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@Kenneth Wiersema set the channel purpose: To climb
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The quintessential climb with others video from RI3D Team Cockamamie - dubbed by some as "the iron cross". https://www.youtube.com/watch?v=R8w5FLrORpo&feature=youtu.be
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just to be clear, there is another rope spool on the other side
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I believe, from experimenting last year, we already have this hand winch that could potentially be adapted (or parts of it). https://www.amazon.com/Reese-Towpower-74337-Pound-Capacity/dp/B000WZ4KBS/ref=pdsbs602?encoding=UTF8&pdrdi=B000WZ4KBS&pdrdr=JD63K6K96GA072KV1XM3&pdrdw=57hzn&pdrdwg=9gCHa&psc=1&refRID=JD63K6K96GA072KV1XM3
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Possible guides for running the climber rope up the lift - people seem to like them: Yongcun Self Adhesive Twist Lock Cable Management Wave Locks Adhesive Kurly Lock on ... https://www.amazon.com/dp/B01J6RDIQU/ref=cmswrsmscapiyWBxAb9A7G7CY
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@Jack Chapman @Andrew Peterson @Ethan Rininger The masses involved in climbing assist (500 lbs across three robots) are spooky to me safety-wise when it comes to prototyping and testing. Idea: What if we build a rough 1:4 scale model of that part of the field & robots and prototype initially with that?
Bonus Question: Who can tell me the weight of a 1:4 scale model of a 120 lb. robot? Hint: It's not 120 divided by 4.
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Something to consider regarding climbing: With the scissor lift, the upper part of the robot could be a square shape allowing you to add hanging bars on each side. Once the robot has lifted itself, two other robot may be able to climb our robot using the replicated bars on each side. Since most robots will have climbing capabilities, don't try to lift them, give them the ability to lift themselves.
@bill great idea! Not sure about weight capacity of the lift, but worth considering
Re: weight of scale models, in case we decide to pursue: www.alphalanding.com/rc-track/true-scale-weight-of-a-110-rc-car/
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Here's a relevant post started by an FRC coach who was way off on his climbing winch calculations. The community helped him out, including pointing him to the linear mechanism tab of the JVN calculator we were looking at today... https://www.chiefdelphi.com/forums/showthread.php?t=161181&highlight=jvn
Here's a set of recently shared engineering resources, including JVN + several others... https://www.chiefdelphi.com/forums/showthread.php?t=160323&highlight=jvn
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Insight into versaplanetary gearbox stages: https://www.chiefdelphi.com/forums/showthread.php?threadid=161563
In prep for Friday, I threw some questions and possible actions into our working requirements spreadsheet. Next step is to decide which few things to tackle next.
As we started to do last meeting, I used that JVN calculator + the Versaplanetary load ratings guide to come up with this proposed motor and gear ratio. The high ratio might surprise some, but with the fast-spinning 775pro it seems to work, AND we can just use the Versaplanetary gearbox without needing a separate additional gear reduction. Guidance I read stated the gears should be packed into the Versaplanetary as follows: the 10:1 goes closest to the motor, then 7:1, and finally the 3:1 as the third stage furthest from the motor and closest to the output shaft. I'm interested in other proposals - please play with the JVN calculator and see what you can come up with. Thanks!
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I added a new tab to our requirements spreadsheet that includes key specs of the robot and field pieces + a conversion in case we decide to do a 1:4 model. The more I think about it, it really would not be that hard to create a rough scale model prototype for initial testing of "climb with friends" designs. Better than testing with ~500lbs :slightlysmilingface:. Here's a link to the requirements spreadsheet Andrew originally created after our first meeting: https://docs.google.com/spreadsheets/d/16UsQbuSxHZaBjMxUQS0OeBaFg87fXKBlKat4cA1Hs/edit?usp=sharing
Some parts of this are pretty useful
Thinking about hanging in a stable position using single point cables made me think of climber's "porta-ledge." Picture attached
@Paul Vibrans I have searched the interwebs and not been able to find any video of a roller clutch in action that behaves the way you describe. I found some unidirectional transmissions that looked interesting and maybe similar, but not the mythical roller clutch (our name for it on the climber team) allowing different transmission speeds by reversing direction of the input shaft from the motor. All of what I just said is a long-winded way to say... We're going to need your help. :slightlysmilingface: Andrew is going to work on a CAD incorporating the roller clutch as described, but I'm certain we'll need help finalizing the design. Thanks for teaching us a few things today!
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One other question about changing the motor direction - isn't that akin to stalling the motor until the motor starts spinning the other way? Anything we need to worry about? Since CIMs are more resilient than 775pros (at least out of the box), it seems like CIMs will be the way to go despite the weight and size disadvantage.
@Andrew Peterson If you have time, in addition to the design with the roller clutch, would you please do a variation that instead incorporates this 2-speed gearbox with ratio A at 25.90:1 and ratio B at 5.45:1? If you have time. CAD files are in the downloads section on AndyMark. Note: Shifting is done via pneumatic solenoid.
Here's the link to the gearbox: http://www.andymark.com/EVO-s/643.htm
@Paul Vibrans @Jack Chapman @Ethan Rininger @Violet Advani @Jack Chapman @Sean Williams @Bill Bandrowski @Kirsten Martel I want to run something by you. If we used the Evo shifter mentioned in the previous post, including those gear ratios, then my calculations indicate a favorable solution with 2 CIMs and a spool diameter of 1.25 inches. The shifter is expensive, but we'd have it for other things in the future, and if we're really serious about climbing with friends then I feel like a beefy solution is called for anyway. Here's my math - what do you think?
If you all agree, I'm inclined to ask the coach to order this thing right away so we get it ASAP and can build a solution with it. I like the idea of the roller clutch, but I just have a concern that the overall solution is complex / more custom than we may have time to design, build, test, iterate if it doesn't work, etc.
FYI. We already have 4 of these :https://www.vexrobotics.com/vexpro/motion/ball-shifter.html
I did look at that one. The 2.27 spread between each low gear and high gear option is not as ideal for our application as the 4.75 spread with the EVO and the selected high/low gear ratios. It would mean around 2 1/2 more seconds to gather the slack... not too bad, especially since we have it NOW. I'm sold - I recommend we use it. @Andrew Peterson My request has changed. Please create a design variant that incorporates the vex ball shifter coach mentions above. If we select the right spool diameter, then we should be able to have a simple system of 2 CIMs, the shifter, the spool, and the pneumatic integration. If we want two spools as some have argued, then I think the solution is 2 CIMs, shifter, sprockets and chain to a separate shaft that both the spools are on, and the two spools (+pneumatics).
@Jack Chapman how do we find out the gear ratios of the ball shifters we have in stock? Also, on the website it says, "Note: A pneumatic shifting cylinder and fitting kit is not included in the Ball Shifter kit. Be sure to add these below in the "Pneumatic Cylinder & Fitting Options" category if needed." So need an inventory check on that if we go this direction - hopefully we have what we need.
@Andrew Peterson one more thing, our spool diameter will need to be somewhere between 0.5 and 1.5 inches depending on the gear ratios our ball shifters are set up with.
The Vex 2 CIM ball shifter is 3.66:1 and 8.33 :1. 2.27 spread. We should have all the pneumatic cylinder and fittings. If you go this route please inform @Peter Hall. The fittings and hose are not the standard size.
Thanks. @Andrew Peterson given gear ratios, I think a 0.5 winch spool diameter should work. Current is a bit higher than ideal, but from what I've read spikes somewhat over 40amps during a climb of a few seconds have been very common the past two years. Here are the numbers.
Argh, I just thought about rope pileup from spooling that 11 feet of slack. It seems like there will be in the neighborhood of 50 to 75 wraps (depending on pileup pattern) with a 0.5 spool diameter. and that'll change the effective diameter of the spool from 0.5 to a diameter perhaps 3 times larger by the time the slack spooling is done... just in time for the climb... If the diameter is 1.5 inches by the start of the actual climb, then the numbers don't work - way too much current that would trip the 40-amp breaker. I think it makes sense to order the gear kits we need for the lowest gear option with the Vex ball shifter. Option 1: 64:20. They're not that expensive, so could order a couple of them for 2 robots. That gives us ~3.2:1 additional reduction in the gearbox itself & will allow us to have a larger winch spool like 1.25" without having a big separate gear reduction stage. Even with that, we might need 1.5:1 more reduction in the system somewhere. And here are yet again more numbers. Here is with the additional 1.5:1.
If we want those different gears for the Vex ball shifter, here they are:
The extra 1.5 to 1 does seem to be nessecary, and I don't think a 7 second climb is to bad. Would there still be space inside of the shifting gearbox for the extra gears?
Needs to be researched- I think might need to be done via different diameter sprockets & chain from the gearbox output shaft to the shaft the spool(s) is/are on
@Jack Chapman @Sean Williams https://www.westmarine.com/buy/fse-robline--ocean-3000-dyneema-single-braid-line-gray--9486374?recordNum=3 Order 50 ft
@Paul Vibrans Here are the inputs to the gear ratio calculation: 450lbs for 3 robots, 2 CIMs, 1.5" diameter spool (due to 4mm rope), 30" slack & 20" climb under load. The commonly used JVN calculator tool indicates a gear ratio of 32:1 will result in ~4.5 seconds to gather slack & climb 20 inches, with current draw at a reasonable level. Please double check with your own spreadsheet. Thanks.
If any experienced folks know of a 2-CIM-single-shaft gearbox that supports ratios of 32:1 to 60:1 (or even 80:1). I looked at the Modulox, and it might work, but it seems to be designed for prototyping / hypermodularity, and so for many purposes it'll be larger than desired.
Let me know what you guys want.
I was hoping Paul could check the math / gear ratio. And I was also hoping someone would point out a two-CIM-single-output-shaft solution. Do you know what single speed gearboxes we have and what ratios they're at? We could do a reduction with a large sprocket on the output shaft and small sprocket on the shaft powering the winch, and that would be compatible with the typical drivetrain gearbox ratios.
I don't. @Will Hobbs @Kenneth Wiersema @Rose Bandrowski @Jack Chapman Please check your inventory sheet or feel free to go to robotics room afterschool on Mon. Please respond back to Chris.
I think the only single speed two cim setup we have our the vex gearboxes I showed you today
They are two speed but can be setup as single speed
We can do dual 775pros and bag motors on the versa planetary
Any reason why you went with cims over 775 pro’s? Also, I might be presuming a bit here, but we might be able to create an adapter plate for the duel versa planetary system for cims. Otherwise Andymark has a few different solutions, but I don’t think any really fit the small option. /
We've been leaning toward 2 CIMs due to stall resilience.
Is the climbing group ordering any aluminum angle brackets? just curious Will said you might be and I wanted to check
Ask Kaedric Quartermaster.
@Will Hobbs and @Kenneth Wiersema What is the largest reasonable reduction using sprockets/chain 2:1, 3:1, 5:1? 5:1 is getting to be a large sprocket.
on the bracket order question, I don't think we got there, though @Jack Chapman might know otherwise
I ordered al. angles. 3" x 3" x 0.375" 6061T6 Extruded Structural Aluminum Angle - 72" at Paul's request.
we might be able to use the versaplanetry dual motor adapter with two cims
we spent a lot of time evaluating winch design options today - I do recall at the very end hearing some conversation about the stabilizing arms - current thinking there seems to be we need arms that are somehow released and then fall down via gravity. position on the robot is TBD because we need to understand constraints from the harvester design
its not deigned for it but using the right adapters it might work
If we used two of these (https://www.vexrobotics.com/vexpro/motion/gearboxes/217-4018.html) and one of these(https://www.vexrobotics.com/vexpro/motion/gearboxes/217-3141.html) we might be able to use two cims with one versa planetary gearbox
not sure I trust it - single CIM or 775pro are the largest power sources in the load ratings
Please check inventory. I believe I bought some Versaplanetary CIM adapters. Please finalize order on Mon.
also, the spacing of the two inputs may not be wide enough for two cims - cims are quite a bit wider than 775pros
Just an idea we can look at
I'm pretty sure that's all we have for dual cims
Do we have plenty of versaplanetary gear kits (e.g. enough for four VPs - 2 per robot - at a given gear ratio)? So if we need a ratio similar to 32:1, then we could pick 35:1, which would mean we need four 5:1 and four 7:1). If so, it seems like we could use them and pool their power via chain
We should have plenty
@Rose Bandrowski was planning on using some for the intake but i don't know how many she needed
Based on the inventory we should have 10 1/2in hex output versa planetary gearboxes
we also have 3 5:1 gear kits and 3 7:1 kits
Example forklift mechanism for climbing with 2 partners. See additional photos below from a FIRST book coach has.
@Enrique Chee @Jack Chapman it seems likely direction is to use 2 CIMs + one of the following:
- one VP shared by the CIMs via adapters mentioned earlier in the channel
- one VP for each CIM... could position each motor+VP on either side of the shaft with the winch spool (space allowing, of course) to avoid needing to do chain. Worst case we do have to do chain to combine the power of the two motors - just need to do the diligence to get it right.
Given inventory on hand Will stated, I think it'd be good to order 1 more 5:1 and one more 7:1 VP kit.
And then if Paul states we need higher gear ratio, then we'll have to look at options & use other kits in inventory or possibly order other kits
@Kaedric Holt Please include above order with Rose's request from Vex and give me final list on Mon. to order. @Will Hobbs @Rose Bandrowski
I would be very concerned with a system that has each CIM coupled to a planetary gearbox, and the outputs of the two planetary gearboxes rigidly coupled to a shaft. If one of the motors were to fail (or just not get turned on by software correctly, or accidentally disconnected from power, etc.), I think the other motor and gearbox would shred the idle gearbox to bits.
trouble with the 2-CIM-input gearboxes is the gear ratios aren't high enough for our application
they're designed for drivetrains - ideas definitely welcome - thanks for the input
Any high-reduction gearbox being driven backwards (ie, from the output side) will resist movement. The higher the reduction ratio, the worse it is. A CIM could easily spin an idle CIM coupled at 1:1...
another idea: make our own gearbox maybe (not the gears, but the box enabling COTS gears to be set up for the ratio we need)?
At this point, we've talked about so many design directions for the winch... Today, when it was realized the rope slack had been overestimated, there was relief because numbers indicated a simple single speed winch can be pursued rather than the more complicated options. We just need to lock down the design direction given that decision. I took physics and even statics & dynamics back in the day, but I don't have the intuition or experience of a seasoned engineer or mechanic. There is a fair chance I will miss something critical like the exploding gearbox risk Riyadth mentioned. So any and all input from experienced people is welcome.
@Kaedric Holt @Enrique Chee Given the risk Riyadth pointed out, I'm afraid we should adjust course and order two of these: www.andymark.com/ToughBox-p/am-toughbox.htm with the 14.88:1 gears (not sure steel or aluminum). Scratch the order for the additional Vex VP 5:1 and 7:1 kits. With that approach, we'll need a 2:1 to 3:1 reduction via sprockets/chain. Do we have inventory to accomplish that?
@Andrew Peterson As far as CADing the winch, here are the pieces:
- 2 CIMs (CAD here: http://files.andymark.com/CADFiles/am-0255+2.5inch+CIM+Motor.STEP)
- Toughbox gearbox with 14.88:1 reduction gears (CAD here: http://files.andymark.com/CADFiles/am-0145+Updated+Toughbox+2015.STEP)
- Sprockets and chain that accomplish a 2.5:1 additional reduction - not sure where to point you for CAD
- Custom 1 1/2 inch diameter winch, with grooves as described by Paul today + a way to tie into a 1/2-inch hex shaft system
@Will Hobbs @Kenneth Wiersema @Rose Bandrowski We might need some chain and sprokets. Again, feel free to swing by at 1:45 pm to check inventory or check inventory sheet which may not have been shared with mentors.
I will not be able to come after school because I am making up a calc quiz
@Andrew Peterson Paul will definitely need to help with the winch drum, because we'll need a brake again, we'll need flanges incorporated, etc. So I would just do a rough in of that part of the overall design
I will post a link to the inventory in the engineering Chanel
I think we’re fine on chain right now, not certain on what sprockets we have for what gear ratios. We could probably put together a 2:1 or a 3:1 ratio.
@Jack Chapman: @Ethan Rininger I did not look at how CIMs tie into that gearbox (key, pinion...). Would one of you please take a look to ensure compatibility with our inventory?
Before you get carried away with ordering gears that appear to work out to a total reduction ratio of 37.7:1 please note that my calculations show a requirement for a gear ratio between 81:1 and 82:1 with two CIM's driving.
The spreadsheet is not complete because I have not added the links to the motor performance and the battery drain.
@Paul Vibrans: Direction was we need to order today, so we did our best. All we decided in the end was to order a couple 2-CIM single speed gearboxes for the 2 robots, geared as high as they sell them. And we have an intention to include whatever additional gear reduction we need in the form of sprockets and chain. No sprockets ordered. If you have a superior solution, please share and drive it.
I do want to remind you that we ended up lifting 1 robot with 1 CIM at 21:1 last year. 2 CIMs at 35:1 to lift 3 robots seems roughly proportional. 80+:1 seems very conservative and will not be fast enough IMO. What’s your time projection? 15 seconds? Do we need more motors? Different motors? Are we back to thinking 3-drum traction machine?
If we attempt to lift 2 other robots we may need to go much slower to minimize sudden movements that could cause a slip/fall off of our lift. Does that mean we need a two speed system - single lift and partner lift, or just one slow system?
@Chris Rininger can you summarize what you want me to order or @Will Hobbs thanks
At this point, I need to defer to Paul as the experienced engineer & mechanic. Don’t order anything now.
Correction: still order the rope @Paul Vibrans
@Paul Vibrans: could we possibly use the two CIM + toughbox (http://www.andymark.com/ToughBox-p/am-toughbox.htm) at 5.95:1 + this beefy planetary at 12:1. Could the gearboxes be mated?
The planetary: http://www.andymark.com/CIM-Sport-p/am-cimsport.htm
Output of the toughbox is 1/2 inch shaft with 1/8” key and input to the CIM Sport is 1/2 inch shaft with pinion gear pressed on. Can a pinion gear be pressed onto a shaft like that with the key removed? Beyond that, could mounting holes be added to the output side plate on the toughbox in order to mount the CIM Sport. Or if you have a better way to get to (or close to) your target gear ratio, please share.
Calculations indicate a single CIM motor wiith a CIM Sport 64:1 ratio planetary gear will lift three 100# robots in 4.33 seconds with 2.4 second reel-in time and 33.9A motor current. That is what we should use. When all the robots get to 150#, an unlikely situation, the hoist time goes to 5.5 seconds and the motor current goes to 49.5A, which may trip a circuit breaker.
Thanks @Paul Vibrans ! @Enrique Chee @Jack Chapman @Will Hobbs please order three of these with 64:1 ratio: http://www.andymark.com/CIM-Sport-p/am-cimsport.htm
Why not use a versaplanetery gearbox instead of the AM Sport planetry gearbox ?
Hopefully bigger gear teeth and more strength
@Paul Vibrans: will you be able to help @Andrew Peterson with the winch drum design, including grooves, brake, flanges? Thanks again for all your help
Ran across this - I think the risk of tripping the breaker is quite low: www.team358.org/files/electrical/MX5%20Spec%20Sheet.pdf
I found the same thing. We are safe.
Thinking about the climb with friends forklift wings (I vote we call them "the wings") and also about the fact that robots have to be able to clear the cable-protecting conduit bumps on the field that are 7/8 inch high... Should we target to make the height of the structure of the wings the same to ensure compatibility with robots? From section 3.3 of the rules: "A cable protector extends from the center of each side of the PLATFORM and is 2 ½ in. (~6 cm) wide and ¾ in. (~2 cm) high (Electriduct, Inc. CSX-3, black). The cable protector is attached to the field with hook fastener, increasing the height to approximately ⅞ in. (~2 cm). These cable protectors extend to the GUARDRAILS and the SWITCHES." Has any work been done yet on the actual structure of the wings?
This is where we may need to lean on Paul or Kirsten to help figure out what we need for the structure to be strong/rigid enough. For example, is something like this appropriate, too weak, or overkill? http://www.onlinemetals.com/merchant.cfm?pid=22327&step=4&showunits=inches&id=1634&topcat=60
Or thinking a bit more about it, it seems like a frame of 20x20x3mm might be better? Would be good to figure out frame material and general structure so wings can be CADed.
There needs to be a decision on overall geometry before purchasing materials. If the forks lie flat on the floor, the hinge geometry is particularly tricky and the sound the forks make as they slap the floor may turn heads. I think we need to go back to ramps that lead from the floor to the top of the bumpers. The hinges can be located at the top of the chassis with ramp structure extending into slots in otherwise continuous bumpers. Cored composite ramp surfaces are highly desirable if we can get them. There are honeycomb panels available in the aerospace market if we can afford them.
Regarding forks vs ramp - a few thoughts: When I look at auto maintenance lifts, they consist of two rails (versus a platform), seems simple and effective, minimum material and space requirements, does not impede the view as much, and keeps the robot wheels from rolling off the ramp. Striking the floor can be solved with padding.
I like the drive over rather than on nature of the fork/rails. Seems more forgiving / faster as far lining up and getting in place
Could use bumpers to cushion the drop of the wings a bit
Can you draw the hinge detail you have in mind?
I can talk to Mr Michaels about carbon fiber /fiberglass honeycomb if we want to pursue that idea
Probably best to do a flat panel to avoid having to build a mold.
How thick is it? Half inch would be just right.
It is half inch
@Paul Vibrans Here's what I had in mind. Might not need to be so reinforced.
When it is folded within the frame perimeter where is it?
If it hinges where the arrow points it sweeps through all of the side space we need for mounting electronics and pneumatics.
I didn't know locations of those were decided... I also thought a lot of that was going to go sub-deck. Could modify the concept to provide clearance.
@Chris Rininger @Paul Vibrans would love to go sub-deck for electronics (and have access via bottom belly pan) but I believe scissor lift needs the low sub deck space right down the centerline of the robot, forcing electrical to be vertical mount. By the end of next weekend it would be wonderful to define approx. space envelopes for our major systems just to see how big the pieces of our puzzle really are.
Remember that pneumatics will require a significant number of storage tanks (probably 4 to 6), which take a significant amount of space and cannot go below deck. Also, the volume occupied by the pneumatic tubing to all the actuators will be significant, and it will be routed all over the space. Always reserve some space around the edges of modules for routing of control tubing and cabling.
Latest space saving version - not sure about the slide then hinge, but if it could be done then a lot of space could be made available for other things.
suggest a different external product name than ‘wings’ as wings can break — something that can be PR’d as we may need to convince folks to trust we can carry and not break them
How stable will our robot be if only one robot can sit on our ramp while we climb ? I am sure you guys have discussed this.
My understanding is that this is why we want the stabilizing arms
I will not be able to make it to the meeting today
@Chris Mentzer has joined the channel
(http://www.cargoequipmentcorp.com/Wire-Hook-p/1016.htm) heres a possible hook design
Created these sketches, thinking about the need to roll up both the tower face and sides. I still wonder about glides or felt - with enough surface area, could work.
Thinking about a couple things we will need even just to climb by ourselves:
1) the clips that will hold the rope in place when it is zig-zagged up the lift prior to climbing
2) the wheels we will use on the climbing stabilization arms
To that end, I threw a bunch of items we can look at into an Amazon wish list. Here it is:
@Jack Chapman @Ethan Rininger @Violet Advani @Sean Williams @Andrew Peterson @Bill Bandrowski @Jim Carr If you have a chance, please take a look at the arm sketches and potential items to order above. If anyone has strong opinions about which design directions or which components look best, please comment. Re: the arm, definitely would like to see other design ideas. Re: the rope-holding clips, we may need to order a few and see what works best for our unique application.
@Jim Carr has joined the channel
What about the hook ?
Violet shared one yesterday that might work, and yes I agree it would be good to see some options to evaluate. Go climbing team!
I updated the wish list to include several hooks. Also, as part of our winch spool design, do we need some things like these to connect hex shaft and a flanges to the PVC drum? I could see us needing up to four things like this per robot, depending on design. It is possible the flange itself could be designed to cover this base as well as act as a flange, but that could also take more time (which is passing quickly). With these things, we could probably make our own flange readily.
One last thought on the design. It seems to me the placement of the winch drums (including being strongly anchored to the chassis) and 1/2 inch hex shaft is most critical. There are a variety of places and ways we could install the motors + gearboxes + chain to drive the shaft. I recommend we set a goal of getting the winch drums and shaft fully designed and placed on the robot CAD next meeting. @Jack Chapman @Ethan Rininger
Fun with knots 2018 edition... Excellent article on what knots to use with spectra/dyneema types of high-strength rope: http://allaboutknots.blogspot.com/2006/01/selecting-strong-hitch-for.html
We have these hex hubs .
Here's the current location of the climber, and I think it's a bit further back on the robot than what is desirable, but it conflicts with the flipper motor otherwise (the colorful things on the model). The mounting setup is currently temporary, as I think that it needs to be reinforced more than what is currently done.
Let’s wait till the meeting for the images, as there are drums on both sides of the scissor lift as the assembly stretches across the entire chassis
Possible specta knots
I think the Alloy steel flat hook style B looks promising
it is very heavy and way beyond what we need
Some hook ideas
if the 1/2 inch hex hubs are as strong as the andymark ones, they're definitely a better deal
thanks for looking those up
The PDF show some hook ideas. 1) The top is an idea for bolting on a piece of 3-4 inch of channel for a "hook" - either one large piece or 2 small pieces; 2) The middle idea is the custom hook cut from a piece of plate - it can be designed so the bar below will slide easily into the hook when the scissor lift is lowered; 3) the bottom is the idea using the turnbuckle hook.
I think the custom plate idea may make the most sense if we can mount it directly to the side of the intake arms and the rope clears everything. As noted, we can design it so as the scissor lift is lowered, the bar smoothly slides up the arm and into the hook.
how about this hook ? https://www.amazon.com/gp/product/B01NCKUL5L/ref=oxscacttitle1?smid=A1SO27Z04BGMP1&psc=1
the above hook is 500 pound tested
That is an interesting hook!
I like it. Let's get one as an option. It's almost the same shape as I sketched onto aluminum (other than the spring snap clip close) to potentially cut out.
I looked at Amazon for hours - how'd you find that dang thing? Good find!
Weight wise it’s about a pound, but
I bet that one that we make could be lighter
I have used something like this for climbing. 1KN is 225 pounds. so it is 5000 static pound tested
I think a plate hook would be the way to go
how about we steal the shape & cut a couple of them out
While I like the hook Chee found it seems a little heavy and hard to mount
I liked ghe snap lock to prevent our robot from coming off the bar but may also be an issue grabbing
It looks like the snap bit is easily removable if it becomes a issue, attaching the rope also looks fairly easy
Will, re: plate hook, what's that look like roughly?
This is what I was thinking
On the second hook, it looks like you could drill through it and bolt small angle stock onto it, and bolt the stock onto the grabber arm
Wills hook is Definitely easier to mount to scissor lift, cable attachment on Chee's hooks seems easier
I will order both types that I just showed.
The plate hook should be able to mount directly on the side of the intake arm (each side)
@will I like. @Enrique Chee here's another option as well https://www.amazon.com/Climbing-Scaffolder-Automatic-Protection-Standard/dp/B00ZVYXBNS/ref=pdsbs2002?encoding=UTF8&pdrdi=B00ZVYXBNS&pdrdr=V2W5WZ0NTB585SBNCM56&pdrdw=cH4j5&pdrdwg=4kEQd&psc=1&refRID=V2W5WZ0NTB585SBNCM56
I agree with bill
we can also add a hole in the plate to attach the rope
I think top choice is cut the hook out for easy mount as Bill & Will agreed
probably lighter as well - with two of them (one on either side), how thick does the material need to be?
I think the thickest plate we have and could use for this is 1/4 inch, we'd also probably want both to be able to hold at least 500lbs in case one cable gets ahead of the other
I would say 1/4" to be safe
But we could also do 4 1/8" hooks
Can we use the x-carve to cut for hooks ?
Maybe? It will take a long time to cut them, and Will or I will need to watch it constantly
I think we could but it would probably be faster and easier on the bandsaw
With the 1/4" bit we ordered we could probaly cut a lot faster
one thing about the locking hooks: if climb started tipping sideways it would only tip so far
@Will Hobbs You need to show me the 1/4 bit that we ordered. I don't remember anymore.
with two locking hook spaced fairly widely, the hooks themselves could keep things level & might not need the stabilizing arms
just a thought
I think this is true with the plate hooks as well
This is the bit we ordered
@Will Hobbs Thanks.
Don't we have this bit already ? I thought the freebie I ordered was a 2nd one ? @Will Hobbs
We do not. We have a two flute bit which is not ideal for aluminum cutting
Two hooks will not keep the robot level if we climb with only one other robot. The guide rollers are required.
Yep, we're still planning on them. My point was top+bottom rung shaft contact is superior to just top, stability wise.
The hooks shown on slack will not engage to provide down force with the center of gravity positions of just two robots and the expected side to side spacing. A tighter fit on the rung is required.
I did a torsional stress calculation on a winch with 2.5 inch diameter drums and the shaft needs to be 0.625 inch solid drill rod or 0.75 x 0.095 wall 4130 tube of which the tube weighs less. If the tube is used, the drums can be cantilevered off single bearings, which make the installation easier. The drums do not need to be wider than 1.5 inches between flanges to handle all of the rope for a lift. Wider drums will just waste time to make and add weight. If half inch hex rod is used to drive the drums and all of the load is placed on one drum, even if it has support from bearings on both sides, it will get a permanent twist after lifting three robots with a total weight of over 300 pounds.
Loctite 638 will lock hubs longer than 0.5 inches on a 0.75 inch shaft with sufficient capacity to lift three 150 pound robots with a safety factor of 2. No keys or hex shafts are required.
Thanks @Paul Vibrans. Please share the best way to interface with the .75 shaft you recommended, including chain drive, sprockets, and the thankfully narrower drums (custom hubs and loctite on the latter is what I glean, but what about the others?).
I ask because the 1/2 inch hex shaft & surrounding solution was within the grasp of our climber team (everyone understood the pieces & how they fit together), but a more custom solution using the .75" tube may be a bit beyond us (speaking of my myself at least). I respect & appreciate your analysis conclusing that the 1/2-inch will fail with the "climb with friends load" - reality is we're going to need help to attempt the superior alternative.
@Paul Vibrans Will we need something like this (or that "looks" like this)? Two of something like this, one on either side of each drum, bolted through the PVC and loctited to the .75 tube? https://www.pipefittingsdirect.com/075-inch-slip-on-plate-flange-316-stainless-steel
And for the sprocket/chain interface, maybe something like this? https://www.amazon.com/35B20H-3-Tooth-Sprocket-Roller-Chain/dp/B01FV5R6MI/ref=sr16?s=industrial&ie=UTF8&qid=1517210349&sr=1-6&refinements=pborediameterderived-vebin%3A0.75+inches
Is there a local source for parts or are we going to need to order? If the the latter, then we need to figure out what to order before next meeting and then get the orders placed.
Could we possibly change to carbon steel 1/2 inch hex in order to reduce change to overall design, need to identify/source parts, etc? https://m.grainger.com/mobile/product/GRAINGER-APPROVED-Hex-Stock-4YNF7?breadcrumbCatId=17059
Please read the last several posts starting with Paul's post that the 1/2 hex shaft will fail under the load of 3 robots from 10:23pm last night. After sleeping on this, I believe we are at decision time. I see three options, assuming the carbon steel stab in the dark above will not work:
1a) Stay the course with the 1/2-inch hex and abandon the aspiration to climb with friends
1b) Stay the course with the 1/2-inch hex as a hedge against the risk that finalizing an updated design, sourcing the parts for it, and constucting it will take too long for incorporation into the robot (including appropriate testing) for the first competition.
2) Abandond the 1/2-inch hex design and proceed at maximum speed to complete the new design, source parts, build it, and test it.
@Paul Vibrans If we're doing anything but 1a, I need to insist you officially join the climber team part time (which means there's an opportunity cost because we'll be taking your time away from other teams). We can't afford another miss like the torsional stress failure inevitability, and we need your experience to effectively and efficiently get a new design done. Without you, we'll come up with another design, it is likely to be fatally flawed in some other unanticipated way, iterate, etc.
This is the shaft Paul recommended (or I believe so): www.onlinemetals.com/merchant.cfm?pid=9879&step=4&id=250&topcat=0
@Jack Chapman @Will Hobbs Do either of you know what series (25 or 35) our 1/2-inch hex driven sprockets are?
@Chris Rininger I do not remember off the top of my head but I can check today
@Paul Vibrans does the stress issue also apply to the gearbox outputs, or is it just the winch that we would need to change?
I'd personally believe that we should climb by competition 1, so I'm not the fondest of option 1b
By the looks of it, we won't have climbing with friends done by bag day, and changing the shaft would push us a little further back, so the big question is just abandon climbing with freinds or do we change it all
I'm going to reserch parts for the different shaft tonight and order stuff for the other shaft soon unless we come to a conclusion before I order
As arranged nose to nose with the coupler the gear shafts are OK. Separate sprockets and chains for each gear are better.
Potential gap in our general design: How are we guiding rope onto the winch drum? Need a fairlead of some kind?
@Paul Vibrans your calculations we're taking into effect a steel hex shaft, right?
We do not need a fair lead if we can give a clear path from the hook directly to its drum after it pulls free from the clips on the scissor.
I looked at steel hex and it needs to be bigger than 1/2" if all of the lifting takes place with one drum. No amount of hope or wishing will make it otherwise.
@Jack Chapman pinned a message to this channel.
@Jack Chapman pinned a message to this channel.
For those wanting to cnc the hook. I quickly plugged the hook into Easel (the cnc interface program) and it came out with 7.5 hours to cut 1 hook. While someone could do it under 30 minutes on the vertical band-saw.
Thanks for figuring that one out !!
I like it, and it isn't that much of a modification to the current design.
I am just curious on where we would get the bearings for the drum shaft?, as most of our regular suppliers don't carry bearings that have bore diameters greater than .5.
Would the mounts to the drums need to be custom made?, or what Chris found would work too?, because I don't just see the shaft as a strength issue either, as the Drums might not be strong enough either.
Thanks Paul. To Kenneth's point we need to get to specific bill of materials & then order parts.
thinking of the "climb with friends" side forks/platforms, here's a lightweight manual forklift that may inform our design: http://www.globalindustrial.com/p/material-handling/lift-trucks/manual-lift/lightweight-portable-hand-operated-li-truck-500-pounds-fixed-legs?infoParam.campaignId=WR&msclkid=45115bd936ad19ecc9b501a93b4b683c&utmsource=bing&utmmedium=cpc&utmcampaign=catch%20all&utmterm=4582627026478407&utmcontent=Catch%20All
Correction to my earlier comment about our regular vendors not selling large bearings, I found a .75 inner diameter bearing on vex pro, so sourcing the sprocket might be the only problem. According to Jack we have #35 chain, so a 15 or greater toothed sprocket would be ideal.
Another quick sketch - hinging forks - not sure about viability given everything else on the robot. Should we consider a single ramp off the back instead (i.e. climb with friend rather than friends)? Seems like there might be more space back there.
It is not possible to validate the concept sketches without making a first attempt at a design with details like real bearings and housings, real structural members for which stresses can be computed and the like. Can you do that?
Wouldn't a extra 150 lbs off the back of the robot stress the scissor lift more?
Check the platform geometry to see if the length of our robot plus the length of the ramp leaves room for the friend to drive on.
Can take a shot at a more robust sketch tonight. @Jack Chapman I mentioned the back because I’m concerned about having enough space on the sides (& weight to spend generally) for two robust fold down bearing structures. It could turn out to be not viable, but a single fold down bearing structure off the back could be viable in that case.
The parts that need to be ordered for the climber winch are:
4 each Drawn Cup Needle Roller Bearing, 0.75 ID x 1.00 OD x 0.5 W, J-128 Koyo, $4.61 per unit
4 each Needle Thrust Bearing, 0.75 ID x 1.25 OD x 0.0781 W, NTA-1220 Koyo, $1.94 per unit
8 each Thrust Washer, 0.75 ID x 1.25 OD x 0.031 W, TRA-1220 Koyo, $0.71 per unit
All from John Bearing & Supply, Inc.
3 feet Cold Rolled 4130 Alloy Steel Tube, 0.75 OD x 0.095 Wall, $29.57
From Online Metals
4 each Steel Sprocket 35B15 reborable or 3/4" finished bore, #35 chain x 15 teeth
From any source on the internet.
All of the other parts we need are in stock at BHS
@Jack Chapman @Ethan Rininger Send me the links to buy stuff above.
I just need a link for the sprockets. Bearings and washer have been ordered.
the sprockets are backordered from amazon above. Let me know if you find a vendor that can deliever sooner.
Nevermind found a vendor with them in stock
I thought we needed a 0.75 bore, the one that was purchased had a .5 in bore.
Here’s one that I found that has a 0.75 bore, .375 pitch, downside it has 16 teeth
we can bore it out
Boring out sprockets is normal practice. When mounting with Loctite 638, the keyway is redundant.
added stabilizer arms that roll up the tower to the previous sketch, and now I'm going to remove the succession of sketches from the past day other than this one
Thinking about this more, the cables to the sides likely won’t work due to bumpers
I have a possible fix - will look at it later
rough, but gets point across - use hinges to go wider to accommodate robot width including bumpers
I found this summary of how to approach beam load calculations (including cantilevers) that seems fairly well done, though there are ads to skip past. http://www.brighthubengineering.com/building-construction-design/109683-beam-load-calculations-explained/
Here's some websites I like:
How does this sound for a wrench?https://m.grainger.com/mobile/product/PROTO-1-2-22DJ01
Section properties of various aluminum square and rectangular tube sizes.
My calculation for platform tube sizing. This includes a factor of safety of 3. Also calculated is the deflection of various tube sizes.
@Jack Chapman I bought this wrenches: https://smile.amazon.com/gp/product/B01F511BI8/ref=ohauidetailpageo00s01?ie=UTF8&psc=1
Thanks! Since we need the drive-over height to be 1” or less (1.5” is too high probably), would you recommend the 1x2?
The 1x2 is actually the strongest of the 3 I listed. It would be my choice. In addition, it has the smallest deflection.
@Kirsten Martel Kirsten, thanks again for your calculations on the tube sizing. If we are going to build the fork lift mechanism, we would really need a design of the bracket and hinge. If it could be designed to use common materials readily available that would certainly help (a concern is that due to complexity, the bracket may need to be fabricated by a 3rd party).
@Jack Chapman @Ethan Rininger I was thinking... With other mechanisms being behind schedule, it seems like it may be a while before we get time with the robot. I wonder if we should create a wooden stand-in for the robot to mount the climbing winch onto and use it to test test in the meantime. It would be a chassis sized (~28x33 - we can get the exact measurements) plywood platform blocked up to be the same height as the top of the chassis. And we could also use it to prototype climb with friends components as well. Even once we do get time with the robot, it won't be much because of all the other teams (driving, programming, etc.) that need time, so having the stand-in could help us. If it seems like a decent idea, then a couple of us could build it while the climbing winch pieces are being finished up tomorrow.
Also, any word on the wheels for the stabilizer arms? I recommend we order the following to initially try:
One unit of this: https://www.amazon.com/dp/B06VWBN661/encoding=UTF8?coliid=I3NWTJW7FLFYK1&colid=QRAUIR30SRDH&psc=1
Four units of this, in case the above is not strong enough: https://www.amazon.com/dp/B00PZXI1QW/encoding=UTF8?coliid=I3JE5ABQ5W9W38&colid=QRAUIR30SRDH&psc=0
Also, I still like the idea of trying a glide - so much simpler and less risk of breaking it off when lining up. Let's order this to try: https://www.amazon.com/Shepherd-Hardware-9240-Adhesive-Furniture/dp/B000KKVOX2/ref=pdsim604?encoding=UTF8&pdrdi=B000KKVOX2&pdrdr=MB34J8FBNK6EDRY2JSX4&pdrdw=LWRPn&pdrdwg=6ZSPu&psc=1&refRID=MB34J8FBNK6EDRY2JSX4
@Bill Bandrowski we can probably make a triangular one out of aluminum plate. From the hinge to the chassis side could be tube, then vertical tube to the lower platform. A triangular plate aligned with the vertical tube and the bottom platform/tube edge should work. I’ll sketch something up. Open to additional ideas or design considerations I might be unintentionally ignoring!
If we only get one winch built before bag day it must go on the robot. The second winch gets used for testing either on a chassis or a mockup.
Latest thoughts on climb with friends platforms based on Kirsten's work, Bill's ideas, Paul's input that we should consider simplifying bearing via ropes/posts, etc.
Reading the review area on the first wheels, it seems like they aren't that strong
@Paul Vibrans for the design you said that we would need a steel drill rod. Is this something we would have to order?
@Jack Chapman: to Paul’s point, if we can confidently make parts for the second winch (e.g. the drums & flanges), we should. We are going to want practice/tuning time & we are going to be last in line on the main robot. Not sure about the steel drill rod... I think that may have been the different heavier shaft option we did not choose
Here's a tote lifter that has a reinforced corner that we might consider as we design climb with friends
Yes! That’s a similar idea to what I was trying to convey with words. Just proves how worthwhile a picture is.
Thanks for you help Kirsten - looking forward to working with you today if you are available. Chris - I think you are right, we may need to build a mockup of the robot to test components.
A mock-up will be helpful. Did the winch drums get turned and finished at the last session? Thanks Paul for drawings. See you all soon!
FYI. Sprokets are in. They came in on Fri. 2/2. Someone was asking for them. I gave them to the climbing team.
Chris, thanks for posting the drawing showing the issue.
@Bill Bandrowski: @Ethan Rininger @Kirsten Martel picture of our tight spot for mounting the climb with friends forks. One thought: make the fork very slightly a ramp (to allow us to anchor closer to the chassis edge).
Another thought: use something thinner for just “the Z”... 3/8” steel? It would also allow mounting a bit closer to the chassis edge.
Yes, steel plate might work as it may hinge in between wheel and winch
I'm not giving up on Climb with Friends because of how valuable it would be, but I think the time is right to discuss contingency planning. Let's start a tread here... If we have Climb with Friends & it works, our chances of being a picking team are excellent due to the Face the Boss RP + the point advantage of having 3 climbs each match contributing to victories and thus more RPs. If we do not have Climb with Friends, then we won't get all those extra RPs & we won't win as many matches. At this point it is very difficult to say what our chances are to be in the top 10 to 14 robots who will get to select alliances. Chances are pretty good we won't be a picking team if numerous other teams have figured out Climb with Friends (or just Climb with Friend + levitate), because those teams will be getting the extra RPs.
So we need to plan for the scenario of not being a picking team. From an end game / climbing perspective, what can we offer? It seems clear that we will ideally be able to be a robot that can interface with other robots' Climb with Friends solutions. Let's think about that...
1) If a robot offers a climbing bar the same height as the one on the field, will we be able to use it to climb? Would we need to do anything beyond current plans to enable that?
2) If a robot offers a climbing bar that is significantly lower than the one on the field, what about that?
3) If a robot offers a ramp, can we climb it? How steep a ramp can we climb? If you read about that year with the ramps (Rack-n-Roll in 2007 I think), THIS became a big deal. The team members staffing the pits had that information to share with pit scouters ("Our robot can climb ramps up to 25 degrees without tipping.") We may need to test how steep a ramp our robot can climb so we can be ready for this this year.
I put a poll out there on Chief Delphi asking what teams' plans are for climbing / end game. Here's a link: https://www.chiefdelphi.com/forums/showthread.php?threadid=162307
Results summary after 60 responses:
1.7% are not sure they'll even be able to drive up onto the platform and park
20% will be able to park or use a ramp/platform offered by another robot
13.3% plan to simply be able to climb the rung
21.7% plan to be able to climb the box aluminum alongside a robot that climbs the rung
8.3% plan not to climb but to instead assist both of their alliance partners
25% plan to climb and help one other robot climb via ramp, platform, or faux rung
10% plan to climb and help both alliance partners climb via ramps, platforms, or faux rungs (5% of them are planning platforms/ramps like we've been talking about doing... which is easier for other bots to interface with than faux rungs IMO)
There is going to be some craziness during the end game with all that variety!
Updated to include actuator/release... This is a past design that may work better given space problem - space under the drum could potentially be used or not even needed. The question is still, could something like this be designed that would be strong enough?
Hey, is there a need for me to stay today to get some work done on the drums?
The bore of the drum flange should be 0.752".
No, I believe that Cruz will be working on scissor lift parts on the lathe most of the meeting
@Jack Chapman @Violet Advani Cruz will not be at today’s meeting
Chris - thanks for setting up the survey. It is very interesting and useful. Yes, may be a bit crazy out there at the end of the match.
I will need to leave the meeting today at 6:40
4 Pcs - Lock Extension Table Bed Leg Feet Steel Folding Foldable Support Bracket Screw A https://www.amazon.com/dp/B0725X9HRR/ref=cmswrothapiRUPFAbD08MP1R
@Jack Chapman: here are those items
@Andrew Peterson @Sean Williams FYI, no climb with friend(s). After weighing the robot at 5pm, we don’t have the required weight to add forks/platform. The robot came in around 110 lbs and we needed 14 lbs for one set of liftings arms + stabilizers. That puts us over 120 lbs.
I will not be coming to the optional meeting today
Had a thought of the “making lemonade from lemons” variety. What if we leave the two CIMs on there and try to be one of the fastest single climbers?
Could leave gearboxes as is and change overall gear ratio by changing size of one sprocket on each side. Or switch to versaplanetaries with faster ratio.
@Chris Rininger Agreed why don't we keep the power?? We're not going over our weight limit yet so I say we keep it until we know we need the weigh for other more important things
With going with the faster climb,
Would it be a good idea to incorporate the actuators then?
This will help to lower the climb time by keeping our chassis close to parallel with the ground below.
@Sean Williams what do you think?
I don't think that it is necessary to have the actuators for climbing speed if we are climbing on our own. I'm In some respects, it could be better to not use them if there was a possibility of two bots climbing side by side (even though everyone says it won't happen, it was done in 2007). If added, we could simply not put them down. It also wouldnt be all to difficult to add them on. We could plan on adding them then not put them on, or leave them on as a needed basis. They weigh 2 pounds total.
I think weight is going to be a bigger issue than you’re all making it out to be, so let’s go with only one motor on the robot, and then see where we are later, before just going ahead and seeing were we need to remove later.
Weight is a real serious problem and we surely will not climb with two friends. There is no reason to carry around the extra motor and gearbox that are needed to climb with the second friend. Calculations indicate that one motor and the existing gearbox will lift two maximum weight robots but the motor current is nearly 50 amperes, which raises the possibility of tripping a circuit breaker. Our strategy needs to change to include using the "power up" feature to get the third climb. There is a possibility that a fold-down frame on one side of the robot will come in at under 6 pounds, which is what we save by getting rid of the extra motor, gear and its foundation.
Our motor circuit breakers are 40A, which is the maximum allowed. What weight of 2nd robot (assuming ours is maximum) is the heaviest that we could lift and stay below 40A on the climbing motor?
I thought “with friends” was cut. With so much still to do (programming, controls set up & tuning, driving, getting just climbing alone working), is it realistic to continue pursuing? That’s why I suggested pursuing fast single climb.
All up weight of the second robot for 40A motor current is only 90 pounds, an unrealistic number. It would be better for us to replace the 15 tooth sprocket on the winch shaft with a 24 tooth sprocket that puts the motor current at 44A and stretches the climb time to 9 seconds. The breaker will not trip because of the inverse time characteristic of the trip curve. The Talon can handle 60A for short periods of time.
Fast single climb might work in our first match, but what is the strategy when the alliance has no climb with friends machine and two fast single climbers?
With the gearing we have and one CIM, the time to climb is about 5.4 seconds and the current is about 25A.
For just us.
Sounds pretty good, thanks. There’s quite a bit still to do to enable climbing by ourselves - let’s focus on that and see if there is time for more. If there is not time, then next best option will be to be ready to utilize others’ climb with friends (or simultaneous climb on the side) solutions.
Climbing team, I can’t be there tonight. See you all on Saturday.
Hopefully we will see a climb test today, still need to figure out out how to keep the rope stored during the operation of the lift etc. thanks Chris for getting the splice instructions.
Deleted those splice instructions - Ethan found the ones for the splice Paul had in mine & will share
Order for more rope ?
How much is left? I'd say yes because it looks to me like the rope is going to rub against the wire rope on the one side with the pulleys, which could cause it to wear. It may be a question of how fast will it wear.
We have 4 lengths, 2 of which are about a foot too short, and 2 of which are a few feet too short
And the 2 on the robot
That solves it, yes order more. Jack, do you have the length we need? if not, please get it, and then let's order that length times 4 + a few feet extra. Sound good?
or times 6 or 8 depending on how much back up we want to have
FYI robot climbed
Ethan and I running late - also Ethan has doctor appt at 3:30
Here’s 254’s bot, including climb with friend similar to our team’s concept: https://www.chiefdelphi.com/forums/showthread.php?t=163577&highlight=254
looks like this file has been taken down...
updated the link - thanks Dana
Similar to our concept, but all Nasa'd up! Carbon fiber friend lifter? LIDAR? And even a lovely paint job! Click through to their web page, and you can see high-resolution pictures of the robot. Interesting to see they use omni wheels at the corners for increased maneuverability.
looks like their hook and forklift mechanism are on the same side - how would that work?
I think they climb sideways, hooking over the square bar...
I suspect maybe they climb either side box aluminum
It looks like they can climb pretty much any way they want
The honey badger of robot climbing. It just does what it wants.
That tends to be 254’s style; if they want to do some thing, they do it.
One way to speed up our climb is to add a "pre-climb" function that will run the climb motor long enough to take up the slack in the rope. This could be started automatically when there's about 20 seconds left or by the drive team. Drivers need to keep in mind that one in preclimb, dropping the lift will pool rope in the chassis. If we fail to hook and have to retry, there's a chance this would cause a problem.
If we do that we will need some kind of feedback on the motor or drum (like a potentiometer or encoder.) Just let us know if that needs to be programmed (preferably sooner than later.)
Spooling in should start just as soon as the scissor starts up to grab the rung and pause after a fixed number of winch revolutions. The counter could be a cam and a limit switch. Maybe the flats on the hex output shaft on the gear will serve as the cam.
I can't come to the meeting today, so here is a quick to do list, 1-3 are very important.
1. Get rid of any gap between the drum and the bracket
2. Change to 40:1 versaplanetary gearbox
3. Make more pins
4. Make the drum deeper, maybe even add grooves.
5. Change to 40:1 versaplanetary gearbox
6. Add a ratcheting system-500lbs holding strength
7. Add 2 bars for others to climb on, elevated above the chassis at about the same height as the top of the sissor lift in lowest position, one on each side
The 40:1 gear does not produce enough torque to lift 3 robots.
Smaller diameter drums can make up some for the reduced torque of the 40:1 gear but will slow the climb.
Bars for others to climb should be as high above the floor as the rules allow for autonomous. This may be lower than scissor lowest position. The bars need stays like a sailboat mast; the other robots will pull them sideways.
The bumpers will need to be strengthened because they are going to be the side guides if only one robot grabs on. Or you need to add side guides that engage the vertical support for the rung.
The 40:1 would be for just us, others would climb when were at the top
What about one bar off the back? No need for side guides then.
If the friend climbs off the side, both winches need to be active because the hook on the friend's side must connect directly to a rope that carries tension. Otherwise the top of the scissor could get permanently twisted.
One bar off the back does seem like a more feasible option, especially since weight is a little tight
Also keep in mind that the harvester arms are swinging backwards these days.
to do so we'll need to climb high with a ratchet, correct? And we'll need to add a way to drop the bar back
Can the bar stay within the frame perimeter and still be available to other robots?
no frame perimeter the last 30 seconds
I don't think that a bar inside our frame perimeter would be accessible to most teams
I was asking to see if we really needed to drop the bar back or whether we could get by with a fixed bar. If we are off the ground where other teams could drive under our chassis, then perhaps we could offer a fixed bar that was still accessible.
The problem is how far out a teams hooks are from their lifting mechanism. If the hooks are a bumpers length out, then the fixed bar soulution would work, if the hooks are closer than a bumpers length, then they wouldn't be able to hook on
No work got done on the climber today
@Jack Chapman do you want me at the meeting to work on the climber?
We need to replace the climber motor, with the new versa-planetary. I’d focus on getting a group together for that.
@Violet Advani, if you could still?
I can be there from 4-5:15
But I don't really know how the versa-planetarys work
Hey @Paul Vibrans, we don't have any steel drill rod to make spare pins, and Themis seems to be really good at bending them, so if you could please make 2-3 more as spares?
@Jack Chapman did you check scrap?
No steel drill rod that I could find in scrap
I will see if I have any left
@Paul Vibrans if you bring the piece, I can machine it
@Paul Vibrans wasn't around to see the chain slipping on the climber. As I mentioned yesterday, I think a quick-and-dirty work around might be possible to tension the chain enough to avoid slipping (e.g. a strategically placed long bolt that creates a dip in the chain between the two sprockets), and I think Paul may have experience with how to do that. I recommend we consult him. It would be great to avoid chewing up a sprocket in the middle of GP and then having to scramble to fix it, because there are numerous other things people would like to spend robot time on (e.g. auto)
Why did the chain get loose anyhow? I didn't think we were going to change the gear case, just the gears inside. I didn't check the VEX gearboxes for sustained high side loads on the output shaft but they aren't as strong as what we started with, which I did check. Not all gear sets are created equal. Can we change the ratio of the gear that was removed and put it back where it used to be working successfully?
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