Jack Chapman
Jack Chapman1:13 PM

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Andrew Peterson
Andrew Peterson1:14 PM

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Jack Chapman
Jack Chapman1:14 PM

@Jack Chapman set the channel purpose: Get robot to level3 climb

Chris Rininger
Chris Rininger1:14 PM

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Cruz Strom
Cruz Strom1:14 PM

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Enrique Chee
Enrique Chee1:14 PM

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Ethan Rininger
Ethan Rininger1:14 PM

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Harrison1:14 PM

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John Sachs
John Sachs1:14 PM

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Julian Bonifaci
Julian Bonifaci1:14 PM

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Kenneth Wiersema
Kenneth Wiersema1:14 PM

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Paul Vibrans
Paul Vibrans1:14 PM

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Violet Advani
Violet Advani1:14 PM

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Justice James1:18 PM

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Ryan Olney
Ryan Olney1:18 PM

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Riyadth Al-Kazily
Riyadth Al-Kazily1:46 PM

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Chris Rininger
Chris Rininger7:44 PM

Question for the climbing team: Is the plan to climb from the L1 platform to L3, which is 19 inches? Or is the plan to climb from L1 to L2 (6 inches), then L2 to L3 (13 inches)? I believe the plan was to go straight up to L3, but I'm looking at it in the simulator, and it is a long way up, so double checking.

Andrew Peterson
Andrew Peterson8:38 PM

Looking at the CAD design that Paul made, it looks like the idea is to go all the way from L1 to L3 if we can. The piece that gets pushed down below the robot is a little over 24.5 in.

Paul Vibrans
Paul Vibrans8:46 PM

The robot climbs from L1 to L3 directly. Anything else takes too long.

Chris Rininger
Chris Rininger11:09 PM

Sharing... If there is some vision for how the cargo intake will assist with the climbing process, please let us know so we can factor into our requirements and design. Thanks.

Micah C. Glasby
Micah C. Glasby11:32 PM

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Jack Scheiderman
Jack Scheiderman12:22 PM

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Sunny Gregson
Sunny Gregson1:17 PM

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Jacob Preston
Jacob Preston3:31 PM

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Jacob Preston
Jacob Preston3:32 PM

Here are the 2 1/2 inch solid pvc rods we need https://www.usplastic.com/catalog/item.aspx?itemid=32414&catid=733

Enrique Chee
Enrique Chee4:10 PM

Please check what we have in the R8ZZ bearings in inventory .

Jacob Preston
Jacob Preston4:21 PM

the proper gray pvc rod

Jacob Preston
Jacob Preston4:25 PM

we actually have the correct size bearings in inventory so we don't need those then

Andrew Peterson
Andrew Peterson4:32 PM

We have some of the bearings, but not enough so we will need to order more

Jacob Preston
Jacob Preston4:34 PM

we are going to need 12 more right?

Enrique Chee
Enrique Chee6:17 PM

Who is putting this order together ? Quantity , etc ?

Andrew Peterson
Andrew Peterson6:19 PM

I have already made the order and sent it to Kenneth

Enrique Chee
Enrique Chee7:25 PM

Please send me a copy of the email . @Andrew Peterson

Andrew Peterson
Andrew Peterson9:59 AM

I will not make it to the meeting today until 11, work on figuring out exactly what we need for the programmers to automate the climbing process until I get there

Andrew Peterson
Andrew Peterson10:03 AM

Once you figure out what we need, start figuring out where these things will need to go on the robot

Andrew Peterson
Andrew Peterson10:09 AM

Programmers may come to either of you, Ian and Jacob, so be ready to answer questions about the mechanism

Andrew Peterson
Andrew Peterson10:10 AM

If you finish everything I have given you to do before I get there, ask Cruze if you can help him with working on the robot chassi

Binnur Alkazily
Binnur Alkazily12:46 PM

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Austin Smith
Austin Smith12:47 PM

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Randy Groves
Randy Groves12:52 PM

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Harper Nalley
Harper Nalley1:01 AM

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Lane Johnson
Lane Johnson10:14 AM

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Andrew Peterson
Andrew Peterson9:32 PM

@Violet Advani this is the link to the metal that we need to order, we will need 3 feet of it

Kenneth Wiersema
Kenneth Wiersema10:09 PM

I added it to the online metals cart-however I would like to see if there's anything else that we need to order

Paul Vibrans
Paul Vibrans7:23 AM

We need 12 inches of 1" Schedule 40 aluminum pipe for spacers on the intake arms.

John Sachs
John Sachs9:40 PM

OHHH! We can do this! (only on the practice field of course;-) https://tenor.com/view/low-rider-hydraulics-bounce-cars-garage-gif-5103931

Binnur Alkazily
Binnur Alkazily9:50 PM

@Austin Smith @Ryan Olney ^^^ :wink:

Harper Nalley
Harper Nalley2:04 PM

@Paul Vibrans @Peter Hall and I would like to test the climbing cylinders to see if they work so that we can hopefully order the five additional cylinders by the end of the meeting on wednesday. Do you have any ideas for how to test them? Peter and I were thinking about putting something heavy on one of them and seeing if it could lift it. The problem with this would be building a mount for the heavy thing as well as reinforcement for the cylinder.

Peter Hall
Peter Hall2:04 PM

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Paul Vibrans
Paul Vibrans2:32 PM

They are easy to test in the pull direction. Drill a 1" diameter hole in a wood 2x4 and mount it in a vise with the hole vertical. Stick the nose threads through the hole so the piston rod points down. Thread one of the clevises that Ulysses was making onto the rod. Put a pin through the cross hole in the clevis and tie 130 pounds of weights to it using a suitably strong rope. Add 60 psi air and time the lift.

Enrique Chee
Enrique Chee3:45 PM

I went ahead and orderd the additional 5 cylinders for climbing.

Harper Nalley
Harper Nalley4:26 PM

@Enrique Chee okay, thank you!

Harper Nalley
Harper Nalley4:28 PM

@Paul Vibrans so, do that with all four cylinders at once I assume, correct?

Paul Vibrans
Paul Vibrans4:33 PM

Just test one with a single air tank charged to 120 psi feeding a 60 psi reducing station and one air tank on the 60 psi side. Be prepared to reduce the test weight in 5 pound increments to 100 pounds.

Riyadth Al-Kazily
Riyadth Al-Kazily5:05 PM

I would suggest adding a flow restrictor to the exhaust port of the solenoid so that the weight will be let down slowly, or maybe just put some foam padding underneath to minimize the shock on the cylinder and mounting block when you re-extend the cylinder after timing the retraction.

Harper Nalley
Harper Nalley12:23 AM

@Paul Vibrans @Peter Hall another idea I had was using elastics to simulate the weight.
Also, doesn’t the telescoping of the climbing mechanism effectively double the weight of the robot from the perspective of the cylinders?

Paul Vibrans
Paul Vibrans10:41 AM

Our climbing is a constant force process. Elastics are linear springs where force increases with distance. The only accurate test is lifting a fixed weight.
The telescoping does double the force required from the cylinders but the test weight of 130 pounds compensates for this.
A maximum weight robot that has a perfectly centered center of gravity only has 39 pounds of reaction force from each jack. That corresponds to 78 pounds of cylinder force. Add a factor of 25% for 1/4 G vertical acceleration and you get a cylinder force of 98 pounds required with a lift time of 0.64 seconds. Friction will slow this.

Declan Freeman-Gleason
Declan Freeman-Gleason4:09 PM

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Andrew Peterson
Andrew Peterson8:46 PM

@Violet Advani What you will need to figure out at the meeting is how we are going to mount the system to the chassis. By this I mean something like the L brackets at the bottom. As for the upper support across the front set of the climbing mechanism, I do not think we can get them to go across without interfering with the shoot mechanism. I would still check this with Paul just in case I am missing something on this. Other things that needs to be done is to finish the rectangular brackets, filing down the brackets that are already made, start figuring out cable lengths and start cutting the cable to these lengths, sanding down two of the wooden legs that still need to be sanded, and start figuring out how we can attach the drawer slides to the wooden legs. If you have any CAD questions go to Jack on the CAD team, if he is unable to answer your question go to Kenneth. I am sorry that I will not be able to make it to the meeting tomorrow.

Violet Advani
Violet Advani8:48 PM


Darwin Clark
Darwin Clark8:50 PM

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Andrew Peterson
Andrew Peterson9:59 PM

@Violet Advani After checking over my work I realized that the upper support across the front set of the climbing mechanism will, in fact, work, with 2 inches of room between the top of the shoot and the top edge of the climbing tube.. I will give you a drawing for the 2x2 in hollow tubes as soon as I finish up with them in CAD

Jack Scheiderman
Jack Scheiderman7:51 PM

@Andrew Peterson Will you be at the meeting tomorrow?

Chris Mentzer
Chris Mentzer5:18 PM

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Chris Rininger
Chris Rininger7:36 PM

Check out post 14 to see a cousin to our bot: https://www.chiefdelphi.com/t/post-video-of-your-first-hab3-climb-attempt/343744

Mark Tarlton
Mark Tarlton2:29 PM

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Paul Vibrans
Paul Vibrans10:06 PM

Nine tower legs are finished except for deburring.

Justice James
Justice James10:10 PM

Is that four per robot and an extra?

Cruz Strom
Cruz Strom5:53 AM

Yes, Thanks Paul

Chris Rininger
Chris Rininger12:29 PM

Mark Tarlton
Mark Tarlton2:28 PM

Something more like this might work as well. The advantage is that there's no play once it's latched. The real challenge is to add a latch and not require reworking of the arms and joints to integrate it.

Mark Tarlton
Mark Tarlton2:30 PM

something like this arranged in parallel with the pneumatics is an option. The idea is you have a telescoping assembly that doesn't latch until it reaches full extension and when it does latch, has strength enough to support the weight of the robot.

Mark Tarlton
Mark Tarlton2:34 PM

... and of course there's a youtube video https://www.youtube.com/watch?v=y3V6o3eca0g

Mark Tarlton
Mark Tarlton7:57 PM

@Paul Vibrans Is it possible to rotate the front legs 90 degrees to move the cables away from the center of the chassis? The hoops are running into the cables and pulleys.

Andrew Peterson
Andrew Peterson8:01 PM

To answer your question Mark, no we can not. The idea of the cables is to link to two rows together so that when we go to climb the front and back will at least be parallel to the platform.

Paul Vibrans
Paul Vibrans8:01 PM

The locking button is more like what will work

Mark Tarlton
Mark Tarlton8:04 PM

I think the front cables are going away. There's an interference problem with the chute. My understanding is that the rear legs will be responsible for keeping the robot level.

Paul Vibrans
Paul Vibrans8:04 PM

Which cables and pulleys are in the way?

Mark Tarlton
Mark Tarlton8:05 PM

the upper pulleys and the cables running down to the bottom of the legs.
It looks like the hoops will be pressing against them

Paul Vibrans
Paul Vibrans8:06 PM

Do you mean the pulleys attached to the piston rods?

Mark Tarlton
Mark Tarlton8:06 PM


Paul Vibrans
Paul Vibrans8:07 PM

The answer is absolutely not.

Mark Tarlton
Mark Tarlton8:08 PM

Ok. what happens if the front legs are rotated?

Mark Tarlton
Mark Tarlton8:11 PM

Since the crossing cables for the front legs are going away, it looked like the leg assemblies could be rotated one way or another to make more room.

Paul Vibrans
Paul Vibrans8:12 PM

The wheels at the bottom of the stalks can't rotate 90 degrees because of the direction of travel. The stalks and guides are designed around the orientation of the wheels and the towers would need to be changed. The towers are made.

Mark Tarlton
Mark Tarlton8:14 PM

do you really need wheels on the front? I thought the front legs would retract as soon as the arm goes down

Mark Tarlton
Mark Tarlton8:15 PM

If we don't change the legs, is there going to be a problem with the hoops rubbing against the upper pulley and the cables?

Chris Rininger
Chris Rininger8:18 PM

OK, well, here are nearly 1cm locking tube pins: https://www.amazon.com/Paddle-Button-Spring-Locking-single/dp/B00N01CLW6/ref=sr13?ie=UTF8&qid=1549339973&sr=8-3&keywords=locking+tube And here's a source I found for telescoping metal tube: https://alcobrametals.com/products/telescoping-tube Are you guys thinking the tube goes along side the cylinders or the cylinders go inside the telescoping tube?

Paul Vibrans
Paul Vibrans8:20 PM

I don't know without seeing the extent of the interference. The piston rod and its pulley are relatively stiff so I would expect both the pulley and the hoop to damage each other. The cylinder foundation could become distorted as well.

Mark Tarlton
Mark Tarlton8:20 PM

my thought was the tube is parallel to the pneumatics (on the inside) so that the pivot points for the pneumatics and the tube are identical.

Mark Tarlton
Mark Tarlton8:21 PM

Ok. I'll try to skinny up the hoops, but they will flex more as a result.

Paul Vibrans
Paul Vibrans8:25 PM

Can you trim the hoops and add steel flat bar with a much greater modulus of elasticity to make up for the removed material?

Mark Tarlton
Mark Tarlton8:27 PM

possibly. Especially since I have to cut and glue the hoops at that point, i might be able to insert a stiffener at that point. I'll keep working on it.

Paul Vibrans
Paul Vibrans8:33 PM

Can you send me a .stp file of the hoop and a datum for locating it in the robot? The datum I use is the mid point of the line of contact of the center wheels with the floor. The towers are symmetric about longitudinal and transverse lines through my datum.

Chris Rininger
Chris Rininger8:34 PM

Not seeing it. Seems like there are timing belts & pulleys in the way on the inside and probably not enough room on the outside for parallel mounting like that. I think it would need to be mounted below the pneumatics to the outside of the drivetrain wheels. Or we could make the intake a bit narrower to give us room on the outside of it.

Chris Rininger
Chris Rininger8:39 PM

Mark Tarlton
Mark Tarlton8:40 PM

it would be just inside the stacked pulley. there's a clear shot from there back to where the pneumatics mount. not in the center of the arm but the space between the pneumatics and the legs

Chris Rininger
Chris Rininger8:42 PM

so a tongue of metal linkage connects there and extends back to the telescoping tube with the button lock that will lock when the arm is in the full down position?

Mark Tarlton
Mark Tarlton8:50 PM

Ok. just got it integrated into kenneth's robot and it is the BACK cables causing problem. I can work around that, I think. I'll send you models anyway. I'd like to slim down the hoops but I don't know how much I can slim it down.

Chris Rininger
Chris Rininger9:04 PM

I understand the suggestion now, I think. It seems a bit much- the telescoping tube moving back and forth every time the arm moves back and forth, but if it's our best idea then should we order a few different button locking tubes (e.g. https://www.amazon.com/Stansport-254-Telescoping-Tent-Pole/dp/B004Z10D16/ref=sr18?ie=UTF8&qid=1549342688&sr=8-8&keywords=telescoping+pole+button+lock) and start experimenting? Climbing won't work without a lock-down mechanism, correct? We're sure the pneumatics will not be strong enough?

Mark Tarlton
Mark Tarlton9:06 PM

or you could have the nesting square tube the entire length for strength and stability.

here's a different direction that you might be able to do on top of what's there now

(I meant to send this earlier but forgot to copy the link)

Mark Tarlton
Mark Tarlton9:17 PM

you need something stiff enough that it won't buckle under load. the simple button at the hinge might have worked but I didn't see room for it

Mark Tarlton
Mark Tarlton9:19 PM

Another idea is to put a notch in the arm right at the pivot point, so that a latch would press straight up into the notch when the arm is fully down.

Chris Rininger
Chris Rininger9:44 PM

That's more what I had in mind, except higher up.

Chris Rininger
Chris Rininger10:09 PM

Something like this tied into the arm pivot mount

Chris Rininger
Chris Rininger10:10 PM

that latches onto the arm here

Kenneth Wiersema
Kenneth Wiersema10:15 PM

The clip was what I was thinking for it, but just a piece of flat bar with a spring or elastics attached to pop it into position and then have a hook to connect into a cylinder that comes out of the arm around where you've indicated. However I think we're going to need something pretty strong to support the weight of the robot

Mark Tarlton
Mark Tarlton10:33 PM

that's the problem with putting the latch at the pivot point. You've got a long lever arm putting a lot of force on the latch right there. If you put something there, it needs to be tight fitting and really strong. any slop in the latch and the robot will sag if the air goes out

Mark Tarlton
Mark Tarlton10:37 PM

for the sliding bars, you would need to check how much travel it has and also double check the forces on it. The force depends on where you mount it and what the leverage is on it.

Chris Rininger
Chris Rininger10:57 PM

I guess I go back to your earlier suggestion.... Strong telescoping square tube like they sell here: https://alcobrametals.com/products/telescoping-tube/telescoping-aluminum-square-tube/6005a-t6-telescoping-square-tube Plus custom installed beefy locking tube pins like these: https://www.amazon.com/Paddle-Button-Spring-Locking-single/dp/B00N01CLW6/ref=sr13?ie=UTF8&qid=1549339973&sr=8-3&keywords=locking+tube Mounted along side the pneumatics. We might have to try a few things to find something that works right - this seems to be a nontrivial problem. @Paul Vibrans when you're back on here... of all the ideas thrown out here, for which ones should we start ordering stuff so we can try them out do you think?

Paul Vibrans
Paul Vibrans11:53 AM

There is no way to delete the back cables.
Replace the part of the hoops at the side joints with steel flat bar having joints above and below the equator. Use steel for stiffness. Attach with countersunk screws so the outside face is flush. Put the longitudinal guide above or below the equator by enough distance so the curvature of the ball provides space. Attaching the longitudinal guide may require countersunk screws and tapped holes for a flush finish inside and out.

Mark Tarlton
Mark Tarlton11:55 AM

Ok.. I'm working on an alternative .. I think if I tilt the hoops so that they're parallel to the legs when the chute is at 30 degrees, then I can place them anywhere. The hoop shape is weird but it should be much easier to work with.

Jack Scheiderman
Jack Scheiderman12:00 PM

@Mark Tarlton Will this be printed today?

Mark Tarlton
Mark Tarlton12:01 PM

I've got other stuff ready to print now on the MarkForged. Let me know when the bed is cleared and ready to print, and I'll launch the job

Nora Wilson
Nora Wilson1:39 PM

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Nora Wilson
Nora Wilson1:41 PM

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Jeffrey Tappen
Jeffrey Tappen5:45 PM

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Harper Nalley
Harper Nalley11:07 PM

I just rewatched Ethan’s Climbing Oof video several times on repeat and I think locking the wheels might help a good bit, but it won’t prevent it 100% of the time. I think we may want to put needle flow regulators in the system for the front pistons since they are extending more quickly.

Harper Nalley
Harper Nalley11:07 PM

Those two things done together should fix the problem.

Mark Tarlton
Mark Tarlton9:02 AM

Paul is looking to add "spurs" to the front stalks to provide leverage against the front legs tipping over. These spurs would attach where the wheels and act like shoes pointing to the rear of the robot. If the robot starts to tip, the extended length of the shoe will move the tipping point further to the rear and should stabilize the robot. That may also provide a similar effect to locking wheels. We discussed adding flow regulators. The conclusion was that since the climb system behavior is inconsistent, it wouldn't be likely that we could tune the regulators to give good results across various possible tank pressures. As a result, the focus has been on possible mechanical solutions to the tipping.

Chris Rininger
Chris Rininger9:49 AM

We bought smooth hard plastic adhesive backed floor glides (1"x1" squares I think) last year that will slide with low friction on the HDPE - they might be good for the spurs if I'm understanding them. I know where they are if interested.

Mark Tarlton
Mark Tarlton10:02 PM

@Paul Vibrans Regarding the width of the "toe" -- since the grippy stuff behaves more like an adhesive than a friction surface, making the toe wider may provide more grip than a regular width toe.

Paul Vibrans
Paul Vibrans9:18 PM

After pondering the performance of a "clown foot" on the back stalks when trying to climb to the lower level of the Hab, I no longer support the clown foot as a climbing solution.
The way to keep the stalks from moving backward is to fit the wheels with one-way clutches, which I have ordered from Zoro Tools. They should be here in about one week. In the mean time, we need to replace the 3/8" aluminum tube axles with 3/8" steel tube axles and fit them with anti-rotation features. The wheels should be, but do not have to be, aluminum with rubber tires made from O-rings or stretched bicycle tube material glued on with Barge Cement. PVC wheels can be used but their grip on the roller clutches, which depends on a press fit, is not too reliable.

Mark Tarlton
Mark Tarlton9:25 PM

Let me see if I understand the reasoning. When the robot starts, the front and rear legs are "x" apart both in the chassis and where they hit the floor. If the robot starts to tip, the legs are still "x" inches apart in the chassis but on the floor they start to move away from each other as a function of the tilt angle. Therefore, if we can prevent the wheels from moving apart on the floor, then the tilt angle will be 0.

Paul Vibrans
Paul Vibrans9:48 PM

Also, the hab wall prevents motion toward the top of the hab until the bumpers clear the top of the hab. At the lower level, the robot will be tipped radically toward the hab once the front stalks retract, which would firmly engage the toes of clown shoes with the floor, preventing any subsequent movement toward the top of the hab's mid level. Wheels with one-way clutches could roll forward still.

Chris Rininger
Chris Rininger2:39 PM

Similar climber to ours: https://youtu.be/50hUj3VJyCQ. They use rack gears with motors - legs go up together.

Binnur Alkazily
Binnur Alkazily3:23 PM

I like that solution — watching our robot during bag day testing highlights the challenges of high level of dependence on air tanks for cycle time execution

Chris Rininger
Chris Rininger8:34 AM

@Paul Vibrans Since it would fit in the same or smaller footprint and we should be able to reuse much of what we have (just a different way to actuate) could we possibly trade our pneumatics on the climber for a rack gear solution like this? Advantages: 1) Motor control reliability, 2) L2 climb should be as easy as L3 because we can use motor control for that as well, 3) weight savings (possibly major). The climb is near the end of the video. Since motors don’t count in holdback, we should have holdback weight to spend on it.

Paul Vibrans
Paul Vibrans8:47 AM

Start working on the detailed design. I will be happy to review your calculations and drawings before manufacture. You will learn a lot. Please try to keep it within the envelope of the existing climber.

Chris Rininger
Chris Rininger9:08 AM

I might just take you up on that, because the solution advantages over our current one would help the team. You're saying you will collaborate if I take lead? I'll start by reaching out to that team to find out where they got their gears.

Paul Vibrans
Paul Vibrans9:19 AM

I don't have time to collaborate, just time to review.

Chris Rininger
Chris Rininger11:17 AM

Then I'll pass - it's your system & collaboration would be required to upgrade to motor controlled actuation. I believe you know this. Please consider the advantages in my earlier post & let me know if you change your mind. Thanks.

Chris Rininger
Chris Rininger3:11 PM

Here's an "endless" 3D printable rack gear set. Could probably design one like this that is herringbone. https://www.thingiverse.com/thing:3444515 Clearly, these don't integrate with our solution as is, but worth considering for a future need. There's a different one I saw designed to integrate with drawer slide rails.

Paul Vibrans
Paul Vibrans6:58 PM

What is to save if the climber is to change to electric motor driven rack and pinion? Besides, it would be faster to remove the existing stuff in whole assemblies and replace them with whole assemblies that are pre-tested. As I consider potential details of a rack and pinion climber it begins to take on many of the undesirable fabrication features that made me abandon motor driven screw jacks. I could make one robot set in about 40 hours. How long would it take the students? Rack and pinion jacks also would not be as fast as what we have now, based on timing videos of our climber and motor driven climbers on You Tube. I would not put more than one 775 Pro on each leg because you start to chase battery voltage drop caused by adding motors such that the available climb power doesn't rise and the climb doesn't speed up.

Chris Rininger
Chris Rininger7:57 PM

The 3339 climb took 8.5 seconds, with the end of the climb demarcated by the instant the back legs begin to rise (climb successful once contact with lower floor is broken). Our climb in the video on our marketing channel took 8.9 seconds by the same standard. The raising and lowering of legs IS definitely faster with our pneumatic approach; it is the other steps in the cycle that took us longer. I do think we could cut that time by up to a couple seconds with automation, so let's say we can get to a 7-second climb (which I think we will think is great). The questions are concerning reliability and the opportunity of the level 2 climb. 1. Reliability: The speed of the pneumatics seems to create a risk of tipping with potential major consequences because one set of legs gets ahead of the other unpredictably. Will the proposed fix truly solve this? We are all hoping so. 2. L2 Climb Opportunity: This may be the more significant one. If our L3 climb isn't the fastest and most reliable, and alliance captains also have very fast, reliable L3 climbs, then the coach has pointed out it will be a disadvantage to not be able to climb to L2. With rack & pinion + motor control, it's mechanically free - just some programming work (I think). With our current solution, I'm not sure how we do it without tipping risk again.

I agree with what you say about just switching out full assemblies rather than retrofitting, BTW. Before, I was thinking the 2x2 and even rails/legs might be adaptable, but your point about testing on a separate robot and just switching out makes sense.

Kenneth Wiersema
Kenneth Wiersema10:22 PM

I’ll believe the numbers, but I think the primary issue would end up being weight. The 775 pro is 0.8 pounds and the pneumatic cylinder ended up at 3 pounds I think, so if we’d just look at replacing the pneumatics rather than the entire system as what seems to be implied, we have a hard time getting a rack and pinion that light.

Chris Rininger
Chris Rininger10:22 PM

Starting a new thread, exploring a rack-and-pinion + motor/encoder climbing solution like the one FRC team 3339 did in the shared video (see conversation above). I used one of the common engineering spreadsheets (named AMB Design Spreadsheet) created by a mech engineering prof in Israel as I understand. The spreadsheet indicates that given...
- 10v left on the battery
- 154 lb robot
- 22 inches (19" climb + 3")
- single 775pro per leg
- 0.5" pinion gear
- a 20:1 gear ratio (each leg motor)
- total efficiency across gear reductions: 70%
a climbing leg under load should rise in around 0.7 seconds

Here's a screen shot. This and the similar JVN calculator are designed for use by students, and I would be happy to help any students learn to use them. It is extremely common for students to execute this aspect of analysis on FRC teams, using these tools. (Ask around at competitions if you doubt it :slightlysmilingface:.)

Paul Vibrans
Paul Vibrans8:23 AM

The 0.5" diameter pinion driving on the rack implies small teeth. Check rack tooth strength and final drive pinion tooth strength before settling on a gear ratio.

Chris Rininger
Chris Rininger8:38 AM

Thanks, I was wondering about that.

Chris Rininger
Chris Rininger12:15 PM

For future, a bit more information: I heard back from team 3339 that they use an 18-tooth 20DP VexPro gear + a compatible plastic 20DP rack gear. https://www.vexrobotics.com/3-8-hex-bore.html (the 18T)

Chris Rininger
Chris Rininger12:26 PM

From their email, they used a rack gear like the dr12.5/10/.5 on this page: https://www.beltingonline.com/1-25-mod-x-0-5-metre-plastic-acetal-cut-teeth-rack-6937

Enrique Chee
Enrique Chee1:51 PM

Climbing with robots #2 and modifications.

Paul Vibrans
Paul Vibrans3:01 PM

It did climb? More than once?

Riyadth Al-Kazily
Riyadth Al-Kazily3:05 PM

It fell over. More than once.
Every attempt (2 or 3 tries) resulted in the robot falling over backwards (away from the step).
No climbs were successful.

John Sachs
John Sachs3:43 PM

Wondering if the back legs are slower to extend due to being cabled together; more friction in that system?

Paul Vibrans
Paul Vibrans3:48 PM

Probably. Loosening the cables might help.

John Sachs
John Sachs3:49 PM

What if we sequenced the intake arm to go down first to act as a brace against falling backwards?

Paul Vibrans
Paul Vibrans4:27 PM

I just watched the climb video a bunch of times and there are many things that could be the source of our troubles. It is clear that the stalks nearest the wall are first to go and the back ones go later. With no manifold, the pressure drop in the air supply to the back stalks may be greater so they start later and develop less force than the front ones. Reverting to a manifold would help with this. The tubing runs to the back jacks could be longer than those to the front ones, adding to more pressure drop. The cross wiring on Robot 2 is much tighter than on Robot 1 and has more drag; it should be loosened slightly at the dead ends and this looseness distributed throughout the system if possible. The stalks should drop freely when the robot is on its cart and the safety pins are removed.

Robot 2 has a different weight from Robot 1 and the center of gravity could be much farther aft. If Robot 2 can be tested with ballast on the end that goes up first, it would help our understanding of the problem.

The intake arm can't be put down first because wall is in the way.

Paul Vibrans
Paul Vibrans4:38 PM

Can a delay be built into the programming so that the front stalks go down reliably later than the back stalks so that if friction were equal front to back, the robot would always tip toward the wall?

Justice James
Justice James4:46 PM

Yes, we did this when first testing the climbing system.

Paul Vibrans
Paul Vibrans4:50 PM

Today or some time ago? When I saw the robot attempt to climb in the past, it was tipping toward the wall and the timing was adjusted to make it tip away from the wall. The wheels were modified to work with the robot tipping toward the wall and having a center of gravity on the wall side of the middle axles.

Justice James
Justice James4:59 PM

The first time the programmers had the robot, so some time ago. It was working relatively (? half the time, about) well without any timer. When it was tipping, it tipped away from the wall. We played around with the timer, but it didn't help much at the time.

Declan Freeman-Gleason
Declan Freeman-Gleason5:01 PM

@Paul Vibrans Justice is correct that we had a timer, but he missed the nuance that the back wheels now lock. We tried a timer at CK once today (I put it into the code), but we’re testing driving now to take advantage of the field. We will test more back home (maybe Monday?)

Paul Vibrans
Paul Vibrans5:07 PM

I will be prepared for Monday.

Justice James
Justice James5:12 PM

It might be worth looking at Skunkwork's climber. It didn't actually work, but it also doesn't have front posts...

Whatever they had on their back posts had good traction.


Jack Chapman
Jack Chapman9:22 PM

Could we use needle valves like on the intake arms?
@Peter Hall

Chris Rininger
Chris Rininger10:02 PM

One anecdote from another team: Rock could not get a pneumatic climbing solution to work because of a similar problem to ours of legs rising at different speeds unpredictably, and they spent much of this weekend switching to a motor-driven solution involving chain inside 80-20 extrusion. They demo'd it, and it was still not Rock solid (:)), but it seems like they'll be able to get it dialed in.

Of the things I've seen us try, the clown feet seemed to have promise given how they seemed to stabilize the robot against tipping while the climbing legs caught up to each other. Not sure why the roller clutched wheel didn't help more.

Cruz Strom
Cruz Strom7:23 AM

We tested the system at CK with a delay and it fell the other way. If we fine tune the delay on the first robot, we will be good. The clutched wheels worked perfectly but the weight of the second robot is different than the first robot. I think we should test the first robot with clown shoe and clutched wheel without the delay, and then try adding the delay if needed.

Paul Vibrans
Paul Vibrans9:44 AM

Lets get Robot 2 to work and truly understand the climbing problems before doing anything to Robot 1.

I watched the video again and saw that the roller clutches are oriented properly. We can add clown shoes and fix the center of gravity enough for testing. Loosening the cross cables should be the last thing we try.

Paul Vibrans
Paul Vibrans9:45 AM

I will bring clown shoes for both robots.

Chris Rininger
Chris Rininger1:43 PM

Something Mark has mentioned a couple times that we could fairly readily test is different, higher traction center wheels on the intake for pulling more forcefully during climbing. The idea of the omnis was that they would continue to allow the ball to center while being intaked, and I still like it, but it might work just as well with grippier wheels. Mark suggested the compliant wheels, and I think andymark traction wheels (maybe one click softer than our drive wheels - blue ones?). We could also make some slightly larger-than-4" diameter wheels out of plywood or something, and fasten the super grippy diamond-shaped tread. The slightly larger diameter would help prevent breaking the mecanums as much, and it would put the robot's weight on the grippier wheels.

Another thing: I feel once the intake wheels are spinning there isn't much pull, and with the intake motors at 100% they start spinning almost right away. What if we fast pulsed the motors instead, go to 0% (or even brake mode deliberate stop) for a moment to restablish static friction, then 100%, then 0%/brake, etc.? It seems to me, this may be more effective than just full speed spinning.

Paul Vibrans
Paul Vibrans2:04 PM

@Paul Vibrans has left the channel

Max Morse
Max Morse12:20 AM

@Max Morse has joined the channel