Team 449 Climber
 

This is the climber prototype built by Team 449, the Blair Robot Project. We weren't sure how legal it was to use Velcro, so we build what I've been calling macro-Velcro: spinning "hooks" (actually just bolts) that grab a loop. There's also a slipknot that allows the rope to wrap around the winch reel a couple times before it starts bearing a load. We complete the climb in about 6 seconds. Questions/suggestions are welcome!

Video

CAD:

Re: Team 449 Climber
 

Looks sick. What gear reduction are you using?

Re: Team 449 Climber
 

You have plans for something to trigger the touchpad before you run into the channel? You'd probably hit the touchpad first tilted sideways like that, but you might not if you went up especially balanced.

Re: Team 449 Climber
 

Far from impossible. Just add some 2" sticks extending straight up (or whatever direction you're climbing).

Re: Team 449 Climber
 

50:1 on a VersaPlanetary attached to a Mini CIM.

Re: Team 449 Climber
 

Not yet. Ollien's suggestion of sticks could work, as could a pneumatically-actuated bar of some sort. Thanks for telling us this!

Re: Team 449 Climber
 

Nothing's impossible or even very difficult at this stage. It gets tough when you show up at your first competition with a climber at the very top of your robot volume, though. I think there's a lot of people forgetting that the challenge isn't climbing, it's pressing the touchpad for >1s.

Re: Team 449 Climber
 

How much weight was that in the video? Looks like a cool design! (At least, it's not velcro anyway :) )

Re: Team 449 Climber
 

It probably weighed about 40 pounds, although we designed it to lift 150. It's the frame (made of 80/20) from our 2010 robot, with a battery and electronics board attached.

Re: Team 449 Climber
 

Very impressive. What power was the motor running at?

Re: Team 449 Climber
 

Full power.

Re: Team 449 Climber
 

I'd be very interested to know how it performs at about 150lbs (maximum robot weight is 154lbs)

Re: Team 449 Climber
 

The gearing was selected very conservatively to ensure that we're on the rising side of the power output curve.

The current gearbox is 50:1. Mini-CIM output torque is listed at 1.4 N*m. Our winch drum is 1.25'' diameter, so .625'' radius.

Neglecting friction, we have:

(150 lbs * .625'')/(1.4 N*m * 50) = ~15% of stall torque.

Now, I have really no idea how big the frictional losses actually are in this system, but I don't think there's any way they'll take us from 15% motor loading to over 50% (which is peak power, i.e. the loading for which this gearing provides optimal climb rate).

Fully-loaded climb rate (using the frictionless numbers) is somewhere around 6'' per second.

Upon reflection, we could probably gear it a bit faster (we had done the math for the gearbox when we were considering a larger-diameter winch).

Re: Team 449 Climber
 

Your gearbox will fail you after a regional's worth of matches, maybe sooner. The aluminum ring gear will flex enough to allow the planet gears to ratchet, and you will lose the climb.

Re: Team 449 Climber
 

Are you sure? The 50:1/mini-CIM combo is labeled as acceptable by VexPro's documentation, and as noted above we're not actually anywhere near the peak loading on it.

Re: Team 449 Climber
 

Catapult failure in first 2014 regional, canburglar failure in second 2015 regional. Similar physical setups.

Re: Team 449 Climber
 

Any gearbox suggestions, then?

Re: Team 449 Climber
 

Maybe custom if you have resources. Vexpro CIM gearboxes would work, but bulky because you'd need two reductions.

Re: Team 449 Climber
 

We don't have much in the way of machining resources at all (miter saw, drill press, and a little hobby lathe), and the drive gearboxes would be an absolute nightmare in terms of space/weight.

I think I'd rather try to add a 2:1 reduction or similar via. chain to reduce torque on the gearbox if this proves to be problematic.

Re: Team 449 Climber
 

Are you sure you were using the VersaPlanetaries correctly? I've used them a number of times without problems and I've pretty much only heard good things about them. Were you properly greasing them? Did you check the max loading guide before choosing a reduction? Did you assemble them in highest to lowest reduction order? Did you support the end of the shaft?

Re: Team 449 Climber
 

Bold words are mine for emphasis.

This is completely false. This is not how the ring gear works in a planetary system. The only load that goes in the direction to cause the gear to flex is the separation forces of the planets, which is quite low even when the gearbox is overloaded. Please do not make claims that look like statements of fact when you have no idea what is actually going on.

Now, I am sorry that you had failures, but I can tell you that a steady climb is NOTHING like catapult and can burglar loading scenarios as those have extremely high shock loads. I an willing to bet that you either had planet carrier failure or a failure of the spline. I would like to hear about the details of your setup and I can pinpoint exactly what failed and why.

We did excessive failure testing on the VersaPlanetary and failed it in ways you can't even imagine. That is how we developed the load rating table and that is why the 10:1 has lower load rating due to the nature of the failures.

Again, I would love to help pinpoint what happened on your can burglar and catapult, but my team used VPs for both applications with exactly 0 failures.

Paul

Re: Team 449 Climber
 

Nice design. Just a quick question/comment: Is the geartrain's resistance enough to prevent the robot from releasing the rope if the battery runs out of juice? I would consider the event in which your system reaches the top of the rope and needs to maintain its height until the end of the match.

Re: Team 449 Climber
 

Please explain.

This application is within the load ratings of the VP gearbox for this application. I have a hard time believing that they'll have a problem considering how many VP gearboxes my team has run at the edge of what they're rated for (and sometimes past). Suffice it to say the VPs have taken every ounce of use and abuse we could throw at them and still work great.

Re: Team 449 Climber
 

Can't wait for district competition event and hopefully will be on the same alliance this year. Good Luck 449 and Wil see you soon on the field soon

Re: Team 449 Climber
 

We have a ratcheting wrench on the hex shaft that the winch drum is attached to.

Re: Team 449 Climber
 

Also, what gear boxes are suggested for the climber reduction??

Re: Team 449 Climber
 

There's been a rather extensive discussion of this already in this thread!

We're currently using a versaplanetary with a 50:1 reduction, though we may reduce it to 40:1 or 30:1 pending further testing with a full-weight robot. I would not advise just blindly copying this without understanding the motivation for this choice, however - if you go back to the first page, I posted the math behind it.

Re: Team 449 Climber
 

We have used VP for years and only ever had 3 fail. But the 2 that had gears fail were back in 2014. I cant remember the ratio, but we had the two gears that goes in the center separate, because they were only pressed together. (We also did not do much looking into the loading charts or anything like that back then) In 2015 we had a pin fall out of one of the gear ratios inside the gearbox. The pin then jammed up the gearbox and burnt up the motor mid match. I would put all my money on the VP gearboxes. IMO they are the greatest cots gearbox available. (Excludes drivetrain)

Re: Team 449 Climber
 

I can say from experience that VPs don't deal well with an axial load pulling on the shaft. They seem fine with a moderate axial load pushing on the shaft. I've failed them two ways pulling on the shaft. In 2014, we had a ridiculous arm intake mechanism lifting a bunch of mecanums on a long lever arm. It was actuated by a leadscrew attached to a VP. The weight on the arm was failing the shaft retaining ring by deforming the groove. My only option for fixing that was making a bearing block for the leadscrew with a flange nut transmitting the tension to the bearings. Thus sparing the VP.

Second was in 2015, leadscrews moving our stacking mechanism up and down. Except programming decided to up limits switches right next to hard stops, so when we lowered the lift, it hit hardstops, pulling the leadscrews up and over several cycles pulling the 8mm CIM shaft out of the VPs. I had thought it was solid, but no, it's pressed in. Solved that one by machining down a 1/2 hex shaft to 8mm, and fixing the program to PID to position like it was supposed to.

TLDR; don't pull on the VP shafts. They're not really designed to put up with that.

Re: Team 449 Climber
 

Wait - there is a knot in the at the bottom end of the rope? Or, Are you planning to bring your own rope and its legal to have a knot at the bottom to grab onto?

Re: Team 449 Climber
 

Re: Team 449 Climber
 

Thanks for posting your design.

If there is any concern about Versaplanetarys taking the load, you could go with half the gear reduction and a 1:2 chain sprocket ratio.

Re: Team 449 Climber
 

Yeah, I considered that earlier in the thread. We're really not that worried about it, though, given the loading and VexPro's documentation.

Re: Team 449 Climber
 

So does the rope just wrap around around the rod? I was just wondering because we have a similar design and I wanted to know if you had anything special to keep the rope in place and wrapping around while keeping the robot relatively stable. THANKS

Re: Team 449 Climber
 

One more question. What material did you use use for the rod? Did you buy it from AndyMark or McMaster-Carr? Thanks

Re: Team 449 Climber
 

The rod material is from https://www.competitionrobotparts.com/

Re: Team 449 Climber
 

Without a ratchet how does it not come back down?

Re: Team 449 Climber
 

There's a half-inch ratcheting wrench on the hex shaft.