How do teams winch quickly?

I am curious how teams that use a hook at the end of some kind of rope are winching quickly (Team 33 comes to mind

Here is our current climb:

We have a Falcon 500 on a 100:1 CIM Sport spooling up a strap. The tape was put on the shaft to help spool up the slack more quickly at our last event.

You will notice in the video that after we spool up the slack, we have to pulse the motor 2-3 times to get off the ground because it slows nearly to a stop.

We orginally used a AM RAW Box at 14.2:1 for winching (we had it laying around) and it was acuatlly able to lift the robot, but it frequently stalled as we lifted. Again, the pulsing was necessary.

Sure, I could do the math on this, but we are using a Falcon 500 on a 100:1- I really don’t think we should be slowing down. It seems like the bottleneck is somewhere else.


Some photos showing the routing of the cable would be very helpful.

Yes, you should. This is a program to encourage students to study STEM topics after all.

It only took an hour to go through the calculations. Most of the time was spent explaining the physics to the students. The time spend doing the calculations is probably less than the time to install a new gearbox.


JVN Design Calculator is an excellent resource for this kind of problem. When you plug in your scenario into JVN design calculator, you find that you are only drawing 6 amps, and take nearly 10 seconds to climb, with a stall load of 6,641lbs!
You can reduce your reduction a significant amount, since you can safely draw 30 amps consistently (more than that at peak). I recommend something around 20:1, which would draw 24amps and allow you to climb in about 2 seconds. By using JVN Design Calculator, you can easily determine this kind of thing before you cut any metal.


We use a mini cim with 20:1 and our spool is half inch hex shaft

we are running a neo on 30:1 and it works amazing we are 120lbs

My team uses a neo on 21:1 reduction on a VP with a ratchet with the rope tied into one of the holes on a TTB 1/2" hex hub(so the spool diameter is 1.875"). We can climb in under a second once we are aligned.

Ideally you want a large diameter spool to remain more consistent, and geared appropriately. If you use a 1/2" shaft, that means it’ll build more drastically, than if you design for a 1.5" spool. If you use a small diameter rope, it also helps prevent build up. Using JVNs calculator is the best way to calculate the amount of force you actually need. To climb faster also, you may just need more motors. It wouldn’t hurt to add a second climb motor from a redundancy standpoint.

i also notice watching you climb this weekend at Northern Lights your cable routing is less than desirable. I believe you use caribeaners as pulleys to redirect your cable path? If that is the case you are adding a lot of inefficiencies to your system which adds stress to your motor which increases your amp pull while climbing.


I think we are using a 40:1 NEO with a 2" diameter spool, which has been more than enough for us. We are using a ratchet and total robot weight is around 145lbs.

Yes, we are doing exactly that. We needed to somehow route the cables to pull upwards from our center of gravity so that we don’t go outside of our 12" extension.

We pull our string straight down onto a 1/2 vex hex shaft. We use 1 NEO in a ~12:1 VP reduction on brake mode to keep us in the air for at least 5 seconds after the match.

We are using a 775 pro on a 7-5-3 reduction. I think on a 1” spool.

Okay. I’ll look into seeing what we can do for using pulleys as pulleys. With the design of our “cannon,” I really don’t see us being able pull down on a central location.

you really just need to have a rolling friction. the problem with the caribeaner is you’re not getting that and you’re losing too much in your system.

There is another team who started a thread about their slow climb despite using lots of motors. If I recall correctly, the conclusion was that there was too much friction where the cable went around corners and they needed to add pulleys to allow the cable to roll around the corners. You need to solve that problem first before doing the calculations because the friction greatly increases the load on the winch and you will have a hard time determining the extra force due to the friction.

Our climbing winch consists of a single CIM with a 12:1 Sport gearbox driving a 6" long piece of 1/2" hex that serves as a drum. An eye bolt causes the 1/8" diameter cord to spiral along the hex shaft so it doesn’t stack up. It is all mounted on the very top of the robot, near the CG to avoid having to route the cord around things.

Our solution to this was to route the line from our winch to the top of our robot with steel eye hooks ( I think 2 of them).

This is a very rough sketch showing our strap routing relative to the frame of the robot. We route it through an eye-bolt and again through a carabiner.

so its not going to just be the carabiner, is also going to be anyplace the rope touches your tower arm…


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