Riddle me this

Started think about lift limitations and I wish we had time to do this on our bot, but alas.

Coming from this thread about a lift they’re working on:

I posted that it was possible to lift three 150lb robots with a 250lb lift.
How is that possible?

Keep in mind, I mean 250lbs AFTER gearing/ using pullies/ etc. the whole nine yards. You’ve tested it and all you have is 250 lbs.

Remove the cube handling stuff from one robot so it only weighs 100 lbs total, get the 150 lb robot to put three cubes in the exchange and load those in the levitate column in the vault. Then use the 100 lb robot to lift the 150 lb robot and itself, and push the levitate button.

I can envision some mechanism that gives some serious mechanical advantage, almost like a corkscrew. But is that allowed in the scope of your question?

Ha, clever MrForbes. Let me reword a little.

One robot physically lifts all three robots.
Each robot weighs 150lbs during the match.

Ninja, the scope will allow it. I hadn’t thought of any kind of corkscrew before, but I’m interested in other peoples ideas here.

The system I have in mind does obviously give a mechanical advantage, and it would not be particularly hard to pull off. We may even try working on it for our small build allowance after bag day.

I’ll post later today what we have in mind unless someone hits it first.

How about this? More like a corkscrew handle, I should have said.

You supplement your lifting force with energy from compressed air, elastic deformation, or change in altitude.

You lift the robots one at a time.

Your robot has 2 platforms on it, each of which can hold another robot while your robot is hanging from the rung. You lift yourself first, placing a static hook on the rung which can hold 500+ pounds. Then, one of the platforms acts as an elevator that your alliance partners can drive upon and then be lifted up to the scoring position. The other platform is static, so a robot has to get to it by driving onto the elevator platform, getting lifted, then driving from the elevator platform to the static platform. The second robot just stays on the elevator platform. Oh, and the mechanical power for the elevator platform is directly connected to the lift which you used to lift your own robot.

This is incredibly convoluted, but satisfies your requirements that:
1.) There is only one source of mechanical power on the robot for lifting, and it can only lift 250 lb at a time
2.) All 3 robots are lifted by your robot

Give me a lever and a place to stand and i’ll move the earth. Mechanical advantage doesn’t just come from gears and pulleys!

Also, if you want to be tricky… build some springs/gas shocks into your lifting mechanism. Those can (if properly sized) provide 200 lbs for lifting. If your motor can provide 250 lbs in either direction, it’ll be strong enough to overcome the springs to extend up to the bar, and can then assist the springs to lift all three robots with a combined 450 lbs of force. Basically what Sean said, but with more detail :slight_smile:

John and Jon both hit pretty close to what I was thinking.

Ok, try this on for size.
https://imgur.com/a/qpi1p (hope the link works)

Tables unfold. Red outside cables are static and never need to change length.
Front side lifts with just one bot and locks
As it lifts the tables self-level
One OR two bots drive on
Backside lifts ~250 lbs

Yes, there can be some swing with one bot, but the static cables actually prevent tipping.

The spreader bar serves two purposes. Keep cables from tangling on bots. And providing a fixed point to add the pullies/eyebolts/team flag/etc. Now you just need a means of raising the bar.

I would imagine that the bots could slide off so maybe using a rough surface you could increase the friction because it looks like the bot may fall off but that is a genius of a design though. It also seems very simple.

This is what I thought of before finishing the question.