Re: Lifting mecanisms
 

Kevin,

Our team would like to purchase a set of these spherical chickens. We think that they will be the key to success this year.

While we're at it, we'd also like to purchase any infinite planes of uniform density and frictionless vacuums you may have for sale.

Thanks,
Jared

Re: Lifting mecanisms
 

We've only been able to find planar chickens for sale this year, so we're figuring that the 1.5 second number will end up being around 8 seconds

Re: Lifting mecanisms
 

It's going to be harder than most think to elevate a robot above the platform. As it's lifted the robot is going to swing toward the tower assemble and a bumper will most likely snag on the underside of the platform.

Re: Lifting mecanisms
 

Every time I ask a serious question, I get 6 people telling me to read the manual, search the pdf, browse the FIRST site...

I have looked, read, searched, and found NOTHING on spherical chickens. Are they available from AndyMark? They were not on the kick-off inventory list.

Thanks

;)

Re: Lifting mecanisms
 

My students would beg to differ with you on that.

Also, yes, a 1 second lift is unlikely. Mostly because gearing to max power means you stall your motor if you double the load. But c'mon. Aiming for a paltry 12.5% stall torque on a CIM still gets you from 0-20 in under 2.5 seconds. 5 seconds just to lift yourself with a CIM means you're doing something wrong. Using a different motor will obviously be slower, of course. But still, it's just 20".

Re: Lifting mecanisms
 

I have been running some numbers on lifting with a single CIM motor.

Seems perfectly reasonable for a robot to be able to lift itself in ~4 seconds. Now you just need to figure out how high is high enough to hang (keeping in mind you need to get down without powering on the bot, and also staying in place when power shuts down).

Remember to consider the current being drawn by the CIM while your lifting. Gear down too much and you will lift too slowly, but not enough gearing and you will blow your breaker. We are limited to 40 Amps continuous load per motor.

Hope this is helpful,
Rob

Re: Lifting mecanisms
 

This was brought to our attention with the idea of a winch, and frankly, I'd agree that this could be a huge problem.
We're now considering something other than a winch that we saw in 2007 by many robots.

Re: Lifting mecanisms
 

As long as you don't center the robot in front of the tunnel (keep your bumpers up against one of the poles) this shouldn't be a problem.

Re: Lifting mecanisms
 

During the finale, robots can come out into and around the bumper zone, and with an unlimited number of servos, the top tier teams will easily be able design a mechanism to prevent bumper snagging.

Talking with my physics, he has assured me that using a CIM to lift the robot would definitely suffice, and it'd be fast too.

And for those who are considering a worm gear, a worm gear will rip itself apart before it goes against the motor, but they are extremely slow. And I mean EXTREMELY slow. IMO, it'd take at least 10-15 seconds to get up beyond the 20".

Good Luck,
- ttl

Re: Lifting mecanisms
 

Any thoughts on gear ratios? We're looking at using a CIM with a planetary gearbox from Banebots and a spool winch, but the only ones we've ever used are 12:1 reduction -- probably inadequate for the job...

64:1? 128:1?

Advice would be appreciated.

Patrick

Re: Lifting mecanisms
 

Patrick,

There are many things to consider when selecting your gear ratio.

Specifically, what method are you going to use to lift yourself? I presume a spool and cable system of some sort. So you need to consider the radius of that spool. Changing the radius of the spool will affect the linear speed of your cable system, as well as the required input torque to lift the robot.

If you were to share a bit more information and specs on your proposed system, I am sure someone could give you more clear advice on what gear ratios to run.

Also consider how the mechanism will back drive after power has been cut off.



That aside, something I have not heard much about yet, is if anyone plans for their lifting mechanism to be able to work with multiple robots hanging off their bot.

Rob

Re: Lifting mecanisms
 

Also, Banebots cautions that the higher gear ratios on their planetaries are for speed reduction only. A CIM is capable of tearing the gearbox apart if the shaft is too heavily loaded. What that load is, they don't say.

Re: Lifting mecanisms
 

I personally wouldn't use a CIM on a BB planetary to hold high loads, as I've heard lots of stories about gearbox failure. Perhaps Andymark's GEM500s are worth a look?

Re: Lifting mecanisms
 

While checking the Harbor Freight web side for cheep winches to play with (hint hint) in the search was a couple come-along. The thought of powering one of these with a pneumatic cylinder briefly crossed my mind. I might have to try that just for kicks.

Re: Lifting mecanisms
 

Team 2508 is planing on a robot that can pickup two other robots using a forklift like device to pick them up, but we are still sketchy on how we are going to lift all of the weight off of the ground.