Chief Delphi - We need help... A lot of it

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Re: We need help... A lot of it

Quote:

Originally Posted by GeeTwo (Post 1446070)

A second cable is only needed if your lift plate is too light, or your friction is too heavy, for the lift to lower itself. As I read your posts, your first cable (pull on lift) is also your second cable (pull on lower). If this is correct, you can pretty much ignore the "second cable" posts.

Also, if this is correct (that is, your cable is doubly terminated on the chassis end), you can make your system more repeatable/reliable by adding more wraps to the shaft/axle/spool on the lift side. This basically means making a somewhat longer cable in the shop (add one or two wraps around that spool), including it in your WITHHOLDING ALLOWANCE, then replacing it on the Thursday of your competition.

Quote:

Originally Posted by EricH (Post 1446071)

Yep. Often for winches, that's a bit larger and drum-shaped.

It's more of a "hold-in-place" on the wheel, giving it more cable to work with (having the same effect as a grippier wheel, theoretically). You'd have a tensioner (turnbuckles work well) elsewhere in the system and run a pretty tight cable for this trick to work, but it should be. Given that you've got a small(ish) wheel width-wise, you might be able to get away with 2 wraps.

I'm going to suggest following the procedure I posted earlier, with the cable not permanently terminated until you get the lift working reliably. It might take extra cable wraps or some grippy material or both, but it should give you some working room.

Thanks guys its such an easy fix Im mad we didnt get to do it today. The good thing is our mecanum wheels are working and I had a little bit of driving practice getting a good feel for this years control layout. We should be able to make all the fixes necessary in an hour or 2 on practice day of the comp. Thanks all ;)

Re: We need help... A lot of it

Quote:

Originally Posted by Sperkowsky (Post 1446075)

Enjoy your competitions.

My favorite thread of the season.

Re: We need help... A lot of it

Quote:

Originally Posted by Sperkowsky (Post 1446075)

Always glad to help. I hope we ally with you on Einstein ;->.

Quote:

Originally Posted by GeeTwo (Post 1446133)

Always glad to help. I hope we ally with you on Einstein ;->.

Miracles are real... I think

Re: We need help... A lot of it

You might find the capstan equation interesting: http://en.wikipedia.org/wiki/Capstan_equation

Basically having a few wraps around the moving part of your winch increases the maximum pulling force exponentially.

You might see a few photos of 5742's robot with a 6" diameter steel pulley on the front of it. There are three wraps of 1/8" plastic coated wire rope around there, and it does not slip. http://www.chiefdelphi.com/media/photos/41356?

With two wraps it slipped a bit.

With one wrap is just spun uselessly.

You'll note that there is an eyebolt at the top of the 5742 lift to adjust tension in the cable. That also helps improve traction.

As far as linear slides are concerned, IGUS (the cool plastic bearing people) have some information on designing them at http://www.igus.ca/wpck/6109/TechTalk_Overview Check out the "2:1 rule" and "How to Eliminate Binding"

Good luck,

Jason

Quote:

Originally Posted by dtengineering (Post 1446146)

Thanks man

Re: We need help... A lot of it

Quote:

Originally Posted by Sperkowsky (Post 1446140)

Miracles are real... I think

Absolutely. Miracles happen all the time. Too many of them go unappreciated.

Quote:

Originally Posted by GeeTwo (Post 1446187)

Absolutely. Miracles happen all the time. Too many of them go unappreciated.

If that happens I will appreciate it haha.