pic: Team 188 Teaser 2
 

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Its A Winch!

Re: pic: Team 188 Teaser 2
 

Re: pic: Team 188 Teaser 2
 

It's the van door motors shaft (the longer one). We lifted 128 pounds (4 cement brick) running a winch on the shaft with that motor. And we did it w/out supporting the shaft. You won't sheer that. A better nut perhap, nylon locking.

Re: pic: Team 188 Teaser 2
 

A little info on shear ratings


Shear Capacity Calculation

To roughly calculate the ultimate single shear capacity of a bolt, multiply bolt area at full shank diameter times ultimate shear strength rating, e.g. 8-32 18-8 stainless steel bolt, 0.164" diameter. (A standard 8-32)

Area = πr2; 3.1416 x 0.082" x 0.082" = 0.0211 square inches

Single shear = 90,000 psi x 0.021 = 1890 lbs. at full diameter

This calculation is for shearing a 8-32 on the thread. I am pretty confident it will hold your robot.

Re: pic: Team 188 Teaser 2
 

Consider that bolt not flush against the load.. such as a tiny "negligible" bending moment of only .25 inches....

Stress = M * y / I

Stress = M * y / I

130 lbs * .125 * .082 in / (3.141 * .164^4/64) = 75,500 PSI

Compound that with some shear stress... you're in a danger zone. Consider and extra load of an extra robot hanging with you... eek! In my opinion.. using a #8 bolt is definitely pushing a reasonable factor of safety.

However, the van door motor, being 11mm or so, should work out to be just fine.. but I'd definitely try to avoiding doing anything cantilevered... that freaks me out. Keep in mind that those bearing are bought from the cheapest bidder...

Nevertheless, good luck!

Matt

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I doubt that there is a .25 inch gap. I assume this because most team dont manufacture parts like that to within 250 thousandths. I believe if there was "a tiny "negligible" bending moment" it would only be that of 1-2 thousandths. Especially considering that the nut on the end would hold it all flush.

Re: pic: Team 188 Teaser 2
 

That's a cool winch drum but it looks liek it would be really heavy.

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Too heavy. It's at the shop being turned down. We thought 3/4 inch was a little too sturdy.

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Nice pulley or winch. The device has a good chance of working, depending on the stress put on the wire.

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Such high praise!
Careful, or you might end up actually making a compliment.


188 - Looks awesome guys. I can't wait to see the finished version.

JVN

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I'll give you a bit more.

Yes it's a pulley/winch system. Yes it will hold. No it's actually not that heavy, but we want it lighter anyway. Yes, it backdrives, but not for long. You will be more impressed when you see some other stuff, I promise. That is, if our robot sheds some pounds.