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-   -   pic: Whoops! Too much torque (http://www.chiefdelphi.com/forums/showthread.php?t=87522)

basicxman 15-11-2010 08:35

pic: Whoops! Too much torque
 

Nick Lawrence 15-11-2010 08:36

Re: pic: Whoops! Too much torque
 
How did this happen? Too much cowbell?

-Nick

JesseK 15-11-2010 09:31

Re: pic: Whoops! Too much torque
 
I think by cowbell, we mean what was the motor setup + gear ratio into this wheel? Also, how did the wheel stall?

Chris is me 15-11-2010 09:36

Re: pic: Whoops! Too much torque
 
The outer rims of the wheel seem like a really odd way for this wheel to shear. Wouldn't the bolt holes loosen, the sprocket bend, etc. before the outer part of the wheel broke? How does that relieve the stress?

Brandon Holley 15-11-2010 10:51

Re: pic: Whoops! Too much torque
 
Pretty interesting failure. Definitely not typical from what I've seen out of the kit wheels in the past.

Still looks like it was due to the robot being pushed sideways in some manner.

-Brando

Racer26 15-11-2010 13:37

Re: pic: Whoops! Too much torque
 
Sure looks like a side-loading failure to me. A rotational-loading failure would more likely manifest itself in shattering spokes, or breaking the holes in the hub.

Josh Fox 15-11-2010 13:44

Re: pic: Whoops! Too much torque
 
Team RUSH had a couple wheels go like that during the past season, those bumps were pretty rough, but we did add reinforcements to them by cutting pieces of what I believe was 1/16" aluminum and placing them between each set of spokes.

I don't fully understand what you mean by side-loading, so I'm not sure if that's the same as this, but I think the general belief is that our failures were due to the forces of impact on the wheels when they hit the ground.

Alan Anderson 15-11-2010 13:47

Re: pic: Whoops! Too much torque
 
The distorted shape of the wheel doesn't look like what I'd expect from either a rotational or side load. It looks like a simple impact to me. The robot might have taken a hard bounce, or it might have run the wheel into a proverbial brick wall at high speed.

Then again, the wheels were redesigned to handle greater side loads without breaking the spokes, and this might just be how they react now.

Ether 15-11-2010 13:48

Re: pic: Whoops! Too much torque
 
Quote:

Originally Posted by Josh Fox (Post 980889)
I don't fully understand what you mean by side-loading

A force parallel to the wheel's axis I presume.




Josh Fox 15-11-2010 13:54

Re: pic: Whoops! Too much torque
 
That's what I assumed, I was just thinking that an impact force would be more likely to have this effect on the wheel, since it reflects what we saw happen in our own wheels this year.

Ether 15-11-2010 13:59

Re: pic: Whoops! Too much torque
 
Quote:

Originally Posted by Josh Fox (Post 980893)
That's what I assumed, I was just thinking that an impact force would be more likely to have this effect on the wheel

"load" can include impact loads.

You get hit hard in the side, the impact creates a momentary side load (especially if the bottom of the wheel is against the bump or the goal ramp)




TroyCDH 15-11-2010 14:06

Re: pic: Whoops! Too much torque
 
Neat picture. As others say, my guess is not torque but a thump coming down of a ramp etc.

I will add for fun--possible plastic "creep". If that robot has been strapped in real tight to a shipping crate for what? 7 months now...that could cause some high stress points that now show up after standard use.

Troy

Chris is me 15-11-2010 14:49

Re: pic: Whoops! Too much torque
 
The odd thing about this is that 2200 had an omnidrectional robot that could not cross the bump. Perhaps their preseason prototype has enough power to break wheels by pushing?

BEEKMAN 15-11-2010 15:03

Re: pic: Whoops! Too much torque
 
Quote:

Originally Posted by Ether (Post 980891)
A force parallel to the wheel's axis I presume.



Correct:

Axle-Wheel-Load
_
| |
| |
---| | /___\
---| | \ /
| |
|_|

Woot ASCII Art


EDIT: It messes up my spacing.......

Chris is me 15-11-2010 15:08

Re: pic: Whoops! Too much torque
 
Code:

Correct:

Axle        Wheel    Load
                  _
                | |
                | |
-----------------| |    /_________\
-----------------| |    \        /
                | |
                |_|

Fixed art above.


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