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-   -   Plaction and Omni wheels (http://www.chiefdelphi.com/forums/showthread.php?t=83258)

Edoc'sil 21-02-2010 08:50
Plaction and Omni wheels
 
Ok, so we got our bot up and running last night. Our robot had been unable to turn, but we have omnis in the four corners of a six wheel drive. Watching this thing spin in high gear was pretty crazy. Unfortunately while we were stress testing , one of the treads came off our plaction wheel. We assumed Andymark used a epoxy of sorts to adhere the tread to the wheel, but in reality the tread is only held on by three weak staples. How are we supposed to reattach it? Andymark suggests rivets, but I wonder if that is legal due to rules about metal and the floor. Could we use regular epoxy to adhere the tread?

My other question is why did this happen. Is this a common occurrence? I assume it is because the omni's radius is about .125 smaller making them in effect travel slower at the same RPM. Could this have been that cause of the problem? Do we need to gear the omni wheels so that they are going closer to the same speed? And more importantly, why aren't 8 in wheels 8 in?

Chris is me 21-02-2010 08:57
Re: Plaction and Omni wheels
 
Quote:
Originally Posted by Edoc'sil (Post 925171)
Ok, so we got our bot up and running last night. Our robot had been unable to turn, but we have omnis in the four corners of a six wheel drive. Watching this thing spin in high gear was pretty crazy. Unfortunately while we were stress testing , one of the treads came off our plaction wheel. We assumed Andymark used a epoxy of sorts to adhere the tread to the wheel, but in reality the tread is only held on by three weak staples. How are we supposed to reattach it? Andymark suggests rivets, but I wonder if that is legal due to rules about metal and the floor. Could we use regular epoxy to adhere the tread?

My other question is why did this happen. Is this a common occurrence? I assume it is because the omni's radius is about .125 smaller making them in effect travel slower at the same RPM. Could this have been that cause of the problem? Do we need to gear the omni wheels so that they are going closer to the same speed? And more importantly, why aren't 8 in wheels 8 in?
The product page for the wheel says that the tread is only held on by the pressure of the wheels clamped together, this lets you swap out tread easily. For rough and wedgetop, installing rivets prevents any slipping and dragging issues. Once you drill the hole and rivet the ends, the rivet sits under the rest of the tread enough that it doesn't really contact the ground. Teams have riveted tread onto wheels for years with no issues, so you should be good. I don't know how strong your epoxy is or how well it would adhere to tread / wheels.

The tread probably failed due to the stress of wheels pulling in opposite directions. Slightly slower omnis probably had little to do with it, I wouldn't fret too much over gearing for 1/4".

IndySam 21-02-2010 09:01
Re: Plaction and Omni wheels
 
Using rivets to attach tread is a tried-and-true method of attachments in FIRST.

Put a couple on the ends and you will be OK. You could used a little epoxy on the ends but that makes replacing treads harder.

Teched3 21-02-2010 09:02
Re: Plaction and Omni wheels
 
In the past, we have used a combination of "Shoe Goop" and safety wire to hold our tread material to our wheel surface. As long as you place the safety wire in the low spots of the tread, it will not contact the carpet, and should be legal. We do this in eight equally spaced locations around the perimeter, paying special attention to where the ends of the belting meet. Drill small holes through the rim and twist the safety wire together within the wheel rim.:)

Edoc'sil 21-02-2010 09:16
Re: Plaction and Omni wheels
 
Thank you for the speedy response. We will do the quick and easy glue and wire to ship with and bring riveted wheels to our competition.

IndySam 21-02-2010 09:41
Re: Plaction and Omni wheels
 
Quote:
Originally Posted by Edoc'sil (Post 925189)
Thank you for the speedy response. We will do the quick and easy glue and wire to ship with and bring riveted wheels to our competition.
With the withholding allowance you don't have to ship them at all.

Edoc'sil 21-02-2010 09:46
Re: Plaction and Omni wheels
 
*ship and practice

KC1AJT 21-02-2010 12:20
Re: Plaction and Omni wheels
 
Quote:
Originally Posted by Edoc'sil (Post 925171)
Ok, so we got our bot up and running last night. Our robot had been unable to turn, but we have omnis in the four corners of a six wheel drive. Watching this thing spin in high gear was pretty crazy. Unfortunately while we were stress testing , one of the treads came off our plaction wheel. We assumed Andymark used a epoxy of sorts to adhere the tread to the wheel, but in reality the tread is only held on by three weak staples. How are we supposed to reattach it? Andymark suggests rivets, but I wonder if that is legal due to rules about metal and the floor. Could we use regular epoxy to adhere the tread?

My other question is why did this happen. Is this a common occurrence? I assume it is because the omni's radius is about .125 smaller making them in effect travel slower at the same RPM. Could this have been that cause of the problem? Do we need to gear the omni wheels so that they are going closer to the same speed? And more importantly, why aren't 8 in wheels 8 in?
here's a picture of our bot:

it is a six wheel drive with the omnis in front and 4 plactons in the back on a pivoting drivetrain we have had no issues with the tread (just normal wear) i would recommend putting your plactons at the back so that you dont create that twisting shear between the carpet and wheel


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