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srider4004

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Reply with quote  #1 
Does anyone know how you are supposed to go about using the long open ended pulley belt that comes in the kit? we are trying to figure it out but not sure how if its not closed.
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gyoung

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Reply with quote  #2 
There is a good hint in the Generic_Kit_Usage_Guide_v2.pdf.

Find it at http://www.bestinc.org, under Participants > File Manager

Then navigate to:
MAIN / Public Resources & Training / Kits
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jmg

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Reply with quote  #3 
We use them when we want to have a motion that will not perform a complete rotation like an arm that just rotates 180 degrees. You will usually want to use a tensioner to make sure it is good and tight.
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EvansPhysics

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Reply with quote  #4 
Back in our first year, our team spliced the ends together to make a full loop.  They used a section of adhesive velcro (soft side only) on the back and then stitched the belt tight to it with a little of the copper wire (stripped to bare copper).  There was a little hitch when the splice was engaged with the gear teeth, but it worked.  It was in an application where it didn't require a lot of tension.  I can't speak to the the durability of this (I was worried about it) as it was only used on a mall day prototype and was abandoned as the design changed.

Unfortunately, I don't have a close up pic, but you can definitely tell this is not the standard size loop and you can just see the velcro section of the splice.

Spliced Belt.jpg    

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rookies2017

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Reply with quote  #5 
I came to the forum with this same question. [smile] This is our first year, and I feel very overwhelmed with the BEST competition. I'm sorry, but after reading the Usage Guide referenced above (both the one linked here and the current year's copy), I still don't understand how to use the pulley and provided belt. We don't need our arm to rotate more than 180 degrees, but I don't see how we can even do that with an open belt? What do people use as a tensioner, as referenced by jmg? How do you keep the belt on the pulleys if they aren't linked, and the belt can't be altered?

I really appreciate the forum and all the helpful advice I've found here! (Including how to create the motor mount hubs, which we were lost about.) Thank you to anyone who has the time to help!
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dannyk

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Posts: 21
Reply with quote  #6 
I will try to attach a photo. Essentially the ends of the belt are screwed into a large gear/wheel (not the one included in the kit since you can't alter itIMG_20161209_123433371.jpg  and the belt is looped around the small drive pulley.
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rookies2017

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Reply with quote  #7 
Ok, thank you so much!
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jgraber

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Reply with quote  #8 
By screwing the belt to the arm-wheel-pulley, that part is using tension, not tooth-friction;  but weak point is still tooth-friction on the small drive pulley.  
You can use tension on both pulleys by using string or wire or bike-cable instead of a belt, and making a spool or string drum to wind up the string on the drive motor axle.  You can even use just the shaft coupler as a small drive pulley this way  .
Some teams use a separate wind and unwind drum to keep the strings from tangling.
You can cut a groove in the edge of a wooden pulley by using a pivot jig and a table saw set to 45 degrees
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