Why WCP said that the Gt2 and HTD belt don’t need tension, however the chains do need tension. Does it because belts can not stretch while chains will stretch during the competition?
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Note the “Once set up” before the part you circled. It is claiming that you won’t need to adjust the tension once you have the belts in place.
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Chains will “stretch” due to each join wearing tiny amounts, think 0.001 or less. This compounds over 70 or 80 links adds up fast. Belts don’t have that issue because the are actually a composite with either glass or Kevlar fibers running through them preventing stretch from tension. For that reason you can set you belts at the right operational tension and forget about them
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Thank you very much！I think that is the reason. However I still set a cam because I think it is easier to assembly pulleys.
As long as that cam doesn’t slip, I guess there’s no harm, but timing belt is quite stable over time period far longer than most FRC robots ever see. Automotive timing belts are usually scheduled for replacement every 100,000 miles, and if ignored, three times that long is rarely an issue.
ok, I see, thank you!
Although they don’t stretch much once installed, automotive timing belts do have tensioners. The tensioners are generally locked down once the belt are tensioned, The belts are also way oversized for the load they transmit.
I’m not sure that cam is going to do what you think it will anyway. For the cam to work, it needs to be able to move whatever it’s pushing against. Hard to tell from the rendering, but it appears that the gearbox is screwed in.
If you set the cam up properly all of the loads should be passing through its pivot point, thus the loading on it should be self locking and it will be incapable of slipping.
3D Printes which mostly use GT2 have tensioners usually a bolt that pulls on one of the pulleys or a spring but once set you usually don’t have to change it until the belt has really really been used for a long time.
The idea is the motor mount is slotted. You tighten the screws until they are almost tight, then use the cam to tension the belt, and only then do you clamp the bolts down all the way. The cam will also stop the motor from slipping under the tensile load of the belt after installation.
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