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Unread 24-06-2016, 16:50
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Re: pic: Another Belt-In-Tube Drivetrain

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Originally Posted by Mark Sheridan View Post
yeah we have broken HTD 15mm with 18 tooth.
Do you mind providing details on what parts you were using and how it failed? The 18t VexPro timing pulleys are plenty strong enough for use in an FRC drivetrain under normal conditions, but as Chris explained earlier, there must have been some slippage and racheting going on that lead to your failure.

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Originally Posted by asid61 View Post
Cripes, that's a ton! Who knew that such tiny changes could have such an effect...
The difference between trapezoidal and HTD is just as great somehow. It's a shame that GT2/GT3 is patented, otherwise Vex would be able to produce them (I think?). Does anybody know why Vex doesn't use GT2?
Also, can GT2/GT3 belts be used with HTD pulleys, and what effect does that have?
Yes, the GT belt profile is trademarked. (GT stands for "Gates Tooth," so they made sure everyone would know who came up with it.) This means that Vex cannot produce ACTUAL GT belts or profiles. But there is nothing against measuring the belt teeth and coming up with a very very close approximation to the GT profile. So if you look at WCP's page on the GT2 belts and pulleys they sell, they refer to it as "GT2 compatible profile." I assume that this is just a legal workaround to use the GT profile.
And yes, I believe that GT (3mm) belts can be used with HTD (3mm) pulleys, and if I recall correctly, it performs about as well as HTD with HTD.
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Unread 24-06-2016, 19:11
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Re: pic: Another Belt-In-Tube Drivetrain

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Originally Posted by Cothron Theiss View Post
Do you mind providing details on what parts you were using and how it failed? The 18t VexPro timing pulleys are plenty strong enough for use in an FRC drivetrain under normal conditions, but as Chris explained earlier, there must have been some slippage and racheting going on that lead to your failure.
No slippage or ratcheting. We have good control on build quality to get our Center to center right. its was overloading with too many cycles and the belts snapped on our drive. Our practice bot easily runs 100 simulated matches in a week. So we always have the practice bot on a lifecycle far ahead of the comp bot to catch these sort of failures.

971 helped us out and pointed out that these belts are being loaded beyond their recommended limits. We built a calculator just to double check belt loading. We also swapped a bunch of belts on the same drive rail and noticed despite the same CC, the tensions were different. We try to reduce belt load and build in tensioners which is what we did this year. The last conversation I had with the students is that we are in the mood of having the drive on the practice bot survive with minimal maintenance for over 1000 simulated matches. we are just sick of worry about this stuff, so keep in mind that perspective.

I think using 22 tooth pulley and 15mm wide GT profile belt will be a step in the right direction for Ty's design, which is pretty sweet.
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Unread 24-06-2016, 19:58
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Re: pic: Another Belt-In-Tube Drivetrain

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Originally Posted by Cothron Theiss View Post
Yes, the GT belt profile is trademarked. (GT stands for "Gates Tooth," so they made sure everyone would know who came up with it.) This means that Vex cannot produce ACTUAL GT belts or profiles. But there is nothing against measuring the belt teeth and coming up with a very very close approximation to the GT profile. So if you look at WCP's page on the GT2 belts and pulleys they sell, they refer to it as "GT2 compatible profile." I assume that this is just a legal workaround to use the GT profile.
And yes, I believe that GT (3mm) belts can be used with HTD (3mm) pulleys, and if I recall correctly, it performs about as well as HTD with HTD.
Pretty much,the belts are not produced by Gates and the profile is not the same as the GT2 or GT3 profile by gates, it slightly different. Will be putting up test data over the next few months to compare the profile we sell vs Gates GT2/G3.
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Unread 24-06-2016, 20:07
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Re: pic: Another Belt-In-Tube Drivetrain

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Originally Posted by R.C. View Post
Pretty much,the belts are not produced by Gates and the profile is not the same as the GT2 or GT3 profile by gates, it slightly different. Will be putting up test data over the next few months to compare the profile we sell vs Gates GT2/G3.
That's excellent, thank you! Any chance you can also throw in testing of HTD so that teams can compare your data against something most teams are more familiar with?
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Unread 24-06-2016, 20:18
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Re: pic: Another Belt-In-Tube Drivetrain

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Originally Posted by Cothron Theiss View Post
That's excellent, thank you! Any chance you can also throw in testing of HTD so that teams can compare your data against something most teams are more familiar with?
Will do. Let me know if there is anything specific you'd like in terms of testing.

As a side note the pulleys we sell and future pulleys we will be releasing are the actual GT profile. The pulleys are free game for anyone to sell/make just not the belts sadly.

Thanks!
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Unread 24-06-2016, 21:32
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Re: pic: Another Belt-In-Tube Drivetrain

Quote:
Originally Posted by R.C. View Post
Will do. Let me know if there is anything specific you'd like in terms of testing.

As a side note the pulleys we sell and future pulleys we will be releasing are the actual GT profile. The pulleys are free game for anyone to sell/make just not the belts sadly.

Thanks!
That's great news! It'll be interesting if teams can use the more compact GT pulleys to make belt-in-tube drivetrains using the 2x1 VersaFrame.
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