Pulleys - interesting observation

[DNic]

Hi Pete, Again 4 x longer than the total single belt length. Tie the appropriate knot & loop the very long belt 4 times. It takes a bit of care & practice not to get it tangled up
Note it does help if the motor is in a separate motor pod, as mine is as moving the pod can take up variations in belt length.

Cheers

 

[PeteAugello]

loop the very long belt 4 times

I finally understand what you mean, lol. I had thought that you meant that I should move the motor several feet away and use an extremely long loop.

Pete

 

[ripblade]

Hi,
Thread Length. Pete. All you need to do is cut the length of thread 4 x longer, Then Loop them into the into one length.
Platter design. Mark, completely an option. just a little harder to get the top platter aligned correctly. I have done one similar with pointed grub screws.

Cheers

What is the advantage of a 4x loop vs a single loop, or some other length?

I went down a rabbit hole with my custom belt drive turntable, testing various combos of belts, belt material, and pulleys. I came to a couple of conclusions. I built an Arduino speed controller with SineWave/SpaceVector control of a 3 Phase motor for very stable motor performance, so focused on the belt and pulley to really get the last bit of optimal speed control out of my system.

My observations:

1) round silicone belts are terrible for speed consistancy, they move A LOT
2) EPDM round belts are pretty good
3) dual round belts are better than single belts, but have weird spikes in speed stability
4) cheap flat belts are better than round belts, but require a pulley that can keep a flat belt centered.

I have a very nice crowned flat belt pulley, but the one pulley that provided the best performance? A GT2 timing belt pulley. WITH RIDGES!!

I am wondering why. Does a smooth flat belt pulley load a lot of the tension at the two ends (aka stretch before the belt engages the pulley, slack after it releases)? Is a timing pulley performing better because the gaps during rotation allow smoothing of the belt tension during pulley rotation?

Have you tried twisting the flat belt? It is sometimes recommended that a single twist (180°) after the pulley or a double twist before and after the pulley is desirable. I'm told it is to reduce fluttering as the belt is sheared off the pulley vs being tugged straight off. A single twist also has the supposed advantage of wearing both sides of the belt.

I'm curious to know, if you tried it, what your observations were.

 

[Stuey]

Many pullyes are bell-shaped and then the belt will automatically ride on the fattest part of the pulley.

Jan

Jan, I think that's what was meant by a 'crowned' pulley, or at least that was my take.

 

[DNic]

Hi Ripblade : With the 4 looped tread belt there are two advantages

• the knot get's buffered in the bundle of thread, so is far less intrusive on speed.
• Have 4 treads help at start up time, similar to two belts.

But again none of these perform as well as Mylar.

Cheers

 

[ripblade]

Thank-you!

 

[es-hovertech-audiolab]

Matching the shape of the belt to the shape of the pulley will be very important.