Belt and Pulley 1

[Omar7amdi]

Hello,

Suppose this pulley is latched to a motor's shaft residing on the floor. On the ceiling there is a similar pulley hanged on a hook. At the center of the belt's height there is an object carried by the belt. When I ran the motor sometimes the belt's teeth does not lay on the pulley's groove which causes the object's position to not be coherent with the motor's rotation. I tightened the belt and the problem still comes from time to time? The motor is moving forward and backward.

is there any idea how to solve this problem?

Thanks

 

[JohnRBaker]

You need to provide a better description, perhaps with pictures/drawings of the overall set-up before anyone could give you any idea what to look for.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Omar7amdi]

Hi John,
Here is a drawing.

 

[Sparweb]

What is keeping the belt in contact with the "object". What is the object? We cannot guess.

STF

 

[byrdj]

how about using outer idlers to keep prevent oscilations in the belt causing it to jump a tooth.

 

[Omar7amdi]

Hi Byrdj,
Thanks it's a good idea.

I added the bottom roller only, where the motor pulley. But I did not add the top one. By the way the upper pulley
has no teeth, it's a roller. But the motor pulley still skips the belt teeth sometimes and as soon as start skipping it stays doing it.

 

[Omar7amdi]

Hi SparWeb,

The object is a trolley. Both belt ends are fasten on the trolley. The trolley carries 10-20 lb rod.

 

[MikeHalloran]

You need to guide the carriage; you can't rely on the belt to do that.
Unless you need the carriage to move _very_ fast,
you need a gearmotor, and/or a variable speed drive.

If there's any risk of anyone getting hurt, and it sounds like there is,
you need to get an actual engineer involved.







Mike Halloran
Pembroke Pines, FL, USA

 

[Omar7amdi]

Hello MikeHalloran,

Yes I'm using a gear with a variable speed. The speed plays role in the problem occurrence. It takes more than 3 hours ,continuous running, before the problem occurs. As soon as it occurs it keeps continuous occurring. The trolley out of sync with the motor rotation.

Thanks.

 

[gruntguru]

Perhaps you need two outside idlers at the bottom - one each side of the motor pulley. There are really only two possibilities for your failures:
1. Belt oscillation during rapid travel is allowing a "slack" wave to ride around the motor pulley.
2. The belt is under-rated for the loading applied.

Either way, two idlers at the drive pulley will help by increasing wrap angle on the drive and isolating it from oscillations.

je suis charlie

 

[Omar7amdi]

Thanks gruntguru , I will consider it.

 

[JohnRBaker]

Sounds like it might be a heat problem which could cause the belt to stretch to the point where the lugs on the belt no longer match the grooves in the pulley. Have you considered replacing the belt/pulley combination with a chain/sprocket scheme?

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Omar7amdi]

Thanks JohnRBaker. I'm getting ideas to solve it. I'll consider it.

 

[Jboggs]

If the belt is tensioned properly, and if the object's weight isn't enough to cause the belt to slip, the next most likely condition is that you have mismatched tooth profiles. There are numerous different tooth profiles in use around the world for different purposes and it is a very common problem to end up with a belt of one profile and a pulley of a different (but very similar looking) profile. Google "synchronous belt tooth profiles". Mismatched profiles will eventually jump. I have seen it many times. Carefully double check the exact profiles you are using.

 

[Omar7amdi]

Thanks Jboggs, I'll look at that.

 

[kjoiner]

Omar,

Adding onto the excellent suggestions posted above, have you run through the process of sizing the belt - selecting the profile and width? Some of the newer profiles such as the GT2 etc. are better at resisting slippage than the trapezoid types. What is the distance between the drive pulley and the idler pulley? How many teeth do you have in contact on the drive pulley? What are your torque and power requirements?

I would recommend contacting some of belt and pulley manufacturers to get their input as well - Gates and York Industries are a couple that come to mind. I would also recommend using a timing pulley at the top idler position since there are teeth riding on it. It will be quieter and is more appropriate. If you do use a timing pulley at the top, make sure your are spaced an integral tooth count apart. You can use smooth rollers as tensioners since they are running on the back side of the belt.

Kyle

 

[Compositepro]

Tooth jumping is a common problem on long belts. You have to use idler pulleys on the back side of the belt near to the toothed sprocket.

 

[zeusfaber]

The unloaded section of belt in this arrangement is the bit that sits between the load and the driving pulley. The logistics of constraining that section to stop it flopping about and feeding oscillations onto the pulley are complicated by the fact that the load is moving through the space you're trying to control. Moving the motor to the top would avoid that issue by moving the slack to the back of the belt - a section which is constant in length and amenable to the addition of idlers - you are better able to judge than us whether that's a viable change.

Do you know whereabouts in the stroke of the system it starts to skip? If it happens at the bottom, it could just be the stretch in the belt feeding too much slack into the drive pulley. If you think this is happening, you might add a tensioning spring to the belt attachment on the bottom of the platform.

A.

 

[Omar7amdi]

Thanks very much for all participants. I hope all thoughts would help me overcome the problem.

 

[Omar7amdi]

Hi all,
I have to add this.
The post that carries the trolley between point A and B is not perfect, straight. The distance between A and B is 300 cm.
When I put a laser light at point A to pint at the wall, by the time the trolley at point B, the laser light deviated by 15 cm.
The light should remain vertical " perpendicular " , at right angle.
Distance from A to B = 300 cm; deviation ~= 15 cm.