Flat belts

[Jonesy]

Got a question about running flat belts.

Anyone got any experience of running 2, side by side, touching? Each one 1 inch wide on 2 inch pulleys?

Or same principle, regardless of belt width?

[Captain K]

The centre of the belt wants to ride on the crown of the pulley, so I don't think that will work. Each belt will run of its side i would think. If the pulleys are truly flat there is no way to make the belt track.

[Rich Carlstedt]

Can't work if the pulley is crowned - as most flat belt pulleys are
If you are talking about a common straight ( ie flat) pulley for the two belts and separate crowned pulleys on another system (s) , then you may have it work.
Trying to balance the tracks to run without interfering each other is like juggling jello

Rich

[TGTool]

Plus, it may be difficult to get both belts exactly the same length, so one may be doing most of the work and the other not. That would hamper the load capacity.

[Jonesy]

What about this... flat pulleys with raised flanges.. no crowns.

Assuming both belts identicle.

Actual pulleys will be 2" driven turning a 14" slave.

[BCRider]

Nope, that won't work either. Odd as it sounds the belts will try to climb up the conical sides. That's why the crowned pulley idea works. the belt wants to track to the path of the highest/longest path. The only way to do what you want would be to have vertical or extremely steep sides. Like nearly vertical.

And while it might work like you want if trapped onto the middle with steeper sides there's the issue that one belt will inevitably try to walk over and press against the other. I imagine that this will cause some wear since there will be some small but significant difference in how each belt runs and tracks.

What's the big deal about getting the proper width of belting? It'll make your life a lot easier.

[Bented]

I make these fairly often in various diameters and widths, this particular order is for idler sheaves that the back of timing belts run on, very flat.

Make them like so, change the dimensions for the belt width and sheave diameter.

[Jonesy]

Trying (as always) to work with what I've got. And I've got tons of 1" composite belt.

The pulleys arn't made yet. I can make straight flanges no probs (but not to Bented's standards!).

There will be an idler / tensioner on the ouside of the belt(s) on the slack side to give more contact on the smaller pulley. Maybe this will help with keeping them in place on pulleys with straight flanges.

I know this is doing it the hard way but I always do everything the hard way. Makes life more fun. Buying is boring.

@Bented.... is that design for 2 belts side by side?

[Bented]

The pulleys arn't made yet. I can make straight flanges no probs (but not to Bented's standards!).

@Bented.... is that design for 2 belts side by side?

I have no standards, when using a CAD system the part is drawn by the numbers (-:

Yes, if you are concerned about the belts rubbing together simply turn a groove for each belt with a flange between them.

[BCRider]

Bented, that center bead is tall enough to stop the belt from climbing over it? The outer flanges look great. But that center one seems like it's not tall enough... Or perhaps it's just the drawing.... What is the OD of the center rib supposed to be? Or could it be modified to suit the nature of the belting? I'd think that the rib should be the same or a bit taller than the thickness of the belt. Or for the toothed belts running on the outer smooth side then the same or a bit taller than the thickness of the flat portion?

[darryl]

Two flat belts side by side- one will take the first opportunity it gets to climb onto the other.

[tom_d]

Plus, it may be difficult to get both belts exactly the same length, so one may be doing most of the work and the other not. That would hamper the load capacity.

^THIS^

One belt will do all of the work, the other will just be along for the ride. They would need separate tensioners which of course add to cost and complexity. That's assuming the tracking issues can be addressed. To successfully run multiple V-belts all of them must come from the same batch. V-belts are more forgiving in their tensioning requirements, and even at that it's better to have all of them made as one, with one common backing keeping them joined as if one belt.

[darryl]

Way more advantageous to get the job done with a single belt. You say you have tons of 1 inch belt- that suggests that you make belts to suit from a roll of stock. If that's the case, you could also bond two belts side by side to make them one. Why stop at two- make it three belts bonded together. Stagger the joins and you have a three inch wide belt that will easily go around a two inch pulley. You could easily overdrive that to get say a lot of power to a high speed spindle- a thin, flat, urethane belt is pretty good at doing that. You might need to slightly groove the small pulley so you don't lose grip by creating an air film between the pulley and the belt.

If you aren't making belts from stock- well at any rate I would look at bonding the belts together to make one rather than trying to run two side by side. Or just stick with applications where the 1 inch belt is strong enough. I wonder how far it can be pushed?

[Richard P Wilson]

^THIS^

One belt will do all of the work, the other will just be along for the ride. They would need separate tensioners which of course add to cost and complexity. That's assuming the tracking issues can be addressed. To successfully run multiple V-belts all of them must come from the same batch. V-belts are more forgiving in their tensioning requirements, and even at that it's better to have all of them made as one, with one common backing keeping them joined as if one belt.

Provided both belts are new, are the same manufacture and are being joined with traditional alligator clips, then its not difficult to make them the same length, and they should wear and stretch the same. In theory.
Its worth trying, after all the OP has the stuff on hand, and if it doesn't, then hey, he'll just have to shell out for a 2" belt, but I don't think a 2" belt is going to like going around around the 2" pulley that he mentions.

[Jonesy]

Thank you all for the advise.

I'm working on the drive for a lathe...

Motor to countershaft.

Then countershaft to lathe.

1.5HP motor. 3PH, 50HZ, 1400 RPM. Inverter.


3 step pulley on lathe... 7.5", 6", 4.5". All 2" wide steps. Very slight crown.

The countershaft step pulley is made from very dense ply. Same dims. Not crowned.... yet.

The motor pulley is 2" diameter and 2 1/4" wide (largest I could get away with from the block it was turned from). Still flat. Not crowned.

The slave pulley (14") is not yet made.


All the flat belts are old / new stock. Far too long to use as they are so need cutting down.

I made a belt for a recent project and it worked well. Simply scarfed and super glued. Could not pull it apart. Tried hard! The belt was a little stiffer where it was glued.

Glued up a test belt last night using contact adhesive. Will check the shear strength tonight.


The motor and slave pulleys can have flat flanges, and a center flange can be added.

Can't do that to the 3 step though. Interesting idea to join 2 of them together, Some experimentation required.

I'm 'fairly' confident I can make pairs the same size.