Poly V-belt System Design Questions

[motoman287]

Hi,

I'm designing a portable machining apparatus for a specialty application, and due to space constraints, was looking at using a poly V-belt to drive a spindle off of an electric motor. The motor is used for another application, and so the goal is to use the same motor, and simply change the speed ratios for each application. The motor we've spec'ed out is an 8000 rpm, 1/2 HP DC. My speed ratio is 2:1 (I need final drive to be ~4,000 rpm). Again, due to space constraints, the center to center distance is ~2.94 inches.

I've tried using a handbook from Dayco to calculate everything, but their numbers don't list a driver with an rpm higher than 3450, and tried contacting Goodyear with no luck.

I guess my question is, what is the smallest dia. sheaves I can get away with, and is there any issues anyone foresees with the speeds I'm running and the short center-center distance?

Any input is appreciated. If there's something I can clarify, please let me know.

Thanks.

[PinkertonD]

due to space constraints, the center to center distance is ~2.94 inches.

How does that 2.9" center distance compare with the diameters of the motor and the device to be powered? Will they touch each other?

Is there room to adjust the belt as they are not an exact circumference. It sounds very tight to me and I am not sure you will find a belt small enough that will transmit 1/2hp. Usually belts that small are cross-section-rated for fractional HP.

The 8,000rpm is not really belt-territory.

Have you considered gears as the motor should be reversible?

What about chain?

If you want to stay with a belt then the manufacturers will be in a better position to advise you on HP ratings and minimum diameters.

[motoman287]

The motor is oriented parallel with the spindle shaft, but offset the 2.9" rather than inline, and "flipped" so that they won't touch. And yes, I've allowed some room for adjustment.

I thought I remember reading on Goodyear's site or somewhere that their poly-v belts are rated to 10,000 rpm? We've considered gears/chain, but ideally want something low maintenance, quiet, and smooth running.

We currently use a 4 ribbed J cross section belt in another application with a much larger center-center distance, and I was hoping one would be able to use something similar in this instance. The speeds are slower (3450 driver rpm, 4312 driven), and the smaller driven pulley has an OD of 1.44". If I could get down to a 1" drive and 2" driven pulley that'd be ideal and meet my space requirements, but I don't know if that's possible. I'm new to some of this and am learning as I go.

Thanks for the input!

[RWOLFEJR]

Take a look at this...
I didn't run any of these but did save to favorites for future reference. Looked pretty slick.
http://www.gatesprograms.com/ptsavings/toolbox

Helical gears would be worth looking into?

[PinkertonD]

and "flipped" so that they won't touch.

Does that mean "end-for-end?" If so then direct couple them and use a PWM motor speed controller with it locked at 4000-RPM.

Check that the DC motor is designed for reversible operation. Often high-speed motors have the brush guides angled slightly in favor of the design rotation to minimize brush-lift at higher RPM. Running such motors against their design rotation can result in highly accelerated brush and commutator wear.

You could visually check arcing at the brush-commutator and see if there is noticeable activity in one direction over the other. Try checking the motor manufacturer's website for that part number and see if it is "Reversible."

[motoman287]

Well, I've found that for a J-section belt, .80" is the smallest recommended sheave diameter, and my speeds are acceptable. Even though this is all good news, I'm still getting interference with some traverse rails on the system. Due to space constraints, the only other acceptable position for the motor to be mounted is 90 degrees to the spindle and I suppose I could use bevel gears. Does anyone have any good links to gear manufacturers and/or some good 3D CAD models? I'm using Solidworks '11.

Thanks!