Speed-up or slow-down belt drive

I need about 67 rpm on a shaft. An 1800 motor with a 40 to 1 gearbox = 45 An 1800 motor with a 20 to 1 gearbox = 90 Of course, Automation Direct doesn't have a 30 to 1 box and I want to use them as a supplier. The output of the gearbox will have a belt to drive the shaft but should I use the 40 and step up the speed to the shaft with the appropriate sheaves or step down the speed from the 20? Or, does it not make any difference?

Torque doesn't factor into this, I'm upgrading from 1/10hp single phase to

1/3hp 3-phase...and it's CHEAPER!!!
Reply to
Tom Gardner
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For no particular reason I seem to believe that two reductions are better than one reduction and one increase. Just for fun, you might calculate it both ways to see if one is easier with stock pulleys. Even if you use an adjustable pulley, you might find one way easier or cheaper to implement.

Don Young

Reply to
Don Young

Why not use a VFD to control the speed of the 3ph motor? Then you can have any reasonable rpm you want. That size would be rather inexpensive, also. Respectfully, Ron Moore

Reply to
Ron Moore

If I recall correctly ( and since I was mostly an electrical engineer it is a big if ) the smaller pulley limits the power that a belt can deliver. So for the same size pulley on the driven shaft, you would have a bigger pulley on the gearbox if you used a 40:1 gear box and stepped up the speed.

Dan

This may not be the right answer, but I bet it prompts some comments.

Reply to
dcaster

What Ron Moore said.

Will the budget stretch to $160 for a 1 HP VFD?

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Use the 20:1 gearbox and set the VFD to 74.44%? Perhaps use a heatsink on the motor to compensate for less 'fan effect'?

--Winston

Reply to
Winston

I would step down from the 20.

If you step down to below load speed and then step back up, the max torque in the system is greater than load torque. Not that it matters in this case but I thought I'd mention it.

Reply to
Don Foreman

Out of the budget and somebody would dick with it.

Reply to
Tom Gardner

I have to make twelve units and the one speed will do just fine.

Reply to
Tom Gardner

It just seems natural to reduce to speed, I don't know why. Would the 20 box be more robust and run cooler, last longer, etc.?

Reply to
Tom Gardner

You remember correctly. Assuming everything is sized to the load, two reductions will result in a more compact and cheaper drive.

Reply to
Ned Simmons

I'm a big fan of Automation Direct, but why are you stuck with them? Oriental Motor makes small and smaller 3-phase gearmotors in just about any power and ratio you could want. They stock the component motors and gearheads to make just about anything they list. Figure around $250 for a typical gear+motor.

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Reply to
Ned Simmons

If designed to the same specs for efficiency, lifetime and power output the boxes should be quite similar. Gear volume generally depends on power level (speed => diameter, torque => thickness, power = torque * speed, power in = power out + losses).

I don't know what the case might be for the two particular examples you have in mind.

Reply to
Don Foreman

You should get a 'Martin Gear' catalogue with all the specs. on pulley size, HP rating and the rest of the info you need to design your system. I think they have a website with the same info.

John

Reply to
john

I would consider the Oriental Motor solution to be the most cost effective, because of OM's quality and reliability. Available in reversible, single or three phase models up to about 1/8 HP or slightly higher, with the gear reduction providing higher torques at lower speeds, such as the speeds Tom G was asking about.

The VFD solutions hardly seem worth consideration, since the only frequency required (and highly dependable) is line frequency.

I've seen case lots of new Oriental Motor components on eBay in the past, and I doubt that a better value is available anywhere.

They have numerous styles of gearheads in single-output-shaft, selectable right or left side right angle shaft or dual RA shafts. I believe most of them are entirely ball bearing gearheads, including ball bearing assemblies on both ends of the internal gear shafts (also the motor shafts). Additionally, there are models with electric brakes, clutches, (or both), impedence protected, thermal protection, and tachometer output (and maybe a couple of other features). I've seen some models fitted with optical encoders as an add-on option from OM.

WB ......... metalworking projects

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Reply to
Wild_Bill

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