variable speed pulleys

[RussZHC]

Does anyone have experience using items from:

http://www.speedselector.com/


I have fiddle with adjustable pulleys before but they were much simpler with just a moveable side that you tightened down with a set screw.
These are not "simple" and not all that cheap but...would solve some issues and gives me another choice.

[millwrong]

If memory serves, B.C. Bearing handles that line. Basically any of the bearing supply houses offer variable speed sheaves. Try Princess Auto if budget is a factor, otherwise there's a bearing supply house on Higgins St. that generally has the better pricing for commercial/industrial. Depending on horsepower, a VFD will be cheaper, and simpler to use.

[wierdscience]

X'2 for the VFD.The VS belt drives bleed horsepower,noisy and cost a fortune.

[J Tiers]

X'2 for the VFD.The VS belt drives bleed horsepower,noisy and cost a fortune.

The one thing FOR any belted or geared speed changer that does NOT require a motor speed change is that power will be more-or-less constant at any speed.

With the VFD, you can change speed, but you lose power going slower, OR in most cases by going significantly faster. With a VFD, max power usually is with NO speed change.

it's sort of funny for anyone to complain that a VS system "bleeds HP" , and then they maybe advise you to crank a VFD to half speed, dropping HP to 50% of normal. That "bleeds" just as much if not considerably MORE, depending on speed change amount.

This may not matter in many cases, most don't USE full power on their machines. But when and if you DO, it is good to know how max power is affected by speed with the speed change mechanism you use.

[wierdscience]

The one thing FOR any belted or geared speed changer that does NOT require a motor speed change is that power will be more-or-less constant at any speed.

With the VFD, you can change speed, but you lose power going slower, OR in most cases by going significantly faster. With a VFD, max power usually is with NO speed change.

it's sort of funny for anyone to complain that a VS system "bleeds HP" , and then they maybe advise you to crank a VFD to half speed, dropping HP to 50% of normal. That "bleeds" just as much if not considerably MORE, depending on speed change amount.

This may not matter in many cases, most don't USE full power on their machines. But when and if you DO, it is good to know how max power is affected by speed with the speed change mechanism you use.

VS belt drives are constant torque drives,if you halve the speed you halve the hp at the driven shaft.This is true so long as the spring loaded sheave is on the motor shaft.The VFD can be setup as either a constant speed or constant torque drive,but you also have the option of adding encoder feedback and eliminating slip.

Either drive type is most efficient at no more than a 3:1 ratio and most VFD's that I have installed have had better numbers at 600 rpm than any VS belt they replaced.

The two are really apples to apples comparisons until you factor belt losses.A VS belt bleeds power even when the drive is running unloaded.This is more true of the wide belts than the v section,but it's still there.I won't even start down the slippage road.

In this day and age a 1hp VFD can be had for less than a 1hp VS belt pulley and you don't have to change shaft centers to change speed.When you factor in maintenance costs the VFD is the hands down winner.

[Ian B]

Weird,

The VS belt drives being talked about - they're just simple spring loaded cone pulleys. You screw one in or out, the spring on the other takes the slack.

I always thought they were variable speed, variable torque, constant power drives. Make the driver pulley smaller, the driven larger and you get less speed, more torque.

I'm sure there'll be some slippage as with all friction belt drives, but they shouldn't be too noisy or inefficient. The ratio of 3:1 (up or down) is probably about right.

Ian

[brian Rupnow]

They work great--I use then on bakery conveyors. They are adjusted by a manual take up that changes the pulley center distance to pull the belt deeper into the V of the spring loaded pulley, thus chaning the ratio.---Brian

[lazlo]

VS belt drives are constant torque drives,if you halve the speed you halve the hp at the driven shaft.This is true so long as the spring loaded sheave is on the motor shaft.

The VFD can be setup as either a constant speed or constant torque drive,but you also have the option of adding encoder feedback and eliminating slip.

The Reeves Drive (variable-width sheaves) are constant power (Ian has a good description of why). That's their major advantage: you retain full horsepower at low RPM. A VFD is constant torque, so you have half the horsepower at half the RPM, quarter horsepower at 1/4 RPM.

But I agree, in this day and age, just double the motor size and put it on a VFD. That's what Monarch and Hardinge did on the final versions of their hallowed toolroom lathes.

[gnm109]

I have a Variable Speed rig on my 3 hpWebb Mill (BP clone). It works very well and makes close to no noise. I've yet to notice a lack of power at any speed from 60 rpm to 4,000. I run it with an RPC.

The reason I went with an RPC is that I can fix one of those when they break. If I had a VFD, I'd probably just have to drop it in the waste collection if it broke.

I know, I know, they never break. Right.

[Peter.]

My Denford lathe comes with them as standard. It doesn't like to run at full speed as the (admittedly non-standard) belt doesn't like to make the tight radius on the driven pulley.