Clutch Motor Bogging Down On Skiving Machine ?

[CustomDoug]

I'm having an intermitting problem with a clutch motor... it's on a skiving machine [that I'm in the process of trying to figure out how to use] - sometime (usually lately) it will completely bog down under the slightest amount of load. Like when I try to feed leather through the machine. Once it does this, it will only start up again if I let off the foot pedal completely and let the motor catch up again. It's a 400W motor that I have running in the opposite direction as a regular sewing machine via a switch on it's case, as required for the skiving machine. I can actually slow the motor down enough for it to stop by the "hand wheel" while holding the foot pedal down completely. Is there some kind of adjustment I can make to help with this problem.. or is it just a bad motor? BTW, it will run fine, building up speed to it's max if there is no load added to the equation. Thanks for any help!

[Wizcrafts]

400 watts is not even 1/2 horsepower. You should be using at least 1/2 hp, if not 3/4 hp, at 1750 RPM.

For the time being, try changing to a smaller motor pulley and matching v-belt (1 inch smaller belt per inch smaller pulley).

Also, oil every oil cap and hole and clean out any skived pieces from the knife area.

[CustomDoug]

400 watts is not even 1/2 horsepower. You should be using at least 1/2 hp, if not 3/4 hp, at 1750 RPM.

The tag on the clutch motor says 400Watts, 1/2HP, 3450RPM. Also, a manual for the same type of skiving machine (typical fortuna features) suggests 200-400 watt motor with a range of 1000-1200 rpm (though that speed seems low to me) http://sunstar-swf.eu/pdf/km-76.pdf .

Could it be the tightness of the belt or maybe the screw that controls the brake (I haven't touched it)? I have oiled everything a few times now though.

[Les No6]

1/2 HP is more than enough but I certainly would run any machine at three times its rated speed, turn the skiver by hand with the motor turned of and your foot on the pedal to see if every thing turns freely if it is free there is something wrong with the motor, you would be better of changing to a 4 pole motor any way. Single phase motors have no start up torque and depending on type have separate start up windings these have very little torque and just spin the motor up to speed at which point the main windings kick in, so if the motor spins up to speed and has no torque the starter is working and the main are not, also make shure it's not a three phase motor with a capacitor wired to one of the inputs a trick used by some disreputable dealers the motor will spin up on single phase but have no torque.

[Ferg]

My skiving machine came with a clutch motor of similar size. Ran the machine with absolutely no problems.

I changed to a digital Servo and I love it.

ferg

[tnawrot2]

Clutch Motor Bogging Down On Skiving Machine ?

Can you see or hear the motor loosing RPM, or is the belt slipping on the pulleys?

[Wizcrafts]

A 3450 RPM motor produces most of its power at very high speeds only. You would be better off with a 1725 RPM 1/2 HP, 550 watt motor. That's what was in my USM Puma skiver, which I sold years ago.

[CustomDoug]

Clutch Motor Bogging Down On Skiving Machine ?

Can you see or hear the motor loosing RPM, or is the belt slipping on the pulleys?

Yes, when this happens I can see and hear it loosing RPM and the torque disappears at the same time. I think it's an adjustment thing.. as this has happened after making changes to the head.

[CustomDoug]

A 3450 RPM motor produces most of its power at very high speeds only. You would be better off with a 1725 RPM 1/2 HP, 550 watt motor. That's what was in my USM Puma skiver, which I sold years ago.

This is the motor that came with this skiving machine but I think your point's a good one. Is your 1725RPM motor a clutch or servo motor? I've been thinking about replacing this one with a Servo as I've had good luck with them on my sewing machines. But then again, I don't need the speed adjustment of the servos necessarily on a skiver.

I don't suppose changing the pulley to a smaller one on this clutch motor would be any good? It actually seems a little slow as it is... until the speed builds up.

[CustomDoug]

...turn the skiver by hand with the motor turned of and your foot on the pedal to see if every thing turns freely if it is free there is something wrong with the motor

I'll try that tomorrow.. I guess this would also tell me if the brake is set correctly too

... you would be better of changing to a 4 pole motor any way.

Yea, but I only have 110v in my garage, so I couldn't do "4 pole" - assuming that's 220v.

...Single phase motors have no start up torque and depending on type have separate start up windings these have very little torque and just spin the motor up to speed

Another point for getting myself a Servo motor.

[Anne Bonnys Locker]

A 4 pole motor runs at 1425RPM and a two pole at 2850RPM.

400W should be enough for a skiver but in the past they used fixed speed motors not clutch motors.

The high speed motor should work but they are what is called a PSC - Permanent Split Capacitor - so if the capacitor is dead it may have trouble putting out any grunt. In a previous life I used to modify 315W motors to 420W simply by changing from a 15mf capacitor to 20mf capacitor. Not all motors can be modified this way!

[Northmount]

The speeds listed above are for 50 Hz line frequency. In North America, line frequency is 60 Hz. So 4 pole motor speed, loaded, is approximately 1725 to 1750 rpm. No load speed moves closer to synchronous speed of 1800 rpm. 2 pole is 3450 rpm when loaded and moves towards 3600 rpm with no load.

I would suggest that since this problem appeared after the head was worked on, and since it can hardly skive anything without bogging down, that something in the head is either seizing up, or severely misaligned. So remove the belt and turn the pulley by hand. Should spin fairly easily with no leather in the machine.

Since it used to work, increasing the motor size to solve a seized up machine is just going to further destroy it. Solve the root problem first.

If the pulley turns easily with the belt off, then look at the motor and clutch/brake mechanism.

Is the bell knife sharp? Jamming leather into a dull knife will slow the machine down cause it has to wear away the leather instead of cutting it.

Tom

[Les No6]

I'll try that tomorrow.. I guess this would also tell me if the brake is set correctly too

Yea, but I only have 110v in my garage, so I couldn't do "4 pole" - assuming that's 220v.

Another point for getting myself a Servo motor.

4 pole motors have half the speed as mentioned and twice the torque compared to 2 pole of the same size (shaft power=speed x torque) and the motors run at full speed or there about all the time when on and produce enough torque to maintain that speed until the maximum load then at which point the torque drops to starting torque (very little) its the clutch that varies the speed, load, you dont start the motor under load ie clutch engaged. You would be better off replacing the motor with a 4 pole, there's no point in putting a servo motor on a skiver, the Chinese servo (not really servos) motors are more expensive and less reliable than than a cheap clutch, 1/3-1/2hp is all you need. And as Tom says check the head running with a fault will only make things worse and this is the important expensive bit.

[CustomDoug]

How do you know if it's four pole or two pole exactly? It doesn't say either on the machine's tag plate. Is it just the max speed that indicates which is which? BTW, my motor reads '60 Hz'.

[Les No6]

It's usually on the plate how many poles it has and speed but some just state speed, 1725 is 4 pole, 3450 is 2 pole, the 60Hz is the supply frequency.

[Ferg]

I beg to differ with "there's no point in putting a servo motor on a skiver". My skiver has a digital servo. It will turn at almost nothing to 3600 rpm.

The speed depends on how hard I press on the pedal, duh! This servo is the best thing I have ever done. The bell knife and bottom and top feed wheel

turn at different speeds. There is a ratio there. I can have a very thin piece of expensive leather to skive. I don't wish to allow it to feed at 3600 or whatever

rabbit speed is available. A nice slow skive gives me total control. If I desire to increase the speed after starting the skive it is a no brainer.

There is absolutely no degradation in the quality of the skive when I run it slow . That misconception should be noted for folks looking down the road buying one of these fabulous machines.

ferg

[Les No6]

I beg to differ with "there's no point in putting a servo motor on a skiver". My skiver has a digital servo. It will turn at almost nothing to 3600 rpm.

The speed depends on how hard I press on the pedal, duh! This servo is the best thing I have ever done. The bell knife and bottom and top feed wheel

turn at different speeds. There is a ratio there. I can have a very thin piece of expensive leather to skive. I don't wish to allow it to feed at 3600 or whatever

rabbit speed is available. A nice slow skive gives me total control. If I desire to increase the speed after starting the skive it is a no brainer.

There is absolutely no degradation in the quality of the skive when I run it slow . That misconception should be noted for folks looking down the road buying one of these fabulous machines.

ferg

You can beg to differ all you want but you don't need much speed control on a skiver in fact you can just use a regular motor with just on and off as a lot do. Skivers are not difficult to use most of the know how is setup and adjustment it's quite easy to pick up even for a complete beginner such as your self. And as far as motors go you control the speed of a clutch motor by how HARD you press the pedal, with servo and electronic clutch (Chinese servo) you control the speed by how FAR you press the pedal, Since you don't need pin point accuracy with a skiver and once proficient you just want press a go the cheaper and more reliable clutch motor is a no brainier.

[Ferg]

Well, doggone! I knew I had a problem, I am just a beginner!

You may know, there are just about as many ways to do things with machinery as there are folks using them.

I chose the servo because it works for me and I am sure for a lot of other beginners. I just may be a beginner the rest of my life

but I am happy with my skiving machine running with a servo motor. Maybe I should attach at least three more motors to make it look like I know what I am doing.

ferg

Edited March 5, 2013 by 50 years leather