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Rockwell Pulley

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Woodbass

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Apr 7, 2007
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I have Rockwell Lathe 46-111. I beleive it has cast zink pulleys. Am I limited to motor horsepower with these pulleys. The manual lists 1/3 and 1/2 HP motor options. Can I use 3/4 HP? It is a DC with Variable speed. Were can I find a rating for this type pulley?
Thanks, Woodbass
 
First, understand that I'm no mechanical engineer and am not qualified to speak to the issue of "limits" regarding any mechanical device. Nevertheless, it seems to me that the horse power of the motor, aside from having the capability of providing greater torque under load, shouldn't make that much difference. A 1750 RPM motor will run at 1750 RPM (that's usually a no load rating) whether it's a 1/3, 1/2, or 3/4 horse power device. The 1/3 HP will stall with less load than the bigger motor but I don't see what other difference there could be.

050207
Yes, I suppose that the higher torque could cause the pulley to come apart if things got jammed up; like a BIG catch ... But this is a belt driven machine and I'd expect to see belt slippage before pulley disintegration, especially on a keyed shaft. There is one aspect that I overlooked, that being the difference in shaft size from 1/2 to 3/4 HP. The driving pulley from the 1/2 HP motor is probably designed for a smaller shaft than the 3/4. I'm interested in the technical info. you find in your research so please share what you learn.
 
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Nuturner, thanks for the response, that was where my thoughts were going also. Being a keyed shaft a higher torque could make the pulley come apart. With the open issue of HP rating on the cast zink pulley, I still wonder if there is enough load while turning to cause a problem. With use of the variable speed, I will reduce the shock load at start up.
 
I don't get anyone screaming Don't do it. Not sure if that is a good sign. Delta service centers have benn little help on the subject. Not sure that its worth the persuit. I think I will need to take a chance. What is the worst that can happen?
 
Can't remember the model of my rockwell but it is similular to yours. The 1/2 horse gave up a year ago. Got a 3/4 horse of the same frame and it has been going strong. No problem with the pulleys at all. They are both keyed pulleys.
 
johnston - thanks for the reply, that is great news. Do you know if yours are cast zinc? Mine are light weight and look like a white metal. the top one has holes for indexing. Thanks again
 
Machinery's Handbook is silent on pulley design vs HP, except for arc of contact, etc. For the speeds we usually deal with, belt selection is pretty much "one size fits all" for anything less than about 1.5HP. At worst, I think you might get a slightly shorter service life from the belt. Never hurts to have a spare belt on hand, anyway, especially if you need to replace it on a Sunday evening or such. I'd hope that the drive train was designed with the belt as the weak link.

Joe
 
johnstun - thanks again, this has been a great help.

Joe - I was planning to use the Linkbelt to keep vibration to a minimum. I am not sure how this fits within your thought. Any input on the Linkbelt?
 
I had an older version of the same lathe and I upgraded to a 1 HP motor when the original 1/2 HP gave up. Funny, the amp load on the 1hp was only 10% more than the older motor. I aske a buddy who designs equipment and was told that they rate motors diffently now and a 1/2 hp of 35 years old is equal to a 3/4 hp today.
I used link belts for vibration and I turned everything I could spin. I turned a 32" platter on the outboard and used the 15 speeds (had a second set of shives) to play with the size of this platter. It was a great lathe and I replaced it with a woodfast bought from Arrowmont.
That lathe still spins wood on regular basis. No problems with the pulleys.
 
If the pulley is a worry, why not just get a steel one and use the larger motor? Long as the mount and bearings will handle the HP, I don't know why it wouldn't work.

Paul
 
Captain - Thanks for the input, I feel better now with a few bench marks for referance. I am going to proceed to mount the drive. Variable speed here I come!
Woodbass
 
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