BadDog
Stainless
- Joined
- Mar 27, 2006
- Location
- Phoenix, AZ
I'm thinking of converting my 11” Rockwell to direct drive and ditching the Reeves drive. It needs new belts and the sheeves are worn, though not junk. It has the big belt variable drive on the extreme left side of the cabinet, with a jack shaft converting to dual v-belts that drive the spindle at about the center of the cabinet. I won't be starting any time soon as I need 3hp (prefer 5hp) VFD which is not in the budget at the moment, but wanted to start the research process.
Anyway, I found a nice Baldor 3hp but it’s a bit long for my cabinet, in fact it is only a few inches shorter than the max width. But, it will put the pulley right below where the top Reeves drive belt is/was (ie. about 2” from the left side of the cabinet), and that is with the motor almost touching the cabinet on the right side! This seems to be a very nice “Inverter Duty” (so says the sticker) motor and should be ideal I think, given that the OEM motor was 1hp and swing is only 11”.
So I'll still be using the original jack shaft to get the v-belts lined up with the spindle pulleys. I already rebuilt it with new shaft and bushings, and the brackets/alignment/adjustment is already built in. I’ll simply replace the Reeves Drive wide pulley with another belt system going straight up from the motor. That allows me to choose any pulleys at my convenience and avoid the issue of building a bunch of stuff and dealing with the offset spindle pulleys.
For main drive pulleys, I’m thinking I may just use a single automotive serpentine in 1:1 ratio on moderately large pulleys (6” dia?). That gives me relatively cheap and smooth running belts that are very strong and long lasting, along with common and easy to find pulleys, albeit needing adapting to fit the shafts.
That would let my 1750 rpm motor drive the spindle at 1750 rpm at 60hz. The motor is rated “inverter duty”, so should withstand maybe 15-20 hz on the low end for 525 low rpm in direct drive, and 250 rpm over the stock maximum (1500 rpm) at 60hz. Then again, a slight under drive would let me hit that ~500 rpm (or a bit lower, I may shoot for 400? on the low end?) without going so low on freq, and most folks agree that 3ph motors can run fine for moderate duty cycles at up to 200% (i.e. 3000+rpm) so I would still have more rpms in the motor than the spindle could ever stand. For the low freq, low rpm stuff, it will need an aux cooling fan if you want to go below 30 hz, but that’s not a problem I think, particularly if I gear it lower than 1:1 so I don’t underdrive the motor as much or as frequently...
So, how does this sound? Have I understood all the aspects correctly? Any suggestions on VFDs? I don’t need much except variable freq and 1ph 220V input, so I think most any cheap VFD should work. And it seems I can use a 3 hp 1ph rated, or a 5 hp 3ph rated VFD only wiring L1 and L2 on the inputs. So that’s what I should be looking for on EBay etc. Anything else? Comments?
Anyway, I found a nice Baldor 3hp but it’s a bit long for my cabinet, in fact it is only a few inches shorter than the max width. But, it will put the pulley right below where the top Reeves drive belt is/was (ie. about 2” from the left side of the cabinet), and that is with the motor almost touching the cabinet on the right side! This seems to be a very nice “Inverter Duty” (so says the sticker) motor and should be ideal I think, given that the OEM motor was 1hp and swing is only 11”.
So I'll still be using the original jack shaft to get the v-belts lined up with the spindle pulleys. I already rebuilt it with new shaft and bushings, and the brackets/alignment/adjustment is already built in. I’ll simply replace the Reeves Drive wide pulley with another belt system going straight up from the motor. That allows me to choose any pulleys at my convenience and avoid the issue of building a bunch of stuff and dealing with the offset spindle pulleys.
For main drive pulleys, I’m thinking I may just use a single automotive serpentine in 1:1 ratio on moderately large pulleys (6” dia?). That gives me relatively cheap and smooth running belts that are very strong and long lasting, along with common and easy to find pulleys, albeit needing adapting to fit the shafts.
That would let my 1750 rpm motor drive the spindle at 1750 rpm at 60hz. The motor is rated “inverter duty”, so should withstand maybe 15-20 hz on the low end for 525 low rpm in direct drive, and 250 rpm over the stock maximum (1500 rpm) at 60hz. Then again, a slight under drive would let me hit that ~500 rpm (or a bit lower, I may shoot for 400? on the low end?) without going so low on freq, and most folks agree that 3ph motors can run fine for moderate duty cycles at up to 200% (i.e. 3000+rpm) so I would still have more rpms in the motor than the spindle could ever stand. For the low freq, low rpm stuff, it will need an aux cooling fan if you want to go below 30 hz, but that’s not a problem I think, particularly if I gear it lower than 1:1 so I don’t underdrive the motor as much or as frequently...
So, how does this sound? Have I understood all the aspects correctly? Any suggestions on VFDs? I don’t need much except variable freq and 1ph 220V input, so I think most any cheap VFD should work. And it seems I can use a 3 hp 1ph rated, or a 5 hp 3ph rated VFD only wiring L1 and L2 on the inputs. So that’s what I should be looking for on EBay etc. Anything else? Comments?