What's new
What's new

Electric Motor Shaft Alignment and Motor Mounting

Ckiernan

Plastic
Joined
Jan 25, 2018
I'm building a rotary phase converter and am coupling a 3/4 hp motor to a 15hp motor to get it up to speed before applying power to the bigger motor. I'm using a lovejoy coupler and need to build a platform for the pony motor that would be suitable for making alignment adjustments in all three planes. Anyone have any suggestions on how to fabricate a simple motor mount and how thick the material should be for this application? I was thinking of making the pony mount out of 18 ga. steel with reinforcing bends that are welded in the corners for rigidity. LoveJoy states that I need to be within 1 degree of angular alignment and .015 of parallel alignment.
Any thoughts on this construction?
Thanks,
-Carey
 
Last edited:
Go the belt drive route. You don't need to get the pony motor up to full speed of the RPC motor. Just enough RPM's to get the main motor going, which is about half the full run RPM.

Not too sure 3/4 HP will power up a 10 HP motor to full RPM.
 
Use a single mounting plate for the two motors. Construct an elevated platform on the base plate to achieve vertical alignment between the two shafts. Mount the larger motor, attach the coupler halves and slide the small motor into position. You can eyeball the angular alignment and probably get close enough, but it is easy to check by laying a long straightedge lengthwise atop the two. Then mark and drill for the pony motor bolts. You don't need any adjustment when a lovejoy is properly applied.
 
You might try a wood splitter pump to engine mount and modify it. It would help if both motors were c frame. They are available from Surplus Center. On foot mounted motors a common base with riser block for smaller motor would work. Leave the riser slightly lower than calculation for shimming if you want to dial it in. You will need a substantial base for a 15 hp motor, at least 3/16 channel shape, so just extend it.
 
1/8 hp motor will easily spin up a 5 hp idler motor. Alignment issues trivial:

Conv.jpg


Suspect the ultra-precise lovejoy coupling plan is a solution in search of a problem.
 
Go the belt drive route. You don't need to get the pony motor up to full speed of the RPC motor. Just enough RPM's to get the main motor going, which is about half the full run RPM.

Not too sure 3/4 HP will power up a 10 HP motor to full RPM.
Thanks for getting back to me, the 3/4 will spin up the 10HP motor just fine and since its a short duty cycle, it never gets over heated.
 
Belt drive.
BilLD
Hi, Thanks for the comment, The reason I'm going with the inline coupling is for space purposes, It keeps the profile simple and it fits in its intended space perfectly while still having excellent ventilation
 
1/8 hp motor will easily spin up a 5 hp idler motor. Alignment issues trivial:

Conv.jpg


Suspect the ultra-precise lovejoy coupling plan is a solution in search of a problem.
I've been involved in industrial automation projects for many years and the reason why shaft alignment is so important is it makes for smoother operation, reduces bearing wear and extends the life of the coupling. The beauty of the LoveJoy coupling is that alignment only needs to be within 1 degree of angular and .015" of parallel alignment. I've never done it myself, hence I'm here looking for how-to advice.
 
18 ga. seems pretty thin. I'd go thicker, like 1/4. If you go the lovejoy route, the better the alignment tge quieter.
Use a single mounting plate for the two motors. Construct an elevated platform on the base plate to achieve vertical alignment between the two shafts. Mount the larger motor, attach the coupler halves and slide the small motor into position. You can eyeball the angular alignment and probably get close enough, but it is easy to check by laying a long straightedge lengthwise atop the two. Then mark and drill for the pony motor bolts. You don't need any adjustment when a lovejoy is properly applied.
Appreciate the reply, I'm using the base plate from an old air compressor as my mounting plate and since the foot mount of the pony motor is 16 ga. steel and there is not much continuous torque on this motor, I decided on 18 ga for the pony pedestal (and I had it laying around). Here's what the whole rig looks like.
 

Attachments

  • RotPhaseConv1.jpg
    RotPhaseConv1.jpg
    199.6 KB · Views: 32
Looks great! RPC noise can be extremely annoying. You might consider rubber isolation mounts between the main plate and the caster pads.
 
Last edited:
Or, big rubber stoppers between the 2X4s and the bottom of the crawl space!

(that 15 hp motor is probably a LOT bigger than 3X the size of my 5 hp one!)
 
Looks great! RPC noise can be extremely annoying. You might consider rubber isolation mounts between the main plate and the caster pads.
I'll probably add vibration mounts to dampen latent vibration on the whole unit. I'm concerned that if I add rubber mounts to the motors, it will mess with the shaft alignment. I managed to get the alignment set up fairly well with only minimal occasional vibration using a 6" straight edge to get the angular and parallel measurements. The 15hp shaft coupling is machined slightly oversized and needed to be shimmed .015 to get it to run concentric. Probably keep an eye out on FleaBay for a L-110 - 1.625" bore Lovejoy and swap it out.
I think I have it to the point where I can start tuning the RPC with capacitors which will be something like 200mf across the A-C lines and 150mf across the B-C lines and add a Nema size 2 contactor, mount it all in an enclosure and bolt it to the backside of the unit. This should give me enough 3-phase power to run all the machines in the shop with the exception of my compressor which is a 10HP Kellogg American K452. That's already fitted with a VFD.
 
Last edited:
Ok. Looking at the pic I thought you were going to make it a 'roll-around'. For sure no flexible mounts on the coupled motors. McMaster has some spiffy isolators graded for various weights. 'Tuned' with the caps it will be quieter too.

I made my first RPC and it worked, but was pretty noisy. Bought the present one from American Rotary and it has been flawless for near 12 years of heavy use. Even though this one is much quieter than my home-brew I still mounted the motor in another room with the compressor and kept the box in the shop. Very quiet!
 








 
Back
Top