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Motor Mount : How to????

dazz

Stainless
Joined
Aug 20, 2006
Location
New Zealand
I want to repower my lathe with a 3-phase motor and a variable speed drive.

I have welded up a four sided base but now I need to make a motor mount. The motor has both a flange mount and a base mount. I would like to make use of the flange for extra rigidity. The mount needs to be hinged along one side. On the other side I need to be able to adjust the height to set the drive belt tension.

I want to use a poly Vee belt so good alignment and rigidity are important.

The photo shows the motor sitting in about the right position over the welded base.

Any suggestions on how to design a good mount for the motor??
 

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Dont bother with the face mount. Just use the feet as they are very rigid.

Make a plate that fits the base of the motor about 1/4" would do. one one end make a hinge. You can use a couple blocks with hole drilled and welded to the bottom side. Put a couple set screws to lock onto the hinge pin. I would go for at least a 1/2" hinge pin, if not 5/8". Drill Holes through your tube frame to accept the hinge pin. Use set screw collars to hold the hinge pin and place.

On the other side for the adjustment there are many ways to do it. You could take a piece of angle iron and drill and tap a hole in one flat. The angle would be welded to the frame so that a bolt screwed through the hole would push down on the belt and provide tension.

Or just mount the motor rigid and measure for the right size belt. install an idler if need be. If you are using multiple belts make sure they are an A or B matched belt. Generic V belts are not matched in size and will fight each other when ran in tandem.
 
A spherical rod-end makes a decent tensioner (or some similar mechanism). Don't get too wacky with the tension at first...you can always add more later. An alternative would be an automotive spring-tensioner installed on the slack side of the belt.
 
Missed one little thing Matt

Lathes often run in Reverse, and a Spring Tensioner will have to take unplanned forces in Reverse. Belt Wrap may also not be optimal... Best to keep it simple like almost all the Original Lathe Makers Did..

Will be using a Heim Joint (Spherical rod-end type Unit) http://en.wikipedia.org/wiki/Rod_end_bearing , when putting a J Head on my M Head Bridgeport to beef up wimpy single Bolt Nod adjustment tho, so it is a very usefull Joint.....,
 
Personally, I'd weld 2 pcs of 1-1/2" x 1" steel to the motor shaft ends of the base. Toss it in a mill and mill out a L shape 1/2" deep in each riser. Take a piece of 1/2" plate, mill it to fit in the slot just created. Drill & tap 4 mounting holes on the 1/2" plate for the motor. Mill 4 slots in the 1/2" plate over the flat in the L of the 1-1/2". Drill & tap 4 holes in the L's of the base.
Make a 1-1/2"w x 1-1/2"t x 1/2" thick block, one hole drilled & tapped in the thickness direction for a 1/2" bolt. 2 holes drilled & tapped in the end to mount to the 1/2" plate. Mount this block to the back edge of the 1/2" plate. A second block as above, but with a thru hole for the 1/2" bolt can be welded to your base frame.
Mount plate to base, mount motor to plate. install belt. Use 1/2" bolt to pull plate/motor combo to tension and tighten the 4 slot bolts.
The L holds motor alignment, slots provide tension adjustment, and allow locking the motor down.
 
Its easy to do shop made "zero clearance" rubber bushed hinge pivots for hinged plate motor mounts. I find these are good for absorbing minor vibrations and can be made to give any desired pivot stiffness from "easy swing" to "heave hard". For modest motor powers such pivots allow motor weight alone to provide adequate belt tension as things don't jump around on start-up which the inevitable clearance and free motion in metal pivots allows.

Construction method is to weld a short length of iron pipe to a suitably long flat or angle iron bar producing a P shape thingy. Its quite practical to make the bar long enough to fit directly on the motor feet but I usually use short stalks and an intermediate plate. Pipe size needs to be chosen so that a piece of thick wall rubber hose is a nice stiff fit inside. I have a stock of 1" nominal iron pipe from salvaged from re-plumbing the house and find thick wall car heater hose is fine for the inner. Its impractical to make the metal tube more than an inch or inch half long 'cos you can't push a sufficiently tight fitting piece of rubber tube through anything longer. Choose or make a pivot bar of a suitable diameter to get the right turning stiffness. Preferably lubricate with red rubber grease on assembly.

If you cut the rubber tube long enough to project 1/8 to 1/4 inch each side you can arrange sideways damping / vibration absorption using suitable washers and spaces.

Another trick for dealing with small vibrations or annoying resonance noise is to mount the motor on a wooden platform and fix the pivot assemblies to that. Forcing rubber tube into holes in 1/2 or 3/4 ply so it stands 1/8 to 1/4 proud each side and using plates or large washers under the bolts is even better.

If real quick and dirty will do large hinges and a lump of wood also works. Quickest motor mount I managed was 10 minutes flat by mounting directly onto a pair of long gate hinges. Done for test purposes only but it never did get changed!

Clive
 
Thanks for the ideas. I have found that freezing rubber makes it easier to stuff into tight places. I don't have a mill so I will have to fabricate the final solution.

I brought a used 150mm (6") muffin fan to replace the fan removed from the back of the motor. I will have to figure out how to mount that as well. I plan to make a tube to support the fan and direct the air flow over the motor. Lack of space probably means I will have to use the lathe to remove the flange from the motor.
 








 
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