How would you mount this heavy motor?

[®smpr_fi_mac®]

I'm hanging a motor under my jointer. The motor weighs 84#; it's a 184T frame. My concern is with setting the tension on the belts properly. Bearings on the cutter head are sealed self aligning; I'm not worried about stressing babbitt.

My current plan (open to modification) is to use heavy steel L brackets, bolted to the sides of the jointer, with doubled-up 3/4" ply running between the two. The gap is about 14".

Now then, should I just bolt the motor directly to the plywood as is, or should I bolt it to a second piece that is connected to the first with heavy duty hinges? This way, the weight of the motor can tension the two belts running between the two pulleys.

My PM100 planer is set up something like this, and it had a 184 frame motor before I replaced it with a 145T.

Thoughts?

[MarkSingleton]

Sounds reasonable to me. Plenty of motors are
set up that way and no problems.

[DFJarvie]

Surplus Center sells a plate that you can mount the motor to and will allow the motor to tension the belts. I used one on my jointer.

[Splinter Puller]

Surplus Center sells a plate that you can mount the motor to and will allow the motor to tension the belts. I used one on my jointer.

And... you can use a spring to lighten the weight on the bearings yet still tension the belts.

[daddo]

Depending on the distance between pulley centers, that weight may be too much for the right tension on the belt. I agree with having a way to properly tension the belt. Belts don't really need to be very tight for medium loads if the belt goes at least half way around the pulley.
Spring or tension bolt- or both.

[®smpr_fi_mac®]

The motor will only be about two feet or so below the driven pulley on the cutter. It'll be close to directly below, if that matters.

If I am to use something to lessen the weight supported by the belts, I'll have to engineer something; maybe a threaded rod running vertically from the jointer, through the motor's mounting plate, with a nut under the plate for adjustment?

Or even put the threaded rod in a base that's on the floor under the motor--this jointer weighs 900#. It isn't going anywhere.

[MstrCarpenter]

You said you're "hanging" the motor, and you think it's too heavy. I don't think pulling it up with springs or lifting from the bottom is the best approach. I think it's better if don't put any dead weight on the belts. The pivot allows belt tension adjustment similar to the slots on the motor base but instead of tightening the bolts you would lock it in place with an adjuster on the opposite side of the motor near the drive end. This will maintain the belt tension you select and also keeps the motor from climbing the belt at start-up and when a load is introduced. I've worked with old (really heavy) 10hp 3ph motors where the belt adjustment consisted of adding or subtracting slotted shim washers under the motor base before tightening the bolts. It was a pain. Most were changed to longer bolts that bottomed out with two nuts, two washers and a new lock washer. This made it much easier to get the same tension on the three (supposedly) matched set of belts.

[TDKPE]

<snip>  Most were changed to longer bolts that bottomed out with two nuts, two washers and a new lock washer. This made it much easier to get the same tension on the three (supposedly) matched set of belts.

That's how I mounted the motor on my lathe - long bolts, with rubber grommets above and below the mounting foot, and adjusted to set belt tension.  The grommets provide some resilience for belt imperfections, but mostly they allow some controlled pre-tensioning while allowing me to jump the belt between grooves without loosening anything.

One thing I've found over the decades when playing around with different motors on my lathe is that a hinged mount will, of course, put a twisting load on the mount.  That's fine for a stiff steel mounting system like on a contractor saw, but home built wooden mounts don't much like that and tend to allow the motor to angle a bit, putting the motor sheave out of plane with the driven sheave.  And they can bounce.  The dynamics can be unpredictable, so trial and error is the best I could do until I changed it to a more stable (non-hinged) arrangement.  If hinged, I would definitely use a bit of allthread to adjust the tension AND to stabilize the motor.  Two pieces would be better - one at the shaft end, and the other at the opposite end, or at least build in the capability to add a second if needed to keep the motor shaft parallel with the machine shaft.

As daddo correctly stated, you don't need much tension on a v-belt (usually), depending on the sheave size, speed, and power being transmitted.  I run my Unisaw belts sloppy loose to keep vibration away, and never have an issue when working it hard.  But small sheaves running slow with a heavy load, like the motor sheave on a BS, may need more tension to keep from slipping.  Or larger sheaves.  But if it's not slipping, it's good. 


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[®smpr_fi_mac®]

"Hanging the motor": mounting it under the jointer, base pointing up.

It won't be dead weight on the belts.

I don't think it's too heavy. I'm concerned that it might be too heavy to simply hang it on a hinged platform. I don't know whether it's too heavy or not.

This is why I'm asking.

I don't have a method for locking the motor in place so I'm trying to figure out a method to do this, hence the thought of somehow running a threaded rod through the base holding the motor and securing the other end of the rod either to the underside of the jointer or to the floor.

I don't have the ability or tooling to figure out a way to lock the motor on the non-driving side.

[®smpr_fi_mac®]

I have no problem with using angle iron to support the motor (instead of wood), which should eliminate any twist, right?