The Project Blog

Let’s take it apart

Brook Crompton Motor Repair

March4

R8ZZ BearingThe bearing for the motor on the E2M1.5 vacuum pump came recently and I took a few minutes to put it on. Since it was missing when I bought the pump, I also fabricated a new cover for the cooling fan.

The bad bearing at the front of the motor was marked 7R8Z. I don’t know what the 7 signifies, but a standard R8 bearing matched the dimensions. The R8 bearing has a bore diameter of 1/2″, an outer diameter of 1-1/8″, and a width of 5/16″. I was somewhat perplexed that a British-built all-metric pump would have a British-built motor with parts made in imperial dimensions. Go figure.

Sadly, I forgot to take photos as I disassembled the motor. It is a relatively simple process. At the fan end of the motor, there were two screws that held the entire motor assembly to the mounting plate attached to the pump. The rear bearing of the motor sat snugly in the rear cover, so I used a thin bladed screwdriver to persuade the cover off. I did this with the motor still attached to the pump. The better method would have been to take the motor off of the pump first. I would have then been able to tap the shaft from the pump end and drop the whole armature and end cover out.

Nonetheless, I got the armature free of the end plates and proceeded to work out how to get the front bearing off of its shaft. I gather this is one of the parts that either should never need replacement or requires some special tool to remove. The parts diagram showed no explosion of the motor indicating just how I was to remove the drive shaft that appeared to be attached to the motor. In the photo below, you can see the slotted drive shaft and the smaller motor shaft.

Brook Crompton Motor 01

I thought maybe the drive shaft screwed onto the motor shaft. No amount of torque would budge it. It’s not threaded. I eventually pulled out the propane torch and heated the drive shaft to a dull glow, clamped the cooling fins of the armature in a bench vise and used a punch to drive the shaft off from the back side. It did burr up the edge a bit, but because it won’t be running against any seals, it should be fine. I might have been able to get the shaft off without heating it. Mileage may vary.

Brook Crompton Motor 02

Once the drive shaft was off, the bearing came off rather easily. The new one went back on just as easily after a little 600 grit sandpaper to take off some small burrs on the shaft where I drove the drive shaft off. There is a clip on the motor’s shaft to position the bearing in the right place.

To get the drive shaft back on the motor shaft, I tapped it gently a few times with a plastic faced hammer. I then took a bar clamp and put the fixed against the fan end of the motor shaft and used the screw end to gently push the drive shaft onto the motor shaft.

Brook Crompton Motor 01

After getting it on about halfway, I ran the motor and being very careful to not let it get against the sealing portion of the shaft, I used some 220 grit sandpaper to clean up the edge I burred up driving the drive shaft off. I then used some 600 and a Scotch-Brite pad to polish the entire drive shaft. At this point, I bolted the motor onto the pump chassis. Because I need to be able to get at the end of the drive shaft, I removed the actual pump assembly,

Brook Crompton Motor 03

Because the drive shaft is not fully seated on the motor shaft, it was peeking through too far into the pump. This is exactly the way I wanted it.

Brook Crompton Motor 04

If you recall, the plastic drive coupler between the motor and pump rotors had sheared off partially because the gap between the drive shaft and rotors was too large. In order to get this just right, I wanted to position the drive shaft in situ using the new coupler as a gauge.

I went ahead and pushed the drive shaft flush with the clamp and then used a socket to push it into the hole.

Brook Crompton Motor 05

I pushed a little and checked the coupler. I repeated this about twice before I was happy and then reassembled the pump, filled it with oil and before putting the fan back onto the motor, I chucked the shaft of the motor into a cordless drill and ran the pump slowly to get everything lubricated. I then installed the fan and the cover I’d fabricated earlier.

Brook Crompton Motor 05

The shroud is a 4″ PVC cap with 3 holes drilled into it that match the 3 holes on the motor where the original shroud mounted. I did enlarge and tap the holes in the motor to accommodate the 1/4″x20 cap screws I used. The cap, by the way, is not a Schedule 40 fitting – it is actually sized for use with drainage pipe. The two are sized differently, so watch out for that. You can’t see it in this photo, but I drilled several evenly spaced holes around the center of the fitting for the air inlet. The blades of the fan sling the air outward from the center and the shroud directs it down the side of the motor housing.

On to Part 4: Post-Rebuild Run

posted under Equipment, RepairIt
One Comment to

“Brook Crompton Motor Repair”

  1. On May 27th, 2017 at 4:38 am brookcromptonmotors Says:

    Very Nice Blog
    Thanks for sharing such a good knowledge.

Email will not be published

Website example

Your Comment: