Motor rotation on Sanborn Black Max model B09J500-20

by Fred Parenti
(Morgantown, WV)

My direct drive portable oil free sanborn black max model B09J500-20 has a bad motor, stator windings fried, I'm going to mount a new motor on top of the unit and belt drive to the armature for compressor pump operation.

Can you tell me the proper rotation of this unit?

There is an internal fan mounted to the armature for cooling of pump and motor.

If you are viewing the unit from the motor end, what is the correct motor rotation, or if viewing the unit at the pump end, what is the correct rotation of the compressor pump?

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Feb 19, 2019
Assistance and photos
by: Bill

Hi Fred.

While I do appreciate all your good words, I can't take credit for the good advice. It was all Doug from California, and long time and well respected contributor to this site.

As to getting photos, this system I use is very kludgy and outdated. That's due to change, cut until them, would you mind using the contact page to reach me and I'll get back to you about getting photos for the site.


Feb 19, 2019
Sanborn motor replace
by: Fred Parenti

Hey Bill, I contacted you earlier about my Sanborn, Blackmax and its bad motor. I've made the replacement, it works fine.

I questioned you previously about motor rotation and you said that it should not matter, I've ran it both directions, it pumps the same both directions.

I questioned you about the cooling fan, you stated that you did not see it in any drawings, that fan is located internally in the electric drive motor, it is attached to the motor armature at the coupling end of the motor shaft. I believe that this fan is for electric motor cooling only and since I'm not using that motor no longer, rotation should not matter.

In the installation of the replacement motor on top of the unit I had to use the electric motor casing assembly only. I removed the stator windings, cut an access hole in the motor casing top side for v-belt drive and installation.

I needed the complete motor housing to support the armature at the bearing ends, because now the armature becomes the driven pulley that is connected to the compressor pump assembly. If I can I'll try to send some photos.

I purchased a 3hp compressor motor from Harbor Freight, about $130.00, 220 volt, single phase, 3600 rpm. I used a 2 groove pulley on the motor, probably about 2 inches in diameter, its a little small, but that's what I had laying around. The armature dia. is 2 11/16".

I would like to get closer to 1:1 ratio for correct pump rpm, but I'll need to get a larger drive pulley, right now rpm is at 2500, the unit works ok, but takes a little longer than normal to pump up to desired cut out pressure.

I used 2- 1/2" x 24" v-belts from motor to armature.

I fabricated a pivotal motor mounting plate fastened to the compressor pump housing (top side), for v-belt tension adjustment, I've got the photos on my phone, I've just got to figure how to get them from my phone to you.

I'm still a little "old school", maybe I'll ask my 12 year old granddaughter!

Anyway here's a little bit of the info of "How to replace a bad motor on direct drive oil free portable air compressors".

Pictures are better than words, if I had your phone contact number, I would just text the photos to you, up to you, see-ya, Fred in Morgantown, WV USA

Feb 10, 2019
B09J500-20 rotation
by: Doug in

Normally, the fan or sheave blows air toward the heat source, as a vacuum can't move as much air.

"There is an internal fan mounted to the armature for cooling of pump and motor."

So I'd go with whichever way makes the fan blow toward the heat source, although I don't see a fan on any of the drawings for this unit.

Reciprocating pumps don't care about direction, unless have to pump oil. So no worries there.

Send pix of this thing showing how you do it, please.

Good luck.

(To add photos to this existing post, start a new thread in this same forum, use this same post title and write that the photos are for an existing post with the same title. You can then upload up to four more photos. They will be moved here. Photos can be up to 1.5 MB and a maximum of 800 x 600 px in size. Moderator)

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