25 Start/ Generator Motor

My 25 Buick when it was running its best it still always had a slight miss at idle.When I had the floorboard out the other day I noticed a lot of arking going on in the start generator motor.

This was down inside around where the starter plunger shaft goes in to it.I am now wondering if this could be the miss I am Experiencing.

carmover, the arm that raises and lowers the starter and generator brushes has an insulator at the end. These often become cracked or broken which will cause earthing or sparking. You can see the insulator at the bottom of pic 2 where the arm is connected to the starter brush. I don,t know if this would cause a miss at idle.

I believe thats where it looked like it was arking.That should be pretty easy to fix.I am going to rewire the car and rebuild the switch after The carb issues get resolved.I appreciate the pics and info Rod!

My SG motor has the same problem and I have been thinking thru the options for replacement.

This photo shows the end of the SG motor pulled back and rotated to expose the crank arm. The insulated grooved bushing is broken in half.

After removing the crank arm, its obvious there are 2 insulated rollers attached to this arm that need replacing. First is the grooved bushing, second is an oval roller. This crank arm is made from brass or bronze, and pivots on a brass pin, so it apparently carrying a lot of current when the starter is engaged. Easy replacement of these 2 insulated rollers was not factored into the design at Delco. The grooved bushing is held by a steel pin pressed thru the crank arm and peened over on the back side. The oval roller is mounted over a shaft machined into the brass crank and held in place by a small nib of brass peened over a retaining washer.

I had some flat stock nylon material that appears suitable for replacing the oval roller. This I rough cut into near round shape with the bandsaw, mounted on a quickie arbor made from 1/4 threaded stock, and lathe turned into a round with the larger diameter of the original oval roller. From here all it needs is a little belt sanding on 2 sides to make an oval shape. This same nylon should work well for the grooved bushing, but it would be much simpler to turn that piece from round stock of sufficient length to safely mount in the lathe chuck. I may have to make a smaller arbor because 1/4 is too large.

Now... how to replace parts that were originally peened into place:

For the grooved bushing: I can turn a steel pin exactly like the original, then grind away the peened portion of the original and knock it out with a punch. The new steel pin and slotted bushing will be installed and peened over just like the original.

For the oval roller: split the old roller and remove it, then carefully cut the steel washer away to expose the mushroomed brass nib. with a hammer, anvil and flat punch, reform the nib. (and hope the brass hasn't work hardened too much to re-peen) if all goes as planned, the new oval roller will drop into place on the machined shaft, a new steel washer fits over the brass nib, and peen the brass nib over the washer.

I haven't finished this yet. Is this the same approach that others have taken for replacement of these parts ?

What is the best way to insulate those old wires poking out of the windings ?

Kevin

BCA # 47712

Kevin, That oval roller is meant to be round, it rolls on the starter shaft which raises and lowers the s/g brushes when you push on the starter pedal. the old rubber ones develop flat spots if they don,t turn. I put new wiring in my s/g or you could just wind insulation tape around it, as was done in the pic in #2

Rod

Kevin

I just replaced the roller on the stater brush on my 1925 starter generator with a piece on GaroliteXX from McMaster Carr. I filed the brass away from the washer till the washer came off. Drilled a 1/2 inch deep hole in the center with an 1/8 inch drill bit. Cut a piece of the GaroliteXX tube, finished to size in the lathe, reinstalled on the brush holder with a small metal tapping screw and the original washer. The original material appeared to be Bakelite and the GaroliteXX is the modern equivalent. I would consider the temperature range of the nylon material you mentioned. I have plenty of the correct size GaroliteXX that I would be happy to send to you. Fortunately the other insulators on my unit were in excellent condition.

Jim Bourque

After completely disassembling the SG motor, I noticed the End Frame assembly does not mate up to the SG bolt pattern. I will use the name End Frame because the 1924 Parts Book lists it as: D-15861 End Frame assembly for commutator end of motor generator.

There are 3 bolts which attach End Frame to the SG body, and the center hole does not line up, but is off by approx 1 inch. This End Frame has been braze repaired to reattach the lower mounting ear. My father most likely did this repair after he found the SG at a swap meet, so the ear had been broken off long ago. A possible explanation for the break is the original End Frame was worn or damaged, and someone obtained this End Frame for a replacement. It was not an interchangeable part; the center attach bolt could not be installed, and the small ear was broken off during starting due to heavy side load created when the starter is engaged and cranking the motor, and 2 bolts was not sufficient to hold the End Frame in place. I fear that if try to use this End Frame on the SG, its just going to break off again during starting.

braze repair to mounting ear and misalignment of center hole

this End Frame configuration is correct for 1924-1925 Master. (not mine)

Front view of my SG housing

1924 parts book plate 10 & 12

my distributer and SG distributer housing. casting number on housing is identical to Parts Book plate 12 above

does anyone have the correct End Frame that will fit my MG unit ? I don't know if the correct End Frame will have the casting number 15861, or if that is the subassembly number. The other parts in my SG motor appear to be in good usable condition, so I don't need a complete replacement.

Kevin

BCA # 47712

Kevin

I have one for you. Is that all you need?

Jim Bourque

Thanks Jim

I believe that's all I need, but I should check out the cover plate too and see if its the correct part. its #D-15819 in the above photo from Buick Parts book plate 12. something looks odd about mine, but I didn't get a photo of it. I will check this weekend.

Kevin

1924 Masters parts number are D-15861, and 1925 Masters parts number are D-17280.

Leif in Sweden.

Kevin

Attached pictures are of the S/G end cover I have for you and my cover. Sorry I don't have a spare cover, one of the few parts I don't have a spare for.....

Let me know what else you might need and I will see if I have a spare

Jim Bourque

Last picture shows casting number of the cover, don't know the part number

Jim

your End Frame looks like the picture from the Buick Parts book plate 10 above, and should be correct for my SG motor. The commutator brackets from mine should hopefully fit it. Aside from the smaller cover plate my SG motor, the other parts I have look correct.

I was able to make a positive identification of my SG unit from the casting number 33966 on the body; its a 1924

this is the small cover plate. someone sawed off a piece to get the cover to fit over a stout battery cable.

I will send you a PM.

Kevin

BCA # 47712

Kevin

The 24 and 25 Masters both used the same 268 Delco S/G.

Jim

I completed the insulated roller installation on the brush lifter crank arm using the nylon material. After splitting the large roller into pieces (it was made of rubber), I grabbed the small washer with pliers and peeled it up and off the small brass nib. The washer was not damaged and was easily flattened out for re-install. Using a flat punch and small anvil, it was easy to reduce the peened end of the brass nib down to a smaller diameter until the washer would drop over it. The new roller and old washer went back on, and I peened the nib back over the old washer. I recently purchased a cutoff tool for the lathe, and used it to cut a clean groove with the right width for the smaller roller that lifts the generator brush. Instead of turning a new steel pin for this roller, I ground the head diameter of the old one down until the new roller would fit on the pin. To retain the roller I welded a small washer on the end of the steel pin, making sure the roller turned freely. Both rollers can be removed and replaced again using the same process. I am considering using the GaroliteXX material to turn a second grooved roller to replace the nylon roller. The retaining weld is pretty small, and should be pretty easy to grind away.

Kevin