Speedo Drive Spacer

Could anyone provide me the dimensions of the Speedo Drive Spacer for my 1970 Commando as it is missing and I have the SST to make a new one. Sure I could buy one but where is the fun in that. if I can get the overall length and the flange thickness I can probably guess the rest.

both my 750 and 850 have spacers 1 5/16 " long, 1" OD and the bore would be sufficient to let the bolt through easily.
Dereck

I am thinking crockett23 is looking for the top hat spacer that fits into the speedo drive gearbox. I have those dimensions, but I cannot get to them for 4 weeks, as I am travelling. PM me if that is the case, and no one else chimes in.

Slick

Flange Dia. 1"
Flange thickness .062"
O.D where it fits in the speedo drive .664"
Length of above .250"
I.D .577"
This is the sizes I get.
Don

Thank you everyone, yes indeed the dimensions of the Top Hat Spacer was what I was looking for. I have it made now from the info. provided so now I can establish the wheel position / offset in the swinging arm and lace my new rim to the hub. Thanks everyone

I had been under the impression that the .250" neck of the top-hat was supposed to run up against the end of the long interior bearing spacer 06-2069, putting the wheel clamping load on that spacer, trapping but not clamping the speedo drive body. After another! speedo drive screw-up, I pulled the wheel and find there is no way the top hat can reach in that far, as the spacer is more than 3/8 from the end of the "distance piece" (spacer NM.18234) which is trapped under the lockring.
When the top hat is placed in the body of the drive, there is only about .160" left, so it's about 1/4" away from the end of the long spacer.
I've ordered new spacers, to see if mine are correct, but now it appears I was on the wrong track all along.
Is the speedo drive body really supposed to be clamped in place as we torque up the axle?

Perhaps your Speedo drive body is "bowed" outwards (the center hole is pushed away from the drive dogs). This happened to mine, and at least one other has reported the same effect on this Forum.

I have no explanation how such bowing occurs, but it can lead to tearing up the wheel hub cover (the thin disc with the holes for the three wheel bolts).

From memory, the thickness of the Speedo gearbox is about 0.82" without the tophat spacer in place. I brought mine back to spec with heat and squeezing in a vise.

HTH

Slick

Thanks, Slick, yes I have seen that bulging as well, but this drive is still "flat".

Are you finding the Speedo drive is scuffing the cover disk?
Is the drive trying to rotate with the wheel?

It has been several years since I rebuilt my rear wheel, so memory should be suspect.
It seems to me, from memory, the locknut clnches up the long spacer. I do not remember how the clamp load is distributed, but it seems from memory, the top hat spacer IS NOT involved. I will be with my Atlas tomorrow, and will have a look. Perhaps someone else can chime in before then and enlighten both of us.

Slick

Thanks again, Slick.
Yes, the drive is (barely) touching the hub cover, although it doesn't touch when first installed!
And yes again, the drive tried to rotate w the wheel, pulling the cable back.
I wish I had the tools to do the Comnoz fix, he seems to have figured it out, although I can't quite picture what he did here:
https://www.accessnorton.com/NortonCommando/speedo-drive.6624/

My original Speedo drive lasted about 85K miles, then rotated and tore up the wheel cover disk.
On disassembly and inspection, I found the ring gear lands to be worn razer thin, and the worm gear would, on occasion, catch the end of one of the ring lands, and rather than the worm rotating, the ring gear and gearbox housing would rotate. Thus, I can say the rotation problem is traceable to worn internal parts.

Many forum members have testified their ring gears fail first. In particular, those who have tried the Indian knock-offs say 3 to 5K miles appears to be the best one can expect from them.

Your drive should be inspected for internal wear. The drives are easily repairable if one can find the parts, but NOS parts are more rare than complete NOS drives. In my case, I was lucky to find a NOS GB, which solved the rotation and scuffing problem.

I reviewed the link you provided. It seems comnoz (1) case hardened his ring gear to get extended life and (2) bored out the center hole and made his own top hat spacer to relieve the pinch on the GB.

I will be at my shop tomorrow, and will review my old GB parts to see if I can shed further light on this.

Slick

BTW .... I am fairly certain, the principal function of the top hat spacer is to center the drive on the axle, rather than transfer clamp force to the drive nut or internal long spacer.

Again, very helpful, Slick.
Spoke w Fred at Old Britt's today, he confirms that the long internal bearing spacer is not taking a clamping load from the top hat, and that the body of the drive is clamped, not just trapped.
Pulling apart my speedo drive, I found it caked with old dry grease. The ring gear also "floats" a little bit. Might just be worn out; I'll see what my "spare" looks like.