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MG TD TF 1500 - threaded segment for tach. reduct. gbox TDor TD

Good day all:

Once again I submit an oddity for much needed information.

I have a Dynamo CE Bracket (or Plate) equipped with the threaded Oiler hole but sans the extended end piece which is threaded to accept the Tachometer Reduction Gearbox fitting. The bracket, if bearing the above mentioned bit, would be suitable for use with a TC Dynamo.

I, at first, reckoned the threaded piece to be a pressed in item, but have since been informed that it is not.

However; the same source recalled hearing about someone who was making this bit, as a pressed in fitting, which I suspect, to repair those that had been cracked or otherwise broken.

The threaded couplings are the same for the TC and the TD CE Brackets, so I was wondering if anyone out there could shed some light on the subject.

That is, who this person may be and failing that what the group thoughts may be on the feasibility of having a machinist tackle the chore.

Cheers then; respectfully:
Jack Emdall, Halfmoon Bay, British Columbia, Canada
kernow

Jack - It would be very difficult to make a press in fitting to accommodate the tach reduction gear box. First, the armature has to have the extended shaft that is drilled and slotted to accept the mating piece from the gearbox. Additionally there is a bushing that takes up a good portion of the extension on the CE. That said, I would not totally rule out what a good, cleaver machinist can do if the rest of the required parts are available (that is why I advocate that when one finds a good machinist - treat him/her very well - they are worth their weight in gold). Cheers - Dave
David DuBois

Assuming you have the proper (extended) rotor then, depending on what the end plate or bracket you have looks like you might be able to do something.
Here is Dave B's
http://www.dbraun99.com/mgtd15470/Electrical/Starter%20%26%20Generator/slides/finished%20generator.html

The issue, as Dave DeB noted is the rear bearing.
If I were doing this, and generally I do anything, I would press out the rear bearing,
Make an extension, TIG wield it on, (actually I would have my friend Don Ecles weld it on, my TIG does not do aluminum)and then reinstall the bearing.

Its not a trivial modification but it can be done.

Jim B.
JA Benjamin

For what it's worth, here's a picture of the end plate. It appears on close inspection that it is all cast and then the nose is threaded.

Jud

J K Chapin

Good day again all:

Again I beg your indulgence regarding a matter that on the surface seems to be only TC related. But, its solving could lead to the salvaging of a damaged TD Dynamo CE Bracket as well. (I have one of those with a piece cracked out of its threaded extension to work on also).

Thank you for your insight Dave. I have already had a machinist thread an extension piece, into the armature shaft, which has been designed to accommodate the tachometer cable. This item was obtained from Mr. Joe Curto and as a result of his fix, the armature is now correct for a TC Dynamo.

Therefore; it is solely the TC Dynamo CE Bracket that remains my problem.

I do have a Pre WW II Three Brush CE Bracket and have thought of "jury rigging" it by eliminating the third brush location, but I am hesitant at destroying a part which may be sought after by someone else. Especially as these items have now become as rare as rocking horse dung !

I have suggested to another group, in the past, an offer to trade for a TC Bracket or even to make an outright purchase but sadly they too appear to have gone the way of the dinosaur.

Failing a trade or direct purchase, I will resort to my machinist friend, and hope for the best.

Cheers once more lads; respectfully:
Emdall
kernow

By-the-by all, the Bracket in question is cast iron not aluminium.

Cheers again:
Emdall
kernow

Right then:

Firstly; Probability of machining an insert glum.

Secondly: Can someone set me straight as to the thread used for the extension.

The nearest I can find, using my gauge, but then I am a bit thick, is 1mm.

However; with my luck it will most likely turn out to be some relatively obscure variety such as British Railway, motorcycle or worse yet, a thread designed specifically for the sole use of Smith's of Cricklewood.

If someone out there is in the know please enlighten me !

Respectfully:
Emdall
kernow

A year or so ago I made a new knurled nut for the tachometer gear box.
My drawing says 3/4-26.
Now 1 mm is 25.4 and I checked the threads I made, on my second prototype, with a metric thread gage and 1 mm fits fine.
So If you have a metric lathe you should be able to do 1mm pitch. If you have an imperial lathe 26 TPI works fine.


Jim B.

JA Benjamin

Thank you Jim I did find my 26 G thread gauge which seems to fit fine so I'll go with the 26 tPI.

Cheers mate:
Jack Emdall
kernow

The thread is most likely British Standard Brass.
In this all diameters use the same fine thread, 26 tpi,
and I think the same Whitworth thread form, not the 60 degrees of US and Metric threads.

Taps and dies are available for this standard.
Don Harmer

>and I think the same Whitworth thread form, not the 60 degrees of US and Metric threads.

Yes as Don noted I did use 55 degree threading tools while making this.

Jim B.
JA Benjamin

Would 55 degree vs. 60 degree thread explain why the knurled cap that screws so smoothly and easily on my old ginny is such a hard to turn fit on the ginny (repro?) that I just bought?

Jud
J K Chapin

This thread was discussed between 11/09/2013 and 13/09/2013

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