MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - TF Tachometer Gear Box to Dynamo Peg/Screw

My tachometer stopped working a while back. Eventually got around to working on it today.

The whole gear reduction box had come lose so the original fault was clear to see :-)

On reassembling I noticed that the little screw that interlocks in the slot on the dynamo output was loose. It was still in place because it had screwed out as far as the inner edge of the brass coupling and couldn't come out any further. This also now stopped me taking the coupling mechanism off.

After some head scratching I got the coupling off by prizing open the small brass clamp and was able to push the brass ring down then tighten the screw sufficiently to allow me to slip the brass coupler off.

So far so good. Drop of bearing assembly fluid on the screw to hold in place. Tightened enough such that the inner ring of the brass coupling would just clear the screw head so I could get it back on.

On reassembly it doesn't work. The dynamo drive is going round. I can see that the gear box is working if I take it off and stick a screw driver into the tach cable output and turn it.

The screw/ peg must not be sitting in the slot or big enough to engage. It does seem odd to have something as simple - and fragile as a screw there.

Is this something the PO did ? Is there some secret to this I am missing.

I could do the reverse of what I did on disassembly and this would allow me to loosen the screw out... but that would probably leave it actually loose and feels a bit odd.

Here is a pic of the screw in place.

Dave


D Moore

Yeah. That's not right. It's a tab and not a screw.

Here is a repo picture but the originals are the same.



Christopher Couper

The pinch keyed drive end is missing, it is loose riveted on for free alignment. It reaches deeper into the dyno. Any machinist should be able to make one if nobody has a scrap one to spare.
Ray TF 2884
Ray Lee

I can take mine off and make a drawing of what is required to make one.
Ray
Ray Lee

Just talking to a mate, mine may have been bodged in the past. On his the piece is fastened to the shaft with what looks like the screw in yours. It is free to wobble about and self align.
They tend to wear and come off, check it is not still inside the dynamo drillway, if so a bit of weld will fix it.
Ray
Ray Lee

Just talking to a mate, mine has been bodged in the past.
The piece is loosely held in by the screw you already have. It wears until it come off the shaft and is probably still inside the dynamo drillway (or on the floor under the car). If it is there, a dab of weld and a bit of fettling you are back in business.
Ray
Ray Lee

Talking to a mate and mine has been bodged in the past.
It is held in place by the screw you already have. They wear out and come off the shaft, yours is probably still inside the dynamo drillway or on the floor. A dab of weld and a bit of fettling and you are back in business.
Ray
Ray Lee

Don't know what happened there,it did not appear to send then they all popped up.
Ray
Ray Lee

Well that is the mystery solved anyway. Unfortunately the key is not still in the dynamo or hiding loose in the engine compartment :-(

Pretty sure I can make one.

Ray if you could send me a pick of yours + a drawing of the dimensions that would help cut out a lot of trial and error.

Thanks.

Dave

D Moore

Now it starts to make sense. Found this pic of what I am missing ( not the part with the yellow arrow).

I see how it attaches etc.

Ray - if isn't too much trouble the drawing / dimensions would still be really useful.

In particular the length of the key shaft from where it abuts to the shaft + the length and height of the key itself.
I can then be sure I don't make something that sticks into far or a key that isn't too small to be secure in the slot.

Cheers.

Dave

D Moore

I am going to work on a friends car tomorrow and will measure up. As I said mine has been messed with so better to measure an original one.
Ray
Ray Lee

I thought I'd have a go. Yes I could buy a new fitting and clamp from B&G for £17 + P&P but where it the fun in that.

I started with a 1/4 bolt and a left over flat pack furniture fitting. Needed my angle grinder, bench drill, 1/4 inch tap, some JB Weld and a bit of patience.

Here is my result. The JB Weld ensuring the two parts separating is going off now. Test fit is good. I'll install tomorrow.

Thanks Lee for offer of measurements. I think I am OK :-)

Dave




D Moore

Neat job,
There should be some slackness in the bore so it is free to wobble and not wear out the body of the gearbox.
Ray
Ray Lee

This thread was discussed between 27/03/2021 and 29/03/2021

MG TD TF 1500 index

This thread is from the archives. Join the live MG TD TF 1500 BBS now