Overdrive speedo angle drive

[daverclasper]

Hi. Finally around to dismantling mine and knocked out the ferule?/broken cable bit out of large pinion. Not confident to try a repair.

So will look out for a Smith unit secondhand.

A few questions please.

Would a Smiths require the washer (or would it do any harm) as I understand BL used copies in production at some point so may be when the bulletin info came in (above is dated 68)?.

I assumed the washer fits inside the knurled locking ring on the A/D to put extra distance between A/D and the threaded adapter (and therefore the O/D pinion) the ring screws onto, though the washer pictured on the bulletin looks too large for that (maybe not to scale).

Also some Smiths are advertised for MGB. Have been told these will fit Triumph. I guess any differences on this Smiths model,  would be down to different sized square end of speedo cable?. 

Any other make of car that would be compatible, does anyone know?.

Any help great please.

thanks, Dave 

   

[Pete Lewis]

Originallymade by smiths, its used on many many makes 

Even a  simple search on sites like rimmers for angle drive brings up a whole plethora of alternative model fitments

Even on ebay most show the washer ,really  any washer with a 7/16" hole that fits inside is fine ,

If in doubt fit two better thann none, fibre , copper, whatever

Pete

[daverclasper]

Hi

Picked up a second hand Smiths for a tenner off E Bay, so chuffed.

It was pretty free moving, though ran some oil into it through that little screw hole (ideally would liked to have cleaned/greased it, though it seemed a shame to take it apart (as drilled small holes in the end plates to hook them out on the old one).

fitted a washer even though a Smiths.

So working speedo again.

Thanks for your help everyone.

Cheers, Dave

 

[daverclasper]

Hi

Picked up a second hand Smiths for a tenner off E Bay, so chuffed.

It was pretty free moving, though ran some oil into it through that little screw hole (ideally would liked to have cleaned/greased it, though it seemed a shame to take it apart (as drilled small holes in the end plates to hook them out on the old one).

fitted a washer even though a Smiths.

So working speedo again.

Thanks for your help everyone.

Cheers, Dave

 

[Adrian Cooper]

I had another angle drive fail on Tuesday which makes 3 in 14 months. It is not just the expense that annoys me but the job of taking out the gearbox tunnel is only second to replacing the differential in the rank of irksome things to do with your Spitfire. Each time I have bought a new drive cable too and replaced the speedo with on that I know to be good, and yes, I fit the copper washer. Each failure follows the same pattern; a long, fast run on a hot day and all is fine until I stop, then when I restart the speedo has failed. No strange noises or swooping needles. 

Inspired by Clive's post I decided to have the back off one of the broken drives to see what had broken and if I could fix it. All 3 had suffered the same failure point that Clive mentions where the square drive pin just spins in its ferule rather than transmitting the drive to the gears (which were in perfect, smooth running condition) In this first picture you can see the offending part  which is actually in three bits, the gear wheel, the ferule that runs through it and the square drive pin. You can see the end of the drive pin poking out of the ferule and I assume that the ferule is designed to grip the  drive pin when it is pressed into the toothed wheel. In the original Smiths angle drives the hole through the centre of the ferule was threaded, rather like the rifling on a gun barrel, so that it gripped the drive pin which is made from twisted steel strands. These new, crap repro parts don't have this and this is the root of the problem. My guess is that the heat from the gearbox makes the different metals expand at different rates and so lose their grip on each other and once they have started slipping there is no way that it will ever grip again. What really surprises me is that it worked for as long as it did.

Following Clive's instructions I removed the pin from the ferule. I tried to drill it out but , even using a pillar drill, the bit kept wandering off the steel wires of the drive pin and cutting into the softer metal of the ferule. So I gripped the pin in the vice and carefully levered the ferule away from it. Be careful with the ferule as it is very soft and it will not run well in its bearing if it is deformed in any way.

I didn't want to try to reuse the pin so I found one of the old speedo drive cables and thoroughly degreased it and the ferule. I used Araldite to glue the pin into the ferule making sure that it protruded 20mm from the front of the drive, like the original. When the glue had dried I used a Dremel type device to cut off the rest of the cable and I filed the cut end flat, finishing it off on an oil stone as this surface runs against a domed washer under the cir-clipped end cap.

Final reassembly with plenty of fresh grease and time to refit it. Higher up this thread Uncle Pete had suggested, perhaps jokingly, that it would be a good idea to make an access hatch in the gearbox tunnel and this is what I did, not because I don't have faith in this repair but because I hate taking the tunnel out so much. Worked like a charm Pete!

 

I went for a long test drive today and everything seems fine. Thank you Clive!

Adrian

 

[Pete Lewis]

Thats brilliant, ive got a failed one in  a  bag ,   used it on twiddle day,  so must try a rebuild,  the 2000 doesnt use one , im lucky there

Just to reply we have a local herald we added a D tpye and direct drive cable through a grommet and hole in the tunnel fed the cable under the carpet and its worked ok for some years now

Pete

 

[Clive]

Glad it worked! I have done 6-10 like this over the years, I probably do every one differently. 

Copious old cables helped, but not many left now. And I think mig is the way forward rather than epoxy, but epoxy has worked for me. Think I scuffed the hole the "new" Pin first, and I have always used a 4 1/2" grinder for all cutting etc. Obviously I am a barbarian.

On a different note, I had heard some of the recent angle drives are doing rather better, but that is hearsay. Not sure if anybody can confirm.