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Pesky Right-Angled Drives


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In this topic on the 4A forum someone has the usual problem with speedo-drive:

http://www.tr-register.co.uk/forums/index.php?/topic/47892-speedometer-cable-question

 

This generated a PM asking if I repair drives. Well mines good, so I have never done one.

So I replied that I'd have a go and even if I failed it would make an interesting Forum topic.

 

Four arrived this morning and all had defective wire stubs, the sticky out bit that mates to the OD.

There were two original ones, a Bastuck and an unknown.

 

I am most interested in the original ones so this evening I dismantled one. took about an hour.

The next one will take 15 mins. It helps so much when you know what's inside.

 

Tomorrow I will do the photos and you will all know. All I will say is that you can forget about the gears in these failing. They are superb precision parts, which should not just get thrown away.

 

I have loads of special workshop tooling but anyone could dismante one of these, substituting patience for special tools.

 

Now what I need is something to make the new wire-stubs.

 

Anyone got an broken inner wire from a speedo-cable?

 

By the way, thanks Niall! You should get some working ones out of this.

 

 

 

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Alan.

I can supply some inner cable, I have modified these in the past, & the problem you find is that once you cut them, or grind extra

metal from the sides of the square ends they tend to unravel. The solution for this is to add braze, or silver solder into the ends before you cut / grind to a new shape. You will have to do this if you are going to produce some short cables for angle drives, anyway I will send a PM with my email address, & we can discuss sending the cable offcuts to you.

 

Bob.

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Hi Alan,

should be interesting how you get on. I repaired mine many years ago using a spitfire speedo cable.

This appeared to fit better than a TR cable but my comparison was very basic and they may be identical.

 

Cut off the required length and force into the cavity made by removing the old stub end.

 

Roger

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I've been thinking these may need silver-solder. But this will de-temper the wire.

 

The ends will end up being "solid" and with luck there will still be a "springy-bit" left in the middle.

 

I wondered what would happen if you just used a solid rod. Suppose the flexing will break it.

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My current speedo cable is a normal TR3 one (RHD + O/D) but modified to fit into a T2.5PI speedo unit (fitted inside my TR casing)

I had to change the securing "nut", & the termination sleeve on the outer, & for the inner had to change the nylon part for a stepped brass part.

Also the T2.5 inner cable is of a slightly smaller dia, & as such the TR inner would not fit into the speedo - hence the need for grinding down the square, & silver soldering to hold it all together.

 

Bob.

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Here is an original drive, made by Smiths, TR4A vintage:

https://flic.kr/p/orc8fE

 

I have been able to get the end plates out by just nicking the peenings with an end-mill.

There is vitually no damage and the housing is serviceable.

 

laid out in the order they fit together:

https://flic.kr/p/otdZQH

Note the top-hat washers, that control end-float, have flat faces.

They show a perfectly circular witness mark from the gear rotation.

 

There is negligible wear on the bronze bearing bushes or the gears.

Note the size of the ferrule that holds the wire-stub. This is a good interference fit in the gear.

 

This is the oldest and has probably done 100K miles. Given a new wire stub it will do another 100K.

Pity about the attention from Mole grips on the brass nut.

 

Here is an item of unknown make:

https://flic.kr/p/otct7s

 

This is a very close copy. Possibly this is also an original item, from the "Leyland" period.

The gears would interchange with the Smiths.

 

But the ferrule is poor and invites slipping. And the top-hat washers are not flat so the witness marks are small.

Control of end-float is important in a drive like this, as we shall see later.

 

On the face of it Circlips are a good thing. But the small one is tricky to get out.

This one is newer, not quite so well made, but will be as serviceable as the Smiths with a new wire.

 

Now we come to Bastuck, this is recent manufacture:

https://flic.kr/p/otdZJv

 

Looks OK huh! Even still has its wire-stub intact! Does not work, of course. It should go in the bin really.

There are so many problems with this poor thing, that it will get its own post!!

Edited by AlanT
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Had samples made by this company in the 1990's. One sample is still running on my brothers TR.

 

http://www.veethree.com/right-angle-drives.html

 

The item was larger and very substantial compared to the orig Smiths item.

 

Cheers

Peter W

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Mine has been repaired with a suitable length of Allen key -so long ago I can't remember the size but it's now done quite a few thousand miles.

Cheers

Allan

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So no springy thingy, just a solid square shank?

 

How long have you run this?

 

If this is sound then its much easier than wire.

 

I could sell replacements in quantity if that works. Wire is too fiddly to do this I think.

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It's been on at least 3 years (or more) so at least 15-20 k so far.

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Had the pleasure of fixing my drive today...

 

Ordered new drive and right angle as prep, but found that the drive "spring" had frayed seized and caused the drive to snap, but the original looking (brass lock ring) right angle, looked good once cleaned, undid the little screw, filled with light 3in1, and reassembled..

 

So new cable and drive original right angle..

 

Works well, but a bit wobbly, past 75 :rolleyes:

 

Rich

Edited by tr6wilts
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Just to remind you all, this is our ol' mate Bastuck:

https://flic.kr/p/ou94i5

The big gear is the Bevel and the small one the Pinion.

 

Compare him to Smiths, the original and best:

https://flic.kr/p/otdZQH

 

Let me say that he is clearly marked Bastuck, but could have been made in some far-east sweat-pit and just givien this marking, because they had heard the name. He may be a counterfeit!!

 

So whats wrong with ol' Bastuck then.

Man is he sick. And it ain't old age either. He's hardly been anywhere.

 

Let's start with the obvious reason he got took out and retired. The bevel wasn't going round with the wire-stub. The wire was, and still is, crimped into its ferrule. This is the kind of low-tech operation repro guys can do OK.

 

The ferrule diameter is 0.235in but the hole in the bevel is 0.240. It only holds kind of because the last 1mm of the ferruke isn't round. The crimping has left it oval. Just this tiny bit was doing the driving. But not for long.

 

The bored hole in the bevel is rough and chewy. Done with a blunt drill. This is why its gone oversize.

https://flic.kr/p/ocFbbE

 

For comparison Smiths has a ferrule of 0.235in and a mirror finished bore of 0.235in. They fit intimately now, as they did in 1966 or so.

 

But hey, whats this I see the wire-stub has been buckled up a bit. So this drive jammed before the ferrule broke free. Actually it jammed quite obligingly for me when I "reversed" it.

 

So now we look at the brass bearing bushes that the shafts of the pinion and bevel run in.

A good running fit, allowing for some thermal expansion would want the hole 3 thou bigger than the shaft.

 

I checked Smiths, 0.332 running in 0.329 and 0.246 running in 0.248. It feels nice. Bit of wobble on the bevel but you got to look for it.

 

Bastuck, well its 0.346 running in 0.361 and 0.248 running in 0.256. This allows the bevel and pinion to "run askew". They can jam if you do this. You can see the pinion walking about in the hole.

 

But whats this, as I wiggle him about, the pinion jumps axially by about 3mm. He's not controlling his end float.

 

If you look at what substitutes for the nice "top-hat" in Smiths, he's only got a flatish disc. And there is no witness-mark to show the bevel ever touches the disc. Actually the bevel hits the case and this is why I found Mazak shavings in there.

 

The peenings were uneven and the outer disc was on the cock, as shown here:

https://flic.kr/p/obJeW7

Its not been pressed home fully.

 

At least the pinion hits the pointy washer, Eventually. But this was cocked too. the witness mark is not in the middle of the pinion face.

 

So poor ol' Bastuck never had a chance. His holes are too big. His washers mis-shapen and on the cock.

But cheer up ol'friend. Now you have met me.

 

You can have a new ferrule that fits. You can have some end-float bungs that keep you in the middle.

 

Maybe you will get new bushes to keep you on the straight and narrow. But this is hard.

They cast them in so I'd need to machine them out.

https://flic.kr/p/otdZJv

See how the cast flows over most, but not all of the brass bush.

 

Ol' Smihs is OK I could pull his bushes out I think.

But then they have an axial grease groove so they won't run dry. Ever!

 

There will never be a better example of why you should retain and try to repair the original parts rather than use low-volume repro copies.

Edited by AlanT
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Been "off air" for a while, but conferred with my "co-fiddler" yesterday. Yes Roger, I had noticed but we did square it off first.

 

The detail I did confuse however, was precisely which part of the drive we actually replaced. It was the internal drive from the angle drive to the gearbox. not the cable end.

Cheers

Allan

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Well you used good stuff. I think ordinary mild-steel would fatigue.

 

The trouble is this is awfully hard. I keep seeing the video of rotary-broaching in my mind.

This may gradually enlarge the hole in the OD. This is brass I think.

 

I'll see how difficult the wire stuff is to work. Poor ol' Bastuck needs a break.

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Here are a few more interesting details, that came to light today.

 

Smiths ferrules are really a work of art. They carry an internal thread so that they actually screw onto the wire.

I know this because I unscrewed the bits of broken wire out of them and can see the thread in there.

 

But to match the wire you need a 13TPI thread with four starts. This is because the cables are made by winding four wires, each 0.019in dia, around the central core. This part did not therefore have the thread cut in there, but rather the thread was pressed in, by squeezing the ferrule onto the wire.

 

There are however, no marks left by this operation. This is because the ferrule was precision-ground to size, with the wire inside it.

If the wire I am expecting has the same pitch it will just screw on. The direction of rotation is such that it will be continously tightened while driving normally.

 

Now strangely, Bastuck has the opposite, left-hand, thread on its wire. So it can't be just screwed in or it would undo, most likely.

So its been brutally crimped and to get it in the bevel, they made a big hole for it. This is actually pretty funny.

 

Another tiny but vital detail is that the hole, in the ferrule, is tapered so that the wire leaves it without meeting a sharp corner.

The wire breaks about 1/2in past the end of the ferrule.

 

The TR6 drive, the one with circlips, has the wire failed exactly at the end of the ferrule. The ferrule is too short and comes to a sharp corner.

 

It is tiny details such as this, that are the difference between a running life of 10 months or 10 years.

 

The wire strands, by the way, carry no spring-temper and so silver-solder will not degrade its behaviour.

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Alan,I notice that some have a small Screw and Lock Washer in the Bottom and one of them has not,is this a Lubrication Point or maybe something else,if Lubrication what is the Lube and how is one supposed to administer it,Cheers.

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They ALL have this screw. I've been wondering why also.

 

You could add oil through this hole. It would be good to do this, but it would run out, because there are no oil seals.

 

Originally these were greased. But getting anymore grease in, through that little hole, would be tricky.

I think this an historical left-over.

 

I'll use Lithium grease when I re-assemble them.

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