Thorneycroft 154 Tachometer take off

[SiandSue]

The tachometer take off on my Thorneycroft consists of a mechanical angled drive unit by AC and an electrical generator by VDO which powers the tachometer. The mechanical drive unit was broken when I bought the boat and had been removed. I have managed to source a new one but unfortunately the part that connect the drive to the generator is missing. Does anyone know where I might be able to source one.

[Tony Brooks]

I am afraid not but if you had asked before buying I think most of us would have advised you to buy an alternator driven one and if necessary get the alternator modded to drive it, but your alternator may already have a tacho (W) terminal.

 

You could try ringing Calcutt Boats and ask them but I don't hold out much hope.

 

 

I am also unclear as to what is missing. Is it the gear that fits inside the engine, the piece that bolts onto the engine and holds the gear in place plus provides the thread for fixing the drive cable outer, or the piece that screws onto that fitting which is part of the cable. It could even be the cable inner or outer that has broken. If it is  a cable problem then a company that supplies speedometer cables for old cars may be able to help.

Edited July 14, 2021 by Tony Brooks

[Tracy D'arth]

Anything like the Austin Healey drive that went on the back of the dynamo? If so it is possibly available from vintage car parts suppliers, Moss?

[Tony Brooks]

10 minutes ago, Tracy D'arth said:

Anything like the Austin Healey drive that went on the back of the dynamo? If so it is possibly available from vintage car parts suppliers, Moss?

I had a feeling the piece that bolts onto the block might look like a typical 1960s speedo gearbox fitting, but what vehicle it might have fitted or if the gear was a special to match the camshaft is anyone's guess nowadays.

 

I think a photo of the area and existing pieces, plus a sketch might help.

 

I also seem to remember the cable is a bit chunky.

Edited July 14, 2021 by Tony Brooks

[SiandSue]

Thanks for all the replies. I am struggling to upload photos for some reason. 

As commented the drive unit is commonly used on vintage diesels so is not hard to source, don't know why previous owner had difficulty. 

What is I think is unusual is that the generator fastens straight on to it using the thread that an outer cable would have used. This means that what you might call the inner cable is about half an inch long and this is what I am missing. 

Currently all my engine gauges are Thornycroft branded hence my preference to keep to original. Once you replace one gauge you end up replacing them all and then your messing with 40 year old wiring so you end up replacing that and then all of a sudden your in yet another n thousand pound hole. You know the story, and then the missus sees whats been spent on the boat and wants a new kitchen/bathroom. 

Any way I'm retired and don't mind a bit of a challenge. 

[David Mack]

1 minute ago, SiandSue said:

I am struggling to upload photos for some reason. 

Maybe your photos are too large for the forum. Try using a graphics program or online image editor to make them smaller.

[SiandSue]

[David Mack]

18 minutes ago, SiandSue said:

What is I think is unusual is that the generator fastens straight on to it using the thread that an outer cable would have used. This means that what you might call the inner cable is about half an inch long and this is what I am missing. 

So all that you need is a short shaft, presumably with ends shaped to fit the matching components in the angle drive and the generator. I imagine you will struggle to buy one off the shelf, but it should be a simple job to make up something to suit.

[Tony Brooks]

Assuming its a short length of square section "cable". I suspect if you can find an old, long-established country general garage they could make up a short length of square speedometer inner that would suit. We need to see down both holes to see the shape of the existing drive parts to be sure. As David says, it may be perfectly possible to file something up.

[Tony Brooks]

Try contacting these people https://speedycables.com/

 

I suspect they will want more info and dimensions about the parts you have and how they join. Much like I suggested  a photo of what is down the two holes. If its two hollow squares, then I am sure they can help you.

[SiandSue]

Hard to see but looks like a square cable fitting in the drive end.

Large slot in the other.

I am thinking I could maybe make something from a brass screw and solder a plate on the end.

[David Mack]

Rather than solder, I would be tempted to make a single piece, filed down from a bit of brass.  Plenty of suppliers on ebay serving model engineering types who will sell suitable small pieces of brass.

[Tony Brooks]

As the shaft and flat piece need to run concentric with each other, I am not sure that I would try to file down from a solid bar because it would be all too easy to make then eccentric. I would probably start with a brass bolt and file the head to form the flat piece.

[SiandSue]

I will have a try and let you know how I get on.