speedo gearbox

[jellywrestler]

hi folks,
my 5 inch speedo gearbox is a bit second hand. can someone advise me what else had these components fitted t them so i can hunt out a new one if possible please
thanks
graeme

 

[BlackLightning998]

Try David Woods at Chronometrics

Hi,

Have you thought about trying David Woods who operates as Chronometrics, advertises in MPH and is a VOC member. He knows everything there is to know about these.

I would recommend you think about trying him for a fully reconditioned unit.

If it is the head gearbox then I understand that there were two types, early and late so you'll need to identify to David which one you have.

As relating to the drive in the front wheel, I have seen loads of what I thought to be the same thing at autojumbles only to then find small differences, different spacings, different drive shaft finishes etc. so maybe the answer would be either have a part number (can't see one on mine) or take a Vincent one with you when you go looking.

The front wheel speedo drive, I stripped mine, cleaned and overhauled it myself and put it back together again it worked fine.

The head end, I've had stripped gears and David sorted those out for me for about £35.

Hope that helps.

Stuart

 

[Tom Gaynor]

Speedometers

There are articles in Forty Years On which describe how they work, how (within limits) to fix them, and from Ted Davis on what speedos were fitted to what bikes. The right angle gearbox on the back, outside the case, is apparently the same as the one fitted to Landrovers.

 

[timetraveller]

Don't think so Tom. The ones fitted to Land Rovers will fit and will work and, if I remember correctly Colin Jenner at Conways used to, and perhaps still does, supply them as replacements. However, they are noticably larger than the original items. I have had the Land Rover item on my bike for years but they will not suit the purist.

Cheers to all

 

[Tom Gaynor]

I had never noticed, but you're right. The right angle box I used on a Smiths conical tacho must be a Landrover one, with a "barrel" about 3/4" diameter, whereas the Vin one is about 5/8". Too late now: I used to be pure as the driven snow, but I guess I drifted... (Mae West).

 

[Hugo Myatt]

Beware. The early 5" head gearbox (monkey metal) will break the cable if the bike is wheeled backwards more than a few yards. It is a design fault. The scroll is driven upwards by the pinion until it jambs against the casing.

 

[Paul Ennis]

5" speedo gearbox

I don't think it's a design fault Hugo, the effect you describe is caused by the gears wearing thin and jamming when the bike is wheeled backwards.I understand that David Woods can supply refurbished units, but for any DIYers out there, see my article in MPH 669 Oct 04 describing how to replace the gears with new ones from HPC Gears Ltd.

 

[dave g6xnc]

Speedo cables

The breaking of cables on early units was well known at the factory and is mentioned in Richardsons book the design was changed to avoid the problem. Incidently another piece of usless in formation if you find the that the teeth on the ring gear on the hub are worn take it off and reverse it and put it back. Teeth on the gear only wear on one side.
dave gs.

 

[Hugo Myatt]

I bow to your greater knowlege Paul. This is over 20 years ago but as I remember it the scroll gear (This is probably the wrong technical term but you know what I mean) is champhered at the end in the direction of the thrust when the bike is in forward motion. The other end is not champhered so that when the thrust is in the reverse direction as when wheeling the bike backwards the sharp edges of the teeth dig into the end cap and lock it up solid. At least this is what happened to mine. My garage is at the end of a very steep drive entailing paddling the bike backwards for some distance. The cable would break after the exact same number of wheel turns. It took me a long time and many cables to work it out. I had a slight champher ground on the other end of the scroll and no further problems.

 

[Tom Gaynor]

Having just read Paul Ennis' article in MPH 669, I jalouse that the reason for the "Landrover" gearbox being bigger, and therefore "impure", is that it holds nylon gears, not steel, and they have to be bigger. I know that some right angle boxes do contain nylon gears, because I've had them strip, on other (lesser...) bikes. In turn, that suggests is that what one needs to be looking for is a treasure trove of pre-1954 Landrover speedo spares, c/w right-angle boxes with steel gears. At 1954 prices........
I know that the 5" speedo was made by Smith exclusively for Vincent (PEI says so) but am guessing that the gearbox was an off-the-shelf item.

 

[clevtrev]

Having just read Paul Ennis' article in MPH 669, I jalouse that the reason for the "Landrover" gearbox being bigger, and therefore "impure", is that it holds nylon gears, not steel, and they have to be bigger. I know that some right angle boxes do contain nylon gears, because I've had them strip, on other (lesser...) bikes. In turn, that suggests is that what one needs to be looking for is a treasure trove of pre-1954 Landrover speedo spares, c/w right-angle boxes with steel gears. At 1954 prices........
I know that the 5" speedo was made by Smith exclusively for Vincent (PEI says so) but am guessing that the gearbox was an off-the-shelf item.

It was probably available in France, as it`s 100% metric.

 

[Tom Gaynor]

Next you'll be telling me that Eddy Stevens is half French........

I found another "large" right-angle gearbox (while looking for something else) which lacked an end cover. The gears are indeed nylon (or at least plastic).

 

[vapide]

There seem to be at least three gearboxes one may encounter on 5" Shadow clocks. As I understand it, the original ones had non-threaded inputs, so they could only be used with the original gearbox which clamped over the input stub. Repros usually had a standard movement with a threaded stub so a cable could be attached directly, but were supplied with a Smiths BG2410/00 gearbox which has a captured knurled screw which screws down over the threaded input stub. Later repros seem to use Landrover gearboxes. I think the Smiths is a little smaller but can't swear to it. Just to make it more complicated, there was a modification available in the old days to eliminate the troublesome gearbox by putting a threaded input on the original speedos so the cable could be run straight out of the back, and its possible an original speedo so modified could have been fitted later with the BG or Rover box. Doug Wood apparently has a source of the original style boxes which he uses in his repros. The Smiths BG is no longer made but NOS ones turn up fairly regularly (I bought a couple recently for $50 each), and the Rover one seems to be readily available.

 

[Paul Ennis]

5" speedo gearboxes

Hugo, I guess that your problem gearbox was the early type as mentioned by dave gs, pre-dating the ones that I am used to. It seems logical then, that the steel thrust washers and the 3/32" ball bearing were Smiths' cure for breaking cables. That is until (after about 50 years) the gears wear out!

 

[Hugo Myatt]

Paul, I guess your are right. I certainly don't remember any steel thrust washers but I am not going to take it apart to look. If it ain't broke don't fix it.