Speedo inner cable

[Duccout]

Does anyone know how far the square end of a speedo cable should slide into the drive shaft at the wheel end? When I bought my Spanish 250 the worm drive shaft did not rotate and I found that the teeth were worn out. I bought a new one (at vast expense) from the Ducati Vintage Company which works, but keeps wearing out the square end of the cable. A 2.57 mm cable will slide in to a depth of 30 mm, but is too sloppy and wears out; a 2.6 mm cable is tight in the housing, but hits a stop at 10 mm depth.

I don't know why there should be a stop inside the shaft; maybe it is just badly made and the cable should fit in further..... It is all a PITA! I have tried shimming the smaller cable out with a strip of shim steel, but the clearance is tiny across the flats, it is the corners of the square that are too small. I am going to get a new inner made, but I would like to know how far into the drive shaft it should go.

Thanks,

Colin

[blethermaskite]

Colin, I have had this issue numerous times so what I do is (and as you have tried) make a super thin shim to make the squared end bigger ....or..... very carefully file down a bigger squared end to fit, I know filing it down seems wrong but you are only taking a few thou off to get a fit, what I would do in your case is file up a 'dummy' square to get a perfect fit which will of course give you the dimension to reduce your 'too big' cable end. So I don't know how deep the cable should 'go in' generally I would expect around 18/20mm 10mm seems a bit short to me, can you run a needle file down the bore to clean up any 'crabs' in there? Cheers George

[Duccout]

Hi George,

Thanks for the reply. I have just found the original speedo drive shaft (I knew it would be somewhere amongst all of the junk) and basically the hole is the length of the shaft. The original has a squared off section at the top that the cable engages with, and the cable slides through this and can go all the way to the bottom. The new shaft from Ducati Vintage does not have the squared off section, it is ground internally to a square shape, and only to a depth of 10 mm (although the hole continues to the end of the shaft).

So, as you say, maybe I could file out the square hole deeper (although if the shaft is hard that will be impossible) or I will have to get a new inner cable made that only allows 10 mm engagement, but I'm guessing that it will not last long. I need to keep my eyes out for a used shaft, but it is unlikely that one will turn up. Pattern parts are a pain, but without them we would have nothing so I suppose that we must be grateful.

Cheers,

Colin

[Jordan]

The normal way to make the square hole is evidently to insert a square solid steel "anvil" the same size as the square cable end and squash the hollow shaft end at four places.
I had some plastic gears printed to replace the original steel one.

download/file.php?mode=view&id=8239
download/file.php?mode=view&id=8240

[Duccout]

Thanks Jordan, that is interesting. I assume that you turned off the old gear or did you make a new shaft?

Cheers,

Colin

[Jordan]

No Colin, the steel gear is a separate piece, pressed onto the shaft.
I used a bench vice as a press, with a tube and a rod to remove it.
The plastic replacement is pinned to the drilled shaft.

[Duccout]

Thanks Jordan. Maybe I can refurbish my old shaft.

Cheers,

Colin.

[Jordan]

I'd offer the STL file for printing the gear, but it's for a 4 leading shoe brake, which differs in the angle that the cable exits the brake plate, with a different helix angle on the gear.

[Duccout]

OK, thanks.

Cheers,

Colin