Gearbox issues

Peter Roydhouse, in the technical/singles/gearbox section, states that the gears for the upright and laydown boxes are identical and therefore interchangable. Try the club spares scheme for bits for your box. They provide an excellent service at very reasonable prices.

Although no gear trouble with my 16H dolls head box, back in 1975 the laydown box in my 1955 19s Combo did jump out of 3rd. I learn't too ride without engaging third gear.

I asked an expert of the time 'why third gear ?' To be told that it is selected more than any other gear and therefore gets more wear. I don't think being packed with grease rather than gear oil will have helped either.

I should have had the box apart when the splines went on the kickstarter, but instead, had it welded to the shaft. Things you did back then in the inexperience of youth!

Good point David, I made a slight adjustment to the rod on my dolls head box when I got it as I found the changes sloppy (Though not jumping out) And now it is a positive stop change as advertised. Incidentally, over a thousand miles later, I've never had to adjust it since. I use Castrol EP 140 gear oil.

Somewhere on the net (I thought it was this forum but I can't find it), there was quite a discussion about the machining of the Dollshead' dogs and the undercut.

The conclusion, which was illustrated is that in fact there does seem to have been an error in how these were originally drawn and then manufactured.

That said, hundreds of thousands of them have done hundreds of thousands of (mostly side-valve) miles so in practical terms, they so seem to keep working.

Previously David Cooper wrote:

Have you made sure the operating rod is correctly adjusted? Mine started jumping out of third and was transformed by adjusting the rod by one thread pitch. The rid needs to be slack both in second and third. ..

I am having exactly the same problem with my dolls head gearbox despite a full rebuild. When you say 'make sure the operating rod is correctly adjusted' could you elaborate? I'm not sure what you mean by the operating rod.

Thanks in anticipation

Thanks for the information David. I will check the adjustment when I get chance. I've just got back from a weekend in the Isle of Man with the old girl (ES2 that is). Apart from the 3rd gear issues she ran really well. I did 2 laps of the TT circuit on her touching 80mph down Creg-ny-baa with a 1938 500 Red Hunter on my tail.

Previously Richard Moss wrote:

Thanks for the input. I'm guessing that there must be some other issue for this amount of damage, possibly as well as the fact that they are used a lot on third gear. It's quite noticeable that the damage is all on the corners. Why would that be if the faces were parallel. I've also got some wear to the linkage from the foot change mechanism to the cam plate indexing mecanism, so maybe it just isnt actually fully engaging the dogs and the undercut is having to drag the gears in.

Anyway, will look at spares shemes stock and go from there.

Many thanks.

Of the boxes I have used snicking out of third is the most common problem and in the main has been remedied by setting up the positive stop indexing mechanism rather than dog wear... Seems the throw is marginal if thee is any slack in the linkage.

It probably isn't a design problem with the third gear, but more likely a reflection that most of these bikes will have spent years pulling heavy chairs, where third gear is predominantly used.