A dolls head adjuster bolt made a successful bid for freedom the other day. I have just received a new one (i.e. bolt + cross bar + retaining screws) from RGM. I intend to cross drill the retaining bolts and lock wire this time (could be tough in stainless steel). But I see it has a locknut on the long threaded portion. I'm sure my old one did not (probably why it escaped). Does the nut screw up against the back of the top gearbox bolt? I expect I'll find out when I try to fit it, but I've not found a drawing of how it is supposed to go together. Access is pretty tight.
See Paul Norman's site....
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Thanks Michael. I'll use my…
Thanks Michael. I'll use my mini milling machine as a drill press... it's very rigid. I think it's best to push quite hard quite quickly to avoid strain hardening. Yes - I see Paul Norman's version. I'll see if I can get a small spanner in but I don't think it will fit. But RGM must have got the design from somewhere!
My original three-holed-plate cracked across the centre hole. The replacement was new old spare from Russells.
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I'm sure you know this...
.. but when adjusting the primary chain overtighten it slightly first then use the adjuster to push the gearbox forward to get the right slack. This takes up all the lost motion and ensures that when you ride the bike the extra tension in the rear chain doesn't pull the box back and undo all your good work.
I always err on the side of too slack rather than too tight anyway.
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Thanks Ian - I remember this…
Thanks Ian - I remember this from my Dommie, but always need to remind myself which chain is tighter!
I fitted the adjuster yesterday and of course there's nowhere to fit the nut that came on the long thread. I can't understand why the previous one escaped, but I've drilled the heads of the two fixing bolts now. I love my little milling machine as a drill press - went straight through with 1.6mm bit no problem whatsoever.
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Just seen this . . . an update
Hi Folks, ths is Paul at RacingNorton,
Just fyi - yes, we make this assembly in stainless steel (the difficult bit is the adjusting bolt that has to have its head silver soldered on, once the retaining bar is placed on, then the head turned to profile, again on the CNC.
But just to let owners of Norton's with upright gearbox's know - this is always a difficult task, to adjust the correct level of primary chain tension with the upright gearbox, it typically is very difficult to access the top nut , with battery carrier (road bikes) or wrapround tank (race bikes) . . and often, the chain changes tension after adjustment!!
fyi - many years ago I 'donated' a special ring spanner - which is correct size for the nut (there are typically two types on upright gearbox's - the big 'full hex' type used on most WD and post war types, and the pre-war 'Manx' type we manufacture (see link above) . . . both use std Whit spanner sizes - but I used a cutting disc to cut the ring spanner so it was 'C' shaped and open ended, but then - used oxy acetylene on the spanner shaft to bend it to the weird 'L' shaped appearance, that means it could best fit into the confined space available at appromately 9pm when viewing from the primary drive side. This enables me to more easily adjust and tighten the gearbox primary chain tension - a 'Must' in racing days . . . when engine sprocket used to get changed on every circuit. Email me on our site - www.RacingNorton.co.uk if you want more info about this, or some of the issues on rigid/plunger frames that affect the abiltity to get a good tight fit when adjusting the upright gearbox. chrs . Paul. www.RacingNorton.co.uk
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....https://racingnorton.co.uk/epages/4c675e64-813f-4c0a-8926-87a680c962a0.sf/en_GB/?ObjectPath=/Shops/4c675e64-813f-4c0a-8926-87a680c962a0/Products/%220569%20GearbxAdjstSet1%22
No locknut but seems like the bolt can be snugged up after adjustment and tightening cross bolt. Safety wire not bad idea. Use short cobalt drill bit on SS and drill guide. And preferably drill press.