Dommie Primary Chaincase nut

You boys are great!

I do have the lugs located properly Robert. However the ‘new’ rubber band is neither a consistent rectangle or tapered - very badly cut.

You have pointed out the problem... I will pursue options to fix - many thanks!

steve

The band conforms to the spec in terms of section/taper and lip. It’s a very slight taper.

My pic showing the centre nut on is without the rubber oil seal and chrome washer! With those added I am a looong way off getting the centre nut to catch a thread!

in fact, if I remove the rubber band completely and fitted the outer casing the rubber oil seal, chrome washer and centre nut and they all fall into place with a couple of threads showing as proscribed.

Its as though the rubber band is not required at all!!

I do wish my local meet gets going again soon - would be great to have some expertise across a tap room table!!

Steve

Thanks for that Lionel.

It appears that the rubber band is way too big for the job.

I need to start eliminating potential probs - so I think I’ll start with a new band. 

Current one bought late last year from Andover as part 06.7627... and according to Andover same as part numbers A2/486 and NM 13185. Which is interesting because Norvil say 067627 is for Dynamo and Alternator types and A2486 is for Dynamo types .

RGM have 060398 - which looks a lot thinner and says it’s for pre MK3. And cheap at £2.20.

This strategy could get expensive but I’m tempted to order from RGM and see what it is.  Unless anybody got a better idea?

I really hope I don’t have to buy new inner and outer chaincases !  

Kind offer Robert - I’m near Newark now so swaps are a bit ambitious! Built so far from a box of bits with no previous experience so many will say no wonder I have these challenges! I don’t mind spending a little if I can get the right solution... but the missing factor is meeting local guys who have had the same/similar experiences. But I won’t be beaten!!

steve

... just to answer the question!

David & Robert

inner case fitted flush to crankcase - with gasket. Alternator / clutch not holding outer off. Only one serrated peg mount length.

I’m not a religious chap but praying the thinner pre MK3 rubber will do the job. Worst case is I have mismatched inner and outer cases... not thinking that far.

Progressing onto gin.... awaiting parts.

Steve

...

In the absence of any info on restarting Club nights - Is there a person on here who lives near enough to Farnsfield - NG22 8LD - who has Dommie experience, to make a home visit?  Reasonable expenses paid, tea/coffee and biscuits provided during consulting and probably a bottle of something to take home if successful.

Yours in desperation.

Steve

PS - I’ve written to Andover, Norvil and RGM setting out the problem with pics. Andover have replied and have no idea. Awaiting other responses.

..

Rubber bands have grown over time. Plus they used to have a much more pronounced taper. What you buy today are much bigger in section and with a lot less taper.

He suggest find a mate with the kit to taper the band - may need a couple of goes - this will solve the problem.

What a bloke!

I’m on it!!

Steve

Al

thanks for wading in... during my test build I had both inner and outer tested and outer flattened back to “standard” on a bench press.

Pete Lovell suggested this might be the problem - but I think he was kidding!

I am constantly checking the flatness of the outer - it’s flat across its whole rim.

in theory I would need to depress the middle of the outer (without bending it out at its edges) by about .3”. Surely too far? ... but maybe a solution for an engineering shop.

Norvil now tell me there were four different lengths of hangar / serrated tube from 3.5” up to 4.415”from face of engine plate to tip of serrations. (Since 1932). I’m awaiting an answer on which I should have, part numbers etc. Best measurement on mine suggests it might be a little short of 4.415” but I’m gonna have to strip it to find out - will not a problem.

I am expecting fellow member Jon Newton calling this eve to apply some additional skills - he’s bringing some older rubber bands.

I really am looking forward to pestering you about 12v and EI.

Steve

Just spoken to machine shop who straightened outer case for me - quite possible they pulled centre out - thus losing required threads on hangar tube.

They suggest fitting without rubber band so that can get nut on and slowly - one turn at a time tighten up - check with band fitted and repeat. Keeping an eye on bowing whole casing.

This fits Al’s theory and is something simple like Robert suggested.... and Pete Lowell’s “joke” turns out to be a fact!

Steve

I’m now about 1 thread of getting the nut on with its rubber washer and chrome finisher - with big sealing band.

I’m confident that you have cracked it!

Thanks Al for the starter and all who patiently contributed. Every day is a school day and I’ve just reinforced a lesson learned some time ago and Robert pointed out - the bigger the problem appears the more likely there is a simple solution!

I’ll be back with another one shortly, no doubt.

Steve

Thanks Al, gradual wind on/off of an old nut and suitable washer “reshaped” the outer chaincase until I could get the pukka rubber seal, chrome finisher and chrome nut in place. With no detectable distortion of the outer case. See pic. Get the forks on now!

steve

Worry not... cash available - but when we get to electrics you now have an appreciation of who/what you are dealing with!!

steve