Model 88 dynamo drive

Hi Geoff...just to say I think the Bakelite material is actually a material called "Tufnell" it is self lubricating and probably lasts longer without lubrication than with it,but obviously in theengine set up it does get engine oil on it.

I wonder if the steel version should have been well oiled , even greased before assembly?...I don't know how long you have run the engine but as far as I can see, the timing chest only fills up with oil to it's overflow level then overflows back into the crankcase from oil ejected by the blow -off from the oil pressure relief valve.After refitting the cover the chest will be drybut If you have the situation of an engine withworn big-ends, worn pump and thin oil you might not hit the blow off pressure at all and this will leave the timing chestand steel dynamo cogshort ofoil and cause it to run noisily. With the original self lubricating Tufnell version this wouldn't matter as it will still run quietly.

Perhaps an aluminium alloy version would have been better as steel and aluminium combinations createpretty good bearing surfaces.

To ensure there is sufficient oil in the timing chest you could try revving the motorreasonably highly with cold oil for a short while to promote oil blow off from the valve....you never know, but once lubricated well, perhaps the whine will diminish....worth a try I think but can't guarantee it will work...If it does let us know please....Les

Hi Geoff, it would seem that your recent engine refurb would eliminate a potential dry running timing chest. There is just a very tiny chance that the oil pressure relief valve is not blowing off oil but this is not likely ...however the test for this would be to monitor the oil pressure which should plateau out at around 60 PSI....Not suggesting you should bother but then again monitoring the oil pressure after a major rebuild is always a good thing and very reassuring, I would imagine this was always done at the factory before shipping bikes out from new. Anyway I guess you will be removing the timing cover soon as new timing chains settle down very quickly and become quite slack and you don't want chains flapping around in there, so when the cover comes off, expect half a cup to run out to verify normal lubrication is occurring.

Noisy gear drives using straight cut teeth can be a symptom of too tight an engagement. You could, if you feel like it, loosen the three dynamo screws and the strap to see if you can rotate the dynamo just a fraction to loosen the engagement. You might just have a thou or two free movement in the screw holes which at best could be enough to lower the engagement pressure and lower the noise. Don't forget to tighten it up after. Also don't forget that by removing the dynamo completely you can safely run the engine without it, perhaps even see oil splashing around etc.You never know ,but after some hundreds of miles running the teeth might get to like each other and blend together better, which is likely to quieten the running so don't be to impatient and give it some time.

By the way I'm not trying to be pedantic here (but maybe I am) the old drive was made from TUFNELL and not Teflon which could be useful to know if you are getting one made up.

Les

tongue in cheek, Les, he could always use the metal assembly and spray it with Teflon, it does claim to combat heat, corrosion and have chemical resistance!!

The laugh could easily be on me when I eventually get my 1955 dommie 88 ready to fire up, after 34 years in pieces!!

Terry

Yes Teflon spray wouldn't do any harm...anyway... Congratulations Terry in getting the 1955 Dommie ready to run.A few weeks ago I started my completely refurbished M7, but haven't run it for long...before starting it I did have a problem with the cover leaking oil so it was removed and refaced again so no leaks now...However, I cannot remember checking the oil pump conical washer on the second fitting, so now I'm tortured somewhat worrying if the seal was still in place. This is where measuring the oil pressure wouldprovide me with an instant check, so I should make up the fitting for the timing case and measure it OR take the cover off and see...but as everything is nicely fitted I'm very reluctant too...I'm always doing that sort of thing....like fitting the barrel back on, I'm always sure I've snapped a piston ring, then take it off and find it perfectly OK, then refitting the barrel and then thinking I've broken the rings again!...it just goes on and on...torture.....ATB....Les

I was always under the impression that the tufnol gear was a safety precaution, so that the teeth on the dynamo would be the only ones damaged if the dynamo seized. My 1954 dynamo, although overhauled a few years ago, still has the original gear, I would never consider fitting a steel replacement.

Tufnol is quite an awesome product, been around since the 1920's & is still used today. The QEII prop shaft bearings were made from it !

http://ahistoryoftufnol.org/index.html