Author Topic: Side cover "circular plate" question  (Read 2796 times)

Online Brian

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Re: Side cover "circular plate" question
« Reply #15 on: 19.07. 2008 00:55 »
Its a bit difficult to explain but I will try. SRM are correct with their explanation. Imagine you have the crank sitting on the bench in front of you. First you would put the shims on, then the bearing, then the steel spacer [the one the seal runs on] then the splined sleeve and finally the nut. Once the nut is done up all these parts are trapped between the crank and the nut. This is why the nut must be done up tight to stop any of these parts being able to move. With a roller main bearing the end float is critical as even with the nut done up tight the whole crank assembly can move sideways. The early [plunger] engines had a ball bearing main and provided the outer of the bearing is tight in the crankcase the crank is held in position by the bearing. Some people use ball a bearing main in the later motors that originally had roller main and there are arguments both ways on this subject. Anyway, back to the cush drive. The sprocket and lobed piece and spring are independant of all the parts on the crank. Even when the spring is fully compressed the lobed part can not ride up and over the other lobed part. The idea of this is that as the two lobed parts work against each other, when you accelerate the lobed parts climbs up its opposing lobe and when you are running on a constant throttle it settles back to its normal position. I should also mention that sometimes when you dismantle these things you will find shims between the steel spacer [the one the seal runs on] and the splined sleeve. These are to align the sprocket to the clutch. If you have a six spring [plunger type] or a four spring type clutch it does pay to check the alignment of the sprockets and use shims if necessary. If you have the other six spring clutch [external springs with nuts on them] it doesnt really matter as the chainwheel moves anyway. I have that type of clutch in some of my bikes and have got them to work well but I dont like them, poor design I reckon. Well I am not sure if this will help or just make it all more confusing.      Brian.

Online groily

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Re: Side cover "circular plate" question
« Reply #16 on: 19.07. 2008 06:53 »
Illumination! So in fact what I call the AMC factor does apply Brian - in that the spline/sprocket etc DOES abut the bearing effectively and I was wrong to have said the crank and its end float, shims etc are independent and unrelated. I thought the sleeve was held just proud of the spacer (and therefore of the bearing) against a non-existent inner end of the mainshaft spline and that therefore the sleeve could not whack same. Humble pie with extra worms on order . . .  But I'm keeping my split pin all the same! And the tooth puller.  I shall look at it all a bit more carefully the next time (it'll be the first time for this engine) the crank is on the bench. Hope it's not any time soon as it runs so sweetly it'll be a shame to disturb it. Looks like it's in for a very wet and miserable couple of hundred kilometres today . . . where is Summer (for those of us who ought to be having one by reason of our northerly orientation)? Nothing worse than wearing wet-proof gear on warm and  heavy days . . .
Bill

Offline octane

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Re: Side cover "circular plate" question
« Reply #17 on: 19.07. 2008 15:01 »
Oi ! Lot's of interesting stuff here Gentlemen
Thanks.


But one thing totally beats me:
WHY that seperate 'circular plate' ????
Why isn't it just a 'build-in' part of the crank-case.
Why doesn't it just have that extra 2.4 mm / 0.095" , where the plate is put on?



..or why isn't this flange just 0.095" further 'out'





It's a bit weird.

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Re: Side cover "circular plate" question
« Reply #18 on: 19.07. 2008 18:05 »
Probably because the drawing office made a ****s of it; or because of the problems of making one semi-standard design of frame and transmission cope with all sorts of engines! It all adds to the mystery of it . . . some of which I am exploring with the addition of a gentle and charming single to the shed  (with attendant hassles, as ever . . .)
Bill