Bike Weights and Weighing

vibrac

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I have read differing views on the following method. Bathroom scales under front wheel, back wheel on block same height, balance bike with steady hand on handle bar after pulling upright from slight lean on wall. repeat for back wheel. Add two totals. The question is, can the result be true?
 

greg brillus

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I bought 2 sets of el cheapo bathroom scales, the old school type with the rotary needle, make up some simple ramps and wheel the bike on. Hold the bike upright with your fingertips on one bar end and read the scales.......On my current single racer the front was 65.5 kg's and the rear 64.5 kg's........that's near enough to 130 for me.......With oils, no fuel.
 

Mike 40M

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Impressed Greg. Makes it 10kg lighter than a standard Manx, witch has all the fancy magnesium engine parts and throughdrilled bolts. Still some 15 kg heavier than a Yamaha TZ though.
A modern MotoGP racer has a minimum weight of 157 kg.
 
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brian gains

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if this weight question is causing sleepless nights I have a hanging, sack scale? free for collection.

of more interest/alarm is that AMC boxes have difficulty handling 850 torque let alone 1300cc (1100cc in my case) and there I was looking forward to a summer of lurve once the bike is back together.

on the weight Q; I love speed holes as much as the next man but drilled flanges on ali' rims, does that really amount to anything significant?. I would have thought the trade off in weight saved against, and accepting, the questionable aerodynamic benefits of deep rimmed wheels would cancel each other out.
 

Pushrod Twin

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I see that you are using the same alternator that I have been fitting recently for the 'Walkernator'. I drive it at double engine speed on twins to ensure that it starts to charge at low revs. I also use a multi vee belt drive to take out some of the shock loads which are inherent to the standard Vincent dynamo drive. I could not mount my system as low as yours because of the standard gearbox top and yours looks very neat, Once you have it on the road I will be interested to learn about its performance with regards to shock loading the primary drive and low speed charging cut in speed.
100 Greenbacks on Fleabay USA, marketed at hot rodders. Looks like ND but has no markings, made in China I suspect.
I drive it direct off the back of the chain with a standard Vincent dynamo sprocket. The clutch drum is Norton Commando with the centre row of good quality hardened teeth machined off. It has 1 tooth more than the Vincent sprocket.
There is a little rubber cush coupling between the sprocket & alternator The short sprocket shaft is supported by two ball races in the 1/2" 2024 T4 engine plate.
It's been running 2 years & 5000 miles now. I was in the case to change clutch plates a few months ago, no sign of distress. I have no ammeter, just a red charge light. Light flickers when pushing kick starter down to feel for compressions then disappears, no flicker at idle.
There is a smaller ND alternator fitted to modern Russian Urals and it is face mounted. I would like to use that one for my B motor but I'm still looking for a cheap source.
 

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Chris Launders

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I believe the problems with the AMC box were caused by the weak layshaft driveside ball race, cured long ago by using a roller bearing and the weight of the standard Commando clutch with the bronze plates. most people building them into specials use alloy belt drive clutches with fibre plates some fitting a bearing behind the clutch on an outrigger plate. I know many people using this sort of set up (with and without the outrigger) and not heard of any problems.
 

Pushrod Twin

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of more interest/alarm is that AMC boxes have difficulty handling 850 torque let alone 1300cc (1100cc in my case) and there I was looking forward to a summer of lurve once the bike is back together.

Yes, that keeps cropping up. Mine is a "standard" Rapide, maybe 8:1CR, 28mm Delortos, Mk III cams, nothing at all spectacular.
However, I took the opportunity to support the outer end of the sleeve gear in a bearing as I believe the factory racing Commandos did. It only needed a few thou of hard chrome and a precision grind to fit into a half inch wide ball race which in turn lives in the 1/2" engine plate.
You can see in one of the pics above that I used a Vincent slipper chain tensioner.
I dont go with the folklore regarding the "heavy Commando clutch" I dont see why the weight of the clutch would have any influence at all. It is simply the force generated by the power of the engine which pulls on the wee spindly shaft.
There are other separate g/boxes which are up to it. Roy Robertson's race bike runs a box which looks like a Triumph and that motor makes plenty grunt. I recall him telling me it has 5 speeds.
 
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stu spalding

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A guy I only knew as "Digger" put a 3.5 litre Rover V8 in a featherbed and ran an AMC box behind it. When doubts were expressed he replied that he had fitted "an outrigger bearing". This machine broke the primary drive belt but the gearbox was OK. Cheers, Stu.
24  Digger's              Norver.jpg
 
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