• Welcome to the website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Hon. Editor and Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this website.

    If you have previously registered to use this forum, you should log in now. CLICK HERE.

    If you have never registered to use this website before, please CLICK HERE.

Bike Weights and Weighing


greg brillus

Well Known and Active Website User
VOC Member
Shaving weight off a bike like a racer is not too difficult, the wheels are the biggest problem. If alloy castings were replaced in magnesium the weight savings would be significant.......look at the wight of a Manx. Glen is right about the weight specs on the engine, and a belt primary/clutch is a huge weight saving........On the suspension you can save big amounts by doing away with all the spring boxes and shocks, with a single coilover front and rear that weigh in at 1 kg each.
 

Pushrod Twin

Well Known and Active Website User
VOC Member
Lose 20Kg, chop the gearbox off! Oops, sorry, that's culturally insensitive these days o_O But is it really? None of us would chop a genuine set of period cases these days, obviously, but is there a problem chopping a new, aftermarket pair? Do I recall that Ian Hamilton was discussing having new cases cast without the gearbox end and making provision for an AMC or similar box? I also understand that may be pushing the definition of the racing rules in which you are competing Vibrac.
Here's mine at 80kG, no zorts as quoted by Glenliman, but an alternator to make up for it. The drive side looks "standard" Vincent.
 

Attachments

timetraveller

Well Known and Active Website User
VOC Member
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.
 

Albervin

Well Known and Active Website User
VOC Member
It all depends where the weight is. I have ridden bikes that differ by less than 25kg and yet they feel 100kg different. I would love to lose some unsprung weight from my Shadow as it would make for a much sweeter steering and handling machine. I have thought about fitting Brampton forks as per my Rapide with coil over damper but that doesn't address the unsprung weight. Unfortunately Aussie roads are not kind to alloy rims so it is about the brake drums and sprockets.
 

oexing

Well Known and Active Website User
VOC Member
As to alu rims , are you sure about less sturdy than steel rims ? I imagine most off-roaders have alu rims, no steel . You have to hit a big stone right on to ding the alu rim but same with steel I guess. In that rare case you´d change the rim anyway so I´d prefer to have flanged alu and live with it. What matters a lot is a perfect job with spoke tensions all round for good rigidity of a wheel.

Vic
 

Vincent Brake

Well Known and Active Website User
VOC Member
It all depends where the weight is. I have ridden bikes that differ by less than 25kg and yet they feel 100kg different. I would love to lose some unsprung weight from my Shadow as it would make for a much sweeter steering and handling machine. I have thought about fitting Brampton forks as per my Rapide with coil over damper but that doesn't address the unsprung weight. Unfortunately Aussie roads are not kind to alloy rims so it is about the brake drums and sprockets.
Get the motorcycle center of gravity in the line from middle steeringhead races and other point is rear axle.

Tony Foale.
Yamaha.
And the rest.

And i can do you some heavily drilled drums
 

Glenliman

Well Known and Active Website User
VOC Member
All of the things I was weighing on the bathroom scale suddenly got a lot heavier when I purchased a 700 lb hanging scale and 90 lb Postal scale.
On careful checking, it turned out that the bathroom scale was reading way low.
The hanging scale shows a standard 998 Vincent engine at right around 220 lbs with everything attached, carbs, exhaust, the works.
Other than the belt drive, I cannot see a good way to reduce the weight of the engine very much. It takes a lot of drilled holes to equal 1 lb. You could turn it to Swiss cheese and only take off a pound or two.
Chopping the cases would cut some weight, but you must add in some engine plate weight to get some kind of gearbox back on there.

The AMC trans is quite light, but it struggles to contend with the torque of a stock 850 Norton.

Do they hold up against a modified Vincent 1000 ?
Definitely wouldn't last behind a tuned 1300+

Maybe a 6k$ TTI would.
I think the 5 speed Quaife with its 200 HP gears in the Vincent cases is the best solution, although the end result isn't light.
 

Glenliman

Well Known and Active Website User
VOC Member
It all depends where the weight is. I have ridden bikes that differ by less than 25kg and yet they feel 100kg different. I would love to lose some unsprung weight from my Shadow as it would make for a much sweeter steering and handling machine. I have thought about fitting Brampton forks as per my Rapide with coil over damper but that doesn't address the unsprung weight. Unfortunately Aussie roads are not kind to alloy rims so it is about the brake drums and sprockets.
Not much weight saving with Aluminium rims. 1lb per wheel going from chrome over steel Dunlop to Morad flanged alloys.
Buchanan Sun rims are heavier, they weigh virtually the same as stock chrome/steel rims. They are very strong though.

I haven't weighed them, but have read in mph that Bramptons and Girdraulics are almost the same weight. This was a surprise, the Bramptons look much lighter than Girdraulics.

Glen
 
Last edited:

Glenliman

Well Known and Active Website User
VOC Member
Yep, had to rework the bike and do it on a nearly empty stomach. Very difficult to think straight!

Glen
 

vibrac

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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.
 
Last edited:

brian gains

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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.
 

Attachments

Chris Launders

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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.
 
Last edited by a moderator:

stu spalding

Well Known and Active Website User
VOC Member
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
 

Latest Forum Threads

Can't Find What You Need?

Buyer Beware: Fake or Real?

Top