Bike Weights and Weighing

Pushrod Twin

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TTI boxes are great, I visited the factory a couple of years ago, they are 80 miles away from me. Bruce is a nice guy and his team are enthusiastic. I too would fit one if my Commando boxes wear out.
 

greg brillus

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Thanks for the figures David, the numbers are quite amazing. My racer runs a 6 speed TTI box which is just the best......I can shift up through the gears as fast as I like with no issues at all, it is entirely predictable. I have sold the original engine and ancillary parts to a fellow Vincent man and racer, he is also interested in the gearbox which I would replace with a 5 speed in magnesium for the small extra cost. As Roy said, Bruce and the team at TTI in Nelson New Zealand are very helpful. The gearboxes are very strong, they run their own specific output sprockets which are not interchangeable with the AMC style boxes, I think the spline is larger. My frame comes back from the paint shop hopefully this coming week, then the reassembly will begin, this is a genuine Slimline frame with a later swing arm. I use longer back shocks and use a 30 mm spacer under the top yolk, with a longer steering stem to change the steering angle. This helps the bike to "Turn in" on corners much better.
 

davidd

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It's a small photo, but this is a comparison of the mainshafts:
amc_gearbox_comparison_(thumbnail).jpg


David
 

Bill Cannon

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If u check yr bathroom scales by say 5, 10, 30 kgs plus all weights, each time u use yr scale for yr bike, u will
know the deviation factor or "bathroom-factor". What I found out by weighing my Norvin: It had the same
weight distribution, like my Honda RC31 (650 Hawk), which - in my opinion - is the best road holding bike
in the 60hp class. These bikes have a lighter front wheel load, than rear, and this seems to be for the changing
load with braking. If u study modern superbike tests, like BMW 1000RR, Honda CBR1000RR, etc. , they all have
heavier front wheel loads. I asume, that this is for compensating the aerial lift at speeds over 140mph, to keep
these bikes steady at full throttle on the motorway. As we do not have this kind of lift with our bikes, they
should not have the same weight distribution, like modern Super Bikes, to submit an enjoyable ride at lower
speeds, even on track. In other words, a good Vincent, on road or on track, should have abt 40% load on the
front and 60% on the rear. Original brakes in good nick are fine on a Comet, but will need some improvement
on the front with twins.
Don't forget friction is directly proportional to load, so weight on the front gives extra front tyre grip allowing more cornering power and stronger braking.
Cheers Bill
 

Monkeypants

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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.
Roy told me that he has blown up more than one of these Triumph 5 speeds. They are said to be a lot stronger than the AMC .
One of the fellows on the Norton site runs a modified 850. It's 910 cc and makes maybe an extra 15 bhp or so, which he uses.
He has broken stock AMC transmissions with that one. He's got a TTI in there now, it's holding up.

On the question of weights, how does the 280lbs of a Comet racer compare to the weight of a roadgoing Comet?
Would the racer be approximately 100 lbs lighter than the roadbike?

Glen
 
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davidd

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Glen,

I think that is about right. The Flash was billed around 330 and it was probably around 340. The street Comet was 390. I weighed a stock street Comet once and it was 400 lbs.

David
 

Monkeypants

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My next question is, how does one reduce the weight by 120 lbs while retaining Vincent frame members and Gridraulics?
I have an ulterior motive. I would like to chop some weight from my Rapide but still have it look like a Rapide. Surely some of the tricks used on the Comet racer could be applied to a Rapide?
Here's my list to date. Some of it has already been done but hasn't amounted to much weight reduction.

-Alloy head brackets- big weight saving possible here.
-Armours silencer to replace Spares Co Spiral baffle- done
Alton to replace dynamo- done
-Replace rear stand with Alloy version s that will only be a fender brace ( Dave Hills stand in place)
-Alloy rims- done
-Lightweight horn to replace heavy Altette - done
-Newby belt drive
-Alloy engine plates
-Remove front stands- done
-Lightweight ignition housing instead of magneto- done
- Alloy fuel tank
- remove ss crash bars
- replace ss and steel fasteners with titanium
- replace ss fenders with alloy version

I'm sure there is more low hanging fruit, but that's the easy stuff that comes to mind ( other than the Newby drive!)

Glen
 

Robert Watson

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Titanium oil tank
Keep the side stands but drill them up the middle.
Make almost all your fasteners from alloy
Alloy brake drums with cast Iron liners
Alloy brake arms.
Alloy brake rods
Alloy fender stays
Alloy spoke flanges
Drilled and tapped hubs with socket head cap screws and no nuts
Get a new set of lightweight leathers
switch to a beanie helmet
Notice I have said nothing personal here
 

Monkeypants

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Way past that Mike, I'm using a digital hanging scale now. And it's painfully accurate!
My Rapide with the rack and Top box is 507 lbs with 1 gallon of gas in the tank. That includes travelling tools.

Glen
 
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