Purity of design...

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A few years ago after a British Motorcycle Owners Club meeting we rode to a local cafe for a coffee. I was on my Vincent with my girlfriend on the back. My friend Chris was right behind me on his Ducati Panagale. We got to the cafe, and Chris said, wow that Vincent can really accelerate. I am pretty sure the Panagale has about 170 HP and the Vincent about 60 HP, but the Vincent gets going right away.

My bike is pretty standard and it easily does 100 MPH in third gear. I am not sure how fast it can go in fourth. The only mods are 8:1 pistons (standard late Shadow spec) 105 cams, and 34mm carbs. I does tend to leave other bikes behind. I have a 900ss Ducati 1975 and it is way faster than the Vincent, while having some similar power characteristics, I am sure the Panagale has double the power of my 900ss but still the Vincent has the grunt to get going really quickly.
 
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I've got a real nice old 650 BSA that has 1 more claimed bhp than a Rapide.
It's a nice looking bike, I enjoy riding it, but to quote John Mcdougall, " it ain't no Vincent" Put a passenger on board plus luggage and it is pretty slow on mountain passes.

A lot of old bikes don't quite measure up to the period road test hype. The Vincent is one that , if anything, outperforms expectations.
Somehow it's more machine than the sum of its parts.
I find that the detractors have never even ridden one, much less owned one long term.

Glen
 

Fast Eddie

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On top of your points Glen, many Vincent’s did huge mileages. My own had done 132,000 miles by 1962. How many it had done in total by the time I got it in around 2000 is anyone’s guess.

Prices of old used Vincent’s plummeted in the late 60s and through the 70s. That put a lot of heavily worn out Vincent’s in the hands of many who’s enthusiasm outstripped their means. Seems to me that’s when much of the ‘problematic’ folklore was born.
 
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All of this and warm sunny weather (55f) here got me going.
Just had to go for a ride and enjoy the two Phil's creation all over again!

 

p400

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Crawdad harvesting near a 1947 Rapide

20130619_140653.jpg
 
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The rear shock in my photo is a Koni.
I'm not sure what brand the coil-over shock is in the above photo.
Maybe an AVO?

Glen
 

p400

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The 47 Rapide shock pair were a custom Vincent build from Works Performance. I dont think they, WP, are offering this Vincent pair any more. Too bad cause they work well for me.

WorksVN-44003side.jpg

VN-44004 WP part number for the pair.......order/purchase year 2007
 
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Fast Eddie

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The 47 Rapide shock pair were a custom Vincent build from Works Performance. I dont think they, WP, are offering this Vincent pair any more. Too bad cause they work well for me.

Yes, they certainly look like they’ll work a lot better than the stock stuff!

You weren’t tempted to put something similar on the front too?

I had Thornton stuff on a Vin once (dunno if they’re still going), the dampers worked well, but the springs really messed up the ride hight. I ended up keeping the dampers and fitting Godet springs, that sorted it.
 

p400

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The threaded body spring preload allows for height, also allows different spring selections,
I have adapted to the Bramptons as stock setup. I have several Girdraulics to compare and Girdraulics are nice.
But Bramptons rule.
 
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It's not horse power that counts its engine torque that gives it grunt.

How much grunt remains depends on how high you raise the overall gearing, and a close ratio gearbox will help most bikes accelerate faster, because you ride the top of the torque curve. The correct gearing is where the motor just continues to pull at the end of the longest road. If it runs out of puff, the overall gearing is too low.
 
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How much grunt remains depends on how high you raise the overall gearing, and a close ratio gearbox will help most bikes accelerate faster, because you ride the top of the torque curve. The correct gearing is where the motor just continues to pull at the end of the longest road. If it runs out of puff, the overall gearing is too low.

Or if you get the gearing just right, because the bike has run out of its power, and is incapable of running /pulling a higher gear ratio. Unless one day you have a 20mph tailwind. ( by changing rear wheel sprocket)
 
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A surprising number of people are talking about a lot of engine torque needed for acceleration. An engine has most torque at lower revs. As revs goes up, horsepower goes up a and torque goes down. To overcome this a gearbox is fitted. Rear wheel torque multiplied by gear ratio. Ever tried to accelerate at low revs with much engine torque on top gear? Not much rear wheel torque.
On gearing and close ratio gearboxes. That depends on the intended use of the bike. For road racing with a short power band, close ratios prevents going off pipe upshifting. Overall gearing set for max rev just before braking at the longest straight. When fairings became common, increasing top speed about 10 Mph, you had to slip clutch excessively in the hairpins. So 5 and even 6 speed gearboxes became common to get a lower first. The main obstacle for speed is wind resistance. To get best overall result, progressively less ratio difference going up through gears. As an example of this, when I designed a 5 speed gearbox for BMW racing outfits, riders requested a 800 rpm drop when going from 4th to 5th.
Quite different on a road bike that shall work both on roads and in cities. Ever tried a Goldie with close ratio gearbox in congested traffic? A while ago, I had a discussion with an Inter owner about which gears he should put in the box. There is a couple of sets to choose from. With current speed limits, most riding will be at less than 60 Mph. So 2nd and 3rd sets for best acceleration overtaking heavy trucks was chosen. A fairly high gearing on primary and final drive will keep revs low (less vibrations) for touring.

Another issue. Horsepower figures mentioned by Vincent and other manufacturers. I've read that Vincent had an accurate dyno on loan for the drone engine project. Probably more accurate than their own. So the Vincent mentioned figures is believed to be fairly correct. If other marques horsepower figures came from the engineering or the marketing department is a question not yet answered.
 

Fast Eddie

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There are many stories (inc from Norton) about HP figures being set 1-2 HP above the competitors claim. Of course, if the competitors did the same before that, and before that, and so on, we end up with daft figures... like 65hp for a stock 750 Commando (for example) !
 
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When Norton built the Manx, every engine was braked. It had to exceed a certain limit before put in the frame and delivered. Mine, according to factory records, was built in a batch for John Surtees. They differed a bit. I guess John got the best one.
 
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