Who makes crankcases for commandos ?

hybridracer · Aug 5, 2024

acotrel said:
Do you base everything you do on what has happened in the past ? - I suggest that is conservative thinking. When I first looked inside my 850 engine, I thought it could never be competitive in road racing. - I learned one thing during my life -'the system runs on bullshit and if you have a victim's mindset, you will be a victim'. My mate lined up on the grid with my first race bike - he looked around at all the other bearded idiots and thought he could do alright. He immediately found out he did not know how to ride a motorcycle. When you are lined up for a race, what should your mindset be ? There are NO geniuses, everything is a development. You cannot move forward by only looking backwards.
With my 850 engine, most things depend on the way it is used. Because it's power delivery is based upon massive torque, when it is used with low gearing, it spins up without really exerting itself. It gives the appearance that it is doing it's best. When you gear it up and use close gears, you make it pull. So you use it's torque. The other thing which helps my bike, is it's steering geometry. You will never win a drag race with a Commando. The crank always tends to spin-up at the same rate.
I always seek more torque, not more power by revving higher.
When you are on a bike, if you change up too early and the bike is still fast, that is a sign there is unused torque. With some bikes when you change up too early, the revs really drop. If you get on a normal commando , put it in third gear and rev it to 5000 RPM and drop the clutch, it would probably accelerate like a jet. I did it once by mistake, I got a real shock.

Old truths still valid today -
It is the torque at the back wheel that determines the acceleration and gear change points, but the maximum power limits the top speed. The only weakness of a close ratio gearbox is at the start line. A drag race is usually won in the first second and most likely by a Commando engined bike. The torque required to accelerate the rotating parts of the power train can be calculated. An inertia type rolling road cannot measure the power/torque at the crankshaft. The clutch is not used when changing up through a close ratio gear box. A 300 lb Norton 88ss is great fun to ride. The advantages of double overhead camshaft 4 valves per cylinder engines were demonstrated in 1912 then forgotten for many decades (I thought I would put that in here).To name a few.

johnm · Aug 5, 2024

hybridracer said:
Old truths still valid today -
It is the torque at the back wheel that determines the acceleration and gear change points, but the maximum power limits the top speed. The only weakness of a close ratio gearbox is at the start line. A drag race is usually won in the first second and most likely by a Commando engined bike. The torque required to accelerate the rotating parts of the power train can be calculated. An inertia type rolling road cannot measure the power/torque at the crankshaft. The clutch is not used when changing up through a close ratio gear box. A 300 lb Norton 88ss is great fun to ride. The advantages of double overhead camshaft 4 valves per cylinder engines were demonstrated in 1912 then forgotten for many decades (I thought I would put that in here).To name a few.

Some of this I agree with some I don't.

The simple fact is if your racing you build to the class rules, the budget, the timeline, the track, the rider, your skill set and the competition. Feel free to add any thing I missed.

Statements like "the only weakness of a CR box is at the start line" are true for some places. And definitely not others.

I can tell you from personal experience that a four speed CR box on a Dommie 500 is not what you need on a track like this. Or the Cemetery circuit or most other street circuits that we run down here. If the rules say 4 speed then you need almost standard ratios to cover right angle tight corners and short straights.

hybridracer · Aug 6, 2024

johnm said:
Some of this I agree with some I don't.

The simple fact is if your racing you build to the class rules, the budget, the timeline, the track, the rider, your skill set and the competition. Feel free to add any thing I missed.

Statements like "the only weakness of a CR box is at the start line" are true for some places. And definitely not others.

I can tell you from personal experience that a four speed CR box on a Dommie 500 is not what you need on a track like this. Or the Cemetery circuit or most other street circuits that we run down here. If the rules say 4 speed then you need almost standard ratios to cover right angle tight corners and short straights.

We had loads of WW2 airfields to race on. I don’t think I would have wanted to race on street circuits. I couldn’t afford a cr box and used a Barton 4th gear pair as a compromise. The 500 Domi was always rare in the UK and in 8 years of racing I didn’t see another and the only other Domi was a 650 raced by a friend. They must be even rarer “down under”. I saw an old post of yours, about 2012 I think, and was impressed. They must be even rarer “down under”
My bike wasn’t suitable for the Vintage racing and prior to the Classic racing club the suitable classes were “singles & twin 4 strokes up to 500” and a general mix of older 4 strokes up to 800 or 900 with modern Jap stuff keeping to other 4 stroke and open classes. In other words, race what you bring.

cash · Aug 6, 2024

I was told at Engineering Tech Collage of a Frenchman who invented the offset crank in the late 1800 early 1900 his name was De Saxe. "Désaxé" (French), also means misaligned. From memory the Ariel Arrow has the wrist pin offset along with a few other manufactures ie Toyota. The offset crank helps to give the Commando it's legendary torque.

johnm · Aug 6, 2024

hybridracer said:
We had loads of WW2 airfields to race on. I don’t think I would have wanted to race on street circuits. I couldn’t afford a cr box and used a Barton 4th gear pair as a compromise. The 500 Domi was always rare in the UK and in 8 years of racing I didn’t see another and the only other Domi was a 650 raced by a friend. They must be even rarer “down under”. I saw an old post of yours, about 2012 I think, and was impressed. They must be even rarer “down under”
My bike wasn’t suitable for the Vintage racing and prior to the Classic racing club the suitable classes were “singles & twin 4 strokes up to 500” and a general mix of older 4 strokes up to 800 or 900 with modern Jap stuff keeping to other 4 stroke and open classes. In other words, race what you bring.

A photo of my bike about 15 years ago ridden by a guy called Tony McQueen.

There were at least 4 500 Dommies being raced down here in the 1998 2011 period I was racing mine. At least one is still being raced today in modified class I think. One of the bikes at the front end and competitive against most Manx Nortons. I'll have mine going by next year I think although currently busy helping friends taking bikes to this years Manx.

hybridracer · Aug 6, 2024

johnm said:
A photo of my bike about 15 years ago ridden by a guy called Tony McQueen

A photo of mine at Colerne in 1979 ridden by a friend

Dropbox

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acotrel · Aug 6, 2024

I usually start with something and do what needs to be done to make it better. I have only ever raced what I could afford. My 500cc short stroke Triton was a bike Allan Greening created, and he had a very big crash with at Bathurst in 1956. When I got it, it was a savage mishandling bastard. I improved it but what it really needed was a close ratio 6-speed box. I probably could have bought that, but motorcycle racing was not my priority back then. The Seeley 850 has loads of torque, and that is lovely -much less stressful.
When you build a race bike, you need three things - the frame, the front brake, and the gearbox - the rest is easy. Within reason, any motor can be made to go fast enough, but the rest has to be right.

Who makes crankcases for commandos ?

hybridracer

johnm

hybridracer

cash

johnm

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