Commando aluminum frame.

So this idea kept me awake last night, again. Another Idea that I have had is to fabricate a commando frame out of aluminum. I am thinking about some modifications to my current frame, and think a complete aluminum frame would be the way to go. Any thoughts, or orders? I have a neighbor of mine that had an Egli vincent that he was restoring for a friend. He went so far as to make 3 new frames, because the original was "hand built". He is retired and was a machinist/engineer. I have spent my entire career working on aircraft, so aluminum is my medium of choice. Plus my bike is heavy, any weight savings is great.

I am not an engineer, nor am I much of a welder. But I do know that the steel vs aluminum frame debate has been alive for years in the bicycle industry. Typically the weight savings of aluminum is eaten up by the need for larger diameter tubes and extra gussetting. If you were to keep the same dimensions as a standard frame, the implication to me would be that the original frame was over built to begin with. How would you address this?

Russ

A bare Commando frame weighs about 26 lbs. How much weight do you plan save? I would think that an aluminum swingarm and engine cradle would get you the most bang for the buck, followed by lighter wheels.

Ludgwig, we need you to weigh in here (pun intended :roll: ). You are our lightweight expert!

My complete thought was, Aluminum oil in frame, cradle with 2nd ISo. (eliminating head steady) , and swingarm with mono shock. I allready have aluminum rims, and am working up an alloy barrel. So overall I think it would be lighter, if not plain cool.

Sounds like you want a JPN monocoque!

Were the early commando's made from Reynolds tubing??

Why not go for Rickman or Seeley if you want a nice light frame!

There was a great series of article by Peter Crespin (Covenant conversion man) many years ago in British Bike Magazine (may not have made it across the pond).
He built a commando special using a cast aluminium frame/swingarm originally from a Yamaha TZ racer.
His target was 250lb all up.

Rich_j said:

There was a great series of article by Peter Crespin (Covenant conversion man) many years ago in British Bike Magazine (may not have made it across the pond).
He built a commando special using a cast aluminium frame/swingarm originally from a Yamaha TZ racer.
His target was 250lb all up.

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Yes I remember it, it actually ended up at 290lbs dry, with no charging system, lights etc I still have a copy of the final article

My 'curvy' '00 SV650 has Al frame as did the Ninja I learned tarmac skiing on.
Personally my impression is the Cdo steel frame has nice compliance that elite bikes are trying to get with slideways less rigid swing arms. Al has a definite fatigue life if built light enough to out do Steel in weight, Its a problem best seen in Al rods, bottoms are so big to take the loads, crank cases have to be milled to clear em.

To get best out of Al frame means different geometry and diminisons, similar to a monocoupe boxy frame. Sticking with isolastics also allowed lighter frames.
Recent new Al alloy announced that is very close to steel, search that for inspiration.

BTW the lightest strongest fork yokes are made of steel sheet metal, so why not frames except for easy access by eyes or hands to power plant/gearbox etc.
Commando spine is along these lines, thinner bigger OD than about anything out there. Brilliant cheap solution to me.

Personally I feel if shooting for max safe handling nothing beats a tri-linked Cdo with braced factory frame and spend most on removing mass from engine and drive train and wheels.

Personally I think industry and philosphy has shot handling in the foot. I much much prefer what feels like and articulated chassis that can twist to take up and absorb the tire conflicts in powered turns then just relaxes in one action not on and on like the elite moderns do all to easy. Personally I prefer doing corners a full gear shift faster than buzz saw sports bikes can tolerate. I've no interest in only neck and neck handling advantage invocations.

Just look at the way cars are made, thin sheet metal, no frame to speak of.

Jean

Jeandr said:

Just look at the way cars are made, thin sheet metal, no frame to speak of.

Jean

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Norton


Ossa

Yes, and that JPN weighed about 360lbs!!

Covenant Commando 290lbs including a JPN fairing.

An interesting number to calculate if you want to compare strength to weight possibilities is the material specific strength.
Divide the tensile strength by the density.

Might get some surprising answers.

Did I read some were recently that the jpn frames were stainless and not aluminium ?
Keep posting the interesting pics, because like most I to dream of building a special frame ''ONE DAY'' ,I like the Tony Foal style frames, with the back bone and and rear swing arm assemble and front engine hang from the frame, should stop dreaming and start doing.

Rich_j said:

Covenant Commando 290lbs including a JPN fairing.

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We all know Ludwig is crazy about saving weight and he has brought his street bike to about that same weight, so no need to go nuts with special frames, titanium this and carbon fiber that, just get rid of everything that is not needed, think about how to build things, be meticulous and you get a lightweight Commando.

Jean

So far I have in the not needed pile, inner and outer primary, oil tank, side covers, battery tray, swing arm ( going to be an AL monoshock design) Transmission cradle (again AL.) Frame (agail AL. with oil tank built in). I'm going to use the Nike philosophy and Just do it. I'm not going to race it, just be different. And as much as I have wheeled the dam thing around, it needs less weight. And that is without the motor. I finished up my instrument mounting today, pleased with that. And got my temporary paint on the front fender. I just have to finish re-inforcing the fairing and paint it, then the fiberglass will all be done for now.

http://i1029.photobucket.com/albums/y35 ... 143636.jpg the instruments.

splatt said:

Did I read some were recently that the jpn frames were stainless and not aluminium ?
Keep posting the interesting pics, because like most I to dream of building a special frame ''ONE DAY'' ,I like the Tony Foal style frames, with the back bone and and rear swing arm assemble and front engine hang from the frame, should stop dreaming and start doing.

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The first Norton JPN monocoque frames were fabricated from mild steel. After they decided they worked properly, the remaining ones were made in stainless steel.

Ken

A Commando at less than 300 pounds is quite an acheivement.

Bravo

Jean

Rich_j said:

Covenant Commando 290lbs including a JPN fairing.

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IS THERE MORE INFO ON THE COVENTRY? WHEN? HOW IT PERFORMED? Beautiful job - but I think you want steel because the vibes will crack the Aluminum.

See the JS monoshocker below:
more info at http://www.jsmotorsport.com (click on technical dropdown - monoshock chassis)

Read details about the Norton monoshock at:
http://users.gotsky.com/jimschmidt/racing.html

jseng1 said:

Rich_j said:

Covenant Commando 290lbs including a JPN fairing.

IS THERE MORE INFO ON THE COVENTRY? WHEN? HOW IT PERFORMED? Beautiful job - but I think you want steel because the vibes will crack the Aluminum.

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I have the original article scanned but not sure about the legal side of things, the magazine died a long time ago. Will post if it's OK - can anyone help here?

Also, I agree on the material comment, although an interesting discussion I certainly wouldn't put a rigidly mounted Commando engine in an aluminium frame and even an isolastic mounted one would be a risk.