Commando aluminum frame.

Rich_j said:

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.

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Post the article. Legally the worse that someone could do is ask you to remove it. Chances of that are nil.

Adding lightness is one of my favorite subjects and turmoils.
Everything Ludwig said plus or rather minus the steel fork internals for Al like Greg Fauths's kit. Alloy yokes or way better yet boxed steel sheet yokes. Al kind look kwel but generally only save .5 lb d/t extra bulk mass because its fatigue prone Al.
Replace all bearing and chassis and axle spacers with good grade Al or more exotics.
Drill 1/4-1/3 out of center of axles. Replace fork caps to axle nuts with Al.
Ti fork springs if ya can to $pring for them. Oil in frame, especially a boxed sheet frame. 18" wheels and the small 325-350 size tires racers run. Tubeless is best but tricky to get spokes sealed and now apporach mass of a tube. So far Peel front tire worked fine in living room, rear is on 5th attempt of esculating sealing goops.
Al handle bars, rear sets, belt drives primary and final, are available or DIY.
In general necked spoke Al or Mg rims beat mass of cast wheels only some out in orbit expense one piece wheels beat old school and then often such short life time they must be replaced like tires. 2-1 exhaust saves almost haft systems mass. DO Not use Al spoke nipples.
Isolastics-chassis allows low BF crank that saves mass that is noticed in seat of pants response and road flinging, which is the whole point of removing mass ain't it. Al box stock swing arm is cat's meow back there for Ms. Peel.
No fenders of course but grit blast even w/o water becomes an issue in real life.
Z plates are over built but hardly a couple oz lost to drill out but shows you care.
Slice off the back haves and remount exhaust with few oz less involved.
About every steel bolt can be drilled and head trimmed for a few more total oz off.
4.5 lb = 1 hp in get go or whoa!

Clever designs this thread brought to light, thanks.

hobot - shooting for 1 hp/4 lb bike-6 gal gas, 2.5 qt oil + pilot + crash bars.

Rich_j said:

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.

Click to expand...

Click to expand...

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.

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First post here - messing with Jags these days though still commute on a Triumph.

FWIW the Covenant Commando is alive and well (or as well as any bike can be with a K2FC that hasn't been cleaned for 20 years). I have a pair of three-spoke mag wheels and tubless tyres that will bring the weight down by about 15lbs plus a set of magnesium Amal Mk2 concentrics to save another pound or two. Nice to see people remember it. Of course by now belt drives are ten a penny but nobody made one in those days. The Covenant Fork Conversion is still done bt RGM apparently, not that I've ever had a penny from them.....

Pete Crespin

Hi Pete,

Good to see you're still around! I remember it well!!

When we planned the "C652" Norton in the late 1990s I discussed frames with Dave Pearce/Tigcraft and Lester Harris/Harris Performance. Both agreed a steel frame, propperly constructed, will not weigh an ounce more than an aluminium frame. Both agreed aluminium was more a fashion thing than of technical advantage. Add to it aluminium frames tend to tire (get soft with age), that a steel frame can be repaired more easily, and looks nicer in my opinion because it is less obtrusive, you can guess what frame the bike ended up with.
I have since had no reason to revise my opinion.

Hi guys- I am not an engineer or any kind of expert, hence my need to 'weigh' in here
In another lifetime I did some work requiring light structures- and I found that it helps me to think in terms of percentages of savings, that is, how much lightER can I make it? So if I can reduce the weight of an individual component by 15%, that's a pretty good savings. For example, the Z-plates are overbuilt; but with the proper drilling, and THINNING of the plates (like the thinner aftermarket plates available) can you save, say, 10%? Not bad. It all adds up. Second, I haven't the foggiest about steel v. aluminium, but (gasp, shudder) Ducati has made a pretty good living off of the trellis approach, and I have used the trellis approach to some other projects with great success. Hard to beat the triangle for stiffness and lightness. One last exotic thought: if you must have a headlight, there are lithium ion batteries that would fit inside the headlight shell and weigh a few ounces. Need a small circuit/cutoff to prevent overdischarge, but still, a few ounces to be streetable is pretty good.

Great project idea- good luck!

ZFD said:

When we planned the "C652" Norton in the late 1990s I discussed frames with Dave Pearce/Tigcraft and Lester Harris/Harris Performance. Both agreed a steel frame, propperly constructed, will not weigh an ounce more than an aluminium frame. Both agreed aluminium was more a fashion thing than of technical advantage.

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That's all true if you are comparing like with like. But since you can do things with aluminium that you can't do with steel, there'd be little point in trying to replicate a steel frame in aluminium. The Terry Shepherd frame used on the Covenant Commando is basically a hollow cast box - try that with steel. His original intention AFAIK was to dispense with the petrol tank on TZ 250/350 bikes for short circuit racing, as well as beat them on rigidity and therefore handling. Remember the Japanese bikes were quick but not the best handlers in those days. Personally, I wouldn't want to run the bike without a wider tank between my knees so it's used as an oil tank only.

I am always sceptical of people's claimed weights for British bikes. If you simply add up the various components such as wheels, tyres, tubes, forks, frames, engines etc you can see what a joke some of the claimed weights are. My inspiration was Alastair Laurie of lightweight triple fame. He was absolutely meticulous in measuring everything. Francis Beart was another influence and another perfectionist from an even earlier era. In the end, not wanting to use exotic materials, I was happy with what the Covenant Commando weighed, considering the massively heavy but oh-so-period wheels. It came out around the same as a normal Interstate minus its engine and gearbox. Wheeling it around you'd swear it was a bare frame, not an 820cc bike. No danger of anything cracking as the box section and fixings are so massive. Not the world's most refined bike, but the monoshock is very comfy.

For those who might remember him, Nutty Slack from that era is about to re-emerge as 'Jaguar Joe' in an E-type restoration book I'm finishing off at present. E-types are very like bikes. Tubular frames, spoked wheels polished alloy covers, alloy head, multiple carbs etc.

Pete:

I am a bit surprised that no one has yet mentioned titanium. It is stiffer for a given cross section than steel or aluminum. Of course, there are a few problems, naturally, nothing that can't be handled with access to inert atmosphere work boxes and disposable machine cutting tools (titanium galls VERY readily).

Teledyne manufactured a titanium frame bicycle; my racing acquaintances preferred steel (more flexible) or aluminum (stiffer), but I only knew a few of them. The headset had to be press fit hardened steel.

As nice as Titanium is, I am working on an aluminum budget. I've used some Ti on airplanes, it sucks to work with. I have a few Ti parts, Valves and keepers, I aquired on e-bay, ex NASCAR stuff. Nice stuff, great price. Just have to mod them a little, mostly length. the stem size is the same.. And I have enough to do my yamaha.

Frank S said:

I am a bit surprised that no one has yet mentioned titanium. It is stiffer for a given cross section than steel or aluminum. Of course, there are a few problems, naturally, nothing that can't be handled with access to inert atmosphere work boxes and disposable machine cutting tools (titanium galls VERY readily).

Teledyne manufactured a titanium frame bicycle; my racing acquaintances preferred steel (more flexible) or aluminum (stiffer), but I only knew a few of them. The headset had to be press fit hardened steel.

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Im pretty sure you will find that steel is stiffer than Ti, approx 208 GPa vs 116 GPa. As has been mentioned steel and aluminium end up being almost identical in mass but will have slightly different flex characteristics. If you did want to get radical carbon fibre would be the way to go, ultra high modulus carbon can be greater than 450GPa

Yep can compare dimensions of Steel vs Ti rods to see Ti must be bigger size to handle same loads. Strongest lightest chassis and fork yokes are sheet steel box structures. Now it temps rise into 1000's of degrees Ti is way to go ie: SR71 Blackbird.

In terms of modern materials carbon is far superior to anything used in the past, and was first used for MC frames back in the 1980s by UK manufacturer Armstrong on their tandem twin race bikes. Currently carbon frames are being used by Ducati on 2011 works race bikes, and many MotoGp bikes have been using carbon swinging arms for quite a while.

Ti frames were first used by BSA on their works MX bikes back in the 1960s, but they had an awful lot of problems with these, and in effect the use of the Ti frames lost them the World MX championship, which they had won the year before. There have been a few more recent one off special Ti frames made for competition use, but not sure if there have ever been any production ones?

Wasn't there an aluminum monocoque chassis JPN built back in the waning days of Nortondom?

IIRC first monocoup was a Norton twin in steel plate then SS.
Here's review of types of most frames and common materials.
http://www.ehow.com/list_7611776_motorc ... tyles.html

Trouble with carbon fibre besides creating hard points for attachments is is brittle and too often to build to point of mass advantage over other material it comes with a use by date this discard. Wheels are known issue especially if loaded hard.

i bet a sheet metal boxy frame in 4130 chromemoly steel would be hard to beat for a long time to come or until spider silk ceramic frame and wheels come online.
http://en.wikipedia.org/wiki/41xx_steel

Only limited production TI frames. I have been involved in building these bikes for a few years. All TI frame with carbon fiber wheels and bodywork. Under 450 lbs with 2.3 liters EFI and a blower for 200 horse at 7000 RPM . What a grin to ride. Talk about torque. We are gearing up for another build this spring. Jim

Yes sir Cosmo, that's what I seek to best in mass to power and torque ratio with biplane technology built in living room. Them Harleys if lifted some sure can corner though.

hobot said:

IIRC first monocoup was a Norton twin in steel plate then SS.
Here's review of types of most frames and common materials.
http://www.ehow.com/list_7611776_motorc ... tyles.html

Trouble with carbon fibre besides creating hard points for attachments is is brittle and too often to build to point of mass advantage over other material it comes with a use by date this discard. Wheels are known issue especially if loaded hard.

i bet a sheet metal boxy frame in 4130 chromemoly steel would be hard to beat for a long time to come or until spider silk ceramic frame and wheels come online.
http://en.wikipedia.org/wiki/41xx_steel

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Thats contrary to what Armstrong found when they used carbon frames on their race bikes back in the 80's! Sheet metal frames were used on production machines from the 1960's, and not sure whether or not 4130 sheet would work any better than the magnesium sheet that was used by Mc Claren (FI builder) to make a limited run of Suzuki trials bikes in the 1970s?

The only real disadvantages of carbon are cost, and the fact that its not really a material that is as "idiot proof" as steel or aluminum, and therefore only really suitable for serious race applications.

OK thanks for setting me straight Carbonfiber. Personally I think Norton steel tube is just right with the 3 links, seems to dampen stocks and twist like an anti-sway bar that takes out / adapts to the tire vector conflicts w/o any springing just single unwrap to neutral. Moderns can have their stiffer and lighter frames but for the life of me I don't think it matters in a linked isolactic Commando, just needs more power to make up for a few extra lbs in bee line sprints. Any who what kind of reaction would the world have if a quaint ole Commando beat their best times around various tracks? Will be fun finding out one way or another.

The Norton isolastic chassis is very well matched to the motors, but not sure how well it would handle with 150BHP at the rear wheel, which is what a modern 750cc race bike is likely to be making?

hobot said:

IIRC first monocoup was a Norton twin in steel plate then SS.
Here's review of types of most frames and common materials.
http://www.ehow.com/list_7611776_motorc ... tyles.html

Trouble with carbon fibre besides creating hard points for attachments is is brittle and too often to build to point of mass advantage over other material it comes with a use by date this discard. Wheels are known issue especially if loaded hard.

i bet a sheet metal boxy frame in 4130 chromemoly steel would be hard to beat for a long time to come or until spider silk ceramic frame and wheels come online.
http://en.wikipedia.org/wiki/41xx_steel

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If you want a really strong steel try maraging steels.... http://en.wikipedia.org/wiki/Maraging_steel
amongst other things the problems with these type of steels is that to build a light stiff frame you end up with bigger diameter (2nd moment of area) section and thinner and thinner wall sections, you then end up with localised buckling limitations as well as a distinct lack of weldability.

The biggest problem with carbon is the general lack of understanding of it. Being non-isotropic is one of its distinct advantages yet it is hard for a lot of people to visulise load paths and how they are transmitted through a structure, especially when you get into non symmetrical laminates.