Race chassis

[Michael Moore]

Here's a Scorpion off-road bike from the early 1960s with a welded steel box frame. Don Morely says the designer, Paul Wright, was a race car chassis designer. He lists the weight of the frame as 11 pounds. With a standard iron barrel Villiers trials engine the bike was under 200 pounds. There is no mention of sheet thickness.

cheers,
Michael

[richban]

So after not much thinking I am going to build it. For no better reason than there is not one on the track here I know of. And I also need 2 light and nibble bikes to compete at the front. 50 and 90 AM6 engines.

Sketchy has kindly offered to put the frame through his fancy software to test safety / stiffness. Also the weight calculations of the frame and swing arm. So we can try different thickness Ali and see how we go on the computer before cracking into building. He has also recommended a good grade of Ali to use. Helpful chap that Glen.

I will now try and figure the foot peg and engine mounting then send it off to Glen for analysis. Work on top view in 2D and the swing arm.

If it all works out I would like to publish a cutting pattern for anyone to have a crack at.

2 important things missing are the front forks and rear shock.

I think RS125 front forks would be the simple choice.

I found these the other day as well.

[Michael Moore]

richban, in Volume 2 John Bradley mentions the Foggy Petronas superbike frame is made from 2mm 5083-O sheet and the swing arm is 2.5mm. Other parts are turned from solid (presumably also 5083). Filler rod is 5356. He says 5083 is reasonably formable in H12 and "just" formable in H14. It does work harden quickly which is why O temper was chosen for the pressings. He thinks the alloy is underutilized for motorcycle applications. 5083 also has very good fatigue characteristics.

So you might keep that in mind as a starting point for your frame.

cheers,
Michael

[Grumph]

And in NZ 5083 is used a lot for boats.....but not common under 3mm thickness.

[Michael Moore]

If he went with the 2.5mm as a nice safe number for the frame material then having to use 3mm is a 20% weight disadvantage, but that might only be a pound or two. If he got serious he could attach the sheet with a belt sander. The peace of mind from the 3mm might be considered a plus.

A big industrial supply place here has 5083 sheet with .125" (+/- .007") being the thinnest they offer. They do go up to 1" plate for making machined bits. But they are stocking convenient sizes for quick ordering, I've not checked with an actual metals house to see what might be available from a specialist.

[jasonu]

If he went with the 2.5mm as a nice safe number for the frame material then having to use 3mm is a 20% weight disadvantage, but that might only be a pound or two. If he got serious he could attach the sheet with a belt sander. The peace of mind from the 3mm might be considered a plus.

A big industrial supply place here has 5083 sheet with .125" (+/- .007") being the thinnest they offer. They do go up to 1" plate for making machined bits. But they are stocking convenient sizes for quick ordering, I've not checked with an actual metals house to see what might be available from a specialist.

Availability may just make the call for him re. material type/thickness.

[F5 Dave]

I love a bold approach Richardson. Look forward to seeing the results.

In that vein WP made a single sided linear bearing fork . That would be a fun project too.
Never seen on a bucket. How can you resist?

[richban]

I love a bold approach Richardson. Look forward to seeing the results.

Ha ha. Well I did do some more drawing. The more I draw the more problems there are to overcome. As you will notice. I sort of start with what I think looks cool then slowly the practical problems dictate the design. When the new AM6 engine arrives I will be able to change the frame to suite the mounting points on the engine. Anyhow, these are just thoughts on paper at the moment. Turning circle will be a little limited I think. But hey, it will be so light i will just pick it up and point it where I want.

[F5 Dave]

Ha. Autocorrect. Richardson.

[husaberg]

Here's a Scorpion off-road bike from the early 1960s with a welded steel box frame. Don Morely says the designer, Paul Wright, was a race car chassis designer. He lists the weight of the frame as 11 pounds. With a standard iron barrel Villiers trials engine the bike was under 200 pounds. There is no mention of sheet thickness.

cheers,
Michael

The Norton comando JPS was made in Stainless steel i have what the gauge was somewhere.

No carb visible - rotary valve ? If that's an Opel in the background it points out just how close the Opel and Holden of the period were....

Why did we miss on these
Opal GT 1972

I have no idea what GM platform its based on if it even is, Maybe chevette, Gemini or the earlier Isuzu bellet?
What did we get from GM then HB torana and Viva.
How common were the opal GTs in Euroland Frits.

[Ocean1]

Why did we miss on these
Opal GT 1972

I have no idea what GM platform its based on if it even is, Maybe chevette, Gemini or the earlier Isuzu bellet?
What did we get from GM then HB torana and Viva.
How common were the opal GTs in Euroland Frits.

It's a kadett. I had one in London, nothing special. The Manta was a better machine.

[Grumph]

Why did we miss on these
Opal GT 1972

I have no idea what GM platform its based on if it even is, Maybe chevette, Gemini or the earlier Isuzu bellet?
What did we get from GM then HB torana and Viva.

Kadette was I think same pan as HB Viva - which stretched a bit gave us down here the Torana 6 - then the fire breathing XU1 version - then the two prototype XU1 V8's....

This is actually very similar to what Rich is looking to do - first a 50, then a 90, then a fire breathing 300 twin.....

[husaberg]

Kadette was I think same pan as HB Viva - which stretched a bit gave us down here the Torana 6 - then the fire breathing XU1 version - then the two prototype XU1 V8's....

This is actually very similar to what Rich is looking to do - first a 50, then a 90, then a fire breathing 300 twin.....

Thats speedpro's punchline.

It's a kadett. I had one in London, nothing special. The Manta was a better machine.

thought the kaddet was the chevette/Gemini/
edit maybe not
https://en.wikipedia.org/wiki/GM_T_platform_(1973)

edit again oh i see there were two versons of the kadett
https://en.wikipedia.org/wiki/Opel_K...2.80.931979.29

[Ocean1]

thought the kaddet was the chevette/Gemini/
edit maybe not
https://en.wikipedia.org/wiki/GM_T_platform_(1973)

edit again oh i see there were two versons of the kadett
https://en.wikipedia.org/wiki/Opel_K...2.80.931979.29

Aye, individual marque model design got more or less submerged in badge engineering, (design by accountants) from about then onward.

The 1900 engine was the basis of the Holden Torana unit sold here, having been completely neutered for no adequately explained reason.

[husaberg]

Aye, individual marque model design got more or less submerged in badge engineering, (design by accountants) from about then onward.

The 1900 engine was the basis of the Holden Torana unit sold here, having been completely neutered for no adequately explained reason.

Have a read up what GM did to the Cosworth engine made for the Vega one day
Neutered by stupidity.

In April of 1974, just one month before the planned introduction, two of the three engines in the Emissions Certification test cars burned exhaust valves by the 46,000-mile mark, just before reaching the 50,000 mile limit (PDF) marking the end of the test. The third car was withdrawn from testing and a teardown of its engine revealed incipient exhaust valve damage as well. Bill Howell, of Chevrolet Product Promotion (aka Chevrolet Racing) and a fellow Cosworth owner, who together with Herb Fishel spent hundreds of dyno hours developing Chevrolet�s version of the Cosworth Twin Cam engine, twice criticized the decision that led to this failure.
In a rare moment of candor, when among a small group of Cosworth Vega enthusiasts in Akron, Ohio, he attributed the emissions test failure debacle to an irrational decision to run the timing substantially retarded on the test cars in an effort to provide a safety margin in the emissions numbers. That decision, which he had strenuously but unsuccessfully opposed, made absolutely no sense to him, and left him bitter. As he predicted, it dumped excessive heat into the exhaust valves and seats, and they predictably failed. He was convinced from all of his dyno work on the engines, and based upon all of the knowledge he had amassed during his impressive career, that they would have passed emissions with the timing properly advanced.

http://www.cosworthvega.com/cosworth_vega_history.html

Then again maybe the bock wouldn't have outlasted the valves

That Mike referred to the EAA, the Chevrolet Vega, as 'the stumbling block' was perfect, for the phrase amply sums up the debacle.
"It was extremely light compared to the BDA with its pressure die-cast aluminium block from Reynolds, but was not up to the ratings we were putting through it. Designed to be a two litre racer, we could not make the cylinder block live. There was nothing we could do."
" It started as a race engine with Chevrolet, dry sump, the whole works, and it was Chevy who productionised it for the Vega car, They even had problems with the engine in road trim just as they did with the standard engine. The project died but they are now collectors' items!"
Thus the first road car to carry the Cosworth name did not enhance any reputations. It was not the engine which was at fault, only the block, but that tends to be somewhat critical and the whole episode fated before it began. Hundreds of blocks were being delivered, many failing a pressure test Cosworth devised for them and littering up the place while a solution was found. It never was.

http://www.cosworthvega.com/the_cosworth_story.html

http://www.italian.sakura.ne.jp/bad_...th/index4.html