Race chassis

[Michael Moore]

Frits, 2mm steel does sound thicker than needed since 50-100mm steel tube spines will usually be 1-1.5mm wall. Did you use internal bulkheads or ribs?

The CRDC monocoques built here in California were mostly 1.25mm aluminum 5052 sheet riveted structures. The article said it was T4 temper but since 5052 isn't heat treatable that was probably an error, and I suspect it was more likely to be H32.

Matweb says 5052-H32 has yield and UTS of 28000/33000 psi. 1018 cold-drawn mild steel is 53700/68000 psi.

By the time you got the steel thin enough to give the same performance as aluminum it would probably very difficult to keep it from getting dented in use unless you used a lot of shape to stiffen it.

I'd be interested in seeing more photos of the monocoque if you have them available.

cheers,
Michael

[richban]

Some inspiration from another angle. The first MTB I fell in love with. I had the pleasure of riding one of these on the 1994 Worlds HD course Vail Colorado. Epic bike from way back then.

This has elements of what I was thinking. Main frame mono with bolt on sub frame. Maybe a better option for a more modern rider position.

[husaberg]

I started with the steel butterfly below. Cut it, fold it, weld in the head stock and the bottom sheets and you're done.
I used 2 mm mild steel because I had no aluminium welding equipment at the time (1972). Not many laser cutters around then either, so I cut it by hand.
2 mm steel sheet may sound heavy, but I had the lightest, lowest, narrowest and simplest 500 cc bike in Holland; not much bigger than its 50 cc cousin.
Attachment 327961Attachment 327962

What engine powered that Frits, Suzuki 500?
edit one cylinder Maico?

Some inspiration from another angle. The first MTB I fell in love with. I had the pleasure of riding one of these on the 1994 Worlds HD course Vail Colorado. Epic bike from way back then.

This has elements of what I was thinking. Main frame mono with bolt on sub frame. Maybe a better option for a more modern rider position.

http://www.carbonfibretube.co.nz/ind...on_Tube_Prices

http://www.hexcel.com/Products/Honeycomb/
http://www.cgcomposites.com.au/Aerospace.html
http://www.nzcomposites.com/Products...Materials.html

The latest composites can be bent and shaped and glued with aradite products
Where is JasonU.

[Grumph]

What engine powered that Frits, Suzuki 500?
edit one cylinder Maico?

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....

[F5 Dave]

Mr Orr will be scoping eBay.ne or whatever equivalent as we speak.

[Grumph]

Mr Orr will be scoping eBay.ne or whatever equivalent as we speak.

ROFL - You've got a good memory Dave. Doubt Europe got the 308 V8 though....

[richban]

This was what I was thinking. Bit rough but you get the idea. Zero offset 90mm trail. 1200 to 1260 wheelbase. Ali mono frame with Tube Ali sub frame. I like how it looks.


Anyway good to get something down on paper / pixels.

[Frits Overmars]

Nearly spat my coffee all over the screen then. (500) Holy crap. Do you have any pictures of that bike? Sounds a little mental. In the best possible sense of the word.

Just a couple pictures, and not very good ones either. This is all I got.
NB: the front brake was way to small. But the bicycle bell on the left handlebar was mighty handy when manoeuvring through paddock: nobody there takes notice when they hear an engine behind them, but everyone looks around when they hear a bicycle bell .

[husaberg]

Just a couple pictures, and not very good ones either. This is all I got:

ah, Bultaco i never knew they want bigger than a 360.
What happened to it Frits does it still survive, or was broken into bits for other projects like most old race bikes?

[Frits Overmars]

Frits, 2mm steel does sound thicker than needed since 50-100mm steel tube spines will usually be 1-1.5mm wall. Did you use internal bulkheads or ribs?

I might have done with a little less wall thickness Michael, but I've got a couple of excuses. First of all, I designed that bike 45 years ago and I was going to ride it myself so it should stay in one piece. Like I said, I had no facilities for working with light-alloy, and finite element calculations were out as well. Hell, I was lucky to have a pocket calculator then.
Next excuse: lack of equipment forced me to electrode-weld the frame, so a bit of wall thickness was welcome. And finally, you cannot compare flat-section sheet metal with tubing. Tubing is about the best shape when it comes to light, stiff constructions, flat sheet is about the worst. I used one internal bulkhead; no ribs.

What engine powered that Frits, Suzuki 500? edit one cylinder Maico?

No sigar, but close, Husa. The engine came from a 360cc Bultaco El Bandido, the first Bultaco MX-bike with primary gears instead of the troublesome primary chain.
Alas, the gears caused problems of their own. Being helical, they pushed the crankshaft sideways until the bearing locating rings broke out of the crankcase.
Here are some pictures of the donor bike and engine.

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....

Yep, rotary valve and a home-made carburettor built by my friend Jos Disselhorst (he built and raced the 50 cc bike next to mine).
Why home-made? Because I wanted it to be 40 mm and very, very short. Nothing like that existed (and if it had, I wouldn't have been able to afford it at the time).
And yes, that's my Opel Rekord 1700 stationwagon in that picture. It held the 500, the 50, the fairings, the tent, the tools and the riders. The 500's front wheel between the seats served as an arm rest while driving.

[Frits Overmars]

ah, Bultaco i never knew they want bigger than a 360. What happened to it Frits does it still survive, or was broken into bits for other projects like most old race bikes?

Bultaco built a variety of 360s. Or 363 cc to be precise, with 85 mm bore x 64 mm stroke (yep, way oversquare, exactly what I would not recommend today).
Based on the Bandido engine, they also made the TSS350 roadracer (picture below), with straight-cut primary gears and a five-speed gearbox.
I had to make do with the MX-bike's four gears but mine was better in acceleration anyway .


My bike more or less survived. It's resting in my brother's haystack (because I haven't got a haystack of my own). The handlebars are missing because I used them on my 750 cc Kawasaki H2 triple.
The engine broke itself to pieces. Once I had convinced the crankshaft bearings to stay where they belonged, and the clutch to grab instead of slip, I could finally dial in some power and then the gearbox shafts got twisted to pieces, pushing the cases apart in the process. That was more than I could finance at the time.

[Frits Overmars]

This was what I was thinking. Bit rough but you get the idea. Zero offset 90mm trail. 1200 to 1260 wheelbase. Ali mono frame with Tube Ali sub frame. I like how it looks. Anyway good to get something down on paper / pixels.

That could work Richban. But since you're obviously planning to use a fibre seat, why not make a fibre tank-seat unit? It will give you a better contact with the bike than a bare monocoque. And if you shape the seat between your butt end your heels like in the Derbi picture below, you will be able to keep yourself in the saddle instead of being flung up into the air, in case of a highsider.

[Michael Moore]

Frits, I've no problem with overkill on the design since I'm not an engineer and I've got to go with "everyone else seems to think this is safe, maybe I'll make it a little safer". I have a tendency to want to triangulate everything where I imagine an engineer would look and ask what the extra 5 tubes are for. I thought that glimpse of head finning looked Bultacoish. Ducati singles can have similar problems with helical primary gear side thrust breaking the crankcase.

richban, your design looks familiar. FWIW, Tony Foale had a chance to talk to Eduardo Giro who confirmed that at least some of the frames (I can't recall if it was all of them) were welded Mg sheet, not aluminum.

If you make a combined tank/seat unit be sure it is secured better than the one on the Cosworth Norton that injured Peter Williams!

cheers,
Michael

[Grumph]

I might have done with a little less wall thickness Michael, but I've got a couple of excuses.

Yep, rotary valve and a home-made carburettor built by my friend Jos Disselhorst (he built and raced the 50 cc bike next to mine).
Why home-made? Because I wanted it to be 40 mm and very, very short. Nothing like that existed (and if it had, I wouldn't have been able to afford it at the time).
And yes, that's my Opel Rekord 1700 stationwagon in that picture. It held the 500, the 50, the fairings, the tent, the tools and the riders. The 500's front wheel between the seats served as an arm rest while driving.

I doubt if you lost anything worth worrying about by using 2mm sheet. I'm guessing that it might have finished up about 1 - 1.5kg heavier than if it was 1.6mm. Anything lighter gauge than that dents too easily and would have needed internal bracing IMO. And it still survives which a lighter gauge version wouldn't..

40mm carb was popular for big rotary valve singles...Cameron used a shortened 40mm Dellorto, as did Giro on the Ossa I think. But they were rare even new I believe.

There were a lot of those big Bultacos sold in Aussie - but not NZ - and a few were raced I believe. If you'd been in Aussie, your visually similar Holden would have had a 3 litre six in it to carry you to interstate meetings....

[richban]

richban, your design looks familiar.

That thing is so so cool Michael.

I was also thinking of running tube through the sides. As I have a habit of parting company with my bike every so often, I will need some bike and track protection points on the frame for nylon sliders. So the tube gussets would be perfect for this.

The Question is:

Will it be lighter than a Tube steel fame?

How thick does the Ali have to be?

I think a tank / seat unit is a good idea. I do like to have a tank under me.