Chassis Evolution

[Oggy Doggy]

Here's the less well known Ti Husky from '71.
http://www.motorcyclemuseum.org/classics/bike.asp?id=109
http://vintagemxvideo.com/profabtitaniumhusky73400.html

[Ji Gantor]

1971 Husqvarna 400cc titanium framed AMA winning bike.
I wonder if Steve McQueen got a ride?

Thanks Oggy Doggy

Ji

[NR555]

This is the Honda CR250 R 1997. The first production all aluminium framed MX bike.

Ji

And what a heap of sh*t that was.. rigid as all hell.  Remember the single radiator?  I rode one at the old Hallam MX track back to back with my trusty '93 model (just like Jeremy  and I couldn't get off the thing fast enough.  I was sorely disappointed.  I recall seeing it on the cover of ADB and being totally blown away.

You could probably blame that bike for Kim Askenazi's jail term, McGrath getting straight on the phone to Roger, curtailing Steve Lamson's career, and Everts' works version being nothing like it.

It only reinforced my mantra; never, ever buy version 1.0 of anything!

[Ji Gantor]

Yes she sure was a pig to ride.
The lesson to learn here is that the frame needs to flex even if the bike has 300mm of wheel travel front and back.

Ji

[Nathan S]

http://www.vmxmag.com.au/02_Home%20page/homepage_photos/optaco.jpg

Started looking through my VMX mags for the pic of the monocoque Bultaco. Got sidetracked with every issue, so I went to the website.
Couldn't find the info I was looking for, but found the pic...

[Lozza]

Noted motorcycle designer/stylist John Keogh has agood article in the current AMCN on this subject, but it can really be sumed up with 1 sentence.
Before/after the McCandless brothers and before/after Antonio "JJ" Cobas.
Before Cromie and Rex McCandless  designed and built the first featherbed frame. They were just variations of push bike frames. Before JJ Cobas made the first twin spar aluminium frames for a Honda RS 125(the one a very young Alex Creville won the 125 championship first year at Phillip Island) frames were just variations of the McCandless brothers featherbed frames.

[DJRacing]

Speaking of push bikes and Reynolds tubing, alot of racing bikes use 531 and more expensive bikes use 631 and more expensive again is 753. Reynolds do make a tubing for tig welding called 525 and 725.

[LWC82PE]

the articles i promised to scan are located here

http://ozvmx.com/community/index.php?topic=7274.msg70388;topicseen#msg70388

[Oggy Doggy]

Noted motorcycle designer/stylist John Keogh has agood article in the current AMCN on this subject, but it can really be sumed up with 1 sentence.
Before/after the McCandless brothers and before/after Antonio "JJ" Cobas

There's no doubting that the McCandless Bros and their Featherbed definitely revolutionised chassis design but we're discussing the progress of the motocross chassis here and it was proved pretty impressively in the mid to late fifties that the basic featherbed design had some major shortcomings when it came to motocross. Les Archer was a millionaire semi supported by the factory to develop the Manx Norton for GPs. From the mid fifties through to 1962 Les eventually chopped and channeled the initial featherbed design until he ended up with something barely recognisable from the McCandless concept. The main problems to overcome were ground clearance and more importantly chassis flex, or more accurately a lack of it. As the '97 alloy spar Honda proved, you can't have a frame that's too rigid, you need a certain amount of flexibility. While there was nothing better than a featherbed on tarmac, on the dirt it was way too rigid. Because Archers contract with Norton called for him to use Norton frames exclusively he spent the next 10 years developing the featherbed into something usable on the dirt. As photos show, the finished Reynolds 531 "featherbed" frame bore little resemblence to the original design. It was a featherbed in name only. Les won the 1956 European Motocross Championship which became the World Championship the following year.
http://www.motorcyclemuseum.org/exhibits/mx/bike.asp?id=92]]http://www.motorcyclemuseum.org/exhibits/mx/bike.asp?id=92

http://books.google.com.au/books?id=uAzl8ICKMXcC&pg=PA11&lpg=PA11&dq=les+archer+norton&source=bl&ots=3lg5mLDQHR&sig=cxJt6t6VxBs_Naeio-LKQwFkO4w&hl=en&ei=q0jgSZr1C4zW6gOLr52ADA&sa=X&oi=book_result&ct=result&resnum=1

In my opinion the Rickman Brothers Metisse design is the chassis that set the standards for future motocross design. Previous to the advent of the Metisse in 1962/3 most frames were based on road going frames. The Rickmans took basic BSA Gold Star geometry and designed a much lighter and stronger frame using lightweight 531 tubing and quality bronze welding using new flux and brazing material designed specifically for the Rickmans. The Rickman Metisse was the first chassis designed specifically for motocross and deserves its place in history.

[ksiderek]

How to bend Reynolds 531.
Step 1
Take an old plumbers pipe bender.
Step 2
Weld it to some steel rsj stolen from a WW2 air raid shelter in the army camp next door.
Step 3
Eat loads of spinach and your away 

The tube my coleague is holding is the seat rail for a Beamish Suzuki trials bike. We did loads of tube bending for many diferent people in the 70's. This also included the top and down tubes for Bengt Abergs 4 stroke Yamahas. He tried loads of diferent companies but none were able to do the job. The thin wall chromoly tube would crack when bent on modern tube bending machines. We did it using a pile of scap and muscle power ! Charged him a fortune too 

[GMC]

This also included the top and down tubes for Bengt Abergs 4 stroke Yamahas. He tried loads of diferent companies but none were able to do the job. The thin wall chromoly tube would crack when bent on modern tube bending machines.

I went through the same dilemma myself when I started building my replica's.
At first I thought I would just send the large tube out to be bent but they cracked as you said.
Then I bought some formers for my own tube bender ($700.00), did a practice run with m/s to test angles & lengths, beudy, now put in the cro-mo & the fuggin shit wouldn't budge. Obviously I don't eat enough spinach
Eventually found a Co. that was able to do it & was happy to leave the headache to someone else.

[Ji Gantor]

The attached image is of a part that is not from a motorcycle but from a drag car. It has a similar diameter to a bike frame and is subjected to similar loading. It was hand made in the States from Cr Mo 4130. It has been TIG welded and the welds are some of the most beautiful I have ever seen.

When the component was over loaded the main load carrying member ruptured near the welds. This is a typical Cr Mo failure when the load is greater than the load carrying member or when the metal has not been normalised post welding.

Ji

[firko]

Talking of aluminium frames, this would have to be one of the earliest. Lito built this aluminium framed 500 in 1966 but the bike didn't prove to be very competitive. The frame is made from aluminium tubing bonded together using Araldite and cast alloy joining sections.

[Lozza]

The new Benelli's and Lotus Elise sports cars chassis/frames are made the same way, except the join is pegged.

[Ji Gantor]

Hi Mark,
That looks like a PVC tube pool chair frame.
The front hub and fork looks like CZ stuff.
Very cool looking.
How many of them were ever built?


Ji