Race chassis

[Muciek]

I have wanted to install eccentric bearing races into frame headstock so I can alter the rake angle there's plenty of space, but I'm wondering how I can do this easiest way so the forks would be pointing straight down not sideways , anybody have an idea how to do this?

[190mech]

The old CanAm motorcycles in the 70's and 80's had a replacable top and bottom eccentric that was keyed into the head tube,I'm sure pics could be found on google..

[mr bucketracer]

I have wanted to install eccentric bearing races into frame headstock so I can alter the rake angle there's plenty of space, but I'm wondering how I can do this easiest way so the forks would be pointing straight down not sideways , anybody have an idea how to do this?

bimota do it the easyist way , barrel type roller at the bottom and a offset top , only have to change to top to re offset it

[WilDun]

Although we are not talking aluminium alloy here, I have heard that going back quite a few years there were some clever old guys who were very accomplished pipe benders who just used strategic heating and cooling alone to make the shapes required.
I guess it was time consuming in a factory situation - could this technique also be applied to extruded aluminium in our situation? - it's not really clear (in the video) whether Kymco actually used a lot of force or not.

Grumph maybe you can tell us how John Britten did it with his "artistic" exhausts.

I think Neil has gained a lot of experience with aluminium alloys in his aircraft construction.

[Grumph]

Although we are not talking aluminium alloy here, I have heard that going back quite a few years there were some clever old guys who were very accomplished pipe benders who just used strategic heating and cooling alone to make the shapes required.
I guess it was time consuming in a factory situation - could this technique also be applied to extruded aluminium in our situation? - it's not really clear (in the video) whether Kymco actually used a lot of force or not.

Grumph maybe you can tell us how John Britten did it with his "artistic" exhausts.

I think Neil has gained a lot of experience with aluminium alloys in his aircraft construction.

In the short time i worked for John, the pipes i was asked to work on were cut and shut welded, not very nice. I don't know who did the later ones, I've heard that Wob was involved. It's possible that a guy here in ChCh who was heat bending filled tube for car race pipes may have done them. He certainly did some nice work for other people.
I'm sure Neil has vast experience with alloy fabrication Will. The problem with bike stuff is that for preference your frame spars are not rectangular section - usually with what is the top outer corner beveled off. And usually with at least two internal dividers running the full length of the piece too. Looked at full frame post fabrication heat treatment years ago and realised it would need to be done in a jig to maintain alignment. Which raises differential expansion problems...So the 7000 series alloys which age harden post weld are ideal. Most alloy race frames now are 7000 series extruded spars welded to 7000 series pieces CNC produced.
FWIW I've arranged to let Neil have a look at Bradley's book before it comes home.

[husaberg]

I have wanted to install eccentric bearing races into frame headstock so I can alter the rake angle there's plenty of space, but I'm wondering how I can do this easiest way so the forks would be pointing straight down not sideways , anybody have an idea how to do this?

here is a Few
https://www.kiwibiker.co.nz/forums/s...post1130370335
You are far more likely to notice a change in trial than rake.

[guyhockley]

I'm sure Neil has vast experience with alloy fabrication Will. The problem with bike stuff is that for preference your frame spars are not rectangular section - usually with what is the top outer corner beveled off. And usually with at least two internal dividers running the full length of the piece too.

According to Alan Cathcart, Mike Eatough (I think?) investigated various extrusions for the HD Superbike and concluded that none of them had any advantage over a plain rectangular tube. Packaging and/or ergonomics might dictate otherwise in some cases, I guess. John Bradley says Tigcraft used an industrial section and random-bloke-in-the-paddock told me it was something to do with truck bodywork...
One of the Paton V4 2 strokes had a frame from stacked tubes. I had a fractured, no common language, chat with the Paton bloke in attendance and they used 4 lots of 25 x 3 square to get a 100 x 25 "extrusion". I tried to ask if they did anything to the internal faces but it was beyond our level of communication. Later, I found an Italian magazine article that seemed to say it had 6mm thick webs. Material was something like Aerocordal... Roehr in the states does something similar with steel square section.
Team Roberts fabricated their frame spars from flat stock then bent with cerrobend or similar.
I'm away from computer and WiFi so this is all unverified memory, just like the old days!

[guyhockley]

I have wanted to install eccentric bearing races into frame headstock so I can alter the rake angle there's plenty of space, but I'm wondering how I can do this easiest way so the forks would be pointing straight down not sideways , anybody have an idea how to do this?

You want vertical forks?

[guyhockley]

The old CanAm motorcycles in the 70's and 80's had a replacable top and bottom eccentric that was keyed into the head tube,I'm sure pics could be found on google..

Think the CanAm, and Ducati, have larger than usual headstock's for their adjustable Gubbins?

[husaberg]

According to Alan Cathcart, Mike Eatough (I think?) investigated various extrusions for the HD Superbike and concluded that none of them had any advantage over a plain rectangular tube. Packaging and/or ergonomics might dictate otherwise in some cases, I guess. John Bradley says Tigcraft used an industrial section and random-bloke-in-the-paddock told me it was something to do with truck bodywork...
One of the Paton V4 2 strokes had a frame from stacked tubes. I had a fractured, no common language, chat with the Paton bloke in attendance and they used 4 lots of 25 x 3 square to get a 100 x 25 "extrusion". I tried to ask if they did anything to the internal faces but it was beyond our level of communication. Later, I found an Italian magazine article that seemed to say it had 6mm thick webs. Material was something like Aerocordal... Roehr in the states does something similar with steel square section.
Team Roberts fabricated their frame spars from flat stock then bent with cerrobend or similar.
I'm away from computer and WiFi so this is all unverified memory, just like the old days!

Honda always ran extruded sections for GP as well.later years.

The Fireblade from memory has a 4 internal section
The ROC frames that Roberts ended up using as Yamaha f-ed theres up for a few years were pressed in concrete formers churned out on CNC machines using a special froggy areospace alloy.
betting they never made any money out of them. carpental rings a bells as the name
The Harris frames were bent twisted and pounded with a lump hammer and lots of love by Alf Mossel.
150 seperate parts
https://www.kiwibiker.co.nz/forums/s...post1130228780
Spondon used to sorse some extruded sections for some of there later frame.
NWS made them the same as Harris.
https://www.kiwibiker.co.nz/forums/s...post1130228408

[guyhockley]

Various frame spars, mostly ali extrusions, but the small CBR600 one is steel and there are some fabricated ones, too.

[guyhockley]

Couple more including a swinging arm.

[Ocean1]

Girders are good where forces are largely in a single plane. Parallel ones are cheaper, but where loads aren't uniform they don't make much sense.

So if you're using a perimeter concept frame why would you use an extrusion instead of fabricating a beam based on the variable loads involved?

[Michael Moore]

why would you use an extrusion instead of fabricating a beam based on the variable loads involved?

If a production frame: cost. If a one off, easier construction if the extrusions are readily available to you.

[Grumph]

The GSXR frames pictured above point up how much going to the simpler beam frames saved in fabrication time - and cost.

The half - shell pressings which are then seam welded are probably cheaper initially than an extrusion - but still have to be seam welded.
Given that they can be produced in already curved form - and sized appropriate to the loads at any given point they are probably more cost effective than parallel extrusions which still have to be bent...

But later still are the current frames which are using more cast sections than before. They can be produced quickly and can be sized appropriate to loads as can be seen in the Buell ? frame Ocean put up. Bent sections can be accurately finished as cast. Fewer welds as the main pieces get bigger too. Even automated welds cost money.

Not a lot of this is appropriate to the home builder though...Unless you want to get into limited volume presswork.