Aluminium Swingarms

[el chupacabra]

Hello, I’m after some info as I want to build an aluminium swingarm for a bike.
I am wanting to know what the professionals use and do (for their one off gp builds and mass production if known). What I do know is:

I can use 5083 and form the entire thing out of sheet and plate (difficult/time consuming but it is readily available and require no post weld treatment).

I can Buy 6082 extrusion and use that in combination with 5083 sheet but I will have a severely weakened HAZ from the welds and will need to heat treat the part back to t6 but risk warping the part. (Am I just over thinking and should I just over engineer the part in 6082?).

I could get some exotic 7000 series from overseas and make the swingarm without any post weld heat treatment but at god knows what cost.


Up to this stage I’ve made a few steel chassis and modified an aluminium cradle for an RGV250 engine swap, I’ve also cast an engine from scratch. So I have no problems with the fabrication more the design/engineering involved.

Thanks

[Grumph]

Dave Pearce who builds the Tigcraft frames uses mainly 6082 or 6061 with 4043A filler. He's not found any post weld heat treatment necessary.

[jato]

For what it's worth i built one for my bucket years ago from 6060 (90% sure it was) but while it looked the part a near highside or such would have it twist out of shape. checking it with straight edges etc would show it had moved in the welded areas... I decided then should i ever build another it would have the right materials and heat treatment. Pressed out of 5083 could be the answer - a lot of work though building dies etc... is it for the 350 ?

[husaberg]

NWS and Harris used H30 sheet heat treated Which is 6082) (I didn't know that)
https://www.kiwibiker.co.nz/forums/s...4-Race-chassis

https://www.kiwibiker.co.nz/forums/a...8&d=1325803886
https://www.kiwibiker.co.nz/forums/a...9&d=1325803921

https://www.kiwibiker.co.nz/forums/s...chassis/page10

[el chupacabra]

For what it's worth i built one for my bucket years ago from 6060 (90% sure it was) but while it looked the part a near highside or such would have it twist out of shape. checking it with straight edges etc would show it had moved in the welded areas... I decided then should i ever build another it would have the right materials and heat treatment. Pressed out of 5083 could be the answer - a lot of work though building dies etc... is it for the 350 ?

Not for the 350, that project is finished, other than a dyno tune when I get the time. I have an RG150 kicking around with some wider wheels, I want to make a chassis and swingarm for it with 125GP geometry and make a kind of poor mans 125gp bike. I’ll probably make a pipe, tank and custom head for it too. Then I want to do something more ambitious later on.

Looks like I’ll be using a combo of 6082 and 5083 then with some 4043 filler.

[husaberg]

you might not have to import
http://highgrademetals.co.nz/aluminium/aluminium-7075/

[el chupacabra]

It’s a shame they only have round bar and plate

[husaberg]

Sheet as well
https://www.aircraftlogistics.co.nz/...--1791807038=9

[jato]

"Not for the 350, that project is finished" well done! its easy to start a project but finishing them takes real resolve...
I'm pretty sure that 7075 can't be welded. could be wrong.

[Grumph]

Mico Wakefield list a lot of tube and sections in 6060. That's easily weldable and pretty ductile too. When I've had to brace or alter factory arms that's what I've used. It's ductile enough that without additional annealing I've pressed it into carb bellmouths.

[husaberg]

i found this from Flet

Bike frames (pedal) were made from 7000 series but it's fatigue resistance was not as good and older 7000 alloy bikes were not worth owning, they all cracked sooner or later. On the other hand 6000 series frames, although a little heavier, have much better fatigue resistance. many early units are still operating.
I wouldn't bother with 7000 series frames, just (expensive) trouble waiting to happen.
Interesting to note that all our Gyro Copter rotors, rotor heads and frames are all still made from 6061 T6. Frames and Rotor heads are bolted together with the rotors being bonded (and bolted at the hub also)
6061 T6 is good all round performer.

Honda MX Frames are 7005 and it says to use a 5356 welding rod (According to HRC)

Why not cut up a frame and use the special sections ala cbr or Fireblade
https://www.kiwibiker.co.nz/forums/s...post1131043875

[el chupacabra]

"Not for the 350, that project is finished" well done! its easy to start a project but finishing them takes real resolve...
I'm pretty sure that 7075 can't be welded. could be wrong.

Thanks. Well, hopefully I can bring myself to take it out on the track sometime soon after putting in all the effort.



All I was really worried about with the 6000 series was the post weld strength, as it’ll eventually only age back to T4. After reading that it looks like 7000 series is off the cards. I’ll probably just use 6082 and make it a bit thicker than I’d think is necessary.



I quite like the Kobas style swingarms as they will mount similarly onto the rear engine mount for the RG150 and between the frame spars. I wonder what grade they are. Although they look like they are just constructed from extrusions.

I could press up a piece of channel from 5083 in a small die and weld it into a box and come up with something like the Laverda. . I wonder how well some wooden dies would work.

[husaberg]

Most of JJ alloy frames were initially fabrications
he later i believe used extrusions, The poor buggar died at 55

Most euro works bikes at least with fabrications ie Aprilia and Cagiva and possibly ROC used what was referred to as "Carpental" which i believe is an aircraft alloy 7020.
7075 was called Ergal.

The cagiva mito used a similar looking extrusion and design to some of those you posted.

its like most an extrusion welded to two cast pieces.




their banana arm is all cast.

[el chupacabra]

I have no problems with casting, I have been thinking about that too. Although I am a little worried about casting imperfections causing failures. I’m definitely someone who overthinks these things.
I won’t be making enough to justify a run of custom extrusion, so I’ll be stuck with standard profiles, bending some of those fancy extrusions would also probably be a pain.

[Flettner]

If you cast it properly, there will be no imperfections.