RM 400T swingarm

[LWC82PE]

I am a believer in getting stuff like this T6 heat treated after welding. I will be getting it done to several of mine.

[Oldfart]

Yes it should be heat treated, as its the (pivot point ) taking all the movement at load.

[rocketfrog]

The trouble with heat treating Al alloys is there is a specific ramp up, soak and aging process for each different type of alloy. You need to know exactly what the composition of the Alloy is to effectively restore full hardness. You might assume 6000 series and you would be right, but is it 6060 6106 or 6061? all of these lend themselves niceley to extruded forms and are easily welded but the ultimate strength achieved by tempering is very different and the process used varies as stated. (I would like to think Al 6061 is used, but I dont know for a fact).

The only way to know for sure is to use a machine such as a Scanning Electron Microscope or SEM to analyse the alloy material and compare the percentages of the various alloys detected against known alloy composition.

Karl Landrus will only build a swing arm from known mill certified materials to ensure that the finished temper will be true to specification.

What does all this mean? You might as well have the welding and or machining done by a competent professional and omit the heat treating unless you can verify the actual alloy Suzuki used in 1980.

Post rework NDT (Non Destructive Testing) is a good idea to check for cracks and flaws associated with welding and machining.

On going safety by inspection is good practice to include in your regular maintenance regime.

[Tomas]

Let say the swing arm is most commonly used 6061 aluminium. Can anyone recomend a place that would be happy to do the heat treatment? It may be hard to find a place that is happy to do a small jobs like this. Also I am not sure about cost of such service.

[rocketfrog]

Tomas, contact GMC on this site. Geoff uses heat treaters for his frame work and would have a friendly company on his books for sure.

[LWC82PE]

Well i know my aftermarket ones are 6061. Not sure what suzuki used

Here is a bit mentioned on the japanese material

http://www.vitalmx.com/forums/Old-School-Moto,22/Vintage-Aluminum-Swingarm-Question,1122127

[rocketfrog]

Dont get me wrong, I am all for heat treating and understand the importance of optimum strength in components such as frames and swingers. I have read through that blog before and was a little disturbed to hear the engineers reply to the enquiry on heat treating, obviously this bloke did not understand the concept of post weld heat treating.

I really would like to know what the material spec is for 1980 RM swingarms is, I have done conductivity and hardness testing to get an idea of what material is used in an RM125T arm.

I spot faced the extrusion and the axle plate to remove a small area of anodising to get a true reading but the test is not conclusive. This test just narrows it down to a handful of likely materials, although 6061 T6 is probable being that the physical properties of 6061 tick the boxes for a structural component which is both extruded and welded and can be heat treated to achieve the best strength for the 6000 series alloys.

I doubt anyone would disagree that that 6061 would be the best choice for the application, but what were the Japs thinking in 1980? Build to last or build to a price?

[skypig]

Karl Landrus will only build a swing arm from known mill certified materials to ensure that the finished temper will be true to specification.

Who is Karl Landrus?
Is it likely he would build me a Supermoto swing arm?
How do I contact him?

[LWC82PE]

Well in my opinion the 79/80 RM's were not built to last more than a couple seasons. It appears they were trying to cut weight everywhere where they could but keep production and final cost for the consumer realistic. And this continued even more into the early 80's as well with alloy screws and drilled out axle spacers. The hex nuts they made as thin and small as possible, swingarm spacers drilled out, reduced rear axle down to 15mm on 250/400 when they were 17mm 77/78. 79 RM's had thin alloy axle nuts, they must of had some issues with these as they went back to steel in 80. I might have a junk  1980 PE swingarm i could possibly sacrifice for some material if someone wants to  find out what they are made from.

Who is Karl Landrus?
Is it likely he would build me a Supermoto swing arm?
How do I contact him?

http://www.klpracing.com

[mick25]

Karl Landrus will only build a swing arm from known mill certified materials to ensure that the finished temper will be true to specification.

Who is Karl Landrus?
Is it likely he would build me a Supermoto swing arm?
How do I contact him?

karl builds after market swingarms in the states trick stuff not cheap but you pay for what you get goggle him , he has his own site

[KTM47]

If you are considering buying an aftermarket swingarm, make sure it is an exact replica of a swing arm made back in the day.

Some of the swingarms available are not and can run into eligibility problems.

One easy way to check is what the chain adjusters are like.  If they are the more modern style with an alloy block chances are they are not a true replica.