Swingarm Brace - what grade to use

[Shox Dr]

Been asked to brace a swingarm on a Kawasaki ZX12 (B3). Had a look a a few builders and they are using 7020 grade Alloy, however when I look that up it isn't available in tube.

Would another 7xxx series tube be OK to use. It will more than likely be powder coated afterwards so colour match between the brace/rod/swingarm is not important, but would be nice, in case he has it Anodised/polished later on.

Worth noting this is for looks (aren't they all)

Tube size will be 1.125" wall thickness around 1/8"

 

[hotrodder]

For one job is it not worth trying one of the frame builders that use 7020 for a metre or two? There aren't really any other suitable 7xxx series alloys, 7075 is fairly common but not weldable (or used as tube) and 7005 is what 7020 goes by outside of Europe/in the States.
Not listing the size you're after but http://www.bfomotorcycles.co.uk/forsale.html is a possability.

Probably already found capalex, they might be able to point you in the right direction as someone somewhere is extruding 7020 tube. Could be that it's extruded for specific companies (i.e. they own the dies), was given that story by my local stockholder regarding certain diameters of 6063 tube that none of the usual suspects stock/can get. Could've sworn that some of the aerospace stockholders carried it but as you said, not tube

IIRC Pace cycles (relatively local) used to use 7020/7005 for their RC200 frames, might be worth contacting them to see if they can point you in the right direction. Don't think i made that up but they're using a 6xxx series these days

Framebuilders use 7020 as it 'recovers' from welding better than the 6xxx series so less weight/more strength without 'fully' heat treating. If you can't get your mits on some then only choices really are 6082 if you don't need to shape it much or 6063 if you do.

 

[Shox Dr]

First thing that came to mind was 7005, I know that doesn't require post treatment, but the Aero supplies site I looked at didn't say that, 7005 was the same as 7020.

My history is in the MTB industry (I was know as The Shox Dr). And had thought of calling the likes of Curtis Bikes that I used to deal with.

Thanks for the pointers.



PS Pace used to be just outside Kirbymoorside, and now see they have moved up the road to Wykeham, (Scarborough). Also close you me. But your location says you're in the South East. I'm confused???

 

[Shox Dr]

Probably already found capalex, they might be able to point you in the right direction as someone somewhere is extruding 7020 tube.

Rather confusingly they also state it's not good for welding??




I'll get Locate Supplies a call tomorrow they will sell off a full lenght, if they don't have an offcut on stock

 

[hotrodder]

Sorry, meant to local to you as you're in Yorkshire. The 7020/7005 thing... only time i've seen both alloys listed in the same location is in international designation cross reference charts. Same/equivilant alloy listed as 7005 for US specs and 7020 for UK/Europe. There may well be slight differences but it's effectively the same alloy

Edit: Even more confusing they list it's weldability as good here. It's a typo in the first link

Found an International designations chart

 

[scott0031]

Don't waste your time trying to source it. You wont! min order is normally 2 to 5 ton runs at a time pending on the section. Not available in the uk in the section needed for arms. The arm makers you have probably looked at have their own dies made in some cases, the rest is standard dies but its still only extruded to order.

Been there done it got the T shirt. The best bet is to try spondon or harris. They 'Might sell you a bit but is very unlikely they will. If they will they will most likely rip you over on the price, They know the score.


The problems don't end there im afraid. its 7020 is supplied in its highest T spec (It only has one T spec) and is not heat treatable. Which means the only way to bend it is with a great deal of difficulty and it will 'HAVE to be done with a mandrel due to this T spec. Even with a mandrel its still not pretty bending. In fact its pretty awefull as tube bending goes.


Kind regards,


Scott (ward eng)

 

[Shox Dr]

I don't think sourcing the tube will be too much of a problem. I have a few places/favours I can call.

What would you suggest is the best grade to use then bearing in mind;

It's just for looks
To be bent on a Rotary Draw Bender 1.125" Dia 4.5"CLR Die

 

[scott0031]

Well if you can find the material then hmmmmmmmmmmm keep your source close to your chest lol. The only people that will use 7020 are aerospace motorcycle arm (and sometimes chassis builders) and push bike makers but they only use thin wall sections. They are all in the same boat having to buy minimum order amounts and getting it shipped in, as mentioned 2 to 5 ton lots The chances of anyone having it in the section you need are very slim indeed. If you can get it then well done and don't tell anyone! lol


If you go grab a bit of ali something with T6 spec and go try to bend it. That's what your up against. The difference is 7020 is much more resistant. It can be done as it is done frequently by people like jmc. But they have spent years perfecting bending it and its very often not that pretty especially on tight rads. Hence the use of a mandrel.

I spent many years in motorcycle engineering and one of only the handful of arm builders out there past and present. So i have been down the route your trying to take shox.


Kind regards,


Scott (ward eng)