brake discs

Tony Foale is still around : https://motochassis.com/

I read various articles he wrote back in the '80s. Would be interesting to see a picture of the bike.

Try AP Racing they used to stock brake disc blanks that could be purchased. 

Manufacturers of circular sawblades for sawmills do heat treating. Don't know if there is any in the UK.

There are loads of companies that heat treat in the UK, but you'll need to have the material spec and what type of heat treatment you need. Be very careful, a through hardened disc would not be something I would use or even attempt to make. 

I'm a big fan of Tony Foale's designs. Have you looked at cast iron alternatives from the automotive industry. Something of adequate overall dimensions (even a used item) could be machine to your requirements without the need for heat treatment.

Brake discs are usually grade 17 cast iron (AP racing told me this years ago) That said i would be very doubtful of using a cast iron disc 1/8" thick

Get a disc water jetted cut from 1/8" stainless. So long as the cutting company  takes care it should be flat enough. Water jetting will not put any heat into it so no warping. 304 stainless should be ok. Cutting it from sheet will also keep the faces parallel (most important)   No heat treatment  

Cast iron in the thickness required will not work, I doubt if they could even be manufactured successfully, then there is the issue that there are very few pads that will work with cast iron. A modern material will work with modern pads.

A common stainless grade for bike discs used by many manufacturers including current EBC motorcycle products is 420 series Martensitic.  The floating 4mm Nissin discs on my Commando and aftermarket Yamaha 4mm discs use this material.

Needs to be heat treated and precision ground but works perfectly with Ferodo Platinum FDB88P in Commando Lockheed callipers or modern EBC HH pads in others. Excellent performance and disc wear of 40k+ miles easily achievable.

Pretty certain some 300 series stainless won't be hard enough and not heat treatable to the required specs for discs

Thought i post some photos of the brake discs i have just refaced over the last few days. This all came about as i had a T160 disc to grind up for a client, and while the machine was set up to do disc grinding i thought i would go through the pile of worn and scabby looking discs that have accumulated.   

Disc thickness is the same all the way round. Both sides of the disc are ground at the same setting without removing the disc from the machine, so ensuring the disc is true.

When you get the disc water jetted, Measure the thickness all the way round the disc and if it is parallel all the way round you should be good to go. Think the rolled s/steel sheet is like a thick shim, you don't get shim steel varying in thickness do you?  It may or may not need stress relieving. I would try it out first on the bike. When you think about it, the disc get heat treated every time it is used in anger!     

Yes the disc will need heat treatment and precision grinding after cutting but you'll need to talk to the people who do it for the correct sequence and procedure. Could ask the EBC motorcycle tech guys about this. Brembo unlikely to tell you anything.

If it's only for display rather than hard road use, a basic cut and ground 420 disc may be adequate.

Heating treating the brakes by riding no good at all, nowhere near hot enough. 420 stainless usually heated to 1000°c+ and needs controlled quenching. Even race car metal discs have optimum working temps around 400°~ 600°c from memory. Can't imagine any Commando achieving this on a skinny WM2 and Roadrider.

A large diameter disc 3.2mm thick needs to be made properly, shows the innovation of Tony Foale in that era. 

Sounds like you've got it well sorted Jan, flying the Tony Foale flag in 2024. He'd love the fact you're actually riding it to France. Pics when it's done please, the Commando engine makes it even more rare. JPS black gold color scheme or red white and blue?

Normandy in early June is around the 80th D Day commemorations, will be busy. Returning from a memorable Spain Portugal ride in 2011, we washed up at the excellent Bayeux campsite on June 5th. Looked like the US/Allied army was there, restored wheeled military vehicles of all sorts from Jeeps to big GMC type ambulances.

Funny thing was, alot of the owner restorers were from Holland so 1944 US soldiers with Dutch accents. (Dutch blokesssh) Very interesting stay and they told us it's quite a big thing back home with certain number plates reserved for vintage types. There's also a superb, authentic French/US restaurant across the road from the campsite.