70 years of abuse and somewhere along the way my rear brake pedal has developed a rather un-original contour
What is the best way to bend it straight? Heat or cold, if heat do I need to get it cherry red? Quench after, or leave to cool at any particular rate?
I don't want to leave it brittle or soft afterward.

"Malleable Iron" No basis in science here; if the arm did not break from the original "unintended" bending, my experience on wanking away on bent brake pedals is that a small distortion can be corrected cold....if the rebending effort can be distributed over the length of the arm.

A more severe reshaping should be done hot....cherry red, no quench

It is iron after all; malleable or not, with a course granular structure, and will break or be severely weakened if the bending is too localized or too extreme...hot or cold.

email (option): teladelujo@ msn.com

John, I think there is an unintentional typo in your last post. It made me laugh out loud.

Or perhaps not unintentional....just highly descriptive in a colloquial sort of way!


Cheers,

JDE

email (option): teladelujo@ msn.com

Hi John, when you speak of a course granular structure, do you mean that these parts are cast?

I had the impression that the parts like the brake pedal along with the footrests, gear and kickstart lever, and probably the fork links were forged, as they are very though and I have never seen an broken original one.....

Regards, Michiel / NL

email (option): m.wijbenga [ at ] hotmail.com

I imagine that a lot of these parts are cast in steel which is bendable as opposed to cast iron which will just break. Hence the worry about the Indian made forks Ron

email (option): ronpier@talk21.com

I remember seeing pictures of huge presses at the BSA factory which makes the forged steel backbone used in different forms on various models in the early 30's. They were made from a piece of hot steel and stamped in four steps.

If they bothered to make forging tools for these big parts they might as well have made it for these smaller and vulnerable/exposed parts like the footrests and levers. Also my experience with straightening these parts and not seeing any broken ones make me think that it cannot be castings...

It would also explain why the Indian kickstart levers are sometimes breaking as (besides maybe using inferior quality steel) they are castings instead of forgings which of course asks for much more investments in tooling.

But I am not sure and it a just a feeling so please correct me if I am wrong.

Regards, Michiel / NL

email (option): m.wijbenga [ at ] hotmail.com

Yes, forged .. BSA were famous for there habit of forging parts weren't they.
A clue to a forging is the area of "overspill", the seam that needs grinding off during production is much wider than on castings.

I claim no expertise other than my own limited experience with various machines over the years.

"Casting and Forging" As I recall, the brake pedal on the M as well as various other machines are referred to as being made from "malleable iron" which are formed from a fine grain cast iron that is slowly heat-treated and then forged to final shape.

Footrests are often made of the same material as are other bits such as frame lugs; complex shapes that would be costly to machine up but can be easily cast up close to their finished shape.

NOTE: The front fork assemblies from India may well be made up of cast lugs and fittings, but it is not at all likely that they are using forged malleable iron, but the garden variety of course grey cast iron, which is as noted, brittle and unsuited for such an application.

If you bend a WM's foot rest or brake pedel severely, it will eventually break cleanly and you will notice the material structure is not similar to what commonly referred to as steel, but much more granular. And once broken it is not easily repaired by normal welding process, but requires brazing.

There is plenty of information on this topic from various engineering sites on the web; this is just a quick sample:

"Malleable iron is cast as White iron, the structure being a metastable carbide in a pearlitic matrix. Through an annealing heat treatment, the brittle structure as first cast, is transformed into the malleable form.

Carbon agglomerates into small roughly spherical aggregates of graphite leaving a matrix of ferrite or pearlite according to the exact heat treat used. Three basic types of malleable iron are recognized within the casting industry: Blackheart malleable iron, Whiteheart malleable iron and Pearlitic malleable iron.

After the casting and heat treatment processes, malleable iron can be shaped through cold working, such as stamping for straightening, bending or coining operations. This is possible due to malleable iron's desirable property of being less strain rate sensitive than other materials.

Like other similar irons with the carbon formed into spherical or nodular shapes, malleable iron exhibits good ductility.

It is often used for small castings requiring good tensile strength and the ability to flex without breaking (ductility). Electrical fittings, hand tools, pipe fittings, washers, brackets, fence fittings, power line hardware, farm equipment, mining hardware, and machine parts."

email (option): teladelujo@ msn.com

.. my previous post should say ....famous for "their" not "there" haha

I've straightened loads cold but now days i always heat to cherry red to direct the straightening to the exact spot & get it right... as almost none of the ones i straightened cold years ago returned to exact correct shape which is even harder to rectify.

As you describe, applying heat is surely the best way.

If part is just slightly bent and there is a nice run of length to work with, I will bend cold as am too lazy to remove heat, then clean and repaint....

email (option): teladelujo@ msn.com

Not sure if they are made by the same process, but I've just cold-straightened my footrests, which were in a sorry state with one bent up and the other bent back - no problems. I put one end in a vice and used six foot tube for leverage.
Scorp.

email (option): wm20@scorpionvideo.net

Thanks John, that sounds convincing. It would mean that they had to make also casting tools beside the forging tools. But the parts will last almost forever...

Regards, Michiel / NL

email (option): m.wijbenga [ at ] hotmail.com

i should add that another reason i heat badly bent ones is because these are old bikes, The part may have been bent & straightened cold many many times already ... but yes I'm talking about very bent rather than just a slight adjustment which i happily do cold.