Hi Brian Yes I agree, but I do not hear of them breaking. If I had to select a readily available steel that does not need subsequent heat treatment, I would choose EN24T in preference to EN16T, Both are quite strong, but the nickel in EN24T gives it more ductility. EN 16T tends to be a little more granular and brittle but, of course, not as bad as “Silver Steel” which is more brittle and should be avoided at all costs
The material I use for cranks is quite special, expensive and needs unique heat treatment in controlled atmosphere furnaces in several stages. I have to hire a furnace at about £1500 and I can put in the box whatever I can get in for the one process. I remember a Vincent sprinter asking me if I could make some head / barrel bolts to highest strength possible. The material and machining were not cheap, but were reasonable considering what was asked, but when I added on the heat treatment at £1200 the customer thought I had gone mad. I had to explain that it was not possible to consolidate with other customers and I had to hire a box whether there was a lot or a little in it. That is why I always ask about steering stems and if anybody has any special requirements before we start as afterwards, like the Vincent barrel studs, it will be too expensive. When I first investigated the material for the cranks, I knew that I had to go for the absolute optimum material to make cranks that were so far superior to the originals as to put the possibility of breakage beyond reality. Richards bike on dope is putting out 42 bhp on a standard overhung crank and certainly nobody has broken one made in this material. Several years after I started using this steel, I heard that Air Bus had chosen to use the same steel for their landing gear, so the punch line is, when you hear that the wheels have been falling off the AirBus aircraft, then you can start worrying! I have been very lucky to have had such a wide variety of engineering challenges in my life and this is very helpful to me. I have no idea where anyone can get such a comprehensive engineering education nowadays, but then starting to work machinery at nine years of age at weekends was unusual even then. OK back to work. Kindest Regards Roger
