What is the difference with the 26/27 crank compared to the other previous years?
The big change in crank design came in 1924. The earlier lighter and less sturdy 1909-24 style crank has diamond shape throws while the 1924-27 style has straight throws.
One of the improvements with the straight throw style crank was larger radii by the rod journals - they used to be just 1/16", but was increased by then to 1/8". Ford's main journals always had 1/8" radii.
Sometime in 1925, maybe for 1926 production EE steel became available and part of the crank production was of EE steel from then on. It's considered to be better, but you have to check the markings to be sure it's an EE crank in a '26/'27 style engine. Here's an example:
Some EE steel cranks has the markings stamped in the front edge.
How do you know he is asking about the crankshaft instead of the crank (hand crank)? When I first saw his question, the first thing that popped into my head was the hand crank on the front of the T. Jim Patrick
Because Bob is a retired engineer, and we old engineers ponder such things?
The late ee crank is made from essentially the equivalent of 4340 chrome moly steel. No more vanadium steel. I had one tested by a qualified lab
And they still break too!!
And Scat cranks break too
I have always heard the view that Henry used Vanadium steel because he thought it was the best he could acquire, especially when concerning the frame and suspension..did he change his mind especially when it came to crankshafts?
No...his mind was changed for him. Vanadium was part 'bunk', part unknown science that happened to yield repeated predictability and consistency. When Ford had problems making Vanadium Steel after the installation of the new different technology furnaces at Rouge, coupled with all the others actually sharing thoughts on Alloy Steel making coupled with heat treating, Ford became abandoned on an island of its own making.
Think of it like Grandmas chocolate cake v. the same recipe made by the next generation. Somehow it comes out different...was it the effect of Grandma's oven that caused the great taste that is elusive now? Or, was it the exact number of times she beat the batter? Or, was it the moisture level of her kitchen? Or, maybe her chickens laid better eggs? No one knows and the 2nd generation of daughters and daughters in law take safety in number with neighbors to create their own individual versions rather than keep trying to duplicate Grandmas and continually failing.
Vanadium steel had its' day and usefulness (ironically, some small boutique electric furnace mills are producing a variant of Vanadium steel today for 'tough' applications). Vanadium steel also had its glass ceiling limitations and one of them was Wills and his abilities to take Vanadium to the next level...another was Wandersee and what he could contribute. I imagine they did NOT hire consultants to help with evolution. Wandersee himself has said that by 1927 Model year there actually was NO actual Vanadium steel in the Model T.
Regarding breakage, lets say I could acquire an EE crankshaft, with good standard size journals. If I went to the trouble of having it magnafluxed and/or x-rayed for cracks and it passed with flying colors, should I expect it to stay together provided I get the 4th main properly centered?
How much does it cost to have one checked?
Yes to your thoughts. Crack checking shouldn't cost much