Axle steel composition

[Hopmeier]

I had one of the 15 inch axles from the I-cubed update analyzed for steel composition to machine some new ones I am designing. It looks like the steel used is 4820. CAUTION: I am not sure this was an original axle nor what its true pedigree is, but I think it is from the I-cubed and it was 15.13 inches in length.

I will be using 1045 for my new axle design. It is a little cheaper and easier to get at the moment as 4820 is no longer generally produced It is close to 4820, just a little harder and somewhat better fatigue life.

https://amsresources.com/4820-alloy-steel/

https://www.theworldmaterial.com/astm-sae-aisi-1045-carbon-steel-material/

[W427]

Following this. In the other axle threads, the early (original) axles were tapered in the center section, and the later replacements were full-diameter from unknown design source. The early axles appear to have been a hair too short. The failures we have seen appear in the the later axles, where the lack of torsion and reduction of material at the splines incurs failure at the splines as the weakest point.

The replacements I've seen pictured here are tapered, as are the racing axle replacements I obtained, presumably to both improve torsional modulus and place failure in the shaft section between splines, instead of at them. The axles I purchased (but not needed yet) have both these properties and are made of 4340, which they claim reduces transmission failures, again assuming greater "torsion spring" load absorption before yield.

Lots of assumptions of what and why, and it's not all logical. Just throwing stuff out there from the trail of crumbs we've seen so far, hoping it helps.

[Hopmeier]

Did the axles you purchased at least fit? Can you send the source and details, as I need a few, and am also having some made as well. There have been many references to various axles adn sources including various Ford replacements as well as going to Yunani et al to have some custom made.

[W427]

I haven't tried, and all based on info here and measuring a broken axle Paul M1163 sent me for dimensions. Info in other threads. I have had no failures, and don't need to service anything, but may get into it this winter if time allows. I'll just fit a couple in there, and if they fit I'll run them, just for minimal validation.