I received a call last week from the turbo shop saying that the shaft broke when they were tightening the nut on the compressor wheel before balancing.
Normally, I'd be outraged and demand them to replace it at their cost. However, we all know that these shafts are underbuilt and snap all of the time.
I got in touch with Mr. Jack Heath that built his own 600 whp Frankenstein C30-94 for his Honda S2000. He gave me some recommendations and his own sketch for an improved sun-shaft. This is going to cost me about $450CAD for materials, machining and heat-treating. This really hurts the pocket book but if all goes well, this should be a very reliable Rotrex for about $800 all said and done.
Jack's version of the sun-shaft is made out of 440C stainless steel (Rockwell harness of 20) and will reach a hardness of about 60 after heat treatment. The shaft where the compressor is mounted on is 8mm wide compared to 7mm and a smoother radius was added to where it meets the oil seal area to improve strength. Therefore, my compressor will have to be bored to 8mm before balancing.
This is the shaft roughed out before hardening and final grind to size.
If anyone want's the sketch, I can ask Jack for permission to forward it to you.