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wozza

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wozza last won the day on December 18 2018

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About wozza

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  • Birthday 08/25/1970

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  1. wozza

    Broken 4340 Stub Axle threads

    Joe's Manufacturer is replacing them at the next production run, that is in 8-10 weeks from now.
  2. wozza

    Broken 4340 Stub Axle threads

    Update from me, Joe from Chequered Flag Racing has been in contact with the Manufacturer and they have agreed to replace my stub axles too when they make a new batch. Thanks Joe.
  3. wozza

    Broken 4340 Stub Axle threads

    I Also agree, end float is what you need to check and that is determined by spacer length. A quick Google of torque specs for m20 bolts 4.8 grade is 166 lbft, a 8.8 grade 321 lbft. I hardness tested a standard stub axle too, comes out at 15 to 20 HRC on the shaft and 9 HRC on the flange. 20HRC is around a grade 8.8 bolt
  4. wozza

    Broken 4340 Stub Axle threads

    The grain looks a little different to mine, mine looks more crystalline. But that could be in the photo. I would be interested to see a hardness test on your one.
  5. wozza

    Broken 4340 Stub Axle threads

    It appears I have his yahoo address that he was using in April so thank you LLave for his new address. I will email him shortly Regarding torque, Haynes manual is 180 and up to 240ftlb if required to meet rotation torque requirements. 180 is about the most I can achieve with 1/2inch drive socket and I have never had a problem before. I lube all my threads,I use a lanolen product unless its an engine/gearbox etc. Good for your hands too! Regarding peening with a sedgehammer, I didnt need the sledgehammer this time, its got a stiff nut, I think its from a 280zx? nowhere to peen it. Curvature of the shaft does change the hardness reading but at this diameter its only .5 HRC
  6. Has anyone had a 4340 stub axle break off at the theads? I have attempted to contact Joe from Chequered Flag Racing / Modern Motorsport as this is the stub axle he sells, but I have not heard back, I know he is on this forum so I hope to responds. The stub axle was purchased this year and has only done 30 miles The failure point is not under load with engine torque or torque forces caused by sticky tires. The only failures I have had with standard stub axles is the wheel flanges failing. The nut was not over torqued and CV axle is not too short and pulled the threads off, there is more than 1.5 inches of plunge extension left and my suspension has very little droop My analysis of the failure. 1. Design. The threads are machined all the way to the step causing a large stress riser at the failure point, I have included a picture of the Modern Motorsport theads next to standard theads, You will see on the standard stub axle the threads stop well short of the step and have a nice radius 2. Hardness. I had the 4340 stub axle hardness tested, result was more than 51 HRC (Hardness Rockwell C scale) Carroll Smith's book 'Engineer to Win' states 42-44 HRC range for E4340 hubs, axles and torsion bars, Aircraft landing gear are also made from 4340 and need to be in this range too. Did I get an incorrectly machined and heat treated stub axle set? If there are any Metallurgists out there I would like their opinion too and looking forward to hearing from Joe.
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