- Thread starter EddyP
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PhillipM
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Not sure if even that is going to be enough, even with it being about the only sensible step to try now - I would agree with JSF though, waist the neck slightly more maybe to move the stress further away from the spline again but it seems it's not helped enough the first time.
I'd be tempted to try to change the design somehow to take shock out down the line somewhere, different diff mounts, some sort of cush-drive (sprung clutch, torsion bar propshaft design, or similar) otherwise you're getting to the point where you may as well step up to a maraging steel and then cry at the price of a)getting small quantities and b) finding someone that wants to deal with machining and heat treating the stuff - the last time I did some I had to have it done on a batch at an aircraft factory as a favour!
I'd be tempted to try to change the design somehow to take shock out down the line somewhere, different diff mounts, some sort of cush-drive (sprung clutch, torsion bar propshaft design, or similar) otherwise you're getting to the point where you may as well step up to a maraging steel and then cry at the price of a)getting small quantities and b) finding someone that wants to deal with machining and heat treating the stuff - the last time I did some I had to have it done on a batch at an aircraft factory as a favour!
EddyP
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Been and spoken with some folks today about it.
300m/S155 is an option but
Is going to be about £1k for the pair!
The other option is I can change the diff for an 18spline diff, which is also a larger diameter, then potentially do them from EN24T, the increase in diameter should substantially increase the strength.
From this pic the current ones are the bottom pic, the 18 spline is the middle one.
300m/S155 is an option but
Is going to be about £1k for the pair!
The other option is I can change the diff for an 18spline diff, which is also a larger diameter, then potentially do them from EN24T, the increase in diameter should substantially increase the strength.
From this pic the current ones are the bottom pic, the 18 spline is the middle one.
Brad93
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This might not be a strength issue, if it's flexing repeatedly any through hardened steel is going to keep fracturing because of localised work hardening/ fatigue.
This is why 4340 isn't always suitable for shafts or pins, and they turn to very tough but soft cored steels that have been case hardened.
This is why 4340 isn't always suitable for shafts or pins, and they turn to very tough but soft cored steels that have been case hardened.
EddyP
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I doubt it's flexing, it's all mounted pretty rigidly, you can see the bearing on the shaft and the other end is located in the diff, the method of putting the diff together is done so that no misalignment has occured to try and ensure there's no change of any flexing. Would need the ally casing to be flexing too, it's possible but I think unlikely. Also if it was fatigue it wouldn't have twisted the spline would it? Wouldn't it have just cracked and broken.
I think your problem is driver technique.
Dropping clutch is loading the drivetrain, the items with the highest inertia will be the wheels and tyres.
Either slow down the clutch take up or lighten the wheels and tyres.
The first 60 foot off the line probably only needs to be a tenth slower to stop the shafts breaking.
It might be half a car length but you have to weigh it against the non finish and repair costs.
Dropping clutch is loading the drivetrain, the items with the highest inertia will be the wheels and tyres.
Either slow down the clutch take up or lighten the wheels and tyres.
The first 60 foot off the line probably only needs to be a tenth slower to stop the shafts breaking.
It might be half a car length but you have to weigh it against the non finish and repair costs.
Pigeon_Droppings2
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I wonder how modern EVs cope with all the power and almost instant torque...must be well engineered to deal with the power I would think.
Morris
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I'm no expert but I have played with high horsepower stuff and the transmission parts that go with it. The very tough half shafts are surface hardened, the core is left in a softer state.
I have machined Jaguar shafts and they are very tough to a depth of about10mm.
Is it possible that your parts are through hard? You can usually see the transition on the broken face.
Strange Engineering half shafts are forged but the material spec seems to be elusive.
I have machined Jaguar shafts and they are very tough to a depth of about10mm.
Is it possible that your parts are through hard? You can usually see the transition on the broken face.
Strange Engineering half shafts are forged but the material spec seems to be elusive.
Brad93
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Exactly what i was trying to point out above.
Pigeon_Droppings2
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Makes sense...the splines need to be very tough but the shaft itself needs to be "elastic" I would think to reduce the shear forces.
EddyP
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That’s one of the reasons we made these ones from EN36C, it’s a tough material that’s just case hardnened.
I’ve dropped one off to them all to a bloke today who certainly talks the talk, makes all of the hubs on the NASCARs and all sorts of other gears, shafts etc he said he’d test the hardness and heat treatment on the shaft I’ve dropped off. He also said it was the right material but maybe they got the heat treatment wrong, next step up material is 300m/S155. Best option though is increasing the diameter as above.
I’ve dropped one off to them all to a bloke today who certainly talks the talk, makes all of the hubs on the NASCARs and all sorts of other gears, shafts etc he said he’d test the hardness and heat treatment on the shaft I’ve dropped off. He also said it was the right material but maybe they got the heat treatment wrong, next step up material is 300m/S155. Best option though is increasing the diameter as above.
