, should I replace the half shafts? If so, any recommendations?ta
stephen
Strengthened half shafts
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sgrant
- Posts: 333
- Joined: Thu Jan 29, 2009 10:44 am
Strengthened half shafts
Now i'm the proud owner of 110bhp , should I replace the half shafts? If so, any recommendations?
ta
stephen
, should I replace the half shafts? If so, any recommendations?ta
stephen
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erictharg
- Posts: 680
- Joined: Thu Jan 29, 2009 7:50 pm
Re: Strengthened half shafts
Depends how hard your existing ones have been worked, and how often you indulge in "hard" starts. Given your natural instinct for "bulletproof", I'd say they should be somewhere on your shopping list. There's no way of knowing when or where they could go due to fatigue. On my list for upgrade in winter, £'s permitting if only to eliminate a known weakness.
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Mknight702
- Posts: 214
- Joined: Thu Jan 29, 2009 7:49 pm
Re: Strengthened half shafts
I haven't had any problem with my alternative solution, the trackday at the end of August will be a sterner test though.
My solution was to machine down the half shaft in a lathe, the reasoning behind this was the half shafts snap at the splined end (normally in the diff) because this is the weakest point. By machining down the half shaft it allows the torque load to be spread along the whole length. It works in my head but i haven't done any scientific calculations to back it up, perhaps Charles knows someone who can do some scribbling on the back of a fag packet.
My solution was to machine down the half shaft in a lathe, the reasoning behind this was the half shafts snap at the splined end (normally in the diff) because this is the weakest point. By machining down the half shaft it allows the torque load to be spread along the whole length. It works in my head but i haven't done any scientific calculations to back it up, perhaps Charles knows someone who can do some scribbling on the back of a fag packet.
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erictharg
- Posts: 680
- Joined: Thu Jan 29, 2009 7:50 pm
Re: Strengthened half shafts
Most halfshafts fail due to fatigue cracking, not simple "snap like a carrot" overwhelming of the steel. Usual point of failure is the root of the splines because you have a sharp edge. Was a big problem when racing Land Rovers off road. People spent a fortune making exotic new shafts when all you needed was a set of factory fresh standard items. You' punish them all season and then they'd break setting off gently from the lights one day, because the fatigue crack had just happened to work through enough of the shaft to get to that point.
As you can't get new Midget half shafts (at least I don't think you can) you always run the risk. It's a function of how many miles yours have done, and how hard they've been used.
So, if of a nervous disposition, or OCD about reliability, you would want at some point to invest in some stronger items, if only because they are new and so at the start of that fatigue failure curve. Of couse, if designed right, they should be ultimately stronger so their fatigue life is also better, assuming no nasty stress raisers in their machining.
They are on my shopping list for the winter. Once I've been to see Peter May and check the materials and design.
As you can't get new Midget half shafts (at least I don't think you can) you always run the risk. It's a function of how many miles yours have done, and how hard they've been used.
So, if of a nervous disposition, or OCD about reliability, you would want at some point to invest in some stronger items, if only because they are new and so at the start of that fatigue failure curve. Of couse, if designed right, they should be ultimately stronger so their fatigue life is also better, assuming no nasty stress raisers in their machining.
They are on my shopping list for the winter. Once I've been to see Peter May and check the materials and design.
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Westfield 129
- Posts: 882
- Joined: Sat Jun 04, 2011 4:20 am
Re: Strengthened half shafts
I have about 120 HP, and a TranX LSD. I have failed a few axles, just driving the car normally in the canyons. The axles always break when driving away from a stop light, in town.
The failures have occurred with regularity since the installation of the LSD. This is due to the elimination of wheel spin off of slow corners, or any corners. The XI has a high roll center in the rear, and it is always lifting that inside wheel on corner exit. This allows the extra HP to pass through the axle as harmless wheel spin, but pretty much eliminates the fun of driving the car in the canyons as even light throttle applications and a front anti sway bar don't really help. With the LSD, power goes to grip, and acceleration off of the corner. It also makes it easy to maintain a drift angle. But the axles suffer. That I am currently running a 185/70/13 (the only size available at the time I needed tires), which turned out to be surprisingly grippy isn't helping the longevity of the standard BMC axles.
My axles have failed at the splines, in a conical shaped failure, which indicates that the axle was twisted in half. This is not a problem of fatigue or a small crack propagating through the axle. The axles have also failed at the drive plate, twisting it off as well. Drive plate failures are due to the weak hub bearings and lack of support for the axle by the hub, which results in flexing of the drive plate. The last failures occurred within two weeks of each other on opposite sides of the car. After growing weary of picking up the XI and shaking it to get the axle stub to fall from the differential so that I could plug in another axle, I finally purchased a set of two piece axles, with a bolt on drive plate. I have not had any more problems.
I am going to add double bearing hubs to better stabilize the drive plate as well.
If you have 100 HP, and you occasionally exercise those same horses, you will break an axle eventually. It will happen when you least expect it, and you might even remove the engine to change the clutch before realizing that the clutch is indeed perfect, and what you really had was a snapped axle.
Peter May has reasonably priced axles. I have ordered a wire wheel set for the new XI I am currently assembling, with the wire wheel axle housing. The Peter May axles come with the drive extension, which makes them a really good deal for anyone trying to run wire wheels.
The failures have occurred with regularity since the installation of the LSD. This is due to the elimination of wheel spin off of slow corners, or any corners. The XI has a high roll center in the rear, and it is always lifting that inside wheel on corner exit. This allows the extra HP to pass through the axle as harmless wheel spin, but pretty much eliminates the fun of driving the car in the canyons as even light throttle applications and a front anti sway bar don't really help. With the LSD, power goes to grip, and acceleration off of the corner. It also makes it easy to maintain a drift angle. But the axles suffer. That I am currently running a 185/70/13 (the only size available at the time I needed tires), which turned out to be surprisingly grippy isn't helping the longevity of the standard BMC axles.
My axles have failed at the splines, in a conical shaped failure, which indicates that the axle was twisted in half. This is not a problem of fatigue or a small crack propagating through the axle. The axles have also failed at the drive plate, twisting it off as well. Drive plate failures are due to the weak hub bearings and lack of support for the axle by the hub, which results in flexing of the drive plate. The last failures occurred within two weeks of each other on opposite sides of the car. After growing weary of picking up the XI and shaking it to get the axle stub to fall from the differential so that I could plug in another axle, I finally purchased a set of two piece axles, with a bolt on drive plate. I have not had any more problems.
I am going to add double bearing hubs to better stabilize the drive plate as well.
If you have 100 HP, and you occasionally exercise those same horses, you will break an axle eventually. It will happen when you least expect it, and you might even remove the engine to change the clutch before realizing that the clutch is indeed perfect, and what you really had was a snapped axle.
Peter May has reasonably priced axles. I have ordered a wire wheel set for the new XI I am currently assembling, with the wire wheel axle housing. The Peter May axles come with the drive extension, which makes them a really good deal for anyone trying to run wire wheels.