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Home built half shafts


o_teunico

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Just no, to both methods.  Seriously, the suggestion of sleeving the splines, securing the sleeve with Locktite and recutting?  That's like supergluing matchsticks to the end of a plain shaft and hoping they'll stay on!  As for what he did with the screwed joint, that's the same strength shaft as cutting a groove through 1/4 diameter of the shaft!  What a botch!  He has no idea of what he's done.  They'll snap like toothpicks the first time they get a decent amount of torque through them.  He'd have been better off welding cut down shafts together, even though he recognised the issue of heat treatment.

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 Bizarre.  I think he's right about the torque going through the outer edge of the shafts, (many years ago on here was a discussion about drilling out the centre of half shafts for this reason plus reducing the stress)

 

If the joint faces are perfectly square and done up really  tight, the friction between them ensures that the force transfered to the outer region.

 

Even so, it does not seem right, especially with the grub screws, they should have been staggered as opposed to being I the e same plane. 

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20 minutes ago, 02GF74 said:

 Bizarre.  I think he's right about the torque going through the outer edge of the shafts, (many years ago on here was a discussion about drilling out the centre of half shafts for this reason plus reducing the stress)

If the joint faces are perfectly square and done up really  tight, the friction between them ensures that the force transfered to the outer region.

That is not how the stress in torsion works.  This is the problem with a little knowledge is a dangerous thing.

Torsion produces a shear stress that increases linearly from the center to the outer edge.  At the end of his threaded shaft, the outside diameter ends, so cannot develop any shear stress and pass it on to the next shaft.  The minor diameter of the threaded section set the maximum torsional stress that the shaft can take.  He used 7/8" UNF.  This is about 30% the strength of 24 spline and half as strong as 10 spline.  Not taking into account the low fatigue life due to all of the stress raisers.

Edited by Red90
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2 hours ago, ejparrott said:

Started watching it but got bored....does he actually do anything or show any bits or just he just sit there droning rubbish in to the camera?

I got bored too, and skipped through. There's a section about 3/4 of the way through where this finished product is briefly shown.

It's a lesson in how not to make YouTube vids tbh. As the the work... Hmmm

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Haven't whatced the vid and won't bother having read the 'reviews' :D Can however share some experience in welding shafts together, as I've tried that quite a lot in various situations. And to give you the short version: If you get the weld just right, not too much heat, but still decent penetration and slooow cooling it is comparable to a 10 spline in strength, just.

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This guy seems to think the welds will cause cracks in the surrounding material.  Welding them has its issues, but I suspect more to do with softening the shafts through annealing rather than making them brittle.  However, I'd rather see the whole shaft subsequently baked and annealed for consistent heat treatment, rather than having localised heat from the welding and variations in hardness unaddressed.

His grub screws to lock the shaft halves don't seem a bright idea - I can imagine them acting like cams, turning torque into thrust forces that will put the threaded joint into tension as well as overloaded shear.

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https://youtu.be/KhGx9zGt8ic

Round 2

 

fancy HD shafts break with lockers so why does he think 2 violated Cadbury axles would be a good idea. I admit I couldn’t watch that all the way through.....I fast forwarded a fair bit but form what I got he’s only got 1 RH tap so one side of the axle will always be trying undo....all load on the grub screws. That is why bike cranks are RH and LH thread.....

 

 

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1 hour ago, dangerous doug said:

https://youtu.be/KhGx9zGt8ic

Round 2

 

fancy HD shafts break with lockers so why does he think 2 violated Cadbury axles would be a good idea. I admit I couldn’t watch that all the way through.....I fast forwarded a fair bit but form what I got he’s only got 1 RH tap so one side of the axle will always be trying undo....all load on the grub screws. That is why bike cranks are RH and LH thread.....

 

 

Okay, I watched this one.. This is entertainingly stupid! :rofl::hysterical: The fact that this guy can't see that by hollowing out the halfshaft THIS MUCH makes it no stronger than a slice of bread really is beyond me! How can people, who still has the abilities he has for machining, material knowledge etc not realize this?? What is up with the world? :hysterical::hysterical:

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