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Discussion Starter #1 (Edited)
Well after the last thread seeing all the splines streched i got to wondering paying more attention on how manufacturing makes a diffrence.

This is a pic of a 35 spline recut and splined shaft......


What i wonder is how much strenght is lost when you cut the splines in the shaft...I understand the need to kneck down now but my other side stock shaft has no twisting of the splines.... So it has to weeken it more than a stock factory cut shaft..(also understand diffrent there are 2 ways to spline).

So i ask now how much weeker is a after market cromoly shaft that is cold cut/splined than the other splining technique? And how much weeker is a nonnecked down shaft compared to a knecked down one?

(It was pionted out in the other thread that most all aftermarket shafts are not necked down)

BTW this is a dana 60 stock inner cut down..
 

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Who is cold splining shafts ? Most I've seen are annealed and then rolled or cut and then heat treated and the strength depends on the effectiveness/type of the heat treatment.

Dutchmen shortend a stock 35 spline for me many years ago and it outlasted a number of 1480 joint, 30 spl outer and D60 Ring gears without the splines twisting.

I understand the theory of the neck-downed shaft - from a marketing standpoint its still a tough sell - I want the BEEF !
 

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Magnum_Willys said:
from a marketing standpoint its still a tough sell - I want the BEEF !
Why would you want it if it doesn't do anything, like paying for extra material?
 

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Weasel said:
Why would you want it if it doesn't do anything, like paying for extra material?
Lay a necked down shaft next to a necked up shaft and how many people would truly pick the necked down shaft ? I guess if I saw some hard data from more than one source about how much stronger the necked down is I could enjoy a small shaft :D
 

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The twisting on the splines of that shaft don't look to be an issue of the way the splines were cut but rather the hardness of the shaft itself. Was it heat treated properly after the new splines were cut?

As for the necked down (from splined portion to unsplined) vs straight....the ultimate strengths will be the same so you can't compare on a strength only basis. I believe the real benefit is the total rotational deflection at the breaking point. The necked down shaft will twist more before it reaches the breaking point so it will have absorbed more energy than a straight shaft. This plays a larger role on impact loads and not much at all on the break caused by pure torque when a tire is in an undercut or some similar situation.
 

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Discussion Starter #6
ok so new question? The blanks i bought and had splined (cromoly) should they B heat treated after being splined?

And i don't belive the old shaft was heat treated at all.......
 

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Now why'd you have to go hunting down problems like that man? We were supposed to go wheeling next weekend :laughing:
 

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Discussion Starter #8
Now why'd you have to go hunting down problems like that man? We were supposed to go wheeling next weekend
__________________

:( :evil: Hey i saw you won a driveshaft congrats..
 

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XJBender said:
As for the necked down (from splined portion to unsplined) vs straight....the ultimate strengths will be the same so you can't compare on a strength only basis. I believe the real benefit is the total rotational deflection at the breaking point. The necked down shaft will twist more before it reaches the breaking point so it will have absorbed more energy than a straight shaft. This plays a larger role on impact loads and not much at all on the break caused by pure torque when a tire is in an undercut or some similar situation.

Yes, and remember that when a failure is at the splines (on a non-necked down shaft) you can play for hours removing the stub from the carrier. Part of the advantage of a necked down shaft is promoting where the failure will occur (the other advantage is predicting under what load it will fail).

Happy Trails!
 

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Magnum_Willys said:
Who is cold splining shafts ? Most I've seen are annealed and then rolled or cut and then heat treated and the strength depends on the effectiveness/type of the heat treatment.

Dutchmen shortend a stock 35 spline for me many years ago and it outlasted a number of 1480 joint, 30 spl outer and D60 Ring gears without the splines twisting.

I understand the theory of the neck-downed shaft - from a marketing standpoint its still a tough sell - I want the BEEF !
Everyone cold splines shafts after they are heat treated, unless the shaft was splined by the manufacturer before it was heat treated like Superior does. Currie, Dutchman and Moser just cut off heat treated and machined blanks, cut the splines and machine the flange and bolt pattern. Most stock type shafts are induction hardened so re-heat treating is very difficult, the aftermarket 4340 can be annealed and re-heat treated but no one does that, the bearing dimensions would change during that process and the shafts also bend.

My preference would be a necked down shaft, but it would have to be made that way from the start. You cant do that with the heat treated, cut and splined blanks that you get from most places, for one it is very difficult to machine material that hard and if you took off enough material to get down to the root of the splines, you would have cut off most of the heat treated material and the axle would be worthless.

This is one of my 35 spline rear floater shafts, it is the right way to make an axle of of 4340 or 300M.
 

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I'm getting an idea from this thread: I'm going to scribe a line in the splined end of all my axleshafts that is parallel to the bores in the yoke end. Then it could be measured how much twist has been worked into a shaft the whole length of it.
Like others have mentioned, I don't see the splines being cut or rolled an issue in this shaft, it is a heat treat issue.
 

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Put a paint stripe on it -- better than inducing surface imperfections which could induce stress risers. FWIW, drag racers have been striping their axles for decades for that exact reason. They run shorter shafts and hook harder than we do! :cool2:

I'm pretty sure Goat runs Cone axles -- there's not that many other folks who profile shafts according to the books. Most folks just work from a blank...

Goat -- I'm curious why you specified materials for this profile... doesn't it apply to most any steel?

Randii
 

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78bronco460 said:
I'm getting an idea from this thread: I'm going to scribe a line in the splined end of all my axleshafts that is parallel to the bores in the yoke end. Then it could be measured how much twist has been worked into a shaft the whole length of it.
Like others have mentioned, I don't see the splines being cut or rolled an issue in this shaft, it is a heat treat issue.
It's not a heat treat issue, it's a design issue. For a shaft in torsion like an axle shaft, the peak stress is always at the surface, almost all cracks which lead to failures will start at the surftace. That is why you want a smooth surface finish and no sharp edges or transition changes that will be a stress riser, that is where cracks start. With a non-necked down axle shaft the short length of splines that are cut into the axle sticking out of the side gear take just as much torsional load as the rest of the shaft, but now the outer surface which take the most stress has been reduced buy less than half and stress risers added from the splines. That is why those types of axles fail there, it is the weakest part of the axle.

I made those axles myselft when I worked at SAW. The were made from 4340 tubing with a 11/16" ID. We made a lot of the off road race car axles and torsion bars, mostly of 4340 or 300M and they were all necked down.
 

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that axle is beautiful goat - i didn't know that cal poly also gives their engineers that much hands on training in machine shop practice:cool2:. can i assume by that picure you posted that the axle is reduced to approx. the root diameter of the splines it's entire length with the exception of the journal for the oil seal?. and if so this allows the entire shaft to twist under torsional loads and spring back to it's original shape as long as you don't excede the alloy's elastic limit. the improperly designed shafts place all the torsion loads at the splines instead of the entire shaft which because of it's length will accept more degree's of twist before failure?. trying to understand this as a tradesman without a formal education.
 

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stainless steal dave said:
that axle is beautiful goat - i didn't know that cal poly also gives their engineers that much hands on training in machine shop practice:cool2:. can i assume by that picure you posted that the axle is reduced to approx. the root diameter of the splines it's entire length with the exception of the journal for the oil seal?. and if so this allows the entire shaft to twist under torsional loads and spring back to it's original shape as long as you don't excede the alloy's elastic limit. the improperly designed shafts place all the torsion loads at the splines instead of the entire shaft which because of it's length will accept more degree's of twist before failure?. trying to understand this as a tradesman without a formal education.
Cal Poly doesnt give you that much hands on, any more than a basic overview of manufacturing processes is all up to you. I was always interested in making parts so I got a lot more out of it.

Sounds like you've got the basics down. Ever notice that the short side front shafts break more often than the long ones? The shorter axles cannot twist and absorb as much energy as the long ones so they see higher stresses and failures.
 
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