Custom Billet Axle? Drag Racing V's Sled Pulling

I got a good friend that runs a mod 4x4 gasser with an HQSD in the rear and he could get a handfull of runs out of stock axles, then he bought a set of custom axles from a well known supplier and broke them the first pull! So their is more to making axles live in truck pulling. He runs 300m now and works good!
 
brushpuller said:
I got a good friend that runs a mod 4x4 gasser with an HQSD in the rear and he could get a handfull of runs out of stock axles, then he bought a set of custom axles from a well known supplier and broke them the first pull! So their is more to making axles live in truck pulling. He runs 300m now and works good!
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Sure...could totally be explained by the heat treating method and recipe.

In the commercial world, if I were buying axles, I would want to see hardness tests done on the actual pieces to be sure the heat treater did exactly what I told him to do. The easy thing to do is to make the axle blank 1" longer and cut a sample off. You can then polish the cross section and take hardness measurements from the skin to the core to see if the profile is what one would expect from any particular alloy.

Go too hard, and the tensile strength is great, but you enter brittle fracture mode which makes the axle very sensitive to surface defects.

Go too soft and you get twist, then bang.

Don't get me wrong, I'm not bashing anyone here, but I think some axle vendors know next to nothing about the materials or the processing. If the heat treater says "this will work," then he's told you next to nothing. If he says "these tested to 180ksi tensile with 9% elongation and it's 38 HRC on the OD to 35 HRC in the core," now that's some data you can work with.

I just hate to see people paying big bucks for parts that are so unspecified. Hardly anyone has the means to test the materials, so vendors can tell as big a lie as they want and blame something else when it fails, and the warranty is zero. Bad deal all the way around.

There should be very little voodoo in axle making.
 
outlaw99 said:
this is where i got my info, idk I just read what he said, like I said I havent ran them it was just a idea.

http://www.dutchmanaxles.com/Tech1.html
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Yeah, I wasn't dishing on you personally.

I don't totally agree with what he's saying and he presents no data. The 4340 shaft he uses as a comparison, how was it heat treated? Hmmm...

Now, I can see where an axle with a 44" rock crawler tire does put more axial bending moment in the shaft than a typical puller truck would. (on edit, now I'm not even sure this is true with FF axles unless the bearings are shot...the axle is so slender, it would bend like pasta anyway in that direction).

The other thing too, is that there are multiple quality levels of all these alloys, air cast vs. vacuum melt, etc., which all make a significant difference. To do a heads-up pure A-vs.-B comparo would take a lot of work.

This is one reason airplanes are so bloody expensive. You want to intro a new part into a landing gear, you have to test the everliving crap out of it to show proof.

In the sledpulling world, it's "here, deez be good".
 
I have a custom set of moser 4340 axles in my truck, I dont know how they will hold up but i will find out, I never broke a stock axle but that might have been luck..lol
 
outlaw99 said:
I have a custom set of moser 4340 axles in my truck, I dont know how they will hold up but i will find out, I never broke a stock axle but that might have been luck..lol
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I've got what Moser said were their strongest axles for a Dana 80 and that I can't break them. Not sure on the material, but I guess we'll see how they work this season, LOL
 
outlaw99 said:
I have a custom set of moser 4340 axles in my truck, I dont know how they will hold up but i will find out, I never broke a stock axle but that might have been luck..lol
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What makes them custom? I thought moser was producing axles for the AAM now.
 
oh didnt know that, last time I checked with them they werent producing them. but thats been awhile ago.. so they offer them now on there lineup?
 
outlaw99 said:
oh didnt know that, last time I checked with them they werent producing them. but thats been awhile ago.. so they offer them now on there lineup?
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I am not 100% but there are some others who have gotten AAM axles from them.
 
It's pretty simple really, and it goes straight back to power.... as always.

Power per power drag racing will never destroy driveline like a pulling truck. A drag driveline only gets full abuse coming off the line. As soon as the first shift is made the torque starts dropping substantially.

Again, it's all based on power. Torque @ Rpm.

Figure for a drag race truck crossing the traps running say 130mph. Or hell, lets say mid-track at 100mph.

Now say you're putting 1200rwhp to the ground with this thing at the 100mph on 29" drag radial tires. Axleshaft rpm at 100mph with that tire is 1666rpm.

1200rwhp @ 1666rpm = ~3783ft/lbs of torque on those axleshafts.


Now take a sled puller with a 35" AT running say 50mph tire speed with the same 1200hp at the ground. A 35" tire will be turning 490rpm at 50mph tire speed (assuming the measured distance from ground to hub is 17.5" going down the track with the weight on the truck).

1200rwhp @ 490rpm = ~12,862ft/lbs of torque applied to the axleshafts.


Pretty simple math there.



Now what really matters aren't either of those loads as they are both well within the strength for a stock axleshaft in any 1 ton truck.

The loads that matter are the shock loads of course, where those numbers can easily be doubled, trippled or more.

This happens for a drag racer at the launch. And after that, only the subsequent gear shifts cause shock loading, although to a much lesser degree.

Although you're still shock loading a shaft with a static load at part track of say 4000ft/lbs vs one on a pulling truck at over 12,000ft/lbs. 2 or 3 times 4000 and you're just getting up to the kinds of loads the pulling truck axleshafts are seeing under ideal conditions.

Rpm. The rpm for the pulling truck axleshafts dictate that a pulling truck axleshaft will have to tolerate FAR more abuse. Because we all know they don't pull smooth and even but once in a blue moon. Most times they're hoping and barking down the track with tires coming completely off the ground not being rare, but standard.

Pulling truck beats drag racer on axleshaft abuse multiple times over, power per power.
 
Yes, unless Moser has stepped up their game considerably, the axles of theirs I seen in an AAM (duramax pull truck) didn't last much, if any, longer than a stock axle.


C-ya
 
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