Torque Multiplication and Shafts

ckruzer

ckruzer

Infidel
Joined
Jul 2, 2015
Location
asheville nc
So...

At this point, while I am completing interior etc Im trying to plan the next next phase of the build so i can begin collecting parts.

This next phase, I am collecting a 4L trans, winters shifter, and depending on my Atlas fund either the atlas or a used adapter for the np231

The next next phase would be addressing my axles for final build status. Whether that is mildly upgrading what I have and sticking to 37 reds, or hardcore upgrading for 39.5 or swaping housings completely.

Anywho.

To really understand my options with my current setup Im doing a little math. So called, these stock 30 spline axle shafts are rated for 6000 some odd ft/lbs, while oem antique metallurgy 35 spline is rated for 8900 ft/lbs.

(Note: I have 79 f250 44/60)

So

300ish ft/lbs from the LS, by 3.83 first gear, by 2.72 np231 (possibly more with atlas), by 4.88 r/p ratio = 15,xxx ft/lbs.

Am I understanding this right? That even stock 30 and 35 are grossly unprepared for the torque multiplication in offroad environments? After market 30 spline would put me in the neighborhood of 10,xxx ft/lb rating, while aftermarket 35 spline would put me around 14k.

I feel like I am missing something.

Thoughts are welcomed!


My original plan and design and *want* was a 3/4 ton very capable offroad rig that could easily get ice cream or go to the beach whenever I wanted or drive to Harlan, have fun, drive smart, and fix a ujoint or shaft at most and drive home.

Ive looked up 44/60 hybrids and boring the 30 spline 60 to accept 35, but both routes will exceed a simple 500$$ upgrade per axle budget that I want. Exceeding it to the point it would be cheaper to sell the current axles and get "real" tons, which then also require the same budget to mildly mod out. Which still exceeds my original intent and budget
 
EDIT: by mild upgrade currently with what I have, research suggests a vision of truss, chromo inner/outer and ujoint upgrade
 
My understanding is that you also would adjust for loss of power in the drive train, most people say 10-15% depending on type of trans you run. And you would also divide the finally torque number by the number of axle shafts that will receive the torque, in your case 4.
But I may be way off on this......
 
@jeepinmatt (I think it was) and I talked about this a while back in a thread and The way I think I understand it is...
Think of a barstool with 4 legs. If all 4 legs are on the ground (100% traction) the load will be distributed evenly to all 4 legs. If only 1 leg is on the ground, that leg will see the full load.
I would think that if you only had one tire on the ground with 100% traction and were at full throttle/peak torque and you broke a shaft, you kind of deserve it.
 
junkxj said:
My understanding is that you also would adjust for loss of power in the drive train, most people say 10-15% depending on type of trans you run. And you would also divide the finally torque number by the number of axle shafts that will receive the torque, in your case 4.
But I may be way off on this......
Click to expand...


that makes more sense. so I am looking at roughly 7,xxx ft/lbs per shaft when in 2wd. So not including shock issues, if i were to upgrade the shafts I should be "mathematically" covered?

RHSCTJ said:
@jeepinmatt (I think it was) and I talked about this a while back in a thread and The way I think I understand it is...
Think of a barstool with 4 legs. If all 4 legs are on the ground (100% traction) the load will be distributed evenly to all 4 legs. If only 1 leg is on the ground, that leg will see the full load.
I would think that if you only had one tire on the ground with 100% traction and were at full throttle/peak torque and you broke a shaft, you kind of deserve it.
Click to expand...

Now that is the missing piece I wasnt recalling.
 
RHSCTJ said:
@jeepinmatt (I think it was) and I talked about this a while back in a thread and The way I think I understand it is...
Think of a barstool with 4 legs. If all 4 legs are on the ground (100% traction) the load will be distributed evenly to all 4 legs. If only 1 leg is on the ground, that leg will see the full load.
I would think that if you only had one tire on the ground with 100% traction and were at full throttle/peak torque and you broke a shaft, you kind of deserve it.
Click to expand...

The prime example of this, would be a tire getting caught in an undercut. The traction increases extremely quick.

yes, you should be ok.... But shock loads are the real issue. As the tire grabs suddenly, the shock load transmits in reverse against your traction load, which works against each other. Sticky tires make this worse, if you do not use them to your advantage.
 
Yep, in "normal" conditions, its hard to generate enough traction on dirt and rock to actually resist 15,000ft-lbs of torque, which is why your tires spin. The biggest problem, like @paradisePWoffrd said, is when a tire gets wedged, or when you are bouncing and quickly loading and unloading the traction on a tire.
 
To build on this a little more, lets say a normal offroad tire is 36", which gives a radius of 18"=1.5ft. So 15000 ft-lbs results in a force of 10,000lbs to push you forward (15,000ftlbs*12"/18"). If you're rig weighs 10,000lbs, and you're trying to send it straight up vertically, then the resistance would be equal, and the rig would not move (and something would probably break). But, generally speaking, unless you are @GONOVRIT, you can't drive straight up vertical walls with full traction, so the force required to move the vehicle is reduced. On a 30 degree angle, the force required to move the vehicle up a hill is exactly half the weight of the vehicle. So your 5000lb rig requires greater than 2500lbs of force to move. The next component is acceleration, because you don't want to move at a snails pace. I don't feel like typing or thinking about this anymore because then I'll have to convert ft/sec/sec to mph/sec. F=ma and KE=1/2mv^2 is where it goes from here, and the number of variables is infinite, but the main point is, finesse keeps a lot of parts together because you don't need 15000ftlbs to keep the vehicle moving.
 
There is also a safety factor that makes the actual failure torque higher than the rated torque. That would be a pretty hard spec to find, but as long as you're staying on the conservative side of the rated torque, the safety factor just gives you extra ....err.... safety factor.
 
With that noted I feel more comfortable wheeling what I got for now and simply acquiring some HD spicer or chromo shafts.
 
Loganwayne said:
Well go get super duty axles they are pretty cheap


Sent from my iPhone using Tapatalk
Click to expand...
He better plan on linking the front while he's at it... they're springs are way outboard.
 
ckruzer said:
With that noted I feel more comfortable wheeling what I got for now and simply acquiring some HD spicer or chromo shafts.
Click to expand...
Step up to chromos with superjoints or RCVs. Spicer joints and shafts aren't going to last with decent tires.
 
Jody Treadway said:
You know how when this topic comes up, members tend to say "Go with a 14 Bolt".

30 spline 60s take way too much $$$ and effort to make last. When you can buy and build a 14 for half the cost.
Click to expand...

x2. You can also pick up sterling axles with disk brakes to match that superduty front axle for 250 bucks. I think the sterling axle is one that doesn't get the attention it deserve.
 
Jody Treadway said:
You know how when this topic comes up, members tend to say "Go with a 14 Bolt".

30 spline 60s take way too much $$$ and effort to make last. When you can buy and build a 14 for half the cost.
Click to expand...

exactly. i already have a 14b but i believe the internals have rusted away too much for use. before long i will start a d60/14b build to have on the side ready, but until then been pondering ways to smartly upgrade the metallurgy for now.

its really hard to come to terms with - but the reality is I will just collect a few spare shafts and enjoy whats there for now. i got too much to buy/do before revisiting axles. lol
 
ckruzer said:
exactly. i already have a 14b but i believe the internals have rusted away too much for use. before long i will start a d60/14b build to have on the side ready, but until then been pondering ways to smartly upgrade the metallurgy for now.

its really hard to come to terms with - but the reality is I will just collect a few spare shafts and enjoy whats there for now. i got too much to buy/do before revisiting axles. lol
Click to expand...

Coins are considered metallurgy, correct?
Don't waste them on a 30 spline 60. Been there, done that. Spent the better part of a day at Harlan getting 30 chromo Dutchmen splines out of a welded carrier.

Those rusted 14 Bolt internals will all be replaced with different ones most likely anyway. All I reused from mine was the housing, hubs and wheel bearing hardware.
 
Jody Treadway said:
Coins are considered metallurgy, correct?
Don't waste them on a 30 spline 60. Been there, done that. Spent the better part of a day at Harlan getting 30 chromo Dutchmen splines out of a welded carrier.

Those rusted 14 Bolt internals will all be replaced with different ones most likely anyway. All I reused from mine was the housing, hubs and wheel bearing hardware.
Click to expand...

The housing has been sitting open for about three years. no covers, ends open, sitting under a tarp outside. to my knowledge any type of bearing journal is long gone. it was for free so no loss. Im prob better off spending a bone or two getting another housing than braving that thing. lol. the shafts are prob recoverable tho
 
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