Square Front Driveshaft Question

[BRUTUS]

I like the idea of the square tubing for the front drive shaft.....

I'm throwing this idea out there.... my bushhog has a square "solid" inner shaft with a square hollow outside. May be something to think about.

I had never thought about ag shafts because I figured that ag shafts didn't use anything as big as a 1410 joint. I am gonna have to check them out.

[sjlplat]

I used two different types of yokes for my square shaft. Used a standard 3" 1350 fixed yoke, ground to fit inside the larger tubing, then used a 1350 slip-yoke, and ground that down to fit inside the smaller tubing. Everything was pressed at 20 tons, and welded at the seams.

[worn4wd]

break down and get some DOM tubeing and a slip joint from your local spicer rep and just make a "real" driveshaft. if money is an issue just get one at the junkyard that is longer than you need, and cut it down.
i usualy do the later, because i'm cheap!
good luck

[Dmntxn77]

I had thought about that but the larger tube does not even begin to fit over the yoke.

I know that is does not go over it, but from the pics, it looks like you would still get some fresh weld surface...

[rustywagoneers_com]

break down and get some DOM tubeing and a slip joint from your local spicer rep and just make a "real" driveshaft. if money is an issue just get one at the junkyard that is longer than you need, and cut it down.
i usualy do the later, because i'm cheap!
good luck

the slip yoke from the spicer dealer won't have any more LENGTH of slip than the one he is taking out.
leafs can flex great, but the axle will follow a different arc than the driveshaft, there fore we need a slip element (usually a splined section)

however, if one uses square tubing such as described, you can have nearly as much 'slip' as half the length of the driveshaft. (for really flexy leaf suspensions, and some link systems that don't follow the arc of the driveshaft)

peace
Dave

[sjlplat]

the slip yoke from the spicer dealer won't have any more LENGTH of slip than the one he is taking out.
leafs can flex great, but the axle will follow a different arc than the driveshaft, there fore we need a slip element (usually a splined section)

however, if one uses square tubing such as described, you can have nearly as much 'slip' as half the length of the driveshaft. (for really flexy leaf suspensions, and some link systems that don't follow the arc of the driveshaft)

peace
Dave

That pretty much explains it. I went through 2 different slip yokes before I decided to go square. My rig was pulling the slip yoke clean off the splines. They just don't make off the shelf slip yokes with enough slip for my rig. The only choices I had were custom splines, a limiting strap, or square. I went the cheap route, since I had already dropped a good $600 in the front driveshaft.

[83 BEAST]

WOW!!!! that sucks!

[Brown Bear]

Ironically enough.. I am a "redneck" by upbringing and a degree'd mechanical "engineer" by trade.

Speaking as a fellow ME in training, I would do the force analysis on this shaft: square vs round, butt weld vs milling, cross sectional area reduction, heat concentrations, and stress concentrations due to various machining efforts before I touched one piece of metal to another. These types of analysis, as you know, can be done quick and dirty without too much sweat, and might lead you to other avenues of thinking such as sleeving the yoke to the shaft. Two things I would be worried about are the stress concentrators induced by the yoke, and the sheer stress at the joint between the differing cross sectional areas of the yoke and the tubes. I might even do a quick and dirty analysis of the minimum I needed to resist the torsion that shaft will see if say a front wheel gets jammed.

But then again, I do these sorts of things for s###ts and giggles all the time

[jeepzilla47]

not an engineer by trade, but i have worked with alot in my industry...(papermill general mechanic)....i have seen alot of things that should work on paper, but dont in the real world.......and i have also seen things that absolutely should not work, but have been for many years......

i would machine the yoke to accept the smaller tubing.......weld it, then make you a collar to slide over the tubing and weld up to the yoke....

anyway, just my .02

i like the ideal of the ag shafts, but at the time, i could not find a crossover joint......(i have limited rescources)....maybe somebody could come up with some numbers.....

[jtr]

I am an engineer by education/trade and I have found that sometimes you have to try things out.
Burn it in......it was cheap fix anyway. Go wheelin.

[BRUTUS]

I guess my question is ...after all the money you have spent on Axles, lifts, transmission and doubler why get cheap now? A high quality, balanced, warrantied drive shaft is peace of mind.

I don't see it as any compromise as far as quality goes. Did you read this:

I went through 2 different slip yokes before I decided to go square. My rig was pulling the slip yoke clean off the splines. They just don't make off the shelf slip yokes with enough slip for my rig. The only choices I had were custom splines, a limiting strap, or square. I went the cheap route, since I had already dropped a good $600 in the front driveshaft.

If that doesn't say it all I don't know what will.

[HeepofaJeep]

Speaking as a fellow ME in training, I would do the force analysis on this shaft: square vs round, butt weld vs milling, cross sectional area reduction, heat concentrations, and stress concentrations due to various machining efforts before I touched one piece of metal to another. These types of analysis, as you know, can be done quick and dirty without too much sweat, and might lead you to other avenues of thinking such as sleeving the yoke to the shaft. Two things I would be worried about are the stress concentrators induced by the yoke, and the sheer stress at the joint between the differing cross sectional areas of the yoke and the tubes. I might even do a quick and dirty analysis of the minimum I needed to resist the torsion that shaft will see if say a front wheel gets jammed.

But then again, I do these sorts of things for s###ts and giggles all the time

Holy CRAP! Why don't you do an FEA & full engineering report while you're at it. In the time it took you to do the calculations you could have just butt-welded it together & tested it in the real world

I am an engineer by education/trade and I have found that sometimes you have to try things out.
Burn it in......it was cheap fix anyway. Go wheelin.

No kiddng. Weld it up, and hit the trails. The time you've spent just typing up in this thread could have been used to build the driveline .

Toyota guys have been doing it for years-- it works, may not be the best balanced, but I doubt you are pre-running in 4wd .

Machining it would be cool, but I think there are other parts I would rather have machined if I had access to the equipment

[sjlplat]

I guess my question is ...after all the money you have spent on Axles, lifts, transmission and doubler why get cheap now? A high quality, balanced, warrantied drive shaft is peace of mind.

My rear driveshaft is a quality, balanced, warrantied CV shaft. I have dropped the entire weight (5k lbs) of my rig on the front driveshaft without any evidence of damage. The rear driveshaft can't handle anywhere near that amount of abuse.

When it comes to a rear shaft, It's important to ensure it is balanced if it will see any street driving. As far as a front shaft goes, it doesn't spin fast enough (Unless you've got slugs or full-time 4wd) to need balancing.

[Brown Bear]

Well, it could work, for awhile, or it could work forever. I'd feel more comfortable seeing numbers telling me it will still be working in 6 months time rather than finding out 3 miles deep on a trail full of mud. If you have the tools at your disposal, it seems like a shame to waste them.

[DAHoyle]

My 2 cents worth.. I like idea number one better, and would persue that course if I had the means, not so much for a strength reason, just that it could help to index and phase the driveshaft. From a strength standpoint, I'm quite certain that either technique will work and most likely not be the weak point in the drive line.


For the record.... There's way too much negative discussion in this thread by naysayers, when this technique has been in use for quite some time. This is getting reall close to the Duraspark/HEI debate. Both sides have merit. As far as all the "experts" talking about doing a failure analysis and such, Throw your numbers on the table. I'm doubtful that you can come up with even half of the variables, but give it a shot. The man asked a specific question, about a specific design element, not wether he shold buy a $1000 custom drive shaft. If you don't have an opinion specific to his question, then start your own thread to discuss the merits of a square drive shaft.

The very fact that it surprises some of you that someone would even consider it, means you aren't quite the vanguard of 4X4 fabrication data you seem to think. They have been in use, successfully, for quite some time.