Ok, bear with me guys, I was thinking since the last cv/shaft I broke, I know it did hurt to think that long. But from what I have found, the short side cv/shaft seems to fail more often than the long side. Logic would say, that becasue the short shaft is shorter by quite a bit, that it has a lower yeild point than the long shaft. And in my experience, if you watch a rover climb a ledge, you will see the front left tire sortof stop for a breif moment, and then it jumps back in the game. So that means the long shaft is twisting a bit yet still under its yeild point, and the short shaft is having to make up for it.

So lets say you upgraded both the front shafts, and maintain stock CV's for (comparison). You will stil be getting the same effect, but the yeild points have changed. However, now the CV will break sooner, as there is less give in the system. But what if you simply upgraded the long shaft. Supposing the long shaft had the same give and yeild of the short shaft, you would have less stress on one cv, thus one set of CV's might last longer. so if this were true, which I beleive it to be, the ideal thing would be to upgrade both CV's, and only the long shaft. Or upgrade both shafts, but tune the shafts properly so that they give and yeild at the same point. Make since guys or am I a loon.

FLAME SUIT ON AND READY. Give me every thing you got 9V since you are the expert.
:rolleyes: :rolleyes: :rolleyes: :rolleyes: :rolleyes:

Humm,

This sound very much like the rear axle in a series rover debate but in reverse. Basically my theory is that the long side will fail due to fatigue while the short will fail due to shock.


To answer your question there is no sense in making anything less strong that possible, no point in making anything equal as you may have a one time shock load on one side but not the other where when tuned equally it would break but set at max strength it would not. You follow.

So I would go for something flexible (like hy-tuff or 300m) for the axles to take the shock load off the cvs and make the cvs as hard as possible and screw tuning left to right

Ron

I see your point evilfij, but with a locked front end, and the wheeling I tend to do, shock load is not much of an issue. I tend to crawl every thing, and rarely give it the heavy foot. And when your crawling, and locked, lifted tires cannot accelerate more than the tire contacting the ground so unless your giving her all she's got, shock is not a real issue. I rarely see the front wheels stall, unless the front end is climbing a ledge, or is trying to pull the rear end over a ledge. Usually the front is slipping fairly easily, and the driver is steering searching for traction. The DS tire catches, and stalls, and the PS side tire is still trying to spin and catch. When the PS side catches traction, ideally the DS will catch too, but the PS loads the shaft faster, as the DS shaft is still loading up due to its length. This puts much more load on the PS shaft initially. I guess this could be catagorized as a shock load. But if they both load up equally, the stress will be on both CV's, giving them a chance to live longer. I dont completly agree with the upgrade to you hearts content, and see what is next in line to break. obviously its nice to break an easy to replace part, Like a fusable hub (not GKN hubs) but a hub that has a weak point so they break. I think I heard of some one talking about this idea once. I guess this may only apply to ideal situations.

I dont know man I was just curious what you guys thought. I dont break alot, so I guess this is not that big of a deal, but I thought it was a fun topic.

ramble mode off :D

Interesting point KC. If you watch the Cruces video I sent Bill R. you will see exactly what you are referring to(ledge on the first day where he broke the rear). The front wheels bias so much I thought for a second he didn't have his front locker on.

Roverwrench and Drew are working on the fuseable hub thing, check out the photos from Tellico, one of the last ones shows the flange/stub fuse. Sam noted that this is the trend for the rainforest competition guys.

Johnathan

thanks tis, so i am not crazy. I dont know to many people that watch in depth enough to catch this.
but guys dont get me wrong, i am not saying go out and remove your upgraded short shaft, I am just as poor as the next rover owner, and i always look for a way to save money and get similar results. I still run stock shafts all around. I am very easy on my truck, even thoght I have done more than most. Although lately I have been betting the snot out of it.

well heres all ive got :rolleyes:

using your logic it would seem that you would want to upgrade the short shaft, to kind of equal out the strength between the two.

unless what you are trying to do is create a weak link that you know will break before anything else?

the error that i see in this situation is that even if your weak link is the short side shaft, then there is still the very distinct possibility of breaking the long side since in many situations it would be doing more work and possibly past its breaking point. basically since you would only have a weak link on one side, your "strong" side so to speak, still has its own (expensive) weak link.

i think that the best solution is keeping a stock 24spline stub shaft with 30 spline inners and longfielded D110 CVs.

anyways, flame away :flipoff2:

the problem is not the shaft so much as it is the CV. if you upgraded the short shaft, you will break more short shaft CV's But if you upgraded the long shaft, you are loading up the long shaft more, thus loading the cv on the long shaft more thus reducing the load on the short shaft thus reducing the load on the short shaft CV. Its similar to using extension with impact guns. The longer the extension, the less torque you are putting on the socket, thus you may not be able to break the nut loose
(I know thats bad, is merv on tonight) But if you use a short extension, or no extension at all, you will break the nut loose with ease. the longer the shaft, means more energy is being lost. So fewer CV's break on the long side than the short side due to energys nature to expell itself as easily as possible. You simply do not have the same amount of torque on both sides of the axle. And if one has to make up for the other, and you have problems with parts being on the verge of breaking all the time, you can imagine the breakage in store for your next trail ride. Or in my case the next time I drive out of the shop with the truck in low diff lock and try to turn around to park. thats how my old CV broke, and it was the short side, due to fatigue. I plan on running the long side for at least another season, then I will replace the CV for safety, and keep the old fatigued one as a spare. Make since 9V

makes sense. so what you want is a material that is highly elastic yet very strong, so that it will twist alot (ideally infintely, but thats not possible) instead of breaking.

it is a very good idea but you will have to play around with it. as many have stated to me in the past "theory is not always reality" :D

How is this for alot of twist - in excess of 720 degrees

Billster

Another shot of the same thing. And consider that all that twist inside of the oil seal did not break it. Only the twist outside the oilseal broke it (much less twist to break a much shorter portion of the axle). Hmmmm.

Billster

So what are you saying Bill. I assume you are just showing us how much a shaft can twist. especially as that is the long side, and it suports my theory that the short side transfers more torque to the cv. Imagine the energy required to twist that shaft. That is energy that could have been transfered to the CV and translated into drive, that might have reduced the stress on the short side. But in that case bill I think that it was the shafts time to go, or the shaft was not capable of handling what you gave it. What was that shaft (make), I remember you showing it to me awhile back, but I cant remember. I would be curious to hear how many short cv's you broke vs long, and what condition the short shaft was in. I would guess the short shaft is nice and straight, and I know you blew at least one CV on the short side, and one on the long side. Or have you only blown the long side I remember the long side in Fruita.

Of course there would be exceptions to this rule, and driving style would make a big diff. And type of wheeling done. Extreme climbs with weight on only one front tire bypasses this theory, and I would opt for heavy hardware on both sides.

But imagine if you had one of those rotoflex couplings on your rear drive shaft, and you know how much those flex under load, and all of that initial load to move the truck forward would be placed on the front axle. this would cause more stress on the center diff cross pins, and the front axle. Maybe it wouldnt fatigue anything to the breaking point, but it would be hard on the drive train. Especially once the flexable rotoflex catches up and un winds. It would start the cyle over again, untill it finally catches up with the front end.

PS bill the reason your shaft broke where it did i'm guessing is because, the longer section of the shaft has more yeild than the shorter section. the fact that the shaft twisted, proves you had enough force to yeild the shaft, and the shorter side of that shaft is most likely the same diameter as the longer side of the shaft, so it has the same yeild per inch. Meaning were the same material one inch long yeilds and breaks with say 10 degrees of twist, a two inch peice would require 20 degrees to yeild and break. that is why it seems that the twist is much more on the long side. Try measuring the short section in lenght, and then use a protractor to measure the angle at which the line you drew is. Then measure out the same distance anywhere on the long side, and measure the angle. I bet it has the same degree of twist per inch if the short section does not have more.

Now this is all pulled out of my arse, and is completely theory on my part, so guys dont take this as anything more than it is. I dont have any specs or tables or material charts etc. to back me up. I am guessing and hopefully I am some what right.

But it sounded good right guys.

How about the heat treatment of the axles being different at the ends than at the middle due to machining the splines?
The ends are torsionally stiffer and remain elastic, but the heat treatment from machining leaves them less plastic and more prone to fail. Just an idea :confused:


I would imagine that differing stress-strain relationships between the ends and the middle of the shaft as well as the loading rate plays a role. Imagine if both the ends and the middle have the same torsional yeild point (consider only as a torque, since it is already apparant the middle is very plastic while the ends are not at all):
the middle of the shaft can disperse this torque over a greater period of time (because 1. it has the potential to exhibit more angular displacement, and 2. this all occurs over time), thus capable of withstanding a greater angular impulse than at the ends. The rate of loading, up to and at the point of failure does make a difference in how steel fails. The middle of the shaft can potentially increase the time it is under torsional stress by deforming, thus decreasing the loading rate; the ends are not as capable of deforming and *may* reach peak deformation sooner, causing the loading rate to be greater.

Yeah...that's it...my vote is on time. At the ends, time isn't on your side :D

After further investigation...