fine spline VS coarse spline

[GURU]

There is alot of good tech info on this thread.

Although not much of it is any good in the real world, any rover standard axle is weak and probably made of cheese. If you want any strength you need to buy aftermarket axles and hub flanges. Yes the salisbury axles 24 spline and 30mm diameter is the strongest stock axle, it is just so plan stupid when you know it is a dana 60 design diff, that normally start at 28 spline and can go up to something like 40 spline !!!!

Going back to the original post I would fit the 24 spline front housing for now, and if you don't plan on using the car for more than daily driving and light trips I would leave it. If you plan on going more serious off road you need to upgrade the centre to a 2 pin, 4 sun gear type (or a locker) and aftermarket axles and CV's (preferably chromoly) and drive flanges.

[red90]

... it is just so plan stupid when you know it is a dana 60 design diff, that normally start at 28 spline and can go up to something like 40 spline !!!!

Actually Dana 60s usually use 30 spline at the diff, which is only 15% stronger than Rover's 24 spline (with the same materials). You need to go aftermarket with them as well.

[snell40]

thanks GURU, good to get a straight answer
cheers dave

[red90]

Going back to the original post I would fit the 24 spline front housing for now, and if you don't plan on using the car for more than daily driving and light trips I would leave it. If you plan on going more serious off road you need to upgrade the centre to a 2 pin, 4 sun gear type (or a locker) and aftermarket axles and CV's (preferably chromoly) and drive flanges.

Hmmm... Front axles are more than just shaft size though. The CV joints in the later 24 spline front axles makes the whole setup weaker than the older 10 spline axles. Of course, the nice CV joints are cheaper for the later axles than the early ones.

[GURU]

yes the early CV's are bigger than the later ones, but you can convert to defender CV's which is the biggest stock CV again. But again to get more strength you would go aftermarket CV's or do some sort of conversion.

I would just run the 24spline front diff, the axle will be weaker than the smaller CV.


As for the stock dana axle only been 15% stronger than the rover axle, that may be true, but why did land rover make them 15% weaker???? Seriously, the stock dana axle is 15% stronger than the biggest, most strongest standard land rover axle ever made, so how many % stronger is it to a rover 24 or 10 spline axle?!?!?!?

[ISUZUROVER]

Dougal - you are welcome to come 4x4ing if you ever come over to Brisbane.

I try to drive with as much mechanical sympathy as possible, don't spin wheels unless they are on the ground, but I will try and drive up anything I think I can. I have broken:

in My 109 IIA
2x 10 spline axles (then fitted a salisbury) - the 2nd broke while driving around the Brisbane CBD.
1x 24-spline salisbury axle (then fitted a maxi-drive)
1x front ring and pinion
All on 32's with no lockers

In dad's 88" IIA, he or I have broken
2x 10-spline axles (one while coasting DOWN a hill on road)
1x rear diff.
All on 32s with no lockers.

JasonK on AULRO, drives with the most mechanical sympathy of anyone I know, yet in the years he has owned his IIA he has twisted at least one front, broken a few rears (then upgraded to MD axles), and a couple of ring and pinions.
All on 32's with no lockers.

The breakages on-road and while driving downhill prove what John said about fatigue.

I have seen countless failures of 24-spline axles in locked and unlocked vehicles - usually rangies and discos. As John stated (I had forgotten that) one of the members of the LROCB cast poly drive flanges to sell to members, as axle breakages were so common on trips. Many LR/4x4 owners think the LROCB guys drive like pansies offroad and don't do anything difficult (which is part of the reason another club was started further south) - yet they still break these axles which supposedly should hold up.

[red90]

yes the early CV's are bigger than the later ones, but you can convert to defender CV's which is the biggest stock CV again. But again to get more strength you would go aftermarket CV's or do some sort of conversion.

The problem with the later axles is the shaft is very small (smaller than 10 spline) where it enters the CV.

However, you can replace the CVs and shafts for $660 USD from Rovertracks, so the upgrade cost is quite low.

[cloughy]

Dougal spins his wheels on asphalt and don't break axles

[KiwiBacon]

OK, firstly, I'm a mechanical engineer and I don't need to be told the math. A coefficient of friction of 1.0 is not "perfect traction". There is nothing magic about 1 and higher is quite possible. I can guarantee you can easily produce greater force at the wheel surface than the weight on the tyre when off road. The wheels just need to sit behind a small ledge. A lug just needs to catch an edge. The low pressure tyre wrapping around a rock. There are many instances to allow the tyre to be able to force beyond the weight on it. Everytime you fail a hill climb on steep, high traction surfaces, the wheels spin and can grab and catch rocks and ledges with loading that is very high. A little jolt into the plastic range and there goes another 5% of the life of the shaft.

That's good, I'm a mech eng too.
You can't get traction above 1 on-road with 4wd tyres, let alone off road. Normal road tyres on dry tarmac let go around 0.8. If you've got sticky hot tyres on road you can hit a little over 1, but offroad not a snowballs chance in hell. If you have any data on this let me know.

10/24...good lord, those snap like preztels. I was following an 88 a couple of years ago and bang on a tiny incline, just driving along the trail. The fatigue adds up and they fail whenever. I thought we had been talking about late model 24 spline shafts. I don't "personally" run stock shafts, so have broken none of them.... As clearly stated, this is other people in stock vehicles. I can think of six failures of people I know personally, 3 in Australia and 3 here in Canada. Just normal moderate off roading. Normally when they fail they are not doing anything special as the failure mode is cumulative. It is usually a toss up if the crappy cross pin on the diff will break first or the shafts.

88's and 109's do not use the same shafts as a rangerover, disco or 90/110. Has something been lost in translation here?
I worked with one guy who kept breaking 88 rear drive-shafts (like lost count how many). He replaced the rear axle with a salisbury and found the original axle casing was bent. It wasn't drive torque breaking his shafts, it was misalignment.

All I can guess is you've never driven on anything close to high traction and steep. It is probably best if you don't go wheeling with Ben or myself.

We don't have both steep and hi-traction here. We have plenty of steep, but the rock isn't high traction unless tyres and rocks are clean, they never both are. Next time I get over to Brisbane I'll take up the offer, but it's been 10 years since the last visit and it won't be this year either.

[ISUZUROVER]

88's and 109's do not use the same shafts as a rangerover, disco or 90/110. Has something been lost in translation here?
I worked with one guy who kept breaking 88 rear drive-shafts (like lost count how many). He replaced the rear axle with a salisbury and found the original axle casing was bent. It wasn't drive torque breaking his shafts, it was misalignment.

88's and 109s do use 10-spline axles though, same (siameter and spline profile) as a RRC, yet they have about 50 Bhp on a good day, not much torque and 40:1 1st low vs 48:1 for a 4-speed RRC. Is your argument that all the failures in these are due to bent axle casings?

As John said much earlier, in most cases it isn't torque breaking axles, it is fatigue.

[KiwiBacon]

88's and 109s do use 10-spline axles though, same (siameter and spline profile) as a RRC, yet they have about 50 Bhp on a good day, not much torque and 40:1 1st low vs 48:1 for a 4-speed RRC. Is your argument that all the failures in these are due to bent axle casings?

As John said much earlier, in most cases it isn't torque breaking axles, it is fatigue.

[/quote]

Yes they use the same spline, maybe they're the same diameter but there appears to be little correlation in strength or fatigue life. Yes RRC's and discos break axles, but generally while doing the things that you expect will break axles. No I'm not saying all 88's have bent axle housings, just recounting a relevant story. My RRC had 330,000km on the clock when I removed the old 10 spline axles, I know it's been wound back but I don't know exactly how far, it's likely those 10 splines did between 400-500,000km. 1000km of those were driving with a bent rear axle case (4mm toe-in, all on the left side due to a crimped axle end just behind the stub flange). I'm honestly surprised I didn't break an axle then, but it survived fine.

In summary, 88/109's and rangerovers/discos axles are not the same thing or the even the same strength. Does anyone have a torque to failure test like Ashcrofts for the 88/109 axles? Regarding fatigue, I've mentioned many times in this thread that the 24 spline axles are a far better design for resisting fatigue failure.

[uninformed]

ok im NOT a mech eng..... but would the fact that the rrc and disco is fulltime 4wd be more forgiving and sharing of load when on road than a 2wd series that the series sees more fatigue life and lends itself to braking earlier off road??????

[KiwiBacon]

ok im NOT a mech eng..... but would the fact that the rrc and disco is fulltime 4wd be more forgiving and sharing of load when on road than a 2wd series that the series sees more fatigue life and lends itself to braking earlier off road??????

It helps when the diff is unlocked, so onroad, towing etc. But offroad with the diff locked it's all the same, but worse because the RRC's and disco's are heavier and have more power.

[uninformed]

ok im NOT a mech eng..... but would the fact that the rrc and disco is fulltime 4wd be more forgiving and sharing of load when on road than a 2wd series that the series sees more fatigue life and lends itself to braking earlier off road??????

It helps when the diff is unlocked, so onroad, towing etc. But offroad with the diff locked it's all the same, but worse because the RRC's and disco's are heavier and have more power.

yeah I ment on road.....I think alot think that fatigue is only during serious offroad.....but using it as a work truck and normal life on road would also contirbute....hence the series being worse than the rrc and disco....maybe even things like suspension come into play.....what about all those series with FWH up front.....those moving parts no moving slowly getting surface rust which could be the starting point for a stress riser????

just my thoughts.....

[cloughy]

Fact is, for those of us that aren't mechanical gingerbeers, rover axles are crud, metallurgy was not something the poms were good at and the piles upon piles of broken axles and diffs....literally in the hundreds of components I've personally had, mean they suck

I've literally been and broken diff components on command "hey, watch this" rev, snap, on standard tyres

I've heard the stories, blah blah, drive accordingly, amazing the red faces that come in, when something finally goes

[red90]

You can't get traction above 1 on-road with 4wd tyres, let alone off road. Normal road tyres on dry tarmac let go around 0.8. If you've got sticky hot tyres on road you can hit a little over 1, but offroad not a snowballs chance in hell. If you have any data on this let me know.

Perhaps you need to go back and read what I wrote. I stated you can achieve higher than weight force at the tyre surface off road. This is NOT due to a friction coef higher than 1.0..... It is due to geometry. The tire is behind a ledge. The tire lugs are hooking onto rock. The tread is conformed around rocks. The tyre loses traction, spins and dynamically grabs an edge. All of these can produce these higher forces and they do.

We don't have both steep and hi-traction here. We have plenty of steep, but the rock isn't high traction unless tyres and rocks are clean, they never both are. Next time I get over to Brisbane I'll take up the offer, but it's been 10 years since the last visit and it won't be this year either.

I'm sorry, but you cannot have steep without high traction... That is just the laws of physics. Steep is when you are close to rolling over backwards. I'll let you figure out the math for the required friction coefficient versus grade.

[KiwiBacon]

Perhaps you need to go back and read what I wrote. I stated you can achieve higher than weight force at the tyre surface off road. This is NOT due to a friction coef higher than 1.0..... It is due to geometry. The tire is behind a ledge. The tire lugs are hooking onto rock. The tread is conformed around rocks. The tyre loses traction, spins and dynamically grabs an edge. All of these can produce these higher forces and they do.

I read what you wrote and I don't agree with it. Even a square tyre lug biting a square piece of rock can't get friction higher than 1 offroad. The rubber deforms around the rock and slides off. If you have some measurements to prove otherwise I'd like to see it.

I'm sorry, but you cannot have steep without high traction... That is just the laws of physics. Steep is when you are close to rolling over backwards. I'll let you figure out the math for the required friction coefficient versus grade.

Righto, here's an impossible example for you. Steep enough to roll and low traction:



The funny thing about this thread is people who don't own a rangerover or disco and hence have never broken anything on them, trying to convince owners just how weak they are.
See I know just how weak they are and to date I've managed to stay on the "no breakages" side of that line. If you think it's so easy to break one then go find a rangerover, grab a video camera and show us just what it takes.

[cloughy]

. If you think it's so easy to break one then go find a rangerover, grab a video camera and show us just what it takes.

What about posting the wheelspinning ability video first?


Who's posted that hasn't owned either a disco or rangie?

[red90]

I read what you wrote and I don't agree with it. Even a square tyre lug biting a square piece of rock can't get friction higher than 1 offroad. The rubber deforms around the rock and slides off. If you have some measurements to prove otherwise I'd like to see it.

Let's pretend you went to school. How can someone transmit a force from one object to another where friction is not used?? You produce NORMAL forces from the tyre to the surface, so friction is not the only thing restraining the tyre. Draw yourself a picture of your square tyre and add the force vectors.... Hmmm, they are not parallel with the friction surface. Now sum the forces to produce a total torque.

Why is it impossible for you to believe all of us who have been wheeling for many years and have seen many breakages IN PERSON??

[KiwiBacon]

Let's pretend you went to school. How can someone transmit a force from one object to another where friction is not used?? You produce NORMAL forces from the tyre to the surface, so friction is not the only thing restraining the tyre. Draw yourself a picture of your square tyre and add the force vectors.... Hmmm, they are not parallel with the friction surface. Now sum the forces to produce a total torque.

Show me a diagram of your wheel catching a rock and you will see the problem yourself. Put simply you can't grip a tyre with anything but friction or a socket on the wheel-nuts. You're not talking about wheel nuts so friction is the only thing left. Friction that occurs between the tyre and whatever it's contacting, regardless of the size or shape.

I've never mentioned a square tyre, you started this scenario and now you're ridiculing it? BTW you don't sum forces to get torque, it's force*distance.

Why is it impossible for you to believe all of us who have been wheeling for many years and have seen many breakages IN PERSON??

You were talking about broken 88 axles and I'm really happy you've seen them break, but this topic isn't about 88 axles. This is about the difference between 10 and 24 spline rrc/disco axles. I happen to own both and have a very good idea of what they can take and what they can't. Yet you have a problem with this, that problem seems to centre around the axles fitted to a landrover 88 many years ago.

[ISUZUROVER]

Dougal, usually your arguments are sound, but I don't know what you are smoking on this one.

Have a look at this vid:
http://www.youtube.com/watch?v=jobHVxA2hv8" onclick="window.open(this.href);return false;
By your calculations, this jeep should not have been able to break an axle. The conditions were wet and muddy, and I can't see any lifting/spinning going on.

EDIT: Another example - notice the jeep slides backwards down the hill (probably because of all the dirt dug up). Again no lifting and spinning, the wheel stays on the ground, but he is trying to drive forward while the tyre slides back into an obstacle. I have personally seen RRCs and Discos break rear axles in similar scenarios.
http://www.youtube.com/watch?v=nRHwjCYMlbM" onclick="window.open(this.href);return false;

[KiwiBacon]

Dougal, usually your arguments are sound, but I don't know what you are smoking on this one.

Have a look at this vid:
http://www.youtube.com/watch?v=jobHVxA2hv8" onclick="window.open(this.href);return false;
By your calculations, this jeep should not have been able to break an axle. The conditions were wet and muddy, and I can't see any lifting/spinning going on.

EDIT: Another example - notice the jeep slides backwards down the hill (probably because of all the dirt dug up). Again no lifting and spinning, the wheel stays on the ground, but he is trying to drive forward while the tyre slides back into an obstacle. I have personally seen RRCs and Discos break rear axles in similar scenarios.
http://www.youtube.com/watch?v=nRHwjCYMlbM" onclick="window.open(this.href);return false;

Honestly both of those videos are impossible to see what happens. The comments do give an indication:

went to Rausch Creek on 12/29/07 and decided to go to the tank traps first..on the way out of them the drivers side shaft completely sheared off leaving the wheel free to come out. Axle breaks at around 1:30, cant miss it

Larry tries to climb the infamous "trench" and his jeep's rear D35 breaks the passenger side shaft, and inner spyder gears! It now has Detroit locker, superior axles, and 4.88 gears

I don't know anything about jeep axles. I did search for videos of rovers breaking axles but I couldn't find anything suitable.

I'm not saying rangerover and disco axles don't break. It's obvious many people have broken them. I'm saying if you keep to the original tyre sizes and drive them knowingly they hold up pretty well. Needless to say this comment has met a lot of resistance.

[red90]

OK, you are seriously an engineer? Look, you can transfer force without friction. "Normal" force. You must understand what that means if you are a mechanical engineer. If you are not capable of understanding this simple point, I give up. Is addition the force on the tyre can exceed weight. I'd draw you a picture, but I feel like I'm wasting my time talking to a closed minded person.

You are the one that mentioned a square tyre. I copied your quote.

I talked about broken late model 24 spline shafts (disco 1 and RRC). Ben talked about 88". Best you go back and carefully read things, because you seem lost.

I just measured a Disco 1 rear axle. 27.4 mm shaft diameter. This is the same size as the 10 spline. It has more section that the 10 spline but is 25% weaker than the 24 spline section.

[KiwiBacon]

OK, you are seriously an engineer? Look, you can transfer force without friction. "Normal" force. You must understand what that means if you are a mechanical engineer. If you are not capable of understanding this simple point, I give up. Is addition the force on the tyre can exceed weight. I'd draw you a picture, but I feel like I'm wasting my time talking to a closed minded person.

Okay, I've drawn a picture for you:


Normal force on a round tyre doesn't generate any torque. To get any torque on the drive axle you need a force applied at an angle that's doesn't intersect the axle. In the pic above the diagram on the right has a normal force and no resulting torque.
The diagram on the left shows weight reaction force and traction force (torque reaction). It also shows the direction of the drive torque and the relationship between these three vital factors.

In a nutshell, the torque you can put on the axle is the product of the weight on the tyre contact patch, the coefficient of friction and the radius of the tyre. Do you agree or disagree?

You are the one that mentioned a square tyre. I copied your quote.

No you didn't, the quote was "square tyre lug". The lug belongs to the tyre and has a square edge on it.

I talked about broken late model 24 spline shafts (disco 1 and RRC). Ben talked about 88". Best you go back and carefully read things, because you seem lost. I just measured a Disco 1 rear axle. 27.4 mm shaft diameter. This is the same size as the 10 spline. It has more section that the 10 spline but is 25% weaker than the 24 spline section.

This was all covered in the first few posts, I stated the minor axle diameters were the same and even posted up a cad model of the axle showing the axle diameters in relation to the spline diameters. Keep up.

[ISUZUROVER]

Dougal, there are plenty of cases offroad where normal forces can be imparted:



Also imagine where the tyre is trying to drive through a v-shaped crevice significantly narrower than the section width of the tyre.

[KiwiBacon]

Dougal, there are plenty of cases offroad where normal forces can be imparted:

Certainly and if you want to go out and break stuff then tyre traps are a great way to do it. But that's not "driving it knowingly".

Also imagine where the tyre is trying to drive through a v-shaped crevice significantly narrower than the section width of the tyre.

Those don't seem to be that bad. Because they only pinch a short section of tyre at a time it doesn't take axle breaking twist to get out.

BTW here's a pic of my wagon a few years back, no rocks in the photo but plenty of them here held together by the clay/gravel mix you see. It drys concrete hard.

[ISUZUROVER]

Dougal, there are plenty of cases offroad where normal forces can be imparted:

Certainly and if you want to go out and break stuff then tyre traps are a great way to do it. But that's not "driving it knowingly".

I'm starting to suspect you are really a lawyer not an engineer...

Initially it was - you can't develop enough torque to break stock axles on stock tyres unless you lift/spin (shock loads). Now it is (not in so many words) well you can develop enough torque if you drop the wheel into a hole but you are an idiot if you do...

This is just getting silly. There are plenty of times when the only driveable line up a hill involves such obstacles, or you (accidentally) get offline through no fault of your own and end up in the same situation.

[KiwiBacon]

Initially it was - you can't develop enough torque to break stock axles on stock tyres unless you lift/spin (shock loads). Now it is (not in so many words) well you can develop enough torque if you drop the wheel into a hole but you are an idiot if you do...

This is just getting silly. There are plenty of times when the only driveable line up a hill involves such obstacles, or you (accidentally) get offline through no fault of your own and end up in the same situation.

And I'll happily say it again, "you can't break stock axles on stock size tyres without shock loads". Even If you want to play wheel trap you've got to either spin a wheel into one (i.e. shock load) or trap both tyres at once.

Basically if you drive stuff (or drive in a way) that breaks axles then you either upgrade them or find a cheaper hobby. If you don't break stuff, you don't bother upgrading. I don't understand what the problem is with that, what are you trying to convince me of?

[red90]

There are other ways to develop normal forces. I've explained them at least twice in this thread. Read back yourself as repeating myself three times is ridiculous. Your picture is lovely, but that it not what off road surfaces and tyres look like...

I'm also quite sure it has been made clear that I have and Ben has personally seen stock trucks break stock axles when driven on easy trails only. You are one of the most closed minded people I've seen on the net. I can't imagine how you can function as an engineer.

[KiwiBacon]

There are other ways to develop normal forces. I've explained them at least twice in this thread. Read back yourself as repeating myself three times is ridiculous. Your picture is lovely, but that it not what off road surfaces and tyres look like...

Normal forces don't develop any torque. You need to draw a picture to describe what you're talking about because it's clearly not "normal force".

I'm also quite sure it has been made clear that I have and Ben has personally seen stock trucks break stock axles when driven on easy trails only. You are one of the most closed minded people I've seen on the net. I can't imagine how you can function as an engineer.

Your arguments fail so you've gone straight into personal attacks, well done.

For the record I'm not closed minded at all, I just can't understand what you're on about. But I have owned this 10/24 spline vehicle for over 10 years and have done plenty of easy trails without breaking anything. OMG, how is that possible?