McNamara vs RoverTracks

[SOA 93]

Well....I will give them a phone call for sure. Prices seem very acceptable and not having to worry with heavy shipping and import taxes is a big thing for me. Also makes spares a lot easir to have.

Thanks Andy, it helped a lot, will call them tomorrow.

Cheers

OK the latest from Rakeway is that I have just sent the cheque off to them for the last RD35 ARB (Dana 60HD full float 4.56 and up 35 spline) that GKN UK has, I will take a 101 axle up to them and then they are going to have a look at the best solution for myself, ie shafts or side gears. Then if its not going to work they can send the ARB back. Did me a good price on the ARB .

If everything is ok they will order another from ARB (Aus), but could take a couple of months, giving my wallet chance to recover.

D-90 I mentioned you, and informed Neil you are likely to call about a similar project.

Guys.....really really really good tech on the shafts!

Andy

[dollythelw]

you're sooooooooooo wrong starboy

milk choc is the superior material

more elastic and less prone to shock loads - slight concern over melting temperature although those concerns are easily circumvented by using ice cream as a primary lubricant, SHOULD you ever manage to break the new flakier crumblier scrapiron halfshaft you can simply relax in the bath and eat whats left (lizard to run over the phone is an optional extra I understand)

now shape up and finish that hardwood chassis you've been whittling at for sooooooooo long

[Astro_Al]

lizard to run over the phone is an optional extra I understand

Yeah, but a scorpion rifling through your wallet isn't...

>"now shape up and finish that hardwood chassis you've been whittling at for sooooooooo long"

Yes Sir, sorry Sir.

Al.

[dollythelw]

[Ex Member]

1541 is a plain carbon steel, not an alloy steel.

1541 is a Carbon-Manganese steel, not technically "plain carbon steel"

15xx mean it is a 1.5% Mn steel

xx41 mean is have 0.4% carbon

[rakeway]

Well....comunication isn´t that good, have tried to contact them but never got an answer. Would prefer to have an European supplyer, but have to go overseas because can´t get anyone to make them!

rakeway are open for 8am till 6.30pm monday to friday and 8am till 1pm saturday

is that long enough for you give us a try. rakeway

[freeagent]

i'm siding with those who reckon gun-drilling half shafts for 4x4 use is a pointless excercise... it WILL produce a weaker shaft, due to removing some material, even though that material is basically running along the neutral axis...

i also think that boring the middle out will compromise any heat treatment as it will not allow for the outside of the shaft to be hard, with a soft, flexible bit running down the middle to absorb all those nasty 36" Simex sized shock loads... you will efectivly have a case hardened centre aswell....

i think the best result will involve material choice (all that £1500 stuff is total overkill) machining quality and design, then the correct heat treatment.

I did a failure analysis study at uni looking at a lorry halfshaft that had failed due to the case hardening being too deep, it had snapped during a fully laden hill start as it was unable to flex enough when the power was applied....

if you spend a grand on steel, then give it to monkeys to machine and heat treat, you might aswell make them from bamboo....

[nas90]

As I understand it, rifle boring is a weight ONLY consideration - like drilling brake discs.

Can someone PLEASE show me an equation which has ANYTHING to do with surface area?

This keeps coming up.

I agree absolutely that strength losses are minimal when removing the centre - that's not an issue for me. It's the idea that it's somehow stronger because it has more surface area (cos you've added that of the inner bore to that of the outer surface) that I just don't believe.

I could be wrong, but I've never come across it.

Proof?

I also accept that it gives more surface area for the treatment to work on - if this is the point then we agree, but it is still the case that removing the central material decreases the strength, whether or not it is minimal.

Of course rifle boring AFTER treatment does not give extra surface area for the treatment to affect, since it's already too late...

Presumably polishing the centre bore is to ensure no surface imperfections which could act as stress raisers or help cracks develop / propagate.

Al.

Approximately the centre 1/3rd of a solid shaft has very little effect on the torsional strength of the shaft and the amount of torque it can transmit.

For example: A solid shaft is Ø50mm, max allowable shear stress 84MN/m^2, max torque T = 2.06kN-m

When hole Ø25mm is bored through centre max torque T = 1.94kN-m

Percentage reduction in strength = 5.83% percentage reduction in mass = 25%

This is the reason why reciprocating engines on propellor driven aircraft have hollow crankshafts, you are reducing the aircraft engine mass for very little change in strength / torque. Prop shafts on vehicles are another example and the outer diameter being that much larger makes a bigger difference to the bore diameter. Unfortunately with a half shaft the outer diameter is not large since you have bearing / CV / brake constraints. By deep hole drilling the half shaft and then honing you will not reduce the strength (appreciably) but you will remove any cracks induced in the manufacture of the halfshaft, especially in the case of a material which is tough and strong and has probably been forged. The quality of the machining and splines will probably have more effect than a stronger steel with inferior quality machining.

[freeagent]

that is a good point, about removing cracks...

...but an aircraft crankshaft is a slightly different application, as it is not realy subjected to shock loads (such as a spinning tyre suddenly finding terra firma again, or 250bhp being unleashed instantly when some lout sidesteps the clutch at 4,000 rpm)

reducing material from an aircraft engine crankshaft will lessen the rotating mass, and allow the engine to accelerate faster, and may be slightly more efficient as it is moving less metal...

i don't know much about planes but i cant see how any of the power train could be subjected to shock loading, or high torsion/ torque loads... so drilling and lightening will have little negative effect...

i still reckon the shaft will be stronger and more robust if it isn't drilled.... i also thought that putting holes in things often reduced the components fatigue life...

i guess the bottom line is this... there must be a reason why nobody, either component manufacturers, race and competition teams, or anyone else, to my knowledge, makes gun-drilled halfshafts for utility or off-road vehicles....

[nas90]

that is a good point, about removing cracks...

...but an aircraft crankshaft is a slightly different application, as it is not realy subjected to shock loads (such as a spinning tyre suddenly finding terra firma again, or 250bhp being unleashed instantly when some lout sidesteps the clutch at 4,000 rpm)

reducing material from an aircraft engine crankshaft will lessen the rotating mass, and allow the engine to accelerate faster, and may be slightly more efficient as it is moving less metal...

i don't know much about planes but i cant see how any of the power train could be subjected to shock loading, or high torsion/ torque loads... so drilling and lightening will have little negative effect...

i still reckon the shaft will be stronger and more robust if it isn't drilled.... i also thought that putting holes in things often reduced the components fatigue life...

i guess the bottom line is this... there must be a reason why nobody, either component manufacturers, race and competition teams, or anyone else, to my knowledge, makes gun-drilled halfshafts for utility or off-road vehicles....

Deep hole drilling and honing is not cheap so for small batch production, it is too expensive even for Land Rover's production and in the case of 99% of vehicles built is totally wasted for the trip to Tesco's! the difference in weight reduction for a Ø28mm half shaft is not a lot!

Aircraft crankshafts are subject to shock loads. If a propellor hits the ground the aircraft is grounded, crankshaft removed and crack tested / checked for accuracy. Engines can be damaged by rapid changes in throttle position, this is more usually a heat transfer problem on glider tugs where the pilot shuts the throttle and gets down as quickly as possible for the next glider, which is why variable pitch props help because you keep a constant engine speed but vary the propeller pitch, downside is the god damned awful noise! Anyone ever heard a Harvard go past?

[bathtub]

Couldnt bother to read full post but r u building 101 Salisburys ?????? if so why not just use 101 lockers & shafts you can get ARBS or Detroits.

Ive run 38.5" Boggers 300+ HP & never even scratched a shaft { got full spare new set for £200} .

I run 42 " tyres know & havnt Broken anything !

Why fit D60 shafts or if you want what i plan is to just get 22 spline better shafts if needed!

[bill van snorkle]

I am going out on a crash and burn offroad trip today and this discussion on the finer points of axle shaft technology has reminded me that my left front inner shaft is still one I knocked up 5 years ago by cutting a salisbury rear shaft in half, doing the same to a Toyota front shaft. pressing both shafts into a 6'' length of hollow bar and pool welding the shafts to the bar through holes in the side. This was only meant to be a temporary measure while I waited for McNamara's to make me a new shaft, and I have been carrying the new one around for 4 1/2 years to replace the welded one when it eventually lets go. That is the beauty of portals I guess.

Bill.

[B reg 90]

Having to much time on my hands this evening I thought I'd work out a real life example of the loading on a 10 spline land rover front 1/2 shaft.

However as I haven’t looked at most of this stuff in the last 11 years, feel free to point out any mistakes that may have creeped in.

So let’s assume you have a land rover with a 200 TDI engine. This will give you a maximum/peak torque of 250 Lb.ft at the engine (this is a tweaked engine - data from J. Ferns website as I couldn't find the standard engine data).

Assuming you are in 1st gear and low box and standard diff ratio with both the center diff and your ARB's locked, then the maximum torque a 1/2 shaft can see will be multiplied by the overall gear ratio, i.e. by 42.

Therefore the maximum torque that the 1/2 shafts can see's is 250Lb.ft x 42 = 10531 Lb.ft or 14279 N.m if you like metric.

However to develop that level torque in the 1/2 shafts the tyres would have to have sufficient traction to resist turning by the same amount. Pragmatically that is difficult to achieve as if you were on a mud surface the wheel(s) would just spin. So let assume that you are climbing a hill all 4 wheels spinning. Then one front wheel drops into a rocky bit and stops it turning. The other 3 wheels are no longer free to spin because of the diff locks, so all the torque is applied to the front wheel/ ½ shaft as the locked diffs prevent the other wheels from spinning. That means the one half shaft sees all of the above torque.

According to my engineering text book the stress in a shaft under a torsional force, i.e. being twisted is:

T/J=Stress/R

Where:

T = torque applied to the shaft (N.m)

J = Polar second moment of area (m4) = PI*(D4-d4)/32

D = shaft outer diameter (m)

d = Shaft inner diameter (m), i.e. a hollow shaft.

Stress = N/m2

R = Radius of the section of shaft you want to know the stress at. As the stress is at it's maximum at the outer radius this is usually used as the outer radius of the shaft (m)

As we are going to compare a solid shaft against a hollow one under the same torque loading we need to rearrange the above to allow us to calculate the stress levels:

Stress = (T x R)/J

A standard chocolate LR front 1/2 shaft has a outer diameter of ~ 27mm

So the polar second moment of inertia is 4.486x10-8 m4

Hence the stress is = (14279 N.m x 0.027 m)/4.486x10-8

=4297 N/mm2 (MPa)

If the standard 1/2 shaft had a 3/8" (9mm) hole down it then repeating the above calculation would give a different value of J (second Polar moment of Inertia) as now the shaft has a inner diameter (d).

J now equals 4.219x10-8

As every thing else is the same the new stress level is:

= (14279 N.m x 0.027 m)/4.219x10-8

=4359 N/mm2 (MPa)

I.E. A 1/2 SHAFT THAT IS DRILLED ALLONG IT'S CENTER WILL SEE HIGHER STRESS LEVELS, 4359N.mm2 against 4297N.mm2 in the un-drilled shaft. Fair enough the difference isn’t much, but as it’s expensive to drill the hole in the first place why do it just to make the shaft weaker?

I believe that it is done in high performance cars as it reduces the weight of the drive train. This allows the engine to accelerate the car faster as there is less rotational inertia in the drive system. This is the same effect as skimming the flywheel.

Now I don't know the material land rover make their 1/2 shafts from (it's guff what ever it is). So lets assume that you have a front 1/2 shaft that has the same dimensions as land rovers 10 spline one. However assume the material is ASTM 4340 steel (Quenched and annealed) with a yield stress (the point where it starts to deform plastically, i.e. doesn't spring back to it's original shape) of 1590 N.mm2 and an ultimate stress level (the point where it breaks/twists off) of 1720 N.mm2 .

As ideally we do not want to permanently twist/yield the shaft, the maximum stress we would like the shaft can see is therefore obviously 1950 N.mm2. So in the above example the engine can supply 2.74 times the torque needed to start permanently bending the shaft. In fact as the applied stress is 2.53 times the ultimate stress level the shaft will just break...........

To make matters worse land rover decided to make the 1/2 shaft with the inner spline at the diff end with a spline root diameter smaller than the shaft it's self. This means that if you redo the stress calculation for the splined area the stress will be higher. In addition the small radius's at the bottom of the square spline will concentrate the stress levels by ~ 2 or more times. Hence why 10 spline LR ½ shafts always break at the diff.

Hence a good ½ shaft should have the main shaft diameter smaller than the spline diameter at either end so that the highest stress level is in the main shaft, not the splined area. Also the splines should be such that the radius at the bottom of the spline is a big as practical. This reduces the stress concentration in the spline area.

However if you up-rate to a bigger diameter ½ shaft it can obviously carry more torque.

Say your ½ shaft has a diameter of 32mm (think that this is the diameter that KAM use). Using the same material this would give:

J = 1.027x10-7

Stress= (14279 N.m x 0.032 m)/1.027x10-7

=2219 N/mm2 (MPa)

So using the same ASTM 4340 material the new ½ shaft can now very nearly with stand the torque applied by the engine. In fact we only need to go up to a shaft diameter of 36mm to get to the point that the shaft can withstand the torque applied by the engine with out the stress being high enough to permanently bend the shaft.

Pragmatically though the above force would be a transient force, so if you make the main diameter of the shaft the same diameter for as long as possible you can get a reasonable amount of twist in it before it takes a permanent twist and/or breaks. Hopefully by this point the peak torque loading has past and the ½ shaft has effectively acted as a shock absorber.

Other Factors:

Fatigue:

A material may be stronger enough to take a load one or more times, but over repeated application of a repetitive force it weakens (fatigues) until it eventually breaks at a stress level lower then it would have when ‘new’. This is equivalent to bending your shatterproof ruler once or 100 times. The first time it’s ok, but by the 100th deflection it goes all opaque and then fails. Each bending operation is a fatigue cycle.

As steel tends to need 1000’s of cycles to fatigue it, use of your right foot will not be sufficient to fatigue it just be accelerating and decelerating. However if your axle is bent then every rotation of the wheel will be the equivalent of a bending cycle for the ½ shaft. If you have 33” diameter tyres then 1000 miles equates to ~ 1.939 million bending cycles(or ½ shaft revolutions), 10,000 mile gives 19.39 million bending cycles. So your ½ shaft material is now nicely fatigued and when you get off road and put it in low first, the ½ shaft breaks really easily as the material can no longer take the stresses induced by the higher torque in the lower gearing.

How many off us check if the axle casing is bent if we seem to be going through a few ½ shafts???? The bigger the bend in the casing the bigger factor this would be. That said I don’t know how far the casing would need to bend to take up the clearance in the splines.

Surface Finish:

Poor machining leaves a surface finish like a mountain range when looked at under a microscope. The valley’s have sharp points that act as stress raisers. These can promote failure at a stress level lower than we would anticipate. So the better the finish on the shaft the lower this effect will have.

[Ex Member]

Yes, don't do the math, because it means the axles should be 1.5" minimum to take a locked wheel with full engine torque. Imagine how big it needs to be "theoretically" with a real engine and serious gearing.

Be careful in first low and locked......

On your fatique discussion, remember most loading is at very low stress. Also there is not a stress cycle with each wheel revolution so the cycle level is actually very low. The fatique discussion in this application is really a discussion over low cycle fatique.

[Andy]

wow big sums, i believe you even if i dont understand it.

if you really want to know, the figure LR state for a 200Tdi in a disco (dunno if defender is different) is 195 lb/ft for a standard engine.

[SOA 93]

Couldnt bother to read full post but r u building 101 Salisburys ?????? if so why not just use 101 lockers & shafts you can get ARBS or Detroits.

Ive run 38.5" Boggers 300+ HP & never even scratched a shaft { got full spare new set for £200} .

I run 42 " tyres know & havnt Broken anything !

Why fit D60 shafts or if you want what i plan is to just get 22 spline better shafts if needed!

Hi Bathtub,

Yes, I'm well aware of what tyres you have run and are now running and I know you have you have been in contact with Bill at GBR after another ARB to replace your Detroit, he hasn't let me know when he expects the side gears to arrive yet, and if I could get new gears made in the UK then I think that would be a better solution, and if I start with a Dana60 ARB then it is easier to upgrade if I ever need to.

I can get drive hafts off an e-bay shop not quite as cheap as yours but nearly.

I want to keep the stock shafts if I can, to keep costs down, I don't really want a detroit in a day to day vehicle and the quote I received from Mcnamara was way to high.

Has Bill from GBR given you a idea of when he expects the gears.

Your plan to get new shafts if needed is exactly the same as I'm hoping.

Getting Rakeway to do the gears (hopefully!) might benefit you too.

Andy

[Andy]

i dont see why people are so against detroits in daily drivers, ive got one in my daily drive & after a month i got used to the difference in handling & it doesnt bother me at all. only goes clunk/bang about once a week & i do 32miles a day work & back.

[Fatboy]

I'm same as Andy... i've got Detroits in both axles (Truetrack in front) and am using the wagon fdaily at the moment, at least 300 miles a week and don't even notice they are there. Windy twisting roads, varying surfaces etc.

[bathtub]

Hi,

Its Phil at GBR isnt it ?????

Hes said on friday arb have done them know but it would probably take about 1 month to get them here.

Want to buy a detroit????? im just getting rid of it as its making steering harder around the forest sections

Just ordered a 180amp alternator from him though

[SOA 93]

Hi,

Its Phil at GBR isnt it ?????

Hes said on friday arb have done them know but it would probably take about 1 month to get them here.

Want to buy a detroit????? im just getting rid of it as its making steering harder around the forest sections

Just ordered a 180amp alternator from him though

Bathtub,

Its Bill Davis, he probably thinks you've got a lisp.

I may be interested in your Detroit, never raced or rallied eh! PM me what you want for it.

You need a 180 amp alternator with that Double oven you've got on your front bumper.

Thanks for the info.

Andy

[Lara]

I'm siding with those who reckon gun-drilling half shafts for 4x4 use is a pointless exercise... it WILL produce a weaker shaft, due to removing some material, even though that material is basically running along the neutral axis...

i also think that boring the middle out will compromise any heat treatment as it will not allow for the outside of the shaft to be hard, with a soft, flexible bit running down the middle to absorb all those nasty 36" Simex sized shock loads... you will effectively have a case hardened centre as well....

i think the best result will involve material choice (all that £1500 stuff is total overkill) machining quality and design, then the correct heat treatment.

I did a failure analysis study at uni looking at a lorry half-shaft that had failed due to the case hardening being too deep, it had snapped during a fully laden hill start as it was unable to flex enough when the power was applied....

if you spend a grand on steel, then give it to monkeys to machine and heat treat, you might as well make them from bamboo....

Hi Freeagent,

Don't degrade your own post by saying silly things!

Although you are quite right that poor machining will render good material useless we have to compare like with like if we are to get anywhere with material comparisons,

And do you really think that I would let a monkey even sniff my half-shafts let alone machine them when the material cost that much? My shafts were machined by one of Williams Race Engineering's sub contractors with a very high reputation and heat treated by the same company to the same spec as the drive shafts made in the same material as Williams F1 shafts, Good enough for me and it has knocked my shaft snapping days on their head!!! I have a desk full of shafts at work including Maxidrive that all lasted me less than one day, Think I got the material spec and machinist absolutely right and saved myself a lot of money and time in the process.

Material quality, heat treatment and design, all add up to quality. not any without the other you are right.

And not silly comments.

Lara.

[freeagent]

My comment was not a dig at you, more as a point to those who seam to think material spec is the be all and end all... i totally agree that if you had just spent £1500 on a steel bar you would want the finest engineers you could find to machine it.

you seam to have found the zenith as far as half-shafts go, it doesn't get much better than that unless you've got whoever bankrolls the Ferrari F1 team paying your credit card bills!

it wasn't a silly comment, just trying to illustrate a point. as someone else said, even surface finish can affect the strength of the shaft, and its fatigue life.

just out of interest... where do you go from here if you wanted to improve on what you've got?

or have you gone as far as you can considering the non-variables (ie shaft diameter)

[bill van snorkle]

Hi Freeagent,

Don't degrade your own post by saying silly things!

Although you are quite right that poor machining will render good material useless we have to compare like with like if we are to get anywhere with material comparisons,

And do you really think that I would let a monkey even sniff my half-shafts let alone machine them when the material cost that much? My shafts were machined by one of Williams Race Engineering's sub contractors with a very high reputation and heat treated by the same company to the same spec as the drive shafts made in the same material as Williams F1 shafts, Good enough for me and it has knocked my shaft snapping days on their head!!! I have a desk full of shafts at work including Maxidrive that all lasted me less than one day, Think I got the material spec and machinist absolutely right and saved myself a lot of money and time in the process.

Material quality, heat treatment and design, all add up to quality. not any without the other you are right.

And not silly comments.

Lara.

If your vehicle requires Formula 1 type materials and technology to survive more than one day, may I suggest that the safety margins are quite small, particularly with regard to differentials, cv joints etc, and that stronger diff/axle assemblies from another brand of vehicle might have been a more cost effective solution ?

Bill.

[freeagent]

that is a good point, aren't a lot of F1 components designed with similar safety margins to fighter aircraft..? as little as 0.1 in some cases?

[Lara]

Hi Guys,

Freeagent, Sorry I was a bit touchy no offence taken or meant, your points were quite valid.

No clue where to go next for a rover type axle and shaft, Cry in a corner perhaps as you say non-variables are the problem if I need to improve now.

Bill,

I had no problems with my diffs as I run Quaife units,

I run 3.5:1 CW&Ps for strength and use a specially built Auto Box with special torque converter so can get away with the ratio.

I also have a Maxidrive 40% under drive transfer box and lockup TC so descents are no problem either.

CV's are now Ashcroft and before that they were KAM units, I never had problems with any of this kit but half-shafts! I honestly broke one every time I went off roading and most within 15 minutes of starting. I must have broken 15 or more and just got fed up with listening to peoples claims to be made of unbreakable "fairy dust" as Dolly would put it.

I have to keep the axles looking standard for Belgian road test laws so have no option but to use Rover axle cases at least. And it was an interesting challenge, if a little pricey.

Lara.