Outer Limits 4x4 Board

Thought some other people might be interested in some info I gathered on the comparative strenght of the steels used in aftermarket Land Rover (and other) axle products.


Material (other names) / Application / Ultimate Tensile Strength (MPa / psi)

EN25 (X9931) / McNamara axles? / 1300 / 190 000

EN26 / X9940 / 1380 / 200 000

AMS-6418 (MIL S - 7108 / 4625M4 / HY-TUFF) / Maxi-Drive axles / 1655 / 240 000

4140 / 1230 / 186 000

4340 / New longfield / 1380 / 200 000

300m (4340m) / New longfield star/ 1980 / 288 000

SAE1045H / Many std axles / 930 / 135 000
SAE1541H (SMn438H/SMn443H) / Many US aftermarket and truck axles / 1200 / 175 000


Data mainly from Timken Steels and Smorgon Steel - both are suppliers of these steels. Interestingly, Maxi-Drive quote a lower strength of 1550MPa for their axles, but strange engineering (another axle manufacturer), quotes 240 000psi (as does Timken).

Interestingly, most standard axles (and US aftermarket axles), seem to be made from 1045H or 1541H - which is supplied already induction (case) hardened but still soft enough to have the splines machined into it. This saves a lot of money for the axle manufacturers and is probably the reason most manufacturers in the US do not waist their axles down to the root diameter of the splines along the length. I am not 100% sure about the values for 1541H - if anyone has a more accurate one please post it.

I am not 100% sure that McNamara use EN25 and not EN26, but since EN25 is what Maxi-Drive used before they switched to AMS-6418 it is probably right. Although the maximum values are the same, most steel suppliers state that EN26 should be used where higher strength than 4340 is required.

Shear is usually 75% of tensile strength for all these steels.

From the looks of the numbers, AMS-6418 is a pretty impressive steel, a fair bit stronger than 4340 and almost as strong as 300m/4340m. Of course a lot depends on how the axle is designed, how well it is machined and heat treated, but I think this is a usefull comparison of like for like.

Does anyone know for sure what McNamara use?

Ben,
I added this to FAQ.

Michael.

Does anybody know the specs on the factory axles? I assume they are low carbon steel.

Cheers Michael.

Running a few quick calcs last night - it looks like McNamara 30 spline 1.31" axles (if made from EN25) are actually the same strength (or even a bit weaker) than Maxi-Drive 24 spline 1.24" axles (Using the quoted MPa values from MD for HY-TUFF). If someone can measure the root diameter of the toy axle I can do a more accurate calc.

Most cheap US aftermarket axles are made from 1410 I think, or 15xx. I will post the specs for this when I have a moment - it is weaker than all the steels posted above. I think factory axles are probably about the level of these steels.

Excellent work Ben.

I believe that Jac Mac uses EN25.

Another interesting point that when I was talking to Jack from CTM (US company - they make the CTM joints and 300m axles) he said when making axles sometimes they use Hytuff when they carnt get the 300m and he said the strength was almost the same which is what you are saying here.

Sam

So the difference in what makes the JM axles stronger than the MD ones (as previously stated on this and other sites) is the manufacturing process?

According to this the material that JacMac uses is weaker. But..... do these figures take into account the heat treating process that JacMac use, and MaxiDrive also if appropriate?

I think after discussions previously we worked out that the axle designs were pretty much the same between the two with regards to stress points etc.

DiscoDino wrote:So the difference in what makes the JM axles stronger than the MD ones (as previously stated on this and other sites) is the manufacturing process?

What makes you think this?? I'm quite sure that the Hytuf axles of the same size are stronger from an impact and fatigue loading point than the EN25.

According to some quick (and very basic) axle strength calcs I did...

Assuming all other things are equal, the ultimate tensile strengths of other after market axles compared to the MD 24 spline (1.24") HY-TUFF axles are:

JM 30 spline axle - 97% of MD
JM 35 spline axle - 130% of MD
New Longfield 4340 CV Stub - 102% of MD
As above if made in 24 spline - 91% of MD

This was using the HY-TUFF UTS quoted by MD or 1550MPa. However the root diameter of the toy axle was assumed (31mm) because I can't measure it now.

So an MD 30 spline would be about the same strength as a MD 24 spline, and about the same strength as the stub of the new longfield.

I have edited my first post to add the strengths of the most common 2 steels used in factory (and US aftermarket) axles.

Interesting figure from Timken Steels below...

DiscoDino wrote:So the difference in what makes the JM axles stronger than the MD ones (as previously stated on this and other sites) is the manufacturing process?

I think the material that Maxi uses is better but his axles are smaller so like Ben has shown the strenghts are fairly similar.

In either case I believe that the axles are stronger than the diff centre that drives them (whether the diff is a rover one or a toy one)

I think that what has been stated about the comparitive strength between the Jac Mac and Maxi setups is that the Jac Mac 30 spliners with the Toy centre is stronger than a Maxi setup with the Rover 8.5in centre simply because the crown and pinion is stronger.

Sam

Slightly off topic but I got a call from Mal Story the other day to follow up an email in regard to C.V's. (M.D. customer service)
He is in the process of building up C.V.'s from the same material as his axles (hytuff) with minimum case hardening, that he said would be near indestructable when they get it right.
With the fuse being the outer stub axle if you want.
Regards
Michael.

Is that the one he has been working on with GBR in the states for the Disco2's?

Yes Slunnie.
Mal said that unfortunatly the manafacturers made a descion based on cost and made some of the parts out of 4340 instead of making the whole lot out of the best material available. There made some prototypes that are out getting used .The full hytuff ones are still in development but I think Mal said prototypes would be up in about six months, at this stage they will be the defender type.
Regards
Michael.