Thread: JacMac vs Maxi

Originally posted by jase
mine was air but have heard the do (did) a vacuum also?
Jase

the air operated version was the most popular

Mick

I thought they now only did compressed air.

<div class='quotetop'>QUOTE</div><div class='quotemain'>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 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?[/b][/quote]

http://www.outerlimits4x4.com/PHP_Modules/...+mac%2A+maxi%2A

<div class='quotetop'>QUOTE</div><div class='quotemain'>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...
[/b][/quote]



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.

Originally posted by skip
I have no experience with a Jac Mac rear locker but I have had a Maxi in the rear of my 300tdi Defender for a long time. Mine was fitted by Graeme Cooper, yes it does require the diff centre to be sent to Maxi HQ in qld to be machined.

My local LR specialist does the conversion in-house - I'm pretty sure they don't send it to Qld. - but I will check.

Ron