Progress pics of the new 'Force 9' differential

[landroversforever]

Is the coast side one side of the teeth on the crown wheel?

[ashtrans]

Hi all,

some photos for you :

new type cast iron housings with fatter ribs

Rear view showing bolts to limit end cap deflection

stock 9" housing and our rover 9" housing

stock 9" housing and early 9" ali housing with small ribs

Bill/Will,

we are using the stock 9" bearing spacing, a longer pinion would of course be stronger but this would then present other fitting and manufacturer problems, whilst the loads are very high when driving on the coast side I think our failure was due to both a poor casting and the fact that our casting is way smaller than the stock 9" and was/is less rigid.

landroversforever,

one side of the tooth is called the 'drive' side, the other the 'coast' side,

on a stock 90 the rear drives on the drive side and the front drives on the coast side,

on our force 9 diffs the front drives on the drive side and the rear on the coast side but due to the different tooth pressure angles the rear generates a lot of side forces, it's these that cracked the ali casing.

[landroversforever]

Ahh I get it now So is the coast side the more sloped one? therefore with power wants to push the pinion away?

[will_warne]

Ahh I get it now So is the coast side the more sloped one? therefore with power wants to push the pinion away?

Spot on!

[bill van snorkle]

Dave / Ian,

I would guess the reason most of the rock crawlers use a nod iron case is because hi 9's are expensive enough as it is and it isn't worth the extra cost of the ali housings (which they will do for special order) to save a few kgs. Plus, if you break a casing then the iron housings come off the shelf....

Will, the standard ''off the shelf'' housings are made from brittle grey iron. Nodular iron housings are expensive performance options and quite hard to find. Interestingly for a diff that gained a reputation for strength and durability,std 9'' Ford housings are one of very few that are made from poor quality grey iron.Most, including Rover use Nodular Iron .

Bill.

[will_warne]

Will, the standard ''off the shelf'' housings are made from brittle grey iron. Nodular iron housings are expensive performance options and quite hard to find. Interestingly for a diff that gained a reputation for strength and durability,std 9'' Ford housings are one of very few that are made from poor quality grey iron.Most, including Rover use Nodular Iron .

Bill.

Bill, sorry, I should have said I was referring to Hi 9s in my post.... But, yes, the stock Ford 9 isn't up to much! There are a few people who supply aftermarket nod iron houses and they are quite expensive - an Ali housing is only slightly more expensive.

[bill van snorkle]

Missus had a headache this morn so I started thinking bout swivels and stuff. Dave/Ian,or anyone,from earlier post, the measured inner halfshaft runout was .008'' TIR. Was that on full lock? And I'm not certain it is the same thing, but did you measure inner halfshaft deflection from centre when going from straight ahead to full lock ? The reason I ask is that the front halfshafts on my old BJ40 are bushed at the stub axle (spindle) only, the same as I have done on my LandRover. RRC's ,Defenders etc from memory are bushed at both swivel ball and stub axle, but I can't remember if there was sufficient clearance at the bushing to cope with deflection.If there is conflicting geometry due to king pin axis being not perpendicular to axle tube,would this deflection add additional stress on the cv joints?

Bill.

[Mr Ian]

Hi Bill I know you know most of the following but for the benefit of those with less experience. The lateral movement of the half shaft is due to the CV being either too far in or out. On a stock 90 there are shims behind the CV circlip these position the CV center of rotation on a line through the King Pin. On early RR the CV is not fixed, ie has a floating stub shaft but the inner half shaft is located by a bronze bush, this is for lateral location only and does not support the half shaft. Our test was carried out at near 45deg but in practice because of tyre/radius arm rub the steering is restricted to much less than this. Even with the small amount of run out we still had leaks with stock seals so have now replaced them with specials, no more leaks. It did explain something that has long fooled us, why does the stock swivel constantly leak 'one shot' into the axle?, could it be some people do not fit the spacers behind the circlip. With regard to materials choice for the diff housing. The UK spec is SG Iron (spheroidal graphite) in the US it is known as 'Nodular iron' same stuff. In our case we use 500/7 (500N/mm wit 7% elongation, Alu LM25 is approx 240n/mm with 0% elongation similar to grey CI) As David noted earlier it is possible we over reacted to the initial breakage, only time will tell. Jim (Gigglepin) Marsden has completed two events now with the new diff with no problems but we need more severe testing before any release. Will try to keep you updated on the trials and tribulations. Regards Ian Ashcroft

[bill van snorkle]

Thanks for clarifying few things Ian. it surprised me to recall that it has been over 3 years since I worked on any landrover other than my own, and was incorrect when I stated that defender etc front inner shafts were bushed.And I forgot that the bushing on RRC's was there just to keep the CV laterally centred and not support the shaft.

bill.

[bill van snorkle]

Briefly resurrecting this old thread so that further developments on the Force9 diff can be included, and possibly inspire a little more discussion on differential design.

As far as I am aware the major improvement has been an alteration to the tooth profile of the ring and pinion so that the pressure angle on both drive and overun sides of the teeth are equal, thus greatly reducing side thrust loads.

I'm a bit interested in the 2 diff failures that Jim Marsdens 90 suffered during his KOH adventure to the USA. The first failure was attributed to the carrier bearing journal snapping off the ARB locker. But I am unable to find any particular reason given for the second failure.

In some ways I have always likened the very deep hypoid offset of the 9'' Fords to that of a worm drive, where drive and overun forces place enormous end thrust pressure on the pinion bearings, and radial pressure on the carrier bearings.Overun forces want to suck the pinion into the carrier or vice versa, and drive forces want to push the pinion away from the carrier or vise versa. I wonder if these forces contributed to the ARB failure and the second failure as well? And I wonder if it would have been better to choose a diff with a less severe hypoid offset to build into the Landrover housing?

What really prompted this post is that I was reading the other day about Wynns Heavy Haulage's experience with the worm drive differentials on their ex WW2 Diamond T tank transporters. When pulling very heavy loads, the end thrust on the worm shafts was sufficient to snap the bearing retainer cap studs and the the shafts would screw their way out of the diff housings.Drive loads would push the wormshaft out the back, and engine braking loads would push it out the front. The mechanics solved that problem by welding the retainers in place.

[JST]

I'm a bit interested in the 2 diff failures that Jim Marsdens 90 suffered during his KOH adventure to the USA. The first failure was attributed to the carrier bearing journal snapping off the ARB locker. But I am unable to find any particular reason given for the second failure.

lack of oil for bearing failure maybe?

[ashtrans]

Hi Bill,

Jim was running our original prototype F9 axles which were built approx 3 years ago and were built using the True High 9 4.11 gears and a modified ARB RD99,

when running the 4.11 gears we found that the needle support bearing on the end of the pinion was failing abnormally quickly, I think 2 or 3 were fitted in the rear over a 2.5-3 year period, I attribute this to the high side loads from the tooth angles on these Hi9 gears,

just before the KOH event, Jim wanted the ratios swapped to 4.86, again from Hi9 in the US, the diffs came in and again the needle roller bearing was a mess and the bore in the casing that it sits in was also a little damaged, the new gears were built up with new bearings etc.

The first failure of the ARB journal bearing I would put down to high loading due to both the tooth angles, ie driving on the coast side of the gears but also one of the mods we had to do to the ARB was to pull one of the journal bearings in 20mm which would increase loading,

The second failure was a classic tooth off which I would strongly suspect was because the gears came out of mesh due to the needle roller bearing collapsing, again related to the Hi9 tooth profile.

Whilst I doubt we will be making more F9 axles the whole experience was a big learning curve, and it has allowed us to use some of this knowledge on other products such as the new replacement diff we have designed for the 110 post salisbury rear, for this we have designed a hypoid ring and pinion with 1.5" low pinion offset, new bolt in housing, longer pinion to pull the pinion bearings apart and it uses a stock Rover (not P38) diff centre, air locker, ATB etc and you can use the stock shafts or our HD ones, I am not sure we would have done this without the knowledge we accumilated when doing the F9's.

Dave

[Daan]

Hi Dave, thanks for the honest reply. I had noticed you are no longer producing them, is this a result of the financial climate?

Daan

[JST]

i think its more of result of the original batch taking a while to shift and the fact its a mammoth undertaking on top of everything else they do.

[Team Idris]

In a way it looks like the same problem as plant and agri, in that the torque loads in the diff get so high, the only way to reduce them is by reduction hubs. But that shoves the cost right up So I cant see them popping into the small 4x4 scene any time soon. Which is a shame, because I've seen epicyclic hubs really take a pasting on site

I loved the idea of the bolt on killer landy axel though. Great idea

[bill van snorkle]

Thankyou for the reply Dave. Will the new P38 hypoid replacement diff be based on off the shelf ring and pinions?

Idris,I think there is a firm in the USA that do bolt on epicyclic reduction hubs for domestic axles. Years ago i narrowed down and lightened some Leyland truck epicyclic hubs for a Forest Rover replica I intended to build. I was making them so that the Sun gear on the halfshaft could be moved into mesh with the planet gears for a 4:1 reduction for running 11.00x28 tractor tyres, or alternately the sun gear could be slid out of mesh with the planet gears and lock into the hub end plate for direct 1:1 drive for when running normal 9.00x16 tyres. After a lot of machining work they were stolen by a scrap metal thief.

[rick]

Bill, Dave updated one of the threads on AULRO with pics+ details of the new P38 replacement CWP's, I'll dig up a link.

[edit] here http://www.aulro.com/afvb/90-110-130-defender-county/144708-life-puma-rear-diffs-9.html

[bill van snorkle]

Thanks Rick..

[ashtrans]

Hi Daan,

yes James is right, it's a combination of them being quite expensive and not a fast seller but also 2 other factors, although they were quite a lot of money, they were not particularly profitable considering the amount of time that went into them and also I would struggle to find the huge amount of time that would be required to produce another batch. If we did do another batch I would make quite a few changes which would make them cheaper but it's still a lot of time and money to gamble. Bit of a shame really but I can't do everything !

Bill, we looked at existing ring and pinions but there are many factors to consider when designing a comercial product and using an existing R & P would mean other compromises, ie wouldn't fit a stock locker, special drive flange, and pinion bearings etc, and the only reason to use an existing would be to buy off the shelf different ratios but in reality 98% of the target market will want stock ratios and we deemed it not worth the additional work/cost/compromise for the other 2%

Dave

Dave

[o_teunico]

plant and agri, in that the torque loads in the diff get so high, the only way to reduce them is by reduction hubs

Maybe that´s the way to follow. With reduction hubs the diff itself will need less reduction, with a smaller in diametre crown wheel, giving better ground clearance.

I was making them so that the Sun gear on the halfshaft could be moved into mesh with the planet gears for a 4:1 reduction for running 11.00x28 tractor tyres, or alternately the sun gear could be slid out of mesh with the planet gears and lock into the hub end plate for direct 1:1 drive for when running normal 9.00x16 tyres

Excellent idea! There was also a Leyland truck with a two speed diff, but can´t remember the exact model.

One of the best ways for making an axle "unbreakable" is the use of overloading protection devices. GKN made years ago some overloading hubs. A shame that they wheren´t commercialy succesfull.

[FridgeFreezer]

If only you could combine reduction hubs with extra ground clearance somehow....

[cackshifter]

Excellent idea! There was also a Leyland truck with a two speed diff, but can´t remember the exact model.

The 2 speed rear axle was made by Eaton, electrically shifted, a splitter rather than a range change, ie more like an overdrive. I think you'd have found it on some Boxer and Mastiff models.

[Soren Frimodt]

If only you could combine reduction hubs with extra ground clearance somehow....

Obviously I know where you're getting at But actually you could run a very small ring gear and subsequently gain more ground clearance. But as far as I know there would be even more parts to be worn in a epicyclic gear than a portal box, and maybe even more drag/ power loss?

[bill van snorkle]

If only you could combine reduction hubs with extra ground clearance somehow....

Wait ! I have some some old transfercase gears in the shed, and visualising if I umm ??

[Part1cle]

Provided they are designed correctly epicyclics are much more efficient than conventional parallel shaft type gears. The manufacture of them is much more complex though so cost may be prohibitive for these applications.