Newbie: Disco 6x6 from Spain

[o_teunico]

Exactly that!

[bill van snorkle]

PortalRover seems to use the expensive Ashcroft/Foley drop box.

Probably not so expensive if converting a new vehicle. But if starting out with a clapped out old Defender then the option, as I've mentioned before is to make your own from old series transfercase parts.

[Nigelw]

they quote the price of that drop box at £5000!!! It is air operated also meaning that the vehicle it is fitted to is part time 6X6, it does look very familiar though as Volvo use such a type of box transferring drive to the rear axle of their 6X6 dump trucks rather than through drive type axles where enormous strain can be put on the center axles crown wheel and with payloads in excess of 50T they prefer to take the drive up and over the center axle to drive the rear, so when the going gets tough you pop her in 6X6 and away she goes!

[bill van snorkle]

they quote the price of that drop box at £5000!!! It is air operated also meaning that the vehicle it is fitted to is part time 6X6, it does look very familiar though as Volvo use such a type of box transferring drive to the rear axle of their 6X6 dump trucks rather than through drive type axles where enormous strain can be put on the center axles crown wheel and with payloads in excess of 50T they prefer to take the drive up and over the center axle to drive the rear, so when the going gets tough you pop her in 6X6 and away she goes!

I think the drop box on the Volvo Dump trucks may have been an afterthought .Over here in OZ, the earlier Volvo 6 wheel dumpers were 6x4 drive. A little later they brought out an interim modification that consisted of smaller rubber intermediate wheels that fitted between the leading rear axle drive wheels and the undriven wheels on the rearmost axle, thus drive was transmitted to the rear wheels via the intermediate wheels through friction. The later addition of a drop box was probably seen as a cheaper alternative to designing a dedicated thrudrive axle.

[Nigelw]

I drove a 6X4 Volvo A25 and an 861 for a while, good enough most of the time but not so good in dry soft sand and sticky wet clay but apart from that you wouldn't know the difference, the drop box became necessary for them after the demand for 6X6 articulated haulers really took off, and Volvo knew that off road conditions were just far too aggressive for through drive center axles and also yes there was an enormous cost implication too as the system of using the drop box allowed uniform and standard components like axle casings and crown wheels and pinion gears, also it eliminated the engineering costs of producing the dedicated through drive axle, something which would see a rise in component costs for that axle but also meaning different tooling for the manufacturing, also the drop box was retro fitted to a great many haulers that were 6X4 when built new and only needing a center axle from a dismantled hauler, it is good to know that through the years they got the gearing right as it never changed from the first of the 5350 range right up to today's haulers and only changes slightly by the range capacities ie, A25, A30, A35, A40 etc.

Sorry, bit of a geeky subject for me LOL

[foxywan]

Hi all! This month's lroi mag has featured a home grown 6x6 defender 110. This got me interested.

And since over the last two weeks I've now got this urge to build one myself but on a series chassis after seeing bills creating from the 70's.

I've researched and read probably every post on the interweb about creating a 6x6, and I'm not going down the through drive version but will be looking into adapting a couple of transfer box's into drop boxes over each axle.

Bill if you're around to answer a couple of questions?

How did you mount the ends of the springs to each axle, was they both fixed or one/both mounted on a swinging hanger like the rear spring mount on standard set up?

And reversing the diffs meant driving on the coast side of the ring gear, but would a 2 gear drop box or even use of portal boxes enable the diffs to be used normally?

What orientation did you mount the shocks? Did you use 2 or 4?

And last one, how and where did the control rods/arms mount?

I've got on order the book that your 6x6 was featured and can't wait to read that.

This is in my system and now feel I can't not attempt this, it's on my mind 24/7!

I'm going to be using all land rover components, mainly for easy sourcing but also due to cost and limited funds. Looking at doing this over a few years.

Any info views and opinions appreciated

Gary

[bill van snorkle]

Hi Gary, welcome. I will be interested in following the progress of your build.

To answer your questions more or less in order.

The ends of the springs also located the axles laterally in lieu of a panhard rod, so they had the eyes cut off and were mounted to the axles on boxed slipper pads. The centres of the springs were clamped to a channel section saddle welded to the centre pivots to prevent the spring ends swinging laterally.

It is very difficult to get enough distance between the input and output shafts, for the propshafts to clear the axle housing if only using a drop box with 2 gears. I would have required a pair of 9 1/2'' diameter gears per diff to get the offset required, which woulld have precluded using LandRover parts.Unfortunately back in the 70's I didn't have the option of using reverse cut Ashcroft or KAM crownwheels and pinions, which would have addressed the issue of driving on the coast side of the teeth.

Due to the large amount of articulation the bogie was capable of and the non availability of extreme travel shock absorbers back in those days, I deduced that I only really needed to dampen the rebound forces of a flexed spring returning to its normal shape, so I instead of mounting the top of the shocks to the chassis I attached them to boomerang shaped mounts welded to the spring pivot clamp plates. 4 standard series front shocks in total were used.Near the end of the video of post #215 on page 11 of this thread the boomerang shock mount can just bee seen.And on post#128 page 7 it can be seen more clearly.

The control rods were orientated similar to most leaf spring bogie drive assemblies, in that the single uppers ran from a bracket on top of each diff to a crossbeam half way between the axles. the lower control rods ran from brackets welded to the axle housings just below axle centre line the same mounting that the spring pivot hubs were bolted to. The photo of the under carriage of the Volvo C306 on page 6 would give you some idea of the control rod layout. The main area that my bogie differed from conventional is that the spring pivot hubs and control rods were all attacked to a cross beam that was independant of the chassis and connected to it via 4 additional parrallel links and two vertical telescopic struts in order to fully exploit the maximum articulation that the double dropbox straight propshaft arrangement allowed for.

The other bits of advice I offer is that although SWB chassis can be extended and strengthened to accomodate the extra axle, a series 1 LWB pick up chassis is much more suitable if you can find one in good condition. LWB series 2/3 chassis are quite unsuitable, as are coiler chassis without extensive reworking.

The other advice is that in the long run it worked out cheaper for me to buy a centre lathe than to farm out machining work for the conversion. Despite initial reservations as to their strength, series stub axles (spindles proved adequate to support the spring pivot hubs.Series 1 hubs are of a weldable material and after machining off the wheel mounting flange, the spring mounting saddle can be welded to it.

Contrary to my advice a few pages back, I think it is best to fabricate slimmer drop boxes from steel, than to rework and fit series t/cases to the diffs. just use the helical gear from the intermediate gear and 2 high range output gears for the 1:1 ratio required, plus the t/case output shaft and a PTO dog clutch to disconnect drive to leading axle diff. To reduce machining and material costs,drop box upper bearing carriers can be made from the bearing carrier section of scrap series front axle swivel balls and the removable oil seal retainers from t/case front output housings or early series diffs can be used

[bill van snorkle]

I ran out of editing time, but I was going to comment that if I could be bothered making another pair of portal boxes for the 3rd axle I think I could resurrect my old 6x6 with the running gear from my present 4x4,that would have an overall cross country performance that would make the Mercedes 6x6 above look fairly ordinary.

I have also just determined that by using old swivel balls as bearing/oilseal carriers for both the upper and intermediate shafts,if you were extremely accurate with their spacing, you could avoid the expense of having the fabricated drop box housings bored on a milling machine. To make fabrication of the drop boxes seem less daunting, structural steel channel section is a good base to start with. just box in the endswith flat or pipe and make a flat bolt on lid. I have a piece of channel here that with external measurements of 150mm x 74mm with flanges 10mm thick that would be ideal for the job. just need to clearance the internal width a little with an angle grinder to clear the intermediate gear diameter of 133mm.

Just for future reference in case I want to make another drop box, the shaft spacing between the intermediate gear and the input or output gears is 112.985mm BC.

[o_teunico]

Oh yes, a real 6x6 and not a "vapour build" like mine! Foxywan, it will be great to see your progress in the "special and moddified vehicles" subforum, as well as Bill´s resurrected 6x6

[foxywan]

Wow Bill!

You are a gentleman and a scholar!

I wasn't expecting such a detailed answer than you so much.

I hadn't seen anywhere how the bogie pivot was made and I had planned on using stub axles & hubs with the use of hub bearings and your suggestion of using the same gives me faith in my ideas.

And yes I can see using home fabbed drop boxes instead of making t/cases fit would be better having a purpose built system.

I'll be putting pencil to paper next drawing up the system and getting myself familiar with layout required.

When I get this up and running I'll create a post and certainly keep you informed,

Many thanks again

Gary

[foxywan]

Oh just out of interest what was the trucks behavior like on tarmac at speed?

Gary

[bill van snorkle]

Wow Bill! You are a gentleman and a scholar! I wasn't expecting such a detailed answer than you so much. I hadn't seen anywhere how the bogie pivot was made and I had planned on using stub axles & hubs with the use of hub bearings and your suggestion of using the same gives me faith in my ideas. And yes I can see using home fabbed drop boxes instead of making t/cases fit would be better having a purpose built system. I'll be putting pencil to paper next drawing up the system and getting myself familiar with layout required. When I get this up and running I'll create a post and certainly keep you informed, Many thanks again Gary

You are most welcome Gary. As to the question about overall handling characteristics. It was much better than I expected.Directional stability was as good as a standard LWB. The rear bogie rode much more smoothly, with less vertical movement of the vehicles body for a given size bump than is the case with a single rear axle. The lower control rods were arranged so that when the vehicle was sitting on level ground, the rods angled down slightly to the axle mounts, so that when for example the vehicle is making a left hand turn at any sort of speed, the r/h/side control rods flatten out, pushing the 2 wheels on that side a little further apart, whilst at the same time the l/h/side control rods pull the 2 left side wheels a little closer together, thereby reducing the understeer and tyre scrubbing that is normally associated with short wheelbase 6 wheelers.

Funny, I had a dream last night that someone gave me 3 series 1 LWB pick ups. So as much as I try to resist, my sub concious is trying to convince me to do a resurrection.My local vehicle modification regulations these days would make getting approval prohibitively expensive unfortunately.

[foxywan]

Just an update.....

I've been doing some rough sketches and have nearly finalized a suitable design for the layout of the rear bogie.

Still need to do some plans to scale tho, once I've done that I'll take pictures and post for criticism.

Also been researching reverse cut crownwheel's and pinion's and the cost is about £195 per set.

Thought I had a brainwave when at one point, I pondered on using the front diff in the rear as that rotates the other way thinking that would be reversed....but no. The front diff is driven on the coast side of the crownwheel as design. Shocked at that. Only one diff in the entire LR range has a reverse cut cw/pinion. Can't remember which one now. The front diff is driven on the coast side of the crownwheel as design.

But I found a couple of different documents and "expert" info regarding best of the standard stock and I've narrowed it down to the rear axle from a late 110 (think the td5).

It has a short nose diff and is a four pin unit.

The short nose should help with space especially enabling a longer prop to the rear axle. And from what I've read it's close to the strength of the Salisbury unit but a he'll of a lot cheaper to rebuild if it ever went pop

Gary

[Hybrid_From_Hell]

P38

N

[foxywan]

Yes but only the v8 has the four pin under its ar$e.

The Short Nose 2 pin is fitted to all P38 Front and Rear, but the 4.6 V8 has a 4 pin Rear Diff as does the 110 Rear, the 110 front diff is a good old standard
2 pin Long Nose type unit

Gary

[bill van snorkle]

Only diffs up to and including series 2a have a bolt on pinion seal retainer with six 5/16'' bolts, the holes of which can be opened up to 3/8'' to bolt the drop boxes to.

In practice,in most cases it is preferable for the front diff to drive on the coast side of the teeth, because when climbing or pulling/towing weight transfer is to the rear axles. When reversing up hill or out of a ditch for example, weight transfer is to the front diff which is now driving on the 'drive' side of the teeth. It was when Toyota went to reverse cut front diffs on their LandCruisers that they started experiencing a high incidence of diff failures.

[foxywan]

Ahh cheers for that Bill, saved me some more swearing in the future

Gary

[bill van snorkle]

Ahh cheers for that Bill, saved me some more swearing in the future

Gary

No worries. It is also advantageous to have the more widely spaced pinion bearings of the earlier diffs .they cope with the side thrust generated by the drop box gears much better than p38 type short nose diffs.

[foxywan]

<p> </p>

<p>Long nose it is then and 2a diffs at that. Just looked under my 2a and it looks as though a PO has put series three axles on front and rear as there isn't a bolt on seal retainer. Knew the front was later as it's got the fat 11" drums fitted.</p>

<p> </p>

<p>Really fancy having discs for this project and have just found out that all long nose diffs fit all axle casings but may have to remove a Dowell or two.</p>

<p> </p>

<p>The number of splines could be a problem but I do fancy making and using portals so not really an issue, as I can make to suit my own needs. </p>

[foxywan]

<p> </p>

<p> </p>

<blockquote class="ipsBlockquote" data-author="Hybrid_From_Hell" data-cid="711024" data-time="1365020276">

<p>P38 <img class="bbc_emoticon" src="http://forums.lr4x4.com/public/style_emoticons/default/tongue.png" title=":P" /><br />

<br />

N</p>

</blockquote>

<p>I've only just realised but I quoted your own words from another forum! </p>

<p><img alt=":blush:" class="bbc_emoticon" src="http://forums.lr4x4.com/public/style_emoticons/default/blush.png" title=":blush:" /></p>

[foxywan]

And apologies for the weirdness posted in my last couple of posts, pc gone a bit doolally

Gary

[bill van snorkle]

One variation on the bogie suspension that I would have liked to investigate is the so called British 'War Department patented torque reaction articulated suspension', which was reputed to have certain traction advantages when compared to the common pivoted inverted leaf spring with 6 control rods.These suspension systems were fitted to many British made prewar and wartime 6x4 military trucks of all makes. Unfortunately the Australian forces during that time used mainly American and Canadian built trucks, so I have never actually seen a truck fitted with this type of suspension, but I believe the description as follows is fairly close.

The pivot hub has 2 separate leaf springs bolted to it, one above and one below.The eyes on the ends of the springs bolt above and below the axles to hangers that are fabricated integrally with trunnions that are fitted concentrically to the axle tubes and are free to rotate around them via a large bronze bushing . Thus it would seem that the springs themselves are the lower control rods, and there is just a single rod on top of each diff running to a central crossmember.

The trunnions would probably be the difficult part to make,especially as LandRovers don't have precisely round axle tubes, but if there are positive traction advantages to be had then it might be worth investigating.

The latest truck that I am aware of to use this type of bogie was the 6x6 Rolls Royce straight eight powered Thornycroft Nubian airport crash tenders circa 1960's, but in the UK with a number of military vehicle museums scattered around, there should be a few examples of the wartime Morris Commercial, Austins etc that could be viewed.

[foxywan]

Had a quick browse on the thornycroft's, think I saw a piece saying there's a Nubian fire tender in a museum in Melbourne, don't know where you are in AUS.

I did find a UK model shop selling a fully working Nubian and antar models in die cast for about £25, might get one just to see the working suspension albeit on a small scale.

[bill van snorkle]

Had a quick browse on the thornycroft's, think I saw a piece saying there's a Nubian fire tender in a museum in Melbourne, don't know where you are in AUS.

I did find a UK model shop selling a fully working Nubian and antar models in die cast for about £25, might get one just to see the working suspension albeit on a small scale.

Thanks Gary, I am in a country region just out of Melbourne, but sadly the museum that the Thornycroft Tender was in closed down a few years ago.

[discomark10]

just seen this http://www.ebay.co.uk/itm/Land-Rover-Defender-170-Genuine-6x6-Camper-Expedition-Overland-/330898055506?_trksid=p2047675.m1986&_trkparms=aid%3D555001%26algo%3DPW.CURRENT%26ao%3D1%26asc%3D29%26meid%3D7030871783087002129%26pid%3D100013%26prg%3D1013%26rk%3D1%26sd%3D151024934888%26