Converting Series 3 rear end into trailer - tech questions

So are there particular specs for Qld and where can these be found? I had heard that the axle had to be in the centre of the "box" part of the trailer, this is the reason a lot of tub to trailer conversions have a tool box on the front, and yet a lot of boat trailers have the wheels towards the back end.

Also what is the consensus on drawbars? One up the middle with some supports like the army trailers or an A frame? Are there any advantages to either system apart from amounts of work and steel required?

And what are peoples suggestions regarding axles? There are a lot of ready made ones, but not designed to take landrover hubs. How solid or thick should an axle tube be? Are there any real differences between using a round and square tube for an axle?

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Originally Posted by pfillery

So are there particular specs for Qld and where can these be found? I had heard that the axle had to be in the centre of the "box" part of the trailer, this is the reason a lot of tub to trailer conversions have a tool box on the front, and yet a lot of boat trailers have the wheels towards the back end.

Also what is the consensus on drawbars? One up the middle with some supports like the army trailers or an A frame? Are there any advantages to either system apart from amounts of work and steel required?

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The national trailer design specs call for the wheels on box trailers to be not further forward than the centre of the box - hence the tool boxes in front, these are counted as part of the box. The idea of this is to ensure that the towbar always has positive download. Boat trailers can often have the wheels well towards the back without excessive download for two reasons - the boat often overhangs the rear of the trailer, and if the boat is an outboard one, its centre of gravity is well back due to the heavy motor.

For a light trailer, I would only use an A frame, as this will give the best strength/weight ratio. However unless you are really trying to reduce weight, the difference will not be all that significant.

John

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Originally Posted by pfillery

And what are peoples suggestions regarding axles? There are a lot of ready made ones, but not designed to take landrover hubs. How solid or thick should an axle tube be? Are there any real differences between using a round and square tube for an axle?

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I have seen suggestions that fabricated axles are not accepted, but I have yet to find anything confirming this.

A larger diameter tubular axle will be lighter than a solid one of the same strength.

There is no practical difference between square and round axles, whether solid or tubular, except possibly that round rather than square U-bolts will be stronger.

Hubs to fit Landrover wheels are available (you'll probably have to get them ordered in), but not with the correct stud type - they are 5/8"UNF not 16mm or 9/16"BSF from memory.

This was why I was contemplating having a plate welded to each end of an axle tube, the same distance apart as a diff with the hubs removed, onto which the wheel spindles from a series 3 could be bolted (so they can be replaced if needed) or welded if this is the requirement. Thus I can fit landrover hubs to it. I guess what I need to find is what wall thickness of tube is a minimum for strength, and then provide some specs to a proficient welder for fabrication (beyond my skills and I don't want to lose a wheel).

I feel that it would be less effort to start from scratch rather than try and modify an existing axle.

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Originally Posted by JDNSW

I have seen suggestions that fabricated axles are not accepted, but I have yet to find anything confirming this.

A larger diameter tubular axle will be lighter than a solid one of the same strength.

There is no practical difference between square and round axles, whether solid or tubular, except possibly that round rather than square U-bolts will be stronger.

Hubs to fit Landrover wheels are available (you'll probably have to get them ordered in), but not with the correct stud type - they are 5/8"UNF not 16mm or 9/16"BSF from memory.

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Quote:

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Originally Posted by pfillery

This was why I was contemplating having a plate welded to each end of an axle tube, the same distance apart as a diff with the hubs removed, onto which the wheel spindles from a series 3 could be bolted (so they can be replaced if needed) or welded if this is the requirement. Thus I can fit landrover hubs to it. I guess what I need to find is what wall thickness of tube is a minimum for strength, and then provide some specs to a proficient welder for fabrication (beyond my skills and I don't want to lose a wheel).

I feel that it would be less effort to start from scratch rather than try and modify an existing axle.

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If you are doing this, I would suggest a diameter the same as the axle housing - to match the flange to be bolted to the sub axles, and to use the standard U-bolts.

While it would be possible to calculate the wall thickness for the requires strength from the spring locations and the bending moment applied by the maximum load with a suitable factor for bumps and then a safety factor, I suggest that this will probably come up with such a thin wall that it will be excessively prone to damage from rocks etc. I would look at the wall thickness of the Rover axle housing - it need be no thicker than that, as the loading is less and has no torque to deal with. From memory that is about 2.5mm.

John

In simple terms, the "load area" in front of the axle centre is to be greater than (or equal too at the very least) the "load area" behind the axle. It is common to mount the axle 50mm back from centre to achieve this. Ute tub trailers usually include the toolbox on the drawbar aspart of the load area. This then complies with the "load area" regs

If you are not going to run brakes, then I advise keeping the tare wieght as low as possable. A standard 39mm solid (round or square) axle is rated at about 1000kg. A 45mm axle is about 1400/1500 kg. It would probably be cheaper, simpler and lighter to run a normal trailer axle as supplied by most trailer shops. Landy hubs are not that hard to come by, but as stated, they may just be an order-in thing. The A-frame drawbar would be the best option for strength versus weight unless you are chasing the particular "look" of a military trailer.

link for National guidelines

Vehicle Standards Bulletin VSB1

HTH

Just check the shape of the chassis and the cross sectional shape of the chassis also. It potentially may not be very good for attaching the drawbar with a decent seperation between the front welds and the rear welds, the drawbar height or a good flat surface for making the actual weld. Then again, it may be ok, but the seam is in a funny place for what is essentially RHS.

For the axles, 39mm round is the lightest, 40mm square is next strongest and then 45mm square. If its only being rated to 750kg then the round axle will be ok, considering its being built for 4WDing then I'd use the 40 or preferably 45mm square. Also slimline bearings. You can get LandRover stud pattern hubs off the shelf - see an Alko retailer. I would remove the entire factory axle and keep it complete, save the weight and use a manufactured trailer axle that is 1/4 the weight and wont drag. You can also set the track if you want it wider than a regular narrow series setup - or keep it the same. The axle, about 50-75mm rearward of the box's centreline - the aesthetics may not work.

For the drawbar, for that load rating we use typically 75x50x4 and create an A-frame. I wouldn't use a single drawbar, there is too much stress that is generated across the drawbar and it will probably crack or bend. The Mil do it with a massive section and very short trailer, but you're conditions are not the same. Dont weld across the top or bottom plates of the drawbar anywhere except at the coupling plate and you will need to work out how you're going to put a satisfactory front cross member in to the chassis so that you can attach the drawbar to that.

As suggested, I would also pull leaves out of the spring pack, but I wouldn't bother resetting them. There is too much load carrying capacity as a fully laden 4WD let alone as a light box trailer. It also sounded like you or someone was talking about trailer slipper springs, these don't sit on the chassis, the bear on a wear plate which is welded to the chassis. For 4WD applications they still use leaf springs with shackles - these are quite stiff for their load rating to handle the roughness. A trailer with the light 4WD springs, I can get onto one of them and jump around and they don't move much at all!

Shocks - for 4WD applications - yes.

I have made heaps of trailers and if doing a Landrover trailer over again I'd still use the Rover Chassis / suspension / axle complete. All things considered your wasting your time & money by going any other path & you will have a much better trailer to boot. The standard body on a home made chassis won't cope with whatever weight gains your trying to save by going the other way. Infact I doubt you'll save much at all. Its no trouble to tow a trailer full to the top with screenings on a standard chassis. You just won't do that on a standard single axle.

Rather than use the full rover rear axle I usually just make a new axle from tube then weld flanges on the end & bolt LR or Toyota stubs to it

anyway whatever way you go there is some good trailer resource stuff here
http://www.spinnythings.com.au/pub/CATALOGUE.pdf

I have built 3 with success. Travelled extensively well loaded.
80's Rangie with various tray. First 2 with alloy 1 ton tray and current extended 130 tub.
Overide brakes and diff centre removed and blanked off.
Weight 520kg with spare and tray, toolbox, original tank and support legs.

I did over 65k in the north and desert towing unit thru kimberlies, Arnhem land and cape with no problems.
Only difficulty is sorting correct springs. Id like to try airbags in springs. I am also going to retfofit a swaybrace.

Its the cheapest way to build a trailer with the best suspension around and LR stud pattern and disc brakes.