Trailer axle question.

[arrow]

I'm building up a fire trailer (i.e. tank, pump, hose etc for when I burn off on the bush block) from an old motorbike trailer.

The current trailer is a bit low and I'd like to increase the ground clearance. The current arrangement is that the axle is mounted on top of the leaf springs and my thought is to move the axle to under the springs. Doesn't get me a lot of extra clearance, around 60-70mm, but better than it is currently.

Now, my question is, is it practical (and legal?) to mount an axle under the springs?
Might sound a basic question but I'm a total novice in this regard.

Is the axle under the springs the way off-road campers get their ground clearance?

What might I need to consider if I go down this path?

Thanks.

[ticky]

It used to be, but most off road campers these days have a Trailing Arm and Coil Spring on each side with a stub axle rather than a full width axle going right across the trailer.

In any event, putting the axle under the springs wont hurt. it will give you trailer body a bit more clearance but your axle is still pretty low. increasing the diameter of the wheels will help a little, but then so will driving on the centre and one shoulder of the track.

Steve

[Drewan]

I flipped the Axel on our van 4yrs and God knows how many is ago,needed that little bit extra lift to stop the back end bottoming out and bring the van up level without the towbal being to low ,keep in mind you also have to spin the breaks over as well 4 bolts on each mounting plate ( if there cable as the linkage points the wrong way ) as for legal every state is different but were on our third lap and it hasn't been an issue yet ( and I get pulled over a lot )

[Apollo]

My camper trailer is setup with the axle under. Rebound leaf springs.

[erad]

It is fairly common for people to flip the axles on their caravans to gain more clearance. This applies where you have round stub axles welded directly onto a square section main axle, giving a slight drop in the body ride height. Flipping the axle gives double the main axle thickness increase in ride height. It also is probably a bit safer, because the U bolts are now no longer supporting the weight of the trailer and its load in tension - the axle sits directly on the springs.

I had terrible tyre wear with my caravan - it had 10 mm toe-out. I flipped the axle and it had 10 mm toe-in. The misalignment is caused by the contruction method - they lay the stub axle opnto the main one and put a heavy weld in the gap. Shrinkage of the weld causes the axle to go out of line, and then they weld the other side, hoping that the weld shrinkage will bring it back. It doesn't. If you flip the axle, check the toe-in of the wheels. Eventually the axle manufacturer gave me a new axle (for free, including freight), but even the new axle has a 5 mm toe-in. Thusfar (about 25000 km), the tyres seem to be wearing evenly, but as they get down in tread depth, I expect that they will go uneven again. One tyre has a much higher pressure buildup than the other, and I expect this is caused by the misalignment generating a bit more heat that the other which runs true..

If your trailer is only a fire trailer and not to be used oin the road, who cares about alignment?

[arrow]

Thanks everyone, for your replies.

It's down that path I'll go.

[arrow]

Hopefully the final question.

With the U-bolts and flipping the axle to below the springs, does it matter which way the U-bolts go?

Currently the U-bolts face downward going over the axle first and then through a plate under the leaf springs. That is, the "U" is inverted.

When I put the axle under the springs, do the U-bolts still need to over the axle first and then past the leaf springs to have the plate fitted - in effect having the "U" the right way up - or can they go over the springs first and remain inverted?

[ticky]

Hopefully the final question.

With the U-bolts and flipping the axle to below the springs, does it matter which way the U-bolts go?

Currently the U-bolts face downward going over the axle first and then through a plate under the leaf springs. That is, the "U" is inverted.

When I put the axle under the springs, do the U-bolts still need to over the axle first and then past the leaf springs to have the plate fitted - in effect having the "U" the right way up - or can they go over the springs first and remain inverted?

I would flip the ubolts and reassemble as it was


Steve

[ticky]

It is fairly common for people to flip the axles on their caravans to gain more clearance. This applies where you have round stub axles welded directly onto a square section main axle, giving a slight drop in the body ride height. Flipping the axle gives double the main axle thickness increase in ride height. It also is probably a bit safer, because the U bolts are now no longer supporting the weight of the trailer and its load in tension - the axle sits directly on the springs.

I had terrible tyre wear with my caravan - it had 10 mm toe-out. I flipped the axle and it had 10 mm toe-in. The misalignment is caused by the contruction method - they lay the stub axle opnto the main one and put a heavy weld in the gap. Shrinkage of the weld causes the axle to go out of line, and then they weld the other side, hoping that the weld shrinkage will bring it back. It doesn't. If you flip the axle, check the toe-in of the wheels. Eventually the axle manufacturer gave me a new axle (for free, including freight), but even the new axle has a 5 mm toe-in. Thusfar (about 25000 km), the tyres seem to be wearing evenly, but as they get down in tread depth, I expect that they will go uneven again. One tyre has a much higher pressure buildup than the other, and I expect this is caused by the misalignment generating a bit more heat that the other which runs true..

If your trailer is only a fire trailer and not to be used oin the road, who cares about alignment?

The way around the alignment problem is to weld a plate to the end of the axle, as square as you can Best way is to set the plate so that it is a bit under square, and tack it in place. The tacks should pull it back to square. If not, adjust it with a hammer. Once square, tack the opposite side. It cant pull as the first tack is holding it. When you weld it, it will probably bend, but this can be hit back straight while still hot.

100% accuracy is not essential, but get it as close to square as you can.

When you have your Stub Axles turned, Have them turned from a billet large enough in Diameter to leave a base plate on the back end.

With a bit of forward planning, your Stub Axle Base plate can now be drilled to match the holes in the plate you welded to the axle. Bolt your Stub Axles to your Drop Axle and check the alignment. Adjust with Shims.

Your Welding should be done with a Mig Welder, or if you are using an Arc Welder, I would suggest Low Hydrogen Rod such as a 4816. Austarc 16TC are common and should be easy to find.

DO NOT USE 4812, or 4813. These are general purpose mild steel rods and not suitable for the job.

TIP. 4816 Low Hydrogen rods start reasonably easy but can be difficult to restart a partially used rod. The reason for this is the rod burns leaving the Flux Coating protruding. break off the protruding flux coating before striking your arc, this will make it a lot easier. If you have never used Low Hydrogen Rods before, Practice with them before doing your job.

Steve

[erad]

When you flip the axle, the original axle locating plates will be on the top. You don't have to cut them off and re-weld them. There is a centre bolt in the spring leaf nest, and this bolt protrudes slightly to align with a hole in the plate. If you flip the axle, the holes in the locating plates may not be 100% accurate. If this is the case, your trailer may track slightly off-centre, but you will probably not notice any difference unless you follow it in another car.

Again, check the toe-in (or toe-out), and if you are not happy with what you have, you can get the axle bent in the middle to give you the wheel alignment you are after.

I was given a new axle by AL-KO (the axle manufacturer) and I had to cut the locating plates off the old axle and weld them to the new one. This involved measuring distances from the towball to the centre bolt and getting them equal. I then tacked the plates in position, and removed the axle and welded it properly. For what it is worth, Jayco in their incomparable quality control checks actually fitted my caravan with the axle offset by 25 mm. It was nearly impossible to remove and replace the left wheel because there was no clearance past the body shell. I fixed that at the same time as fitting the new axle.