Question regarding dropped axle, flipped?

[ExpoMike]

I was checking a thread on NAXJA and one person was using a dropped axle but flipped over so it became a raised axle. Here's the pic,

Is this a workable solution? It would surely save me a lot of hassles with putting matching wheels/tires onto our Kamparoo without doing a full suspension redesign.

Thoughts??? :ylsmoke:

 

[ntsqd]

I think that it's viable, but within a small set of conditions. The now lift distance is going to put a large leverage on the spring perch and leaf springs. Any hard hits to the tire tread will be magnified at the spring.
Another issue is if there is camber in the axle. Some drop axles have camber built into them to offset flex under normal loading. If the axle chosen has this feature then the camber will be wrong when flipped over, and it will only get worse as the load on the axle increases.

So if there is no camber in the axle chosen and the roads that the trailer will be towed on are smooth then I think it's viable. As the road condition worsens the loads on the spring perches, U-Bolts, and springs themselves will increase. Where the failure point is I don't know, but I would expect it to be not too far out there.

 

[njtaco]

I can't say it any more eloquently than above, I just plain see that as a bad idea for anything outside my back yard.

I'll add this anyways...I flipped a tandem spring under drop axle to a tandem spring over "raised" axle to net about a FOOT of lift, and after spending all the time and a little money, scrapped the idea. It was too much leverage in all the wrong places. Think about safe braking, and the twisting forces on all the parts...

How much lift do you need? Will a straight axle direct replacement be enough?

Out of curiosity, is the axle on your camper spring over or under?

 

[mtbcoach]

I was planning on doing the same with my build up of my M416. I've talked with ABC and there is no issue with the camber, just tell them what you want and they will do it.

However, I'm confused with this...

I think that it's viable, but within a small set of conditions. The now lift distance is going to put a large leverage on the spring perch and leaf springs. Any hard hits to the tire tread will be magnified at the spring.

I believe that I have an idea of how this will change the effective leverage of the suspension, however, wouldn't it be effectively the same as putting a larger set if tires/wheels on and/or doing a spring over conversion. I was planning on softening the suspension up a bit from the stock leaves, so its also a good idea to beef up the spring perches also...

 

[ExpoMike]

I can't say it any more eloquently than above, I just plain see that as a bad idea for anything outside my back yard.

I'll add this anyways...I flipped a tandem spring under drop axle to a tandem spring over "raised" axle to net about a FOOT of lift, and after spending all the time and a little money, scrapped the idea. It was too much leverage in all the wrong places. Think about safe braking, and the twisting forces on all the parts...

How much lift do you need? Will a straight axle direct replacement be enough?

Out of curiosity, is the axle on your camper spring over or under?

Our Kamparoo is already a straight axle, spring over setup. The current tires are 26" tall and I want to put the matching size of our Cherokee, which is 31". I already have a spare set of matching wheels and correct size tires. This would keep all of the wheels/tires the same between the Cherokee and trailer. Since the Kamaroo has the wheels under the main box, there is not the clearance nor can I move the fenders up, since there are none.

So what would be the difference between this "fipped" axle and running lift blocks?

 

[Martyn]

The drop arm creates a leverage arm that will put a twisting force on the spring and spring purchase. The leverage will be greater as the tires get larger. I have no numbers to work with so I don't know if it's a major or minor problem.

A few issues with the trailer in question.

The springs are way too short to really work well off road. Rule of thumb, eye to eye distance should be 36".

A rear shackle and a drop axle???

Spring attaching below the chassis via U tube section?

This combination look weak and prone to failure.

Personal observations, not AT diagnosis.

 

[ntsqd]

I was planning on doing the same with my build up of my M416. I've talked with ABC and there is no issue with the camber, just tell them what you want and they will do it.

However, I'm confused with this...

I think that it's viable, but within a small set of conditions. The now lift distance is going to put a large leverage on the spring perch and leaf springs. Any hard hits to the tire tread will be magnified at the spring.

I believe that I have an idea of how this will change the effective leverage of the suspension, however, wouldn't it be effectively the same as putting a larger set if tires/wheels on and/or doing a spring over conversion. I was planning on softening the suspension up a bit from the stock leaves, so its also a good idea to beef up the spring perches also...

Since the wheel bearings have moved down away from the spring it's more like running a very large lift block than going to larger tire. Braking forces and any tire vs. obstacle impacts will act the same as if it had those terribly tall lift blocks. If only going on pavement to the State Park is the plan it's not something that I'd do, but it'll work. If stuff bordering on the Rubicon or the road from Mexico 1 to El Arco is the plan then I'd say the springs will die an early death if the spring perches or u-bolts don't fail first.

Be careful with softly springing a trailer. Since there are no people riding in it the goal is to only soften the ride to the point where things don't get broken in transit. If you go too soft the trailer can easily sway and flop on side-hills. Sway control is one of the reasons that typical trailer springs are so short and stiff. A trailer doesn't need to articulate, it has the coupler to allow that motion.

 

[Martyn]

To me the crux of the spring issue is the weight variations a trailer has to work in. For example an unloaded base Chaser weighs 700 lbs, but a typical loaded configuration is up around 1400 - 1650 lbs. 0r 100% - 136% increase in weight. The maximum load my Grand Cherokee can carry is only an increase of 55%. So we are dealing with much greater magnitudes.

The solution has always been to rate the spring at the maximum load plus a safety factor. So in our case the springs would have to be rate 160% above the unloaded weight. This would produce a very stiff ride.

The shorter springs have much less ability to absorb the movement caused by uneven terrain and produce a bumpier ride than a longer spring. There is no reason a long spring can't be utilized. A long spring doesn't have to be overly soft.

Sway is an issue if the springs are too soft, but it can be compensated for by shock absorbers that are correctly valved (I didn't see any shocks on this trailer), and the use of bump stops.

It's a little more complex than it first appears. With a little planning and forethought there is no reason a trailer can't be made to perform admirably off-road.

 

[ntsqd]

Agreed. Those short, stiff springs are intended and idealized for pavement constricted trailers. In that use they are very efficient as being that stiff they really don't need dampers. Taking them off road is asking more of them than they were designed to do and is a misapplication of them.

In thinking about the 'upside down' drop axle it occurred to me that it really doesn't matter whether it is flipped or not, the leverage on the spring is the same. There will be some increase in leverage if while flipping it there is also a spring over axle conversion performed (by the thickness of the spring pack).
The difference is in taking it off road. No doubt that the axle was designed to live with the occasional pothole impact, but an average off road trail will make the axle think that it's on the worst of all Detroit roads.

With typical stiff trailer springs the idea is viable for mostly smooth road use as it really is no different than the intended orientation. As those roads get more rough, or a spring over conversion is performed, and as those springs get more supple the idea becomes less and less viable.

 

[BigAl]

So what would be the difference between this "fipped" axle and running lift blocks?

Not sure, but instead of lift blocks on the axle, could you weld 2" or 3", ~3' long box tube to the frame and then weld the spring hangers to that? You'd get the same net heigth gain without lift blocks. A 2" frame spacer would allow a for 4" taller tire?

 

[njtaco]

So what would be the difference between this "fipped" axle and running lift blocks?

Late to party, but IMHO, not much difference. I don't like them either...:Wow1:

If the trailer suspension were to be raised, in your case, I think I'd mount longer, "taller" springs on appropriate perches, upgrade the axle for the bigger wheels and tires, and install bumpstops and shocks. Why the bigger axle? So you get proper bearings and brakes for the taller/heavier tires. You also get to pick the WMS-to-WMS distance for your choice of rims (backset). If there is room to leave the original perches without causing interference, all this would be reversable, for the day you sell the trailer.

IMHO, of course. I realize this is not the most cost effective, but it could be done in stages too.

Dang, it's easy spending other people's time and money...:wings:

 

[ExpoMike]

Thanks guys for the reality check. I have been debating lifting the Kamparoo, not because it needs any more clearance (actually has more then my Cherokee) but because I wanted to run the same wheel/tire combo. Down side is it will make it more top heavy due to a higher CG and will make stepping into it higher.

There is just something cool about the tow rig and trailer having matching wheels/tires. Ideally I have been thinking of airbag setup, even with a straight axle. It would give me the ability to have the clearnance but lower it to keep the step in height the same. I also feel it would "cushion" the trailer ride better then leafs or coils.

 

[ntsqd]

IF one were going to "block it" I would prefer to see them at the frame rather than between the axle and spring. The reason is simple, there's a LOT more interface between the frame and a block than is possible at the spring & axle.

IMHO the only way to do this is to cut off the existing mounts and build a sub-frame that runs from the front mount to the shackle hanger. Put the new spring mounts on the bottom of that. It should also have cross-members that tie the two sides together. It could easily be a simple rectangular box made from rectangular tube, doesn't have to be fancy.

 

[mtbcoach]

Thanks for all the replies and information.

I'm an admitted noob to building up a trailer and appreciate the feedback. My objective differs than the OP in that I was looking to improve some ground clearance as well as fit 35's that are the same as on my tow vehicle. In my rational, I saw this axle option similar to a portal axle, going for a similar benefit. I was kind of surprised that I didn't see anyone doing this, I guess I know better as to why.

I'm still in the very early stages of my build up, just getting the frame/tub/fenders sandblasted and haven't started the "build up" part yet. However, the frame/axle configuration is the first stage of the build up and want to be sure that I don't have to go backwards once I get started.

So, it appears that if I'm planning on much off-roading, planning on building a "Rubicon capable" trailer, looking to use one of these flipped-drop axles is NOT a good idea.

Or, doing such would require a higher degree of importance to the spring perch strength and associated suspension hardware/components...

 

[ntsqd]

Portal axles require significant effort to allow for that increased leverage and to deal with the forces generated safely. The inverted dropped trailer axle could be used if the same design approach is used. Doesn't seem worth the effort to me when there are many other, more important challenges in building a trailer that will work and last and the gain over a straight axle is so small.