Drop axles - inverting.

[mdk]

I have a 2 axle trailer I want to raise a bunch. It has 3 inch drop axles, meaning the tube is round, and the cast ends the spindles bolt to curve upwards. I would like to raise this trailer about 6 inches, which would mean rotating the axles 180 degrees. Is this doable? It's a tandem axle, walking "dexter" setup between them. The reason for raising it, is to clear rough ground, of course.

I'd like to keep the axles I have, since they both have electric brakes, and there's nothing wrong with them, really.

Thanks for any input... and no, sorry, I don't have pictures right now.

[eamarquardt]

Here is a page that discusses your change. My initial reaction is no but WTF do I know. Apparently the folks making the axle mentioned don't see a problem.

http://www.expeditionportal.com/forum/t ... ailer-axle

Cheers,

Gus

[mdk]

Here is a page that discusses your change. My initial reaction is no but WTF do I know. Apparently the folks making the axle mentioned don't see a problem.

http://www.expeditionportal.com/forum/t ... ailer-axle

Cheers,

Gus

Interesting link. I have been wondering if the axle tube can turn (twist inside the ubolt). Perhaps I'd just have a buddy do a couple good tack welds on each side of the saddles.

There's mention of camber bends, and mine have camber bends. But I'm not all that concerned. I'm going to be using 215 - 75 /15 tires or larger, and the total weight on the axles should not exceed 2500 lbs, or 1250 per axle, 675 a tire.

[eamarquardt]

Here is a page that discusses your change. My initial reaction is no but WTF do I know. Apparently the folks making the axle mentioned don't see a problem.

http://www.expeditionportal.com/forum/t ... ailer-axle

Cheers,

Gus

Interesting link. I have been wondering if the axle tube can turn (twist inside the ubolt). Perhaps I'd just have a buddy do a couple good tack welds on each side of the saddles.

There's mention of camber bends, and mine have camber bends. But I'm not all that concerned. I'm going to be using 215 - 75 /15 tires or larger, and the total weight on the axles should not exceed 2500 lbs, or 1250 per axle, 675 a tire.

The camber bends will be working against you if you flip the axle. Typically there are "spring perches" welded to a round axle to keep the axle from rotating in the u-bolts. With the normal drop "up" it seems like it would be less of an issue (but perhaps still an issue). With the drop "down" it seems like it would be more of an issue.

Everything in life is a compromise. You might get enough additional clearance by just moving the axle below the spring if it's above the spring right now. Welding new new perches would be a big plus.

Go for it and carry a few spare u-bolts or whatever to perform "field expedient repairs" should the need arise.

Cheers,

Gus

[mdk]

The camber bends will be working against you if you flip the axle. Typically there are "spring perches" welded to a round axle to keep the axle from rotating in the u-bolts. With the normal drop "up" it seems like it would be less of an issue (but perhaps still an issue). With the drop "down" it seems like it would be more of an issue.

Everything in life is a compromise. You might get enough additional clearance by just moving the axle below the spring if it's above the spring right now. Welding new new perches would be a big plus.

Go for it and carry a few spare u-bolts or whatever to perform "field expedient repairs" should the need arise.

Cheers,

Gus

Hmmm... It didn't appear to me that the axles had perches welded to them, and that they just sat in saddles. Of course, I can be wrong about that. If they are welded, flipping the axle over will put the perch in the position of being under, rather than over, the springs. That would be perfectly fine with me, and the additional height would be a bonus.

I do need the clearance, just going from above to below the spring is not anywhere near enough. It is my intention that this trailer go over things only somewhat better than jeep trails. And the camber being the other way will only have an effect on tire wear, but since it will be so light, I don't predict any serious issue with wear.

[angib]

And the camber being the other way will only have an effect on tire wear, but since it will be so light, I don't predict any serious issue with wear.

That camber also helps the trailer tow better - it's possible that a flipped drop axle will be more prone to sway, but I don't know as I've never known anyone try it.

As well as the axle twisting in the shackles, I wonder if having the spindles that far below the spring will make the spring bend in odd ways when it hits a bump - something like the muscle cars used to do to one of their rear springs due to the torque. Again, I don't know, just thinkin' out loud....

[eamarquardt]

And the camber being the other way will only have an effect on tire wear, but since it will be so light, I don't predict any serious issue with wear.

That camber also helps the trailer tow better - it's possible that a flipped drop axle will be more prone to sway, but I don't know as I've never known anyone try it.

As well as the axle twisting in the shackles, I wonder if having the spindles that far below the spring will make the spring bend in odd ways when it hits a bump - something like the muscle cars used to do to one of their rear springs due to the torque. Again, I don't know, just thinkin' out loud....

I agree there are unknowns and that was my initial intuitive thought as noted above. I was kinda surprised when the fellow stated he'd had no problems and the axle's maker didn't seem concerned. I wonder how much engineering really wen't into the axles or if they were just built from "old Chinese customs".

Cheers,

Gus

[mdk]

And the camber being the other way will only have an effect on tire wear, but since it will be so light, I don't predict any serious issue with wear.

That camber also helps the trailer tow better - it's possible that a flipped drop axle will be more prone to sway, but I don't know as I've never known anyone try it.

As well as the axle twisting in the shackles, I wonder if having the spindles that far below the spring will make the spring bend in odd ways when it hits a bump - something like the muscle cars used to do to one of their rear springs due to the torque. Again, I don't know, just thinkin' out loud....

No, the camber does not improve the towing. The camber is there to make the tires wear better on a crowned road.

Reversing the camber will definitely improve towing... but will cause tire wear. However, since I'll have 2 3500 lb (or so) axles and less than 2500 lbs between them, I don't expect issues with towing, axles twisting the springs, or anything else like that.

[kludge]

The camber is there so that when the trailer is loaded it will flex slightly resulting in ZERO camber going down the road, giving optimum tire wear.

[mdk]

The camber is there so that when the trailer is loaded it will flex slightly resulting in ZERO camber going down the road, giving optimum tire wear.

Best tire wear is not zero camber. Best tire wear is a slight camber, to match the road crown.

Of course, this is all academic...

[angib]

No, the camber does not improve the towing. The camber is there to make the tires wear better on a crowned road.

I agree that is the 'common knowledge', but I'm going to hold off on believing that until I've seen some engineering evidence. Positive camber has been used on axles since horse-drawn days to improve straight-line running.

Negative camber is valuable/essential on low-aspect-ratio tyres on a racetrack and because of that it has become fashionable elsewhere - I don't doubt it would improve the ultimate lateral grip of a trailer, but that's not what we're after most of the time.

[KCStudly]

I think Angib hit the nail on the head when he suggested that spring wrap will be an issue. IMO it doesn’t really matter what the axle rate vs. load is when you are looking at a dynamic situation like hitting a pot hole.

Look at it another way. When the drop is installed as intended gravity is always trying to stabilize the axle’s rotation and therefore the spring will remain stable. If you flip the axle gravity will always be trying to torque the spring one way or the other, back and forth with every little, and not so little undulation in the road, resulting in many more cycles of fatigue. Depending on the dynamics of this effect it is quite possible that one end of the axle will be attempting to do the opposite of the other end, more so than in the standard configuration, and that could also result in a whole lot of cyclic loading on the axle tube itself...or could set up some wonky side to side oscillations based on minor wheel base changes (as the spring wraps it will change the relative location of the axle).

Don’t take offense, but the fact that you did not realize that the axle spring perches are welded to the axle tube shows that you are not especially knowledgeable on this subject. You may want to reconsider your confidence level at making critical decisions that might affect your and other’s well being.

Take the hubs and brakes off of your old axle(s); buy compatible bare straight axle(s) (gaining 3 inches) with spring perches factory welded in a “spring over” configuration (gaining another 3+ inches); install your existing brakes and hubs on the new axles, and stuff them under your trailer. It’s what I would do in your situation. (I’m a professional mechanical engineer and designer, if that makes any difference to you.)

Cheap isn’t always smart. Many times cheap isn’t so cheap in the end when things don’t end well.

Then again, it could be fine...Go for it!

[KCStudly]

And if that is not enough lift for you, look into changing your spring eye and equalizer hanger mounts. Dexter sells these in a few different heights. If yours are the short ones, you could gain another 5/8 inch by switching to the longer ones (or more if you space them away from the frame).

[mdk]

No, the camber does not improve the towing. The camber is there to make the tires wear better on a crowned road.

I agree that is the 'common knowledge', but I'm going to hold off on believing that until I've seen some engineering evidence. Positive camber has been used on axles since horse-drawn days to improve straight-line running.

Negative camber is valuable/essential on low-aspect-ratio tyres on a racetrack and because of that it has become fashionable elsewhere - I don't doubt it would improve the ultimate lateral grip of a trailer, but that's not what we're after most of the time.

The aspect ratio of the tire actually decreases the need for negative camber, as the profile becomes smaller numbers. But positive camber can't help in towing. There are two things that the trailer needs to do... One is stay on the ground and roll, the other is to follow the hitch. Side loads, caused by wind, cornering, etc, cause the higher profile tires to roll onto their sidewalls, allowing the tire to scrub. This scrub, combined with a driver driving improperly via feedback and tow vehicle having the same relative sideways motion combine together to provide a large amount of the instability that we see in trailers. Putting a little camber in the wheel decreases the level of scrub for a given side load, due to the tire planting more surface on the road during side load, combined with other tire dynamics. But put in positive camber, and the tire is hampered in preventing lateral motion. So, the camber can't be for quality of towing. Rather, it's there to reduce the bane of trailer towers everywhere, the blown tire, because you can't see the inside of the tread and you wore through to the cords while the outside appears serviceable. Typical settings for camber to maximize tire wear are around 1/2 to 3/4 degree. Front drivers often have negative in the back and positive in the front, and you better rotate a LOT. This creates understeer, because it's assumed the average driver can't handle what happens on a front driver when you hit the brakes and turn hard at speed.

Of course some may want that "understeer" tendency on the trailer, because the springs are canted and uneven roads cause bump steer.

[mdk]

And if that is not enough lift for you, look into changing your spring eye and equalizer hanger mounts. Dexter sells these in a few different heights. If yours are the short ones, you could gain another 5/8 inch by switching to the longer ones (or more if you space them away from the frame).

I'm going to be checking it out. That's off a bit for now. Still at least 2 months away. I have other projects waiting ahead of it.