Teardrops n Tiny Travel Trailers

After putting two coats of Rust Bullet on my frame steel I reassembled it then got everything aligned and tightened down. When I measured the vertical height of each wheel hub with respect to the top of the frame steel I found that there was an unexplained difference.

Here is the set-up.

The axles are the adjustable ones bought from Southwestern Wheel.

The frame is squared with the full length diagonals measuring within 1/16” in length.

The front center of the tongue is squared to the rear corners of the frame within 1/16”.

The hubs are aligned to the front center of the tongue within 1/16".

The measured height between the top of the frame and the top of the splines of the half-axles is the same within 1/32”.

But the measured height between the top of the frame and the top of the wheel hubs shows a 1/4” difference.

In a thread started on 3/5/06 George T said he saw 1/2” height change for each spline change so that seems to indicate that this is not a situation that the adjustable feature will correct.

So, do I have just a puzzle here or a real problem that will affect the handling of the trailer?

It appears that the difference might be caused by a difference in the setting of the rubber inside the tube.

Has anyone using these axles seen anything like this?

The axles have never been loaded with any weight and the measurements were taken while the frame is supported by the steel resting on four tables with no wheels attached.

I have some 3/16” steel flat bar that I could put between the half-axle with the shorter measurement and the frame reducing the difference to 1/16” if necessary.

Don’t panic, Just build it.

While it's certainly a puzzle, I doubt it's a problem. If I understand correctly, while your frame is square and the axle square to the tongue, one of your hubs is slightly higher than the other? 1/4" on a diagonal is pretty negligible as this is not a static measurement anyway. As you load the trailer this measurement will change. Air pressure in the tires will make a larger difference in dynamic hub height I would guess.

If you're still concerned, put your wheels and tires on (measure frame height at axle after tires are on to check) and load up the trailer with several hundred pounds of stuff. Take it for a test drive and see how it pulls. If it: a) pulls fine and b) doesn't look goofy, then I would vote for moving on! Just my two cents...

Brad

This is a built in feature it is to allow for the weight of an on board battery to be installed on the high side then they will be loaded equally.




Just kidding but it sure sounded good !

But seriously are you gonna weigh every item and equally divide and place them at a given distance from the centerline of the tear so as to have your cargo dispersed equally. I DON'T THINK SO !

We just throw it in and go campin'

1/4 " 1/4 "

Just in case it matters, you might call Southwestern wheel and talk to a Tech. Might not be right! It never hurts to ask.

GeneH wrote:After putting two coats of Rust Bullet on my frame steel I reassembled it then got everything aligned and tightened down. When I measured the vertical height of each wheel hub with respect to the top of the frame steel I found that there was an unexplained difference.

Here is the set-up.

The axles are the adjustable ones bought from Southwestern Wheel.

The frame is squared with the full length diagonals measuring within 1/16” in length.

The front center of the tongue is squared to the rear corners of the frame within 1/16”.

The hubs are aligned to the front center of the tongue within 1/16".

The measured height between the top of the frame and the top of the splines of the half-axles is the same within 1/32”.

But the measured height between the top of the frame and the top of the wheel hubs shows a 1/4” difference.

In a thread started on 3/5/06 George T said he saw 1/2” height change for each spline change so that seems to indicate that this is not a situation that the adjustable feature will correct.

So, do I have just a puzzle here or a real problem that will affect the handling of the trailer?

It appears that the difference might be caused by a difference in the setting of the rubber inside the tube.

Has anyone using these axles seen anything like this?

The axles have never been loaded with any weight and the measurements were taken while the frame is supported by the steel resting on four tables with no wheels attached.

I have some 3/16” steel flat bar that I could put between the half-axle with the shorter measurement and the frame reducing the difference to 1/16” if necessary.

I doubt that each spline change is 1/2", but is easy enough to do so I would just pull the hub off and set it on in a corrected position. I would do this after the trailer is finished and towed at least for a few miles or more. I bought the adjustable axles just so I could do this. I didn't like the height of mine when I was finished so I pulled the axles and lowered it a bit. I still think it can go lower so this year i will try to mount my camera to the bottom and pull it in and out of a steep drive way and judge how low I can go and then pull the axles and adjust it.
Getting opinions and ideas from others is a good start, but I like to actually see from experience how things work out, especially something as easy as changing ride height.
Brwbier

I wouldn`t worry, if you have the chassis lifted off the floor with no wheels on when you are measuring. If the axle is made the same as torsion axles are over here it has 3 (or 4) lengths of rubber which are designed to take weight in a twisting motion. These will settle and even out with loading and use. Put the wheels on and load it up, remove weight and lift clear of the floor evenly to let the suspension drop evenly and you will prob find panic over. If not just build it and before you know it it will be even! ( I would)

Mini Renegade wrote:If the axle is made the same as torsion axles are over here it has 3 (or 4) lengths of rubber which are designed to take weight in a twisting motion. These will settle and even out with loading and use...

Suspension construction is essentially the same on both sides of the Atlantic: most "rubber torsion" suspensions use the rubber rods (e.g. 4 in Dexter Torflex, 3 in AL-KO), but a few (e.g. Flexiride) use solid rubber formed in place around the torque rod. The adjustable design sold here is the solid-rubber Flexiride; the arm is splined to the torque rod.

While the Flexiride uses a solid rubber cartridge, that block of rubber (square on the outside is apparently installed in a square steel tube (not formed directly in it), so perhaps the rubber is still settling into the tube, as suggested above. I would have expected this to be a pretty tight fit.

The adjustment increments for a Flexiride are six degrees per spline (which means that there are 60 splines). The height change per degree depends on the length of the arm, which in turn depends on the model of components (weight capacity), but for most brands in small sizes this length is 6" or less, so one spline (6 degrees) is about 0.2"... maybe one side is just set a single spline off from the other?

Correction on Edit: the height change for one spline for a 4.5" arm on a 60-spline shaft is 0.47", as correctly shown below by Bruce, not my original value of 0.2".

More information on the Flexiride units. The swing arms are 4.5" from center of spline shaft to center of axle spindle. Six degrees rotation works out to 1/2" (.47") change if the swing arm is in the horizontal position, something less per spline if the arm is up or down from horizontal, but not much.

Looking into the open end of my 1400# half-axles indicates that the torsion shaft is indeed round, not square as in a Dexter axle. The 1400# axles are cut down in length from similar 2000# units and the cut indicates an accurate cross-section of what is going on internally. The rubber is apparently poured (I have no idea how they mold rubber) into the square tube with the axle torsion shaft in place. There appears to be a simple mechanical bond between the shaft and the carrying tube. Think about the bond between the rubber and steel of the engine mounts in your car. Similar.

Bruce

Gene,

I had a similar problem with my Flexride, didn't notice that the arms were at different angles until it was attached to the frame. I think I had to adjust one side by two or three splines to get the arms aligned. It rides just fine now. I assumed it had been assembled early on a Monday or late on a Friday. I wasn't too impressed with SWW's quality assurance.

How can a adjustable axle be a problem? They are not set at assembly to any specific start angle, you set that when installing. I fail to see how that is a problem. You take out one bolt, slide it off the spline and slide it on in a new possition and reinstall one bolt. It takes about a minute to adjust.
Brwbier

Thanks for all the comments and ideas folks. I will definitely continue with my build by putting the wheels and floor on then test it and adjust the axle if needed.

I think I must be setting a record for the slowest build.

I rechecked my calculation, and must have missed a factor of two... indeed Bruce is correct and the per-spline change at horizontal is 0.47" for a 4.5" arm. (The value is the sine of the angle - 6 degrees - times the arm length, or 1/60 of a 4.5" radius circle).

UCF (the Flexiride makers) say that they ship axle assemblies pre-set to a 22 degree down start angle; if someone is sloppy, or the Flexiride licensee who builds the axle (if you get it from someone other than UCF themselves) does not follow this policy, it might come set a different angle, or even different start angles on each side. I agree that if it's just a matter of adjustment, it's no big deal.

If the side-to-side mismatch is a fraction of a spline, then perhaps the rubber was not moulded to the shafts with the shafts in exactly the same position. That could not be fixed by adjustment, but would never be more than a half-spline mismatch, which probably doesn't matter.

Trackstriper wrote:...The rubber is apparently poured (I have no idea how they mold rubber) into the square tube with the axle torsion shaft in place....
Think about the bond between the rubber and steel of the engine mounts in your car. Similar.

Yes, rubber can be made to flow into a mould, until it is transformed to an elastic solid by [urlhttp://en.wikipedia.org/wiki/Vulcanization]vulcanizing[/url] it. UCF pours or extrudes the rubber around the shaft, then vulcanizes it, like those engine mounts... and much like tires.