Motorcycle trailer without springs...

[e9999]

Just got myself another trailer for free essentially. A fella who (se wife) needed the space.
This one is a motorcycle trailer. Looked OK on CList and I wanted a low trailer to make it easy to load the bikes, since my other ones are very high. But when I got there I saw that there were no springs on it. Not missing, designed without it from what I could tell. It seems that it was probably a DIY project, judging from the overkill on steel, odd design in places, and the not so great welds throughout. Maybe the maker thought that the bikes suspensions would be sufficient. But does not seem like a great idea to me. Got it anyway cuz I thought I can always put some springs on it or I can use a bunch of parts from it to make something else.

Anyway, that got me thinking about folks running trailers without springs for bikes. Is that even remotely feasible without big soft tires (definitely not the case here) ? Anybody on MUD running one like that? I suppose in well-kept place with billiard smooth roads without seams, potholes etc, that would be theoretically OK, but this is California, sigh....

Thoughts about the best way to put some sort of suspension on it while keeping it as low as possible?

 

[ntsqd]

I'd look at the various rubber torsion suspensions. Some can either be ordered at a up-swept arm angle or can be indexed to be that way.

 

[e9999]

good point, thanks. Although the frame may be in the way for an upswept system. And to be honest, I have never been very fond of rubber torsion. Somehow, I can't develop much confidence in the system. It's just rubber, right....? But I'll admit I don't know facts about their failure rate. So, will look into it.

 

[ntsqd]

If you listen to AT they fail left, right, and center. Yet there's mysteriously no pictures of any of them post failure. OK, that might be more cynical than deserved, but......

The advantage of this approach for your trailer is that the trailing arm will be outside of and parallel to the trailer's frame. So it would widen the track width a bit, but the suspension bulk can be under the frame while the arm & spindle can be beside it.

Recently here there was a post showing a new mfg making this type of trailer suspension. The appealing aspect of their product was that the arm indexed to the torsion system via a spline and a pinch bolt. Made it easy to set the ride height where you want it or close. The unappealing part is that the whole system is fairly new and doesn't have the rep of the Dexter Torflex axles. I can't recall the name of who it is that makes those.

I think that for rough surface use that these axles need shocks. Without them all of the suspension motion energy is turned into heat in the rubber. Which if extreme enough could cause the de-vulcanization and lead to the failure that AT said happened. For normal pavement use I don't think this is a concern although I'm not opposed to employing them anyway.

 

[e9999]

I was just looking at axleless sprung hubs. Those would be nice, but sheesh, very expensive.

 

[titanpat57]

How about air bags?

If you have to do some welding anyway, maybe a axleless with 4" drop spindles. Trailer may not enough weight to compress the bag much.

 

[e9999]

Yes. In fact, I do have a big Dexter rubber torsion axle I scrounged up. But way too big -at least 3500 lbs, maybe 5000- and a bit bent. Unfortunately, those can't be narrowed down I imagine. But the pivoting spindle ends could be used with some sort of spring or airbag or even one of those polymer pad affairs.

 

[ntsqd]

Not easily they can't be made to freely pivot. The part inside the axle tube is vulcanized to rubber, which in turn is vulcanized to the inside of the tube. At least that is how I think they're made after an extensive investigation of them.

I believe the center of the tube to be hollow, only the ends - say the outer 18"-24" worth, have 'stuff' inside of them.

 

[e9999]

eh, that would be great. I could then remove the center portion and reweld to make it fit my trailer width or use just the ends with the rubber. If it's only 24" that would be good.

 

[ntsqd]

I'd tap on it with a hammer, should be able to tell if it is and where it is and isn't hollow.

 

[e9999]

Yes, that could work. I did have a good look at the axle. I think it's a Dexter Torflex model #10. 3,500 lbs. Interestingly, there is no evidence of the torsion arm retaining system on the outside. It must be all inside. No idea what prevents the torsion arm from separating from the axle tube and it is probably incorporated within the 4 rubber cords system. That makes it not so useful as a source of torsion spindle I could use with a spring as it's not obvious I could just cut a foot or 2 in from the spindle and hope it'll hold together. I guess I could cut in the center of the axle and try to see how far the rubber and center rod bits extend. That's probably safe since they are advertised as independent suspension, so the system likely does not tie over the center. Also, unfortunately, you are not supposed to weld the axle tube (where the rubber rods are located I imagine). Not to mention that 3,500 lbs is too much for a motorcycle trailer anyway, altough it is remotely possible that by cutting the tube in at different lengths the load rating would change.

But if I could find a torsion axle in the correct width and load, that would make life much easier as I can just bolt it down and I can choose the orientation of the torsion arm to keep the deck low. These things are likely not cheap though.

Ironically, if you are wondering about the longevity of the rubber torsion system, Dexter has a video touting its advantages over leaf springs, but if you look carefully at the rubber rods in the video, they show many cracks in the rubber. Saw the same thing in another independent video. Not a good sign maybe.

 

[ntsqd]

The lighter service weight axles are two piece. I have a pair around here somewhere that were for a trailer that never got built. I think they are the lightest offered.

 

[e9999]

Yes, the little stub axles are convenient. Ultra-tow has some 1000lbs (each) stub torsion axles that have only one mounting bracket. Something like $200 a pair. Not too bad. And just bolt it to the frame and done. The heavier ones like the dexter torflex types at 1750 lbs each have 2 mounting surfaces each so you need to built some cross member further in towards the center of the frame.