Torsion axle question

[Lou Park]

I've been looking at torsion axles without the center bar.
Just looking at them makes it quite obvious on which direction
you should mount them (spindle toward the back), but what
would happen if someone mounted it with the spindle facing the
front? The reason I ask if a thought I had on lowering a floor
in a trailer for more floor space. So, what would happen?
Lou

[TD Beej]

Nothing good. Any play at all in the axle, hubs, wheels would allow the wheel to turn and at the very least cause excessive wear in the tires, bearings, axle/arm. Worse it could cause the trailing arm to be torn off. This kind of design can be achieved but you need the engineering in it at the start.

Just the way I see it.

Beej

[angib]

Many of the small fiberglass were built with reversed one-piece torsion axles back in the 1970s, so leading arm (ie, arm in front of the torsion rubber) works fine. Dexter recently confirmed to someone who had mounted their new unbraked axle this way round that it would cause no problems.

I can't see any reason why using half-axles changes anything, except that you need to think about how you will set them up - you want to be able to run a straight-edge across the two axle housings to get them perfectly in line with each other, so if there's going to be something in the way, fixing the axles before it's in the way would be good.

One thing to watch out for is mounting leading arm axles with a down start angle - that is, with the spindle in front of and below the torsion rubber. This geometry makes the suspension much less compliant (since most big impacts have a backwards as well as upwards component, such as when running over a brick), so leading arm axles should be used with a zero or even an up start angle.

Andrew

[Lou Park]

My biggest concern is pot holes, unexpected bump, etc. I'm thinking that if one wheel goes into a pot hole, it may want to go to low and hit the other side of the pot hole, therefore making it push the wheel back behind.
Lou

[fourays]

I've been looking at torsion axles without the center bar.
Just looking at them makes it quite obvious on which direction
you should mount them (spindle toward the back), but what
would happen if someone mounted it with the spindle facing the
front? The reason I ask if a thought I had on lowering a floor
in a trailer for more floor space. So, what would happen?
Lou

please don't mount the spindle facing forwards, there is an effect called "castering" that requires the centerline of the wheel to be behind the theoretical contact point of the spindle on the ground. this effect causes the wheel to self center and the trailer will run true. if you don't have castering the trailer will tend to wander around and be unstable whilst towing.

[angib]

if you don't have castering the trailer will tend to wander around and be unstable whilst towing.

Yes, but only if you manage to get the spindles in front of the tow hitch!

I think this post is getting confused with front wheel geometry on four wheel vehicles - which is not at all relevant to trailers.

All those leading arm fiberglass trailers can't be towed? Tell their owners.

Andrew

[fourays]

if you don't have castering the trailer will tend to wander around and be unstable whilst towing.

Yes, but only if you manage to get the spindles in front of the tow hitch!

I think this post is getting confused with front wheel geometry on four wheel vehicles - which is not at all relevant to trailers.

All those leading arm fiberglass trailers can't be towed? Tell their owners.

Andrew

yes the front wheel steering geometry was what I was basing my comments on and I maintain that a leading arm will not be as stable as a trailing arm even with the spindles behind the trailer hitch. the degree to which this instability occurs may or may not be noticeable depending on the rigidity of the arm

[dh]

I can't take credit for this idea, it was passed along to my when I asked about these two piece axles.

Tack weld the two axles together with a scrap piece so they are nice and straight, then they are really easy get lined up and weld to the trailer. Once welded, grind off the tacks.


On the trailing arm, I'm with Andrew (For one thing, he is a lot smarter than me when it comes to phisics and geometry) 0 to an upward start angle, so the push in the bump will push the wheel back. A downward angle, and the axle may climb upward when the wheel hits a pothole.

Applied phisics 101:

Hold a pin in your hand, hold one end with your fingers, let the other end rest on your desktop, now push it into your keyboard, see what happens?

Now, pull the trailing end over your keyboard, ah, it just drags on up there.

Now, hold one end on the desktop, and angle the other end up a bit, about .5" - .75" now go at your keyboard one more time, just kind of rides on up there.

[john]

The 2cv (the little French car) had as its front suspension a reversed trailing arm setup. It was not unstable and the car as a whole was nearly impossible to roll over.(edit:Stolen from the net, and thanks to he who is labeled on the pic)

[asianflava]

I dunno, but you may want to ask the mfg. It may void the warranty, they would be the ones who would know.

[fourays]

The 2cv (the little French car) had as its front suspension a reversed trailing arm setup. It was not unstable and the car as a whole was nearly impossible to roll over.(edit:Stolen from the net, and thanks to he who is labeled on the pic)

I had a couple of those growing up, however the there was a kingpin on the end of the arm that the wheel pivoted on. that put the contact point behind the pivot point leading it to caster.