Off road trailer spring mounts

John, I'm trying to send you a PM after becoming a member, but the site won't allow me. Can you PM me?
Thanks,
John

PM sent

If you use SINGLE leaf only it is a disaster waiting to happen eg time bomb and if/when the spring does fracture then axle setup will instantly be the steering system and we will be reading about you in the papers.
I hope not in the obituary column though.
Single leaf and slipper? you can't get much more dangerous than that. May the force be with you.

Older Ford Transit vans had only one leaf and shackle, they worked well but when they broke, goodnight van.
No one with a sound mechanical knowledge would be prepared to tow a trailer with your proposed setup. I definitely wouldn't.
It is not just the trailer but the tow vehicle which also has to be considered, there are usually people in the vehicle while it is travelling and their safety should never be compromised by the towed item.

Many designs of suspension somehow pass Road Authority scrutiny but you wonder how sometimes.

Ross M

What's your qualifications Ross M?

Hello Rod W
The qualies you asked for are:

"A" Grade Automotive Engineer,
Automotive Technician.
Grad Dip App SCI Technology
Automotive Trade Instructor
+ others which aren't applicable to this subject.

So Ross does that mean there is every possibility you know what you're talking about then.

I guess everything has the possibility of failure.

What would you say/opinion on coil springs and their possibility of breaking?

Yes Rod, you are right everything has the possibility of failure it is just some ways minimize the failure rate. A coil set up drops when break occurs but usually doesn't instantly take over the steering.
Leaf springs have interleaf friction which tends to dampen the spring action to some degree. Thankfully they don't often break. Carry a spare leaf if you go that way.
A coil spring generally rides better and is more compliant if something not too heavy is chosen. A coil is just a spiral torsion bar.
I have a T van and while it is ok like all campers, all have pros and cons, it's suspension style is very good. The two point pivoted axle/arm setup is great.
Quality of manufacture could improve somewhat.

You can make your own and incorporate electric brakes just the same.
An engineering shop might be able to help you if your resources don't extend to it.
The coil spring doesn't have any internal friction so they tend to bounce, boing boing, and hammers the tyres back onto the ground more than a leaf does, so shock absorbers are required. A coil can break but you can always carry a spare if.
It depends on the amount of travel required upward and downwards from the running position eg 2/3 up 1/3 down, how long the spring has to be and what height the trailer will be loaded and unloaded.
Spring manufactures can probably be of help here to zero in on your spring selection for your load/travel combination.
Lots of sorting out problems here but it can be done. Just pinch ideas from other designs and best suit them to your requirements.

I will eventually make my own two point arms for my 6x4 and use coils.
You can make a jig out of some rhs which will ensure each of your axles are the same. Remember the forward/rearward setup of the cross arms when doing this though.
As far as welding goes, advice on where to weld is advised. But you couldn't get worse than some professionally built ones. Most manufactures are good but it is in forums like these the failures in newish, well used and second hand used campers suddenly become noticed.
On 4wdaction there is a post from someone who's axle broke going into the mountains near Dargo Vic. Interesting. Has pics too.
Hope this helps un jumble the myriad of possibilities.

Ross M

But what is actually wrong with slipper springs. The issues you raised about short stiff slippers equally apply to short stiff normal springs. If I were to use long soft compliant slippers why would these be worse than long soft compliant normal springs.

No one has actually said what the problem is with the slipper design vs normal design when similar length and compliance is used.

Garry

Garry

My understanding is that if the spring breaks the slipper design will fall apart. Where as spring bolted both sides if it breaks you have a better chance of being able to strap it togethor to get home.

In reality if either springs break and fall apart it will be probably near either end and a temporary fix will be very difficult anyway.


Alan

If you are worried about the slipper action specifically then these are the features I don't like:

1.The slipper is not mechanically secured to the vehicle.

2. The slipper end slaps up and down and is noisey even though some have two spread leaves trying to stop that happening.

3 There is friction in everything but the slipper ends have to be in a high friction sliding action all its life unlike a shackle/greased and mostly sealed, having the sliding action converted to a rotary action in a bush of some sort.

4. If you haven't got military wrap on the front eye end then if the spring eye broke the shackle can't move far and will upset the alignment of the axle greatly, BUT,
the slipper will just force its way back until it steers you into on comong traffic or over the edge. Will you be alert enough and have enough experience to instantly detect this happening and therefore avoid the disaster?????
It isn't very rewarding to see your $50.000 4wd crashed and destroyed and your holiday ruined because of substandard suspension.

5. If you intend to use shockers on the trailer the shock action will be somewhat reduced by the slipper spread leaf feature trying to flex open and shut as the road forces are applied to the shock and suspension.
This flapping flexing doesn't occur with shackles to any worrying degree.

6. As mentioned slippers are a cheap and nasty way of making a suspension.

Thanks for all the comments. It seems to me from the responses that the major issue is that should a main leaf break forward of the axle, having the rear of the spring restrained by a shackle rather than a slipper is likely to be less of an issue safetywise.
It's possible that I overstated the off road aspect, when in reality, all I want is a sturdy trailer for farm use, that can also double as a camper trailer for no more than a gravel road applications. So thanks for taking the time to respond.
John

Ross M's Answer #6 covers everything I could add.
Ozjohn.

Thanks Ross - not trying to be argumentative but trying to understand - my comments against your points.

"Ross M posted:
If you are worried about the slipper action specifically then these are the features I don't like:

1.The slipper is not mechanically secured to the vehicle.

(Is this important as its actions are restricted so mimick as if it secured to the vehicle)

2. The slipper end slaps up and down and is noisey even though some have two spread leaves trying to stop that happening.

(If that is your experience Ok but it has not been my experience - I have had slippers since 1975 and they have been on all my trailers and vans)

3 There is friction in everything but the slipper ends have to be in a high friction sliding action all its life unlike a shackle/greased and mostly sealed, having the sliding action converted to a rotary action in a bush of some sort.

(Don't follow this point - the metal on metal action is relatively friction free once the two surfaced have worn a bit)

4. If you haven't got military wrap on the front eye end then if the spring eye broke the shackle can't move far and will upset the alignment of the axle greatly, BUT,
the slipper will just force its way back until it steers you into on comong traffic or over the edge. Will you be alert enough and have enough experience to instantly detect this happening and therefore avoid the disaster?????
It isn't very rewarding to see your $50.000 4wd crashed and destroyed and your holiday ruined because of substandard suspension.

(I agree completely with military wrap springs but both normal and slippers can come in military wrap springs - the slippers on my box trailer are not military wrap but the slippers on my offroad van are military wrap so your point applies to springs that do not have a military wrap rather than to slipper springs.

5. If you intend to use shockers on the trailer the shock action will be somewhat reduced by the slipper spread leaf feature trying to flex open and shut as the road forces are applied to the shock and suspension.
This flapping flexing doesn't occur with shackles to any worrying degree.

(Why - from the axle (where the shock connects) forward is the same on both type of springs so shocker action is the same - at the back end, in both cases the the end of the spring is moving back and forward with increasing and decreasing shock load. In this regard both slipper and normal springs are acting in the same way - lengthening and shortening as load increases and decreases)

6. As mentioned slippers are a cheap and nasty way of making a suspension.

(I have had heaps of issues with spring mounts and rubbers on my normal springs but never any with the slippers - I agree most slippers are cheap and nasty but so is the $30 shackle spring from supercheap. There is nothing you have said that makes slippers worse than shackle springs when the same parameters are applied to both springs, ie same length, same number of leaves, same mil wrap etc. - the only issue I have been able to find out in all this is that there is a possibility t,hat the slipper can come put of its bracket when reversing. Other than that, based on the evidence put forward in this thread, slippers are as good as shackles assuming the same parameters are used but what seems to be happening is cheap, single wrap, short, tight slippers are being compared with more expensive, mil wrap, long and compliant shackle springs.

I am happy to be convinced otherwise)

Garry