Suspension on a tradie trailer

Submitted: Friday, Oct 12, 2018 at 09:37
ThreadID: 137331 Views:988 Replies:10 FollowUps:5
Hi, I have a fairly standard tradie trailer in fair to good condition, it has 14’’ falcon wheels which I will try to fit a set of ranger wheels that match the ford ranger tow vehicle I have. I’m looking at do the red bash next year then continuing onto king canyon Uluru and a couple of other places over a 3 to 4 weeks. I intend to mount the roof top tent, carry extra fuel and a majority of the camp gear in the trailer... probably up around 750 kg all up.

My issue is the standard slipper spring. Should I

1.upgrade to spring that are secured at each end. Concern is how strong the attachment point will need to be .

2. Stick with the slippers but beef them up. Easier to replace and possibly less damage to the trailers hard attachment points

3. Should I look into a shocker and leaf spring combo.

4.something else u can suggest.

I’m currently researching how to get from Birdsville to Alice Springs via more direct routes that being said the reason for doing this trailer up is do a little more bush camping where our cvan can’t get to also a hell of a lot cheaper to do quick trips in.

Any suggestions would be appreciated
Cheers John

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Reply By: Shaker - Friday, Oct 12, 2018 at 09:45

Friday, Oct 12, 2018 at 09:45
You might be able to save yourself a lot of time, money & possible disappointment by considering something like this top of the range camping trailer. TRACK OASIS LINK
I went away with somebody that had done what you are planning & whilst the suspension survived almost everything else didn’t, there is far more to a good off road trailer than good suspension. My friend found that out the hard way & had to part with plenty of his hard earned cash for repairs at Innamincka!

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AnswerID: 621532

Reply By: qldcamper - Friday, Oct 12, 2018 at 09:56

Friday, Oct 12, 2018 at 09:56
It will be the front spring mounts that might need strengthening no matter what sort of spring you go with.

I bought a near new semi offroad 7*4 and i got rid of the silent slipper springs and put in greaseable shackle springs with the offroad dampener that is supposed to do a similar thing to a shock absorber. The front mount that come with the kit is far stronger than the original. It is 1350Kg rated suspension so a bit bouncy unless fully loaded but reducing the tyre pressure to 20 pounds settles it down a lot and the tyres still run cooler than those on the car on the bitumen and corrugations.

I would recomend that you put some serious thought into fitting brakes to it even though rego doesnt require them, you will be happy you did if your towing 750 kg on dirt where there are animals hopping around.

Look at the huntsman site for some ideas.
AnswerID: 621533

Follow Up By: qldcamper - Friday, Oct 12, 2018 at 10:13

Friday, Oct 12, 2018 at 10:13
Another thing you need to do is protect the wiring, where it is now isnt much good. it will not be there after your first day on gravel roads. The spare on my trailer is in the same spot of yours ( wont be next trip ) and it has bounced hundreds of stones into the tailgate of the ute, peppered with stone chips. After 6 weeks around the SA deserts there wasnt any paint on the front of the trailer except where protected by the tyre and tool box and there are a few dents that would take a big hammer to duplicate on the jerry can holders, luckily i didnt have any jerrys in them or they would have been destroyed.

There are two words that i will recomend, STONE STOMPER.
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FollowupID: 894087

Reply By: RMD - Friday, Oct 12, 2018 at 11:12

Friday, Oct 12, 2018 at 11:12
John
If carrying a load that round axle will have to go, it won't withstand much off road use and the bearings are too small for fitting larger wheels which have more leverage and angular force induced when cornering.
The springs are short and sudden non compliant items which will transfer sudden forces to the trailer body and contents. For life and durability it is best to change them.
Longer, eye each end type springs/rear shackle, will be far more compliant of rough roads and the trailer will not bounce. That will be enhanced by fitting shocks to the axle so it absorbs. I used HJ60 landcruiser front leaves, some leaves removed, with shocks set at an angle. Someone recently said shocks can't be more than 30 off vertical. Mine, for fitting reasons, are around 40 degree from the horizontal and work very well in controlling the 50mm sq axle. The axle moves rearward during spring flex so shocks are mounted behind the axle to the bodywork. Still with 14' wheels though.
PS Landcruiser springs have military wrap of second leaf over the front eye and so is more secure if the main leaf ever breaks, instead of the axle suddenly wanting to leave the trailer, not nice with cheap poorly designed springs.
LC springs also have a larger front and rear eyee than trailer springs and use larger pins and bigger bushes which also absorb shock. Stronger front and rear mounts are required too. Spring hangers made sensibly provide a longer patch of area and weld opportunities to the minimal frame and so spreads the load over a wider area, further lessening any possible failures.
While some trailers are ok, some are not, and require some additional plating or continuation of A frame structure to ensure the forces are taken through sufficient RHS to vital components instead of through some sheet metal areas as many trailers are designed.
AnswerID: 621539

Reply By: Member - nick b boab - Friday, Oct 12, 2018 at 12:36

Friday, Oct 12, 2018 at 12:36
If you're looking at doing Outback travel and off road camping you can find plenty of good soft floor campers fairly cheap second hand and I'm sure the outcome would be a lot better than trying to get this trailer ready for such Adventures
Cheers Nickb

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AnswerID: 621541

Reply By: Frank P (NSW) - Friday, Oct 12, 2018 at 15:10

Friday, Oct 12, 2018 at 15:10
John,

Just looking at those pics, IMO the trailer is not really strong enough to do anything but sealed roads and smooth dirt. It's too lightly built and I think if you strengthen some part of it to accommodate better suspension for touring, that will just transfer or impose loads to another part not designed to take them.

I could be wrong and I won't be offended if anyone offers a different opinion!

Cheers

AnswerID: 621547

Follow Up By: Shaker - Friday, Oct 12, 2018 at 16:35

Friday, Oct 12, 2018 at 16:35
They were my thoughts too, as I said earlier my mate found that out the hard way.
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Follow Up By: Ron N - Saturday, Oct 13, 2018 at 00:11

Saturday, Oct 13, 2018 at 00:11
Franks right on the mark - that trailer shouldn't ever leave the outer suburbs of the city.

It's designed only for bitumen and it's built for a low price - not for heavy work on rough roads - using the cheapest components and materials available.

Slipper springs are the cheapest and nastiest suspension available off the shelf, and the suspension is a good pointer to the cheapness of the trailer design overall.

Cheers, Ron.
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FollowupID: 894095

Reply By: Greg J1 - Friday, Oct 12, 2018 at 16:59

Friday, Oct 12, 2018 at 16:59
Mate. I think the suspension is the least your worries with that trailer.

Sure it would be ok for a quick weekend trip somewhere, definitely not something I would be comfortable towing out bush for 3 to 4 weeks.

If you think I’m being harsh you only have to see how many GOOD trailers you see abandoned in the outback. Left there as though it just a piece of litter beside the track.

Cheers Greg.
AnswerID: 621548

Reply By: Hoyks - Friday, Oct 12, 2018 at 19:47

Friday, Oct 12, 2018 at 19:47
It might survive provided you drive it with a lot of mechanical empathy, but I agree with the guys above, you would probably have to do a bit of work to it to make it bush ready and not have it shake its self to bits.

Flipping it over and beefing up the draw bar so it meets the front suspension mounts, installing new springs, new spring mounts, new wheels, new axle etc.
You are basically up for building a new chassis and dropping the box on top which is going to be a few $$ and a fair bit of work.

Personally, I'd seriously look at a Ex Army TRAILER, LIGHTWEIGHT, CARGO, 750 KG (HAULMARK), MC2.
They are going for around the $1000 mark, are are tough as nails and all you really need to do is fit a new hitch and re-wire the plug.

https://www.australianfrontlinemachinery.com.au/vehicle-types/trailers
AnswerID: 621550

Reply By: splits - Saturday, Oct 13, 2018 at 10:43

Saturday, Oct 13, 2018 at 10:43
I agree with the others who have said the trailer looks too lightly constructed for Outback roads. The easiest way around it would be to remove the box and put it on a more conventional trailer chassis. You may get some good ideas from this one.
TRAILER PLANS

I noticed he has used four shocks after finding two were not good enough. They are on a steeper angle than they should be and so are many on camper trailers and caravans. Maybe that is why so many of them also have four.

Note the way he has mounted the springs. He mentions "axle steer" . Car axles change angles as they move up and down. They swing in an arc around the front shackle bolt. Suspensions with coil springs and linkages do the same thing. Trailers with their short high arc leaf springs mounted at the same height each end under a flat chassis should be in the history books. The path taken by the axle as it moves up and down is the complete opposite to car axles and this does adversely affect stability.

This link shows you where he has taken it.MAP There are thousands of ks of dirt roads on that map but there is no very rough ones like the Canning Stock Route, Gunbarrel Hwy, Anne Beadell Hwy, Sandy Blight Junction Road and the Connie Sue Hwy but I doubt if that trailer would have any trouble handling them.

AnswerID: 621552

Follow Up By: RMD - Saturday, Oct 13, 2018 at 13:45

Saturday, Oct 13, 2018 at 13:45
I like his theory in using lower front hanger and note he is using flat springs. That minimizes bump steer as the axle isn't being made to move much for/aft.
With long flat leaf springs he has reduced the shocks and made the suspension compliant. You can have a lighter frame if the hammering isn't being delivered to the body. Pajero vehicles are sheet metal, no chassis, but sound design suspension.

Trailer pics.
The action of a link suspension at the rear and the path of leaf spung axle is similar. The side under movement moves the axle rearward on that side. I don't think the wheel path is the exact opposite.
Some link suspensions have the arms positioned in a manner which reduces the overall effect because the pivots are made lower than can be achieved with a trailer. Ground clearance dictates much of that.

Looking at the trailer plans and see he has two shocks fitted per side. For the weight he is carrying two has to be used to see noticeable control.
If the lower pivots were positioned further out and the shocks mounted from axle to side frame, any axle movement would cause more shock stroke and more control with just one shock.

The two per side as pictured, are positioned so they cause more stress on the mounts. He isn't using the "principle of levers" much at all. If a wheel moves upward over a bump, the shock positioned that way receive far less movement at the mounting points and so are limited in their control. Most 4wd and cars don't mount shocks like that because of the lessening of effect.
Angle mounted shocks like those shown are generally used where a high degree of articulation is required, ie, 500mm travel per side and for that you can't use shocks mounted where they provide most control. Just add more shock numbers is the only option.
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FollowupID: 894105

Follow Up By: splits - Saturday, Oct 13, 2018 at 21:14

Saturday, Oct 13, 2018 at 21:14
The action of a link suspension at the rear and the path of leaf spung axle is similar. The side under movement moves the axle rearward on that side. I don't think the wheel path is the exact opposite.
------------------------------------------------------------
I think you will find it is the opposite . It is part of the "roll understeer" feature of the design.

A fully loaded leaf spring in a car is usually flat or very close to it. The front eye is now down around axle height or lower. As the car leans onto it in corners, the axle moves up and forward. A conventional high arc trailer spring with each end mounted at the same height under a flat chassis will flatten when one wheel rises or the trailer/caravan leans onto it in a corner. This will push the axle back creating roll oversteer which is not desirable. It is explained here in the second paragraph.ROLL STEER

There is another explanation here but it is on a different design. The middle illustration is the one that was commonly used by many manufacturers.
ROLL UNDERSTEER

Some of this axle movement will depend on movement in the spring's rubber bushes. This is part of the " compliance steer" feature of the design.COMPLIANCE STEER In the third paragraph it mentions car suspension designers "tuning" the rubber bushes as part of the whole design.

It is not hard to reverse all of this, particularly when people fully load a car or get a GVM upgrade then lift up it up on an aftermarket suspension when the car has been designed to be down when loaded.
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FollowupID: 894110

Reply By: GarryR - Saturday, Oct 13, 2018 at 17:06

Saturday, Oct 13, 2018 at 17:06
Unload those slipper springs as they will give you grief. I have several trailers and 2 have slipper springs and both have had spring dislodge from the retaining cradle. This use due to the rough road the boys tow these trailers on to and from job sights. The other trailers are tandem with rocker spring and hve never given any trouble. If you wish to stay with the single axle, I would place eye to eye with greaseable shackle on the rear and beef up the front hanger and replace the bushes. Use new bolts and a nyloc nut with a springwasher and it will not come loose. this is what I have done to all the trailers now
location - Warragul -Victoria
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AnswerID: 621554

Reply By: swampy - Sunday, Oct 14, 2018 at 17:31

Sunday, Oct 14, 2018 at 17:31
HI
The 1st and 2 nd photo tell a story
Looks like angle steel main frame
Looks like Z or top hat section floor support rail [ left to right ]
Positive its a RHS draw bar


Need at least falcon bearing axle 45mmsq beam
Slippers Springs for the weekender fine but for unlimited miles longer bushing supported springs needed .
AnswerID: 621573

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