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  1. #1
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    Post Bush Caravan Sway

    Morning,

    I have built a new trailer. Everything is complete, now just for the licensing.

    I towed it for the first time. (First time I have towed something this heavy (1600kg) on a Braked Rubber Axle.)
    All went well 100km/h and slower, as soon as I go past (not faster than 110km/h) it starts to sway... A lot..

    It just seems as if the rubber axle is too "soft". Even if the trailer is parked. When I push it side ways on the top, it does not just bounce back.
    The trailer sways for about 5 times until stable agian.

    The coupler down weight is about 60kg. Maybe to light?

    Should i go 2.5t blade springs with a new axle?

    3.2 Ford Ranger Towing Vehicle (2300kg)

    Can provide images if needed

  2. #2
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    Default Re: Bush Caravan Sway

    What design did you use for the trailer? Could it be that the axle is mounted too far forward.
    I once borrowed a home built / designed trailer that had a similar swaying problem. The axle placement had been done on what looked good and was in the middle of the loadbed area. After a bit of convincing the owner moved the axle further to the back of the trailer and the problem was solved.
    All my motorbike and car trailers have had "rubber" type axles and I've not had a problem with any of them.
    The humble person makes room for progress; the arrogant person believes they’re already there.
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  4. #3
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    Default Re: Bush Caravan Sway

    It is all custom built. Didn't work from anything... I don't know what is corrent and what not
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  5. #4
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    Default Re: Bush Caravan Sway

    A rule of thumb is to have the axle 60% behind the foremost part of the box, not including the tongue. Just looking at the pics that axle looks to be further forward than that.
    Stranger

    Lusted for a Landy but the Pajero was sexier and bigger in the right departments, just like my Missus.

    2004 Gen 3. 3.8i petrol V6 (PAJTU)
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  7. #5
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    Default Re: Bush Caravan Sway

    Makes sense.

    Will putting more weight on the axle help?
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  8. #6
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    Default Re: Bush Caravan Sway

    I actually coincidentally came across this page, this morning.

    https://mechanicalelements.com/trailer-axle-position/

    Might help shed some light on your issue.
    RvdM

    2017 Mitsubishi PS 2.5DI-D 4x4 MT
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    PRA

  10. #7
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    Default Re: Bush Caravan Sway

    Well, #####, too late to move it now, right?

    You could try to install shocks either side to try any lessen that sway or pendulum movement.
    That is really where the first problem starts. It should be stable when standing still.
    If it moves more than once and do not return to center, the suspension is too soft a and you could also have way too much weight high up?

    Putting more weight on the nose might make it feel more stable, but only up to a point.

    Please be extremely careful!!!


    2007 Nissan Navara 4L Auto - Worshond


  11. #8
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    Default Re: Bush Caravan Sway

    It does not appear that you are going to be able to move that axle due to the wheel wells. The two things that I would try would be to use a drop plate to lower the nose and to fit a stabilizer.

    Internally I would look to lower anything that would make the COG lower. That spare wheel on the back is not helping, can it go any where else?
    Last edited by Stranger; 2021/06/21 at 10:36 AM.
    Stranger

    Lusted for a Landy but the Pajero was sexier and bigger in the right departments, just like my Missus.

    2004 Gen 3. 3.8i petrol V6 (PAJTU)
    X Factor Bundutop trailer (designed by me)
    1998 Blister Fender Pajero 3500 24V (PAJ) (Sold)
    BMW R1200R

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  13. #9
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    Default Re: Bush Caravan Sway

    Moving the spare wheel to a location in front will help to transfer some weight

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  15. #10
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    Default Re: Bush Caravan Sway

    Tyre air pressure also play a role. I had that on my camper on tar. Pressure was to low and side to side sway emerged.Like a rocking motion.
    Inflated to 2.5 bar and swaying stopped.

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  17. #11
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    Default Re: Bush Caravan Sway

    Bite the bullet now and make a plan to move the axle back by at least 150mm or you will forever have this problem and never be able to tow with peace of mind.

    With the current position you will still have the sway problem even if you were to change to a leaf sprung axle.
    Also with the current position and the heavy spare wheel on the back you have created an awesome pendulum.

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  19. #12
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    Default Re: Bush Caravan Sway

    In my opinion the axel position simply moves the load on the tow bar.

    While there my be a rule of thumb of 60% I will bet that this is probably where you would find that the load on the tow bar is circa 100kg's. Currently 60kg's is way light.

    So before cutting etc. I would suggest that the OP load his van such that there is 100kg's on the tow ball, forgetting the fact that it is impractical to load like this. Pump the tow vehicle tires to 2.5 front and 3.0bar at the rear. For now, pump the trailer tires to 3.0bar and go for a drive. This should immediately tell you if you are identifying the problem.

    I did a similar exercise with a 19' boat trailer that I fitted rubber torsion suspension to. I measured the weight on the ball and then did a fairly complex balance calculation estimating the large masses in the boat and trailer such that I could get 90kg on the ball. Got damn close. The trailer is rock solid but the wheels are way to the rear.

    If your stability is fine with the pressures and loading then load your van as per normal and do some calculations positioning the larger masses on the length of the trailer and you should get close to where you need to move the axel to.

    Sounds like your trailer is currently probably on the limit. As suggested fix once and for all.

    OR.

    Jack the trailer up, remove the tires. Place a bar beneath the chassis, bar resting on tressels and keep moving the bar until you get the desired weight on the tow bar.
    Last edited by Andrew Leigh; 2021/06/21 at 07:19 PM.

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  21. #13
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    Default Re: Bush Caravan Sway

    Tyres 3.0, 75kg on the ball and fit a Tando.
    There is no task too simple for some people to complicate !



    Ford Figo 2016

  22. #14
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    Default Re: Bush Caravan Sway

    Increase the drawbar length.

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  24. #15
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    Default Re: Bush Caravan Sway

    Quote Originally Posted by Erwin Schimper View Post
    Increase the drawbar length.
    This will be easier than moving the axle. The new space above the drawbar can be optimized for a bigger nosecone box and a spare wheel carrier.

  25. #16
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    Default Re: Bush Caravan Sway

    Sjoe, that is a good looking van.

    Lengthening the drawbar will be easier than moving the axle.
    But moving heavy items lower and forward will be easiest.
    Put the spare wheel in front of the nosecone. Move the nosecone latches if needed.
    Any heavy items behind the axle can go forward. Ie water tanks.
    Try to get the nose weight to 100kg and see how it tows then.

    Have you weighed it yet. If it is indeed 1600kg, and the axle is rated for 1600, it will be working very hard, and a 2500 axle won't be a bad idea. However, moving to a leaf sprung axle of the same rating won't matter. Other than that the leaf sprung axle will raise the ride height.

    Lastly, towing that heavy at 110kmh and above is stupid. Slow down.
    You have a very heavy sail behind you. If you want to be able to go that fast to overtake trucks, just remember that the winds around the truck (slipstream and crosswinds) is different and those might cause trailer sway as well.

  26. #17
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    Default Re: Bush Caravan Sway

    Quote Originally Posted by Erwin Schimper View Post
    Increase the drawbar length.
    That should help, even though this reduces the load on the towball.
    Mike Lauterbach

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  28. #18
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    Default Re: Bush Caravan Sway

    Increasing the drawbar length won’t improve weight distribution. It could help longitudinal stability, but I doubt it will help roll.

    Is the trailer nose down? My companion rolled like a big without the dropper plate at anything around 100km/h. Do you have any weight up high? That will make it roll as well. Anti sway bar?

  29. #19
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    Default Re: Bush Caravan Sway

    Thank you for all the feed back. The axle has an 1.8t to 2t rating. So i think it is to soft to start with. I drew up a bracket for air suspension bags. If I can stiffen up the rubber axle, maybe that's the solution with some heavier load in the nose to make the coupler heavier and pump the tyres of the trailer and towing vehicles the correct pressure.
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  30. #20
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    Default Re: Bush Caravan Sway

    I do not think increasing the drawbar length is a wise idea with the current weight distribution. 60kg is already way to light, reducing this further would be problematic.

    I also would not be upgrading the suspension before establishing what the suspension / tow dynamics are. If you have inherent design issues then these should be attended to first in order to get the design functional. Once that is done and you seek to improve a functional design then look at the suspension upgrades.

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