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Old 06-01-2015, 10:31 PM   #41
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Name: Doug
Trailer: Trillium
California
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Dexter axle shock absorber

The trailing arm type suspension on Bolers and Trillium's are simple but have a weak point. The tires camber angle is always equal to the trailers roll. As a result if you let the trailer roll excessively you also get excessive camber and the lateral adhesion of the tires decrease. So if you take a corner way too hot, it is easy for the trailer to slide. This is why "caravan racing" has had some popularity in the UK. There are lots of things that can promote oversteer and a sliding trailer is one of them. So an anti sway bar would both limit roll on corners and so help keep the dishes from falling, and would reduce the tendency to oversteer. Boring, but safer.
On the other hand there may not be much roll to suppress. Roll when cornering is caused by centripetal force acting on the center of gravity of the trailer. If the center of gravity is above the roll center the trailer will roll outward, but if the center of gravity is below the roll center the trailer will roll inward. If the two centres coincide there will be no roll. I think the roll center on trailing link is the center of the axil, but I am not sure. There is an algorithm to find roll center for every configuration of suspension to be found on the Internet, but I couldn't find it for trailing link. Probably there is no algorithm because on cars, straight trailing link has not been used for many decades. I found one reference that claimed that with trailing link it is easy for the suspension designer to set the roll center where he likes (no mention of how). If that is true, it explains why it is used on trailers as roll can be set as desired (minimal or zero), and the expense of an anti sway bar is not needed. When I took the dogs out tonight I rocked the Trillium and tried to eyeball the roll center. It is low, somewhere between a foot and two foot above the ground, and the center of gravity is also low. I'm kind of keen to see how much roll I get on a traffic circle next time I take it out.
OK I'm babbling, but it is an interesting topic.

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Old 06-02-2015, 12:37 AM   #42
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Name: Doug
Trailer: Trillium
California
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Dexter axle shock absorber

The trailing arm type suspension on Bolers and Trillium's are simple but have a weak point. The tires camber angle is always equal to the trailers roll. As a result if you let the trailer roll excessively you also get excessive camber and the lateral adhesion of the tires decrease. So if you take a corner way too hot, it is easy for the trailer to slide. This is why "caravan racing" has had some popularity in the UK. There are lots of things that can promote oversteer and a sliding trailer is one of them. So an anti sway bar would both limit roll on corners and so help keep the dishes from falling, and would reduce the tendency to oversteer. Boring, but safer.
On the other hand there may not be much roll to suppress. Roll when cornering is caused by centripetal force acting on the center of gravity of the trailer. If the center of gravity is above the roll center the trailer will roll outward, but if the center of gravity is below the roll center the trailer will roll inward. If the two centres coincide there will be no roll. I think the roll center on trailing link is the center of the axil, but I am not sure. There is an algorithm to find roll center for every configuration of suspension to be found on the Internet, but I couldn't find it for trailing link. Probably there is no algorithm because on cars, straight trailing link has not been used for many decades. I found one reference that claimed that with trailing link it is easy for the suspension designer to set the roll center where he likes (no mention of how). If that is true, it explains why it is used on trailers as roll can be set as desired (minimal or zero), and the expense of an anti sway bar is not needed. When I took the dogs out tonight I rocked the Trillium and tried to eyeball the roll center. It is low, somewhere between a foot and two foot above the ground, and the center of gravity is also low. I'm kind of keen to see how much roll I get on a traffic circle next time I take it out.
OK I'm babbling, but it is an interesting topic.

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Doug L





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Old 06-02-2015, 12:39 AM   #43
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I did find an interesting reference. http://caravanandmotorhomebooks.com/caravan-dynamics/
They put the roll center just about ground level.


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Old 06-02-2015, 02:53 AM   #44
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Trailer: Casita SD17 2006 "Missing Link"
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This has been interesting reading all the comments and posts of g, y or whatever forces are in some tests by whoever to show shock dampening from some folks. I know that you all realize that you can find statistics to prove anything you want. If you're an engineer in the field I can understand your comments and stats, that's how your mind works. But, and I'm sure I'll take some hits for this. I think most of the molded trailer crowd here is old enough to remember when our cars/trucks had just plain shocks. No electronic gismos and controls. Remember when the shocks wore out and the car bounced down the road for a while after a dip or bump? Wonder what that would look like on a graph in comparison? Bottom line, adding shocks to a trailer really looks like it helps and it certainly can't hurt the ride. There have been a few members that have added them and are very happy with the results. Guess I'm old school, I can look at graphs but I'll always take real world user experiences first.
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Old 06-02-2015, 06:42 AM   #45
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Name: JD
Trailer: Scamp 16 Modified (BIGLY)
Florida
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Interesting mention of roll center since the coupling between the trailer and TV and their roll centers have a large effect on the stability of the total system.
On my VW station wagon the IRS has a pretty low roll center and negative camber. It also has a rear anti-roll bar standard. With the stiffer, more highly damped rear end the trailer -TV combination works quite well and as to stability if you sharply displace the steering wheel the combination reacts and also damps out ant oscillation very quickly!
I am currently rebuilding the '86 Scamp 16 footer and changing the axle for one that has some suspension travel left. I have chosen the Flexiride since I can change the ride height ans since I had to buy new wheels anyway (no 4 lug hubs with brakes available) I went to 14" wheels and 205 75 14 tires which are taller and therefore have (perhaps) more sidewall.
I am working to keep the CG low and the trailer balanced as I build to retain as much or the good handling as possible.
I would like to have shocks for this setup. but I don't think that the orbital system will fit. As a result I am looking into importing a set of the AL-KO octagon shocks and welding the necessary brackets to the trailing arms.

http://www.al-ko.co.uk/edit/files/do...chure-2012.pdf

Since AL-KO is the originator of the rubber suspended torsion shock I assume that they know a little about whether or not they need additional damping!
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Old 06-02-2015, 09:31 AM   #46
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Borrego Dave
In the end, we do this for the pleasure of it and we should each do what is the most satisfying. As with most complex systems the answers are never clear cut, situations vary and personal preference varies.


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Old 06-03-2015, 05:57 PM   #47
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Name: J
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Quote:
Originally Posted by redbarron55 View Post
I am currently rebuilding the '86 Scamp 16 footer and changing the axle for one that has some suspension travel left. I have chosen the Flexiride since I can change the ride height ans since I had to buy new wheels anyway (no 4 lug hubs with brakes available) I went to 14" wheels and 205 75 14 tires which are taller and therefore have (perhaps) more sidewall.
I am working to keep the CG low and the trailer balanced as I build to retain as much or the good handling as possible.
I would like to have shocks for this setup. but I don't think that the orbital system will fit. As a result I am looking into importing a set of the AL-KO octagon shocks and welding the necessary brackets to the trailing arms.

Since AL-KO is the originator of the rubber suspended torsion shock I assume that they know a little about whether or not they need additional damping!
Sounds like an interesting and fun project. Keep us updated with any progress.

Jim
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