Dexter axle shock absorber - Page 2 - Fiberglass RV


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Old 05-01-2015, 11:03 AM   #15
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Name: Darral
Trailer: Scamp Standard 13' 2010
Tennessee
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It may be more noticeable on 16' and 19' Scamps. But I simply do not have a problem nor a need for shocks on my Scamp with the torsion axle. This is after nearly 9000 miles. Yes, when I go over railroad or bouncy roads, it bounces some...but so do I in my truck!

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Originally Posted by Borrego Dave View Post
Jim I'm sorry to hear of your thoughts of abuse by members here. From what I've read from members who have installed your shock kits, it has worked out very well for them. I think the video shows the difference in performance perfectly. It does seem that a lot of owners are more into smaller mods/upgrades for personal use than adding something that would let the trailer work easier. I haven't had to many things rearrange themselves during a trip but I am leaning toward adding your shocks to my rig. If for nothing else but to ease the frame jolting and metal fatigue.
Have no idea how many you've sold to Casita owners but despite what some folks have said, I really think the Scamp owners would come through for you if you made them up to fit their rigs. I installed your lift kit on my SD17. The quality/fit and finish were top notch.
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Old 05-22-2015, 08:47 PM   #16
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just a quick follow up - we made some parts for Jim and he got them installed and is now away travelling. When he returns hopefully he will report on how it all worked out


--Jim.
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Old 05-22-2015, 09:26 PM   #17
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and one more follow-up for those of you that dont follow the Casita forums.
We did a bit of data gathering to try to get away from mere anecdotal evidence that shocks work on Torflex axles.
Here is a pertinent picture for your viewing pleasure - this is of course on a Casita with a Dexter #10 axle. Your mileage may vary.
I included all 3 bumps so you dont accuse me of just showing the good one....
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withAndWithoutShocks.jpg  
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Old 05-23-2015, 12:01 AM   #18
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Name: Darral
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I'm lost. I see very little difference between the two charts- one with the shocks and one without.
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Old 05-23-2015, 12:10 AM   #19
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Originally Posted by Darral T. View Post
I'm lost. I see very little difference between the two charts- one with the shocks and one without.
The initial "bang" will always be much the same. Shock absorbers do most of their work on the 'down' part. Compare the final bump of the 3. On the damped version, the up-and-down oscillations die out much faster. The energy has been "absorbed" by the shocks. Trailer settles much quicker.

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Old 05-23-2015, 08:56 AM   #20
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Trailer: Casita 17' 2000 Dodge Dakota 3.9L
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Originally Posted by NedMac View Post

That being said, we do notice our cushions & some equipment becoming displaced inside the camper during travel.
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Originally Posted by Manitoba Jim View Post
We always have a lot of displaced cushions and the like whenever we travel with our Scamp. We are leaving for a 4 week 6000 mile road trip in less than 3 weeks and want to rectify this problem shortly.
I've had a Casita since new and always found cushions on the floor after traveling. I'd be surprised if they stayed in place considering there isn't anything holding them in place.

Am I wrong?

I would also look at my TV suspension parts before the TT's - shock absorbers, sway bar bushings, tire pressure on TV & TT.
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Old 05-23-2015, 09:03 AM   #21
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Name: Dex
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Originally Posted by Darral T. View Post
I'm lost. I see very little difference between the two charts- one with the shocks and one without.
Yes, no difference between the big and small shocks? On the smaller 2 of the 3 parts don't show a difference. The 3rd one does but that just could be a difference in test procedure.

If you look at the chart for the first bump the information looks almost identical with and without shocks - strange.
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Old 05-23-2015, 09:47 PM   #22
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Jump on the bumper of your car/truck & jump off. It will bounce once. Try the same on an old beater with toasted shocks. It will bounce up and down like a basketball for a while. Shocks can only dampen the initial impact slightly & you don't want them to stop it. If they did stop the axle from moving why even have a suspension? They prevent the suspension from continuing to bounce around once its absorbed the impact. It prevents or drastically minimizes aftershocks.

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Old 05-31-2015, 11:02 PM   #23
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Dexter axle shock absorber

Shocks dampen the oscillations of a mass on a spring and in this case the mass is the wheel. On cars this is necessary because if the wheel continues to oscillate after a bump, then the tire spends some time off the ground so not providing steering force or acceleration or braking force. The cost of using shocks is that shock of bumps is transmitted from the road to the car through the shock absorber and the ride is rougher (talk about misnaming a device). Trailer tires are less dependant on braking and not at all dependant on acceleration and do not need the bump forces transmitted from the road. I would not put shocks on a trailer. Just my opinion.


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Old 06-01-2015, 05:31 AM   #24
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Originally Posted by dleverton View Post
.... The cost of using shocks is that shock of bumps is transmitted from the road to the car through the shock absorber and the ride is rougher (talk about misnaming a device). .....
Doug L
With respect - I completely disagree with this notion -and the proof lies in that chart a few posts up. The shock is absolutely NOT transmitted to the trailer. It IS absorbed by the shock absorber and turned into heat. Please look at the waveforms again.

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Old 06-01-2015, 08:03 AM   #25
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Name: JD
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Actually the proper term for shock absorber and as used by the Brits is DAMPER and its purpose is to damp the oscillations on a spring supported system.
The rubber suspension tends to damp the oscillations (turning the excess movement into heat), but the damping is not complete. Ideally the shocks would be smart enough to have variable damping to change their effect for sharp jolts, high displacement regular frequency etc. as necessary and the new, better valved shocks and electronic controlled for cars do this so you get a smooth ride on smooth roads and higher damping for rough roads.
Shocks are valved to have a greater effect on jounce and rebound, since the initial movement needs to be undamped (to some extent) and the rebound is damped. This means that the first part of the bump moves the wheel and the rebound is slowed. The shock valving does this. Shocks are rated as to 50-50, 20-80 etc depending on what the chassis tuner is looking for.
What we are looking for the the carryover oscillations to be damped so that the trailer is not bouncing all over and shaking the contents more than necessary.
AL-KO in the US contends and the other torsion axle manufacturers say that the damping of the rubber is enough for a trailer.. AL-KO Europe adds shocks and the Euro axle is setup to add the shocks to the axle and their trailer frames. Viewing their video shows the usefulness clearly. The benefit is in smoother ride and damping the tendency to sway from side to side.
The enemy of towing a trailer is the tendency of the combiner tow vehicle and trailer to enter into undamped oscillations and the amplitude of such increase instead of being damped and decreasing. Not only do the shock absorbers create a smoother damped ride, but also damp the side to side oscillation from the CG of the trailer being higher than the roll center.
All in all a Win - Win for shock absorbers. Perhaps the fitment of an anti roll bar would complement the suspension of trailers as well for the same reason?
This damping of the oscillations is the reason I think that my VW Sportwagen tows so well. The IRS and the fairly stiff shocks damp the oscillations better than a softly sprung SUV. The result is what is called Dead beat damping where displacement is quickly damped out and swaying is minimized. Shocks on the trailer could only help!
The addition of an anti sway bar to the trailer to TV combination adds the friction damping to help this sway and all it does is change the energy to heat like any other damping system. in the European AL-KO setup the actual coupling has friction pads that are clamped to the ball with a lever to do the same thing and the Hitch balls do not mount with a threaded shaft and nut that would be loosened for this reason.


Since Al-KO basically invented the rubber sprung torsion axle they probably have a fairly good idea as to the best way to operate one as well.
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Old 06-01-2015, 09:20 AM   #26
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Originally Posted by widgetwizard View Post
With respect - I completely disagree with this notion -and the proof lies in that chart a few posts up. The shock is absolutely NOT transmitted to the trailer. It IS absorbed by the shock absorber and turned into heat. Please look at the waveforms again.

--Jim.
The charts are showing that the readings are the same for the largests shocks - they all read between 9.5 to 10 with or without shocks.

In between the largest shocks there the first set does not show much of a difference with or without shocks.

For the last two bumps we don't have a point of reference. We don't know for example if we were riding in the trailer, would we notice if there were shocks or not being used.

With all due respect I think dleverton has some good points.
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Old 06-01-2015, 09:32 AM   #27
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Quote:
Originally Posted by Dextersp1 View Post
....For the last two bumps we don't have a point of reference. ..
Dex,

We absolutely have a point of reference.
No anecdotes here - just data.
This is a "g" meter mounted on the fiberglass of a Casita.
It is showing how much energy the trailer is "seeing"

Jim
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Old 06-01-2015, 09:48 AM   #28
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Looks like an accelerometer using a serial cable to feed Megunolink software. Curious why the Y axis units are called "Bounce" - which is a bit confusing as that indicates to me a distance rather than a force (g-force.)
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