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 Topic: Are shock absorbers worth it
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09/9/2016 at 9:14pm
Location: West Sussex
Outfit: None Entered
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I put dampers on my van having towed it without.
Can I tell the difference? Yes. Just looking in the mirror I can see it is not bouncing around (only noticeable on non motorways). Only on very rough non motorways can I tell by the tow car feedback that the dampers are doing something. 75Kg noseweight is not going to affect the 2000kg car weight much.
for the cost of them, keeping 1500kg from bobbing around on the back of my car is good value.
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09/9/2016 at 9:35pm
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Hello Alex,
I would expect that of you, others don't realize it is not just what you can feel it is the effect it has on the running gear without them - heck lots of drivers don't even know when they have a flat Tyre until someone gives them a toot.
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10/9/2016 at 6:26am
Location: ML9
Outfit: Pageant Champagne 2002 Honda CRV 2008
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Quote: Originally posted by alex on 09/9/2016
I put dampers on my van having towed it without.
Can I tell the difference? Yes. Just looking in the mirror I can see it is not bouncing around (only noticeable on non motorways). Only on very rough non motorways can I tell by the tow car feedback that the dampers are doing something. 75Kg noseweight is not going to affect the 2000kg car weight much.
for the cost of them, keeping 1500kg from bobbing around on the back of my car is good value.
Best answer so far, cheers
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Peter and CofSD (Anne)
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10/9/2016 at 12:34pm
Location: West Midlands
Outfit: Coachman Amara 570 6 + Shogun SG4
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Quote: Originally posted by JohnMW on 08/9/2016
Hi Baileyjake,
I did not want to get to involved in your first part in my last post but I think it needs some clarification. There is a coupling effect that helps reduce yaw in a primary way, however, this is small if you study Simple Harmonic Motion you will note that the pivot in an oscillation is not about the axle center it is about the pivot (ball) so the coupling effect is diminished and reduced to side loads on the two axles. But I commend you for your technical observation. If you can work with calculus you will arrive at more detailed analysis of period rates etc.
Trog I agree totally with your Bulldog leaf accessory it is much better alas still a friction device.
Post last edited on 08/09/2016 21:55:17
It's been a long time since I used calculus to calculate a gradient of a curve or the area under it and writing an expression that that represents the SHM of my caravan would be beyond me.
However what I need to do is increase the resonant frequency of my outfit so that it sways above 60 rather than at 55.
Indeed when towing 300 miles in France this summer I got so fed up with it by the end of the day I increased my speed to 65. But wow do you do that? The hitch stabilizer would do it or moving everything thing into the center of the caravan reducing its moment of inertia.
One possibility is that maybe the caravan tyres are out of balance. I certainly have my doubts about the rear tyres of my car. I had them changed in the spring and the problem seems worse since although it may be in the mind. There doesn't seem to be any vibration etc when solo.
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First van bailey ranger 550/6
Now the proud owner of a coachman amara
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10/9/2016 at 3:46pm
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being old enough to have known a time when wheel balancing on a car was an "extra" i know what out of balance wheels feel like.. in truth i doubt that many younger generation folks do..
it wont come in at all at speeds below 50 mph.. over fifty it starts to come in.. on the front wheels it can be easily felt through the steering wheel.. on the rear wheels it has to be pretty bad before its felt by the driver..
it would not be felt at all by a driver coming from a caravan wheels.. and at speeds of around 60 mph would have to be pretty bad to be a problem..
i think this thread is being over complicated by too many "car" comparisons.. car comparisons dont really apply to trailers..
trog
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10/9/2016 at 8:40pm
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Hi BJ and trog,
You are chasing your tail with trying to move the frequency to suit your needs. I spent months with calculus and sample data from incidents and info from people experiencing sway, trying to pin down a formula that I might use in my design. It is so complex that the variables make it useless to try. Take the simple Harmonic motion and add to it the variables of wind and turbulent vortices that arrive at the extremes of a sway on the side of the van and you can imagine that it could send you out of control in an instant. That is why I needed a control system to ensure the sway never moved out of 3 or 4 degrees before returning under control and was stopped at the center of equilibrium on return by an equal and opposite force - it took me sometime to find how to do this without sensors and motors etc but I have. Trog just because you cannot feel the effect on the running gear does not mean it should be disregarded. Fitting dampers is at the top of my must list on stability.
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