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Trailer Stability

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Tow Itch
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Trailer Stability

Post by Tow Itch on Wed 21 Mar 2012, 5:06 pm

What I always thought was called the pendulum effect is apparently called yaw stability.
Puzzled?
This is why we load heavy things in the middle and don't just put the awning at the back to counteract the weight of the gas bottles and the battery.


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Tow Itch
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Re: Trailer Stability

Post by Tow Itch on Wed 21 Mar 2012, 5:11 pm

AL-KO ATC Trailer Control


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Tow Itch
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Re: Trailer Stability

Post by Tow Itch on Wed 21 Mar 2012, 6:01 pm

Wanted to try and find a video with a Trapezium stabiliser on it as these are quite rare now.
Alas couldn't find one but did find this technical piece in the Sprite club that covered all sorts of facts on stabilisers.
Also mentioned some of the trailer braking systems.

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Nick
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Re: Trailer Stability

Post by Nick on Wed 21 Mar 2012, 6:44 pm

i would like an AL KO hitch stabiliser but they are expensive even 2nd hand then there are numerous model numbers.
The Dandy is pretty stable i would be amazed if anyone could flip a Dandy/Car over through snaking or a blow out,the weight is all low down.
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mike
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Re: Trailer Stability

Post by mike on Sat 24 Mar 2012, 5:11 pm

Whilst a good example the first one failed imo because it only showed the net result of moving all the wieght to the back and front,no explanation was given on what to do with your load in general,you cant just pile stuff up in the middle for a start it would be likely to move when you braked.
Yes as much heavy stuff over the axle as you can but the rest needs evenly distributing over the caravan length making sure it cant slide about,on the six inside you have no option but to load lockers that are behind the axle and then balance this with your load in front of it,so then when it comes to the awning it goes on top over the axle but again you cant just make a heap of stuff in the middle you spread the rest over the dandy evenly.
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Tow Itch
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Re: Trailer Stability

Post by Tow Itch on Sun 25 Mar 2012, 4:43 pm

I can see what your saying Mike. I would counter that as in so many situations there is no perfect answer (well rarely) and it's about the best possible.
I think one thing that is important is clarifying that it isn't just about the balance of the unit and the resultant nose weight, it's also about mass centralisation.
If mass centralisation sounds a bit grand then lessening the pendulum effect or yaw inertia (as Dr Darling calls it).
e.g If the gas cylinder and the battery don't fit on top of the axle we put them nearby and not in the gas locker then balance it with the awning at the other end. At this point we then get into asking should we put the gas cylinder somewhere without easy access?

The more I watch the more bits I don't like about this film:

The two masses. The rear mass is larger and extends further back than the front mass goes forward. I bet this unit had a negative nose weight.

I don't know if it is relevant but there is not one trailer but two in sequence as the car is attached to the table with a bar pivoting at both ends.

Another good piece on stability I found is a PDF that I couldn't get to link elsewhere but appears to work here. [You must be registered and logged in to see this link.]

One of the major factors found in this is the relationship between the distance to the axle from the towball and the entire length of the trailer. This is borne out in practice you can't get a Dart or a Designer to snake and the distance from the tow ball to the axle is two thirds of the total length. A six will snake a Highside Designer certainly will as the tow ball to axle length gets closer to half of the total length.

Look at the film again the axle is only half the total length away from the tow bar.Even the longest caravans don't manage this.

Just found a piece about Dr Darlings report. It isn't the report but is an overview.

Abstract

Previous work on car-trailer stability has been largely limited to theoretical studies with some reference to practical experience or accident statistics. In this study, extensive and systematic experimental investigations were carried out oil a combined car-adjustable-trailer system. The influence of different trailer parameters on the system high-speed stability was examined by changing the mass, dimensions, and inertial characteristics of a fully adjustable trailer. It was found that the dominant factors affecting stability were the trailer yaw inertia, nose mass (mass distribution), and trailer axle position. The tyre pressure also affects the stability, although this effect is less significant. It is interesting to see that the trailer mass alone does not dramatically affect the high-speed stability, as this runs contrary to current guidelines relating to limits on the relative mass of the car and trailer. Experimental tests on a friction stabilizer and on car electronic stability programs demonstrate that both of these improve the high-speed stability and help to delay the onset of 'snaking'. Author Dr J Darling
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Tow Itch
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Re: Trailer Stability

Post by Tow Itch on Sat 14 Apr 2012, 8:56 pm

Knott's Version Of Electronic Stability


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Tow Itch
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Re: Trailer Stability

Post by Tow Itch on Thu 07 Mar 2013, 7:39 pm

There is a report that seems to be missing I don't know If I originally placed it here or elsewhere. Alas I cannot find this now anymore on the sight.
This is a cracking piece on caravan dynamics it's not a light read but it's written in plain language.

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This is a more intelligent than normal forum debate and the author of the above article Collyn Rivers contributes to it.

An updated version of the above It may be easier to read but I think it lacks some of the elegance of the earlier piece.

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Go on get a brew and a butty and have a read priceless education especially for those who tow longer and higher units.

Alas both of these versions of Collyn Rivers piece have disappeared. What we have now  

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Re: Trailer Stability

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