WDH...Which One??

[jock]

I've been using a 4 rod 'shepherds crook' system for years. Have found that they work quite well and I've had very little trouble whilst backing up or negotiating spoon drains etc. etc.

The worst thing about them is the difficulty in hitching up...so without going into the whys and wherefores of how to make things easier with my existing unit....Thought I'd spend some hard earned and upgrade........Having said that, I'm a bit taken aback at the variance in price plus the variety of systems available.

I've googled up all sorts of U-beaut units with the stand out being possibly the Andersen system or Fastway....  Bearing in mind that my priority is ease of hitching up to go, would welcome any advice on the best unit to buy.

Jock

[GerryP]

Jock. I swapped out my HR for an Anderon hitch. They work very well and certainly reduce bounce or porpoising better than the bar type.

It's easy to hitch. You just wind up the jockey wheel with the car attached (to take the strain from the chains) and screw up the shackles and let it down. Mo straining whatsoever.

Also, one of most impressive features is the built in friction cone giving you excellent anti sway characteristics.

Further to all that, they are silent (no creaking), are much lighter than the others and don't hang out rearward as far either, which also aids stability.

You don't need to remove for reversing but you still need to either disconnect or loosen the chains off road. Very happy with mine.

[Mick Themungrel]

I agree 100% with Gerry.

[jock]

Thanks for the response Mick & Gerry.....Was hoping to get a few more but I guess that is going to be the problem, for a while, with this new Forum. I say for a while because I'm sure as membership increases we'll get a lot more responses from a much wider range of participants.

Jock

[Mick Themungrel]

Jock I have used 3 different types of WDH. The shepherds crook like you and had no problem with them as I was a lot younger then. The standard HR twin bar system, hated them right from the start, banged and crashed when turning corners etc, bloody dangerous when hooking up and unhooking. I have also used the Ezi lift, very similar to HR except it doesnt bang and crash like the HR.
Changed to the Anderson Hitch in 2016. Below are some posts I made then after travelling for a couple of days. I still stand by the posts now.

24/9/2016
My van is a 25' internal with front kitchen, so the axle are just rear of centre.



I travelled 313k today from Culcairn to Moulamein. The roads varied from good wide smooth bitumen to narrow 2 lane bitumen with pot holes and rough spots. Some sections had been narrow bitumen widened by added a metre to either side of the road surface, leaving a step between the 2 surfaces.

I previously used a Hayman Reese which worked well, but I had found that in wheel tracked bitumen (which is most roads that has heavy truck traffic) and narrow bitumen that had been widened by adding to the edges, the van tended to move around a fair bit, not enough to be a real worry but usually causing me to slow down, it in the end became tiring and I would feel stuffed at the end of the day.

Today on the good smooth bitumen at about 80kph, I tried the kangaroo test and the van just tracked behind with no swing at all. On some sections of the road there is a noticeable join on the centre line, so I drove over it and back a few times, further on the road had been widened , so again I moved around in the lane trying it out. Result was yes I could feel the edges, more in the steering than the van moving around behind me.

Roz commented that the ute was riding smoother as well. I did find on rough surface there was a very abrupt stop to the movement whereas the HR would bounce up and down a bit.


25/9/2016
Today we travelled to Cullulleraine,a distance of 325k. We turned onto the Sturt Hwy way at Ballranald and headed west. The road between Moulamein and Kyalite varies from good bitumen to rough narrow bitumen that has been widened. The Sturt Hwy is the same as always rough in patches but with well-defined wheel tracks (I call them tram tracks).



Had a few trucks overtake me and apart from seeing them in the mirrors there was no difference in the vans behaviour, none of the suck and push away even in a cross wind. The same with trucks going the other way, the normal buffet as the went past but no swing.



Am I pissed off I didnt get one earlier YES. Am I still happy with it YES.



In answer to a comment by GerryP
Gerry I have liked the idea right from when they came out, not withstanding some of the comments on other forums, (bit like the comments about the endless hot water unit that I have). The idea that something with stop sway early instead of waiting for it to start getting out of line. I do wonder how far out before the ESC reacts.

I did look at adding the antisway to the HR but that was more things to attach to the towball bracken and more weight.

[collyn]

There will always be controversy re WDHs as they are a partial solution for a situation that should not exist. Their main minus is that they can address only transfer weight (the down-force on mass caused by gravity) of the trailer's (necessary) tow ball mass. This, by definition, shifts part of that weight from the tow vehicle's rear tyres. The WDH cannot, however, reduce the trailer's yaw forces - that are now imposed on the tow vehicles rear tyres that because of the weight reduction, are now less able to withstand yaw forces. In other words,a WDH inherently reduces the tow vehicle's required margin of understeer. This can be partially (but not fully) corrected by increasing the pressure in the tow vehicles rear tyres.

In essence, a WDH fixes one issue but introduces another.

The only real solution is not to tow a laden caravan that is heavier than the laden tow vehicle and ideally no more than 80% or so of its weight. If that is not feasible accept that a WDH inherently reduces the rig's essential margin of understeer. A jack-knife is inevitable (and non-correctable) if it becomes oversteer - and is very much speed-related. This is particularly when descending a long hill that also has bends.
  
NEVER set up a WDH to 'level the rig'. As a rough guide adjust the WDH such that the front arch of the tow vehicle is about 50 mm higher when the 'van is hitched.

I publish roll-over data elsewhere (and as a matter of possible Claytons' Towing states that virtually all caravan roll-overs they attend are of rigs with WDHs).

Collyn

[GerryP]

I certainly agree that there's a delicate balance when setting up a WDH. Too much tension will transfer too much weigh and reduce the effective rear traction on the car. Conversely, too little tension could leave you with very light steering and reduced front wheel braking capacity.

It is therefore important that your setup is adjusted correctly and as per the WDH manufacturer's instructions.

One of the things I like about the Anderson hitch is that you can attach them with virtually no tension at all and still retain 100% the anti sway friction system. So even if you don't really need it, or your travelling off road, the anti sway is still there doing it's job.

[collyn]

Gerry

Traction is not an issue. It is an issue of relative front/rear slip angles of the tow vehicle. The reduced weight on the rear tow vehicle tyres can result in their slip angle exceeding that of the front tyres's. If that happens the rig will jack-knife.

Front tyre weight is an issue in that (too) affects slip angle - but the effect of nose weight with or without a WDH is readily counteracted by reducing tow vehicle front tyres pressure by about 30 kPa. That was first recommended by the world authority in this issue - Dr Richard Klein - in the 1970s. If you believe high weight is essential for steering you need to warn Harley Davidson that their trike version cannot possibly work!. Consider too that three-trailer 150 tonne road trains are steered by a tug with only a few tonnes on two front steered tyres (yet over 72 unsteered!) at 100 km/h.

A great deal is known about this but most is in full-on mathematics (but backed up with real-life testing). I cannot quote my own work here - but check that of my UK counterpart at caravanchronicles.com. It does not cover the WDH issue (as they are virtually unknown there) but does describe oversteer and understeer in depth. It is run by Simon Barlow and as far as is know we are the only two describing this stuff in relatively plain English. We are often in contact and share some material.


The main issue with dual cam hitches is that in a full-on emergency swerve, the forces are so great that the cams suddenly unlock - instantly feeding the previously locked up energy into the system - when least needed.

In essence most such systems improve stability in rigs up 90-100 km/h - but can be an issue (in emergency situations) above that.

(For those unaware of this I have spent much of my life in this area (and am an ex-Vauxhall/Bedford research engineer).


Collyn


Collyn

[Mick Themungrel]

Aug 3, 2019 12:29:10 GMT 10 collyn said:

Gerry

The main issue with dual cam hitches is that in a full-on emergency swerve, the forces are so great that the cams suddenly unlock - instantly feeding the previously locked up energy into the system - when least needed.

In essence most such systems improve stability in rigs up 90-100 km/h - but can be an issue (in emergency situations) above that.

(For those unaware of this I have spent much of my life in this area (and am an ex-Vauxhall/Bedford research engineer).


Collyn

Collyn, the reason that Gerry and myself and others that use the Anderson Hitch www.titanrv.com.au/weight-distribution-hitch.php is the built in anti sway, which doesnt rely on dual cams or any addon bits and pieces, so there is nothing to unlock and make a bad situation worse . 

[collyn]

Gerry

I should have made it clearer that I was not referring to the Anderson system (that has the benefit of having a self-damping 'spring'). If one must have a WDH its probably the best to go for.

Collyn

[GerryP]

I hear what you're saying Collyn and also understand as I do have an engineering background. I guess I'm guilty of over simplifying but I was trying to get the point across that a badly adjusted WDH, by either too much or too little tension can both have an adverse effect on handling.

Just another point of interest re the Anderson friction setup is that because of its conical shape, the greater the ball weight, the greater the friction applied to the coupling.

[collyn]

Aug 3, 2019 13:48:39 GMT 10 GerryP said:

I hear what you're saying Collyn and also understand as I do have an engineering background. I guess I'm guilty of over simplifying but I was trying to get the point across that a badly adjusted WDH, by either too much or too little tension can both have an adverse effect on handling.

Just another point of interest re the Anderson friction setup is that because of its conical shape, the greater the ball weight, the greater the friction applied to the coupling.

This is an area where an engineering background (or at least an acceptance of Newton's Laws of Motion) helps no end! The basic issue is of course that overhung hitch that introduces a 180 degree 'phase change' with the rig's momentum adding a positive feedback loop.

Re the WDH - there is no setting that actually assists handling in extreme emergency swerves - some make it worse as they extend hitch overhang. 

I am not opposed to the WDH per se - at least while people discount the effects of Newtonian tails wagging Newtonian dogs - but they can never be a plus as such. (They were invented (in Australia) in 1950 by Mr Reese - but then took off initially in the USA. 

Commercial transport used overhung hitch pig trailers until 1920 or so but, as trucks became less slow,  jack-knifing became common at even 20 mph. The Fruehauf company worked that the overhung hitch was the cause (but did not work out why) - and inside two years the industry changed globally to the semi-trailer concept. (If G-D wanted a caravan she'd probably choose a fifth-wheeler!)

Collyn

[jr]

Hi All,
I thought I would just post this link to the Youtube video of how the Anderson WDH works as it shows very clearly the anti sway system, very ingenious.



Naturally those involved in the discussion in this thread are aware of how the Anderson hitch works but there maybe others that have never seen one.


JR

[collyn]

I have no issues with the Anderson WDH as such and the concept of self-adjusting Coulomb friction for the ball and ditto hysteresis for the compressing component is excellent. I feel it is shame, however, that the marketing side of the company in that video shows it 'correcting' an extent of yaw angle and force that, if ever experienced at speed, it would not have a hope in hell of coping with. (In most engineering tests of this, yaw is limited to about five degrees).


The classic example of sheer marketing absurdity in the caravan industry (that seems prone to this (and/or is immune to the more fundamental laws of physics) is where one of the world's WDH makers noted in its PR spin that its product 'moves tow ball mass toward the centre of the tow vehicle'. It confused mass - the amount of matter in something) with weight - the effect of the downforce of the Earth's gravity on mass. Doing as that PR spin claimed would need not a WDH but an angle grinder and welder!

No wonder that some owners become confused re this.

Collyn