To WDH or not...

[Matty4]

Firstly, let me state that I am a firm believer in the use of a WDH, especially when the towing weight starts getting over the 2000kg mark.

I've read a few posts recently where it has been mentioned on several occassions that some are trying to avoid the use of a WDH,
or would rather not use one, for whatever reason.
I posted this somewhere else a while ago but thought it would be better in the general discussion area.

Please open the attached link and have a read. The more relevent parts to us are on pages 4 - 7.

http://www.caravanandmotorhomebooks.com/pdf/vehicle_dynamics_complete.pdf

I also found this video recently showing how moving weight, not adding it, changes the vehicles stability.

http://www.towingstabilitystudies.co.uk/stability-studies-simulator.php

Food for thought..

Comments??

Cheers,
Matty

 

[Burnsy]

Great video Matty, definately food for thought....thanks for sharing!

Cheers.

 

[chartrock]

You're right Matty, it is food for thought. :nod:

 

[Peter D]

And here I've just made a frame to fit a few jerry cans between the gas bottles! Haven't tested it out on the road yet, so I don't know what effect it's going to have.

Judging by that video the message would be to put any compensatory load near to the other side of the axle(s), and not as far behind the other side of the axle as you can.

P.S. We have a WDH.

 

[ROnEM]

Great links Matty4

The video explains it very simply. For the insomniac I recommend the PDF as good reading!

Both the article and the video are definitely worth reading/viewing as they explain the issue of weight and its distribution in the van as very critical.

 

[Turtle]

Good read and video!
I've often wondered about the change of dymanics when people add a spare wheel, 3 bikes and a jerrycan or 2 to the custom rear bar.
Think i'll leave mine as is (maybe change the bar only).

 

[Billrw136]

Well done Matty .......
I previously posted that second link (to video) - but it would appear that no one looked at it or took it seriously......

Cheers

Bill

Firstly, let me state that I am a firm believer in the use of a WDH, especially when the towing weight starts getting over the 2000kg mark.

I've read a few posts recently where it has been mentioned on several occassions that some are trying to avoid the use of a WDH,
or would rather not use one, for whatever reason.
I posted this somewhere else a while ago but thought it would be better in the general discussion area.

Please open the attached link and have a read. The more relevent parts to us are on pages 4 - 7.

http://www.caravanandmotorhomebooks.com/pdf/vehicle_dynamics_complete.pdf

I also found this video recently showing how moving weight, not adding it, changes the vehicles stability.

http://www.towingstabilitystudies.co.uk/stability-studies-simulator.php

Food for thought..

Comments??

Cheers,
Matty

 

[gspy4u]

I'm still in the undecided camp as well. So far done 5,500klm's without then over rough single lane roads, highways, B-doubles passing and so on and sitting on the speed limit where ever possible and never once had any type of sway or anything to concern about. So still not sure.

 

[Feldty]

Hi Matty4,

Once again thanks for the links. I am glad that I took your advise and that of some others on the forum and organized a WDH for my set up. At the time the cost seemed excessive given that I needed to upgrade the tow bar to fit one, but once paid for, it seems insignificant given the safety implications. I have now had the HR tow bar fitted and have arranged for my Jayco Dealer to fit the WDH upon pick up of the van.

I spent a fair bit of time researching this issue and in all the information I read, not one person had fitted a WDH with ill affects, and almost all had found a benefit from the fitment.

As mentioned in another thread, my van will be by far the heaviest thing I have towed. I am already lacking confidence so any gained stability will be welcome.

Safety first........

Kev

 

[macca]

I was looking at not using a wdh straight away as the BT50 was coming after the van but now we have found a car in stock we dont have that problem. I did not want to buy a hitch for 10 weeks and then find out I had to buy a new one. Does having the extended draw bar make a caravan more stable? I would have thought it did but I am not an engineer.

 

[Matty4]

Some interesting observations.

Today I finished installing my new rear bar with spare wheel carrier.
I decided, after the discussions in this thread about moving weight around, to measure my towball weight both before and after the installation.

I used this method published on the Hayman Reese website..
TW

Tongue weight (TW) is the downward force exerted on the hitch ball by the trailer coupler. In most cases, it is about 10 to 15 percent of GTW. TW of up to 120 kilograms can be measured on a household scale by resting the trailer coupler on the scale and placing the scale on a box so that the coupler is at its normal towing height. The trailer must be fully loaded and level.

For heavier tongue weights, place a household scale and a brick that's as thick as the scale three feet apart as shown in Figure 2. Set a length of pipe on each and rest a beam across the pipes. Re-zero the scale to correct for the weight of the beam and pipe. Securely block the trailer wheels. Rest the trailer jack on the beam as shown, 300mm from the brick and 600mm from the scale.

To obtain the TW, multiply the scale reading by three (3). For greater tongue weights, place the scale and brick 1200mm apart, rest the jack on the beam 900mm from the scale and multiply the scale reading by four (4).

Firstly, disclaimers...
The van is basically empty, there may be a few litres of water left in the tanks, but no food, clothing, bedding etc is in the van.
The gas bottle is full.

On my compliance plate Jayco states an empty ball weight of 122kg empty:shocked:
My van in its standard configuration weighed in with a ball weight of 219kg.
This is just over the 10% "rule of thumb" used previously. Tare is 1879kg. ATM is 2349kg

After fitting new bar and relocating spare tyre the ball weight came in at 162kg.
Now I've only added 19kg overall to the weight of the van, but it's at the furthermost point away from the pivot point (axles).

Fitting a toolbox and relocating some of the heavy items, like the rubber awning matting, into that will give me some back.
We usually take the kids bikes with a rack fitted to the towball to help here as well.

Thought this was an interesting exercise..

Cheers,
Matty

 

[Burnsy]

Thanks for sharing the info Matty, so for another comparison if you only changed the rear bar @ 19kg extra like you said and left your spare on the front (26kg) it would still reduce bw by 31kg.....surprising especially for a dual axle van, I wouldn't of thought it would make that much difference! Maybe it's a progressive ratio?

Cheers.

 

[straydingo]

I was looking at not using a wdh straight away as the BT50 was coming after the van but now we have found a car in stock we dont have that problem. I did not want to buy a hitch for 10 weeks and then find out I had to buy a new one. Does having the extended draw bar make a caravan more stable? I would have thought it did but I am not an engineer.

No it actually makes it less stable as the length of the 'wheel base' (rear car axle to van axle) is increased. This mean the pendulum action from the pivot point is increased also.
However, for 300mm you won't notice the difference.

....and I've still got a HR WDH available.....:whistle:

 

[Feldty]

Hi Matty4,

Some very interesting figures.
I sore the pics of the rear bar on another thread and it looks great.
Have you towed the van with the mod yet, and if so, have you noticed any difference. I am considering the same mod to fit a storage box on the front, but do not want to cause any adverse affects.
I plan to add a box that ways around 25kg to the front that will probably end up with another 25kg of "stuff" added as storage. I'm thinking annex, BBQ and anything else that I cant fit in the tunnel boot.
Given that I will also need to move my gas bottles forward, my thought is that the 50kg on the front should almost counterbalance the 45kg on the rear? Reading some of the info and watching the video that you posted on other threads has made me a little nervous though. Any feedback on your mod would be great. If anyone else has done a similar mod, I would also be interested in any comments in regards to stability.

It might be worth while starting a new thread in regards to Adding a rear bar, stability? Hope I have not hijacked this one too badly.

Kev

 

[ROnEM]

Picked up the 17.56.2OB this morning and with the van on the standard Toyota Land Cruiser towbar with factory suspension, the van was too high at the front. Once the dealer filled it with 160lt of water and the 2 x 9lt gas bottles, this alone lifted the Cruiser's front wheel arch to within 1mm of the recommended limit.

So, had the dealer fit a Hayman Reese 600lb WDH with 30" bars, but had to also buy a very large drop shank to get the tow ball to the correct height. An expensive surprise, but as always - safety first!

This has left a lower clearance as you can see in the pic, but Land Cruiser and van sit nice and level.

Drive home through the hills on the south side of Bendigo with strong winds with no problems! The Tug was running well at 110kmh too and only noticed the van was there on the big hills as the transmission kicked down to try to maintain speed with the cruise control.



Ro

 

[Roh]

Hi Ro,
AAAHHH That new van smell. Looking good. My van sits at about the same height off the ground as yours. I needed the long drop hitch aswell. Seems u have the same problm as i did with the factory fitted chains being too short if you want to cross them over. I found some 2tonne rated Hayman Reese D shackles and used a couple of them to allow me to cross chains over under the hitch But this decreases the clearance again meaning you lose another 50mm or so but on the plus side, if it ever bottoms out it takes a scratch out of the chains and not the new shiny hitch. HAHA
Good luck and hope many adventures are to come.
Rohan

 

[AAJB]

Picked up the 17.56.2OB this morning and with the van on the standard Toyota Land Cruiser towbar with factory suspension, the van was too high at the front. Once the dealer filled it with 160lt of water and the 2 x 9lt gas bottles, this alone lifted the Cruiser's front wheel arch to within 1mm of the recommended limit.

So, had the dealer fit a Hayman Reese 600lb WDH with 30" bars, but had to also buy a very large drop shank to get the tow ball to the correct height. An expensive surprise, but as always - safety first!

This has left a lower clearance as you can see in the pic, but Land Cruiser and van sit nice and level.

Drive home through the hills on the south side of Bendigo with strong winds with no problems! The Tug was running well at 110kmh too and only noticed the van was there on the big hills as the transmission kicked down to try to maintain speed with the cruise control.

View attachment 8946

Ro

just wondering what the ball height is. I pick my 17-56-2 up next week just what the height was.

 

[Pace]

maintain speed with the cruise control.

Cruise control. was told this was a big no no when towing?

 

[ROnEM]

Pace,

Other than big hills where it is better to drop back an extra gear, what is wrong with using cruise control while towing?

My cruiser has 660nm of torque at 1,600 RPM and at 100-110kmh in 6th gear it sits at 1,600 to 1,700 RPM.

Cheers,

Ro

 

[Pace]

Drivers ed course advised against this due to "eyes on the road Rhonda", rather than on the tacho as your foot knows what your feeding your engine. instructor tells. Each to their own of course. I tow no cruise, but personal choice of course. cheers.