Draw Bar lengthening

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    Posted: 26 Jul 2021 at 8:12pm
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I'm wanting to lengthen my draw bar by approx 250mm (Aluminum Trailer). Main reason is so I can open the rear door of my van without having to unhitch.
Wanting to know if this would change the towing dynamics for the worst, if at all?



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Post Options Post Options   Likes (1) Likes(1)   Quote reel crayze Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jul 2021 at 8:17pm
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We looked at doing this for a caravan . I was told by local tow bar manufacturer that it affects your towbar rating if you make the drawbar longer. I never checked out if what he said was correct but i trusted him as these people have been manufacturing tow bars for many years. 
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Post Options Post Options   Likes (0) Likes(0)   Quote Schampy Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jul 2021 at 9:48pm
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Got Andrew from FBNZ to add 600mm to drawbar from new on my old 575.
No probs at all. Just did it to help with beach launching.
Sometimes was a bit of a hassle at a tight gas servo forecourt  because it did make the whole rig quite long. Towed sweet.

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Yes will effect the draw bar rating.. IF the trailer is under built in the 1st place...Even on a caravan, a large caravan it is not applicable.

Wanting to know if this would change the towing dynamics for the worst, if at all?

 Yes. and you will like it...Wink
 There are 3 main area that effects towing, espec reversing.
 1/ The distance from the ball to center of the tow vehicle rear axle.. longer the better
2/ The triangle between the hitch, and trailer wheels, and distance between those wheels..
Which in this case is the distancde from the trailer axle to the hitch.
 A short distance makes reversing very touchy and will jack knife real fast and easy... longer  Thumbs Up

A short distance often means  more weight behind the  trailer axles which if to light on the ball , under braking, slowing down in a cnr, espec down hill have a tendency to snake.. shorter distance the harder to bring under control.
 Longer distance adds a bit of weight, espec if its the axle thats moved back
 Notice how most boat trailers have the axles further back to compensate for the engine weight on the rear?  espec single axle.

 Look at possibly moving the axles and guards back.. thu 250mm looks to be a bit too far...
If go adding the 250mm   re check the weight on the ball.
How To:
 with Bathroom scales.
 Put trailer on the ball, level ground.
Measure distance from the ground to the bottom of the trailer hitch where drops over the ball.
Get the bathroom scales, put under the hitch measure from top to the bottom of the hitch. Cut a bit of 4 X3 or whatever that length.
Now weigh the hitch, boat loaded normally on the 3X2 and scales...
 Very important to be same height was ball when hooked up.

Weight can be changed by moving load distrubution in the boat/ trailer or by changing the tow ball height.

Single or duel axle..
 Small boat like that should be around 75/ 85 kg
 A larger say 5.5m cabin  85/95kg.

 And for those others who may read this in the future

 If duel axle.. lowering the ball is very likely remove required weight.. even a 30mm change in ball height down can go from 65 kg down to 12/15kg.
So be careful changing tow vehicles.
 We had serious  snake issue, normal towing forward, starting anything over 65 km/hr going from the big horn to the ssangyoug. The big horn ball was 38mm higher and perfect.. The SSangyoug is now 35mm higher and perfect to 110km/hr.

 Hope this and the explanations help your understanding what is happening with these changes.


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I had the same problem with my Suzuki Grand Vitara which has a side opening rear door, your van I assume lifts up? Anyway my trailer is a Fi-glass which had an adjustable winch mount to the drawbar (U-bolted on). I moved the whole boat back about 2" and that solved it. Didn't make any noticeable difference to the towing characteristics. Can't quite see on your pic, is it adjustable? Maybe you could do that? Cheers.
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Post Options Post Options   Likes (1) Likes(1)   Quote Big -Dave Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jul 2021 at 1:57pm
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Sorry, but the length of a drawbar can affect the towbar rating?, dosent make sense to me.
The towbar is on the vehicle. The drawbar is on the trailer.
My eperience has been, that the longer a drawbar, the better the trailer was to tow, provided that the drabar was rigid enough.
Yes, adding 250 mm will affect the downforce on the tow ball, but ever so slight and not useful to factor in. The towing dynamics will only improve, but again , for such a small change, it won't be noticeable.
you can't fix an idiot with duct tape, but it does muffle them for a while...
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BNT ask for a new coupling TE4C600Z same bolt pattern problem fixed,Toyota hiace suffer same problem.
Trick to holding coupling open, pull open and put safety chain between button and handle put on ball and pull chain out and will lock down.
Multi fit couplings
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My boat trailer has a massively long drawbar, tows amazing, only thing you need to do is ensure there isn't a huge amount of additional weight on your draw bar. Most axles can be moved easily. Or put more weigh in the rear of the boat when towing. Its more dangerous to have too much weight at the back than at the front, but if your drawbar is loaded up your braking and tow car stability may be worse.

best example is this

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Originally posted by Big -Dave Big -Dave wrote:

Sorry, but the length of a drawbar can affect the towbar rating?, dosent make sense to me.
The towbar is on the vehicle. The drawbar is on the trailer.
My eperience has been, that the longer a drawbar, the better the trailer was to tow, provided that the drabar was rigid enough.
Yes, adding 250 mm will affect the downforce on the tow ball, but ever so slight and not useful to factor in. The towing dynamics will only improve, but again , for such a small change, it won't be noticeable.

Ok i might have my terminology wrong, my apologies. My towbar is made by Blackwells in ChCh. I went in there and asked if i lengthened the bit of metal that connects my truck to the towball assembly will this affect anything. The boss man says yes it will it will decrease the rating that this assembly currently has..
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Loadmaster - Towbars, bullbars, load lids and decks


My towbar is set up exactly like picture 11 , [row 3 photo picture 3] .

The bit i wanted to lengthen is the box bit of steel that has the pin in it.  It is welded to the flat bit that the towball is connected to , that would of given me a greater distance from my caravan to the deck of my truck. Lengthening that the owner says would downgrade my rating.

Sorry for the confusion, my bad.
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Post Options Post Options   Likes (0) Likes(0)   Quote Big -Dave Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jul 2021 at 9:59pm
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Ahh, yeah, modifying the towbar is not a great idea.
I assumed your issue was the rear door hitting the boat, but is it hitting the coupling?
If so, a different style of coupling would suffice as pointed out.
Plus a towbar sticking out that far would be murder on shins....
you can't fix an idiot with duct tape, but it does muffle them for a while...
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I believe any welding or change on the tow ball, tow ball tongue or the tow bar requires certified welders and certification.
Same as any welding on chassis suspension parts.. even then on certain suspension parts its just not allowed.

The ball tongue is the part in question.
 Fortunately these are std box section sizes and interchangeable.

When the tow bar assembly was installed the correct tongue should have be installed to have the rear door clear it.
If that crowd did it then they should simply change it.. maybe u just asked the wrong question??
Rather than modify question asked replace with the correct one for the model?
Often ppl who have messed up in stuff like this try to get away with it by not correcting the question of the customer asking..Wink

Anyway places like super cheap/ repco /trogen/ bars all have these on the shelves.. about $70 to $100 from memory.
You can go in then simply try which one works.
 Keep in mind changing the ball height changes the weight on the draw bar...If anything , being single axle it will increase weight a little  most likely improve towing slightly
. Check you weight anyway.

There is another alternative thu... cutting wheel on the grinder and cut a U in the bottom of the door... If cuts out the door catch a bungy will suffice till next WoF Wink
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Post Options Post Options   Likes (0) Likes(0)   Quote Titahi Quote  Post ReplyReply Direct Link To This Post Posted: 28 Jul 2021 at 10:39am
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Originally posted by Steps Steps wrote:

 


 Keep in mind changing the ball height changes the weight on the draw bar...

I cant for the life of me figure out how raising or lowering the tow ball height changes the draw bar weight? Its essentially a fulcrum and the weight remains constant throughout an arc..... 

If your lucky youll have a reece hayman type hitch, and can buy several different tow ball tounges with differing height offsets.

"I love standing by the ocean and just knowing what its for"
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Originally posted by Titahi Titahi wrote:

Originally posted by Steps Steps wrote:

 


 Keep in mind changing the ball height changes the weight on the draw bar...


I cant for the life of me figure out how raising or lowering the tow ball height changes the draw bar weight? Its essentially a fulcrum and the weight remains constant throughout an arc..... 

If your lucky youll have a reece hayman type hitch, and can buy several different tow ball tounges with differing height offsets.

only time weight would change would be done by moving axle??
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I cant for the life of me figure out how raising or lowering the tow ball height changes the draw bar weight? Its essentially a fulcrum and the weight remains constant throughout an arc.

 Yep.. I still had our duel axle on the mind
 Thu We cant assume it has actually had the ball weight set...maybe 'balanced' so when not hitched and jockey wheel folded up, the hitch is low and needs lifting up onto the ball going from 'neutral' weight to loaded... or set so hitch is high at neutral/ unhitched then needs pulling down.
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Post Options Post Options   Likes (1) Likes(1)   Quote Titahi Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2021 at 4:46pm
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Originally posted by Pcj Pcj wrote:

Originally posted by Titahi Titahi wrote:

Originally posted by Steps Steps wrote:

 


 Keep in mind changing the ball height changes the weight on the draw bar...


I cant for the life of me figure out how raising or lowering the tow ball height changes the draw bar weight? Its essentially a fulcrum and the weight remains constant throughout an arc..... 

If your lucky youll have a reece hayman type hitch, and can buy several different tow ball tounges with differing height offsets.

only time weight would change would be done by moving axle??

Thats how I understand it.

Or change the weight distribution relative to to the axles....  More weight in front of axle for heavier tow ball weight, more weight behind axle for less tow ball weight


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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2021 at 5:19pm
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Hey you maybe right on single axle(???)
The essential thing is either way.. check the hitch weight at ball level...
We digress..thu interesting .. havnt looked it up.

Right or wrong, Im thinking those old scales that from a offset fulcrum blade have a needle..as weight balance changes the end of the needle goes up down on the scale..
But if one moves the needle the balance of weights either side of the fulcrum changes.

I think you are right when it comes to a evenly balanced either side of the axle...eg if when the jockey wheel is put up and the hitch remains in the air...
 If it naturally sits high it will need to be pulled down .. putting -ve weight on the ball.
 If sits below the ball it will need to be lifted and that puts weight on the ball..


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Post Options Post Options   Likes (0) Likes(0)   Quote Pcj Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2021 at 5:42pm
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Originally posted by kitno kitno wrote:

I'm wanting to lengthen my draw bar by approx 250mm (Aluminum Trailer). Main reason is so I can open the rear door of my van without having to unhitch.
Wanting to know if this would change the towing dynamics for the worst, if at all?



Sliding draw bar??

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Post Options Post Options   Likes (0) Likes(0)   Quote cosmo Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2021 at 5:56pm
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Easiest to just change coupling and those ones easier to lock down also,
As far as weighing just use bathroom scales and a block of wood if glass
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Post Options Post Options   Likes (0) Likes(0)   Quote kitno Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2021 at 6:11pm
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The coupling isn't the issue, the door clears it. A photo says a thousand words, so here you'll go.







Images show it clashing and how far back it needs to go to clear everything.

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