Positioning of trailer axle

[Axl]

I pulled this of the RACQ web site, http://www.racq.com.au/motoring/driv...ions_explained

Tow Ball Load is the proportion of the trailer weight that is applied to the rear of the tow vehicle.
A vehicle’s Ball Load specification will be found in the vehicle’s handbook and will be listed as a weight in kilograms or as a percentage of the trailer’s ATM.
Ball Load specifications are often around 10% of the maximum towing mass specification, however this isn’t always the case. European vehicles in particular can have quite low allowable Ball Loads in relation to their towing capacity.

Too little Ball Load can cause the trailer to become unstable and too much can be detrimental to the tow vehicle’s durability as well as affecting its stability, steering and braking.

[Gon Fishun]

Tow it to the weighbridge with your usual tow vehicle before you do anything. For about $25 they will give you combo, steer and drive, tow vehicle, boat alone on jockey wheel and tow ball weight. It is a real good starting point. Takes all the guess work out and is very handy to know.

[gruntahunta]

5 to 10% of the BMT weight on the towbar is the generally accepted range.

Subject of course to the proviso that you do not exceed the car manufacturers max towbar downforce rating. Yes, manufacturers do specify a max towball downforce, or weight on the towball. Look it up in your owners manual or contact our cars manufacturer and they will tell you.

Too little weight on the towbar is the cause of trailers swaying on the highway, which is a dangerous thing. I wouldn't go less than 5% in your case, assuming a BMT weight around 1000kg, that would be 50 kg as an absolute min.

So Grunta, there are 3 things to consider.

1. The position of your boat on the trailer. You can move the winch post back or forwards to adjust weight distribution. So, in your case, you could look at moving the winch post backwards -ie away from the car. This will move the boat backwards and thus shift the balance point to the rear. But you need to consider that ideally, the last row of rollers on your trailer should be close to the transom so they support the motor's weight. So have a look at his and see if it is feasible to move the boat bacwards a bit.

2. The axle position. Looking at your avatar picture, it seems we are dealing with about a 5m alloy runabout, correct? If so, I would agree with Finga, start by moving it 6" forward and check. Take careful measurements from each end of the axle to the end of the coupling and make sure it is the same distance from both sides, that will keep the axle parallel.

3. Weight in the boat. Can you move heavy things towards the back of the boat? Batteries, fuel tank, anchors, etc? It all helps.

You might end up doing a bit of all of these things.

But it really is try it and see.

Cheers

ML

Thanks Moonlighter.... The boat is a quintrex 4.75 and has an 85 2/stroke Yamaha which sits about 1 metre from the transom on a pod....so I don't hink I can move the post back as this would create too muck "overhang" with the motor.

I have recently installed a 110 litre under floor tank which sits more in the centre of the boat so this has created the heaviness at the front of course compared to the 4 plastics tanks that were always located at the rear most point in the stern.

[gruntahunta]

probably need to move it forward around a foot.

can you get access to the frame underneath with axle stands?
Easiest way to judge how far to move the axle is to wait until the missus goes out, then put the boat onto axle stands at roughly the point your thinking of moving the axle to , and her set of bath room scales under another axle stand under the tow hitch, unless your using a 4wd with a large tow bar, you dont want more than 80 odd kg weight on the scales, preferable a lot less. (Most standard towbars are rated for no more than 90kg down weight)

Try lifting it before putting the missus scales under it, you wont do your self any favours if its 150kg and you bugger the scales

oh and wipe the grease off the scales before you put them back, dont want to get caught!

LOL Feral.... but a really good idea mate....No matter what the weight is on the scales, they have handled that before....Geez I hope she doesnt read my posts or I am a dead man.

[gruntahunta]

Thanks for all the great adviseguys...I have decided to leave it where it is until I get to Maroochydore next month...from then I won't have to travel on Highways so will move it forward then, just to make it a bit easier on my back etc. My jockey wheel is the swing away type and so I might replace that with a good pnematic tyre one that makes it easier to push around.

Anyways...all great advise that I will implement in the near future.

[SunnyCoastMark]

Thanks for all the great adviseguys...I have decided to leave it where it is until I get to Maroochydore next month...from then I won't have to travel on Highways so will move it forward then, just to make it a bit easier on my back etc. My jockey wheel is the swing away type and so I might replace that with a good pnematic tyre one that makes it easier to push around.

Anyways...all great advise that I will implement in the near future.

Hey Grunta,
If you upgrade your jockey wheel - there are a couple of points to keep in mind:-

1) Stay away from pneumatic jockey wheels - they don't have to loose much air to go flat - and they are always going flat. You are better off buying either an 8" or 10" solid rubber model - both ALKO and ARK do these
2) If you go the larger jockey wheel - make sure that you have enough height to still swing it down when it is on your car - otherwise you'll be back to trying to lift the drawbar up to swing the jockey wheel down. - If you buy the type that are held on by U-Bolts - there are usually a couple of positions you can fit them (up or down)

Mark

[johncar]

What sort of trailer is it?
What vehicle do you tow it with?
What rating is the wheel on the jockey wheel?

Hi finga,
It's a Belco Trailer similar to the one in the pic 7th photo in the marine pics ATM 3500KG: http://belcocustomtrailers2-px.rtrk.com.au/photos.htm#
Tow vehicle is a 2012 Mazda BT50 2WD Dual Cab
The jockey wheel is Alko, max 500KG static load, it's a great jockey wheel in fact: http://www.alko.com.au/vehicle-techn.../auto-retract/

It only get up to around the 300KG when I carry a bit of a load full fuel and water, but normally it's around the 280KG anyway. If I am travelling any distance I use Levelling bars like the ones for caravans.

[finga]

Hi finga,
It's a Belco Trailer similar to the one in the pic 7th photo in the marine pics ATM 3500KG: http://belcocustomtrailers2-px.rtrk.com.au/photos.htm#
Tow vehicle is a 2012 Mazda BT50 2WD Dual Cab
The jockey wheel is Alko, max 500KG static load, it's a great jockey wheel in fact: http://www.alko.com.au/vehicle-techn.../auto-retract/

It only get up to around the 300KG when I carry a bit of a load full fuel and water, but normally it's around the 280KG anyway. If I am travelling any distance I use Levelling bars like the ones for caravans.

I had a quick search for the specs of the BT50 (great ute by the way ).
Max. towing capacity about 3,350kgs
Max. ball weight about 330kgs

Not much safety factor in the tow ball weight I'd have to say though.

Every one seems to look at the specs for the prime mover. How about the specs of the trailer seeing it's what's been towed and, in my opinion, the deciding factor to tow ball weight. Why?? Because they're the buggers who engineered it.
As an example Dunbier (one of Australia's bigger boat trailer mobs??) recommends a tow ball weight of 5-7% of trailer weight.

We'll use John's boat as an example (nothing meant there matey...your just handy that's all )
3,000kg boat, motor and trailer package and he has 300kgs on the tow ball which is 10%
Dunbier recommends 5-7% so that would put a weight range they find reasonable on the front of their trailers between 150-210kgs for a package weighing 3,000kgs.
Having that 300kgs on the tow ball would make the insurance company happy if ever there was an accident wouldn't it??
90-150kgs overweight on the tow ball??

[johncar]

Yeah I am probably running at about 9% most of the time closer to 280KG. It feels good at that and the rig is nice and stable on the road. My friends 3200KG + BMT is a little lighter at around 240KG and he tells me it sways around at that and he has to add some weight forward to settle it down.

I think that there is more to it than just the weights alone and would depend on where the weight is centred, ie he has a 400 -500KG + inboard and sterndrive sitting on the stern and I have a 250KG outboard which would make a difference.
Lighter rigs with less weight behind the axle would no doubt get away with less towball weight. Suspension set up and centre of gravity would also come into play.
I am pretty happy though with the balance I have and it feels good on the road, the BT50 seems a great tow vehicle so far but I go nice and steady.
Sorry getting the thread a bit off track but I was just trying to make the point that there comes a time where it becomes impractical to manually try and lift the drawbar manually and it is essential to have a functional jockey wheel or stand set up to save your back.