Thread: auction trailer

Hi all, I have a few trailer questions, but , story first.....I got this trailer in a bit of auction madness bidding war when I had a closer look at it I probably paid a bit much for it oh well I didn't have a trailer before and now I do it has a few redeeming features... winch on the front, led lights (needs reverse tho) it tilts, hydraulic brakes and is big for a single axle, was a plant trailer for moving????? Tows ok empty, but, loaded not as good as I'd like has a bit of a sway, only slight, I'm a bit gun shy after having a car tandem throw me off the road many moons ago.

I did a bit of a google on trailer design and seemed to be that ahead of the axle 60% of the trailer bed with 40% behind so if bed is evenly loaded this then gives the tow hitch a bit of wieght, not sure if that gives the 10 to 15% hitch wieght or not I'm thinking that the drawbar length may have an impact on the actual % value.

I had a closer look at mine and it looks like I have a bit too much bed length hanging over the axle especially when evenly loaded, I did place the long lenghts towards the front so as to give some hitch weight but didnt do much to counter the overhang/sway, I tried bumping the tyre pressures up a bit but didn't change.

Questions...
What are the factors that contribute to sway and Is there a single big one?
Is there an ideal drawbar length?
Is there a typical leaf spring rate table somewhere? I want to be able to gauge loaded wieght based on spring deflection.
What is the max load I can have on a single axle, and What determines that max? tyre specs? rim specs? axle max load? spring rate? ADR
The tyres on it are light truck, they have a max tyre pressure of 65psi Has anyone had their tyres up this high towing and if u did, Did u put em up because of a full load?
I registered it as unbraked, 749kg, I didn't know it had brakes at the time, that then means I can take a heavier load, Is that right, and I probably have to change the rego?

Thanks to all in advance


Pete

As our learned friend yonnee would say;

"the axle should be located rear of the middle 1/2" for every foot of trailer body length".

I think though the sway is coming from that very short drawbar that is on it. Can you measure its length from the front of the trailer.

cheers

Fixed from 1" to 1/2". Thanks yonnee

Looks like you've got to much rear overhang to me, reckon the axle needs to back a further 10" or so

Originally Posted by pjt

I did a bit of a google on trailer design and seemed to be that ahead of the axle 60% of the trailer bed with 40% behind so if bed is evenly loaded this then gives the tow hitch a bit of wieght, not sure if that gives the 10 to 15% hitch wieght or not I'm thinking that the drawbar length may have an impact on the actual % value.

Dazzler's right, 1/2" rearward of centre for every foot of trailer body is where the axle should be. And it has nothing to do with the drawbar length at all. There are figures of 10-15% ball weight that are quoted around the trailer and caravan industry, but I strongly disagree. At one end of the scale, an empty 300Kg 6x4, 30Kg is too light. And at the other end, most towbars aren't built to cope with more than 250Kg tops, so 10% of a 2500Kg caravan is a little high.

Originally Posted by pjt

I had a closer look at mine and it looks like I have a bit too much bed length hanging over the axle especially when evenly loaded, I did place the long lenghts towards the front so as to give some hitch weight but didnt do much to counter the overhang/sway, I tried bumping the tyre pressures up a bit but didn't change.

Questions...
What are the factors that contribute to sway and Is there a single big one?
Yes, not enough weight on the towball! Other factors can include axle alignment, especially on tandems, but towball weight is THE biggest factor.
Is there an ideal drawbar length?
How long is a piece of string? I usually prefer 5', but horses for courses. 4' is usually the minimum so as not to hit the front corner of the trailer with the tow vehicle if you jacknife while reversing.
Is there a typical leaf spring rate table somewhere? I want to be able to gauge loaded wieght based on spring deflection.
Let me know the width, thickness and length of the leaves as well as quantity, and I can give you a rough guide as to the rated capacity of the springs, but I know of no table that lists weight by spring deflection.
What is the max load I can have on a single axle, and What determines that max? tyre specs? rim specs? axle max load? spring rate? ADR
The weakest link in the trailer is what determines your capacity.
Let's consider a phantom trailer;
Coupling - 2000Kg
Springs - 1300Kg
Tyres - 1500Kg
Axle (Holden bearings) - 1000Kg
Axle (Ford bearings) - 1400Kg
Axle with no brakes - 750Kg
So if you had this trailer without brakes, your capacity could only be 750Kg. However, if this trailer had brakes and Ford bearings, your capacity can be up to 1300Kg, the capacity of the springs.

The tyres on it are light truck, they have a max tyre pressure of 65psi Has anyone had their tyres up this high towing and if u did, Did u put em up because of a full load?
That would be your only reason to have them pumped that high.

I registered it as unbraked, 749kg, I didn't know it had brakes at the time, that then means I can take a heavier load, Is that right, and I probably have to change the rego?
It would probably cope with a heavier load, but with a registered capacity of 749Kg, not legally. Changing the rego is not as easy as it sounds. Vicroads make it difficult and expensive to do it down here. It was easier to de-register and re-register a trailer I retro fitted a braked axle to, to up its capacity. With its old registration, Vicroads wanted an engineers report, which I can partly understand, but we were a major player in the trailer and caravan repair industry and one of the biggest axle manufacturers in the country. So I couldn't see why a receipt from us couldn't be as good as an engineers report.

Thanks to all in advance


Pete

i think its about right for a tilt trailer?

Thanks for contrubutions...
Measured spring leaves yesterday (finally)

leaf length eye to eye 715mm
width 45mm
thickness 8mm
4 leaves
axle dia 45mm round...are these usually solid?

They do seem very stiff to me, had approximately 1200kg on it yesterday and still heaps of travel.

With the 1/2" dimn, for say a 5' tralier body axle should be 2 1/2" rearwards of centre?

Pete

if you move axle to rear of centre of trailer body it wont work easily as a tilting trailer and will be very sudden in its leveling action when the laod is pulled forward onto the front section of deck.danny

I didn't realize it was a tipping trailer when I was bidding on it, the dynamics of how it behaves as a tipping trailer will change if I move the axel, but, the trailer needs to be rebuilt so I am tossing up rebuild and sell it as a tipping trailer or build something more to my needs which doesn't really need to be a tipping trailer although it could be handy ohh what to do what to do
It does really need to be stable so that might override any tipping disadvantages


Pete

Originally Posted by pjt

Thanks for contrubutions...
Measured spring leaves yesterday (finally)

leaf length eye to eye 715mm
width 45mm
thickness 8mm
4 leaves
axle dia 45mm round...are these usually solid?

They do seem very stiff to me, had approximately 1200kg on it yesterday and still heaps of travel.

With the 1/2" dimn, for say a 5' tralier body axle should be 2 1/2" rearwards of centre?

Pete

Your measurement for standard axle placement is correct. However, this the usual rule of thumb, but not the be all and end all, so there are some applications where this measurement will differ.

As for your springs, all the information I have at my disposal, and I've collect a fair bit over the years, show that spring set to only be around 700Kg for a 4 leaf spring.

Originally Posted by danielhobby

if you move axle to rear of centre of trailer body it wont work easily as a tilting trailer and will be very sudden in its leveling action when the laod is pulled forward onto the front section of deck.danny

But this would happen with any tilt trailer once the load crossed the centre of the pivot point. Unless you're thinking of the fact the tilt body will slam back down once the load is removed from the end of the trailer. And if the trailer were to be for loading and unloading a vehicle, I can see this being an issue. I did see one set up with shock absorbers mounted between the drawbar and the tipping body that dramatically slowed the tipping action in either direction.

Originally Posted by Yonnee

As for your springs, all the information I have at my disposal, and I've collect a fair bit over the years, show that spring set to only be around 700Kg for a 4 leaf spring.

Is that 700kg/inch of travel