Lowloader airbag to coil springs conversion

[jason@helmersdale]

Hi, does anybody know where I can get four coil springs to replace airbags on a Lowloader trailer we have? Like the one in the picture? The air system on it is like spaghetti junction and is ready for a refit so might just simplify it and get rid of the air bags and keep the air brakes. Cheers

 

[Andrew]

Think Totrax made them but gave up. Springmasters may be able to help.

 

[e5c0rt.mk1]

Hancock trailer conversions, convert alot of their trailer to coil springs.

I'm not sure if they are buying them from somewhere, or getting them made.

Might be worth phoning them, see if you can buy some off them.

https://m.facebook.com/pages/catego...er-Conversions-271014196709768/?locale2=en_GB

 

[4755dave]

Used to be a guy on ebay selling them. I did a low loader to coils. It's ok but no axle equaliser.

 

[scary spider]

I have 4 of these that I brought 2 years ago and have never used. £400

 

[avag]

Does anyone know of a supplier for these springs? Looking to convert a drag trailer from air to springs

 

[4755dave]

I've done a low loader. Wont do another. No equaliser between axles. Lea spring will make what you want.

 

[mo!]

@pellow

 

[pellow]

@pellow

Thanks, going for a new leaf spring set now

 

[tinman]

I've done a low loader. Wont do another. No equaliser between axles. Lea spring will make what you want.

if you don't mind me asking Dave, could you explain that a bit more to me.
dose not having an equalizer between the axles make for problems in a retrofit like this and obviously so by the sounds of it but what is the result.
how would the airbags have compensated for it.

 

[4755dave]

Yeah. The springs I used are very stiff.
The axles only drop 1 inch with D6d on it. Loaded it's fine. Empty it rattlesthehitch like swine as its virtually got no suspension. It has moved a lot of gear for us. I just wouldnt do another. I'd look at keeping air bags and running an oil powered compressor

 

[Forever Fendt]

Will drawbar springs not do this job

 

[e5c0rt.mk1]

I dont think a drawbar spring would have enough travel on them.

I've been trying to find a suitable spring to use as i need atleast 8 for a couple of projects. I cant find anything suitable that doesnt cost a fortune.

Tried to get them made at a few places too and they just keep saying they are unable to make them.

 

[Andrew]

The problem is this suspension system is made for ‘active’ springs ie air. As @4755dave says, when empty it’s basically like having solid axles as there is no movement. I suspect on any rough ground then one or another axle will be off the ground. If you fit softer springs it will be too unstable loaded. Air systems vary the pressure dependent on the load to overcome this.
Standard steel spring setups have a balance beam, air lets pressure between the axles, which makes an even load on the hitch on rough ground. I suspect these quite serious flaws are why people don’t use them any more.
I would look at fitting an air compressor somewhere. Fit a second air tank and a small electric compressor, as long as you aren’t doing a cycle (load and unload) every 5 mins it should cope fine. If you are maybe a hydraulic drive compressor would be better.

 

[4755dave]

Exactly right. It will lift an axle as it goes over a high spot. Changing the balance and thumping drawbar up and down

 

[Colliedog]

if you don't mind me asking Dave, could you explain that a bit more to me.
dose not having an equalizer between the axles make for problems in a retrofit like this and obviously so by the sounds of it but what is the result.
how would the airbags have compensated for it.

Air pressure travels between the bags so as there is always the same pressure pushing up at the top of the springs. So the spring rate of an air bag is always the same regardless of the ride height at a given pressure. If we take a standard coil spring the rate is linier, so for arguments sake a spring has a rating of 1000lbs per inch. For every inch its compressed the spring rate rises another 1000lbs so if it was compressed 3inchs it would be suspending a weight of 3000lbs.
So in this situation where there is no bogie to equalise the load if the front axle is going over a bump and the spring is compressed to 4inchs and the rear is compressed to 2 inch's the front axle of two springs will we taking 8000lbs of the load and the rear axle 4000lbs of the load instead of 6000lbs each for the air springs which have transferred some air and equalized themselves.
Its not ideal but a lot better than welding the axles straight to the chassis.

 

[tinman]

Air pressure travels between the bags so as there is always the same pressure pushing up at the top of the springs. So the spring rate of an air bag is always the same regardless of the ride height at a given pressure. If we take a standard coil spring the rate is linier, so for arguments sake a spring has a rating of 1000lbs per inch. For every inch its compressed the spring rate rises another 1000lbs so if it was compressed 3inchs it would be suspending a weight of 3000lbs.
So in this situation where there is no bogie to equalise the load if the front axle is going over a bump and the spring is compressed to 4inchs and the rear is compressed to 2 inch's the front axle of two springs will we taking 8000lbs of the load and the rear axle 4000lbs of the load instead of 6000lbs each for the air springs which have transferred some air and equalized themselves.
Its not ideal but a lot better than welding the axles straight to the chassis.

yes, when you spell it out it makes sense now.
of the two tractors i have here neither have air on them altho its available to retrofit but at a decent cost.
everything i have here is on hyd brakes, it dose for my work but air would make for a smoother ride and braking would be a lot more civil on tyres.

i have the makings for a hook loader trailer here and possibly "sometime" i would like to have made the damn thing (time being the enemy for me) but i had considered using the springs to convert the axles from bags.
as you say, its not the right job but more of a half way house.

cheers for taking the time to post that description.

 

[tinman]

either a hyd or electric compressor sounds like a better job all day long compared to the spring retrofit.
could one not have a system encased within a box on the chassis with a compressor on the 12v supply that would have a pressure regulating system on it so when its plugged in it fills the tank and stops and when it gets low in air pressure it restarts to top it up much like your garage compressor.

 

[Colliedog]

either a hyd or electric compressor sounds like a better job all day long compared to the spring retrofit.
could one not have a system encased within a box on the chassis with a compressor on the 12v supply that would have a pressure regulating system on it so when its plugged in it fills the tank and stops and when it gets low in air pressure it restarts to top it up much like your garage compressor.

I’ve seen it done on a hydraulic motor. Mike at Erintek has told me that he made lots over the years.

 

[4440]

Built one about 11 years ago. Built a trailer that ran on air suspension.
At the time we were using tractors that were on air and some that did not.
It has worked well, have a remote pressure gauge in the cab so we know when to run the oil and not to.