What kind of drawbar on a forestry trailer?

[Sutton]

Hi All,

 

Thought I'd ask for your reactions to a few ideas on converting a forwarder bunk/crane into a tractor forestry trailer. Est. tare weight 4ton, gross 15+ton

 

cranab | eBay

 

A fixed drawbar with swivel ring hitch is obviously the first place to start. But its a bit limited other than for use in the yard.

 

I've got two other options.

 

The crane weight with the bogie axles mean stabiliser legs aren't necessary. The prob tho is that all that log loading will be exerted more on the tractor hitch than the trailer axle. A lot of stress/force - more than the 3ton max weight limit it should have.

 

So what to do?

 

I've almost discounted a sprung drawbar cos forwarding loads at speed (even on the road) are unlikely but it may help in dampening the shock of loading. What do you think?

 

A second option is to fabricate a steerable drawbar (the baseunit being articated means this isn't too complicated). This would definitely require a free swivelling jockey wheel to displace the weight from the the tractor hitch. A bit like this but obviously with a rigid much more substantial drawbar:

 

 

Would you be happy using something like this? A towable terragator sort of thing. If things go to plan, I'll post some work in progress pics next month

 

Cheers:001_smile:

[farmer rod]

  Sutton said:

Hi All,

 

Thought I'd ask for your reactions to a few ideas on converting a forwarder bunk/crane into a tractor forestry trailer. Est. tare weight 4ton, gross 15+ton

 

cranab | eBay

 

A fixed drawbar with swivel ring hitch is obviously the first place to start. But its a bit limited other than for use in the yard.

 

I've got two other options.

 

The crane weight with the bogie axles mean stabiliser legs aren't necessary. The prob tho is that all that log loading will be exerted more on the tractor hitch than the trailer axle. A lot of stress/force - more than the 3ton max weight limit it should have.

 

So what to do?

 

I've almost discounted a sprung drawbar cos forwarding loads at speed (even on the road) are unlikely but it may help in dampening the shock of loading. What do you think?

 

A second option is to fabricate a steerable drawbar (the baseunit being articated means this isn't too complicated). This would definitely require a free swivelling jockey wheel to displace the weight from the the tractor hitch. A bit like this but obviously with a rigid much more substantial drawbar:

 

 

Would you be happy using something like this? A towable terragator sort of thing. If things go to plan, I'll post some work in progress pics next month

 

Cheers:001_smile:

 

I would want to keep some weight transfer to the tractor for less drag and more traction.

[doobin]

Your not gonna be able to push a dolly trailer around for **** in the woods. Discount that idea immediately.

 

Also, no weight transfer to the tractor will be as bad as to much.

 

If it's only the loading process that will put your drawbar nose weight over the limit, then fit stabiliser legs, it's a no brainer.

[Sutton]

Thanks for that. Agreed completely on transferring weight from trailer to tractor for traction as well as not going down the dolly route.

 

The reason I ask is the positioning of the axle is very far back

 

That is, weight of the crane/headboard, half the bunk weight and half the load of logs which would put about 8ton directly on the tractor hitch.

 

Another option is repositioning the axle forward. That's probably the best way to go. Even if it's a lot more work

[Chris Sheppard]

On something of that size and weight, I'd personally think a steering drawbar wouldn't be that much use as you wouldn't want to be dragging that dead weight round the woods through trees, unless you were planning to keep the drive to the bogies somehow. As a secondary forwarding trailer from the edge of the wood to where the wagons can get, then it would probably be quite good.

 

The old Timberliner driven trailers were quite heavy and they didn't have legs on so surely it can't put that much strain on the tractor hitch?

 

However, with a crane of that reach, I still think I'd fancy a set of legs - the forwaarder would more than likely have had a hydraulic stabiliser to use the weight of the front half of the machine for ballast too.

[donk]

So are you the person selling the crane?

[Sutton]

  Chris Sheppard said:

On something of that size and weight, I'd personally think a steering drawbar wouldn't be that much use as you wouldn't want to be dragging that dead weight round the woods through trees, unless you were planning to keep the drive to the bogies somehow...QUOTE]

 

Thanks Chris. Good advice. Just trying keep options open.

 

The Kockums manual has the bogie innards as direct drive cogs rather than sprockets and chains, so could be driven with a PTO shaft off the tractor as there's nothing wrong with the prop shaft etc.

[Sutton]

  donk said:

So are you the person selling the crane?

 

Yes, I am. PM sent

[Craig.]

Could you not use the front part of the articulated joint to make a drawbar on, keeping the original steering rams, pivot, and lock, to make a steering drawbar. And put some simple legs on front of trailer.

Moving the axles forward a bit would help with weight distribution but would be a big job with bogie axles. I know of it done on a back end of a volvo forwarder made trailer, but it was a fixed single axle so relatively simple, it took some weight off tractor and helped make it a bit more manoeurable.

[Craig.]

  Sutton said:

The Kockums manual has the bogie innards as direct drive cogs rather than sprockets and chains, so could be driven with a PTO shaft off the tractor as there's nothing wrong with the prop shaft etc.

The volvo made forwading trailer was made into land drive but it needed a reversing gearbox as the prop shaft turned the wrong way compaired to the tractor pto.