Or a large waist on the driver 
Perhaps a waist like J-O suggests but only lock it when you want. To put a pin in for transporting for instance. The problem I see with that is to be able to get the pin in when loaded or are you compensating when loading so you only have the problem when unloaded?
Well, what I meant was something like this. Permanently vertically fixed via a pin, but trailer - machine can still rotate for climbing uneven terrain.
Throwing both my cents in here.
I am not convinced about a permanently locked waist, it will mean that when he drives in rocky terrain there will be occasions when the trailer is loaded and driving over a rock/hill/log/stump when a lot of weight will be on the drive wheel that is normally out of harms way, it depends if it is designed to handle that weight and plus there will be quite a bit of âbendingâ force on the waist all the time when loaded as well.
Instead of a locking pin it is doable with a hydraulic cylinder as well, lock it when you want and when you donât want it put it in âfloatâ.
Of course I could be wrong but those would be my concerns.
Or Jan, how much weight are we talking about? Is it easiest to put extra weight on the front? In essence put the gasifier back again 
(I missed it at first)
I would think some kind of spring loaded rod in the âmidjanâ i think Bolinders Bv202 used that.
Some modern forwarders have a hydraulic cylinder straightening, with a ânitrogen bladderâ shock absorber in the circuit (could be found on some plows, for âstenutlösningâ. just dont cut them open, some 100 bars of nitrogen really wants to escape faster than a cat in a badger trap 
Johan and Göran. Youâre not listening to what Iâm writing!
You must think Iâm really stupid
Of course the connection has to be able to rotate/âtwistâ, or Jan would only be able to drive on the freeway - for the same reasons Johan discribed. What you are talking about is a locking mechanism used not to tip the trailer over when loading with the crane. Since Jan has got pretty sturdy hydrailic support legs I belive he has been able to do without that feature.
What Iâm suggesting is only to make machine and trailer level in relation to eachother, but still being able to climb a rock or a stump induvidually. Something like this.
This made me laugh. Of course we donât think you are stupid and we did understand what you wrote, not trolling either (love the pictures and Jan looks so happy driving ) but it is not that direction I am talking about, it is the up and down as was the problem to begin with, not the twisting motion of the whole contraption.
You just need to know and understand what I am thinking
Perhaps I am making a chicken out of a feather of all this and it is not a problem at all but as an example:
With the stiff axle you mentioned, imagine going over a small hill in the forest with the ferret on one side of the hill and the fully loaded wagon on the other with the top in between, now the tracks are only in contact with the ground between the last boggie and the driving wheel (as a tank doing a wheelie ) so half of the tracks donât have traction (same on both sides). Is it enough traction to get the load over the hill?
If it is, then it is easy. Just weld the first link stiff behind the ferret and it will be as you suggested.
I am not trying to be an a$$, I just donât want Jan to potentially have other issues further ahead. 
I have a little trouble imagining how it would work to stiffen this, but if you think of a car with a rigid axle for the trailer, it probably wouldnât work.
About 100-150 kg of weight is needed at the front for it to work in the forest, but if I drive against a stump with the wheels on the trailer, the ferret rises.
So either a weight or a spring that holds the front end down, I donât know which is best.
Or remove a bogie on the ferret, maybe, and stiffen it.
It seems like if you stiffen the hitch vertically, youâll ride on the front wheels through a dip, and on the back wheels over a hill. Can you shift some weight off of the hitch? Maybe move the trailer axles forward?
What Kent said, plus expand the stub-frame on the back of the trailer so you can âParkâ your loader claw behind the rear axle a bit farther? And also adding some weight on the front to make up for the âremoved for servicingâ gasifier components. 
Well, moving the bogie forward doesnât work well with the longest dimensions of timber, I have quite a bit of overhang today.
The aggregate doesnât weigh that much, I can lift it myself, so it doesnât affect it that much.
I donât know what to think about the weight distribution problem for the Iller but the simplest solution for the trailer would be a pintle hook type hitch. Allows up and down, side to side and twisting motion.
I would suggest either sliding the wheels or making the tongue so you can push it in and out with the Iller then lock it with hitch pins, with maybe notch to lock you into the right spot. It is a really nice tool, it might make it slightly more useful, if you are just trying to move stuff. You can get it into a tighter space and donât have to worry as much about hitting the wheels.
HmâŠsince Iâm now on the same pageâŠ
Jan, a gooseneck solution would solve the weight distribution, but create problems with the steeringâŠ
Your sand bucket was probably the easiest fix after all.
Hi Jo, i understand what you meant, i just donât think a stiff âwaistâ works that good on a tracked vehicle, therefore i mentioned the BV202, also the modern BV206 uses some kind of âdamperâ in the middle.
Some picâs, these steer by the middle, articulated.
I didnât find that gem, but this one is -way- cooler. It is amphibious so you can avoid paying any bridge tolls and go fishing too! 
These guys arenât -that- far away. It is 1960s Russian so woodgas is the only way you could pass emissions.
You are probably talking about a similar system for connecting a towing vehicle and a trailer, in the front there is a part that allows turning, in the middle there is a part that allows up-down changes with a hydraulic cylinder and a hydraulic accumulator and in the back there is a rotating part for tilt compensation⊠Goran, you probably have something similar in mind.
JO, you draw great, I would like to see more of your drawings.
Neat vehicle. Perfect for the small farm 
. From the linked page:
Drive Unit
Engine |V-2/54|
Drive unit power |258 kW at 1,800 rev/min|
Other parameters |4-stroke ingnition liquid-cooled V-engine|
Cylinders volume |38,800 cm3|
Number of cylinders |12|
Mileage in m^3/km for petrol, trees/mile for woodgas? Perfect for conversion with low rpm, high displacement, 39L engine. Bonus points for raising compression by milling heads for 12 cylinders.
Thanks Tone, hydraulic ACCUMULATOR is the word i tried to remember, a âbulbâ with a nitrogen bladder, just as you draw it.
JanA. here is an add-on system used by some for this problem . . . you mentioned âa springâ . . . this system uses two:
Other longer videos out there.
Videoâs show two more advanced variations also.
Be very aware you will be hard transfering stresses to either back along the trailer neck; forwards to the tow hitch; or both.
Stiffening in the middle, and you can bend-break things.
Weights, yes. A a pain in the arms, yes. But no moving parts. And can be at work-site; travel-change transferred relatively âeasyâ.
S.U.
