The landrover ones are quite good because they have a quite durable linkage with them that makes designing a fitment easier. They also have a roughly 90 degrees range but the lever can rotate full 360 degrees. This prevents damage if the linkage goes a bit further than the measured range.
It’s what I decided to use anyway.
…for example…
…and how I fitted mine (Fendt 716).
No one has mentioned linear sensors yet but I think they have a place, I find them more robust and there is no play in the linkages etc.
I like these Miran units: Miran Lineaire Positie Sensor WY 01 15 Mm 300 Mm Knik Verplaatsing Transducer Met Heim Gewrichten Connector/Elektrische Heerser|output| - AliExpress
Nice mounting!
Easier to correct Ackerman? (as french I like to mention Jeantaud…)
Thanks 
I have no idea, I haven’t bothered with Ackermann correction. I don’t use uturn on the combine, and for small corrections onto the AB line it makes no difference.
On the tractor, with a central steering ram, ackermann has no effect anyway.
Are you sure about the Ackermann issue? Anyway, I would not like to see a fight between different WAS sensors here. Every sensor deserves to be introduced, facts stated but the final choice needs to be left for the person building the system (taking into account his/her preference on price, size etc.).
How much time past from installation?
Is it protected from dust and dirt?
The steering action compared to ram displacement might be nonlinear in a system with a central ram, but it is certainly symmetrical unlike any measurements taken at or around the kingpin.
@d1ken I’ve had a linear sensor installed on my test tractor since 2017, no issues so far. The unit itself is IP rated so I’m confident it can withstand the conditions.
If the “kingpin” sensor is properly mounted, it removes the ackermann issue, gives a linear and symmetric signal. See posts from kaupoi et al. Then again, I agree that the linear sensor should work fine and is easier to install to give a very symmetrical signal at the straight forward point. I believe other details are more important for the choice. I was just commenting on the Ackermann issue, I’m sure your tractor too has Ackermann steering geometry (be it an issue or not, I’d say not).
but the piston rod is not free to rotate in the cylinder?
Yes the piston is free to rotate, there is a joint between the piston and the brushes
Edit:
If you mean the hydraulic cylinder rotating then it depends on the machine. In my case the ram is connected to the rest of the steering linkage by ball joints so there is maybe a few degrees of movement, but nothing major
I agree. I made this mistake first time. It sounds like it’s been fine for years so maybe that one doesn’t rotate but I see no reason why it couldn’t.
Hello,
Agree. On my Fiat tractor, I have a cylinder on each wheel (not a unique cylinder between both wheel).
When wheel are straight, the cylinder are out of 13cm. Max course are 20cm.
When I turn right, cylinder of right wheel is fully retracted (so it traveled 13cm) and the cylinder of the left wheel is fully extand (so it traveled 7cm). Turn wheel full left it’s the opposite.
So the linear sensor will be fully exposed to the ackermann effect.
So we had to be aware how your steering work before choosing a sensor type and assess what will the effect be on WAS output value.
Math
Absolutely, I know that dual ram systems like on my combine are susceptible to Ackermann, but like I said unless working at extreme steer angles, like when using uturn, it’s not a huge problem around the middle of the steering range.
This problem could be eliminated by putting the sensor on the track rod that runs between the two wheels
Using a rotary sensor it is relatively easy to cancel out Ackerman with linkage design. (And poor linkage design can easily create an Ackerman like imbalance from a straight line reference)
Does anyone know any linear sensors available in europe that arent over 100 euro? Seems like a real easy solution and since you can adjust the ackerman effect in the software there is no need to do so with the hardware.
Reichelt has one but no idea if it’s robust. The one from Ali seems more robust and they ship for free.
Hi
Ok for the linkage but un some cases
(Like our carraro front drive with suspension and mud guard) it s not so simple to have à linear and robuste linkage
So i prefer to install it “the best robust” then measure à few points (résistance vs angle) and put it in linearization table (map) afterwards in the Ino code, just important to have à few points close to 0 deg
François
a little inspiration Fendt 714 TMS 2004 ackerman 115%
They are shy on detailed specs but most likely it would work. How much is it? I’m afraid that it costs a lot compared to other options.
