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     This is Linde BMV-105 variable displacement motor with a simple proportional displacement control. It is not that this motor has a special control module or something - no - it's quite simple. It possesses, however, what I like to call "the other way round" adjustments, making it the perfect example of how things in hydraulic components often are the opposite of what they seem, and a good illustration to my previous post on left adjustments.

   When you look at it - you see nothing but a normal bent-axis type hydraulic motor, which has two adjusting screws and a couple of pilot lines. On the first glance everything is standard and pretty much alike other bent axis motors. Let us look now at the adjustment screws one by one.

    First - the displacement limiter. Again, from the outside you can see that it is a robust screw situated on the max. displacement side of the end cover  - in a classic design of a bent-axis variable displacement motor this would be a simple mechanical stop that limits the maximum displacement. However in this motor it limits the minimum displacement. You can see why here - the stopping screw has a head that works inside the servo-cylinder - the more you screw it out - the bigger is the minimum displacement of the motor.

    Now - the proportional displacement control. This is a simple control, based on the good old spring feedback design. This particular module was using the Y port (check out the schematics) to override the X port signal when needed, however on most motors I've seen so far the Y port is not used (it is plugged and is internally connected to the motor case). Now if we consider the control threshold adjustment - we'll see that screwing the adjustment screw in actually de-compresses the spring, and lowers control start pressure.

   As you can see - the motor is a perfect example of the "other way round" adjustments. The stopping screw at the maximum displacement side is actually the minimum displacement limiter, and if you want to increase the displacement control threshold - you must turn the adjusting screw out!

   The rest of the motor is trivial. It has the loop flushing relief and shuttle,and the rotary group is, well, just another Linde-ish rotary group.

   One thing I would really like to ask Linde engineers - where the hell are the servo-pressure measuring ports?!! When you troubleshoot a closed loop transmission sometimes you need to confirm whether your variable displacement motor is in the max. or min. displacement, which is done through servo-pressure readings . In case of this motor the only thing you can read is the model plate - it says "Linde BMV105" - not a helper, is it?

    Here's a tip for you - if you are not sure whether your BMV 105 is in the max displacement (for example when you see that you closed loop transmission doesn't give out the torque you need, and you suspect motor displacement issues - screw the min. displacement stopping screw all way out - by doing so you mechanically bock the motor control at max. displacement, eliminating any influence from the displacement control module.

    This series is rather old, so we don't get those often these days. Like any other Linde creation - these are very high quality built motors, with remarkably over-priced spares and design that can be characterized as "different for the sake of being different" and "over-engineered for the sake of being unique". Are they good and reliable? Yes, they are, very much! Would I want one in my machine? No, I wouldn't, and I'd replace one with a Sauer or a Rexroth motor if I had.  This is subjective, of course...
Linde BMV 105 displacement control schematics
Linde BMV 105
Feedback spring
Linde BMV 105 displacement control
Loop flushing
Loop flushing relief valve
Minimum displacement limiter