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Current replacement for the blue "Slo-Syn" stepper AP servos?

moespeeds

Well Known Member
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Hi guys,

My 8 has the older blue "Slo-Syn" stepper motors. I've been having trouble with my AP holding wings level in any kind of turbulence or gusts. I changed out my old Tru-Trak for a new Xcruze 100 to no avail.

At Oshkosh last week I spoke in person to Stephan, the brain behind the Xcruze system, and in describing my problem he pointed out that my servo is most likely shot.

I have a whole new Garmin panel, AP, and servos on order, but who knows how many months that will take. Garmin is projecting 6-8 months. In the interim, I'd like to get this servo swapped out so I have a reliable AP. So what do I replace this thing with?
 

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Hi guys,
My 8 has the older blue "Slo-Syn" stepper motors. I've been having trouble with my AP holding wings level in any kind of turbulence or gusts.

In the interim, I'd like to get this servo swapped out so I have a reliable AP. So what do I replace this thing with?

Based on the specifications, looks like a regular NEMA 23 stepper motor to me, the ones which are used in CNC equipment of all kinds. Very common in hobby-level projecs (like 3d printers or routers).

Disclaimer: everything below is based on my experience with CNC hobby projects, I have absolutely zero knowledge how stepper motors are used for autopilots.

If it was a CNC project I was doing, I would just buy NEMA 23 motor with at least the same current / torque rating (higher is better, but motor could be larger / longer). Something like 23HS22 I've just found on eBay. It is 1A/181oz-in, close to KML061F02 1.05A / 170 oz-in (bipolar configuration; since KML061F02 has 4 leads, it must be used in a bipolar configuration).

The way stepper motors are controlled (again, in a hobby CNC world) is by feeding them the specified current via the stepper motor driver (which usually takes input in the form of two control signals, "direction" and "make a step").

So, if motor is 7A motor, it does not mean it would require 7A, but it means you can configure your stepper motor driver to provide up to 7A of current through it (more current means more holding torque). In a given NEMA package motors could be of different length with different specs (typically, the longer the motor the more holding torque it can provide).

The only thing that was relevant for my projects were the current and the torque (I want to configure my driver for the maximum current the motor is capable of handling so I get the maximum holding torque). However, I never had to worry about inductance or resistance of these motors, which might be important for a specific stepper motor driver you have in your autopilot. The hobby CNC stepper motor drivers are used are pretty universal for non-critical it-can-fail-and-nobody-cares applications.

P.S. The stepper motors have two windings, A and B. Some has 4 leads (2 for each winding), some has 6 leads (2 for each winding + 1 center leads for each winding). The 6 lead motors could be wired in different configurations, but the easiest is to treat them as a 4 lead motor (find two leads with largest resistance, and ignore the center lead).

P.P.S. Also, might worth doing a basic motor check. Measure resistance between the wires to see if it is the same for both windings A and B and also you don't get any connection ("infinite" resistance) between leads of A and B windings.

P.P.P.S. Looking at my collection of motors, there are also with 8 leads which are two halves of two windings. The most flexible ones, you can connect halves in serial, in parallel, use only one half.

P.P.P.P.S. Seems like CNC motors tend to have higher current / lower resistance and impedance, for the same torque (so they work better at higher speeds). Without knowing the details about the actual driver (which, as I understand, is a part of the servo module), hard to tell the range of acceptable spec differences if the motor is replaced with a different model.
 
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I'm in the same boat. Did you find a good replacement? Which ebay servo did you find. I couldn't find any rated for 1amp and 5vdc
 
Using DuckDuckGo search for the part number in your photo, it took me to this.

Looks like you would need to phone to get price and delivery schedule. Maybe you can find that part number on eBay.
 
Servo Available

If anyone is interested I have a very low time one I used as a roll servo that I removed for upgrade a few years ago that I was going to list. Its stamped 5.19vdc 1.05amp
Message me if interested
 
CATPart is correct about Kollmorgen

In my searches, I began to believe that this is the company took over and that now makes the motor...It is the KM061 series, and look at page 12 in their pdf.

Website:
https://www.kollmorgen.com/en-us/products/motors/stepper/hi-torque/km-series/

PDF:
https://www.kollmorgen.com/sites/de...s/Old Stepper Catalog_Superior Electric_0.pdf

If you google kollmorgen you will find sites that sell their products. A call to one of them could probably match your stepper motor. If you are only going to use it until Garmin shows up, then you might want to find a used one.
Good luck
 
Servo Available

If anyone is interested I have a very low time one I used as a roll servo that I removed for upgrade a few years ago that I was going to list. Its stamped 5.19vdc 1.05amp
Message me if interested
Do you still have the servo ? If so I’d like to buy it . Thanks
 
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