Hi all,

Last weekend I noticed that the heat shrink on two of the motor leads on my Turnigy 3548-800 in my Panther were stuck together. On a closer look, the heat shrink on the connectors appeared to have shrunk substantially.

I just finished removing the heat shrink and all three connectors show evidence of cold solder joints. One of them only had about 50% fill in the joint and had been running hot enough to have the solder flow and partially melt through the heat shrink.

I advise anyone with one of these motors (or really any motor) to give a close look at the heat shrink and if it show signs of any damage, peel it off and check the solder joint. Mine was a short circuit waiting to happen. This could cause loss of motor/ESC or a battery fire.

John

Absolutely true that you generally get what you pay for.  I notice also that the cogging on this motor is not as strong as the Rimfire I replaced. Could be a sign that the magnets are not as good. However, the motor seems to haul the airplane around nicely and does not seem to run hot. Also is smooth and quiet and is running about the same mAh/minute.

All in all, seems to be a good deal. Ask me again in a hundred flights.

John

I notice also that the cogging on this motor is not as strong as the Rimfire I replaced. Could be a sign that the magnets are not as good.

I do not think so ... I know motors with very strong cogging (PJS) or average (AXI) or almost none (MPJ) and they use the same magnets :-)

Strength of magnets is easy to compare if you compare internal resistance on two motors of the same size and the same KV ... stronger magnets usualy show lower resistance.

I have heard that cogging is due to slight imperfections in magnet placement or slight differences in magnet strength. This makes (if it is true!) certain positioning of the stator heads to be preferred. SInce the stator itself is pretty symmetric, this means that as you rotate an angle equal to the difference between stator heads (30 degrees with a 12 head stator), it will cog into the preferred position again.

It sort of sounds reasonable, but like I say, it isn't clear how much it matters.

I'll throw this one into the loop.  The turnigy in-runners have slottless stator assemblies.  The stators are washers and the windings are inside of them.  They have zero cogging, but have 4-poles.  I also have (2) Hacker B-40 FAI F5D motors that are built the same way.  The hackers are (2) pole.

All of my Turnigy out-runners have very little cogging.  There is less in the SK series than the Gold series.  The SK series is by far better than the Gold series in performance and efficiency.

As far as the soldering on the connectors goes, I always check mine as there is a limit to what to expect when buying a $17-$25 450-700 watt motor.  To me, a small price to pay and a good habit to get into when buying motors.  Most motors don't come with connectors, so I guess it could be considered a wash.  If you use the Turnigy within it's capacity, the only thing you will eventually wear out are the bearings.  I have yet to do that, but I am making it a preventative maintainence deal to change the bearings every season as they are under a lot of stress in a CLPA model.  The SK bearings are of much higher quality than the Gold series and are bigger as well to take more abuse.

I did have an "Operator Error" issue with my Turnigy SK 35-42-1000 when using it in an R/C Pylon bird. I had packed everything very tight and the motor wires were compressed together.  After about 30 flights, chafing caused the heat shrink of (2) motor wires to wear and eventually short against each other.  I thought I fried the motor.  I took it apart and popped the connectors apart.  I resoldered new connectors on and re-heat shrunk them.  I then changed my install and left slack in the motor wire arrangement.  No harm done to either the motor or ESC.  This is a testiment to the robustness of these components. 

Archie Adamisin
Muncie,INdiana   

I worked in aircraft and you would be amazed at how many guys could not do basic soldering with any consistancy. But they would try ..or mybe they weren't ?

Some follow up info on the failed connection.

I got a chance to go flying this morning (Sat, 10.24) for the first time since the Salem, OR, meet. I noticed that the motor seemed to be losing RPM when loaded up in verticals, etc. After some checking , it appears that the terminal that was re-soldered had apparently gotten hot enough to anneal the spring leaves in the connector. It only takes about 1/3 the force to pull this one apart compared to the others. In addition, the electrical tape I used to bundle the wires had a hole melted in it at that connector.

If you have an occurrence like this check to make sure the connector is mating with the same force as the others, and pay some attention to make sure the connector isn't running hot. Turns out the electrical tape was a good over temp indicator.

This points up that I do not know which was the cause and which the effect. The connector may have been marginal which could have caused the solder failure, or the other way around. The re-soldered joint appears to be OK, so bad solder could be the initial cause.

It will be interesting to see if the power consumption goes down after this is fixed.

John