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View Full Version : cooked GWS motors. What is actually cooked and by what?


Eggvoel
10-05-2005, 05:24 PM
I've cooked a couple of GWS motors I thought prematurely and was looking for alternative motors in a previous thread. I would like to know generally what is actually being cooked in the motors and the probable cause. Is it the heat from over amps by overpropping? Would a heat sink on the motor help and running without the cowling for better cooling? I've been running 9070 props on B gearing in my Formosa and am going to switch to 904.7, but I like to fly WOT most of the time and then switch batteries and go at it again.
I think I caused my own problems by something I just thought of last night. I needed some weight in the front for CG and had wrapped the clay around the stick mount and the top half of the motor avoiding the vent holes on the motor. This probably caused the motor to overheat as it didn't have any air going over the top half!! Just passing this on so someone else doesn't do a dumb thing like that. Larry

Twmaster
10-05-2005, 05:43 PM
That clay could have been a big contributor to killing that motor. A heat sink is a good idea too. Heat is the enemy. The other thing that cooks motors is too much power being pulled through in the form of too much voltage or to much current causing the brushes to arc. Of course all three things make....wait for it....HEAT! And as I said heat is the enemy. The big key is to not draw more amps than the power set is made for. Prop up or down to get the 'sweet spot'. Sure you will once in a while smoke a motor for no good reason (other than it being weak or defective) but overall the motors supplied with GWS power sets are durable.

There are other threads, including the one you mention, that address much of the issues about excessive volts and current. If I remember the GWS chart they say not to use a 9070 prop on the B geartrain in a 350 motor set.

Dr Kiwi
10-05-2005, 06:50 PM
Mike has the answer - Firstly HEAT (destroying insulation and demagging magnets), and also excess voltage/current (arcing and sparking and burning out the flimsy carbon brushes).

I'm assuming you are only using 2s, but if it is 3s you have really asked for trouble. These GWS cheap can motors are only good for ~80W or 8-10A whichever comes first.

Cheers, Phil

Eggvoel
10-06-2005, 02:17 PM
My Formosa was originally supplied with B gearing and a 9070 prop and an 8060 prop. I assumed those would be the best for it and that is what I used. Looking at the chart on the back of the motor package the 9070 would be for the C or D gearing. I am using 2c lipo's.
I tried the 8060 prop the other day and I just barely cleared the trees where I normally fly.
Must have been the clay because I have used the same set-up in my Estarter and never had these problems.
Thanks for confirming my suspicions. Larry

Eggvoel
10-09-2005, 01:25 PM
I took my cooked motors apart to see what was going on. In all but 1, one side of the brushes were either missing or burnt down to the copper lead holding it. Found 1 end plate with the brushes still in tact so installed them on one of the motors and the motor ran. Would I chance using it on my plane? No way, but I was just curious what was going on inside these things. If someone else wants to try this, I used some fine thread to hold back the brushes to reinstall. Also mark the can and back plate so the timing will be correct. Larry