View Full Version : Ascent glider and very hot speed 400 motor

06-26-2006, 07:01 AM
I have read all posts on this forum regarding the Ascent glider, overheating motors, change of props, etc but I still need some advice. I use the standard speed 400 motor, 35 amp speed controller and a 2cell (2100 mAh) lipo battery. I have fitted the 6.3 Graupner prop. After about a 15 minute very windy flight (full throttle for 75% of the time) the motor was very, very hot (smelled burning). I find this surprising seeing that some owners have had this problem but they were using 3 cel lipos. I have now, as suggested in another thread, fitted a scoop/air inlet but have not tried it since. Now my question: The motor has definitely sustained damage but is still running fine (when turning the prop a very obvious unevenness/notchiness is felt). Could the motor when (not if) it decides to stop working altogether cause an internal short and if this happens what would be the potential effect on the motor controller and battery ? I don't mind the motor stopping in midair but I do not want to loose the aircraft or the very expensive lipo battery. By the way, the speed 400 motors are not that cheap here in South Africa so I want on keep using it for as long as it will allow me before replacing it.



Sky Sharkster
06-26-2006, 03:32 PM
Hi Erik, Welcome to Wattflyer! We have several of the Ascent gliders flying here, most have gone to brushless motors for more power and longer life. I believe the problem is running it for so long (nearly) non-stop, even with a vent hole the motor is fully enclosed and the heat build-up likely burned the brushes. They're not going to stop the motor(yet) but it will be down on power and eventually it will stop running. I've had that happen on a couple of LMR "400" gliders (indicated by a plume of smoke!) and still had R/C control but another time the heat melted the wire to the ESC and I lost everything, including the glider.
Here's my suggestions, hope they help;
Cut air exit holes behind the motor and battery. The general rule is the exit holes should be twice as large as the inlet holes.
Make sure the front and rear bushings/bearings are frequently oiled.
Don't run the motor full throttle for more than a minute or so. Shut it off and glide down. If it's too windy to do that, fly another model!
Put in a 20a fuse inline between the motor and ESC. Even if you cook the motor you should still have R/C control. Might have to go to 25a (if it cuts out too soon) but I'd try 20a first.
Next brushed motor, use the water break-in method first. This will smooth out the brush faces and increase the durability and lifespan of the motor greatly. Also adds a little RPM.
If all else fails, go brushless!
Good Luck!

Crash Test Dummy
06-26-2006, 03:38 PM

Can't you order motors on line? I got a brushless motor on e-bay for a dollar!!. I wouldn't take the chance of loosing the plane over a brushed motor. That is a very nice little glider. I had one once, it lost power in flight due to a bad battery connector. I watched it circle and circle as if flew far far away, sinff sniff!! With electronics you always stand the chance of a short/failure after you tax the heck out of any 1 component.

Good Luck,

06-27-2006, 06:04 AM
The air inlets and outlets have been done, I will install a fuse and try again. Thanks for all the suggestions and advice.

Regarding ordering onlie, the Rand/Dollar and Rand/Euro exchange rate is not very favourable. The postage is usually the cost that makes it too expensive so we need to combine several people's orders to make it worthwhile. Sea freight is cheaper but it takes months ( up to 4 to 5 months) to arrive.

Again, thanks for the suggestions


07-05-2006, 09:19 PM
If you are using the motor at full throttle 75% of the time you are missing the point of a sailplane entirely. This model is designed to climb out and then, with the motor off, soar for a while (like 10 minutes or so), which allows the poor old speed 400 to cool off a bit. Running a speed 400 for about 10 minutes or more at full throttle would be roasty-hot even on a wing where the motor is in the airflow. With the motor inside a fuselage you are just trying to kill it. The notchiness is probably your burned up brushes hooking the commutator...

The Ascent really isn't a sport plane.

07-06-2006, 06:02 AM
I realise that the Ascent is not a sportplane. As it is my first rc model, have never flown a model before I probably use the motor a lot more than an expereinced pilot, mostly to get out of trouble. I am sure there are people who can learn to fly and look for a thermal on their first or second flight, but I am not one of them.

07-06-2006, 06:53 AM
I have no first-hand experience with the stock motor in an Ascent. The pre-flown one I bought recently has a great Ultrafly B/06/15 brushless motor, Thunderbird 18 ESC, and a Graupner 9-4.5 folding prop. With that and an inexpensive but good 1600 mAh 3S LiPo, the Ascent is, IHMO, not only a great glider but also a sport plane. With this combination, run time is a Very Long Time! Perhaps 30-45 minutes under medium power. I've never used more than half the pack before my back and neck got tired and I came down to rest.

But my LHS told me that the stock motor and the stock folding prop were very unsatisfactory and to plan to replace both of them in a short while if I bought the kit plane. That the motor is too heavy, requiring added weight on the tail for balance, and that it is typically short-lived. And that the stock folding prop pretty cheezy. They of course exist to sell stuff. But the owner is pretty straight with me, so I believe him in this instance.

So based on that and my experience with the brushless, I'd suggest that if you plan to fly this plane for a good while, that you get a suitable brushless, brushless ESC, and a good folding prop on order, even if it has to come in by sea barge to keep the shipping charges reasonable. By the time it arrives, most likely you will be ready for it. Perhaps order another Ascent kit at the same time, just in case.

But since this is your first R/C model, then it may make sense to just fly what you have and to just enjoy it till something happens. You could break or lose the plane rather easily in your situation. All planes are Doomed. You just don't know what or how their expiration date is! You may want something different the second time around.

I'm enjoying the daylights out of my brushless Ascent, but I have no idea how well it will hold up in the long-run.

Just my $.02