Question About LS Purpil Peril Setup Issues - RC Groups
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Jun 23, 2007, 01:35 AM
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Question About LS Purpil Peril Setup Issues

I recently purchased a LS PP based on the many great reviews. The challenge I'm having is the motor is getting very hot when I run it at 1/2 throttle and at one point a little smoke (from heat shrink?) came out after a 1-2 min test run.

3s Lipo 11.1V , 2200mah
25A Eflite Brushless Speed Control (Auto Setting for Motor)
Airplane is Soarstar (20oz plane)
Prop is Standard Prop 8x4 Pusher
Direct Drive Setup with Prop adapter

1) Some skipping around 3/4 throttle but smooth when I did full throttle tests for few seconds.
2) Heat seems to build up with anything near 1/2 throttle or over. (Very hot can't touch after running for 1-2 min)

Possible Causes:?
1) I thought a motor wouldn't pull more from a larger speed control vs smaller. I knew 25A was more than I would need, but I like the heat sync on larger speed controls as they seem to last longer. Is this false? Should I stick with an 18A or 16A controller?

2) Should I change the 8x4 stock prop over to a GWS 8x4HD?

3) Does a pusher change power consumption vs a pull?

4) Does the weight added by a prop adapter change power draw vs prop saver? Everything I've read said you should run this motor with a prop adapter if hitting the 160W limit area.

5) Is there a wire length limit between controller and motor? I'd guess my lenght is 6-8".

I'm hopeful that the motor hasn't been damaged as it still seems strong, but I'm concerned that it might burn up in a 5-10 minute run during full flight. I didn't see any warnings on this motor about static testing on ground like some of the higher end LS, but maybe I missed that detail.

Thanks for any advice...
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Jun 23, 2007, 03:10 AM
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Bruce Abbott's Avatar
1) Prop too big and/or inappropriate ESC timing
2) Not enough cooling airflow. I hope you weren't ground testing it for 2 minutes

Possible Causes:
1) No. It does no harm to have a higher rated ESC
2) Yes (better yet, change to a 7 inch or smaller prop)
3) No
4) No
5) Yes, but 6~8 inches should be OK

The PP is small motor with relatively high Kv, so it is easy to overload. It relies on good airflow to get rid of the heat generated. This shouldn't be a problem if your model flies fast and the motor is out in the breeze. Static testing for long periods is not advisable, particularly with a large prop.

An EP8040 is OK if the model flies fast enough to get good cooling and significant prop unloading. However, the Soarstar is fairly draggy so you will have to be careful. Don't try climbing steeply at full throttle for a long time.

I'm afraid your motor may be damaged. Once the magic smoke gets out it's very hard to put back in! However, if the motor runs smoothly and still has good 'cogging' (ie. magnets still strong) you may have gotten away with it, this time...
Last edited by Bruce Abbott; Jun 24, 2007 at 12:56 AM.
Jun 23, 2007, 07:12 AM
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flypaper 2's Avatar
Motor with a pusher prop gets practically no cooling from the prop. Best thing is to fly it then check the motor heat. Mine run fairly hot in the air with a tractor prop but I'm using slightly larger prop.
Jun 23, 2007, 08:34 AM
uhhh....this thing on?
skyking1231's Avatar
a little smoke ????

RC elec equipment runs on smoke....if you let the smoke out...they stop working.

I have a LS PArkjet...which smoked on me. It wasn't the amp draw that killed it. Because this was the about the 30th flight on that setup....and it smoked about 10 seconds into the flight. What i think it was either a piece of metal that go into the motor....or me screwing around with the ESC programming (timing), or current settings.

I sent it in and got a new one for 20 bucks.
Jun 23, 2007, 10:14 AM
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mike3976's Avatar
The challenge I'm having is the motor is getting very hot when I run it at 1/2 throttle and at one point a little smoke (from heat shrink?) came out after a 1-2 min test run.

Dude, It's not a very good idea to run any motor static (not flying) for more than brief periods (15 sec.) This is especially true when you have a set-up that is pushing a motor to the limits of its design.

Dont worry about how it performs on the bench, but be concerned with its flight performance.

A pusher design will cool itself to a much higher degree in the air moving at speed, than sitting on the ground.

Now go fly the damn thing!
Jun 25, 2007, 09:52 PM
Registered User
Okay I got it flying great... (right up til the point where my wife flew it into the top of a 100 year old Pecan tree..) Here is what I did to 'fix' my heat problem: (Thanks Bruce your advice was right on the money)

1) Reduced 11.1 Volt to a 7.4 Volt 2000 mah Thuderpower rated at something crazy like 20 or 25C. I was worried about the plane being underpowered, but dropping the voltage didn't seem to impact speed at all.

2) Changed the timing to 2 Pole Motor (Is LS a 2 Pole? what does this mean?)

3) Changed the Battery to 2S Li-Po for cutoff

4) Dropped the blade down to 7x4 (vs stock 8x4)

The 'burping' went away and she flew great. The only challenge was the plane seemed to fly a little 'faster' with the smaller prop (higher spin rate?). Performance, takeoff, everything was great right up until the incident 50 feet up with the Pecan tree

Back to building my tennis ball launcher to blow it out of the tree...
Jun 27, 2007, 12:16 AM
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methos's Avatar
That is very strange cbhelo.
I say this because I've had my PP setup as a pusher on a depron pusher jet and I currently have setup as a tractor on my EPP combat plane. In both setups I have ran it on 1700mAh (advertised as 20C) with a 25 amp ESC and a GWS DD 8x4 prop and I have never had any overheating problems.

Me and Flypaper run the snot out of our Purple Perils WOT from take off until the battery dies and they never get very hot.

I think your setup was fine, I just think you static tested it WAY too long like Mike said.
Unless you are doing serious testing and don't care about frying the motor, I would never run it static for more than a few seconds.

Jun 27, 2007, 03:52 PM
Registered User

DD vs Stock?

I'm a complete newb on planes... built this one for my wife. (per my tag)

You all are probably right, and I wouldn't have been so paranoid... except I bought a GWS outrunner that burned up when the plane was 50 feet off the ground and my wife had to land dead stick. (Her first landing and no damage woot) I got some really bad advice from a local Hobby shop and the GWS was in NO way rated for a 8x4 @ 11.1 volts. This made me paranoid about 'burning' up my second motor hence all the static testing.

I did buy a 8x4DD and I noticed it has a lot less 'scoop' to it than the standard Soarstar prop. Maybe the extra scoop also loaded the motor down.

Are you running 11.1 volts or 7.4? I'm pretty sure I could run the 8x4DD with 7.4 volts. (I have a LOT of Heli batteries in the 11.1 range hence the reason I kept trying to use that range.) (For those of you as new as me the DD stands for Direct Drive aka there is no gearbox between the prop and the motor.)
Jun 28, 2007, 11:27 AM
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methos's Avatar
11.1v or 3 cell 1300 mAh Lipo battery with the 8x4 DD prop and I run it wide open from take off to landing and the motor only gets warm.
Jul 01, 2007, 01:56 AM
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Recovery complete

Thanks for the tips Methos. I 'shot' the plane out of the pecan tree today with a 110PSI air cannon / tennis ball. Good news is the motor and all the electronics look good. As soon as I get a new stabilizer kit, I'm going to try out the 8x4DD with 11.1.

Any idea why the motor would 'skip' at 3/4 throttle with the 11.1 and not the 7.4volt lipo?

Thanks everyone for the tips you all have been great.
Jul 01, 2007, 11:46 PM
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mike3976's Avatar
2) Changed the timing to 2 Pole Motor (Is LS a 2 Pole? what does this mean?)

Change your esc's timming setting to high!
Poles are the no. of magnets, your LS has 9
This may have something to do with the motor "skipping"

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