SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Oct 11, 2012, 03:31 PM
Lazy Builder
Joined Jul 2005
183 Posts
Discussion
Will It Blow Up?

Hello All,

I'd first like to state that I've done research about power systems, and it seems the more I do, the more I get confused. I've used WebOcalc and have made the best educated guess I could and now I ask all here, to let me know if it will blow up (Granted, I could use a multi-meter but there should be a non-experimental answer).

Model: GWS Slow Stick

Motor: Turnigy 950 Kv, 243 W max, 23.2 max Amps,

http://www.hobbyking.com/hobbyking/s...ner_Motor.html

ESC: Red Brick 30 Amp

Battery: 2200 mAh, 3S, 11.1 Volt, 25C

Prop: APC 10 X 5

Total Weight: Approximately 30 oz

Thanks to everyone for the help!

-Red

PS, If you need anymore info, let me know.
The_Red_Baron is offline Find More Posts by The_Red_Baron
Reply With Quote
Sign up now
to remove ads between posts
Old Oct 11, 2012, 03:39 PM
Registered User
Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
27,197 Posts
At 70g, ~210W is probably a more prudent maximum... but looking at these test results:

static tests on 3S:
Prop/A/W
8x6 8.3 98
10x6 12.5 140
10x7 16.2 190
11x7 21 230
13x4 21.8 240

11x3.8SF 16.2 190
11x4.7SF 20.5 225


a 10x5 should certainly be okay for it [in fact well below its rating!... it may well draw <12A]
Dr Kiwi is offline Find More Posts by Dr Kiwi
Reply With Quote
Old Oct 11, 2012, 04:06 PM
Lazy Builder
Joined Jul 2005
183 Posts
Thanks Dr. Kiwi, that makes me feel better.

I forgot to mention we are at an elevation of 8,000 ft.
The_Red_Baron is offline Find More Posts by The_Red_Baron
Reply With Quote
Old Oct 11, 2012, 09:32 PM
Registered User
Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
27,197 Posts
At 8000' I'd bet you can go up in prop diameter quite a bit and still not be over-taxing the motor.
Dr Kiwi is offline Find More Posts by Dr Kiwi
Reply With Quote
Old Oct 11, 2012, 10:22 PM
Registered User
scirocco's Avatar
Australia, ACT, Kambah
Joined Feb 2001
3,060 Posts
I used the D2836/11 that is in ECalc, then modified for Kv=950, and just tweaked the I0 and Rm a little, and got a similar 11x7 sea level current as Dr Kiwi's test data.

In eCalc, sea level to 8000 feet, same prop is a drop in static current from about 20.5A to 15.3A. The 10x5 estimate is only 10A at 8000ft.

I'd recommend the extra pitch because for the same indicated airspeed the wing is flying on, at altitude the prop is seeing a higher true airspeed and thus will want a higher blade angle/pitch speed.
scirocco is online now Find More Posts by scirocco
Reply With Quote
Old Oct 12, 2012, 10:27 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,853 Posts
The Slow Stick tend to pitch the nose up as power is increased because the motor mounting does not allow the thrust line to be set down and to the right a little.

A mount like this one will let you put some washers between the back of the motor and mount to get some thrust angle change:

http://www.horizonhobby.com/products...mount-EFLM1915

I used three flat washers on the top hole to get the down thrust and 2 on the left to get some right thrust.

The mount will work on a 16mm x 16mm or 16mm x 19mm hole pattern. You may have to shorten the screws a little to make sure they do not go into the motor more than 4-5 turns. If they go in too deeply they can damage or short out the windings.

Jack
jackerbes is offline Find More Posts by jackerbes
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Sold Thunder Power RC Car Lipo Packs BLOW OUT!!LOW BALLS above cost will be accepted!!!!!! purehobby Cars - Accessories (FS/W) 5 May 04, 2012 12:25 PM
Discussion Blow those cows up ! UlteriorModem Life, The Universe, and Politics 21 Apr 19, 2012 03:53 PM
Discussion Will my battery blow up ? marcolisi Batteries and Chargers 4 Jun 04, 2010 09:07 AM
Will this power system blow up? johnhay73 Power Systems 4 Sep 29, 2005 11:33 PM