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LECTROPILOT
02-07-2006, 01:41 AM
gotta hold of a 300 size pylon model and picked up a couple sp300 motors.......BTW am surprised how high they wind up!! anyway the spex say a max draw of 5 amps but when I go to motorcalc it sez with a 4.2x4 prop/3s 1320 lipo itll being drawing 19A, this isnt making sense and need some advice, anyone out thier playing with this size motor on d/d and what components are ya using

Jason T
02-07-2006, 03:28 AM
If the speed 300 motor is brushed then 5 amps sounds about right. Typically brushed motors this size will not handle the voltage a 3s lipo delivers. You should try a 2s lipo pack and it will probably still scream.

LECTROPILOT
02-07-2006, 03:56 AM
so are you saying anything over 5A is gonna fry it?? I have some 2s1500 @8C but even those will deliver 12A.....so now what???? prop down somemore??

Jason T
02-07-2006, 12:05 PM
I would run the numbers on a 2s and see what it says. Otherwise you will have to prop down. There are some bigger brushed motors that can take higher amperage but they are way too big for sp300 racer.

LECTROPILOT
02-08-2006, 01:22 AM
thanx for the info, I tried some 2s 1500 and they seemed to work w/o any strange odors coming from the motor:eek:

Elfi Flyer
02-08-2006, 04:15 PM
Graupner Speed 300 motors, from H/L, come as 6V and 7.2V. I have used the 6V motors in my Elfi's as a performance upgrade from Speed 280 stock motor. Of course there was 4:1 gearing, so amp loads were less than what you would see on direct drive. However, H/L rates the 6V Speed 300 amp range as 3 - 12, with 10 amps being a good workable level. I measured 11.3 A going into a 9x6 tri-blade prop, geared 4:1. I would expect a direct drive configuration to easily pull this amperage on props 6" and under. You can definitely smoke a Speed 300 on a 3S1P LiPo. I did this on a recent Elfi upgrade, using a TP 1320 3S1P Prolite Lipo. Never bothered to Wattmeter the power train. Just flew the plane, got one flight before the motor burned up. 9x6 tri-blade prop, 4:1 gearing.

Interesting to see H/L's spec on the 7.2V Speed 300. They claim 3 amps with a 4.9x4.3 prop, direct drive.

Note also that Graupner Speed 300's (actually Mabuchi) have some advance built in, so if you run them backwards via offset gearing versus pinion in ring gear arrangement (typical MPJet gearboxes), you can get lower performance, more heat, less motor life.

LECTROPILOT
02-27-2006, 01:27 AM
ya I found out the hard way with the 1st 300 I ran......stupid me hooked up a 3s and pooof, Im sure we all reconize that smell:eek: but got 2 new 300s for $5 ea. so cant complain too much :o so to make a long story short the system ran good on a 2s 1500 and 4.2x4 apc, am still amazed how high they turn up for a small brushed.BTW those stinkin 2 mm shafts will bend if ya look at'em wrong so a prop saver may be in order

Barfing Pumpkin
02-27-2006, 02:54 AM
...but got 2 new 300s for $5 ea. so cant complain too much...

Where did you find Speed 300's for $5 each??

LECTROPILOT
02-28-2006, 01:54 AM
someone was clearing them out ata swapmeet :)

Elfi Flyer
03-02-2006, 12:20 AM
Great price. SP300's usually go for about $18.

Twmaster
03-04-2006, 06:01 AM
Tower has the GWS 300's on sale for $5.41 each.

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LR3419&P=DS