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Old Nov 01, 2015, 05:27 PM
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Help!
Reversing ESC. BRUSH TYPE ONLY.

I have the Blue Devil destroyer with 2 very geared down 20 mm motors Those old GWS motors in a 11 to 1 gear box.
On 3 volts the motors draw .7 amps
On 6 volts the motors draw about 1.5 amps.

What ESC could be driven off the 2 celled LIFEPO4 pack ?
Or do I need to separate the receiver & drive packs ?

If separate ? only the NEGATIVE leads are connected together ?

I would like to be able to run the motor on either voltage. Never used this small stuff. My small servo amplifier can not do the job. TOO twitchy at stop position.

Thanks
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Old Nov 02, 2015, 04:12 AM
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Mtronics Marine Viper 10. Small, not the worlds cheapest, certain to work.
The Chinese 10A ESC mentioned in many other posts. Cheap & cheerful, quite good control, in my opinion, has some issues with needing very stable voltage supply due to it appearing to go into a brown-out condition and staying there.
If using servo electronics, its best to forget the stick - just use the trim adjust slider as an engine room telegraph.
Both of the above have a built in BEC so will quite happily supply the radio from the main battery. Check out the "Electrical Discussion" thread in Scale Boats for wiring.
Invest in a voltage warning circuit for use with lithium. Probably two or three bucks.
I have doubts as to whether the model will perform like a destroyer with motors geared down that far, but thats just an opinion.
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Old Nov 02, 2015, 07:59 AM
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Old mind :)

02

I really have 12 MM GWS brush motors. Not 20 mm
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Old Nov 02, 2015, 01:50 PM
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http://www.ebay.com/itm/151543658741...%3AMEBIDX%3AIT

See the link above. Its the one mfr02 referred to above and one I have been using with similar setups and a 2 series lipo. Look at page 4 of the Lindberg Cape Class thread for a pic of mine.

You can't hook up a DC motor wrong, It just may not spin the way you want, and then you just reverse the leads. My set up uses counter rotating props, if yours doesn't just reverse what you see in my pic on one of the motors.

The ESC plugs into your rx and gets power from the drive pack, no receiver pack is needed.

I should also note, my set up delivers half the voltage to each motor. If you want full 7.4v to each you need to splice the feed wires and attach a red and black to each motor. Wire them in parallel, not series.
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Old Nov 03, 2015, 03:49 AM
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Quote:
Originally Posted by cyclops2 View Post
02

I really have 12 MM GWS brush motors. Not 20 mm
The nice thing about modern PWM controllers is that what will control a big one will also control a small one just as well. I still feel that to get it to perform like a destroyer, the right size motor on direct drive is the way to go, as is, the props will simply not turn fast enough to move enough water.
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Old Nov 03, 2015, 07:56 AM
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Good news.

The props throw up 2 beautiful turbulent sternwakes. Complete with the suction gurgles. Way too fast on WOT.
Use gearboxes to get maximum power with the least energy use. Done that for 30 ? years in planes & boats.

The 96 " WWII Higgins PTB has a Minnkota 40 pound thrust trolling motor in it. Still needed a 1 to 5 step up timing gear & belt set up to run right. The props are Prop Shop Naval Brass 5" diameter X 5" pitch with 5 blades. I cheated & only installed 2 of the props to drive it.


Baby PTB is under propped with only a small1/2" X ? pitch. Needs a larger & higher pitched prop.
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Old Nov 03, 2015, 04:36 PM
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As the scale gets smaller, to get the right performance, the RPM at the prop is required to increase. The baby PTB is a case in point. If the props are anything like scale and not making it perform, they need to spin faster. Less gearing, more direct drive.
A small geared motor would probably be great in the Lindberg tug with its supplied prop to move the hull with the right power, but a faster boat needs to move the same volume of water further in the same time. Time X distance is speed.
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Old Nov 20, 2015, 09:51 PM
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Finally !!

BP Hobbies standard servos arrived. Gutted them for just the small amplifier inside . Removed the motor & glued the servo pot at Neutral. The 2 GWS 10 to 1 gearboxes pull 1 amp at BEC voltage of 5.0 vdc . No load in air at WOT. Put the props in water.

TOO FUNNY.

The prop speed is the same as in air. So is the 1.0 amps at WOT in the water. The 2 A123 1100 ma cells are great ballast.

At WOT the prop water is boiling up behind the boat. Just like the USN destroyer I served on in 1960.

5 watts is way too much power for the dual prop Blue Devil.

Time to have all the Santas deliver lots of those small plastic boats. Again. Been 38 years since the last batch.
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