hansvonpensch

I have decided to, and have preceeded to, install 3, instead of 2, Graupner 700s, 12v motors in my 48" pt. The max eff, rating is 15 amps and stall amp rating of 43 amps. Can someone reccomend an esc which will handle 90 amps continues and 130 amp surge and handle 14.4 volts. Thanks, Randy. What would be the cheapest one.

FE_Chris

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rumrunnerracing.com

I am sure some of those dudes could help you better. I don't really think RCU has any resident FE boat experts.....

hansvonpensch

Anyone have any ideas. Thanks.

retaobcr

Something doesn't jive here. You want to run 3-9.6 700 motor on 14.4 volts on a 90 amp esc. I think the trouble with 3 -700's is the wiring probably is 12 gauge and if each motor maxs out at 43 amps, so you have at full speed 129 amp on a 90 amp esc. Answer, get a 820 Grauper or bigger and have to motors on a Castle 240 esc. Now a cheaper way is gas or nitro by a long shot. Time you buy lipos for 3-700 and have each motor on 14.8 or even running 12 cells for each motor = 36 cells at 2.4 ounces per cell = weight you don't need. You figure 12 ounces per motor. Somebody can finish this posting, it's out of reason.

electricalgod1

Hansvonpensch,

It sounds like your going through the same thing I did on my PT.

I now have each 12V Graupner 700 running on its own 11.1 lipo and a Proboat 2314 ESC.
I also stepped down a prop size to help reduce the current draw, only 19A at full throttle per motor.

I have got quite the collection of props, batteries, and burnt out motors.

Dino

rye

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hi
i use two of these for 2 hispeed 900 mzd motors worrk well each has its own 12 volt gelcell
http://www.modelcontrol.com/sc480.htm hope it helps rye

hansvonpensch

I would like to buy a Graupner 700 bb 12v motor, Anyone know where to find one in America, Thanks, Randy.

mfr02

Performance and cheap rarely fit together, especially in a large model.
The most economic way to control 3 motors is probably 3 ESCs each suited to the motor it is controlling, especially high power demand ones. They can work in sync by using a set of Y leads. If the 14.4 volts quoted is the charged voltage of a 12 volt SLA, then all ESCs that are designed for 12v SLA use will handle the voltage. This might be a good case for looking closely at brushless motors and their associated ESCs. And forgetting SLAs in favour of one of the lithium types.

hansvonpensch

Its been a while, I went with the 3, 700s 12v, 3 separate pro boas esc's with 11.1 lipos , it runs great, if I up grade I might go with 14.4v lipos, because I disconnected the bec on the escs I might be able to push more voltage on the escs.

mfr02

Unless you know what the internal arrangements of the ESC built-in BEC is, don't try upping the voltage beyond the stated limit.
The usual way of disabling a BEC is by disconnecting the red lead at the RX plug. The ESC has logic circuits that run on 5 volts. Guess where that comes from. The internal logic circuitry is almost certainly powered via that BEC from the main power, and it might not appreciate the extra volt drop.
Depending on internal component spec, the components driving the output stages might be getting near their power dissipation limits as well. Things should have improved, but I have rebuilt several of the old Hitec gold bricks where the owner thought an extra couple of volts was a trivial matter. Modern output transistors need less driving, but I would guess that the rating of the other components has been suitably adjusted to keep down size and cost.