48chebbie

My Feedback: (58)

ok folks,need a little help. i have a large (60" long) coastguard cutter ship,that i will be putting the drive in soon,and i am planning on using 2 multiplex 19T speed600 long cans,geared 3.5 to 1 and suitable props. anyway,my question is,if i run these motors wired in parallel,how big an esc will i really need cosidering they are geared,or, will my choice of motors/gears,wired in series be enough to power my boat well enough. the whole question here is really about the esc. i just don't think these 2 motors geared will pull all that many amps,regardless of there turns? any ideas?????

LtDoc

48chebbie,
The best way of determining how big of an ESC you will need is to do a 'stall' test on one of your proposed motors. Double that figure and you will have the minimum current rating for the ESC, if you wire the motors in parallel (wouldn't recomend in series, although it will work).

Gearing the motors does reduce the amount of current compaired to a direct drive, but even with the gear reduction a 19 turn motor will draw quite a bit more current than a campairable motor with more turns. That's one of those "(I^2)R" things, and it's just that way...
- 'Doc

48chebbie

My Feedback: (58)

more of what i am getting at is,for example,i build alot of custom clodbuster monster trucks,which run 2 motors,in parallel,and evryone for years have said you have to run a novak superrooster,with anything hotter than stock motors,like 2 16-17 turn mods. a SR esc says it will handle 2 15turn mods,no more. well i have news for the entire world. i have been running old futaba 112's,novak explores,etc. for many years on 2, 17-19-27turn motors,and have never smoked one,even running the truck wide open,slow,crawling,battery pack after battery. now,just like a geared boat prop,these trucks run through gearboxes as well. seems the whole number of turns for the esc is out the window at this point! i mean,i have a couple of super roosters lying around,but,i would rather use one of the hitec boat esc's,or something a little less elaborate. any ideas or thoughts???????

LtDoc

48chebbie,
The number of turns in a motor doesn't tell you anything about the current draw of that motor, which is what you have to know to determine how large an ESC to use. ESC manufacturers who rate their ESC's by the number of turns they will handle are not telling you anything useful. It all boils down to how much total current an ESC can handle for an extended period of time. If you don't know what the maximum current draw of the motor is, you really can't make an intelligent decison about what ESC to use. Do the 'stall' test with one of the motors you'll use. Double what ever that amount was, and you have the total current draw for two motors. The ESC should be chosen so that whatever that total current was, is less than the ESC's maximum current rating. The number of turns in the motor has nothing to do with it. Simple as that...
- 'Doc

48chebbie

My Feedback: (58)

thanks for the help,doc.

Tachikaze

Wait a minute, lets step back and look at what you want to do again.
You want to place a 19T 600 set of motors into a 60" boat and gear those motors down to 3.5:1?
No matter how you want to gear these, the 19T motor is suck the drive battery dry quickly. I run twin motors on all of my warships. They are wired into parellel and they are direct drive.

The INS Alfredo Oriani is just over 57" and runs on two Pittman 24V motors on a 12V battery connected to an early model MCD Super Minicon ESC. This boat will cover 100ft in just over 30 sec. If I wished to increase the speed of the boat I could add a pair of 14V Pittman motors on the same system. These are high RPM motors with low amp draw. By placing them on a lower voltage I can decrease the output speed and utilize far less amps than with the high amp draw motor that you are looking at using with a gear system to decrease the speed.
Here is a link to All Electronics where we often obtain motors. I also obtain a lot of Pittman motors from the bioengineering departent at the hospital where they take them out of repaired equipment.
[link]http://www.allelectronics.com/cgi-bin/category.cgi?category=400&item=DCM-216&type=store[/link]

pompebled

Hi 48chebby,

You don't want screaming gears in your 60" boat...

Apart from the noise, the power consumption is too high.

Go with direct drive, use motors, that rev 3000-4000 RPM.

12V fan motors (cooling the radiator) from cars are ideal powerplants in big boats, quiet and lots of power, not to mention cheap at the scrapyard.

A 35A ESC should be sufficient. (if in doubt, fit the motors in the boat, tie the rear to the wall, give full throttle and measure the amps that flow)

Best regards, Jan.

LtDoc

Or maybe even simpler, clamp the motor in a vise, the shaft in a pair of padded pliers, power the motor and read the stall current. (Standard 'stall' test.) That's the current you have to plan for.
- 'Doc

pompebled

I'm glad I learn something new everytime I visit here.

Greetings, Jan.

harrya1

Has anyone used the new Krylon paint for plastic on there hulls?