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esc size

Old 03-14-2009, 04:01 PM
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rye
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Default esc size

hi
i have a 44" boat with two graupuer 700 bb motors need a esc with rev and water cooled runnning a 12 volt gel cell 7 amps thanks rye 332
Old 03-14-2009, 06:01 PM
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Tony Fitzpatrick
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Default RE: esc size

HI rye.

I have no concerns about an esc if it was watercooled and had a temperature overload feature.
A 7 ah gel cell battery is going to take a hammering and will not last a season.They are not designed for the discharge rate you are going to get.

By the way, those air cooled escs that quote the 100+ continuous amps you will need - the ones on ebay.They will not even run a single 700BB.

Tony Fitzpatrick
Old 03-14-2009, 06:03 PM
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Default RE: esc size


Hi Rye.

Time for you to get a Killer ESC. If it is still available.
Novak reversing Super Rooster.......... Impossible to destroy.
Has a adjustable delay at neutral. DOES handle a Minn Kota 44# thrust trolling motor. Able to blow apart 100 amp auto fuses when the baterry is connected BACKWARDS......

Rich
Old 03-14-2009, 10:37 PM
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rye
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Default RE: esc size

so that esc will hanlde two 700 and 12 volt gelcell 7amps
Old 03-15-2009, 05:51 AM
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pompebled
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Default RE: esc size

Hi Rye,

If you can't find a (afforable) ESC rated 100A with reverse (and watercooling) you might consider getting one for each motor and use a Y cable to get the signal to them.
35 -50 A should be sufficient, watercooling is always a good idea.

I have to agree with Tony Fitzpatrick on your powersource, that battery will suffer; getting out of the hole, a 700BB can easily draw 35A ( x 2=70A ), once on the plane the ampdraw will be 15-20 A per motor, making a power consumption of close to 500W continuously, that's five times what your battery can deliver...

Two 12 cell packs of Sanyo 2400 RC (one per motor) would be a more battery friendly solution (or Lipo's ofcourse)

Regards, Jan.
Old 03-15-2009, 10:18 AM
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rye
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Default RE: esc size

hi
ok thanks any web pages or links so i can get this stuff thanks rye
Old 03-15-2009, 10:35 AM
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Default RE: esc size

I picked up a Kontronik 70 amp 6 - 24 volt for $70 just before Christmas.
Old 03-15-2009, 11:00 AM
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Default RE: esc size


Rye

What shape is the boat ?
Old 03-15-2009, 11:43 AM
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The place that I bought The 70 amp ESC is www.offshoreelectrics.com
Old 03-15-2009, 04:36 PM
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rye
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Default RE: esc size

hi i am using the pt boat design but only 44" long scatched build top i was thinking of this one
http://www.offshoreelectrics.com/pro...p?prod=dh-3020 but can i use just one 12 volt gel cell i have the boat wired and battery case in already thanks rye
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Old 03-15-2009, 04:40 PM
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rye
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Default RE: esc size

or this one
http://www3.towerhobbies.com/cgi-bin...&P=SM&I=LXJAC0
Old 03-15-2009, 04:53 PM
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pompebled
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Default RE: esc size

Two of these (one for each motor) would work aswel and costs a lot less...:
http://www.r2hobbies.com/proddetail.php?prod=rcps61604

Regards, Jan.
Old 03-15-2009, 05:51 PM
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Default RE: esc size


Looks good to me at $14 USA X 2 . Would need a seperate BEC , maybe. 1 amp is low for rudder size ?
Still. Good price. Are they available in Canada or the USA ?
Old 03-15-2009, 05:53 PM
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Default RE: esc size



Nice looking PTB.
Old 03-16-2009, 11:36 AM
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Default RE: esc size

Rye,did I say I have no concern on the esc but then made a remark on the battery? I now see the shape of the hull. [X(]
Two things.....

You have not mentioned what radio set you will use.I know what will happen if you pick up a "full reverse"

I've built a few pt boats in various scales and hull shapes.I've sailed them with different batteries.I'll eat my hat if that boat gets up on a plane with a 12volt-7Ah battery.If you direct drive suitable props for the 700bb the boat will point up at 45 degrees and draw upwards of 30 amp per motor.

Tony Fitzpatrick
Old 03-16-2009, 03:44 PM
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Default RE: esc size


Do you want a close to scale speed. Or as much speed as possible ?
Old 03-16-2009, 04:45 PM
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Default RE: esc size

no just crusing the pond ,i have the dolls in the rear on a servo driver and a ipod and 16 led light so i want to see all this stuff working i us the 700 because i had them and 2 three blade dumas left and right props 2" i just need a esc forward and rev dont need a lot of speed just crusing speed on my 5' pt boat it has two sc-480 esc and two 12 batterys two 900 she get up on plane for about 15 minutes 25-30 munites running time as syou can see on youtube thanks rye
http://www.youtube.com/user/ptboat84
Old 03-16-2009, 05:31 PM
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Tony Fitzpatrick
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Default RE: esc size

After searching,I saw a PT boat on a leasurely stroll

Note that a 900 motor is almost like a 700 with a gear reduction.You can stick a big prop on the 900 and it will grip the water and shift a displacement hull,not dig a big hole to the rear of the transom.
If you were to put large props on the 700bb and can't get it skimming with motors turning at several thousand rpm then the motors,escs and battery will be effed.

I think your 900 motors are a better fit for your cruiser and you could increase on the props until the revs fall to half the free running figure.Perhaps even up the voltage and watercool them.

Tony
Old 03-16-2009, 07:55 PM
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Default RE: esc size


Do you really need 2 ESC's ? Have you tried the 2 motors on 1 ESC ? It should do fine at reduced volts & current . Temporarly use the PTB ..ESC . Should prove out Volts & amps of the 2....2" props needs.
Old 03-16-2009, 08:54 PM
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rye
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Default RE: esc size

yes ok we are back to what i frist ask which esc can i use with the 700;s and one battery as for changing motors no way to much work but i may try bigger props for the pt boat in the spring when my summer place opens , thanks rye
Old 03-17-2009, 11:33 AM
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Default RE: esc size

ORIGINAL: rye
Yes ok, we are back to what I first asked: which esc can I use with the 700;s and one battery? As for changing motors no way, to much work. Thanks, rye
Hi Rye,

If you put smaller props on the 700 motors, one ESC like the one in my link should work fine, just puttering around with the party crew on board.
The system would be far from efficient, but if you don't want to change to a 700 motor that's less amphungry, that's your choice.

Regards, Jan.
Old 03-17-2009, 05:03 PM
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rye
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Default RE: esc size

hi jan
ok i think i am going with this one ,is one enough i am going to drop the props two 1.75
http://www.r2hobbies.com/proddetail.php?prod=rcps61604 would change the motors but the motor mount is one of the ribs and the holes are cut and mounted ,so i wont need a battery park for the reciver with this one and how would i water cool this esc what do you think ,thanks rye
Old 03-17-2009, 05:22 PM
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Tony Fitzpatrick
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Default RE: esc size

Just the one I was talking about when I wrote this:
ORIGINAL: Starkbone McGarvey

By the way, those air cooled escs that quote the 100+ continuous amps you will need - the ones on ebay.They will not even run a single 700BB.

Tony Fitzpatrick
It has an instantaneous current trip that gets triggered by a single 700 motor on 12 volt.

Add to that,the internal resistance,less cable,is about .008 ohms so I think the other reply posters on this thread can tell you the veracity of the continuous 110 amp current rating ( complete rubbish!)
The bec at 12 volts would not help matters.
Tony
Old 03-17-2009, 06:37 PM
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rye
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Default RE: esc size

o i give up
Old 03-17-2009, 06:59 PM
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Tony Fitzpatrick
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Default RE: esc size

You need one of these if you ever want to use those 700s
[link=http://business.shop.ebay.com/items/?_nkw=clamp&_sacat=58277&_fromfsb=&_trksid=p3286.m270.l1313&_odkw=&_osacat=58277]clamp meter[/link]

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