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Old Jul 01, 2014, 10:30 PM
George Jure
Hamilton, Ontario
Joined Aug 2005
273 Posts
Question
Old Radio System with New Main battery

Hello

I have a PT boat which is setup with a Futaba 4 ch. 75mhz FM radio system. The boat also has an OLD Dumas servo operated mechanical speed control. It has dual brushed motors, dumas and I would like to replace the speed control for ONE electronic speed control for both motors and I would like to use a Lipo battery 7.4v 2C to power the boat.

My questions are:
1) Can I run a lipo battery with this old radio technology safely?

2) What strong ESC can I buy that will handle both brushed motors and work off of a Lipo battery?

Any wiring with fuse protection diagrams would also be appreciated.

Thanks for your help.

George
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Old Jul 01, 2014, 11:25 PM
Submarines, etc.
tsenecal's Avatar
Arvada, Colorado
Joined May 2005
1,574 Posts
George,

1) yes

2) how much do you want to spend?


that might sound a bit lame, but we really need to know more about the boat and motors. what size is the boat, what size are the motors, and what size are the props.
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Old Jul 02, 2014, 05:25 AM
Registered User
Bradford West Yorkshire, UK
Joined Apr 2010
1,592 Posts
Try these people George :- http://www.action-electronics.co.uk/ , whatever you want to control, there's likely to be a diagram for it.

Regards Ian.
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Old Jul 02, 2014, 11:21 PM
George Jure
Hamilton, Ontario
Joined Aug 2005
273 Posts
Quote:
Originally Posted by tsenecal View Post
George,

1) yes

2) how much do you want to spend?


that might sound a bit lame, but we really need to know more about the boat and motors. what size is the boat, what size are the motors, and what size are the props.
Hi
Thanks for the reply. The PT boat is a Lindberg PT109 1/32 with a Dumas running package in it with the OLD mechanical speed control. As for prop size, from my tape measure, it looks like 1 1/4" dia. two bladed plastic WHICH for sure has to be changed to brass 3 bladed props. I want to still use the Radio gear and brushed motors. So I need a Speed control that will work with Lipo and what 3 bladed props to use.

George
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Old Jul 03, 2014, 03:27 AM
Registered User
Blackpool, Lancs
Joined Feb 2006
2,845 Posts
Test with a meter to figure out the current draw, double that, use the next available higher rating to get an ESC from a non-oriental source. If going oriental, move the decimal point in their claim one or two places left. Any ESC will be quite happy with LiPo, but it might need a low voltage warning device added, since LiPo do react badly to over discharge.
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Old Jul 03, 2014, 04:30 PM
George Jure
Hamilton, Ontario
Joined Aug 2005
273 Posts
Quote:
Originally Posted by mfr02 View Post
Test with a meter to figure out the current draw, double that, use the next available higher rating to get an ESC from a non-oriental source. If going oriental, move the decimal point in their claim one or two places left. Any ESC will be quite happy with LiPo, but it might need a low voltage warning device added, since LiPo do react badly to over discharge.
Hi, Thank You mfr02 for the tips. Good lessons for the ESC and the lipo.

George

Any idea what size of 3 bladed brass props I should use for the PT boat?
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Old Jul 03, 2014, 06:04 PM
Submarines, etc.
tsenecal's Avatar
Arvada, Colorado
Joined May 2005
1,574 Posts
for that boat i would recommend a pair of 30mm 3 bladed props, maybe even a pair of 27mm. the props you have now are 32mm. i buy my brass props from http://cornwallmodelboats.co.uk , you will have to verify what size shaft you have, and buy accordingly. I assume since everything else is Dumas, your propshaft is probably not metric.

to be honest, i don't have a recommendation for a brushed ESC. the last model i bought was in 2005, and it was a mtroniks. don't know about their current models.

i did find this one at hobbyking, but i don't think it has a high enough amperage to run both motors. it is probably cutting close

http://www.hobbyking.com/hobbyking/s...Search=brushed
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Old Jul 04, 2014, 11:09 AM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
4,792 Posts
The ESC Tsenecal linked to is used widely in scale boats and gets good reviews.

Two 500 size motors may be on the edge, but you could put a small fan on top (like the similar sized car ESC's) or add watercooling by adapting the heatsink to accept a piece of square aluminum or brass tubing with nipples glued/soldered onto it.

Regards, Jan.
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