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Help with brushless conversation - Graupner Systems Cat

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Help with brushless conversation - Graupner Systems Cat

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Old 04-12-2019, 12:15 PM
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sleeper341
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Default Help with brushless conversion - Graupner Systems Catamaran

Hi, Iíve just dug a Graupner Systems Catamaran our of my loft. I want to convert it to brushless but havenít a clue about brushless systems. Iíve been running nitro cars for 30 years, and back when I was younger I ran brushed boats. Brushless is new to me.

The Graupner Systems Catamaran has 2 720ís that run through a Graupner 606 gear box to a single flex shaft. What would be a good brushless set up to swap out the old brushed system? Could I drop 2 brushless motors straight on to the 606, each connected to their own ESC with their own lipoís hooked on to a Y harness in to a single receiver?

what size brushless motors should I go for - given that it is a boat from 1988 (approx) Iím sure it canít take anything too powerful but I want to get it running fast.

any help is appreciated.
thanks

Last edited by sleeper341; 04-12-2019 at 12:45 PM. Reason: Spelling error
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Old 04-14-2019, 04:15 AM
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Appowner
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Brushless adds a whole new way of thinking about it all. And I could hardly help with a plane let alone a boat. Mainly because the prop in use plays into the final decision. My suggestion is to contact a hobby shop or brushless distributor that specializes in boats and ask them. Personally I'd probably go to your side of the pond and ask someone like Cornwall Models. Just be sure that if you ask someone, you also buy from them. Just good business.

Just knowing what boat it is, a good distributor can probably recommend a complete brushless drive train for you. Including motors, ESC's, props and shafts.

Some of the things you might need to know before contacting anyone:
Brushed motor size just for reference.
Gear box ratio.
Approx RPM of both motor and prop with the brushed motor.
Prop size, diameter and pitch. (probably a very small pair of numbers molded on one blade).
Battery type and voltage you wish to use.

And just to be sure, you do know that brushless have their own unique speed controllers? You can not use a brushed ESC on a brushless motor and vice versa.

One thing to add, brushless are shown with a 'KV' value (pronounced Kay Vee). This is the rpm per volt you can expect when unloaded. IOW, a KV of 1500 is 1500 rpm for each volt of battery. So a 7.2 pack would deliver around 10,800 rpm at the shaft.

Don't worry, it gets more confusing before it gets better.

Last edited by Appowner; 04-14-2019 at 04:29 AM.
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Old 04-16-2019, 06:58 PM
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The Graupner drive system was known to be relatively weak with brushed motors. I am afraid that if the OP simply replaced his brushed motors with appropriate brushless motors and LiPo packs he will shred the gears in short order. The best solution is to replace the twin drive with a single motor in direct drive. Simpler, cheaper, more reliable, faster. The biggest change would be fitting a single motor mount.
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Old 04-17-2019, 12:26 PM
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Maybe in the UK it would be a "conversation" Here in t he US of A, it is a "conversion"!
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Old 04-18-2019, 10:09 AM
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Originally Posted by EloyM@twc.com View Post
Maybe in the UK it would be a "conversation" Here in t he US of A, it is a "conversion"!
itís a typo. I did try and edit it a few times the minute after I posted, but it wouldnít change.
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Old 05-18-2019, 11:59 AM
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You can run the system with a 3674 - 2200kV motor and 4S battery
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