Technical, Techniques, Hints, and Tips > DC Motors (Brushed) and Speed Controllers

More power reqd.

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Model Boats Website:
Lets go right back to the beginning. Tug asked the question how to get more power since his original setup
--- Quote ---Graupner 600 bb sp 7.2 Volts and running on 8.4 volts in a 3 foot torpedo boat
--- End quote ---
was not enough to get the boat to lift.

Torpedo boats have the same shape hull as Fireboats so I hope I can give Tug some helpful info about this subject.

First of all I started of with a standard 540 motor running on a 6v 5Ah Lead Acid battery, this moved ok but was not very fast and definatly no lift on the hull.

Second I tried a Groupner 600 motor also on the 6v battery, this made the boat a little faster but not a huge deal. This motors optimum voltage was 7.2v so I thought it a good idea to purchase a 7.2v NiCad battery for it. It went faster again which would be expected but no great speed.

The third motor I tried was a 777 motor from Model Motors Direct, it looked good on display but this was certainly a down grade of motor which was even slower and heavier than the 540. The one advantage it did have is that it drew less current than the other two but was no good for the speed I was looking for.

I then went back to the Groupner for a while, until the NEC model show last year. The model show exibited all sorts of models, very few boats in comparison but displayed many brushless motors in all sorts of models. This show made me realise just how good these motors were since they consume less current and run much faster than ordinary brushed motors.

I purchased a motor at this show and tried it out, it was powerful enough to get the boat to lift just on the 7.2v NiCad and it still has a capability of going up to 15v which would double the speed again! The speed is now running speed as opposed to walking speed and there is no need to apply a bigger voltage since the boat would probably flip anyhow.

Tug asked the question,
--- Quote ---Prey tell, what brushless combo is a directly comparable to say a 545?
--- End quote ---
Well I searched the internet to try and find the best comparison as possible. A 545 motor runs at 750RPM/v the nearest motor I could find to that was the Kontronic KBM 67-07 brushless motor seen on this page:- http://www.motocalc.com/data/motor.html but to be quite honest that is only a speed comparison and the chances are the brushless motor will run much cooler and weigh less.

Brushless motors are approximatly 3+ times faster than brushed motors and currently holds the fastest model speed boat record (120.7MPH!).

If you need to know more on the difference between brushed and brushless motors try this link :- http://www.modelfireboats.co.nr/ue/motors/types.html or contact me via the website.

Stephen.

HS93 (RIP):
  Try ringing radcliffemodels

http://www.radcliffemodels.com/shop.php?category=Motors&subcat=Brushless

I rang them and got lots of info , they race boats with this type of motor  and seem to know what they are talking about,It seems its not as straght forword  to compare motors  (brush/brushless)

Peter

Fast Electricals:
My first boat was a similar shape and size to the one described. The original motor was a Speed 600 which gave quite disappointing performance and ran extremely hot. Upgrading to a 12 cell setup and using a 9.6v 700BB turbo motor produced loads of power and really transformed the model. I would certainly recommend this motor for fast scale applications as a cheaper alternative to brushless motors.

Tug:
 Hey well explained Stephen, lots to go on there, which motor did you settle on?

For now thanks to Fast Electricals cheapest option is the 700. so I will go there first.
The hull is not straight enough to warrant the expense of 'proper motors'

But for the next one.......  yes there will be one.

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