Motorizing 1:72 MTBs and 1:350 ships

Hookay I'm on a roll.

Look up "boats" on the Sharper Image website

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search box. On the bottom of the page is a mini-speedster R/C racing boat kit. USD 19.95. Picked up a couple when I was Stateside last month.

The kit includes a 4 AA cell charger unit, Two transmitters (9V) and two tiny speedsters with sealed NiCad inside hull that can be charged from the charger (2-3 minutes charging to get > 10 minutes run time.)

The speedsters run off two motor pods that are cellphone vibrator motors I think. The props are the size of Revell's PT 109 props. I had been looking unsuccessfully for this size props for as long as the PT boat had been re-issued and I wanted to motorize one. Needless to say the size is ideal for other 1/72 MTB models too and that S-boote. Not only that. The kit includes a pack of 6 spare props, ideal to populate 3 shaft MTBs.

If you cut up a speedster to leave only the guts it is small enough to fit into the Tamiya 1:350 Fletcher. Needless to say the 1:350 capital ships will be dandy for RC conversions.

The Tx has a left and right button pads to switch on each motor. Each button has a top and bottom half, top for Fwd and bottom for Rev. The motor runs only when the button is depressed. So there you have your steering and Fwd/Rev functions.

The mini-speedster motor burps often because of signal weakness or whatever. If the motor can be latched on it can continue running without having to keep pressing a Tx button or worry about it getting out of range (30 feet) . The boat look much better if it continues to run on its own but will be slow enough for you to catch up and regain control should this happen.

Read my post on motorizing the Revell U boat for my ideas on how to improve the RC functions of cheap RC toy units like latching the motor ON. The mini-speedster is a very cheap unit and one cannot expect it to perform like their bigger and more expensive brothers. I don't want to have to buy special hardware installations to put everything (servos, links, speed controllers, etc,) together either. If I can motorize the plastic kits and have some degree of control however imprecise, I'm satisfied.

In MTBs with three props my solution is to use the forward direction wire to feed an OR gate whose output will drive the central prop's motor*. This way so long as either the left or the right motor is on the center prop will continue to rotate Fwd. Should both motors stop or be in Rev the center motor will stop.

*(Salvage a motor from a scrapped cellphone or if Canadian "Princess Auto" has a pack of 10 for CND 9.99.)
Reply to
PaPaPeng
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In article , PaPaPeng writes

In the UK our local cheapo "Everything a Pound" shop has single boats for, surprisingly, a quid. I bought one to play with, but the internal battery life seems only to be a couple of minutes rather than the 10 it says on the box.

Regards,

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Reply to
Moramarth

Guys,

Look up a German website

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that shows a number of plastic kits that have been moptorized.

Reply to
PaPaPeng

After cutting up one of the speedsters boats to look at the insides I was puzzled at why there are three wire leads to the minimotors. The three wires in this toy allow the motor to be rotated forward or in reverse. In the classic DC motor reversing the motor's polarity requires four wires from the battery to switch around to the two wires to the motor brushes.

An enquiry to another newsgroup had a reply suggesting brushless motors. Looks like this little toy is a lot more sophisticated than I thought.

------------------------ But of course. I don't know why I never thought of looking up what a brushless motor is although I have come across it enough times in the reading materials.

The URL

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gives a very clear explanation of the brushless motor technology involved. It does require three wire leads and its obvious how the direction of rotation is derived.

My problem is now how to wire a regular two pole mini motor that had been clearly labelled as a cell phone vibrator motor to work from the brushless motor. The general idea is that in a three propellar PT boat the two side motors will be from the minispeedster set up. My intent for the middle propellar is to OR the inputs from the two side props such that so long as one of them is rotating in the forward direction the middle prop will spin forward. I can steer without losing forward speed or use a rudder. If both side motors are idle or in reverse the mid prop will be idle.

Reply to
PaPaPeng

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