motor and gearbox

[Red_Hamish]

Hello all, I built this kit on friday night and have not had a chance to try it out yet. It is a 3vmotor running at 12000rpm no load and with a gearbox of 288:1 takes it down to approx 40 rpm. Which i think would be ideal for the small (18"x5" or so ) Paddle Tug Tipstaff the free plan from Modle boats magazine. Will now have to build a pair of wheels and a test rig. I will let you know how it goes.

cheers

Jim

p.s. any advice welcomed.

[Eddy Matthews]

Great to hear your having a go at a paddler Jim....

My own feeling is that a speed of 40RPM will be too slow though - Most of the models I've seen tend to use paddle speeds of up to 120RPM with 80-100 being the most common.

After saying that, I've never seen a working model paddler as small as you are building, so maybe it will work? Trial and error seems to be the order of the day - Please keep us informed on your progress, it certainly sounds interesting...

[mjt60a]

I would have said about 100rpm at cruising speed too (with maybe about 130 available for emergencies). That looks similar to the motor/gearbox I put in my PBM model, I found it made no headway against the wind at all when set up as standard - but it was a simple matter to exchange the 'driven' wheel on the output shaft with the red one (so the green and red gears do nothing) or replace the red and green with lengths of tube as spacers (using only three gears) to increase the speed of the paddles...

[Red_Hamish]

thanks Mick for the warning, I've tried it out on the plans and you are quite correct. This is not going to be anywhere near powerful enough for the job intended. So it is back to the drawing board again.

cheers

Jim

[rva1945]

Hi guys:

I'll build the Chieftain, 1/50 scale, which gives a 26" x 4.5" model, and I will install the 70168 Tamiya double gearbox:

http://www.pololu.com/products/tamiya/0114/

I'll choose the 12.7:1 ratio, which, with the motors running at 10000 rpm will spin the wheels at almost 800 rpm, although at half that speed will be enough.

Or will it be underpowered (low torque)? Should I choose the 38:1 ratio instead, to have 10000/38 = 263 rpm?

Any help or experience about that?

Regards

[mjt60a]

I've got one of those twin motor/gearboxes (it was from a tamiya tank model) with 3volt motors and about 260-ish rpm at the output shafts. I'd planned to use it with a pair of belt/pulley sets at 2:1 to give 130rpm paddle speed - but I haven't tried it yet...