RC Tank Warfare community hobby forum

I have added a resistor in series to the power goign to the turret motor. I believe the color coding was red-red-black. It is very low ristance, did not want to reduce the motor's torque to where it won't turn the turret. With the resistor in line, a 360 degrees rotation takes exactly one full minute. As this is on my Sherman (yeah, I used a HL turred motor assembly and ring gear) it is a bit fast but far closer to real speed. And the slower turret rotation looks far cooler....

Hi folks,

Just adding a bit of science to the above post!

Had a quick off-load (no turret) test of my WSN T-34. At 5v, it took ~200mA. This implies a motor resistance of ~25 Ohms.
The resistor Dmon has used is 22 Ohms. Hence this is approximately halving the voltage to the motor. Halving the voltage will generally halve the current taken by the motor and hence quarter the power.
My turrets generally take ~15s to do a full 360 degree turn (I've noticed), so Dmon's quartering of the power increases the time to rotate the turret by 4.

Bloody hell, the numbers add up! Wahoo! all that education was worth it after all....!
::)
My only worry is that the power handling of the resistor may not be up to continuous turret rotation. A power calculation gives:

P = I^2 * R = 0.1^2 * 25 = 0.25 Watts (NB current halved from 200mA to 100mA)

So you need at least a 1/4 Watt handling resistor to make sure it doesn't turn your Sherman into a true "Ronson/Tommy-Kocher"



Nige

Wow that was way too much technical talk for me... either that or I've accidently reset the language on my profile page   

I'm really not very electronically minded but I fancy giving this a go. Is it just a matter of finding the right wire, cutting it and soldering a suitable resistor in line? If yes, is there any chance of telling us what wire it is. Pictures with large arrows saying "CUT THIS WIRE HERE" would be most welcome and not thought to be at all patronising 

I think all you have to do is twist about three of these together in parallel and they will handle the wattage.

Well I'm sure we all remember Kirchoff's laws, don't we?

Resistors in series: R1 + R2 + .... Rn = new resistance

Resistors in parallel:  1/((1/R1)+(1/R2)+...+(1/Rn)) = new resistance

Therefore 3x  22 Ohm resistors in parallel works out at.....22/3 Ohms, so about 7 Ohms.

Thus to get 22 Ohms at the end you require 3x 66 Ohm resistors. The nearest standard value is 68 Ohms.

Nige

NigelDerEnglander wrote: Well I'm sure we all remember Kirchoff's laws, don't we?

Resistors in series: R1 + R2 + .... Rn = new resistance

Resistors in parallel:  1/((1/R1)+(1/R2)+...+(1/Rn)) = new resistance

Therefore 3x  22 Ohm resistors in parallel works out at.....22/3 Ohms, so about 7 Ohms.

Thus to get 22 Ohms at the end you require 3x 66 Ohm resistors. The nearest standard value is 68 Ohms.

Nige

Really???

Holy smokes it has been a long time out of school, but I thought resisters in parallel made no difference in the resistance,  I have twisted two together, and never noticed anything .  So what you are telling me is, my actually ohm count is only half of what I thought it was when this is done.  Thank for the clarifation.