1/72 Type VII Motors Help

[jure george]

Hello

Can someone please tell me what type of motors to use for my 1/72 Type VII Submarine in my own WTC? I have heard of the older motor/gear combos from airplanes BUT they are VERY Hard to find now. I would think direct drive brushed motors would by my choice BUT I don`t know what to use or where to find them.

Any help would be appreciated.

P.S. Before I forget, same motor help needed for my 1/144 Kilo as well.

Thanks for your help.

George

[raalst]

Re: 1/72 Type VII Motors Help

for the Kilo any small motor will do (provided the prop is not very oversized)
I have had very good results running with motors from car door locks
(powered by 6 cells, i.e. a nominal 7.2 volts).
I use them in the water (i.e. outside the WTC), only protected by a puff of WD40.
they last well over a year that way.

If you want to go even simpler, consider disassembling an old normal size servo
loose the gears and presto, forward/backward controlled small motor.
keep the electronics dry, of course, or encase them in e.g. silicone.

[Guest]

Re: 1/72 Type VII Motors Help

A little ambiguous to say that any small motor will do the job, as they come in so many different winds from mild to wild.

Instead it's much better to think about what diameter and pitch of prop you wish to run and go from there.

In the case of a scale sub, the style (e.g. blade area and shape) and diameter of prop tends to be dictated to us by the original 1:1 prototype, and if we wish to remain faithful to the prototype, then realistically the only thing we can adjust to suit our requirements is the angle of attack of the blades of the prop to influence pitch.

Generally the optimum range is between .8-1.5 times the diameter, with 1-1.25 being about optimum.

If we know the pitch of our prop, we can quite accurately calculate the speed our boat will make at a certain RPM. We also need to bear in mind that electric motors work at best efficiency when loaded at about 75% of their unloaded RPM, so we should ensure our motors do not operate at below 75% to get best value. If we go above that figure, then the motor is getting an easy life, but that is preferable to it being bogged down, where much of the energy is transferred into producing heat.

So how do we know what motor to select? Well the way I go about it is to consider the speed I wish the boat to travel at, then I calculate the pitch of the prop if it isn't already published, then work out how many RPM that prop needs to get the required speed. I then see what motors are available to me that can give me that RPM plus 25%. If running direct drive the diameter of the motor should be within 3/4 the prop diameter or greater a rough guide but effective. Very often it's not possible to get a motor at sufficiently low RPM, therefore you need to think about some form of reduction (gears, pulley etc.).

All this will get you very close to the magic number, but there is still a fudge factor, as hull shapes, propeller efficiency etc. all influence the final performance, but it's so much better than guess work.

[giovanni]

Re: 1/72 Type VII Motors Help

Andy,
You have a very good knowledge of motor/prop combinations.
This must come from many years of experimentation.
What subs are in your fleet?

[Guest]

Re: 1/72 Type VII Motors Help

I have documented some of my projects on here and in the SCR, both verbally and through pictures. I wish I could say the same for you, despite the impressive range of boats listed in your signature.

Perhaps before throwing stones, it may be an idea to step outside of the greenhouse.

[jure george]

Re: 1/72 Type VII Motors Help

Hello To All Memebers

I posted this simple question with the hopes of learning what motors would be recommended to be used in my 1/72 Type VII. I did not intend on any other actions to be displayed. Please everyone stay focused on my simple question.

If someone here has successfully built a r.c Static diving Revell 1/72 Type VII, could you please tell me what motors you used and where you got them from? The same question applies for my Trumpeter 1/144 Kilo.

Again Thank you ALL for your replies Especially Mr. Subculture, I REALLY ENJOYED your posted End Cap/O Ring Making Video VERY Educational.

George

[bob_eissler]

Re: 1/72 Type VII Motors Help

Hi,

If you look at a subdriver sold for that sub you can see that 2 280 size motors work. The diameter of your WTC is a limiting factor. The Gatos seem to have 380 size motors if you have room. The kilo is very small in comparison. A look at frontal areas and similar lengths of subs will get you in the ball park.

[Guest]

Re: 1/72 Type VII Motors Help

280 size motors will most definitely do the job, but they do come in some hot winds. You don't want anything exceeding about 10000RPM unloaded, else you'll turn the Type VII into a speedboat when on the surface. In fairness I'd say a shaft speed of possibly half that will be adequate, but it does depend on the pitch of the props you are using.

In fact a couple of 180 motors would be quite sufficient, if you were to cut the revs a bit by employing some form of reduction e.g. gears pulleys etc. about 2 or 3:1

[redboat219]

Re: 1/72 Type VII Motors Help

How these 130 motors?

http://www.pololu.com/catalog/product/1117

[Guest]

Re: 1/72 Type VII Motors Help

Bit small. 180 is better.