If the gear motor is rated to no-load speed 5rpm, fitted to HL stock ratio gb, what's that going to be like? If that too slow, what would be the minimum rpm it should be?

That will be extremely slow. We are talking slower then snail pace.

If you have a smartphone, there is a good app called "RPM Visualizer" that you can download. I've found it to be very useful.

@Dan, how about 200 RPM ones?

@Captain Nemo12, thanks, I checked out the software & it's very useful. I'm now trying other apps too.








EDIT: I checked 200 to 250 RPM with the app, it still too slow I think. Maybe need at least 300 RPM.

If we are talking about so called "3:1" HL gearboxes It should be about 15000-17000 rpm at 7,2V

Kizwan - see these two posts...they have gear ratio/tank speed info to answer your question.

http://www.rcuniverse.com/forum/rc-t...l#post10509044

http://www.rcuniverse.com/forum/rc-t...l#post10509277