What is the Gear Ratio on Rokutan "Shorty" Chassis?

[Maletrain]

I am looking at tiny motors to make a mine locomotive in N scale using the Rokutan Z scale "Shorty" motorized chassis.  I am thinking about replacing the 6 mm coreless motor with a similar motor with a planetary gear head to slow it down.  What I am trying to determine is what ratio planetary gear I want.  The info I don't have is the ratio of motor RPMs to wheel RPMs for the "Shorty" drive train as it comes from the factory.  Has anybody counted teeth on one of those?

[peteski]

I don't have the info you are asking for, but I suspect that using the gearbox with the numerically lowest available gear ratio (like 4:1, which is probably the lowest you can find) will give you more than adequate speed reduction.

[Rivet Miscounter]

Don't know the answer, but this video might help. 

 

Also this thread has some good info: https://www.therailwire.net/forum/index.php?topic=44612.0 .

There seems to be a good amount of info in Google...the answer is probabably there somewhere.  Make sure to search for "Rokuhan", not R-o-k-u-T-a-n.

[Chris333]

I'm Guessing around 20-25:1.

Where you getting gearheads?

[Maletrain]

Ok, that video really helped.  I could count 12 teeth on the worm gear in the video, and I pulled an axle off the chassis and counted 8 teeth on the axle gear (I think - hard to see clearly).

So the answer to my question about gear ratio is 12:1 x 8:12 = 8:1 from the motor to the wheels.  But, while you helpful folks were posting responses, I tried to measure the speed with 2 AA batteries (3.2 volts) and got ~3.25"/second.  The wheels measure 0.15" diameter, so that means that the motor was only doing about 3300 rpm (if I didn't screw-up my math).  I tried with 3 AAA cells and it was more than twice as fast - not measurable on my small piece of track.

I am going to take this to my club where I can measure speed on a loop with a stopwatch and voltage on the track with a meter and try to get a speed table.  I'll post here what I get for a speed table.

My next question is what voltage should be my max to ensure decent motor life.  The eBay listings for motors similar to the ones I am considering have test rpms at voltages up to 4.2 volts, but the ones I am considering have test results at only 3 volts - and those results make the motors look like they run at about 30,000 rpms at only 3 volts.  I am wondering if the load on the Rokutan has that much effect, compared to a planetary gear, or if I am looking at very different motors.  They all look the same, canned 6 mm outer diameter.

[Chris333]

Damn I was being generous guessing 20:1.   12:1 yikes!

[Chris333]

@randgust did a Nn3 Climax using this chassis and gearhead.

[Chris333]

I *think* the truck gears are just transferring power and not reducing anything.

[Maletrain]

Chris, there are lots of 6mm motors with planetary gear heads in 1, 2, 3 and 4 stages on eBay.  For instance: https://www.ebay.com/itm/364586546614 has options for all 4, with some specs.  But, there are a lot that are cheaper.

[Chris333]

They look like the old Gizmozone motors. That one would give a 61:1 total gear ratio.

[randgust]

No, that's the Solarbotics motor/gearhead that's 25:1.   That's a hybrid drive using the Kato universal, driveshaft and worm, to the Rokuhan trucks.   And THEN it goes into the worm, so top speed on my Climax A is maybe 30mph with that gearhead screaming.

This is the standard gearhead motor I put in all my Climax A custom builds, not just the Nn3 ones.  And in that video, that's WIDE OPEN.

https://www.solarbotics.com/product/gm15a

Yes, it's 3V, I just drop a 100-ohm resistor in there in series, have yet to burn one out.  They are a little noisy with those gears.

I did Gizmozones 5.14:1 for years but now they are discontinued, you could put those on the Kato 11-105 12V motors.

Now, out of the box, those Rokuhan SA's are virtually uncontrollable, worm right into the axle.   The only thing that I've found that can tame them is the Blue Snail Z throttle that runs on a 9V battery.   I love those throttles.   I can get absolute creep out of my Climax A's with that.   But stock?  I can't imagine a worse drive for a mine locomotive.   And with a gearhead, you don't have a stable shaft, you're kind of stuck with a universal to driveshaft to worm.   I'm just telling you the Kato worm works with the Rokuhan spur gear, and it took me MONTHS to develop a frame to make that relationship work reliably.

[Maletrain]

Randgust, what gears and worm are you suggesting I use?  Do you have URLs for the parts?

[randgust]

Maletrain, see your PM