Rokuhan Z Shorty For N Scale

[Mark W]

Last year Rokuhan released a new power chassis for Z Scale called the "Shorty". 
http://www.rokuhan.com/english/products/shorty-series/

Z Shorty package

https://i.imgur.com/u2mqBtf.jpg

The guys over on another Z scale forum have done some pretty sweet stuff with this chassis already.  Surprisingly, I don't recall seeing any discussion on the Shorty here on TRW.  Especially after the TP56/70 projects, I'd have thought to see someone do something with the Shorty by now.  The only thing I can think is that since it's a Z scale product, N Scalers are just overlooking its potential, or simply dont know about it yet.  So I thought it would be useful to share how to very easily convert the Rokuhan Z Shorty to run on N Scale track by stealing parts from the Kato N Scale Power Chassis.

Out of the package, here's a quick comparison of the Z Shorty with Kato's N Power Chassis.

https://i.imgur.com/o3FHGPr.jpg


https://i.imgur.com/ihLe3k3.jpg


https://i.imgur.com/T66ocRU.jpg
 

Disassembling the Z Shorty is very easy. 

The top literally pop's off. 

https://i.imgur.com/tDCiSY9.jpg

The normal truck is un-screwed.  To remove the geared truck, remove the metal pin/gear shaft.  The motor just lifts out.

https://i.imgur.com/kvlUTNC.jpg

For converting this to run on N Scale track, this is were we got real lucky! 

I originally thought I'd turn down the axle on two FVM wheelsets (center picture), but that's when I found the old Kato Chassis in my parts bin.  Turns out the Kato wheels are an exact match to fit the Z Shorty geared axle sleeves!  In fact, the gear mesh on the Z Shorty even matches that on the Kato axle gear, however you can see on the right side, the Kato gear tooth is much more narrow.  It would work, but I'd stay with the original Z Shorty gear for piece of mind. 

https://i.imgur.com/4v7gF8v.jpg


Once properly gauged, next up is power pickup.

https://i.imgur.com/u5G3kCe.jpg

I cut the top tab off (may be optional), flattened the whole thing, drilled out the axle cups and drilled a new hole to clear the top gear shaft.  Be sure to isolate the gear shaft from one (or both) sides of the contacts.

https://i.imgur.com/Ani3O6b.jpg

And at this point we have a Z Shorty that can run on N Scale track!  Note: there is a MTL coupler spring between each wheel and the pickup to ensure there's good contact between the wheel and pickups 100% of the time.

https://i.imgur.com/zP3Eb7r.jpg


Ok, my part is done.  Now go out there, grab yourself a Z Shorty or two (or three, they're cheap!), and come share your awesome critter kitbashes and scratch builds! 

[up1950s]

Chris and Randy will probably come up with something like a self propelled Burro crane . How about a realistic looking mouse ? Thanks for the heads up and toot .

[randgust]

Wow, thank you.

two questions:

1)  Wheel diameter in N inches?  at the face?
2)  Truck wheelbase in inches - center to center?

Sorry to disappoint you but the burro crane is old news: 

/>
Yikes, 10 years ago...!

But I'm always looking for that elusive 48" wheelbase powered truck.

[Chris333]

Chris is out in his garage 

[Cajonpassfan]

Sweet.
So two questions please:
How does it run?
What is the axle spacing in N scale? (Truck spacing and wheelbase)
Thanks.
Otto K.

[Mark W]

Wow, thank you.

two questions:

1)  Wheel diameter in N inches?  at the face?
2)  Truck wheelbase in inches - center to center?

But I'm always looking for that elusive 48" wheelbase powered truck.

Sweet.
So two questions please:
How does it run?
What is the axle spacing in N scale? (Truck spacing and wheelbase)
Thanks.
Otto K.

Ah, should have included these in my original post. 

The truck is 60 scale inches axle to axle.

Wheel diameter is 24.5 near the flange, 24.35 at the face.

Bolster to bolster is about 105 scale inches.


I say the running quality is excellent!  Of course with these pager motors, throttle is very sensitive, but you could get a good 5smph creep. I haven't seen anyone do so yet, but I bet using the Gizmoszone 1:5.14 gear motor would really bring it to a crawl, though you may need to extend the wheelbase some for that motor.

On the other Z forum, someone designed new chassis and SW1200 shell to be printed in brass.  Here's a video one guy shared showing of the smooth running and amazing pulling ability! 

/>

[up1950s]

Wow, thank you.

two questions:

1)  Wheel diameter in N inches?  at the face?
2)  Truck wheelbase in inches - center to center?

Sorry to disappoint you but the burro crane is old news: 

/>
Yikes, 10 years ago...!

But I'm always looking for that elusive 48" wheelbase powered truck.

Damn quiet too .

[Cajonpassfan]

Thanks for the dimensions Mark, appreciated.
Being no Max, I was thinking a powered tender for this 0-6-0, pic below. The tank body is exactly 20' long...
Still, it doesn't look like this is the answer, it would need to run like a switcher, slow and steady.
Otto K,

[randgust]

The Kato 'critter' has a 5'6" wheelbase and what I've measured to be a 27" wheel, that's my story and I'm sticking to it.  So this is 5' and 24".   Hmmmm.
What I really like about what you did is the ability to make inside pickups on that.   That's freakin' genius.  THAT will get adopted.

10 years ago the only 'video' I could shoot was off my Canon zoom camera - NO SOUND!

But it actually does OK.  I did a full build thread on it but the photos were on a different ISP server.
http://www.trainboard.com/highball/index.php?threads/powered-burro-crane-project.37746/
  It's one of those tiny Japanese four-wheel trucks with one-axle drive, and a very ground-out Railway Express Miniatures cast pewter metal body.  The flatcar is permanently attached with Kato caboose trucks and an extended frame for 8x8 electrical pickup, so it's quite reliable.  It's the smallest running 'thing' I've ever done in N, smaller than the 25-tonner.  Other than the fact it can't pull much more than itself, it runs great.

[Mark W]

What I really like about what you did is the ability to make inside pickups on that.   That's freakin' genius.  THAT will get adopted.

I didn't mention, there is a MTL coupler spring between each wheel and the pickup.  Ensures there's good contact between the wheel and pickups 100% of the time. 

[peteski]

I didn't mention, there is a MTL coupler spring between each wheel and the pickup.  Ensures there's good contact between the wheel and pickups 100% of the time.

Mark,
That is an important construction detail. It would make sense if you added this  info to your initial post. That way someone reading the thread for the first time will have complete info in there, rather than maybe finding it 10 posts down. Especially as the thread grows, the info in your additional post will be buried in the middle of the thread.

[mmagliaro]

I didn't mention, there is a MTL coupler spring between each wheel and the pickup.  Ensures there's good contact between the wheel and pickups 100% of the time.

Aha!
I was wondering how the pickups were really going to work without riding on the axle points.  The spring is a good idea.

[randgust]

Not only that, but many end-axle pickup trucks rely on those for bearings with no retention design of the axles against the gears if they are removed.  The Kato critter truck is like that, and if you try to modify it to not be end-axle bearing you have to also have to make a new precision inside sideframe out of brass to hold the axles.  Gert (Waldbahner) did it for his Westside Heisler, one of those things most mortals can't do.    Showing that using the axle cups inside on the Z trucks to fit N got an audible 'wow'.  Last time I had to make that kind of a member salute was when it was proven that you could fit 27" critter wheels into a Kato 11-103 chassis and junk the original 42" wheels, which was the breakthrough on my trackmobile project.  And way back when, when Ron demonstrated you could make a 44-tonner design fit the critter.

If you look at most of the inside-axle bearing critter designs out there from Tomytec and others, they all depend on the contact ears pushing down on a brass plate to the axle insides, and none of them work as well as an end axle pickup does.   The coupler spring thing is significant in solving that problem and I can hardly wait to try it.

[peteski]

If you look at most of the inside-axle bearing critter designs out there from Tomytec and others, they all depend on the contact ears pushing down on a brass plate to the axle insides, and none of them work as well as an end axle pickup does.   The coupler spring thing is significant in solving that problem and I can hardly wait to try it.

There are couple of things about using that spring that to me might raise flag:

1. How quickly will the fine-wire Phosphor-Bronze spring will last before it wears out at the contact area?
2. Will the very fine spring be damaged (melted) by a heavy current of a short if it happens to be the sole path of the current (if the axle is not in good contact with the bearing plate)?

But that is just me trying to theoretically consider the worse case scenarios. I think that in actual use there is nothing to worry about.

[mmagliaro]

I did kind of worry about the short/melt problem.   MT phosphor brone springs are made from .006" wire, I believe.
The AWG charts say that can carry 330 mA (for "chassis wiring" which is the higher rating, as opposed to "transmission", which we don't care about).
That ain't much if a short occurs.  But you'd have to be unlucky enough for the short to happen to complete its path through one of those springs.   I'm having a hard time envisioning how that would happen.

As for the springs wearing out, I suppose they could.  But phosphor bronze wire is more durable than carbon brush material, I would think.  And the rotational speed of the wheels is much less than a motor armature.  So I would expect the springs to far outlive the motor, and probably outlive the owner of the model.