Best Of The TP56/TP70 Kitbash thread N scale

[Chris333]

You can just make the adapter with brass tube. Or buy them here:
http://www.nigellawton009.com/PayPalMotors.html#Pulleys

[u18b]

Wow.  You guys are certainly resourceful.   It's what I like about hanging out here.  I learn a lot.

So, yes..... I had thought that if the worm was bored to 1.5 mm then that would give more options for motors.
It might NOT- since space is tight.    But, yes I did think that.   But, there is also a bearing disc that is on either side of the worm in there.   That's what the plastic housing holds.  So those would have to be changed out/re bored also.   That would all get too complicated.

The goal we were shooting for is something that is reproduce-able.  If we get too complicated, then the desired end is missed.

Of course, the limited availability of the Kato truck is a problem too.

[u18b]

Maybe a couple of these photos will help.

This is the stock Kato mid truck with the worm retainer/cover off.
shaft 1mm diameter.
Notice that the retainer holds the round bushing discs on the ends.
So if you do something to the cover (like cut portions away to get the motor closer) then if it will no longer latch properly, the usefulness of the cover to hold everything together is gone.




Here you can see how short the stock Kato 11-105 motor is.   The replacement motors I have coming next month have shafts that are about 10 and 12 mm long.



And here is the helicopter motor I was talking about.  This tiny thing mounts in the tail.
It has a shaft that is .78 - .79 mm.   So a sleeve that goes from .8 to 1.0 mm might work.
But even then, I'm not certain the shaft is long enough.



And these are the motors that I ordered from Asia.
Pics are taken from the ebay listing.
They both have 1mm shafts.

And they are both stupid cheap.   Like one buck each.

This one has a 10 mm shaft length.



And this one has a 12 mm shaft length.

[peteski]

Ah, so both the worm and motor shafts are 1mm.  So you could partially push the worm shaft out and insert the critter motor shaft in the hole in the worm. Then Beardenize the assembly (only keep the outside bearing on the worm shaft). 

As far as the worm bearing retainer, you should be able to find a way to fasten a trimmed one to the gear case. Maybe drill a hole clear through the worm bearing retainer and the gear case (before trimming it) then pin it after trimming. That way it will be correctly aligned.

Or like I mentioned, use a short rubber-tube coupling between the Kato motor and the worm.

That truck is very low-friction but I think that you'll be better off using a conventional motor (not the small coreless motor). I think those small coreless motors don't have much torque at low rpms.

[Chris333]

Again I don't even know if you need to move the motor in, but it can be done.

In this photo:
https://goo.gl/photos/4VxPtrxLSVFpfBog9
The very short motor shaft is inserted into the worm. Then I took more 1.5mm shafting and glued it into the other end. This sticks out and is supported in the bushing.

[mmagliaro]

There's something fishy about that Mitsumi motor.  The M20 does not correspond to that size or those characteristics.

You can look it up on Mitsumi's website here:
http://www.mitsumi.co.jp/latest/Catalog/pdf/motorav_m20n_8_e.pdf
The case isn't even the same as the one in your photo.

I think those are "artistically rebranded" motors that are not actually Mitsumi.

However, Mabuchi makes an "FF-N20" series, and I think there's a good chance that's what you are really getting. 

Here's the Mabuchi.  The RPMs are higher than 4000, more like 12000, but otherwise, this looks close.
https://product.mabuchi-motor.com/detail.html?id=16

[mmagliaro]

Again I don't even know if you need to move the motor in, but it can be done.

In this photo:
https://goo.gl/photos/4VxPtrxLSVFpfBog9
The very short motor shaft is inserted into the worm. Then I took more 1.5mm shafting and glued it into the other end. This sticks out and is supported in the bushing.

Chris, did you build the brass loco in that photo ???

[randgust]

This was my experiment that failed.   Well, it worked, well enough on the workbench, to make my 25-tonner work better.  This is a Tomytec power truck, end axles, and the way I made it, equalized.   Drilled out the worm to press-fit a .7mm shaft on the Motorola 9V pager motor.   

But this is also where I learned, the hard way, that tiny pager motors have no torque to speak of.  You could stall it out with 3 cars, it couldn't move.   If you gave it a nudge, it could start, and then accelerate to warp speed.   Could run on its own though, and on a test track.   

Filed under 'seemed like it would work'....

[Chris333]

Chris, did you build the brass loco in that photo ???

It is a Sango brass kit. If I had made the frame perhaps I would have finished it...

[narrowminded]

There are some very basic principles, undeniable facts, at play here that you shouldn't lose sight of.  If you don't have the leverage (above 75:1,preferably over 100:1) then you need brute force (torque, bigger motor).  And If you want good scale speed you need either a slow motor with a lot of torque or a very high gear.  And If you have a very high gear you don't need much torque.  You accomplish the work with leverage.   There's nothing magical here, just those simple facts going round and round.   The other thing is weight for power pickup and traction.  Randy has the leverage with his planetary gear and if there's enough room you can add the weight.  When you have those bases covered it will work well.  If not...

[coosvalley]

As a casual observer...I think the best course of action here is to combine a gearhead into U18bs design, and to me it looks like it would fit.....Find a way to connect everything as close as possible, and you're good to go.....Am I missing something?..

[randgust]

Got the frame finished by doubling up the brass sheet - nice and heavy, and got the end sills/steps on by epoxying them to soldered-on brackets on the frame.  Put couplers on it and did some road testing and switching.

Observations:  It's bigger than most; I scaled the frame out to 31' using that side photo (one with the fuel tanks) based on the known wheelbase of the truck.  For a critter, it's actually a pretty big one.   It runs over an Atlas C80 #6 crossover with long insulated frogs flawlessly.   With the cab weight on, the tractive effort is really good, pulled around a respectable train.   Slow speed is excellent, pickup good - only gets a little odd at extreme slow speed where it will unexpectedly stall.  I suspect there's more room in this thing than I thought for weight.  Definitely sold on the 5.14:1 gearhead, it lugs nice at slow speed and the motor RPM's done don't change even at full slip.

I wish this thing was more repeatable.  Given what I'm seeing about the actual hood length, with a little luck you can still get room in there with the Kato truck for a motor, trick will be for a gearhead.   I'll openly wonder if one of the smaller, yet powerful, Gizmoszone gearheads with the smaller pager motor is the way to go with DCC limiting the motor voltage.   My experience with the tiny planetary gearheads is very good, but they do sound like there is a bee trapped in the shell when they are really cranked up.  You'd still have to splice the worm shaft for most of them that I've used, but they have alternatives.    I've used the tiniest motors/gearheads in the Climax and they have plenty of torque, just really slow.

Gizmoszone does have 'long shaft' 1.5mm drives, but the gear reductions are pretty darn high.   I'll guess, but don't know, that the 8x10mm 3v motors are swappable with the Kato 12V motor like the other one I use.

http://www.gizmoszone.com/shopping/agora.cgi?product=Gearmotor&user6=longshaft;ppinc=1g

My approach to most of these critter mechanisms has been pretty much like watching the coyote design roadrunner traps.

[Philip H]

@randgust - neat little 25 tonner.  Given that we have 3 axles in play here, I'm wondering if the design approach would better match a 50 tonner . . . of course i"m several dozen projects away from even attempting this one . . . .

[narrowminded]

... Slow speed is excellent, pickup good - only gets a little odd at extreme slow speed where it will unexpectedly stall.  I suspect there's more room in this thing than I thought for weight.  Definitely sold on the 5.14:1 gearhead, it lugs nice at slow speed and the motor RPM's done don't change even at full slip.

My approach to most of these critter mechanisms has been pretty much like watching the coyote design roadrunner traps.

And there are those basics, covered.  5.14:1 then 20:1 or if a compound reduction truck, maybe 30 something :1, and there you have the 100 to 150 or so :1 ratio.  And it works.  Randy, it's that ratio that was missing in your 25 tonner and explains all of its faults including the stall then runaway speed problem.  Even if you got there by guess, you still got there.  In the future there will be no need to guess.  You've got the proven data.

[narrowminded]

Several years ago I got a batch of Motorola pager motors off of Ebay - with the vibrating metal cam still on them - that were rated as 9v. Dirt cheap and super tiny.  That's what I tried to use on the 25-tonner truck, direct DC.   .7mm shaft, sleeved it up, mounted a worm on it that was about as big around as the motor.   Didn't matter, still didn't have any torque.

After that I kinda gave up on them, but if somebody else wants to take a shot using one, hey, PM me.

Do you have the body diameter and length of those motors?   I might be able to use them although I suspect they'll be too big if 9 volt.