Removing Trucks From Trix H12-44

[peteski]

Minitrix motors have 1.2mm diameter shafts. Not sure why they went with 1.2mm. Most other motors use 1.5mm shafts.

I would say that reducing the 1.5mm motor shaft down to 1.2mm would be much more difficult that reaming the 1.2mm worm to 1.5mm.  Motor shaft is made from hard steel and at the length and diameter it is would be quite difficult to turn down on a lathe (especially since it is an integral part of the motor.  Even if you took the motor apart, the armature is still quite bulky and it is permanently attached to the shaft.

But reaming the hole in a brass worm could be easily accomplished even by hand (using reamers).

[nstars]

Marc:  If all you want to change is the truck gear ratio, you're right.  But if you want to change the total gear ratio, between the motor and the wheels, a gearbox at the motor would do the same thing.  Either way will change the ratio between motor and wheel RPMs. 

In the Minitrix model, simply installing a modern motor would make a difference.  The models run nicely, but tend to start abruptly, due to the primitive 3-pole motors. 

FYI Hans has made a replacement kit for an H12-44 for John and although the results were not bad, it was not as good as for instance replacing the motor in an Arnold S2. Main reason was the low gear ratio between motor and truck. Adding a gearbox to the motor won't be a good solution as it won't work with 2 trucks powered. It would require gearboxes on 2 sides, which as far as I know is not possible. You will also fight for room, both length and width as the available space is tight. Perhaps John can post his pictures of the conversion.

Changing the gear ratio would require changing the module size of the gears and the worm. As I mentioned, we haven't done it yet. Perhaps a better idea would be to use a VO 1000 chassis from Atlas. This is also the method used for the H12-44 available on Shapeways.

Marc


Marc

[nkalanaga]

No, putting a gearbox on both sides wouldn't be practical, in such a small loco, but it's probably the only way to change the gear ratio without totally rebuilding the drive.  You're probably right that repowering it would be the easiest option.  And, if it matters, one could get DCC at the same time, which wouldn't be easy to put into the original, due to space constraints.

Peteski:  You've had a lot more experience with that than I have.  My thought was to chuck one end of the shaft, armature and all, into the lathe/whatever and turn the other end, then reverse it to do the second end, without taking the armature off.  It should be balanced, so would spin smoothly, and wouldn't be turning any faster than in the motor, so centrifugal force wouldn't be a problem.  But, then, I'm not a machinist, and have never used a lathe or similar device.

Is the problem that the shaft would be too hard, and require too much force on the tool or file, risking bending the shaft?

[peteski]

No, putting a gearbox on both sides wouldn't be practical, in such a small loco, but it's probably the only way to change the gear ratio without totally rebuilding the drive.  You're probably right that repowering it would be the easiest option.  And, if it matters, one could get DCC at the same time, which wouldn't be easy to put into the original, due to space constraints.

Peteski:  You've had a lot more experience with that than I have.  My thought was to chuck one end of the shaft, armature and all, into the lathe/whatever and turn the other end, then reverse it to do the second end, without taking the armature off.  It should be balanced, so would spin smoothly, and wouldn't be turning any faster than in the motor, so centrifugal force wouldn't be a problem.  But, then, I'm not a machinist, and have never used a lathe or similar device.

Is the problem that the shaft would be too hard, and require too much force on the tool or file, risking bending the shaft?

Actually DCC decoder would provide pulsed voltage to the original motor so it should be able to run it at very low speeds.

Yes a motor shaft is way too long for its diameter and the metal is too hard for a cutting tool to bite into it without deflecting it. There are ways to stabilize long pieces while being machined, but that is not something that a hobby machinist would have handy. Actually grinding down the shaft would probably be easier to accomplish, but again, that is not something an average hobbyist is equipped to do accurately.

Reaming out the hole in the worm seems like a much easier task.

[nkalanaga]

Peteski:  Thank you.  That makes sense.  If the Fm is like the Fs, and I'm NOT taking mine apart to look, there was a connector between the motor shaft and the worm shaft, sort of a makeshift U-joint.  If that's the case, changing the motor would be very simple, once a new one is found.  Shorten the motor shafts as needed, ream out the connector, and you're ready to go, no need to disturb the worm at all.  I've removed the motor on the F units without taking the worms out, although it might be easier to take it all apart.

[Altoona]

"Changing the gear ratio would require changing the module size of the gears and the worm. As I mentioned, we haven't done it yet. Perhaps a better idea would be to use a VO 1000 chassis from Atlas. This is also the method used for the H12-44 available on Shapeways."

One problem with this . Shapeways 12-44 is good for phase I and II, which have long frames. Phase III 12-44 (Minitrix) had a shorter for due to rearrangement of it inners.


Judd Barton

[nstars]

One problem with this . Shapeways 12-44 is good for phase I and II, which have long frames. Phase III 12-44 (Minitrix) had a shorter for due to rearrangement of it inners.

Oops, good point, complete forgotten. I guess it's the holiday season, I also forgot another H12-44 Hans did modify. He replaced the trucks with LL SW9 trucks. He also used a new motor with added idler gears between the worm and the truck (see pictures below). Not an easy conversion, but the results are good.

Marc

[tehachapifan]

Wow! Talk about a major (and extremely well done) rebuild!

[sp org div]

Some precision work on the drive-train that looks pretty awesome... but dont the trucks need to pivot by use of a worm / idler combination, or is there some other magic down below that we dont see in that pic?

Jeff

[peteski]

I was also wondering about that.  The way I imagine it is the worm engages the small worm gear which then engages what used to be the worm gear on the truck. Except instead of meshing on top of the trucks ex-worm gear, it meshes with it on the side.  But the new worm gear must be wide enough so it meshes with the trucks ex-worm gear while the truck pivots to the sides.  Too bad we don't have more photos of that part of the mechanism.

Old East German Piko N scale locos used a wide gear to couple with a pivoting truck.

[nstars]

There is a picture with more detail and from this picture you can see that the pivot point of the truck is right in the middle of the truck, only a little bit lower than the original H12-44 truck. It is difficult to see, but you can also see that the new worm gear is indeed relatively wide.



Marc

[peteski]

Thanks Marc.
So this setup is only to relocate the worms and to use low-friction trucks - there is no additional gear reduction added.

The motor looks quite odd - very small armature and very small magnets.  That armature looks similar to the 5-pole replacement armature for old Rivarossi can motors.  Does the motor have enough torque at low speeds for smooth operation?

Looking at that setup, there seems to be plenty of room for a much beefier motor (or to add some weight.

[nstars]

Thanks Marc.
So this setup is only to relocate the worms and to use low-friction trucks - there is no additional gear reduction added.

The motor looks quite odd - very small armature and very small magnets.  That armature looks similar to the 5-pole replacement armature for old Rivarossi can motors.  Does the motor have enough torque at low speeds for smooth operation?

Looking at that setup, there seems to be plenty of room for a much beefier motor (or to add some weight.

Peteski,

Compared to the original setup the gear ratio has improved considerable. Don't forget that these are not the original Minitrix trucks. The trick is the gear setup within the Life Like trucks with different module size for the gears. In fact the whole gear train from worm to wheels has been changed, which in the end has resulted in the much needed improvement in gear reduction. The consequence is that this small motor has a much easier job than the motor in the original configuration.

Marc

[peteski]

Don't get me wrong Marc, I do realize that the modified mechanism is a great improvement over the original setup (especially with the low-friction trucks). That is a very advanced conversion. I guess I was just wondering why wasn't a larger motor installed?  But maybe it is just not needed for such a small locomotive.

Do you know where that motor came from?  I'm really curious as I never seen anything quite like that.  Especially with such small flat magnets and a large air-gap between the magnets and the armature.

[nstars]

I checked it and it's a Mashima 9x16 motor.

Marc