Key Imports PRR I-1

[mike_lawyer]

I was able to pick up a Key Imports PRR I1 2-10-0 for a good price.  It was basically brand new in its original package.

Out of the box, I was surprised how well it ran with the minimalistic drawbar electrical pickup.  Top speed is much too high, but pulling power is off the charts.  I was able to pull 40+ cars with ease.

I plan on inserting Kato Mikado tender trucks for all-wheel pickup, and also remotoring with a coreless motor for better low-speed control.  One issue that I have is that on one corner of my layout, I have 16 inch radius curves.  The locomotive slows down around that curve.  It looks to me that there is very little lateral play with the drivers such that there is tightness when tracking around curves.  Has anyone worked on one of these locos to improve tracking around curves?  I imagine there must be some way to improve that on the locomotive.  Any assistance would be appreciated.  Thanks!

Mike

[mmagliaro]

The pulling power on these is good on a flat.  I believe it can pull 40.  I did repair work on one of them and it could easily pull 20 without a struggle.  But up a grade is another story.  Twenty 40' cars was about it on 1.7% curved grade.

I only ever ran it on 18" or broader, so I didn't see the curve problem you mention.  But it doesn't surprise me.  Even though it has a blind middle driver, if drivers 1 and 5 don't have much lateral play, it's going to be a challenge on 16" radius.   If only you could get the axles out of the bearings, you could sand the bearings outer faces a little bit and that would get you some more lateral play quite easily.  But the two drivers, bearings, and axle do not come apart.  You can't press drivers off on these brass models very easily and getting them back on can be even harder, so I wouldn't try it.

Have you checked to see if it is the rods themselves that are restricting the lateral play of the outer drivers?
It could be that 1 and 5 drivers would move outward a little more freely, but are being held in by the rods being pinned to
2 and 4.  This model is geared to the center driver, and all the rest of the drivers run on the rods.  Perhaps you could loosen
the crank pins (or screws, or whatever they used, I don't remember) on #2 and #4, so the rods can flop outward a little more,
allowing the outermost drivers 1 and 5 a bit more lateral motion. If that works, then you just need to find slightly longer
pins or screws that will tighten up while still leaving a bit of gap between the rod and the head of the crankpin on #2 and #4.

If that doesn't yield any fruit...
One trick I used on another brass model to give it more lateral play (and was essentially in the same boat - can't take the axles apart) was to run it in a cradle on its back, and painstakingly ride the blade of an Xacto knife square against the inside faces of the drivers, essentially machining off some of the metal. It took quite a while to take about .005" off each one.  If I were doing that today, I'd put the driver in a lathe and do the same thing, just much more easily!  Just try to get .005" off.  That would get you .010" more total play, which is a good amount when you consider how thin the rail itself is.

That did work on my other engine (it was a Hallmark 2-10-2, I think).  But be aware you are running some risks.  If you let the drivers slide back and forth more, there may be more things they can touch and short out on.  They can also start introducing rod jams you didn't have before because the more the drivers can slide out, the more they alter rod hole distances.

[peteski]

Unlike plastic models which are designed from the start to traverse unrealistically sharp curves, brass long rigid wheelbase locos are not designed for that, so like Max mentioned, it would be very difficult (or almost impossible) to get them over relatively tight N scale curves.  As I see it, most brass models are designed for realistic appearance more so than for running.

[mike_lawyer]

Max and Pete -

Thanks for the responses, I really appreciate it.  I only notice the slowdown on the one curve at lower speeds.  It could be that the stock motor simply doesn't have enough "girth" at lower setting to overcome any slight "tightness" when going around that curve.

My first steps are going to be to install all-wheel tender pickup, then install a Faulhaber 1016 with a 4:1 gearhead.  Hopefully that will supply enough power to smooth out the running on the curve.  I want to try this first before doing any other modifications, as it might work itself out.

[rodsup9000]

  Mike, If you are using Atlas track, did you keep the sliding rail to the outside of the curve. The sliding rail to the outside, widens the gauge a little and with it to the inside, narrows it a slight bit.
Just a thought

[mmagliaro]

If your plan is to put the Faulhaber + 4:1 in it anyway, I agree that is the first thing you should do. It will make so much low-end torque that, as you are hoping, it will probably push right through curves without a hitch.

[mike_lawyer]

OK, need some help on the remotoring.  The stock motor is 23mm long.  Too short and not really enough room for a Failhaber 1016 + 4:1 gearhead.  Here are some pictures:





Two questions:

1.  How do I remove the stock motor?  The motor is held by an L-bracket connected to the main gear that connects to the center driver.  I cannot figure out how to remove that bracket.  I removed the bottom plate, but cannot see any access to that gearbox.

2.  What motor would be recommended that would fit in this 23 mm space?  I want a much lower top speed and better smoothness and torque at lower speeds.  Stock motor has a top speed with this loco on par with a Kato Mikado.

[kiwi_al]

Okay so the motor from a Kato Mikado should fit. I bought a few Kato Mikado clone motors from china but they only have 1 shaft. They also don't have screw holes for mounting but you could drill those. The length is 23.75mm. See attached pictures.

[mike_lawyer]

You are right about the Kato Mikado motor being the right size, but the top speed is way too high.  I am looking for something with much lower top speed and much stronger torque at low speeds.

Maybe just a straight Faulhaber 1016 without a gearhead?  I am also open to flat can motor suggestions.

[kiwi_al]

Would you consider something shorter but with lower RPM?
EDIT: around 21000 rpm or lower like 12000 rpm?

[peteski]

There should be 2 screws on the bottom of the gear case cover  of the driven driver. You might have to remove the bottom frame plate to get full view of the gearcase's bottom.  Once you remove the cover, you should be able to lift the gear case (with the motor) from the top.


Here is a similar disassembled gear case (the bottom cover is not in the photo).  The screws which hold the bottom cover are threaded back into the case, and you can also see where the motor mount would attach.

If yours is different, take some photos of the bottom of the loco.

To  install a longer motor you might try to shorten the worm shaft and make another motor mount.  Or even mount the worm directly on the motor output shaft, but alignment will be tricky. It is easier to retain the flexible coupling.

[mike_lawyer]

Would you consider something shorter but with lower RPM?
EDIT: around 21000 rpm or lower like 12000 rpm?

Something around 12,000 rpm or even lower might work well.  Got anything in mind?

[mike_lawyer]

Thanks Pete, that helps a lot.  There are two screws on the bottom right where the gear is situated, looks like I just have to remove those screws and lift it out.

[peteski]

Thanks Pete, that helps a lot.  There are two screws on the bottom right where the gear is situated, looks like I just have to remove those screws and lift it out.

That should do it. The entire gear case with the motor should just come out from the top. The driver will stay in the frame.  Pretty clever design.

[mmagliaro]

If you want a plain motor, try a Mashima 1224 or 1220 if you can find one on online.  Their top RPM is about 12,000.  Those make a lot more power than a Kato / Atlas motor.  An Atlas "Scale Speed" motor (the gray bodied ones) will have a lower RPM range also.
But before you give up on the Faulhaber + 4:1, look at your photo.  There appears to be a good bit of length behind the
the back of the motor.  When you put the shell back on, check to see if at least some of that empty space back there could
hold more motor and still allow the shell to slip down over it.  The length of a Faulhaber 1016 with a 4:1 gearhead on it is about 26mm.
So you only need 3mm more back there, about 1/8".
As for mounting, what I have done with these L-bracket mounts is make a new L bracket that is made from steel like the original but with the correct dimensions of the two legs of the "L" so that it will come up from the chassis right between the motor and the gearhead.
You make a large hole in it so that you can push the motor nose through it and screw the gearhead on so the bracket is sandwiched between the motor and gearhead.   The bracket will still screw back into the original holes.  It is not easy to get the dimensions of the bracket just right, but it certainly can be done.

Here's a photo in a completely different engine, just to illustrate the idea.



 This motor has a much longer weird gearhead on it, so don't worry about that.  And the L bracket isn't screwed into the gearbox like the I1, but that doesn't matter.  You just need to make an L bracket that gets your motor in the right place to sandwich it between motor and gearhead.  The Faulhaber gearhead mesh can tolerate the gearhead being held away from the motor by the thickness of the bracket.  The bracket needs to be steel.  Brass won't be rigid enough unless you make it unworkably thick (will cause gearhead mount problems.)