Best Of New Brass EP-2 assembly & Mod clinic

[u18b]

OK. now we get more to the fun part.

The drive train.

First let's deal with an important preliminary.
Here is a shot of the mechanism of the new loco as KMT envisioned it.

I know, the worm is too far to the outside-- that's because I didn't want to put it on too tight when I was just going to have to pull it. (so just pretend the worm is directly over the gear.).

Now let's note in that photo that the motor is supported by an L-bracket (on the left side of this photo.).

Here is the bracket in the kit.



And here is a shim that gets it all to the correct height.


But speaking as one who has assembled/disassembled/reassembled EP-2s SCORES of times, that shim is a pain in the pettuties.

One day, sick of lining it up and dealing with it, I thought-- why not solder that sucker to the bracket so I don't have to worry with it any more.

So......

I heat up my soldering iron and remove the stock jumper wire from the bracket.



I then gently file ALL surfaces getting everything to a fresh bright shiny brass.



I then flux the bracket bottom and bottom edges with rosin flux paste  (humor- that tube is about 25 years old.  I bought it my first year of kitbashing).



I then use tweezers to hold the shim to the bottom of the bracket.  Notice that I don't have them quite lined up right yet.


When lined up, I add solder around all sides of the base.  Some of the solder will flow between the pieces.




last step is to clean it all up.


NOW... we are almost ready to explore kitbashing the drive train you saw above.

More next time.
 

[FlyGuyB]

Hey Ron, I can't wait for your other Kumata tutorials. Been following this thread, and makes me want to go out and find an EP-2. Great techniques you're showing us. Outstanding!

[u18b]

Thanks.
I kind of lost some steam on my book.
It is about 70% finished.

Of course this info could be an appendix.

[u18b]

One more important motor preliminary.

It did not take me long fooling with these that I discovered the screw to mount the motor were a bit tight.

I'm not sure why.  It is at least possible that they were tapped for a smaller screw, but KMT did not give me any smaller screws.

So I decided to run a tap through the holes.

Well that was not good.

The motor frame is steel.  With strong magnets.
so when particulate matter comes out of the tapping process, all those little particles stick around and can foul the motor.

So I inserted tissue in the end of the motor.



THEN I  tapped the holes-- obviously not going too deep.



When the tissue is pulled out, the junk comes with it.


I want a completely clean motor-- especially with no obstructions between the motor pole and the magnet wall.

[u18b]

With the preliminaries out of the way,  it is time to talk about some design theory.

Here is the original 1983 KMT chassis design.


Notice the key parts.

1.  L-bracket supporting the motor on the left.
2.  big motor.
3.  Worm in the gearbox but look!  Only the outboard bearing (no inner bearing!).  Hey, they "Beardenized it!" 

Now, when I look at that old NJ chassis, I think.... Dang!  I wish they had not cut the motor shaft on the left side so close.  That would be a great place for a flywheel.

Here is a drawing of the NJ 83 version.



Well, Kumata made some changes to the drive train in this new version.

First, it has a new 5-pole motor that is smaller.



Second, while they include two bearings in the kit, they don't use any bearings at all.  The shaft is too short for an outboard bearing, and they don't use the inner bearing at all.



Here again is a photo of the new chassis with the worm not beaten on all the way.



Now, in theory, no bearing at all should make for reduced friction.  But experience shows that the result is more noise.
I think what happens is that the motor turns the worm-- but the power truck does not want to move.  So the twisting force of the worm builds trying to overcome the friction in the truck.

Well since there is nothing holding the worm shaft, it is natural for it to lift up sightly (as the bracket on the far end allows).
So when it is running, there must be a kind of bouncing that is subtly going on with the motor/worm shaft.

So I think a bearing is needed.  And while I would rather have an outer bearing, I'll have to use the inner bearing.

Now, I don't know what goes through your brain, but when I see the 2003 drawing and chassis photo above, I think--- wow, that's a lot of extra space.  Wouldn't it be great if I could get a flywheel in there?

The simple solution that makes this all possible is to REVERSE the L-bracket that supports the motor.
When that happens, the motor is moved BACK away from the gearbox.  And as long as the worm will still hold on the shaft and will interface with the gear, then all will be well.


So that is exactly what I'm going to do.

Room will be tight, but a flywheel will now fit in there.

[TiVoPrince]

Block
diagrams really help me to visualize your descriptions and accounts.  Thanks again...

[mmagliaro]

Hmmm.  Ron, as I look at that, what do you think about just replacing that motor with a much longer one?
You've got the room.  This would improve it in a number of ways, I think.   First, that little straight-wound
open-frame motor is not a very powerful design and you could get a much stronger motor that would have
better low-speed power in there.  Second, a longer motor would solve the problem of the long shaft with
the worm hanging out there in space.  I'm thinking a natty Mashima.  You might even still have room on
the back for your flywheel.

Just a thought...

[peteski]

Instead fo a longer motor, why not use a gear-head motor with 4:1 gear-head (which adds length to a motor assembly anyway).?  That would dramatically improve slow speed performance.

[mmagliaro]

Instead fo a longer motor, why not use a gear-head motor with 4:1 gear-head (which adds length to a motor assembly anyway).?  That would dramatically improve slow speed performance.

Well,  I thought of that, but I assumed that Ron would be trying to keep to a moderately-priced
solution.  Mashimas cost money too, but not like a coreless.  And in fact, any spare Atlas or Kato
motor you've got lying around should work well here. 
Plus, I have no idea what the speed range on this engine already is.  If it goes down by 4x,
will it be too slow?

Well, okay, I'll shut up now and wait for Ron to comment.

[u18b]

All great ideas fellows.

On speed, you are spot on.  The current motor runs somewhere around scale speed at full throttle.

The prototype was rated at about 70 from GE, but Milw found it ran best at 60 and limited it to that (though some engineers ignored the speed restriction- you know how that goes).

As for gearhead-- wouldn't I loose a potential flywheel effect?

As for other motors, this one is OK. 
If I could keep cost down when what I have works, I'd like to do that.
Although I'm open to experimenting with motors.

But, I do have two examples of Mashima motors.  One is similar to this one, and the other is a can motor.
The can motor is about 1mm fatter and on first glance actually ran the risk of touching the front Idler truck retention screw- which is hot and would cause a short.



 

[mmagliaro]

Ron,
I don't know what Mashimas you have, but I was specifically thinking of either the
1015 or 1020.  This page has complete diagrams and specs, including the sizes in each dimension:
http://www.hollywoodfoundry.com/mashima.htm

Perhaps your little motor there is narrower than 10mm.  I can't tell from looking.

As for losing the flywheel effect with a gearhead, yes, you would, because nearly all of them
do NOT have a backshaft for a flywheel.  (If only they did, we could have the flywheel spinning
at 4x the speed of the output shaft of the gearhead, which would give you the most powerful
flywheel effect ever!).   But by the time you put a Faulhaber or Maxon coreless in there,
you won't need a flywheel for smooth low-speed operation.  True, you would lose the ability
to "coast" over dead spots in the track, but that's all you lose.

If the top speed on this engine is only 60-70 mph, it sounds like the gear ratio is good and the motor is
probably revved high enough to run well, even though it is small and straight-wound.

I only mentioned it because I've come across motors like that one in brass locos before, and I'm not a fan.

[u18b]

Max,
Thanks.  I already have the 1015.
I'll report back what I find out.

So the original motor here must be about 8mm.

[u18b]

Drive train time.
Stock, I'll worry about other motors later.

I really want to get a flywheel in there.
It will be tight, but I think my favorite flywheel will just fit.

I like the Atlas/Kato/Japan SD7/9 flywheels.  They are hefty, but the also have a plastic insert which means they can be slid onto shafts without beating or pressing.  They are much easier to deal with.



Even though the insert is plastic, it can still be pretty stiff getting it on the shaft.  So I add a little oil to the shaft.



I then slide the flywheel onto the shaft trying to keep it even with the shaft.  Twisting it badly at the start could introduce an uneven/unbalanced spot.
Notice that there is a bevelled edge to it.  That will actually be helpful at the far end, so I am installing it "backwards".  Normally the u-joint hex nut end goes away from the motor, but here it does not matter.



How close?  As close to the motor as I can get it.  Space is tight!  I leave just enough room to get the fine tip of my oiler down there to oil the motor bearing for future maintenance.



Here is the bearings.  I only need one per motor.  Gosh, the one on the left looks a little rough around the shaft hole.  I polish the bearings just like before.



Just like before I gently slide the bearing in circles on worn out fine sandpaper.



I then rub the bearing hard on a piece of wood to burnish the surface.



The mating surface is now polished.  And even though this close up is a bit fizzy, you can see a ridge at the hole on the unpolished bearing.



Bearing slides on with the bigger polished mating end away from the motor.




Wait.  Since the worm can potentially touch the bearing, then its surface should be polished too!



Once again, you can see a huge difference.


I twist the worm on by hand.  Fortunately, it sits deep enough on the shaft to get a good "bite" and is not loose.


Obviously, there is a judgement on placement.  It has to be where the bearing fits into the gearbox slot-- and I want the bearing and the worm to only be BARELY touching each other when I wiggle the bearing.

Here is the gearbox assembled.  Hmmmm.  space it tight.



Getting to the screws on that end is possible- but it is really tight.  If only I had about 1/2 a mm more.


more next time...

[u18b]

If I need more room to get to those screws....

The problem is the flywheels.  They cannot move any closer to the motor.  If they did, then I would no longer be able to oil the motor bearings on the flywheel end.

But!  I could move the whole motor to the left.

The way to do that is to remove everything back down to the L-bracket motor mount.
That mount could be moved to the left if the screw holes were opened up.



A motor tool works a lot better than a file for this task.



In this photo, right hole is stock, left hole has been adjusted.  Notice the hole is opened UP in this photo.


Repeat on the other side.  Clean it up.  Reassemble.

Wow!  It worked.

[u18b]

We are almost ready to give the new train a test run.

But first we need to talk about polarity and a trick.

1.  Trick.  Many of you would know this, but it might be new for some.

The most common materials for screws are steel and brass.  There are others, but those are probably the most common we will see-- and we see those two in the EP-2 (and other Kumata locomotives).

In this EP-2 kit (and probably many other KMT locos), the steel screws have Phillip"s heads and some (like the coupler screw) are slotted for a flat blade screw driver.

The reason this matters is that most of the construction screws are steel -- and thus can be easily HELD IN PLACE by magnetizing your hobby Phillip's screwdriver.  The way you magnetize steel is to draw it over a good magnet 7 or 10 times.

Since I assemble/disassemble/reassemble etc, being able to hold these little screws on the screwdriver is a lifesaver and helps me keep my sanity.



2.  Polarity

The EP-2 is a slightly more complex loco when it comes to polarity.  That's because:
a.  large number of wheels
b.  the individual powered Cabs (each a "loco") run back to back
c.  the shells are electrically hot and thus you can have a short if a spot of bare metal around the drawbared boiler room touches when the Cabs are wired incorrectly.

Remember I told you to construct the trucks oppositely  (solid wheels on left or right).

That's because when the whole loco is assembled, the solid wheels will consistently be on the same rail for their truck.
The EP-2 draws power from one rail from the GEARED truck and power from the other rail from the IDLER truck.

So since we have two "locos" running back to back, they need to be lined up correctly.

Here is a simple (fuzzy) scan I took of the bottom of an NJ Brass EP-2 from '83.  All EP-2s are constructed the same.


The colored marks are where the solid wheels are.  So if there is no color, there is an insulated wheel.
Further, I color coded like DCC.  Right rail red, left rail black.
So in this photo "front" is to the right.  And remember that I placed a RED jumper wire on the front Idler truck pad I made.

Notice the geared power trucks have to be constructed oppositely so that when they are reversed, all solid wheels will be on the same side.  Same for the idler trucks.

NOTE (again):  we MUST do it this way because ALL the loco is electrically charged.  The main loco frame AND the brass shell are all charged to the power trucks.  So it IS possible to have these Cabs run fine by themselves, but when you connect them all together it won't run because of a short.

Now-- we have a new puzzler to think about.  These two cabs are MIRROR images of each other.  And then turn back to back.

Let's think about 2 Atlas GP40s. They are constructed IDENTICALLY (and all wheels pick up electricity).  So when they are facing the same direction, they run the same direction.  But when we turn one so they are back to back--- they STILL run the same direction.

Why?

Because the reversed loco motor is now drawing electricity from the opposite direction.  The + rail (in our imagination) is on the right side for the front loco.  But the + rail is on the LEFT in the reversed loco.  So the reversed loco runs backwards.

This is a LOOOOONNNNGGG way of explaining why--- if the wheels are NOT identical on an EP-2 Cab half (they are reversed), then the motors must be flipped to each other.  One must be "up" and one must be "down"  (assuming the motor wiring is the same (for example, frame to the left pole, Idler truck to the right).  If the motors are NOT flipped, then the cabs will run in opposite directions instead of together (don't ask me how I know    )

I hope that made sense.

There is a CASTING mark on ONE side of the stock KMT motors.
Here it is.



And here it is missing.


So with that casting mark, I can keep track of one motor UP and one motor DOWN.

We will be ready to get this thing running next time.