Kumata brass E/E1/E5/E3/E6 Rebuild Project w/ DCC & Sound KMT

[u18b]

I’ve spent a lot of time with N brass Kumata locomotives.  In fact, some of you helped me in my research.  Thank you.    I’m still in the process of writing a “book” in pdf format.  About 80 pages are written so far with more to come (including material from this thread).  I got delayed because of the great EP-2 revised version I discovered and am slowly building (which is an extension of the Kumata project)

In the last year or two, I obtained a plated E3/6 set and an AT&SF E1 set (the better 2nd version).  It’s time to fix these up with the goal of eventually selling them with the research accomplished for the book.

So in this project, we’re going to see how I improve these locomotives.  In all, Kumata brass often gets mediocre reviews.  In fact, Spookshow was not impressed- at first.    But the simplicity of the design allows for improvements- if you know what to do.  I demonstrated this to Mark and he raised his ratings a notch with improvements made.   

These locomotives are about 30 almost 40 years old now.   This thread concerns specifically the E units, of which there are 5 (well 6), though some of these techniques apply to other Kumata brass.

B&O E   (this was the last  E unit produced by Kumata)
AT&SF E1 first run   (this was the first produced and came with a dummy B unit)
AT&SF E1 second run
E1 B unit revised chassis (to power the dummy B)
E5
E3/6

I’ve worked with everything on that list.

As with almost all Kumata brass, the biggest problem is correcting electrical shorts (which is also the problem with some Samhongsa brass as well).

The shorting is so bad, it’s a deal breaker.  Forget DCC and especially sound.   You often can’t even run some Kumata brass on anything other than perfectly level straight analog track.  For example, the worst offender may be the Trainmaster.

The reason shorts are a problem is that the entire frame is usually electrically charged (not a rare thing in brass locos)- thus when an oppositely charged truck touches the frame you get a short.  On the list of E units above, only the B&O EA/EB set does not have a charged frame.

There are a few other problems with these E units as well.

More to come over the next days and weeks.

[NorsemanJack]

I'll be following.  E units of all vintages are great, and anything E6 or earlier is especially attractive (see my avatar).

[u18b]

This thread will not exhaustively cover every E unit, but I’ll show you a good bit.  And besides, there are a lot of design similarities.   The specific example I’m primarily working with is an AT&SF E1 second run set.  I’ll be correcting problems and then adding sound.  Since the designs are similar, these procedures could be used on others.

Let’s start with the chassis variations of all the E units.

E1 first run




The E1 first run is the poorest design of the lot and it shares the same design as the SD40-2.  It uses a knock-out pin and the trucks are very difficult to disassemble from the chassis. 




Furthermore, the gearbox halves only have two screws instead of 4- which allow them to come loose from the frame and each other. 



Kumata also used plastic screws on one gearbox for insulation.  The first things you should do after disassembly is:
--open up the frame a bit with a file so you can get the trucks out in the future without removing the knock-out pin.
--drill holes in the frame and gearboxes for additional screws.

The other problem is the dummy B unit.   The A unit does not have enough traction to pull both the dummy B unit and a bunch of passenger cars.  That’s why Kumata released the powered B unit chassis later.

Rebuilding one of these first run locos is a more challenging task and not specifically covered here.

The motor is offset and entirely supported by the nose gearbox. 



One thing you can do is shim the motor to support it and take some of the stress off the worm bearings.   Or you could make an L-angle mount and drill/screw it into the frame.

The front gearbox charges the frame and the frame charges the motor frame.  Since one pole has no insulator, the motor can run. 

Note:  the motor is on the front end.

Because the motor is offset, there is a long worm shaft and weight.  That long shaft is a prescription for loud noise because of wobble.


The E1 B power chassis



Even though it was not released next, the power chassis has a similar look with improvements.
The motor is still offset, but now has a support bracket.  The long worm shaft also has a support added as well as employing a different u-joint (dogbone).

The motor is still on the forward end.  And the trucks are retained by a headless screw- NOT a knockout pin.


Purchasing an ATSF E1 set

To be honest, the E1 first run set is not desirable.   Do not purchase unless you get a look at the underside of the B unit.   If it is a dummy, I’d stay away unless you can power it yourself.   

If you see that the B unit is powered- how can you know that this is first run (with the power chassis installed) or second run?

The answer is the box.  They have different labels.

The first run does NOT have a number.  It also has the KMT logo.



The second run has #0249




E1 second run, E5 and E3/6 all share the same basic chassis design.

E1


E5


E3/6



The motor is now centered.  There is one weight.  Only one gearbox is insulated so the frame and shell are charged.  And all trucks are retained by a headless screw.



I have tested two E5 sets, and both were amazingly quiet.  It’s probably a co-incidence since I can’t see what would be different besides the closed frame motor.

The weight is in the rear.

The B&O E set is a bit different.  The driveline is the same, but now two weights are used and both gearboxes are insulated.  Consequently the frame and shell are NOT charged.





By now you may have noticed that the motor poles always go the front.  This mostly matters when you are dealing with a B unit and forget which orientation it follows.

[u18b]

Test Case:  Improving an E1 A & B 2nd run



I first do a survey and see what I am facing.   I pull the shell.
This set is not too bad.  I have seen much, much worse.

Here are the problems with this set.  These are fairly common problems with Kumata E units.

Trucks sometimes short on the shell or frame. 



One of the worst offenders is the Kumata Trainmaster.  Here is one crossing a turnout.  In the process, the truck shorts on the frame.

The shorting makes DCC, and especially sound, impossible.



Out of 8 u-joint cups in the E1 A & B unit, 6 were cracked.   This is average.  I have never seen a Kumata E unit set with all u-joints in perfect shape.



Driveshaft alignment.  This is mostly noted by the u-joint between the motor and the worm which are not perfectly aligned.

This set was slightly off, but here is what I found on another KMT (Kumata) loco.



When the shafts are not aligned well, the end result is a locomotive set that is loud and runs poorly. 

You should always inspect the insulated gearbox and the shoulder washers.
At least one gearbox will be insulated from the frame.    This is done in two ways.

First there is a clear acetate under the gearbox- as seen here.



Then, the screws are isolated from the gearbox by a plastic shoulder washer.




The insulated shoulder washers on the insulated gearbox may be damaged.  Here is a good one and a damaged one from another KMT loco.



On this set, yep- there is a damaged washer which is close to failing and creating a short.   The error people make is cranking down screws in the delicate plastic.  They also don’t make SURE the parts are all centered correctly before torquing the screw down.

[u18b]

While we are here, you should also inspect the gearbox metal,   Sometimes there can be Zamac rot.
E units usually don’t suffer from this, but I would BEWARE ever buying an Alco where you cannot see the gearboxes and the truck frames.  The metal in the Alcos was a BAD batch…. As seen in this RSD-4/5 truck frame.



And this RS-2.



When things have been really bad, I have created my own cast gearboxes.  Thankfully, I don’t need them here.   When a truck frame is seriously bad- the loco may become a shelf queen.



There can be corrosion on the screws- especially the one at the motor tab.







You can also have broken wires which have come loose from the motor or the gearbox tabs.  This set had none, but I’ve seen it before.  I assume it was a cold solder joint, or poor fluxing, or corrosion, or all three.

Like here:



Even if the joint is in tact, there can be so much corrosion, that the conductivity is greatly reduced.  I had some clean-up to do.



Oh- that photo above also shows a mis-aligned u-joint can be side-to-side, and not just up and down.

You should also check the excess screw length on the gearboxes.  In my E1 set, there was one screw that was longer and projected out a bit- but not excessively so.



Hopwever, look at these two EP-2s.  This first one is a photo taken in Japan of a 2000 release.  Follow the line down from the cab windows to the frame.    Those black spots are the protrusions of absurdly long screws.  While, in this case, these will not create a short, they are really ugly and could be a snagging problem.



But now look at this NJ EP-2.  See on the far left….. that screw projecting upward from the truck?   That is an absurdly long coupler screw.  This is the insulated truck.  So if there is uneven track or some other obstruction, if that screw goes up and touches the frame, there will be a short.



You should also check for a bent frame.  I once had an RS-2 that would not run because the frame was bent and caused a bind in the drive train.  In this set, the A unit had a slightly bent frame.  I didn’t notice it at first, but when I saw the loco on the track, I could clearly see that the shell sat lower in the rear than in the front.



One other thing to check is the tightness of the gearbox bearings on the worm shaft.  Excessive wear in the worm bearings is manifested by a worm shaft that wobbles a lot.  The bearings don’t hold the shaft tightly.  Mine were fairly tight because this was a lightly used set.

You can check in two ways.  First, just grasp the worm shaft and see how much it wiggles.  Second, with the u-joint straight, turn the motor with your finger (or run at very low speed if it’s possible) and watch the worm shaft.  Is it true?  Or is there eccentricity to it?

Mine were fairly true.



You will also want to remove the trucks and inspect the bottom surface of the frame- because it tells a story.  If you see semi-circular wear spots, they can also be indications of shorts.  In the next photo, you can see two arcs.   The one near the fuel tank is the tip of the truck frame rubbing.  Track work has to be pretty bad for that to hit.  However, the inner arc is the wheel flanges hitting.  If this is the insulated truck, then it will short on the frame.




This concludes our tour. 
I will have to correct all these problems that I find in the E1 set- before we even think about adding sound.

The first priority is smooth, quiet reliable running.

[Dwight in Toronto]

Ron - thanks for taking the time to prepare such a thorough presentation. 

I know nothing about Kumata, and it is unlikely that I would ever acquire such a thing, but your tutorial was still of interest.  Just curious - when were these brass models produced?

[Dwight in Toronto]

Never mind - I see now that you mentioned that they are approximately 30 years old. 

[u18b]

Dwight,

Here is the specific info.  All sets A and B unit except B power chassis

E1  1st run,   AT&SF painted,  Oriental,   11/1982  (B unit dummy)
E3/6   undec, brass or plated,  Hallmark,   4/1984
E5,    undec,  plated,       Hallmark,  4/1984
E1  2nd run,  AT&SF painted,  Oriental,   5/1984
E1B power chassis,  Oriental,   6/1984
E      B&O painted,  Oriental,  10/1985


That list has lasted fairly well. 
No one has even made an E1 (though BLI has made it in HO- maybe N one day).
BLI has made a nice E3/6.  Atlas bought Life Like, so maybe they will make an E3/6 one day.
Kato makes a nice E5
And no one has even made an E for B&O.

Of course, I'm speaking of commercially produced complete locos.  You might be able to find 3-d prints of some of these.

[nkalanaga]

The newest one will be 38 this Fall?  Definitely old-tech!

I have some Hallmark diesels of similar age, and they all run very nicely.

[u18b]

The newest one will be 38 this Fall?  Definitely old-tech!

I have some Hallmark diesels of similar age, and they all run very nicely.

@nkalanaga   haha.  You are correct.  These are almost 40 years old as a group.
I edited the first post.

[u18b]

U-joint Repair

Before I get to electrical (I just ordered something and want it to come in)…

As stated above, cracked u-joints is a common problem for KMT locomotives.



Now, on this locomotive set, the cups were still holding, but usually there is a loss of grip.  So they need to be replaced or repaired.

One way will be to add flywheels, which we will talk about in the future.  But first let’s talk about no flywheels.

I have commonly cannibalized old locos- even vintage locos.   While the motor from a 1970s loco may be crap, the u-joints may be useful.   Here is a KMT loco where I installed a new u-joint from one of those old locos.  Note the new joint on the right.



However, it is possible to repair those old KMT cups.
These u-joint cups just happen to to be about 5/32”.  Therefore, K&S brass tubing of that size can be used to make a little band that goes on the outside.  I got this idea from @peteski in a gear he salvaged a long time ago.



This is not a perfect solution because the shaft is spinning and if the band is not perfect, it can create some wobble and noise in the shaft.  So it is important to make the finished band as straight as possible.  People with a lathe have an advantage here.   Here is a decent one with only a motor tool.



I press the band onto the cup.    Then add just a little superglue to the back side of the band once in place.   In fact, this band is a little wide and could have been made a bit narrower.






I have found so far that this is sufficient to cause the u-joint cup to hold onto the shaft sufficiently tight.

I had a good cup and a bad cup.  Therefore, I placed the repaired cup with the band on the motor shaft to reduce the effect of any possible wobble.



We will look at other solutions in the future.

[peteski]

Looks good Ron!
Thanks for the mention. The brass band fix works really well for me, and should permanently prevent the plastic part from cracking again in that high-stress area.

[Simon D.]

I bought an E1 second run from Brass Trains a few years ago - the UJ had been replaced with a silicon tube - seems to work well.    Its the shorting that is the problem!  Looking forward to your solutions immensely.  Apologies, it's packed away at the moment, so no photo.  I'd be interested to know what you think about using these tubes.


Great stuff

[peteski]

Silicone tubes, over the years, have been used in many models (especially brass ones).  When they work, they work fine, and even provide a soft and quiet coupling.  The problem can happen if either the tube is not tight enough on the shaft, or oil gets on the shaft. Either way the tube can start slipping causing drivability problems.  But cracked universals will have the same problem.  If in your case, if the tubing works well I would keep it.

[u18b]

Flywheel and Worm Shaft Mods

I like to add flywheels to Kumata brass if possible.  This not only smooths out performance a bit, but it also solves the U-joint problem.  Furthermore, it can free up two u-joint cups per side.

For example, here is a flywheel added to a KMT Trainmaster- two different variations.






In the past, I have installed two flywheels in each E unit.  This sometimes required trimming the lead weight- which is not a great loss since the flywheel adds weight back.

In this example, the weight was removed altogether.



Here is an example with the weight trimmed.




In this case however, since I plan to add a sound decoder in the E1A, I’ll only install one flywheel.  Because the sound decoder is sizable,  I’ll install a flywheel on the short side (with the motor support) leaving the larger side for the decoder.  So in this photo, flywheel on the right and decoder on the left with the weight removed.