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

[u18b]

Through the years, I’ve used flywheels from Atlas, Kato, or Life Like locomotives that have a hex hole.    You might need to pull one off of a motor (as I have done before).



With a hex hole in the flywheel, you now have a couple of options. 

You could use a u-joint from a Kato loco from a few years ago (like the old U30C/SD40/SD45 etc.).  This has been one of my favorite solutions through the years.   You used to be able to buy these easily from Kato.   



The same green cup accepted a floating hex rod of differing lengths.



If you can’t find what you want from Kato, you could search ebay.

Atlas has also made a good u-joint.  These also work well

[u18b]

After installing the flywheel, you will probably need to cut the Kumata worm shaft to proper length.

However, my favorite procedure is to Beardenize this end of the loco.   This is a term people have given for a procedure of mine for removing the inner bearing block from a wormshaft with no bending u-joint.
See my article:  http://u18b.com/wp-content/uploads/2019/10/Bearingblock09.pdf

First, I pull the gearbox apart.  This might be hard.  Kumata learned that the bearings can be too loose, so they began using epoxy to hold it together.  That was the case in this E1 set.  I had to very very carefully use an Xacto #11 to pry the haves apart (and do it without cutting myself!)

This is a good time to note that the steel KMT uses in the worm shaft is VERY soft.   I have had a u-joint cup that was stuck on.  I would grasp the shaft with a pair pf pliers to pull the cup off- only to see that the pliers had damaged the shaft!   Thus I have determined the best course is to simply replace the shaft with something just the correct length.

I very carefully drive out the old shaft.   Chamfer (round) the end of the shaft before it gets near the worm so  you don’t gouge out the worm getting it off.

For a replacement shaft, I found stainless steel tubing works well.  I have some in the aprox 1.5mm shaft size.

My worm is not real tight on the shaft so I add some superglue on the end of the worm away from the outboard bearing.

Now we need a hex interface.  With no inner bearing, you cannot use the floppy Kato joint described above.

But Atlas has made several variations through the years for several locos.  Here is one- though sometimes you might need to remove some flashing (as seen here).



I place an Atlas hex nut on the end of the shaft.  I then test fit and cut the shaft more if needed. 

As described in my article, when the shaft just right length and all assembled, there should be a only tiny amount of lateral play in the worm shaft.  No play and there is a bind.  Too much play and there can be a rattling noise.   The hex nut should almost bottom out in inside the flywheel.

Time to assemble everything again (with the weight).  The loco should run smoother and quieter.





Beardenizing the loco like this greatly reduces noise.  This is especially true in longer locos.   If you have a long KMT commuter set (Silverliner, Washboards, etc), then you REALLY need to do this.

I added flywheels to both the A and the B unit.

[u18b]

Electrical Issues

This portion is slow because I’m continuing to research sources of solutions.

For example, I’ve ordered some M1.4 Nylon screws coming from Japan.  I don’t have high hopes, but you never know.

Also, I have contacted two firms to get bids on shoulder washers. 



These are the measurements I submitted.

A  Diameter of the top surface-   2.55mm
B  Thickness of the lip    .60mm
C  Outside barrel    1.85 mm 
D  stock is .75mm 
E  inner hole for the screw  1.35mm

This is such a small job (tiny object- 100-500 run) that I’m not sure how interested they will be.

If anyone here wants to draw and produce these on Shapeways… or even make the file available for free to all here, please speak up. 

@narrowminded graciously made some for me,  one at a time on a lathe- but that does not seem feasible if there is a need for 100 or more.   I think a commercial solution would be best.   The material must be not too brittle and not too soft.

[Chris333]

Here is the file:
https://www.thingiverse.com/thing:5974763

Had to convert it to inches 

[u18b]

Wow Chris.  That was fast.  Thank you.   

@chessie system fan (clearing throat)..... Dad could use a favor....   

[u18b]

So we will proceed- because there are a number of things you can do.

As explained before, the problem is shorting to the frame and shell since everything (except in the B&O E’s) is electrically charged.

Now, the real problem is generally the rear truck in the E units since the rear truck is electrically isolated from the frame and charged oppositely.   If the front truck touches the frame, there is no problem.

However, the other problem is the wheel flanges.

So, on almost all Kumata brass, I find it beneficial to insulate the bottom surface of the main frame.

Begin by pulling the shell and remove the trucks.  The trucks are retained by a headless screw.  Be very gentle when removing.  I also remove the screw for the weight if needed.

Clean the bottom surface of oil if needed.
You can see in this shot the tell-tale sign of wheel flanges scraping.  The chrome plating is covered in clearcoat and you can see where the clear is rubbed off.



I then take plain old clear packing tape and stick it to the bottom.  Starting at the fuel tank and excess forward.




Now, obviously we need to cut the tape for all pass-through parts.  So here I am cutting the tape so the truck geartower will pass.  I’m cutting at the frame.




I then have to cut out the holes for the screws which pass through to hold the shell.  As well as the screw hole for the weight.





Just making this simple change improves many KMT locos.

[u18b]

The next solution is simple and effective.
Shim the shell to raise it away from the trucks.

I use Micro-Trains washers.  The edges often need to be trimmed.  They're about .005" thick.




A little superglue hold them down.



If you have a KMT Trainmaster, you absolutely MUST do this since clearance is WAY too close on that loco.




Now, after doing this…. I noticed the gap was larger at the front truck than rear.    If that ever happens, you should check to see that the clear acetate insulator is present under each gearbox- because without it, it changes the height of the shell.  In my case, the insulators were present.



Closer examination revealed a slightly bent frame forward of the fuel tank.  Since this is plated, I didn’t want to risk damaging the integrity of the plating- so I did not try to bend it straight.  I simply removed the shim I had installed in the nose- which lowered the nose and the gap.  Now all is good.


Unfortunately, while this helps many electrical issues, it does not solve them all.  In my A unit, the rear stirrups are soldered just a hair too far forward.   This means the rear truck can short near the fuel tank skirt or the stirrups.



Now, on an E unit, raising the shell gives you a few extra microns clearance because of the angle of the skirt.

But what about the stirrups?

Well, we have four sources of play which we can manipulate.

Shell
gearbox
truckframe
truck

Let’s look at each one.  The first three are all similar in that the screw hole is a few microns bigger than the screw.

#1   So on my A unit, I loosen the three screws (not remove) and press the frame/mechanism forward toward the nose.   Then tighten the shell screws.  That helped.   But not enough.

#2  So then I pulled the shell and loosened the screws on the rear gearbox.  I then pushed the gearbox toward the nose (moving the rear truck forward) before tightening the screws.  That did not gain me much on this loco because the gearbox had very little play.  Of course I repeated #1.

#3.  With loco assembled, I flipped it over and see two screws holding the rear truck sideframes.  I loosen these screws and slide the sideframe toward the fuel tank before tightening.

So #1 + #3 + raising the shell did the trick.  The A unit runs perfectly now with no shorting- even with the inherent unevenness of grades.

[u18b]

Now, if you STILL have not gotten the movement you need, you have two more options.

You can take a motor tool and open up the holes to give you a little more play.  The best candidates are the truck sideframes and the gearboxes.  In my case, I did not want to break through the plating so opening up holes was not an option. 

That meant #4 above.  Addressing the truck play.

Now, I did not need the following since my shorting stopped, but I tested it to make sure it works- and it does.

The trucks themselves have some gap between the geartower and the gearbox sides.  Thus, one solution is to place a barrier to remove some of that play.

In my example, I moved the mechanism into the shell farther.  This helped the rear truck clearance, but now the front truck front edge can hit the curved skirting of the front plow at the nose.

This is not a crisis electrically since the truck and the shell are charged the same.  But just for fun, let’s see if we can correct this. 

You can see in this shot , you can see the frame hole is larger than the gearbox.  I want to place something on that gearbox edge.



I found some styrene that was just under the thickness of the frame.  I then trimmed and filed to get a good shape.  The side toward the truck is curved a bit. 



After test fitting and making adjustments, I superglued the styrene to the gearbox.  Of course I did not use much- applying a tiny dot with a fine wire.  You cannot see in this shot, but I also ran an Xacto blade and trimmed the edge about 45 degrees so that the gears will clear the styrene.



This procedure worked.  It moved the truck rearward toward the fuel tank and it now clears the pilot skirt edge.

[u18b]

The last electrical step to take right now is to clean up all connections and check solder joints.

All solder was strong on this loco, but I had some typical corrosion.



So all the screws and brass tabs were cleaned.

This loco set now runs perfectly with no shorting.  Adding sound is in my future!

[chessie system fan]

So how many of the thingy's do you want?   

[u18b]

So how many of the thingy's do you want?   

20 would be a good start!

 

[wm3798]

This gives me hope.  I had my eye on the B&O EA set for some time, but have hesitated based on the Spookshow review.  I feel like it might have the best of the E unit drives now, and with a more robust motor and perhaps a flyweel, it could be a strong contender...

Lee

[u18b]

This gives me hope.  I had my eye on the B&O EA set for some time, but have hesitated based on the Spookshow review.  I feel like it might have the best of the E unit drives now, and with a more robust motor and perhaps a flyweel, it could be a strong contender...

Lee

Hi Lee,

Yes, it is the best of the KMT E units.  I'll be talking a bit more about the B&O EA set.

And bringing  the E1 up to  the EA standards will be where I'm going soon with this thread.
Waiting on a few parts to come in.

[u18b]

No word on anyone producing the shoulder washers yet.

So what can be done instead when you have some insulators that are damaged or destroyed?   You must electrically isolate one of the gearboxes from the frame.  I’ll cover 4 solutions and evaluate them.

1.  First, I have used heat shrink.   Not desirable since it is not strong enough.




2.  I have used an awl and poked a hole in a business card.  The awl pushes some paper thru the hole and sort of centers the screw in the hole and provides a little insulation.

Works- but not a good long term solution.

You can see the white card pieces in this shot of a Trainmaster.



3.  M1.4 insulated screws are hard to come by.   But 0-80 screws are common.    This is a pretty good solution.    It requires you to take a tap and thread the stock M1.4 screws to 0-80.

This was the same Trainmaster as above.   This is a MUCH better solution than the imprecision of cards.



However, while this is a generally good solution, I did not want to do this on the AT&SF E1 set.  This set is chrome plated.   Tapping for 0-80 screws would cut through the plating- which can then lead the the plating peeling once broken through.

4.   Thus I found a source for M1.4 insulated screws.

The company home office is in Japan.  And they have an office in USA.   They make a resin kind of screw.   Much stronger than the old Delryn screws Kumata originally used in early locos.  And stronger than Nylon.

This is a destroyed screw from a KMT SD40-2.






This is the screw I wanted- but they were out.   It has the largest head.

https://solidspot.com/shop/index.php?main_page=product_info&cPath=143_380_216_220_330&products_id=2471

Model: RENYLM146

Reny is the screw.
LM is a large head.
M14 is size (M1.4mm)
and 6 is the length (6 mm). 

I figured I’d cut off excess.

So rather then wait, I bought the screws with the smaller head.

https://solidspot.com/shop/index.php?main_page=product_info&cPath=143_380_216_219_327&products_id=2469

They are a little pricey but you get 100 (shipping is 10 bucks- but there is no extra charge if they have to get them from Japan).



These are great screws.

I did notice a problem.  They are Phillip screws, but the center cut is not very deep.  A typical pointed Phillips screwdriver will strip the head.   So I found it is actually better to use a correctly sized flat screwdriver.





These screws are so tough that I could not easily cut them off without risking the X-acto knife jumping dangerously.

So I scored them….


Then broke them off.   Any extra is easily removed now,



I admit- I’m very impressed with these screws.  I can now use them as a method to replace the shoulder washers when damaged.

[nkalanaga]

Xuron flush-cutters and some light filing?