Best Of New Brass EP-2 assembly & Mod clinic

[nkalanaga]

"I suspect that if he bought a 100, the price per spring would be much less than $100."

I imagine you might get a hundred for less than a couple hundred all together.  The original comment was "6 or 7 dollars apiece", so a hundred would be $600 to $700, not as bad as $100 each, but still prohibitive.

[VonRyan]

I could go for a good extension spring. Especially the one Ron used since it has a great travel length. Just wondering if my Arnold solenoid can sufficiently pull it while energized.

-Cody F.

[u18b]

Ok.  Let's take a pause and talk more about mechanism theory and practice.

This thread is primarily about the new 2003 EP-2 by Kumata.

However, there is a lot that can be learned that helps improve the 1983 NJ Custom Brass version as well.
Aside from details, the number one difference between the two is the power truck.

The new version has all 4 axles powered.

The old 1983 version has only two axle powered.  And that is a HUGE problem in these locos.

I'm repairing a 1983 version right now, and I've hit an interesting observation.

Let's start back with that movie I made.

Notice that an individual Cab tends to run fairly well FORWARD.

But traction is DRAMATICALLY worse in reverse.  That is a consistent observation.  Seen it multiple times.

But why is that?

Let's study it.

Here is the 1983 power truck.


The gear tower is off-set at one end.  The two axles near the tower are the two geared/powered axles.  The other two axles are idler.

[u18b]

Now, in an ideal world- (the world of perfection  )

All wheels would touch the rails exactly evenly.  Thus our two geared axles would always touch the rails.



But the world is not perfect.

In this example, the frame has a little bow in it.  Either manufacturing defect, or from slight Zamac expansion over 30 years.
The end result is that the true weight is on the outer two axles.
Well.... that means a loss of traction on axle #2 and we are really riding on only one powered axle-  the #1 axle on the far left.



So my initial solution was to get a file and open up the holes on the idler axles (#3 and #4).
That way, when the weight comes down the geartower, it would be distributed 100% to the geared axles.  The idlers would bear no weight.



And trust me, this does indeed help.  Traction is improved.
Here is evidence at the 2:14 mark.

You would think (theoretically) that it should not matter how much filing I did using this basic principle.  In fact, as long as the idler flanges don't have room to lift over the railhead, we have tons of room to work with.

But..... that theory would be wrong.  There is another variable.  (thankfully I did not open up the holes on this current model excessively!)

What I said above is absolutely true about opening up the idlers and placing 100% of the weight on the drivers..... as long as the truck is at rest.

But once the truck starts moving, another force is at work.

Torque/friction.   

Torque/friction is what explains our observation that (all things being equal) the trucks seems to have better traction forward than reverse.

Since friction is not at zero, when the wheels turns, the truck frame itself has force applied to it too.

Look at this diagram.
When the truck is moving forward (to the left), the wheels are turning counter clockwise.  And friction and/or torque is causing the truck frame to lift up on the right side-- or turn counter clockwise itself.
But since the pivot point is offset on the left side, the effect is minimised.  We still have traction on the two powered axles.



But reverse is another matter.
When travelling in reverse (to the right) the forces are opposite.
Wheels are turning clockwise.
And the whole truck frame wants to pivot clockwise too.
This places a DOWNWARD pressure on the idler end.

But wait.  We removed metal from that end, so the truck frame can ACTUALLY pivot in that direction- even if only a little bit.
Well, when the truck pivots clockwise, the #1 axle on the far left LOOSES traction.
So now the truck is only riding on axle #2 and #4-- with only ONE axle being powered---- thus loss of traction.

[u18b]

Now, what I've said is theory/explanation.

What led me to it is actual observation.

I was frustrated that I was not getting the traction that I wanted/expected with my mods.

So I experimented.

I removed the idler axles completely and ran a Cab.

When gong forward (left) this photo shows another force at work.
The WEIGHT of the frame itself (since the balance point is offset to the left).
Friction/torque (purple) tries to lift the idler end.
But the weight (yellow) of the frame itself is pressing down.
So to some degree, these two forces offset each other.... and reasonably good traction happens.  Driven axles  are both on the rail and pulling.



But once again, going in reverse (right) is a different matter.
You are witnessing what actually happens when the power is turned up in reverse.
Now, friction/torque (purple) AND weight (yellow) are BOTH pushing in the SAME direction.
This actually does in fact pivot the truck.  And the #1 axle can come OFF the rail with no counter-acting support.
So once again.... now we have only ONE geared axle on the rail.... and a loss of traction.



Obviously, this is pretty exaggerated with no idlers present.
But even with the idlers present, the effect happens ... even if it is only a few microns.
But those few microns are enough to take pressure off geared axle #1.

So I needed to find a way to counteract these forces to provide for better traction on axles #1 and #2.

[u18b]

More later this evening.   

Oh!  And a message to any possible manufacturer who might be reading this....

DON'T design trucks off-set like this! 

[peteski]

More later this evening.   

Oh!  And a message to any possible manufacturer who might be reading this....

DON'T design trucks off-set like this! 

That was a very educational explanation. Thanks Ron!

As far as manufacturers nowadays making trucks like this, I don't think that you have to worry (especially with mass-produced plastic models). I think that they know better (I would hope).

I also think that brass models like that were designed to be displayed in a cabinet (and to provide countless hours of fun to people like you who make them run well).    The running mechanism design was IMO an afterthought.

But I think that the brass designers still design more for show than for go.  I recently had a chance to examine a $1300 N scale brass steam loco.  it was just produced - a brand new model for 2013.

http://www.reynaulds.com/products/Fulgurex/1158d.aspx


The model is stunningly gorgeous!  It also comes equipped with latest technological advancements: a Coreless motor, and a DCC decoder.  You figure that this would indicate that the mechanism is also ready to run.  Wrong!

I was only able to give it a visual/tactile examination (no running). But based on my experience, this model will not be a good runner without some modifications.

Front truck pivot is very stiff (both sideways and vertically).  It is also fairly light with no spring to keep it in positive contact with the rails.  It will most likely derail on turnouts.  Funny thing is that it picks up power from all 4 wheels!  Nice electrically, but the extra drag from the pickup strips will most make it even more derail-prone.

The trailing truck is a disaster. It is so tightly attached to the loco that it doesn't move at all. In this model, it was actually tilted slightly off-center, causing the entire loco to "crab" slightly.  I was able to force it to line up with the drivers, but for the loco to run properly, the truck's pivot will have to be modified to allow the truck to move freely.

Tended trucks are also very stiffly mounted. They can barely twist (probably due to stiff pickup wires), and have some side-to-side tilting ability. But they do not have any front to back tilting ability. This will most likely case some problems as the loco starts ascending or descending a grade.

The only part that appears to be designed well is the drivers and gear train.

Looks to me like there is plenty of room for mechanical improvements (even on this brand new brass model).  I think it is safe to say that brass manufacturers will provide plenty of projects for people like you or me to keep us busy now and into our retirement. 

[u18b]

Now to solutions in a moment.

Here is how this all started.

You will remember that one of the fatal flaws in the EP-2 design (both the old 1983 and repeated in the 2003 versions) is the jumper wire from the front idler truck.

There is just no way around it.  This is a bad idea.  The wire WILL eventually break.  It is only a matter of time.

If you look over Spookshow's listings, gives gives an A rating to only a few locos that do indeed run very smoothly and quietly.... but they have wires!

Like the PFM F40PH.



Or the Life Like FA1.



These locos run great.... but the wires WILL break sooner or later.

I was trying to cure this by employing a wiper design in these new EP-2s.







This works great on these new 4 geared axle power trucked EP-2s

But when I did it on the old EP-2 I'm repairing... I was in for a surprise.

Here is a side view of the technique.



Here is what happened in a recent try at this technique.



The wiper presses up at the blue arrow.

But if the wiper was a little too stiff, it could lift the rear end of the whole frame (yellow).

When that happens, we lose the electrical contact point (red) because the gearbox MUST interface with the main gearpin/screw.  Part of the electricity runs through the metal frame itself.

So now the loco won't run!

Weight, of course, helps push all this back down.  But this still got me to thinking......

What if I could move that wiper to the FRONT?

So that is what I did.  Space was tight, but I did it.



Now look at the new forces.




The wiper presses upward on the nose (green).

Since the truck becomes a fulcrum point (purple)...
This now causes a downward pressure on the rear (red). 

This is all good!  Better electrical contact and better weight/pressure on the power truck.

But wait!

With the wiper moved from the REAR part of the front truck...... all that space is now available.

Time to try something else I've been thinking about.  A wiper on the REAR power truck.

By placing a wiper at the forward part of the power truck (yellow) I place a downward pressure on the front edge of the truck (where the traction happens)...

And this places a lifting effect on the rear of the truck (green).



This simple change counters the loss of traction when going in reverse as described above.

Success.  And the icing on the cake is a little better electrical contact so that I no longer have to rely 100% on the gearbox contacting the main gear retaining screw/pin.

[u18b]

Here are some more photos of the changes I made to the pickup system.

The board is the max length.
Divided electrically into two sections.



Screwed to the frame.  Note that the screw is not isolated from the rear (right) portion.  This is now where the rear truck wiper will pass.



The pad for the front idler truck gets its jumper wire up to the wiring harness.
The black truck bushing is also installed.



The pick-up wiper is soldered to the front (removed from the rear).
Had to be careful.  The pilot is soldered to the frame right at the edge of the frame.  I did not want to overheat the area and have it fall off!
The pickup is from an Atlas VO-1000.  Just heavy enough to work, but still very light.



For the new rear pick-up wiper, I was able to just place it between the frame and the sideframe piece.  The screw holds it tight.  This wiper came out of my parts box.  It is an old wiper from a passenger car I think.



This new system really works well.  And I now have more electrical contact than just the gearbox/pin interface.

[peteski]

This continuous improvement is commendable!  Very nice job Ron!

[u18b]

Thanks Petski,

I received a kind email from Motion Dynamics Corporation.

The rep said:

They keep no inventory in stock, but make stuff as ordered.

Although he did say that he was sending me some samples.
He felt like they could meet my request  (.5 mm outside diameter).

He said I might be able to make something with a sample and then see if that works as far as ordering more.

I'll post back when I get the samples.

I'm really jazzed about  half a millimeter springs.  Hope they don't cast a fortune.  It takes 4 springs per loco.

If I ordered a quantity of 100, that would do 25 locos.  I'd keep some of them , but maybe some others would be open to buying 4 spring packs.

[peteski]

Thanks Petski,

I received a kind email from Motion Dynamics Corporation.

The rep said:

They keep no inventory in stock, but make stuff as ordered.

Although he did say that he was sending me some samples.
He felt like they could meet my request  (.5 mm outside diameter).

He said I might be able to make something with a sample and then see if that works as far as ordering more.

I'll post back when I get the samples.

I'm really jazzed about  half a millimeter springs.  Hope they don't cast a fortune.  It takes 4 springs per loco.

If I ordered a quantity of 100, that would do 25 locos.  I'd keep some of them , but maybe some others would be open to buying 4 spring packs.

Did you select the thickness of the steel wire they'll use? Or they will select that themselves?  If they use very thin wire then the spring will be very soft (similar to MT coupler springs).

[u18b]

Peteski,

I did not specify wire size.

I'll see what the sample are like.

[u18b]

Just posted a 2 minute video on the repaired 1983 NJ Custom Brass EP-2.

Traction is just a bear in these.  Still not as high as I would like, but at least it runs and pulls a little something.

If you didn't see how bad these are stock, here it is again (along with the new 2003 EP-2).

[Roger Holmes]

Ron--Thanks again for all of your efforts and meticulous documentation.

Was the unit that you repaired factory painted or somebody's custom work?  As you know mine is bare brass but I bought it used and don't recall if they were offered factory painted when they were first released.