Bachmann 2-8-4 Berkshire/Kanawha in stock at M.B. Klein

[jdcolombo]

John, remind me: do these have true see-through spokes or solid disk centers (like Bachmann 2-8-0)?

True see-through spokes.

John C.

[mmagliaro]

1. The drivers have see-through spokes.  They actually look pretty good (but not as good as the LL drivers)

2. John, I'm glad you mentioned the symptoms about going into full bind when backing a train.  Yes, even with the driver quartered now, I occasionally see this.  And of course it happens more under load because the wheel is less inclined to just "slide on buy" when it has pressure on it against the rail.  The quartering really has to be tight and accurate, and this is neither.   Like I said in an earlier post, you can get the quartering right (and by that, I mean that all 4 drivers match in their relative positioning of their crank holes on each side), but if the side rods are flippy floppy,
then it still won't work.  I can watch it do this.  Driver #3 turns... turns... turns... takes up all the egg-shaped slop in the crank hole, and NOW driver #4 turns.  And unfortunately, that little bit of error is enough to make the driver jam.

Victor, I very much enjoyed your discussion about the idler gear.  It makes perfect sense to me.   NOW I really see why the idler should always be above or below the line of the two gears riding against it.    Otherwise, the gears on either side press against each other and bind unless that center gear is dead true, on a dead straight bearing,
and is made perfectly concentric - all things that Bachmann is utterly incapable of making.

SOLID SIDE ROD:
Okay, I took the cheap way out. I layed the two rods over each over at the crankhole, aligned them over a scribed line, and soldered them together right at the crank hole.   I'm a little antsy that over time that soldered joint could break, but it's got a lot of soldered surface and the forces are shearing very flat on it, so I think it will hold.
All the same, if the idea works, I think I'll drill a few tiny #80 holes and put some pins through the two pieces.

With a solid rod on one side, the engine runs noticeably less lousy.  Notice, I did not say "good".  But it is definitely less lousy.

On to do the other side.

////////////////////////////////////////////////

Other idea:
It occurs to me that if driver #2 were pinned to the rods, and the idler gear were removed entirely,
that would remove the entire issue of the awful wobbles and binds being caused by that gear.  I would have to drill holes and put pins in, but I figure, heck, if it doesn't work, I can always just take out the pins and put it back the way it was.   A quick way to test this will be to remove the idler and just let #2 freewheel.

... which I will do...


... later tonight.

[VonRyan]

No idea if they installed them on this model but Bachmann-s 44-tonner does include an electronic circuit breaker wired into the motor circuit. It is a small yellow disk-shaped component which is supposedly there to protect the tiny motor from overloads.  I suspect that it is some sort of a thermistor which will get warm when too much current goes through it and will shut down the motor circuit until it cools down.  It is only a speculation (about how it works) as I never tripped it).

If it is what I think it is, it might be a capacitor to make them compliant with EU television things.

[peteski]

If it is what I think it is, it might be a capacitor to make them compliant with EU television things.

If you are taking about the 44-tonner then no, that is a circuit breaker. The RFI suppression components (chokes and capacitors) reside on the decoder board.  The breaker (which is a disc-sharped component which looks like as yellow capacitor) is wired in series with the motor.

[mmagliaro]

Checking in on Bachmann Berkshire progress...

Okay, after soldering the rods together so there is one solid siderod.

I think it definitely runs more smoothly.  Not great, but better.   Less binding, more uniform motion.  Starts up more consistently,
and can run at a lower voltage... I'd say about 4v now, instead of 5.

 I want to eliminate as much slop and variability in the mechanism as possible.  I want the wheels, rods, and parts
to move one way, and only one way, within a very narrow range of "wiggle".  That way, if something binds, it will
ALWAYS bind, and then I can see it and I can fix it.

To that end, I made the siderods one solid piece.
------------------

Next...
I took things apart, spread the frames open just enough to pluck that idler gear out from the bottom,
and put it all back together so the #2 driver now just freewheels in there.
MUCH better.
In fact, I'd say it runs "mediocre" now, instead of "lousy".

No doubt, that sloppy idler sandwiched between two driver gears was causing a lot of the loping and binding.
I have a notion now to drill some holes and try to pin it so I can make it go 'round on the rods.

Otherwise, I want to run it a while and see if it gets any better.  It has finally gotten to the point where it doesn't run
so awful that I didn't want to bother with any run time.

The idler... it's a bad bad thing.

[mmagliaro]

Well, as I feared, soldering the rods together does not hold.  Eventually, the stresses and flexing cause the solder joint to break apart.  So, I resoldered one to use as a model, traced it out on strip brass, and I'm making two new rods, all one piece.

That reminds me of another thing I don't like about this engine.  The rods are nickel plated brass.   Pushing drivers around on brass rods is probably a bad idea.  They are going to wear those crank holes. 

I really don't get how they think.  This is what I mean by "designing themselves into a corner."    Etch a single rod from stainless steel.  It's not THAT much more expensive.  It might not be any more expensive at all.   Get rid of the idler.  Drive 1, 2, 4 on the rods,
and gear-drive #3.    So now you have 1 rod and no idler.  Two fewer parts, lower cost, and a better mechanism.   

By the way, the wheel centers appear to be metal, so the trick of twisting the driver with tweezers between the spokes to correct the quartering is "probably" okay because the spokes won't shear out like plastic ones would.  As long as the driver isn't too tight and it moves easily, that should actually work.   Don't lean on it.  If it won't move easily, unscrew the crankpins, take out that driver wheel set, hold one driver and give the other side a gentle twist.  They actually move horrifyingly easy that way (which may be at the root of the quartering problems to begin with).

[victor miranda]

Hi Max


soldered side rods broke...
that seems.... wrong.

what is causing the flexing?

from clock making and repair
the thinking is for longest life of pivots(bearings)
one wants a hard and a soft. steel in brass
or steel in carborundum

so if the crank pins are steel, brass may be the correct material.
if the ll 2-8-8-2 of many years ago is any indicator, the thickness
of the brass may be more important.

the #2 driver does not have holes for a crankpin?

I am puzzled by the metal driver centers and the fit to the axles.
I know that flywheels are glued to shafts by b-mann,
you think they intended to locktight the axles ?

any signs of glue?

victor

[peteski]

If the drivers are all metal (tire and spokes) how are the wheels insulated electrically?

[mmagliaro]

Answers:

1. It looks like there is a non-metal bushing of some sort in the driver holes that the axles are pressed into.  I think that's
how the insulation is done.  You can see lots of plastic flash around the outsides of the axle holes at the centers of
the drivers from where they pressed the metal axles in from the inside.  At first, I thought the whole wheel center was just plastic.
But I started noticing that they just felt too heavy, and a little scratching with an Xacto showed shiny brass-colored metal under the paint on the spokes.

I don't see any glue, although there is some grayish looking stuff over the inside nubs of the drivers, so they may have used some 2-part epoxy.   It kind of looks like JB Weld, actually.

2. I soldered the rods by sanding off the plating until I saw clean brass.  Applied flux, tinned both surfaces.  Taped them
down on a board next to a scribed line so I knew I had them straight.  Apply iron to the overlapped rod joint,
while pressing down on it with a small screwdriver, the solder inside the sandwich between the two rods melts, the rods fall together.

It seemed like a really solid joint when I made it, and yet, after a while, both of them eventually broke apart.

I think the normal sliding back and forth of the drivers when it runs must flex that joint enough to eventually break it.  I could sand it all clean and resolder.  Maybe I didn't get them as strong as I thought.  But both? 

3. Driver #2 has a hole in it where the crankpin would go, but it is not drilled out to full size or tapped with any threads like
the holes on #1 and #4.

[Chris333]

For sale:  One DCC Bachmann Berkshire 2-8-4 Pere Marquette #1225 "sound equipped" Very little run time. Make offer. 

[victor miranda]

For sale:  One DCC Bachmann Berkshire 2-8-4 Pere Marquette #1225 "sound equipped" Very little run time. Make offer. 

I'll open the bidding at 75 and add shipping...

[victor miranda]

Hi Max,

I have faith your soldering is good.
what puzzled me was the fact it failed so quick
something is causing the flex to break it.

that same thing is also causing a hitch.

the crank throws are not the same,
out of quarter, and off center axle bearings.

all will flex the side rods.

hmmmm

a quick fitment check I use is to set the side rod on
the drivers at 3 or 9 o-clock,  All the holes should line up perfectly centered.

and on to other things.

that gray stuff is likely to be the glue to hold quartering.
I am betting the assembly is glued sparingly because they are
trying to avoid getting the glue into the bearings.

.... that is a fairly easy fix.

and the glue getting into the bearings may well be the hitching problem....

[mmagliaro]

Well, I don't see any glue on the bearings, and I've had the axles out of this thing.  All the bearings seem to float fine in
their slots (some might say, "flop around like a distressed fish", but I will use the nicer word, "float")

As an aside, I did find that the #4 bearings were the main source of the to-and-fro driver hunting that Chris333
mentioned.  There is just a little too much horizontal wiggle allowed in them.  Here's the interesting part.
I slipped a .002" brass strip down in between the rear side of each bearing, to lock it firmly in its slot.  The engine absolutely would not run.  The rods would lock hard.  No tweaking of the #4 quartering back one way or the other would alleviate this, either.
That means that the mechanism relies on that looseness and hunting to make it work.   Sigh.

I did a little more robust soldering job.   This time, I soldered not just between the two pieces, I also soldered around the rim of
the hole where the two rods lie on top of each other.  On the backside, this doesn't matter because it doesn't show.
On the front side, you can see a little solder if you look, but since this is the side rod with the main rod and the eccentric stacked on top of it at this hole, you really can't see it when it's on the engine.

Victor, I like your suggestion about making sure all the holes and drivers lie in a line.   Indeed, I can place this rod over the 4 holes  and they seem to line up dead-center with the holes.   However, the real test will be:
I am going to slip a washer under each crankscrew, so that when they are tightened down, they clamp the rods down against the wheels, then nothing can move.

Then, take the screws all out of the other side and see how THAT rod looks over its holes.  I bet I will see the alignment error.
Maybe I can fix it.

Chris,  I'll offer FIFTY quatloos  for the newcomer!

[peteski]

This is a very interesting experiment - but no photos!  Is there any way we could have some photos of the soldered siderods and other various related bits?  I know from persona experience that it is a pain to keep taking photos while experimenting but I thing it would really be worth it to have some photos in this instance.

[mmagliaro]

This is a very interesting experiment - but no photos!  Is there any way we could have some photos of the soldered siderods and other various related bits?  I know from persona experience that it is a pain to keep taking photos while experimenting but I thing it would really be worth it to have some photos in this instance.

Peteski, take heart.  I have been amassing photos of each step I've been doing.  I just haven't gotten around to posting them.   I hope to do it today or tonight.