Kato Mikado weight info and ideas

[peteski]

Max,  I did a quick Google search and here is one example: http://eagerplastics.com/rtv325.htm

As far as water in plaster or cement mold goes, it can take many days for it to completely dry at room temperature (even thought it looks dry).  You could speed up the process by baking the mold in at a temperature below 212 degrees F.  It will still take some time for the water to evaporate.

If you don't want to bother with RTV rubber, try Plaster of Paris or Hydrocal.  Both will produce fairly smooth mold cavities (when completely dry). 

[mmagliaro]

Max,  I did a quick Google search and here is one example: http://eagerplastics.com/rtv325.htm

As far as water in plaster or cement mold goes, it can take many days for it to completely dry at room temperature (even thought it looks dry).  You could speed up the process by baking the mold in at a temperature below 212 degrees F.  It will still take some time for the water to evaporate.

If you don't want to bother with RTV rubber, try Plaster of Paris or Hydrocal.  Both will produce fairly smooth mold cavities (when completely dry). 

I was wondering about this because you mentioned it before.  Can plaster stand up to the temperature of molten lead?

I have a plaster mold hardening right now.  I baked it in the oven at low temp for about an hour, took it out,
and it seemed bone dry.  But sure enough, I waited another hour, and I can feel that the top surface is
just not "dry" dry.  It's got that slightly cool feel.  So I'll give it a couple of days and try it.

[SkipGear]

This seems like an awfull lot of work when you can form lead so easy. Melting lead (or any other material for that matter) gives off some pretty nasty fumes. I haven't had a situation yet where I couldn't cut, file, or hammer a piece of lead into shape to do what I want and have it fit as well as a molded piece. .....





Those little pieces of lead added 10g to the Walthers 0-8-0 and they all fit exactly where they needed to go with no voids. I realize this is a different type of application and there is a desire for repeatability in this case but with the work and effort so far, I could have had a half dozzen or so pieces built already.

[peteski]

Skipgear, anything you do repeatedly and often enough will eventually kill you. Melting lead, photoetching, painting, eatign junk food, etc... 

Max, plaster or Hudrocal can easily withstand 600 degrees F.  Investment (a type of plaster) can easily withstand temperatures of molten brass (much higher than lead) used for those fine investment castings we use in our hobby.

[Lemosteam]

But I can cast and sell hundreds!! MUwahahahah....    The eight castings I made add lots of weight to my Minitrix K4's...

[mmagliaro]

Ha!... I doubt I could sell 3, of course.  That's not the point.  I want to see how to do this.
(Although, if those traction tire drivers disappear again, a simple drop-in weight that makes a tire-less
Mikado a good puller might be an attractive item indeed).

Tony, it's taking a lot of time *this* time because I don't know quite how to do it.
Once I figure that out, hopefully, it will be a simple matter of mixing something up, plunking in the weight,
waiting until the next day, and then pouring some lead in it.
I have always done what you did (and what everybody does), fit pieces, sheets, cubes, whatever, and
make them fit however you have to.  I want to see if a cast weight can do that more easily, and perhaps,
if I drop cubes of tungsten into the mold and pour around them, more heavily.

[mmagliaro]

Well, it's time to close the book on this as a failed experiment.

I did succeed in casting two weights in my plaster mold.  Worked great and the weight popped right out of the plaster
with no hassle at all.

But...
The pure lead weight, which needed some filing to get it to actually fit properly in a stock Mikado, only weighs 14g.
Since the two Kato stock weights I have weight 10g and 12g, respectively, a 2-4g increase is clearly not worth the hassle.

In the second one, I placed all the tungsten cubes and disks I could into the mold and then pour molten lead around it.
The idea worked, but still no go on the weight.   I have filed it down to 20g, and it still doesn't fit.  I could beat that with
a few tungsten plates and cubes stuffed here and there.

So, as many of you suspected, it's not worth it.  Making and shaping lead, molding putty, or fitting in tungsten wherever you can
is easier and yields better results than this.   I suppose if one could actually cast an exact replica of the Kato weight in
pure tungsten, we'd get a serious increase.  But that's a little beyond my capabilities.

Thank you for all your commentary and suggestions.  If nothing else, I learned how to make a lead mold in plaster!

[Chris333]

I think tungsten has one of the highest melting points of just about anything.

Odd you first try with sheet lead got 20g, but a perfectly molded piece of lead was only 14g?

[Mark W]

I think tungsten has one of the highest melting points of just about anything.

Odd you first try with sheet lead got 20g, but a perfectly molded piece of lead was only 14g?

The second highest melting point of any known element to be exact.  Only Carbon beats it with a higher melting point.

Was it the same sheet lead melted into the casting, or perhaps a less pure hybrid for casting? 

What if you take the putty and squish it into the mold along with the tungsten cubes.  What weight can you get with that?

[Chris333]

Yeah Max if you have any I would want to know what the putty weighs in the same mold. 

[Kentuckian]

Very interesting thread.  I learned a lot.  The law of diminishing returns is illustrated again.  It was  relatively easy to double the weight, but small increments in weight after that were very expensive in effort or money.  Thanks for sharing.

[mmagliaro]

Well, remember, I didn't get 20g just with sheet lead.  I got it with a few tungsten plates and some sheet lead.

Filling the mold with tungsten putty is a good idea.  I thought about it (I don't have any, but I could get some).
But seeing as how tungsten putty weighs about the same as lead, and my casting of pure lead weighs 14g, I don't see how we could expect much different from the putty.

[SkipGear]

I wonder if the difference is in the fact that it was an open pour vs. a spin or pressure cast? A gravity pour could be more porus and less dense than a pressure cast.

[mmagliaro]

I wonder if the difference is in the fact that it was an open pour vs. a spin or pressure cast? A gravity pour could be more porus and less dense than a pressure cast.

Tony, so in other words, the tungsten plates and lead weights I piece together were pressure cast, so they are less porous than
when I pour hot lead into my mold?  So cubic inch for cubic inch, the "fishing weights" are more dense than what I can pour?
Interesting.   I don't really know how to find out, except to make a mold as close to exactly the same size as a pure lead weight
and then try pouring my own, but I think I've had enough of this.

Another thing I discovered is that it's pretty hopeless getting a Mikado to pull well with weight alone.  I stacked 45g of weight on top of it, and it still cannot pull a 20 car train up a 1.7% grade without a traction tire.  45g is a darn lot of weight.  The GHQ W-3 boiler
(without the cab or smokebox face) weighs only 26g.  (That pewter is not very dense, only about 7.6gm/cm^3)
In fact, with that 45g on there, the engine total weight is about 130g, which is actually 5g more than a Kato F unit (and the
F can easily pull those 20 cars).

It's all about those swiveling diesel trucks.  They are much more sure-footed and adaptable to the track than a rigid 2-8-2.
Getting all the wheels solidly on that rail makes for lots of friction.  The Mikado is probably only really "biting"
on 3 or 4 wheels, not 8.

Anyway... traction tire it will be.  It's been a fun ride.

[victor miranda]

try a layer of tape over the #4 driver bearing.

.... or file at the bearing pocket of the # 3 driver.