New brass Milwaukee Bipolar EP-2 clinic- part 2

[u18b]

Now, when I see this photo.....



I look at that wasted empty space under the motor.

It is begging me to fill it with weight.

So I decided to make a cast metal weight to fit in that spot.

Here is the hand crafted master.  Since my shim was made out of .060" perfboard, I just used that.




Had to make on end round to fit the contour of the flywheel.




It is designed to be a drop fit.  There are cutouts for the truck retaining screw which must swivel, the height adjusting screw and the pick-up wire.





Notice I made small cutouts for around where the motor tabs are.

[peteski]

Ron, is it really worth the hassle to add such tiny bit of custom-cast lead weight when there is probably lots of space over the motor/gear-tower to install a larger slab of lead there?  All this mastering the part, making molds and pouring melted metal?

Then if you really want to add some weight in that space, why not just get some 0.040" (1mm) lead flashing at Home depot and then simply cut a rectangle with the hole in it?  No need for the little wings. They probably add less than 1g each.

Or add some rectangles of that lead sheet behind the gear tower and in front of the motor.  Much less work.

[u18b]

Pete, you are correct in that it may not be worth it/matter.

However it might.

Here's why. 

When it comes to TOTAL weight, this will be pretty minor.   
That's not what I'm after at all.

It has more to do with Balance point.

When you look at an EP-2 mechanism..... like this shot.




Where can you add weight?

Well, Kumata already includes in these kits a lead weight that fills the cab.

Here is the weight.   The tall part sits in the cab and the long part sits on top of the gearbox and just a little over the flywheel.



And of course the boiler room sits BEHIND the cab.  There is a TON of room to add weight in the boiler room.   The problem is.... you can place so much weight in the boiler room, that the nose of the loco begins to lift.

So the important need to to try to find spots to add weight forward of the gearbox.

The largest area in the nose of the loco on the other side of the motor brace -- that is where the decoder goes.

And there is not much room in the roof area.

So the space that is available is the area under the motor.

So if I can add several grams of weight over the front trucks under the motor,  then that allows me to add some more weight in the boiler room.

So it is not about total weight per se, it is about balance point.  Much like the issues steam people have with getting as much weight as possible over certain drivers.

Since I have not cast any weights yet, I don't know how much difference it will make.

But I do know one thing-  it can't hurt.   

[davefoxx]

Ron,

Balance: makes perfect sense.  Keep up the good work.

DFF

[peteski]

It has more to do with Balance point.

Since I have not cast any weights yet, I don't know how much difference it will make.

But I do know one thing-  it can't hurt.   

I had a strong feeling that you were going to say that.  However, to me, this is still a bit of an overkill.  The entire loco body/shell/most mechanism is brass (which is a pretty heave metal by itself).  Going through all the gyrations to add few grams under the motor IMO will not really be worth the effort or affect the balance all that much.   But I wouldn't mind being proven wrong.

I guess to me this is one of those points of diminishing returns I would not spend the time or effort on (when I have so many other projects waiting to be worked on).  But we are all individuals with our own opinions and views. 

[u18b]

You may be right. 

But it wasn't all that much trouble.
The master only took me about an hour to make.

Mold making took about 45 min. 

Casting should be easy. 

So it wasn't that big a deal. 

[victor miranda]

uh, peteski?

have you noticed how far U18b goes in his attention to detail?
if he thinks it should be done, he does it.

please stop asking him why he does what he does.
ask him how he did it...

Hi U18b,

I am of the opinion that there is no such thing as an n-scale loco that weighs too much.
They can be badly balanced.... and that means the challenge is to add counter weight.

victor

[peteski]

uh, peteski?

have you noticed how far U18b goes in his attention to detail?
if he thinks it should be done, he does it.

please stop asking him why he does what he does.
ask him how he did it...

Really Victor? Stop asking "why"?

Ron posts his project write-ups in a public forum and I didn't think that questions or critiques were out-of-line (especially in this forum).  Why do I ask ask? Because I'm curious. That is how I learn.  Maybe my manners or posting style is not the most delicate, but I guess I call um as I see um.  Ron answered my questions and critiques and I am grateful to him for that.

[u18b]

Time to make a mold so I can cast some weights.

This will be old hat to many/most of you.  But some of you have never tried mold making and hopefully this will help you.


I want to be able to copy the weights for the cabs so that I can have extras as well as the new weights I made.

Here is the weight for the cab.  It is easy to make a mold of because it is FLAT on one side with no big undercuts.  It did have one hole that I will fill in with body putty.  When the castings are made, I can re-drill it out.



I use flat styrene TILE sheet for the mold box since you can break it in lines easily. 
I then glue the weight to the styrene sheet (flat side of course).

Now since this is for pouring metal (a bit different from resin castings), I added the extra styrene on the right.  And actually, that side will be the top.

The big triangle is the pouring hole.  The thin long piece is an air hole to allow air to escape.



Here is the mold (more in a minute).



It is oriented this way.   I'll be making another mold to be the second part.  You will see when we get to casting.

Now, since I already made this master of the cab weight and a mold, I decided not to re-invent the wheel and just use it over again.  So I broke the cab weight free and cleaned it up.




I then mounted my new master.



To be better organized, I scratched what this was for – backwards-- into the mold box base.




I then build up the walls for holding the RTV rubber.  These walls are a bit thicker than normally needed for resin casting since...
1.  the mold will stand up on its side instead of lying on its back.
2.  the liquid will be hot.
3.  since I will be holding 2 pieces together, I need it to be sturdy and deform.



In the next installment, we will look at making a mold.

[u18b]

Went to one of the art supply stores (Hobby Lobby or Michael's- forgot which)

Bought some RTV moldmaking silicone rubber.   This one was 10 to one by weight mixing.  It was made by alumilite.

The very first step is knowing my volume of my master with mold box.

So I go to the kitchen and fill the mold box with water.  I then carefully pour that into a mixing cup.

Now RTV does not last forever, so you should use it for a couple of projects if possible.
So I have another mold project ready to go.  I'm one day making castings for GE axle sideframes. 

So I add water to that and add it to the mixing cup.

I use a Sharpie to mark the line.



I then used compressed air to blow all the water out of the mold.  To dry it out.

I then use a postal scale.
Turn on, set to grams, and then zero it (tare) on with the cup on top.



So the weight at this moment is zero.   I now want to add the main white RTV to the dried out cup and fill it to the line I made.



When I fill to the line, I'm at 61 grams.




I then add 10% of the catalyst.

About 6 grams.  You can see I'm short 1 gram, but it is no big deal.



I then carefully stir the two parts together.   I try not to be too vigorousness.

You have to mix it thoroughly until the color is even.
But mixing adds airbubbles- bad.



I have a full 30 minutes before it sets up, so I let it sit for a while.
Air bubbles rise.

After about 7 minutes, I'm ready.



Here is a casting trick I learned from a friend.

Air bubbles rise.
Air bubbles are IN and moving UP to the top.

........uh...... why not pour from the bottom.
There are few bubbles there.

So I cut a hole in the bottom.




.... and let it drizzle out.




Notice how it is filling the hole in my weight.   You raise the RTV high on a side and let run/creep into the crevices.




And I have my other mold box right handy.


EP-2 master is covered.  The sideframes are getting there/




When everything is covered, I can open a second hole so it will drain faster.




And then I fill the boxes up to the top.



I then place a lid on top for a nice smooth surface later.




NOW comes the hard part..... leaving it alone for 8 or more hours.

[TiVoPrince]

Nice
to see implementation of best practices in contrast to the 'we hope that nobody will ever know about the shortcut taken' approach.

Wonder if we would ever have heard of Takata had they followed best practices rather than the minimum that the law allows...

[u18b]

Thanks TiVo.

Been out of town on a business trip.  Ready to get back to work.

Molds came out great.
I gently peeled them loose.






And while I was away, my mega supply of casting metal came in.

Bought a 1 pound ingot.  More on that when I get back to posting.

[u18b]

As we are moving toward pouring metal castings for various weights.....

Let's talk alloys and toxicity.

I am no expert by any means, but I have done a good bit of reading and prep for modeling.

First Lead.

Lead is a great substance because it is dense and soft.
But there are two problems with it.
1.  It is toxic.   If you ever melt it, do it outside.  Also, always wash your hands when working with it in modeling.

2.  It has a very high melting point.  It is a whopping 621 degrees F.   That by itself makes it a bit more difficult and dangerous to work with.

But people discovered that if you combine metals in various ways, you get alloys with very different properties.

The properties that I care about are: melting point, density and hardness, toxicity.

Here is a GREAT website for learning and studying alloys.
CS Alloys manufactures this stuff.  I have never bought from them but they have a WONDERFUL chart of organized information.

Go to their website:   http://www.csalloys.com/

Over on the right side you will see a chart.
Just under the chart you will see a link that says:
Click Here to See Full Specification Table

Click on that (scripts must be enabled since a pop-up window opens).

THAT chart has a bunch of info.

The things I look at are:

NAME- left edge
MELTING POINT  - middle left
BRINELL HARDNESS - middle right
COMPOSITION - right edge

Now remember, water boils at 212 F.   So that is a good reference point.

Hardness.   If you are a math and physics guy, read this:  http://en.wikipedia.org/wiki/Brinell_scale

I don't care why.  I just need reference markers.   
LEAD has a rating of 5.0 and of course is fairly soft.
BRASS is about 60 (and is pretty hard).

So bottom line.....  when I go to the CS Alloys chart, I see a low of 9 and a high of 22.
For my purposes (like a gearbox) 9 is pretty soft.


Next TOXICITY- 
Bismuth- low.
Tin- low
Indium- fairly low
Lead- fairly high
Cadmium- bad news   

So for modeling, when I look at that chart, I want to stay away from Cadmium.

Now I have 2 weights.   One is big and is over the gearbox and sits in the cab.
That weight is not a big deal.
For that one, I'm going to use Lo-136.
When searching to buy some, just search ALLOY 136.

I'm not certain, but I'm pretty sure this is the stuff Walthers used to sell years ago as "Temp-Lo".  It melts in boiling water and is moderately hard.

But the other weight is a bit different.   That smaller weight is right up next to the motor and will get pretty warm.  I don't want a 136 alloy melting in my loco!

For that one, I'm going all the way down to TRU-ALLOY 281.   Hopefully that is high enough to withstand the heat of the motor (300 degrees is cooking temp.  If my loco gets 300, it would seriously burn my hand).

Also, it has low toxicity.  And at Brinell 22, it is pretty hard.  The density is not a whole lot different from all the others.

So those are my choices.   I have bought both.

I have cast with good results already with Lo- 136.   I made a gearbox for another Kumata loco (Trainmaster).


I have not cast with  Tru- 281.

So I will be reporting my experience in the future.

[u18b]

Had a little extra time this evening.  So I enjoyed trying casting metal.

As described above, I used the Tru-281 alloy.
I had a 1 pound bar that was rather unwieldy.
So I melted it in little bit larger pan (just for casting, not eating      ).



Once melted, I transfered the molten liquid to a smaller pan that gave me more depth for spooning out.

I had my mold ready.
Two halves held together be spring loaded tweezers.



I scooped out some liquid.....




....and poured it into the big opening of the mold.
(hard to photo and pour at the same time      )




The first pour looked pretty good.



Once cooled, brought it to my desk.


It actually turned out pretty good.   Except for that BeeBee.



Haha.  It was from one of those bubbles.  Next time I'll make a better lid.




Pulled the casting out of the mold.  Looks pretty good.
The excess was trimmed with Xuron cutters and the waste dropped back into the pan to melt.



Not much clean-up required.



But all was not rosy.  I guess I got lucky on the first try.   When I did more, I had problems.
Suddenly liquid metal ran out the bottom since the mold halves were not tight up against each other.

In the end, I found that just holding them together with an oven mitt to protect my fingers was sufficient and worked well.



I made several castings while the metal was molten.
I made gearboxes for one complete loco,
2 cab weights (enough for my old NJ Custom Brass EP-2)
and 4 under motor weights.

They all turned out well.



Now, this alloy is about 25 % less dense than lead.
The original lead cab weight weighs about 11 grams.
My new weight weighs about 8 grams.--- still a benefit and better than none.  (I look forward to being able to make these for years to come.).

In the case of the little thin weight under the motor, Pete was right that it did not add much weight.

The alloy castings came in at about 1.5 grams.

But all of that weight goes directly over the front truck.
So while it was indeed a very minor improvement, I think it was worth it... if for no other reason than I've begun to explore a new area of modeling.

[peteski]

In the case of the little thin weight under the motor, Pete was right that it did not add much weight.

 

Nevertheless, I thoroughly enjoyed your excellent writeup and photography in this tutorial.  Well done Ron!