USATC S-160 Consolidation

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Dick_Morris
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Re: USATC S-160 Consolidation

Post by Dick_Morris »

After a couple of previous attempts at using patterns made in 3D printed wax-like castable resin, I've made it through most of the learning curve of learning 3D modeling software, learning to use a 3D printer, and lost wax casting. I had a pretty good collection of lost wax equipment acquired many years ago from a friend moving out of state, but had never put it to use. Several more items were acquired or made before I was ready to efficiently create some castings. One of my better decisions was to cut a hole in the wall of the garage and install a second-hand high end range hood above the work bench. Burning out the flasks filled the garage with smoke and opening the door when it was below freezing wasn't a good option.

These are the results from a couple of weeks ago. The castings all came out looking very good and with one exception, all appeared to be unusable upon first inspection. The "almost successful" was because I got the compensation for shrinkage wrong. The prints were supposed to shrink by 3% and the bronze by 2%, so I compensated by printing the waxes at 105%. Upon careful measurement, all the castings were all 5.5% too large.

With the exception of the Laird crosshead, which was done using lost PLA, everything was done using a wax-like castable resin. In the first photo, going clockwise, the parts are CP_173 water tender valve rod flow controllers from the Disney drawings and coil spring seats, crosshead, offset cranks, a couple of types of valve linkage parts, and smoke box door hinges all for the S-160 Consolidation and modeled from the prototype prints. The thickness of the walls of the hinges was only 1/16 inch. The other photo shows the parts still on the trees after they were cast.

So, I'll chalk this up as partially a success and partially a learning experience and throw the parts with the most critical dimensions back into the pot to try again.
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Harold_V
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Re: USATC S-160 Consolidation

Post by Harold_V »

Nice work, Dick. Fairly large for investment, so I can only assume that you have a powered centrifuge, or are you vacuum casting?
How are you melting the metal?
So many questions! For good reason, though. I hope to get my investment casting equipment operational soon. I have much to learn!

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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Dick_Morris
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Re: USATC S-160 Consolidation

Post by Dick_Morris »

Vacuum. I melt with a Kerr Electromelt that I retrofitted with a digital PID controller. I have a propane foundry that will melt a lot more, but I restrict it to summer use. I've used it when there was snow on the ground but I'd rather not. Burn out is with a Kerr 6" x 6" x 6" oven and a kiln that is 6" x 6" x 8". Both have external ramp/soak PID controllers and go through a burn out cycle automatically. I'm not using perforated flasks and initially had trouble getting the mould to fully fill. After trying a couple of ways to get better flow of the vacuum in the moulds, I am now using vinyl rain gutter leaf guard mesh to line the flask from the bottom to about 3/4" from the top. It works well, is cheap, and is easy to put in the flask. It doesn't seem to give off fumes on burn out that are any more noxious than the PLA or castable resin and my new vent fan extracts the fumes pretty well.
FKreider
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Re: USATC S-160 Consolidation

Post by FKreider »

Awesome work Dick! I am jealous of your burnout oven, that is currently my biggest barrier to doing some investment casting myself. I keep thinking of picking up a pottery kiln which can be had for relatively short money off of craigslist and installing my own programmable PID controller. Maybe I will get around to it this coming year.
-Frank K.
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Harold_V
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Re: USATC S-160 Consolidation

Post by Harold_V »

Thanks, Dick. I trust when you say you have a propane foundry that you mean you have a propane furnace? A foundry is where castings are poured, while a furnace is what melts the metal. I've seen this several times, so the terminology is quite regularly misused.

I have a burnout oven, but it needs a modern control. I'd appreciate you commenting accordingly, keeping in mind I am not literate where such matters are concerned. I'd trust your recommendations in getting one for the oven. Right now, I don't have a sense of direction.

Many, many years ago I invested in both a vacuum caster and a powered centrifuge, a Romanoff. It will swing 4" flasks, about 7" long. It really helps in getting fine detail, something I learned in the many years I refined precious metals. All of my (jewelry) customers were engaged in investment casting, as you might suspect, with some of them willingly sharing what they knew with me. Trouble is, I've never done it myself, but I have witnessed a huge amount. I feel I have a lot to learn, so I welcome any guidance. I appreciate your comments in regards to the flasks, and how you are venting.

Interestingly, all of my customers just torch melted, even the one who ran a Romanoff, like I have. It would be more desirable to use a small furnace, which I'll keep in mind if I ever get that far. So much to do, and time is running out. :-)

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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Dick_Morris
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Re: USATC S-160 Consolidation

Post by Dick_Morris »

Frank - A simple kiln can be made relatively easily. Check VOG's Youtube channel for information on how he made his. He also has a calculator for wire size and length. I was getting tired of making tools before I could make parts so I watched Craig's List for Kilns for about a month. They show up regularly but most are pretty big. The one I finally got only had a 4" tall cavity and was missing the fire brick base, but for $75 it was a good start. I added a base and another course of blocks to take it to 8" high inside. Even with the increased volume it gets plenty hot for burn out. I'm attaching a photo of the kiln that I bought and modified. It might give you some ideas. The lid and top course with controller was what I bought. I added a firebrick base and on it is a perimeter row of fire bricks. The part I made is held together with a bit of furnace cement from a caulk tube, a piece of SS flashing, and a couple of universal length hose clamps. I don't claim any originality, I just copied the commercial design. The whole unit uses about 14 fire bricks. I got the parts from Amazon since it can be hard to find some things in Anchorage. The original controller isn't needed and is just set on the high and it is plugged into an external PID controller which does the actual controlling. The plug in the front was to look into it but I used that hole for the thermocouple. I added a couple of frames and some tie rods so the bottom and top will move as a unit, but they aren't really necessary. I still need to add a couple of tie rods. One thing I want to add is some sort of handle for the lid. The Kerr oven I have that is about the same size has a front opening, and I think I prefer the top opening.

Howard - Yes, foundry furnace. The error I keep seeing is people calling a foundry furnace a forge or smelter.

I opted to use an external controller so I didn't have to modify the kiln or Kerr oven. I just plug the controller into the wall and plug the kiln into the controller. I bought one from a place in Canada that advertises on Ebay for about $225. It works fine but the programming instructions are a challenge. Since I needed a second one I decided to make my own and I like mine better.

The type of PID you need for a burnout oven is a ramp/soak controller. It can be programmed with a burnout cycle. You will also need a solid state relay, maybe an off-on switch, a project box, and a type K thermocouple. I think I have about $140 invested in the one pictured that I put together, but if I were going to do it again I would simplify it a bit and probably save about $20. The thermocouples I got have a type K thermocouple plug so I can plug them into the controller so It's easier to move things around. Make sure the insulation on the thermocouple wire will handle the temperature. The PIDs and SSRs will operate on either 110v or 220v. (But don't get a 24v PID.) The assembly involves relatively simple wiring and is was actually easier to build the controller than sort out the programming, which isn't very intuitive. Some brands of PIDs have better instructions than others. I got the cute little box (about $15), thermocouple and thermocouple socket from Amazon and I think the PID and 40 amp SSR on Ebay for about $100.

Concerning flasks, About 10 years ago my son came brought me several pieces of 3" diameter SS tubing in about 30" lengths. I didn't know what I would use them for, but when I started the casting project I dug one out and cut it up to provide various lengths of 3" flasks, including some that are longer than what is commercially available. Never throw anything away!
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FKreider
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Re: USATC S-160 Consolidation

Post by FKreider »

Thanks for the info Dick!
-Frank K.
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Re: USATC S-160 Consolidation

Post by Asteamhead »

Hello Dick,
That's a pleasure, watching your results and your way of making 8) ! Like your work!
Knowing well it's a long hard way from a raw construction towards a perfect casting :!: . Thus I never dared to make castings by myself rather than relied on skilled friends and several small companies who were willing - and were able - to do such work. :). Making patterns of different methods however is another story (and fun).

Best regards
Asteamhead
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Dick_Morris
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Re: USATC S-160 Consolidation

Post by Dick_Morris »

Lately I've been working on the hangers, equalizers, pins, clips, etc., for the suspension and I've made some good progress on springs. The driver suspension is made up of eight leaf springs of two lengths and two coil springs. The springs in the photos have 17 leaves, the other four will have 19. I've always been bothered that some commercial designs use springs that are overly thick and not to scale. Since I have prototype drawings and a locomotive to look at I decided to try and follow the prototype as close as I could. These aren't exact scale in thickness and width, but they are pretty close. When they are black, covered in oil, and under the locomotive no one will ever know they aren't exact scale.

Just scaling springs directly won't give a usable spring. I ran the numbers using an English ME booklet on springs and found a scale spring would be about twice as stiff as needed. A suggestion in the book was to use Tufnol (phonelic) sheet for some of the spring leaves to decrease the overall stiffness. I decided make half of the leaves from black Delrin sheet, alternating with the steel leaves. Both Delrin and 1/2" wide spring stock were available in .043" thick which is pretty close to the scale thickness of the prototype.

After cutting the Delrin close to the right width on a band saw and then using the mill to bring it to the finished width, I cut the spring stock and Delrin close to the proper length with the cutest shear I've ever seen. Leaves were then drilled in the center with a 3/32" carbide spade drill. A jig was used to locate from the center hole so I could accurately trim each end of each leaf to length with a 1/4" carbide end mill. The spade drill was used to drill starter holes and was followed by a 1/8" carbide end mill to make the slots at the end of the top leaves. After they were cut to length the arc of the leaves was increased and made consistent using a pair of simple dies in an arbor press as shown in the attached photo.

One stack of leaves was then temporarily assembled on a #3 bolt and the center of the stack was compressed in a vice so I could measure the thickness for the opening in the strap that would clamp them together.

I had three tries at the best way to make the strap. First I made a simple pair of dies and bent a piece of .062 stock. That didn't give sharp enough corners and the material galled against the die. Next I cut a 1/2" slot in a length of material and tried to TIG weld a cap on it. That probably would have worked if my TIG skills were up to it. I got a nice TIG welder for Christmas, but so far I only have a total of about 10 hours of experience using the TIG process. The successful method was to use the slotted material, cut a step into it so the opening height would be exact, and silver solder a cap onto it. The straps were made so that they are about .005" wider than the spring leaves and the vertical opening is about .005" larger than the stack of spring leaves when they are tightly compressed together. One problem with the silver solder was that it left a fillet in the corner of the opening that I had to remove before for all the leaves would fit into the strap.

To assemble each spring I slid the leaves into place, one at a time, and held them with a pin through holes in the strap and the leaves. When all but the last leaf was in place, I clamped the pieces together and used a drill press vice to push the final leaf into place, pressing against the next longer leaf in the stack. When all the leaves were assembled, the temporary pin aligning them was removed and replace with another which was riveted over in countersunk holes in the strap. The pin on the first spring was steel, on the second it was brass with the ends annealed. I'm not totally happy with either because the peened over material didn't fully fill the countersunk holes. For the next spring I'll make a countersunk rivet and peen over just one end in a fairly shallow countersunk hole.

When all the springs are done, they will have gun blue applied.

With the use of the shear and carbide tooling machining the hardened spring steel was no problem.

I've tested the springs and all support between 75 and 80 pounds when straight, which is their operating level on the prototype locomotive. I'm guessing my locomotive will weigh around 700 pounds so this should be pretty close to what I need. If the springs aren't right I can adjust them by disassembling them and replacing one of the leaves with either Delrin or steel.
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NP317
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Re: USATC S-160 Consolidation

Post by NP317 »

Nice work.
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Dick_Morris
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Re: USATC S-160 Consolidation

Post by Dick_Morris »

Some thoughts and things I’ve learned about the capabilities of 3d printers to print precision mechanical parts.

The photos are of a couple of generations of test prints (frame brackets for my S-160). The dark grey part was printed on an Elegoo Mars DLP (resin) printer, modified with a dual linear rail Z-axis and with the Z-axis modified to decrease play. The print settings for the X and Y axis have been calibrated for Elegoo standard grey resin. The light grey part was printed in generic PLA using an unmodified Flashforge Adventure FDM (filament) printer.

The final versions will be printed in either PLA or castable resin and investment cast in bronze. I created the 3d models with Freecad. My parts are typically one or two off - in this case they will be left and right side mirror images of each other. I’ve learned that doing test prints allows me to test/mock up and check the fit and the accuracy of my 3d model without wasting expensive castable resin or spending the additional time required to commit the parts to bronze until I know they are right. After they are cast in bronze I will do light machining of the critical surfaces.

Here is a comparison of selected nominal and measured dimensions and the percentage the actual dimensions compared to nominal dimensions. The prints to be printed to be investment cast will be printed 2% oversize to compensate for shrinkage of the bronze when it is cast.

Axis---Nominal------Mars------------------- FFA3
Z------.906”----------.900”/99.3%---------.895”/98.7%
X------1.813”--------1.814”/100.1%------1.821”/100.4%
Y-------1.281”--------1.275”/100.5%------1.292”/100.9%

These machines are remarkable!
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FKreider
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Re: USATC S-160 Consolidation

Post by FKreider »

I have an FDM printer (CR-10) and have done a bunch of prototyping for castings along with a handful of actual sand patterns, it has been worth every penny!

I am seriously considering picking up an Elegoo Mars since its so affordable and highly recommended. My purpose would be the same as yours- for one off investment castings using castable resin.
-Frank K.
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