Ball Hopper Monitor Patterns/Castings Attempt

[Casting Iron]

A trial run on printing multiple patterns at the same time.
These are not usable patterns, but the print did prove the concept is viable.
The multi-color is using up some old filament.
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[Casting Iron]

Work continues on the Baker BHM design.

I have a photo of a 7hp engine on a base, but I don't see a base on a 4hp engine, which is what I am modeling.

I came up with my own base design, which is just a freelanced affair.

And I got the two flywheel 3D models complete.

There are lots of little bits and pieces on an IC engine.
This is my first IC engine, and so I am discovering these facts.

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[Casting Iron]

Here is an update on the various 3D printed pattern work.

The story on these 3D patterns is that you can get a close approximation to a pattern with 3D printing, but there is always a bit of touchup work to be done to the 3D prints.

Layers/Layer Heights:

One issue with 3D prints are the lines that occur between layers.
The layer height can be adjusted a bit, but generally speaking, if the layer height is reduced, then print time seems to go up exponentially.
I have decided to just use standard layer heights that come with the Prusa XL printer.

Sometimes a 3D model cannot be created exactly like a final pattern, due to the limitations of the 3D program.
When this happens, I get as close as possible to the real part in the 3D model, and then touch up a bit with fillers, and perhaps a bit of dremel touch-up here and there.
I really like to minimize the post-printing work as much as possible, but it is inevitable that there will be a bit of touch-up.

Line Smoothing Techniques:

I have tried various line-smoothing techniques, to smooth 3D printed patterns, and some work ok, and some have not worked out.
I am not going to use any chemical means to melt the PLA surface.
I don't want the chemical exposure.

One method that has worked somewhat well is using a fine sanding sponge in a variable speed angle drill.
I tried sanding disks, and they just burn the PLA surface.
I tried 2" sanding sponges in a tool and die grinder, and these also melted the PLA, and created black streaks in the surface.

I tried the same 2" sanding sponge in the variable speed angle drill, and ran the disk slowly, with a good bit of pressure, and the sponge sort of melts the tops of the ridges off, and repositions the excess material into the valley.
There is not much if any dust or particles created during this proces, since it is a low speed melting/smearing process.
The low speed prevents the large scale melting and black streaks on the surface of the PLA.

I use the fingernail-scratch method to determine how effective the sanding sponge is at smoothing the surface.
Before applying the sponge, there is a very audible and tactile feedback when you scratch your fingernaile over the 3D print lines.
After buffing with the sanding sponge, there is almost no audible or tactile feedback; it is more like scratching the surface of glass.

Sprayed-On Filling Compound:

Another technique I tried was to spray sheetrock wallpatch compound onto the surface of the print.
This method actually worked fairly well with a pressurized slurry container.
The problem with this method is that when I applied a shellac overcoat, it basically dissolved the wallpatch compound.

So the method I have settled on using is the 2" slow speed sanding sponge, followed by enough coats of shellac to fill any remaining low spots.

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[Casting Iron]

The 3D printed patterns and coreboxes that I have created to date use a variety of methods.

I can apply a thicker coat of sheetrock wallpatch compound (called Fastpatch, not the same as the material I sprayed on), and this seems to withstand the shellac, but a thicker coat requires a lot more sanding and finishing work.

I have grunted through the filling for the pattern halves for the water hopper, the water hopper core boxes, and the fuel tank pattern halves.

Permenant Pattern Halves and Coreboxes:

The intent is to create permanent pattern halves for this engine in alloy 356 aluminum, since I would like to make multiple sets of castings, or at least have the capability of sending out permanent durable patterns to a foundry for reproduction.

I generally don't like to make separate coreboxes when I can use the pattern halves as both patterns and coreboxes.
I tried to combine the patterns and coreboxes for the water hopper, but that got too tedious, so I have water hopper pattern halves and corebox halves.

For the fuel tank I am going to use these patterns as a corebox, as well as using them for patterns.

Some folks go to a lot of work making coreboxes that are unnecessary, so I am trying to make these patterns using the "smarter-not-harder" method.

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[Casting Iron]

Here is where the fuel tank pattern halves/coreboxes have progressed to this point.
These patterns will required a bit more sanding, and another coat or two of shellac, and then they will be ready for use with making the pattern half molds.

The sand for the molds and cores will be resin-bound commercial foundry sand, which is very fine and dry sand with round grains.
I don't know how they get the round grains, but they are indeed round, and very uniform in size.

These are photos of some molds I made for the green twin engine, and this material produces a very accurate castings, since you do not rap the pattern to get it out of the sand, but rather use a small automotive body work slide hammer to give a sharp slight impact on the pattern in the direction of pattern pull, which sheers it out of the mold cleanly and precisely.

I also discovered a spray-on ceramic mold coat, and this does a superb job of stopping burn-in, and gives a smooth shiny finish to iron castings, right out of the mold.

Using resin-bound sand, and various molding techniques, one can approach what is called a "near-net" casting, which is a casting that is almost at the final machined size, and only requires a light skim of the machined surfaces.
Many commerical foundries are now producing "net" castings, ie: the castings don't require any machining, due to their extreme accuracy.
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[Casting Iron]

Here are the fuel tank 3D printed pattern halves, almost ready to be used to make permanent pattern halves.

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[Casting Iron]

Here are the water hopper 3D pattern and corebox prints.
I have a bit more smoothing on these to do.

The pattern halves have coreprints on the top and bottom.

The corebox creates coreprints on the top and bottom of the core.

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[Casting Iron]

This was the trial run 3D print pattern half for the flywheel, mainly to test bed lifting on the Prusa XL.
This flywheel is 14" diameter, and the bed adhesion was excellent, with complete adhesion across the entire print, in a drafty room with cold air conditioning blowing across the print.

The spokes for this flywheel were created flat, and then a radius added to the edges.
Although these spokes look ok, I wanted true ellipsoidal spokes, and so I recreated the entire flywheel to achieve that.

I like the looks of the revised flywheel a lot better, and will be 3D printing pattern halves for it soon.

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[Casting Iron]

Last night I modeled the engine base, and the night before that the inner and outer flywheels.

Detailing the small parts is rather tedious, but there is no other way but to keep at it, one tedious part at a time.
We all know the phrase "No pain, no gain".

I may work on valves tonight.
I remembered that I 3D modeled a set of valves and springs for a Galloway, so I have gone back and reviewed what I did there (Galloway items shown below).

The Galloway valves are not the same size, but I think the 4hp Ball Hopper Monitor valves are approximately the same size.

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[Casting Iron]

I ran across this video while trying to avoid doing 3D modeling for this engine.

This was a motion study to verify that there were no conflicts.
Luckily, if there is not a perfect fit of all mating surfaces in Solidworks, the simulation will not run.
I add one piece at a time to the assembly, and test each piece for motion before adding the next piece.
Very handy feature of SW to make sure the engine is going to run.

I think I will work on the governor weight next, since it is a very strange object, and so is going to be tricky perhaps.
Sort of a wishbone affair, with a bob weight on one end.
This is one of those odd pieces where it is not really clear exactly where to start, since most of it is curved.

In some of the 4hp BHM photos, the free end of the weight is constrained in a C-shaped boss on the side of one of the flywheel spokes.
I am using this design as opposed to the stop located on the outside of the weight, which can be seen on some 4hp BHM's.
It appears that only the top of the swinging end of the weight makes contact with the trip arm.
Nothing else touches except I guess the finger on the end that is constrained in the C-shape.

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[Admiral_dk]

You really have been busy 

Any of the shown 'Castings' that will be committed to Metal ?

Per       

[Casting Iron]

The next step for me it to cast permanent pattern halves in 356 aluminum.
I have not quite gotten ready to do that, but am getting close for the fuel tank pattern halves, water hopper pattern halves, and water hopper coreboxes.

The weather is good right now, so this would be a good time to cast those items.

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[Casting Iron]

I got the governor counterweight done.
That was as ill-mannered a piece as I have ever tried to model.
So many odd shapes in that piece.
I will have to touch it up a bit after 3D printing it, but I think it will work.
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[Casting Iron]

I am studying phtoos of the rocker arm tonight.
This is a relatively small part, and located behind the flywheel and larger timing gear.
Rather challenging to get a good look at it.

This video has been a big help with looking at the fine details of a 4hp engine.
If the video is slowed down, the movement of the mechanisms can also be studied.
See 7:12 for the rocker arm.
Also at 3:52.

Looks like the ignition contact is screws to the bosses on the outer bottom end of the rocker.
There is a latch block that bolts onto the inner end of the rocker arm.
And a roller wheel inside of the arm over the cam.

Looking at 4:42, perhaps it is an optical illusion, but it seems that the inner end of the rocker arm is offset in towards the crankcase, when compared with the pushrod that rides in a recess in the top of the rocker arm?

I need to start a new assembly, and work out the vertical alignment of the cam, rocker arm, valve pushrod, valve chest and valve rod centerlines, etc.

I think I can see what is going to with the rocker arm.
I will attempt to make a 3D model tonight.

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<a href="https://www.youtube.com/watch?v=igHwlFFY2Us" target="_blank">http://www.youtube.com/watch?v=igHwlFFY2Us</a>

[Jasonb]

Yes there is an offset, probably 5/32 on your size engine

Are you going to cast the stop pin on the outer curve of the governor weight? I'd also slightly fillet all those square exrernal corners