Rudy Kouhoupt's Open Column Steam Engine - Cast & Double Size

[bmac2]

Hi Ved
I’m following your build with great interest. It’s hitting a lot of my favorite things, model engine, fire, molten metal, and I keep hearing the sirens song of 3D printing.

I haven’t done much with plaster investment casting but have had good results using I use one part plaster/ one part fine sand/ one part grog (it’s just pulverized used investment). You can avoid air bubbles forming on the surface of the pattern by first brushing it with a mix of water with a couple drops of (Propylene glycol) the stuff you put in the dishwasher to eliminate spots.

 

[vederstein]

Hi Ved
I’m following your build with great interest.

Thanks for following the trials and tribulations of someone who has an extremely limited idea of what the hell he's doing.

I printed off the two flywheel halves. I'm going to give the printer a rest for a while. I need to pour lots of investment over the upcoming weekend and probably make lots of scrap.



...Ved.

 

[vederstein]

I also print PLA on blue painters tape. Some people say heat the bed, others say don't heat the bed. On small-ish parts, 25mm square or less, I don't use any bed heating and normally don't have any problems with print bed adhesion. On larger parts where the print head travels more than 50-75mm of linear travel before the next filament is laid down, I've found that with my printer I need to heat the bed(I use 60°C)
Don

Now that I have the heated bed working, I've have the same experiences as you. Some of those larger parts I've printed lately wouldn't have a chance without the heated bed.

Everything printed has been PLA thus far because my previous PLA burnout was fairly successful (and the wax filament is expensive) although the pour was a complete failure.

...Ved.

 

[bobs7-62steamair]

Just received the Rudy K book, "Working Steam Engines" Open column in 2x scale up looks like a fascinating project. Do you happen to have any detail parts drawings in the 2X size available? Would be happy to pay reproduction and shipping cost.
Regards.
Bob

 

[vederstein]

Just received the Rudy K book, "Working Steam Engines" Open column in 2x scale up looks like a fascinating project. Do you happen to have any detail parts drawings in the 2X size available? Would be happy to pay reproduction and shipping cost.
Regards.
Bob

I sent you a PM. Let's please continue this discussion off the forum.

Thanks,
...Ved.

 

[vederstein]

I've been very ill lately and that's why I missed my window for what was to be my second pour. It will happen later. I did manage to add the sprues to the next set of molds though...

 

[Wolfie01]

I did notice you had no vents. When I did my first pour, I had vents for each pillar, I didn't have my mould glowing hot either...

 

[vederstein]

As I'm preparing my molds for tomorrow's pour I have one mold in the furnace burning out. I figure that I might was well use the waste heat and put another mold on top the furnace for preheating the second mold.

 

[vederstein]

Ok, now I'm losing my patience.

First of all, the burn out from yesterday:

I put it into a bucket full of sand. After several hours of cool down I gently grasped it. It disintegrated. I guess heat stress? That's one mold down the tubes.
​

So I burned out another item, a post with a vent in the mold. To increase hydraulic pressure, I printed a PLA sprue and when embedding the mold & sprue into the sand it looked ok. During the pour the sprue lifted off and no material went into the mold.





Third pour, third mold. The burn out look ok. I enbedded another PLA sprue. On the pour, the system began to bubble (boil?) splashing molten aluminum. This is only one where some material made it into the mold. But it wasn't good enough and the burn out was insufficient. Don't know what caused the bubbling but it was a dangerous situation.

[ame]http://www.youtube.com/watch?v=ER8jDn9RmaA[/ame]




I guess it's time to switch to the wax filament and try again. Other things learned:

• A plastic sprue don't get it.
• Make the burn out longer
• Bury the investment when it's hot and pour when it's hot.

Anybody else have some insights? I'm learning but this is getting annoying. I really thought I would have had a good part by now.

 

[abby]

It is very unlikely that you will have a successful burnout without a controlled kiln.
The free moisture needs to be removed first , this is done at around 180°C for about 5 hours , chemically combined water then needs removing at around 350°C for a couple of hours with a gradual increase to 550°C.
Final burnout should be at 725°C for 3 to 5 hours.
Any pattern media whether it be wax or plastic will expand during the heating cycle , wax melts quickly thus avoiding expansion pressure on the investment mould. Many plastics do not melt and the mould is cracked as a result.
Investments cements are formulated from carefully selected refractories with known expansion characteristics , they are designed to withstand the rigours of the heating cycle with a minimum of cracking.
Homemade recipes are rarely succesful on a repeatable basis but re-inforcing with something like chicken wire can help , the addition of chopped glass fibre strand may also work.
Commercially produced investment is not cheap but compare the cost against the cost of patterns , time , fuel and effort .
You may find some tips on my website/forum
http://www.unionsteammodels.co.uk/
Dan.

 

[vederstein]

After some dejection at my failures I have to agree with Abby that my method just isn't going to get there. So it's time to take a step back and retool.

First, I'm going to try some open molding for some components (like the cylinder head) where one entire side gets machined anyways.



Second, I guess I'm going to have to learn about sand casting. This will be a project all in itself. To start, I need to make a flask and some green sand. I'll be following this guy's recipe.

[ame]http://www.youtube.com/watch?v=2rAQxw6X6uc[/ame]


Then I'll be printing some split patterns (the picture shown is of the posts). Because of this, I need to check for undercuts when pulling the patterns out. So for example, the flutes on the posts are gone.




That's all for now.

 

[vederstein]

Today I made the green sand and a casting flask. To see what kind of difference I would have, I made an open mold of the cylinder head from both plaster which baked in the oven for three hours and the sand.

The sand mold, though not quite good enough, was much improved over the plaster mold. It's still a failure, but less of one. Now I feel like I'm making some progress.

I did make a two part mold, but the sand wasn't sticky enough. I think I need to add a little bit more water and/or clay.

I'll need to re-evaluate some of the smaller details I have in the parts and simplify as required. For example, I'm going to need to remove the text on the cylinder head.

...Ved.

 

[bobs7-62steamair]

Ved has embarked on casting parts for the 2x Vertical originally designed by Rudy K. I am off building the same type engine using one purchased casting, the Flywheel. Have first seven parts made to date. Support columns were lathe made using a combination of Knurling and grooving to achieve some different column design that can be easily made--see pics. Will send additional picks and potential pitfalls to avoid building this engine.
Bob

 

[Engineville]

Sir,
Disclaimer: The following in an opinion.
I watched your video panel #69 of pouring molten Al . . . massive and intense gas formation begins immediately upon Al pouring; gas is coming from combusting sprue and then from the PLA.
To reduce the formation of gas, need to reduce the mass that the molten Al needs to burn as it flows in to resulting cavity.
Consider setting the 3D printer on a setting of internal part structure that is as much open space and as little PLA as you can get away with and still maintain part shape with a smooth surface. In effect you’re trying to produce a result similar to lost-foam casting that uses highly expanded polystyrene beads.
The 3D printer that I messed with three years ago was a very simple one. But the software had different setting for internal structure, e.g., 75%, 50%, 25% void-open space.

 

[vederstein]

Sir,
Disclaimer: The following in an opinion.
I watched your video panel #69 of pouring molten Al . . . massive and intense gas formation begins immediately upon Al pouring; gas is coming from combusting sprue and then from the PLA...

I'm giving up on the lost PLA route. After my experiences, I have to agree with Abbey that I'm just not properly tooled for it. I did try printing some components with the wax filament. The wax printed ok for small components. Parts for this engine are too big though. Even with the heated bed, the wax filament warps and it warps a lot.

I'm focusing on sand molding at this time. I'm going to lose some of the smaller details, but it's the only method (save for the lost foam) thus far where I've made something of an improvement over earlier tries.

I'll get there, but this learning curve is much steeper than I was expecting.

I will persevere!

Also, I wish Bob the best in his barstock version of the same engine. At this rate, he'll be finished before I.

...Ved.

 

[vederstein]

Another Sunday another set of pours.

This time was my first try at a closed mold sand cast and my experience was much much improved. The video shows the first pour. The cylinder head is a flat back pattern. The bearing block is a split pattern.

[ame]http://www.youtube.com/watch?v=TZ5PH-MRqEs[/ame]

In the photo, the casting on the left is the first pour. The casting on the right is a bearing block and one of the posts. The post was created with the "cope down" molding technique.



All of them are a bit rough, but with some work can actually be used. Eventually I'll machine them up and see what I get. Overall today was a much improved day.

It took me several tries to get to this point. I learned that the sand need to have more water in it than I originally thought. In the end I had it a little damp.

That's it for today.

...Ved.

 

[vederstein]

My wife is out of town this upcoming weekend so I hope to get a lot done.

Tonight I gave it a go at machining the one post casting I have. The casting itself isn't great, but it did machine ok. The bad casting side I can rotate to the inside of the engine to hide it. Eventually I may have a go at re-creating this one.

I found myself flipping the part several times in the lathe.

I first worked one end round.
Then I flipped and worked the other end.
Then I cut off the end.
Then I flipped it a last time and cut the opposite end to length.

The ends aren't even, but I think if I proceed with the same pattern on the other three, they'll look somewhat similar.

...Ved.

 

[vederstein]

Got a couple of pours done today after work.

I made two posts in the first pour and in the second pour I made another post and a bearing block.





All of them are better than my earlier tries.

I initially made 50 pounds of green sand. It really doesn't go very far. I cannot fill two flasks entirely full. I guess I need to make more sand.

In the video I was trying to make the cylinder mold. My cylinder pattern doesn't have any draft where the core goes and that's why it breaks away when I pull the pattern out. It's no big deal though considering that's the core anyway. Not knowing anything about cores, I made it out of the same sand. As you can see, it falls apart. More learning is involved in how to make cores.

[ame]http://www.youtube.com/watch?v=w5xRXzioBk0[/ame]

My technique is improving...

 

[vederstein]

I've machined up the four posts.

They aren't perfect, but as I've mentioned before, I'm not a perfectionist. Overall, I think they look ok for a first self cast engine.

 

[bobs7-62steamair]

Hi Ved: Your columns look great. Sand casting is not all that bad and with experience I am sure it will get better. Have a couple of questions i will address off line.
Regards.
Bob