Felgiebel 16,6

[Cogsy]

Guys - please post in English, even if it's just run through Google translate. Thanks.

 

[Mechanicboy]

F-DS and Matthias, for model engines with contactbreaker, you can order the coil from this website:

https://minimagneto.co.uk/Products.php

http://www.model-engine-ignition.com/home/coils

 

[F-DS]

Production of gypsum mold for casting of engine crankcase. If the casting is not according to my wishes, I will also make a mold from sand.
I used an ordinary cutting spray as a separator.

 

[Matthias]

Be careful about pouring aluminum into Gibs. Gypsum must be completely dry, otherwise steam bubbles will form. It may be that aluminum splashes on you.

 

[F-DS]

Yes, I know. I have already cast into the plaster mold. Let the plaster dry for at least 2 weeks under the fireplace.

 

[F-DS]

I have a roughly finished connecting rod.

Bearing ready for pressing.

 

[F-DS]

Grinding the connecting rod width to the final dimension of 6.5mm

 

[F-DS]

Finished connecting rod.

 

[F-DS]

I cast the crankcase of my Felgiebel engine. During casting, I had a small accident, when the metal was poured into the mold, the mold broke and most of the aluminum leaked out of the mold. I then glued the mold (using a regular glue stick, because it contains little water) and I cast it again, which was successfully cast. In fact, the casting is better than it looks in the photos. The last picture shows the first cast scrap, which is porous and full of bubbles. These bubbles were caused by the evaporation of trace water.

When using gypsum molds, there are always problems with moisture, which I have been dealing with for a long time, but they are difficult to manufacture and do not allow me to reach such a surface as gypsum molds. I have repeatedly tried to conclude that the gypsum mold must first be "burned" by pouring molten aluminum into the mold before casting the usable casting itself, which will cause immediate release of steam during the first casting and thus spoil the potential casting. Only after this "firing" can liquid metal be poured into the mold without fear of the occurrence of additional steam, which otherwise causes cavities inside the casting, rough surface and porosity. The mold used now was dried for several weeks under the stove for a few weeks, then fired in an oven at 200 ° C for 1 hour, and finally just before casting I heated it for about 80 ° C with a hot air gun in a special "preheating box". This measure did not help either. In the form you can see made inscriptions, which unfortunately did not cast. (E only)

 

[Dragons_fire]

I'm learning lost PLA casting in plaster and I've found that adding just a few percent of Portland cement and a few percent of sand really helps with the strength of the mold. The cement really slows down how quickly the mold dries though. I let it cure for a week, then put it in front of a space heater for a day and that blows warm air over it and helps remove moisture. Then goes into an old pottery kiln and heats to 110°C for 4 hours, then up to about 180°C for 2 hours, then up to 350°C for another 4 hours. I let it cool in the kiln overnight, then the next day it's ready for casting. It makes an almost exact copy of the surface finish on the 3d part, and there is no noticable voids in the cast part.

I also find it's a lot safer to surround the mold with sand (bottom and sides) before pouring the aluminum. It seems to hold any cracks in the mold together, but will also prevent any spilled aluminum from running all over the place.

 

[F-DS]

to: Dragons_fire

Does the drying of the mold you described help make the first cast usable? The tip surrounding the mold with sand is good, it increases safety and slows down cooling, which helps to better shape the internal structure of the casting.

 

[Dragons_fire]

I'm doing lost PLA, so the 3d printed part is actually burned right out of the plaster mold. These molds are only useable one time, and they are broken apart to reveal the part inside. Attached is a pic of some handles I made. They are about 3/8" (10mm) thick. There has been some grinding and some machining done to them before this pic, to remove the sprues and clean them up a bit. If you look close, you can see how it picked up the layers from the 3d printed part right in the aluminum.

 

[F-DS]

Since I am not satisfied with the surface of the crankcase casting, as there is time (due to the presence of the flu) and because I wanted to have the engine name "FELGIEBEL" on the casting, I decided to cast the crankcase once more, this time in sand mold. I started to adapt the model for this method of casting, I made letters from the putty. The process of making letters can be seen from the photos.

 

[F-DS]

I glued the letters to the crankcase model, which I then painted with a thicker layer of synthetic varnish.

 

[TonyM]

I'm looking forward to see the final casting. Where are you in CZ. I am in the north near Novy Bor

 

[F-DS]

I live in the Olomouc region, Přerov district. Nový Bor is 320 km from us.

 

[Rudirk]

This is one of my first casting. I made a easy wood model and buried sand for casting. The next part was much better. I made a lot of 0,5 mm air holes in sand.

 

[F-DS]

How did you achieve cavity formation in the casting? Two-part casting form?

 

[Rudirk]

Yes, I made two wood parts .

 

[F-DS]

Sand preparation. As a binder, I used ordinary clay, as sharply sieved construction silica sand. I started with a binder / sharpening ratio of 215/1000, with a gradual end to 1/3. The mixture is full of clay, but it forms a smooth surface. I'll see if a higher proportion of clay does not matter during casting.