Rotax 912 1:2 scale model engine build .

[Charles Lamont]

Very nice looking casting, and seems to be machining well too.

[ThomasM]

Hello everyone,

I made good progress on the machining of the crankcase. To keep you updated i made some pictures.

While i am waiting for the ordered brass material for the main bearings i started working on the next patterns for the propeller reduction drive and back cover of the engine.

The pictures :

1. Original engine
40: Fixture for clamping the two crankcase halfes in the same position repeatable.
41 - 45 : Machining
46 - 49 : Finished crankcase
 

[ThomasM]

47 , 48 : Finished crankcase
49 : Original crankcase and model

Best regards ,

Thomas

[Admiral_dk]

Very nice progress 

It's more complex than I originally thought - but your remark about it being finished, did not match my expectations about the number of holes etc. that needs to be drilled in the Crankcase, and seeing it next to the original confirms that 

Per

[dieselpilot]

Excellent work! I may have missed how you finished the pressed surfaces of the journals and webs. Were these also hard turned like the front shaft?

[ThomasM]

Excellent work! I may have missed how you finished the pressed surfaces of the journals and webs. Were these also hard turned like the front shaft?

Hello dieselpilot,

Sorry for the late answer, i was very busy at work and making the next parts for of the engine.
I machined the journals and webs to size + oversize for the press fit and hardened them without additional oversize for machining after the hardening. First time i made them i recognized that my oversize for the press fit disappeared after hardening because of oxidation ( ? ) while glowing them. They where 0,05 mm smaller in diameter after the hardening. So i did them twice with additional oversize to compensate  the shrinkage. After the hardening i only polished the surfaces.

Best regards,
Thomas

[ThomasM]

I made some progress on the engine.
I finished the crankshaft main bearings which also include the camshaft bearings in one piece. With this kind of bearing i can avoid the complicated line boring setup of the crankcase and it is was also possible to machine all the holes and channels for the pressurized oil from the oil pump " offline " direct in the bearings.

I also finished the model of the engine rear cover which includes the gears for the electric starter, the camshaft reduction drive and the drive for the water pump.

Maybe i can cast this part this weekend.

50 - 53 : Machining of the brass two pieced main bearings. They are paired together with dial pins.

54 : Milling the surface and cavity on the rear crankcase

55 : The holes in the bronze bearings which are not in the center of the part ( have to be exactly at this place. This holes are through holes for bolts which hold the crankcase halves together....

56 : The rear shaft of the crankshaft is still missing ...

57: Model for the rear engine cover ( green ) with raisers ingates and sprue.

Best regards,
Thomas

[AlexS]

Interesting way to make main bearings with channels for oil. I'll make a note of that for myself.
And castings look great!
Keep going