# Building the Felgiebel



## rweber (Mar 6, 2018)

Dear all,

after finish the Mono (http://www.homemodelenginemachinist.com/showthread.php?t=27456) I was looking forward to find a new project. When beeing at an exhibition I meet a guy that was showing an Felgiebel engine. It's supposed to be one of the first model engines available in Germany for home builders. Designed by A. Felgiebel at about 1939. The plans together with detailed building instructions were publishd in a book named *Benzinmotoren und ihr Selbstbau, A. Felgiebel, 1939. *I was able to buy a complete book from an ancient library to a moderate price. 
Compared to the Mono, this design is completely different. While the Mono consists of about nearly 600 parts this two-stroke engine is an example for simplicity. But there is one challange: The crank case and cylinder head are aluminium castings. I've never done that before, but I always wanted to do.  If someone is interested, here are a few pictues.

regards,
Robert


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## rweber (Mar 6, 2018)

First i build a 3D printed model of the crank case, ground coated a grinded.


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## rweber (Mar 6, 2018)

and put it into the sandbox.


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## rweber (Mar 6, 2018)

but the results are not so bad for a first try


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## rweber (Mar 6, 2018)

and milling the backside


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## rweber (Mar 6, 2018)

and final internal turning.


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## rweber (Mar 6, 2018)

and a Wohlhaupter is all you need :thumbup:


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## Herbiev (Mar 6, 2018)

Coming along nicely


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## rweber (Mar 9, 2018)

to the cylinder


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## rweber (Mar 9, 2018)

cylinderhead's holes


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## rweber (Mar 9, 2018)

and mill the ports


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## rweber (Mar 9, 2018)

in the workshop. I should consider to install a better isolation


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## rweber (Mar 9, 2018)

Casting was quite successfull, I have got five good crankcases. I took the best three of them. But building three identical engines would be boring. So, here are my variations. On the left side, the watercooled version, in the middle my own idrea and on the right side, the original as described in the plans.


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## Mechanicboy (Mar 10, 2018)

Hi, is it not too high transferport and too low exhaustport in the sleeve?


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## ZAPJACK (Mar 10, 2018)

To help you in this nice project, here is a couple of pictures of the Felgiebel
Nice job !
LeZap


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## Mechanicboy (Mar 10, 2018)

Now i can see the exhaust port is in other side of the cylinder.


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## rweber (Mar 11, 2018)

ZAPJACK said:


> To help you in this nice project, here is a couple of pictures of the Felgiebel
> Nice job !
> LeZap



Thanks for providing that pictures. You mounted it on a nice stand :thumbup:


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## rweber (Mar 11, 2018)

Mechanicboy said:


> Now i can see the exhaust port is in other side of the cylinder.



Yep you are right. See the picture I attached, that shows the locations.


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## rweber (Mar 11, 2018)

Does somboedy know, whats the purpose of this screw? Some Felgiebels have one, some not. And it is not drawn on the plans.

regards,
Robert


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## Barnbikes (Mar 11, 2018)

Drain the crankcase if you ever flood it?

Some dirt bikes and snowmobile use to have them.


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## ZAPJACK (Mar 12, 2018)

Your right barnbikes !
LZ


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## rweber (Mar 15, 2018)

I cannot fiish the cylinders until some material is delivererd. So I'm moving forward to the cylinder head. This will be an alu casted part again. If it works  I started creating a computer model and let it print on the 3d printer.

(Don't blame about the printing quality ;-) My 3D printing guy switched to a new filament vendor and this requires some adjustemt to the printing paramters for proper results. In the meantime now I have about 5 cylinder heads and they are looking better from print to print)


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## rweber (Apr 10, 2018)

I tried to build the cylinderhead via lost wax technique. Therefore I created a 3D printed model made of Moldlay.


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## rweber (Apr 10, 2018)

I put it into some leveling compound and lety it dry. Then I put it into the curing oven and sloooooowly increased the temp to 270°C to let the wax melt out. This took about 2 hours, but the wax dropped out completeley. Great, so far.


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## rweber (Apr 10, 2018)

Highly motivated, I moved on to the casting process.


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## rweber (Apr 10, 2018)

But the result was very disappointing. 

It looks to me that the Alu was not able to push out the ambient air. Perhaps I filled it in to fast. I don't think the Alu cooled to fast, it came out very "liquid" from riser. Alu was at 700°C, the mould was pre-heated to 200°C, I used some salt as flux and wash soda for degasing.

I'm not sure where the problem resides. Maybe there is more than one 
Or it is even not possible to make it this way 

Any comments and suggestions are welcome!

cheers,
Robert


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## RonGinger (Apr 10, 2018)

I have been told that you must use a vacuum under the flask to pull air out of the investment. I was able to spend a few days in a professional investment shop and all their flasks were perforated and placed into vacuum containers before pour.

For small items jewelers use centrifugal spinners to throw the metal into the mold, but I think your part might be to big for that.

I also saw a write up of a n idea to use s team force. A cover is made for the flask and has a big wad of wet newspaper in it. As soon as the metal is poured the cover is placed over the flask and held down so any steam generated forces the metal into the mold.

Bottom line is gravity alone is not enough to get metal flow fully into the mold.


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## Mechanicboy (Apr 10, 2018)

Die casting is the last solution.. There is 2 difference die casting: Low pressure die casting with air pressure or high die casting with piston.


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## rweber (Apr 12, 2018)

Hi Ron,

thanks for your thoughts. Especially the steam method looks interesting dangerours. There are some videos around where they press a can filled with moist paper on the mold. This is only for the brave ones. 

The centrifugal method you mentioned looks feasible to me. I will have to do some investigation about this. I think I should be able to handle it.


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## rweber (Apr 12, 2018)

Mechanicboy said:


> Die casting is the last solution.. There is 2 difference die casting: Low pressure die casting with air pressure or high die casting with piston.



Hi Jens, 

at the upper picture, there are no ejectors where the air can leave. Does this require a porous mould where the air can get through?


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## Mechanicboy (Apr 12, 2018)

rweber said:


> Hi Jens,
> 
> at the upper picture, there are no ejectors where the air can leave. Does this require a porous mould where the air can get through?



It must be ejectors to reduce air pressure inside when the molten meatai is pressed into the mould. Mould an be made of steel or similiar material. The ejectors are smaller than you find in sand casting.


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## rweber (Apr 19, 2018)

Thanks for all of that casting hints and tips. I will have to think about this in a quiet minute. In the meantime I will proceed with activities that I am familiar with. I started silver soldering the transfer ports and the intake.


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## rweber (Apr 19, 2018)

Putting them into 65°C sulfuric acid (about 12%) greatly removes the flux.


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## rweber (Apr 19, 2018)

Silver soldered the water jacket and pipes.


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## rweber (Apr 19, 2018)

Mounted and centered it on the lathe and used a fresh sharpened HSS turing tool. Unfortunatley I have no internal grinding tool.


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## rweber (Apr 19, 2018)

Unexpectedly found some time yesterday  Time to build the cylinder head for the water cooled version.


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## rweber (Apr 19, 2018)

Flat countersink and drill the holes on the milling machine and final turning.


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## rweber (Apr 19, 2018)

Put it all together. Slowly it takes shape.


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## rweber (Apr 24, 2018)

Now beginning to work on the crankshafts. I will build them of C45 to harden and temper the pin. They will be pre-turned and later grinded.


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## rweber (Apr 24, 2018)

Facing and centering the back-side.


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## rweber (Apr 24, 2018)

Putting them between centers to turn them one by one.


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## rweber (Apr 24, 2018)

Adjusting the support for turning the cone.


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## rweber (Apr 26, 2018)

Turning the bushes, made of RG7. Heating up a the crankcase and they will slip in like a charm.


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## rweber (Apr 26, 2018)

Finally shorten the cases to the desired length.


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## rweber (May 3, 2018)

Align and scharpen the grinder


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## rweber (May 3, 2018)

Some more turning, and the crankshafts are ready to be checked against the  bushes.


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## rweber (May 8, 2018)

As the support is already in the angle for the taper, turn the propeller driver disc.


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## rweber (May 8, 2018)

...and drill the holes.


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## rweber (May 8, 2018)

Now moving back to the crankshafts, turning them into final length.


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## rweber (May 8, 2018)

Finally created a little helper tool for turning the crankshaft pin. Then the weekend was sadly over


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## rweber (May 15, 2018)

Turning the crankshafts pin, leaving 4/10 plus for later griding after tempering.


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## rweber (May 15, 2018)

Forming the counterweight


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## rweber (Jun 23, 2018)

Just back from vacation, and right into the workshop. After riding my motor bike two weeks across Sardegna it's time to be productive again  I'm continuing the build process with a not to difficult part. The connecting rod. Made of C45 with RG7 bushes.




View attachment 102366






cheers,
Robert


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## rweber (Jul 17, 2018)

Finally I found some time to continue with the Felgiebels. I started making the piston rings. According to the book, Felgiebel itself bought them from a model store, made of cast iron. After finishing a first try ring, it turned out, that the ring must be bent very far to slip over the piston. This is too much for a normal, untreated cast iron. The ring will not spring back into its original position. It will remain deformed and the pressure to the cylinder will be too much, in my opinnion. Fortuntely I used GGG60 cast iron which can be excellent hardened and tempered. The termpering temperature is suprisingly high at about 550°C.


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## rweber (Jul 17, 2018)

Some time was left, so I continued building the piston. I modified the inner construction compared to the original. Felgiebel turned the inner side, leaving less bearing surface (about 1.5mm each side) for the piston pin and some kind of Pilz (german word) to fix them. I milled an oval to the inner side to give more bearing surface and used the usual clips to fix the pin.
































Not finished to far, next step will be to mill the nose.


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## Cymro77 (Jul 17, 2018)

Amazing! I must be on the wrong site!!  This looks like professional work.


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## rweber (Aug 7, 2018)

Ok, here we go again. Finishing Pistons, forming the nose.







and the nuts for the piston rings.






and the very tiny nuts for the pin.


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## rweber (Aug 7, 2018)

Machining the piston pins

pre-turning the silver-steel material, and drill a hole inside.







After harden and tempering, checking concentricity accuracy. 
Light taps with the hammer will fix it, if necessary ;-)







Finally grinding


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## rweber (Aug 26, 2018)

Next step is to build the contact breaker. I start with the holder, made from 1.5 steel. I welded a package of 4 pieces together for better mechining and to save some time, too. This would be a job for a EDM. But I don't have one. Therefore a mill must do the job.







Looks not too bad 








Bendig to its final shape.







After sandblasting it looks like this:







Quickly turn the isolators, made of PVC







Done, so far.


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## rweber (Aug 26, 2018)

Next piece to make is the contact holder. Made of a sheet of brass, reinfoced with a silber soldered strip, also made of brass.











The contacts itself are made of silver steel.






and are rivedted to the holder.


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## Pierkemo (Aug 27, 2018)

*Whaaawww, very nice build!!!!!
Also very wel done, the castings!!

Pierkemo*


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## rweber (Sep 1, 2018)

Next part is not so easy to build, the contact spring.

Starting with this:







Bending around several times ...






after harden, temper and sandblast it looks like this:






finally assembled contact:


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## rweber (Sep 1, 2018)

Next part to build is the fuel tank. 
I do not like sheet metal work that much  But it has to be done. The tank is build of a 0.25 sheet of brass.

First I made a helper tool for forming the caps. The sheet has to be annealed several times to punch it around the radius.






Soldered togehter:


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## Mechanicboy (Sep 1, 2018)

Better to create the tank cover with metal spinning method, it's fact much easier and more beautiful than hammering the edge of tank cover.  You can do it on lathe. The brass sheet must be annealed to be soft to form on pattern. See this movie how to spinning the parts..






Here is the info about metal spinning..
https://en.wikipedia.org/wiki/Metal_spinning


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## rweber (Sep 2, 2018)

You are absolutely right. This will be a much better approach. I never could motivate me to create the nessecary tools needed for spinning in the past. Did not need them often in the past. But in the time I spent knocking with the hammer I would already have built them. You make me start thinking...


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## rweber (Sep 11, 2018)

OK, I took the time to create some metall spinning tools for me. 
Now the result looks significantly better than my first try. 
Thanks to Machanicboy!


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## Mechanicboy (Sep 11, 2018)

The fuel tank cover look much better and beautiful!


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## 777engman (Sep 12, 2018)

How about some photos of the tools you made for spinning?
Regards
Dean


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## rweber (Sep 19, 2018)

777engman said:


> How about some photos of the tools you made for spinning?
> Regards
> Dean



Sure, here we go:


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## rweber (Sep 20, 2018)

Some carburettor parts


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## rweber (Sep 25, 2018)

Some gastank parts






and a mounting plate. Used for drilling the careburettors holes and later as testbench.


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## ixb1 (Oct 22, 2018)

rweber said:


> But the result was very disappointing.
> 
> It looks to me that the Alu was not able to push out the ambient air. Perhaps I filled it in to fast. I don't think the Alu cooled to fast, it came out very "liquid" from riser. Alu was at 700°C, the mould was pre-heated to 200°C, I used some salt as flux and wash soda for degasing.
> 
> ...


Hi
Maybe possible solution is simple mold by imprint the head pattern horizontally into sand with fins oriented down.


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## rweber (Oct 22, 2018)

ixb1 said:


> Hi
> Maybe possible solution is simple mold by imprint the head pattern horizontally into sand with fins oriented down.



Also tried this way, but the gravity produces to less force, to press the alu down and let the air come out.  The result was not better as in the picture you quoted. Perhaps it would work, if you fill the alu very very slowly, but then it would cool down until you are finished.
Now I'm thinking about a simple centrifugal cast mechanism... I know, the head can be simply milled and turned, but I'm interested if I can get it done this way.


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## ixb1 (Oct 22, 2018)

Is acceptable head with thicker wedge profile fins like on old Enya or McCoy engines?


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## rweber (Dec 3, 2018)

Finally I decided to build the heads from a round bar, to get this project done.


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## rweber (Dec 11, 2018)

Ok, alle the parts are completed. Now putting it all together ... 




This is the watercooled version, also described in the book.




This is the "original" version from the book:




This is my personal version, some slight modifications. A longer intake tube and a "tuning" head with higher compression. I'm curious to see how it will run ;-)




The whole Felgiebel family:




and from behind:




Can't await to see them (homefully) run.

More to come....


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## rweber (Dec 17, 2018)

Jippie, they are running. All of them ;-) I did two short vids if you want to see. They can be found here: https://www.homemodelenginemachinist.com/threads/finished-my-felgiebel-project.30741/

Merry Christmas!


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## Billitmotors (Aug 18, 2019)

Would you have a copy of the STL file for the crankcase  that you would be willing to share?
Rob.


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## rweber (Aug 18, 2019)

I sent you a PM.


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## Pierkemo (Aug 19, 2019)

Hello Rweber, yes i like to receive the STL for the crankschaft. Many thanks, Pierre


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## rweber (Aug 19, 2019)

sent you a PM.


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