Planis Farm Boy Engine

[Plani]

Hi everyone

Since I always enjoy watching buildlogs, I want to start one of my adaption of the Farm Boy engine.

Some time back i got my hands on a set of drawings of the famous Farm Boy engine from Jerry Howell. I liked the design of the engine a lot and also the fact that it can be made from bar stock.
Since I'm all metric I had to redraw the plans. While playing around on the CAD I figured, I might as well make the engine a little bit bigger than original and so I settled for a scale of 32mm to the Inch. This means the engine will be about 30% bigger than original.



The engine specs are:
 - Bore: 32mm
 - Stroke 44mm
 - Compression ratio 4:1
 - Displacement 35cc
 - Flywheel diam 192mm

Because I've never made a one piece crankshaft before, I decided to start with that one, so in case it is not turning out right I can still abort the project...

To start with I got some normalized S355 bar which will hopefully not distort too much while being machined




The round bar was machined square and then the shape of the crank was roughed out




Then turning the crank pin




Roughing the outer parts of the shaft




Since I've done some wrong thinking , the crankshaft hat to be shortened and center drilled  again



To then finishing the shafts




That's what it looked like so far. I left some material to take a skim cut on the crank webs too.




Moment of truth  I think I can live with a runout of about 0.02mm 




So I went on with cutting the keyways




And cutting the key accordingly




Done:




Plani

[yogi]

Looking good! 
I'm looking forward to see this one coming together. 

[Roger B]

That's a good start  You may find that the runout changes over time as the stresses in the metal release. Generally it can be trued up again.

[Brian Rupnow]

Nice cad work and very nice job on the crankshaft.---Brian

[awake]

Great work! Looking forward to seeing more.

[Plani]

Thank you guys for the kind comments 

Roger, I sure hope it will not distort more. But we will see, time will tell....

Plani

[Plani]

Hi everyone

Next I started with the flywheels. There have been two blanks of steel of pretty much the perfect size lying underneath the shelf in the shop for ages. As it seems, these have finally come to their destination. 


Ready to go




Turning the outer shapes






I decided to mill the reliefs in the wheels instead of turning them. Here are the two Flywheels ready for the mill




  The crappy endmill I used for this didn't quite cut it. It got dull an therefore pulled out of the collet. This is the inner side of the governor side Flywheel. That's going to leave a mark. I guess....
But since I'm planning to paint this engine, I think I'll be able to fix that.




I purchased some decent carbide endmills (what I should have done from the beginning) and these made live much easier.




Relief milled of the non governor side flywheel




There was some material left at the bottom of the reliefs to be cleaned up on the lathe.






Next step was to mill the spokes.




Then a radius cutter was used to mill the radii on each side of the spokes.




Milling the slots for the spoke lugs on which the pulley will be fixed.




Milling the relief to balance the weight of the piston using a ball nose endmill.






The flywheels so far. There is still the bore to do and on the rims there is also some material left for a final cut in the same set up as the bore will be done.




Thank you for following along an stay tuned for more
Plani

[kuhncw]

Very nice work on the flywheels.

Chuck

[Dave Otto]

The flywheels are beautiful!
Very nice work.

Dave

[Plani]

Thank you for the kind comments Chuck and Dave 

Is it only me or does some one else also know this behavior: On a project first the most demanding Part (i.e. crankshaft) is made, then the "interesting" ones like flywheels and then it boils slowly down to the fiddly bits which need be done...
So to counteract this at least a little, I decided to make the spoke lugs next.


Milling the contour from some steel bar stock:




The hole for the bolt drilled




Milling the thickness, all of the lugs in one shot




Test fit




Thank you for following along.
Plani

[Admiral_dk]

Is it only me or does some one else also know this behavior: On a project first the most demanding Part (i.e. crankshaft) is made, then the "interesting" ones like flywheels and then it boils slowly down to the fiddly bits which need be done...

No - I believe that this is a very common thing among many of us 

Nice parts so far 

[Plani]

Hi everyone

Next part to make was the conrod.

I started with the bearing cap of the big end




The bearing cap was then bolted in place on the stock for the conrod in order to mill the outer contour




Milling the recess on the first side




And then the seat for the bearing and the relief




First side done




Set up for the second side. In the scrap aluminum underneath were two bosses milled to locate the con rod.




Milling the contour




Contour done




And the final setup to mill the lubrication access in the small end




Finished part




Thank you for following along.
Plani

[b.lindsey]

Very nice progress Plani. I am just seeing this thread. The parts are all very nicely finished as well. Looking forward to your continued progress on this great engine.

Bill

[yogi]

Looking good! 

[scc]

Cracking job Plani  I see no coolant so do you use a gentle airstream to keep swarf away from cutters? That must help towards your beautiful surface finish.          Terry