Fairbanks 80HP 3 cylinder model

[cfellows]

I can't seem to get excited about resuming work on my Bessemer model, so I've decided to tackle another engine model that has been on my list of projects to do for some time now.  This is the Fairbanks 80hp, 3 cylinder. 



Castings have been available for an IC version and I've seen several of these at model engine shows.  Here is a video of one such model...

http://www.youtube.com/watch?v=Gqsi6Z2qsEI

My engine will be somewhat smaller with a 3/4" x 7/8" bore and stroke.  And, although my engine will be four stroke in operation, it will be powered by compressed air using over head intake valves and my slave exhaust valve.  For those of you familiar with the IC model, and perhaps the original engine, my version will have the main bearings and caps contained in the upper crankcase half instead of the bottom.  While I want to adhere to the original scale dimensions as closely as I can, my model will be somewhat stylized and probably not have all the detail seen in the original.  However, I will try to add some bling and make it somewhat interesting.

Finally, I'm making a serious attempt to model each part in Alibre before constructing that part, so I should end the project with a complete set of drawings.  Below is the first installment showing the upper crankcase half.  It will be machined from solid aluminum or cast iron, yet to be decided.  If you download the 3D PDF, you can click to activate it, then rotate the part by holding down the mouse and dragging it around.

Chuck

[steamer]

Sweet Chuck!  I'll be watching along!

Dave

[smfr]

Me too. Looks like a great engine to model.

Simon

[cfellows]

Thanks, guys.  Didn't have the right materials on hand to start on the engine this weekend so SWMBO "pursuaded" me to build a doll bed for the granddaughter.  Now everything in the shop is covered with sawdust... 

Went down to the local metal supply store today and picked up a nice chunk of Aluminum.



Measured it up and mounted it in the bandsaw to carve off a piece.





Finally cleaned up the two edges with a 2" face mill.  So now I have chunk of aluminum that's oversized by about 1/8" on top and sides and almost an inch too long.

This is going to require a lot of hogging with an end mill and my experience with this sort of thing has always been mediocre at best.  Guess the secret is to take it slow.  If anybody has any hints or videos worth watching on doing this without a CNC mill, I'd love to see them...

Chuck

[Don1966]

That's a nice engine Chuck, I will be following as well. Good luck bud.

Don

[steamer]

Hey Chuck,

I can say ...from my perspective....start by squaring the block up flat, square and parallel.   Pick one corner as a datam...locate off that datum for all your cuts.

I would cut the corners with an extended slot mill...and then connect the corners...it leaves a volume for the chips to go while your excavating the center of the pockets.....cut the the straight lines between the 4 corners. Then cut the stock out.

As far as the cam shaft bore....A between centers boring bar might be in order.

Leave the outside features until last.   Keep the block square for as long as you can.  It makes finding and indicating a lot easier.

See my post on Milling buttons...in my Wallaby thread.

Hope that helps!

Dave

[cfellows]

Thanks, Don, I appreciate the support. 

Thanks for the suggestions, Dave.  Unfortunately I already started and did just the opposite of your suggestions.   



I first positioned the spindle over the middle of the cutout area.  Then I set the spindle depth stop to bottom out 1/8" above my final depth.  With a 1/2" roughing mill in the spindle, I used the drill press handle to apply steady downward pressure as I cranked the table back and forth a counted number of turns each way to establish the slot.  The resulting slots are undersize in depth, length and width.  I am planning to sneak up on the final dimensions by working from the inside out.

Chuck

[steamer]

Looks good from here Chuck!....what ever gets you there that works....Works!

I'd keep the outside flange off until last though....make it easier to grab in the vise.

Dave

[stevehuckss396]

Your plan sounds like it would work fine.


Judging from the size of the stock it going to awefully hard to get 80 horse out of this thing. 

[cfellows]

Your plan sounds like it would work fine.


Judging from the size of the stock it going to awefully hard to get 80 horse out of this thing. 

Did I mention I'm going to run this off a Scuba tank at 4500 PSI!   

Chuck

[cfellows]

One last picture for tonight.  I've got about 5 hours total into this so far.



I have the hollowed out parts to within about .015" of each line and .005" of the depth.  I'm very happy with the results.  I found that by going full depth in the initial slots, it was much easier to control the widening process.  The roughing bit cut pretty effortlessly at full depth and there was no tendency to dig in or pull the table against the leadscrew backlash.

I'm going to leave the openings slightly undersized until I finish the crankshaft.  Then I'll remove the final few thousandths as needed to fit the crankshaft to the crankcase.

Chuck

[steamer]

Looks great Chuck!....I think maybe I should be taking your advice!

It would appear the tough part is mostly done!

Dave

[cfellows]

Looks great Chuck!....I think maybe I should be taking your advice!

It would appear the tough part is mostly done!

Dave

Thanks, Dave, I always appreciate your comments and advice. This was the part that I dreaded most and tried to think of some other way to make the crankcase, including a weldment and a casting.  But, in the end, I wanted a one piece crankcase top from barstock which others could duplicate if they wanted to build the engine.

I got started on the next piece that I don't expect to be easy.  I'm calling this my first attempt fully expecting to make 2 or 3 before I get it right... who knows, maybe I'll get lucky!  This will be a built-up crankshaft.  I'm starting with a piece of hot rolled steel, 3" long x 1" wide x 1/2" thick.  The maze of layout marks looks a bit confusing.



Next I drilled 7/32" holes in what will be the opening between the webs.



This was followed by sawing out the waste and mounting it between centers in my lathe.  Forgot to mention that I had drilled countersunk holes on each end.



Here it is after I have turned down the connecting rod journals to 1/4".



And finally, the three crankshaft throws have been separated.



Next I need to clean up and size the thickness of the sawn ends.  Then I'll drill 5/16" holes through the other end of the webs for the crankshaft journals which will be made from 5/16" drill rod.  These will be loctited and perhaps pinned to secure them.

Chuck

[steamer]

Getting the popcorn!   Nice Cranks!
 
Dave

[Don1966]

Nice cranks! Gee Chuck, your cranking it out there Buddy.

Don