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Steve Peirce,     Uniontown, OH            Start 2/24/2004,  Complete 4/20/2004

Darling,    1 Cylinder, Vertical

Engine Type:  Compressed Air
Bore: .312"
Stroke: .500"
Valve System: Prototype Design
Operating pressure: 35psi, at break in, PSI required has been dropping as the engine breaks in.
Flywheel Dia. 2.000"
Skid Length: 4.500"
Over all Height on skid: 4.000"
Steve Peirce's web page

Final Pictures


NAMES 2004: The Darling finished second , just behind Ron Colonna's "Whizzer", a beautiful piece of craftsmanship. Can't complain about loosing out to such a fine piece.
 I got some nice photo's of the Darling with the two engines that I had photo's of to build it from. Might be neat to add them to the gallery. It was amazing to see the Darling with the original models it was designed from.

  Steve with full size Monitor


 There are still a few pieces off of the engine, such as the serial plate, spark plug wire and few other goodies. I'm waiting on some decals. Once I get the decals on I will complete the assembly and send you final photo's.


 The "Darling" is now complete.   3/21/2004



Building the Engine

 I decided to go with a 1/8" one piece solid steel crank. Finished it and the Muffler last night. Decided to gear down to 00-90 bolts for this engine. The "Darling" should be a read nice looker and with the new valve system design should be a very nice slow runner. I ordered the 64 pitch valve gears last night. This ,is if nothing else, is going to be a really fun project for details.


Started the crank case body tonight and finished lapping the crank shaft to a nice snug fit to the bearings. Finished up the crankcase side plates as well.


am officially calling the base casting done. It had such a nice flat surface in the front so I decided it was begging for a Serial # Plate.
  I went ahead and replaced the Valve Cam with a double lob Cam, so the exhaust beat will match the valve movement.
 I'm still working the bugs out of the valve rod lifter arm. If I don't get it just right it will tend to move the rod front to back too much for my comfort.


3/6/2004, Well as for the "Darling". I was unable to be satisfied with any of the three Lifter Arms I designed. They all seemed to not have enough strait up and down movement to make me happy. So.... I did what I thought Max Maxum would do. I went with a more conventional lifter and an elaborate Bracket Casting.
 Anyway, I fabricated a two piece detailed casting replica and added mountings to the Crankcase. Now the lifter pops strait up and down the way I want it.



 3/7/2004,  I may have bit off more then I can chew on this one.  I enlarged the bore to .312 to ease up on connecting rod restrictions and allow the engine to breath a little better. This of coarse put a dent in my original plans! It left little room for error on the head bolts and forced me to go with 00-90 head bolts instead of 0-80.
 I made the cylinder liner form stainless steel, laped to .312. Turned out beautiful! after that I made the cylinder sleeve from brass. To hide the exhaust ports I decided to use an observation I had made sometime ago. When cutting thin wall brass tubing with a tubing cutter it tends to curl the cut inward and radius the cut end. I decided to use this to my advantage. The bottom of the false waterjacket has a nice radius to it, do to the tubing cutter. this added to the beauty and helps hide the open body of the water jacket where the exhaust will vent out the bottom.
  The air will pass thru a nice little fuel tank mount bracket that bolts to the side of the water jacket.
 Some time ago I bought a Dremel Diamond cut off wheel it's about 1 inch in dia. and .030 thick. I have been using it to cut my exhaust ports on my CO-2 engines between the cooling fins. It has worked out very well as it cuts brass like butter. I used this to cut the exhaust ports in the steel liner and brass sleeve. It cut the stainless steel as well as it cut the brass!. I decided to see what I could do with nothing more then the Diamond Cut off wheel. Hard to see in the photo's but on the side of the water jacket near the bottom is a .025 square head bolt / drain plug on a small boss. This was made 90% in one simple set up using only the cut off wheel. I turned a small piece of .093 brass rod to 1/16" spigot about 3/16" long and cut it off with about 1/8" of the .093 brass attached to the spigot. I chucked it up by the 1/16" spigot in my lathe chuck and mounted it on my turn table, mounted vertically and used the cut off wheel to cut it square, then under cut the square head and cut a .015 female radius around the top of the boss. It is officially the smallest detail part I have made to date.......but this engine has a long way to go yet!  I may use the cut off wheel to form the fuel line plumbing fittings and the cylinder drip oiler. Time will tell.
  I still have to solder the water jacket sleeve to the cylinder and smooth over the seam. Then I think I will seal the seam on the top of the head, between the steel liner and cylinder, with JB Weld and lap the surface flat. If I can get it good and flat the wax paper gasket should hold ok.....I Hope!

    I'm Down to the last few details to complete the "Darling".
The Oiler has been a real pain. The oiler it'self was no problem but the
Plumbing fittings , now that's a different story, LOL.
 The push rod is done and the lifter is all set. the fuel line and oiler plumbing
is all that is left to the engine. Then the skid and coil box. Once these are
done I will disassemble it and start paint prep.



 Fired up the "Darling" Tonight! Runs great with the exception of every 15 seconds or so it backfires and sounds like a Mouse Sneezing! I like it , it really sounds neat when it back fires. So far it runs perfectly at 38 PSI. It would probably run well at a lower PSI once it gets worked it. I ran it for 20 minutes and it was getting faster all the time. Also since the connecting rod is so small I used axle grease on it instead of oil. The grease adds some resistance to the engine, but in the long run I think it will preserve the rod and journal much better then oil.


 As you may have seem on the message board I posted a picture of the darling since the paint work started. I had an accident and tore the paint up pretty good on the hopper and lid. I had to strip the hopper lid down to bare metal and start over, but the hopper it self will have to remain as it would be far too much trouble to strip the entire engine back down and start over.  It was a shame, since the paint was flawless and the best I have ever done with a deep shine , high gloss finish.
  The way it goes I guess.



The last was the Fuel line, which I completed tonight. 7 must be a lucky number!
I bent 7 fuel lines, 6 of which I didn't like and they became scrap. I'm happy with the 7th!



Copyright 2004,  Florida Association of Model Engineers and engine builder as noted above, All rights reserved.