Another Rupnow Air Hit n Miss Engine

[bmac2]

So no chips just burn up the electrons in the old CAD. To my very limited experience this should/could work. I think it might be more to scale with the rest of the engine and I could run the airline out the back.

 

[bmac2]

Looks like I’ve got a decent stash of 1 1/4 cold rolled so a quick trip out to the garage to cut off the blank for the head. Cold out there, the 4x6 didn’t sound happy with me. Cleaned up both ends of the blank and got it to the right size in the lathe

 

[bmac2]

Pin pointed off the edge to establish a 0,0 reference for the iGaging DRO’s. I know, these things are not perfect but they beat the crap out of the ½ turn of slack I get out of the hand wheels on my Mini Mill and I did the X and Y axis for under $100.00

 

[bmac2]

Was going to have the bracket as a bolt on but thought if I made it part of the head with a small (.10) shoulder I would have a good vertical reference. Roughed out bracket and milled the 1/8 slot for the rocker arm then spotted the locations for the bolt holes

 

[bmac2]

With the head drilled and counter sunk I used it as a drilling jig for the cylinder.

 

[bmac2]

Used that nice .10 shoulder to help set the head up vertically for drilling and as I still had the 1/8 in mill in I spot the center for the ¼ hole for the valves.

 

[bmac2]

Bob’s tip of the day. Ok you experienced guys can skip on to the next part. This is for us rookies. I’m paranoid after drilling a nice hole on the table on my drill press while step drilling. I’d set the depth stop but didn’t take into account that as I went up in drill size they get longer. So with the set up for this piece I know I have 1 ¼ inches of material set 1/2 inch (tool blank) off the bottom of my vice for a total of 1 3/4 inches. I set the bit so it’s just above the work piece and used a 1 3/8 parallel to set the depth stop on the mill. Repeat with all the bits and I have a nicely reamed ¼ in hole in the head and no damage to my vise.

 

[bmac2]

Milled a 3/8 in flat top and bottom of the head for the intake and exhaust, drilled and tapped the 4 holes and it's done. I think with that shoulder it me longer to type this than it did to make the head.

 

[bmac2]

If you are looking for small taps I can’t say enough about these Sowa spiral taps. I’ve only broken 1 and that was because I was stupid and trying to use it free hand in some gummy brass. Nothing is more reassuring than seeing long (relative to a 2-56 tap) curly shaving coming up out of the hole.

 

[cfellows]

Bob, the drawing you have in response #21 should work OK. The other drawing you showed was mine, but I'm not the originator of that valve actuating mechanism. I first saw that design in the 5 cylinder radial engine, the Liney Halo. I used it on this engine:

http://www.homemodelenginemachinist.com/f43/anzani-3-cylinder-radial-compressed-air-13574/

But I later changed it to a rotary tube valve arrangement.

Chuck

 

[bmac2]

Hi Chuck. Glad to see you’re vertical again and thanks for the encouragement.
Thank you Mr. Liney Halo. Hope I don’t mess up your design.
I’m way more comfortable working directly from plans than winging it on my own. Let Captain Kirk go where no man has gone before I like drawings. Your “Inverted Compressed Air Hit n Miss” sounds great. To my uneducated eye the governor arrangement looks a lot more like what I’ve seen on “real” (if that’s right word) engines. One of these days I’m going to have to man up and give gear cutting a go.

 

[bmac2]

The valve seat is just 1/4“brass ¼” long. I haven’t a clue if the angle would matter a lot so I just used a ¼” center drill as I find they drill clean with a not bad finish.

 

[bmac2]

The ball for the valve is .184 stainless steel salvaged from a small pump type hand sanitizer.
http://www.homemodelenginemachinist.com/f25/free-stuff-21757/

 

[bmac2]

With the valve seat krazy glued down and the ball hot glued to a specific rod (the rod has to be long enough to hold, be stiff enough, and most importantly be within reach without having to get off my chair) I honed it in.

 

[bmac2]

Aaaa.:wall: The pin I want to use for the valve rod (?) is hardened stainless steel out of an old hard drive measuring .0377. I’d milled a 1/8 hole .10 down in the center of the head to reduce the amount of steel I need to drill through with that little #62 drill bit. Unfortunately the hole doesn’t go in the center but worked out to be just south of that. The 2 holes don’t overlap (barely) so I just filled in the hole with some JB weld. I think it will be ok

 

[bmac2]

When I tested the seal I couldn’t hear any leaking from the ball but it was leaking around intake manifold. Used some copper tape to make a gasket under it and can’t hear any air escaping with 10lbs on the intake.

 

[bmac2]

The internal parts done it’s time to set it aside and start on the flywheels.
I hate flywheels.

 

[bmac2]

Chilly In the Garage. I’ll have to let the old 4x6 free run for a while to warm things up.

 

[bmac2]

Back in the warm basement, the blanks for the outer rims have been cleaned up.

 

[bmac2]

Going to try for a spoked flywheel using aluminum. It’s just over 8th of an inch thick but I can’t see where thickness is critical. Krazy glued and bolted the 2 blanks tougher and took the outside dimension down to size then bored the ¾” hole in the center. The copper strips are to protect the aluminum from the jaws.