Vertical hit and miss engine

[Brian Rupnow]

Thanks guys. It's good to know that people are looking.---Brian

[crueby]

 

[Brian Rupnow]

The crankcase vent doesn't look all that impressive, but it's made and installed. At the last minute before I started to machine anything, I realized that I could use a 3/8" bolt for the main body. The head size was correct and I could thread it right up to the underside of the head and then cut it to length. I did that, but drilled out the center to 1/4" and threaded the end of a brass rod both externally and internally, then loctited it into the bolt. The knurled screw on cap ended up being made from cold rolled steel, because I have lots of that. I won't know how well this is going to work until I get the engine running. I can vary the spring pressure on the ball by tightening or loosening the set screw that the end of the spring fits into.

[Brian Rupnow]

The gas tank plumbing is finished, and with that I'm going to ride off into the sunset. There is nothing left to do until my gears and piston rings come in. Will post some more after I get all the bits and pieces.

[crueby]

Very nice looking engine!
Have you ever done any gear cutting for your models? Not very hard to do, very satisfying results.

[Brian Rupnow]

Chris--I always cut my own spur gears. I have a full set of 24DP cutters, a total of eight I  think. I did make one set of mitre gears just to see if I could, but they were equal sized with 1:1 ratio.

[Brian Rupnow]

Today we're not machining anything much. I have been thinking about engine oil levels and a dipstick. This view, with some of the near side pieces hidden, shows the position of the crankshaft and con rod with piston at bottom dead center. I'm thinking that the oil level should be such that it comes up to the centerline of the big end of the conrod and not any higher, when the engine is "at rest" with crankshaft in the position shown. If anyone has a different idea for oil level, please let me know.  Secondly, there is nowhere inside the crankcase for a dipstick. The entire cavity is filled with crankshaft and con rod as the crankshaft travels thru 360 degrees. I have the beginning of an idea---Right now the oil drain plug is a solid piece of steel screwed into the bottom of the crank case. If I ran a pipe horizontally from the oil drain plug, then a 90 degree elbow "up", and then a short piece of vertical pipe, the oil level in that short vertical pipe would be the same as the oil level in the engine when the engine was not running. This would let me have a screw on cap that would be air tight. On the outboard end of the screw on cap, I would solder a dipstick. I want the crankcase to be sealed so the vacuum fitting can do it's job properly and maintain a semi vacuum in the crankcase. I don't want a separate dipstick which would surely get lost. Making the screw on cap and the dipstick one piece seems like a good plan to me, but I'm open for suggestions. What do you think? (This picture does not show what I am talking about re: dipstick.) It shows the engine in it's current state with only a screw in plug in the bottom of the crank case.

[Jasonb]

You could just tap a hole at oil level in the front or back plate and fill until that overflows, screw in plug to seal it much like the Bobcat.

Or why not have two fittings with a bit of clear acrylic tube between them so you have a visual oil level much like the sight glass used on steam engine boilers.

I'd probably go with a lower oil level maybe bottom of crank pin, the conrod will still sling it around the crankcase.

[Brian Rupnow]

Jason--I like your idea. It is simple and gets the job done. A 5/16" shcs with a fibre washer will work just fine. Thank you.---Brian

[gbritnell]

Brian,
By all means don't fill the oil to the centerline of the rod. The oil level only needs to be high enough to have the rod drag through it. Most small engines (commercial splash oiled) have a tang off of the rod end cap that dips into the oil. It doesn't take much to get oil thrown about inside the engine. If you fill it too much the rod will be slapping into the oil and throwing large amounts of oil inside the crankcase.
gbritnell

[Brian Rupnow]

Thanks George. I do want a bit of splash to oil the wrist pin, but not enough that it affects the running of the engine.--Brian

[Brian Rupnow]

Position of tapped hole in sideplate that will determine oil level in engine.

[Art K]

Brian,
I had lots of problems with my Upshur engine mainly due to bad crankcase ventilation and to much oil. I have a second of those little squirt bellows like I use for gas and with oil I use one and a half of the sections. It is just about where the rod dips into the oil. By the way we had a great time while we were in Canada and enjoyed the visit with you.
Art

[Ian S C]

Some small motors have an oil slinger, a finger on the bottom of the big end bearing cap, this moves the oil around enough to go up the cylinder to lubricate the cylinder and small end, in fact some motors have a baffle to reduce the amout of oil going up the cylinder.
Ian S C

[Brian Rupnow]

Had a lovely visit from Art and his wife, from Madison, Wisconsin. Art brought along a couple of his engines and ran them for me, and we had a real "model engineers show and tell". I introduced Art to my office full of "shelf engines" and my newest work, the vertical hit and miss. A great time was had by all and I really enjoyed the visit from Art and his wife.---Brian