Upshur's twin opposed cyl. engine

[Brian Rupnow]

Today I cut cylinder head fins and made up a couple of rocker arm support towers. Not terribly exciting, but it took up most of my day. There is something a little fishy about the bearing support tower in the drawing package from Upshur. Haven't quite figured out what it is yet, but there is something about the #5-40 threaded holes tapped in the rocker arm support towers and in the head.

[Jasonb]

I see two little fishies

1. The thread into the head is quite shallow so you need to make sure you avoid the spark plug thread and also don't overtighten things and strip the shallow thread.

2. If the rocker post is also threaded as shown you may find it hard to get things to line up

[GordonL]

Today I cut cylinder head fins and made up a couple of rocker arm support towers. Not terribly exciting, but it took up most of my day. There is something a little fishy about the bearing support tower in the drawing package from Upshur. Haven't quite figured out what it is yet, but there is something about the #5-40 threaded holes tapped in the rocker arm support towers and in the head.

See note #9 on the Upshur drawing. The rocker arm support is not drilled through. It is fastened with a threaded stem locktited in place.

[Jasonb]

Funny enough I suggested that over on HMEM, Would I had not seen the note

https://www.homemodelenginemachinist.com/threads/upshurs-opposed-twin-engine.36037/post-410481

Is that note on the original Upsure drawings as I  can't see it on the MEB ones? They also show it with a single cap head screw through the whole lot.

[Roger B]

I understand that many people have successfully built Upshur's engines but that does seem a somewhat dubious design with the spark plug recessed at the end of a small hole and the limited engagement of the rocker tower holding bolt. A stud and nut would be a better solution.

[Brian Rupnow]

Today I broke out my gear cutting stuff, and made gears for the Upshur. These gears actually fit inside the crankcase, but I stuck them on the outside just to be sure that they meshed properly and to take the picture. I haven't had lunch yet and it's 3:52 here, so I'm up up and away to eat something!!!

[Art K]

Brian,
Maybe the twin is different, but my Upshur vertical single has a drilled hole. The post is square on top turned on the bottom. The head opposite the spark plug has a set screw to hold it in place
Art