- Joined
- Aug 25, 2007
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I'm considering this engine finished, although, like most of my engines, I will most likely always be tweaking and changing things a bit. For those of you who might think my engine mount resembles the lid of a crypt with a tombstone, my wife already pointed that out to me. Wasn't my intent, just turned out that way.
The curved bottom of the base was inspired by some of the excellent models made by Tom Hall. It is made from a 1.75 inch diameter steel pipe, split lengthwise into quarters. The ends were then mitred and all pieces welded together. Lots and lots of grinding and sanding got it to resemble a casting rather than being built up by welding. The top of the base is made from 1/4" cold finished steel, rounded on all edges and welded to the mitred frame. The upright is made from 3/8" thick aluminum angle. The base took me 3 full days to complete. Usually I just throw something together, but since my models spend a lot of static time being admired on the shelves of my study, I decided to make it "pretty".
One bit of serendipity is that this engine idles and runs kind of rough, missing a lick now and then and generally sounding like it needs a tuneup. I find this to be amazingly like many of the videos of old radial engines running on youtube. Almost sounds like it has a 3/4 cam in it. It's also kind of hard to start sometimes, kicking back and endangering my prop spinning finger. Not sure how I managed this bit of realism, but I'll take it!
In retrospect, the cam assembly, lifters, pushrods, rocker arms and valve assemblies added a huge amount of complexity to the build compared to the much simpler valving mechanism of my opposed 4. But, perhaps the visuals and the irregular running make it all worth it. Now if I could just get it to backfire occasionally...
This is my first video. I noticed later, after I had uploaded the video, that one of the pushrods was dislodged from the lifter, so the engine is only running on 2 cylinders.
[ame=http://www.youtube.com/watch?v=VbuiCROHeVY]http://www.youtube.com/watch?v=VbuiCROHeVY[/ame]
This is the second video, taken with a different camera and with the engine running on all three cylinders.
[ame=http://www.youtube.com/watch?v=bIYcx4-uyYE]http://www.youtube.com/watch?v=bIYcx4-uyYE[/ame]
As a recap, the engine has a bore and stroke of 5/8" x 5/8". It is 4 stroke in operation with each cylinder "firing" on every other revolution. The cam has 2 lobes 180 degrees apart and turns at 1/4 the RPM of crankshaft. Two sets of gears, each reducing the speed by 1/2, are positioned so that the cam sits on and is concentric to the crankshaft. The propeller is made of from a steel bar, 1" x 1/4" x about 10" long.
Chuck
The curved bottom of the base was inspired by some of the excellent models made by Tom Hall. It is made from a 1.75 inch diameter steel pipe, split lengthwise into quarters. The ends were then mitred and all pieces welded together. Lots and lots of grinding and sanding got it to resemble a casting rather than being built up by welding. The top of the base is made from 1/4" cold finished steel, rounded on all edges and welded to the mitred frame. The upright is made from 3/8" thick aluminum angle. The base took me 3 full days to complete. Usually I just throw something together, but since my models spend a lot of static time being admired on the shelves of my study, I decided to make it "pretty".
One bit of serendipity is that this engine idles and runs kind of rough, missing a lick now and then and generally sounding like it needs a tuneup. I find this to be amazingly like many of the videos of old radial engines running on youtube. Almost sounds like it has a 3/4 cam in it. It's also kind of hard to start sometimes, kicking back and endangering my prop spinning finger. Not sure how I managed this bit of realism, but I'll take it!
In retrospect, the cam assembly, lifters, pushrods, rocker arms and valve assemblies added a huge amount of complexity to the build compared to the much simpler valving mechanism of my opposed 4. But, perhaps the visuals and the irregular running make it all worth it. Now if I could just get it to backfire occasionally...
This is my first video. I noticed later, after I had uploaded the video, that one of the pushrods was dislodged from the lifter, so the engine is only running on 2 cylinders.
[ame=http://www.youtube.com/watch?v=VbuiCROHeVY]http://www.youtube.com/watch?v=VbuiCROHeVY[/ame]
This is the second video, taken with a different camera and with the engine running on all three cylinders.
[ame=http://www.youtube.com/watch?v=bIYcx4-uyYE]http://www.youtube.com/watch?v=bIYcx4-uyYE[/ame]
As a recap, the engine has a bore and stroke of 5/8" x 5/8". It is 4 stroke in operation with each cylinder "firing" on every other revolution. The cam has 2 lobes 180 degrees apart and turns at 1/4 the RPM of crankshaft. Two sets of gears, each reducing the speed by 1/2, are positioned so that the cam sits on and is concentric to the crankshaft. The propeller is made of from a steel bar, 1" x 1/4" x about 10" long.
Chuck
