Bog's Paddleduck Engine

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bogstandard:
Kirk,

By the sounds of it, as long as your spools were made to the measured dimensions shown in the article, your trouble just might be timing. Even if things are rather badly made, once the timing is something near, it should run.

When I did my very first runs, the timing was later found to be about 10 degs out, and even at that setting, it ran very well.

It can be a little tricky at first just how to figure it out, as Roy (Shred) found out, but once you can get the grasp of how the timing works, it becomes a lot easier.

John

shred:
If it 'kicks', but doesn't run, when turned by hand I'd say it's most likely timing. Especially if you have to rotate it quite a bit to get it to 'kick' again. That's exactly what mine does when the timing is out.

kvom:
After I found a 1/8" NPT x 3/16 hose barb that I could fasten with a hose clamp, I hooked up the engine to the air supply. Although my compressor is set at 125 PSI, my regulator will register a maximum of 45 psi, which I assume is a result of back pressure from the engine itself.

The engine didn't self-start, but when I manually set piston #2 just past TDC and turned on the air, the engine started up and ran for several seconds before stopping suddenly. I repeated this and got another couple of seconds. Since the first two tries, it hasn't repeated. If I do the same thing I get 3/4 of a revolution. Setting piston #1 just past TDC and apply air gets 1/2 of a revolution.

At the point of stoppage there does seem to be more friction (i.e., resistance to turning the crank by hand), but I don't know if it's friction/binding that's stopping it or something else.

A few questions come to mind:

1) Should this engine run on only one cylinder? If so, I could tune one cylinder at a time by removing air supply to the other.

2) Does it sound as if it's the cylinder 1 timing is an issue? Visually, it still looks to me as if the eccentrics are at the top positions when the cranks are horizontal. How sensitive is the vertical setting of the valve? Would it make sense to adjust that before trying different timings of the eccentric (since I have no real idea which way to adjust them)?

3) Does it make sense to try to run in the engine some with the drill at this point?

bogstandard:
DO NOT TURN THE ENGINE OVER BY ANYTHING OTHER THAN HAND OR AIR UNTIL YOU HAVE IT TIMED IN CORRECTLY

If it isn't in correct time, there will be internal pressures built up that are liable to destroy your engine by bending shafts and knocking the crap out of bearing surfaces.

There is only one way you can go, and that is to sit down, study the instructions and the engine, and time it in. It might be a frustrating time for you, but that is the only way to do it. It might take a dozen goes before you get it spot on, but it will be worth it in the end.

John

shred:
A few full rotations is great progress! When mine runs-and-then-stops, what's happened is something (typically the valve spools, but sometimes the crank parts or packnuts or joint pins or crosshead rods or whatever) has moved, rotated, or come loose and either thrown it out of time and/or caused binding. Check on your crosshead rods, valve and crank timing to be sure they're still where you left them.

I don't think perfect timing is critical-- mine is 'sort of' timed at the moment and works ok, but it's got to be close.

You probably don't want to be putting 125 PSI straight into it. I'd start about 60 and lower it as soon as it gets going. A little oil in the airline is good to keep the pistons and valves happy.

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