Bog's Paddleduck Engine

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bogstandard:
Kirk,

There is definitely something not square.

The whole engine is built along a common centreline, so the centre of the cylinder head cap is on the same centre as crank. So it should turn equally as easily in both directions.

The only thing that isn't centre line dependent are the four bars that the crossheads run up and down on. That should be your first search area. Slacken them all off, or even take them out altogether, and see if you have the same friction in both directions then. If it still binds on one side, then it isn't the crosshead or bars that are causing the problems. Do not run the engine without the crosshead fully built up, it is that which prevents wear on your bottom cylinder bearing and gland.

John

shred:
Also check your packnuts on the cylinders and valves. They gave me no end of friction trouble since I got the threads a little off-axis-- if yours get tighter and looser as you turn them around the rod, they may have the same problem.

ozzie46:
Shred

How did you correct the problem of the packing nuts? I'm building this engine too.

Ron

shred:

--- Quote from: ozzie46 on July 11, 2009, 08:31:56 AM --- Shred

How did you correct the problem of the packing nuts? I'm building this engine too.

Ron

--- End quote ---
At the moment, careful tuning. I put them about where they're supposed to be, then rotate them and the matching rod until they both run free. Then a dab of loctite or superglue onto the threads to hold the packnut in place (if not, they gradually tighten themselves to the point of binding). I considered redoing them a couple different ways. Since I've been playing with O-rings a lot lately, were I to redo them, I'd try a Kozo-style O-ring gland (I have his book that discusses them, I have no idea if the design is original to him, likely not given how things are in this business); basically it looks like the packnuts on this engine except not threaded and there's an o-ring seat where the packing goes. A sideways set-screw holds the 'packnut' in place (it must fit well in the o-ring bore)

Since I just went through and re-turned my engine the other night, here's how I went about it-- Starting with an assembled engine that doesn't want to run, even if timed correctly (check this! I messed it up for days of frustration)

1 - Separate the top and bottom halves. Pull the piston and valve pins and undo the tops of the columns. Now you have the crank half separate from the block half .
2 - While you are separating, check the con-rods and eccentric joints are free-- I found that bead-blasting peened one enough to rub. Fix those.
3 - Make sure the crank and bits turn free (dangle it upside down or whatever to keep the con rods and eccentrics from crashing into things). The crank must be smooth and free-running, no binding, or rough spots. Often a little bit of bar protrudes or a crank web or con-rod rubs on something else. Fix all of that, then set the cranks and timing on the bottom end and set it aside.

4 - Now address the top. Without mucking with it (you took it off an engine you thought would run, right?), pull and push the various rods. Run them to the full extent of their travels-- take note of any drag, friction, binding and rough spots. Drag going from one direction to the other at the ends of the travels is a bigger problem than a little running friction between the end points and often indicates an alignment issue.
5 - Starting one at a time, with one moving part (one valve or one piston), fiddle with the adjustments. Bogs left a ton of adjustments in this thing. So many sometimes it's hard to know what to fiddle with. Loosen everything up-- gland bolts, packnut (undo it completely), crossheads, etc and make sure the main bit moves correctly and smoothly. If not, fix it. Then start tightening stuff back up, starting with the gland bolts, then the packnuts, then the crossheads checking all along the way, both ends of travel, fixing the problems that come up.

6 - If there are alignment problems, you may have to drill some holes a little larger to get more wiggle room. If something is way out of wack, you'll probably need to redo it. One adjustment to play with as well is the main block baseplate. That has wiggle room and alignment for the crossheads as well. Pull the glands and pistons all the way out, then put them partway back onto the crossheads, so the piston is just out of the cylinder-- do the pistons line up with the bore? If not, tweak the baseplate over a bit so they do.

7 - Fiddle with the crossheads and get the pistons running as smoothly as possible.

8 - Recheck and reassemble. Time the valve spools and apply air. If your valve spools only run free in one orientation, you'll have to be careful when setting the timing-- set it by screwing the joint, not by rotating the spool.

Hope this helps
- Roy

Brass_Machine:
Kirk,

1st, what a nice job you have been doing on this build. I think I speak for everyone, we are very grateful you are doing a build log! :smart:

2nd, between what you have learned and the great advice you have gotten from our members you will have it running like a top in no time. :dremel:

:clap:

Eric

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