Duclos Odds 'N' Ends Engine

[olympic]

For those of you who remember this thread, I took the engine outside a couple of days ago (the rain has stopped and the temperature has moderated) and tried again. Still no luck.

I discovered that the intake valve spring was too weak to fully seat the valve, so I replaced it with a slightly stiffer one, and I then heard that signature snort of a hit and miss engine on the intake stroke, but the compression was still low and I got only the odd pop from the ignition spark.

Yesterday I removed the piston and found that the two rings (steel, I think, not CI) were installed with their gaps about 20 degrees apart. I changed that separation to 180 degrees and ran the engine with a drill for a while. I now seem to feel better compression, and will again try to run the engine when my spring chores give me time.

 

[a41capt]

The thing I love about model engine machinists is their desire to solve problems. I’m not sure what a non-critical thinker would do if faced with similar issues...

We are all standing by awaiting that first “POP” while you trouble shoot someone else’s miscalculations. There is nothing more satisfying than untangling a mystery and seeing (and hearing!) the fruits of your labor come to life!

John W

 

[CFLBob]

I've been looking at the prints and getting ready to start building one of these, but that intake valve is what's making me pause. I built a Webster for my first IC engine and while it ran a few times for a minute or two, I haven't been able to get it to run since about February. That valve and whether it's moving enough has been the center of all my issues. I told myself that my next engine needs a push rod and valve lifter on both valves. That would be a major design change.

Sorry to take up space, but I'm suspicious of that valve.

 

[a41capt]

I've been looking at the prints and getting ready to start building one of these, but that intake valve is what's making me pause. I built a Webster for my first IC engine and while it ran a few times for a minute or two, I haven't been able to get it to run since about February. That valve and whether it's moving enough has been the center of all my issues. I told myself that my next engine needs a push rod and valve lifter on both valves. That would be a major design change.

Sorry to take up space, but I'm suspicious of that valve.

That would take the Miss out of the Hit and Miss!

 

[CFLBob]

That would take the Miss out of the Hit and Miss!

In the words of Emily Litella, "Never mind."

I've only been able to look at a few engines, and I don't see any that use a push rod on the intake valve.

 

[a41capt]

That’d be an interesting twist on a hit and miss Bob. It’d take some doing, but I suppose some sort of dual bobbin/counterweight system could be employed that left the intake valve closed and the exhaust valve open during the coasting cycle and then opening the intake valve as the exhaust valve closes. Timing it would be very interesting indeed!

John W

 

[Chiptosser]

A hit and miss engine, is a draw through system. It only draws through the intake track what it needs. These engines use a vaporizer or mixer to supply the fuel and air. They are not self metering as far as adjusting the fuel to the amount of air flow. It needs the vacuum created by the action of piston movement unseating the valve and associated spring pressure. It's a fine balancing act. If you are controlling the valve actions , you would have a throttle governed engine, or throttler.