Rocker issues...

[lazylathe]

Hi All,

Being my very first build i thought it would have some issues, and it does!

It will run very nicely with air pressure over the flywheel.
It spins freely and does not bind anywhere during the cycle by spinning the flywheel.

When i blow or use higher air pressure it stalls on the downward stroke.
I have tried placing the piston in varying positions but none seem to help.

It did run for a few minutes under breath power but i have not been able to replicate it again.

Any ideas or help would be greatly appreciated!

Andrew

 

[Jadecy]

Sounds like a port timing issue or not enough mass in the flywheel. Did you have plans for this or is this your own design? I would re-check the port holes and the offset of the crank pin.

 

[b.lindsey]

Andrew,
It sounds as if the piston is becomming too vertical on the downstroke and beginning to seal against the cylinder wall enough to cause back pressure, especially at higher pressures. I would check the vertical height of the crankdisk center above the centerline of the cylinder first, then the crankpin throw. Keep us posted on what you find.

Bill

 

[rleete]

Someone in the early stages of this epidemic had problems gettting it to run except upside down.
I don't remember what the solution was, but it was deceptively simple.

Anyway, I've found that the more I run mine, the easier it gets. This one apparently likes to have quite a loose fit on the piston. It also won't run at anything above about 20 PSI. The flywheel doesn't have enough mass to overcome the pressure on the return stroke. Low pressure (1-5 PSI) should be all you need to get it to tick over quite nicely.

I suggest spinning it over by hand or using a drill with some light oil in the bore. After a minute or so, take it apart and clean it up (alcohol works well), then reassemble it dry. That short run-in may be all it needs to free it up.

One last thought: this one only runs in one direction. Make sure you aren't trying to get it to run backwards.

 

[lazylathe]

Excuse my ignorance but...HUH???

It was built from plans and i remeasured everything and it is all to what the plans said.
The only thing i found is that i did not bevel the edges of the piston a lot, i just water papered them to get rid of the sharp corner.
All the materials are according to the plans.
The holes in the flywheel are the correct size as per the plans.

"I would check the vertical height of the crankdisk center above the centerline of the cylinder first, then the crankpin throw"
Can this be translated into english for the novice??
What should the measurements be?

Perhaps a "Secret Formula" ???
:wall:

It spins very freely when i spin the flywheel and goes for a few seconds under it's own power... scratch.gif

Think it may be a better idea just to build another one and see how that goes!
:-\

 

[b.lindsey]

Andrew, I wasn't trying to be cryptic at all, sorry if it came across that way. If all the measurements are to the plans then neither of my suggestions applies. I would think that if it turns over freely then the beveling on the piston is fine...otherwise it would bind. The only other thing I can think of is the size of the air inlet hole...I don't recall if the plans specify that or not. As i recall i used 1/8 dia brass with a 1/16 hole.

Bill

 

[rleete]

You're porbably trying to get it to run on too high a pressure. It will only start at the lower PSI. After it's going, you can crank it up - it really screams along at 15-20 PSI - but to start it, you have to be down less than 5 or 6.

 

[arnoldb]

Andrew, you can try the following:

Like rleete said, try starting it up from a lower pressure - try a couple of different pressures or slowly increase pressure while trying to start it.

Did you use any oil on it? - One of my rockers insists on being totally oil-free to run. The other one only started up after I gave it oil; not thin oil, but thicker multigrade motor oil - some in the cylinder, and some on the main shaft and on the crank pin as well - runs like a charm with this.

There's actually not much you can change on the rocking engine once built - but do check that the crank pin is nice and square to the crank disk.

Good luck

Kind regards, Arnold