Dear Cadman.

I'd like to take the opportunity to thank you on behalf of this community for your presentation.

Here in the UK we can add an approximate extra 1.7 Lbs to the weight for an Imperial Gallon. ( 4.54 L/Kg )

Cheers Graham.

Dear Cadman.

I'd like to take the opportunity to thank you on behalf of this community for your presentation.

Here in the UK we can add an approximate extra 1.7 Lbs to the weight for an Imperial Gallon. ( 4.54 L/Kg )

Cheers Graham.

Thank you for your kind words Graham. Of course it doesn’t matter which measurement system is used, it’s all the same force in the end.

I have one question regarding your idea. i understand the sequence of the upstroke(power stroke) but am having a little difficulty with the return downstroke, which relies on gravity. To function correctly both pistons and the connecting rod must have good seals with the cylinder walls and the rod gland. this means some type of o ring or u cup or even metal sealing rings, which in turn will impose considerabe drag or friction on the sliding parts. My question then, does gravity have enough pull to overcome the fiction of the sealing parts and weight of piston assembly and force needed to shift the bottom valve position? From my experience hydraulics and pneumatics require considerable spring force to return a piston to its starting point, on one way acting systems.
thanks!

Hello Vince,
Thanks for your interest. O-rings or metal piston rings are not needed and should not be used for the very reason you say. Besides, metal rings and PVC pipe do not work well together. A 20 lb assembly has plenty force if you are careful with clearances and keep things a little loose. This engine does not have high rod travel speed or high fluid pressures.
I use cup piston seals 3D printed with petg and have also used a flat rubber gasket material cut just slightly larger than the bore. Both work well. The cup should just touch the wall all around at the top edge with little compression. I lube the piston, rod, and seals with a moly grease when assembling. You will be surprised how easy it slides. Speaking of lube, the fluid is 50/50 water anti-freeze and I'm thinking about adding some powdered teflon to the fluid. I think the very best seals would be a leather cup soaked in the fluid prior to assembly. The rod seals I use are plain old buna-N u-cups but I have also used cut rubber sheet.
The snap action slide valve I designed takes about 6 lbs of force to shift and I’m not satisfied with that design yet.
The hydraulics and pneumatics you are used to have small diameter plumbing relative to the piston bore don’t they. You need large diameter plumbing with this engine to minimize flow restriction.

Regards
Cadman

Edit: piston seals are cup seals, not u-cup.

Hi Gyula,
That’s impossible to say at this point, I haven’t finished the 6”. I will be very happy if the piston speed of this 6” bore & stroke engine could average 6” per second. More likely it will be quite a bit less since I am currently limited to 1.5” ID plumbing. I can say this much, it all depends on the flow velocity you can achieve. Large diameter plumbing, fluid rotation while filling and discharging the cylinder, large radius bends, and high flow valves will be just as important as in a high performance ICE. Maybe more important.

If it matters, what I have built up until now is a mock up using 4” PVC pipe, garden hoses, hand operated valves (vise grips and wood blocks) and weights. Just enough to verify the concept is valid.  A 4” is too small for any kind of power. The 6” under construction is for experiments, testing and development.

What I want eventually is a 14” bore or 12” square, 3 to 6” stroke, 4” ID plumbing, 60 cycles per minute, 2 cylinder engine with a crankshaft and flywheel. 

Regards,
Cadman

A quick and dirty evaluation.

All the sixes, in Imperial measurements.

Six Feet head of water.    2.6 PSI

Six inch diameter piston. 28.27 square inches multiplied by 2.6 equals 73.5 Pounds pressure.

Six inch stroke. Volume of displaced fluid ( water ) 169.17 Cubic Inches. Mass 2.78 Kg or 6.116 Pounds.

Taking Cadman's value of 20 Pounds for the power piston and displacer piston assembly we then add the 6.116 Pounds ( working fluid to be returned ) giving 26.116 Pounds total.

By subtracting the 26.116 from the input pressure of 73.5 pounds we have a net gain of 47.4 Pounds
( 21.5 Kg ) losses excluded.

That's " my " take on Cadman's presentation. Mathematics isn't my best area of expertise so please feel free to contradict.

It's the clever use of the " displacer " piston to transfer the working fluid back to the header tank, my hat is off to you Cadman.

I can think of several means of reducing the losses like simple sliding gates for the control valves and having several vertical tubes through the displacer that can be covered by a thin Rubber flap at the top.

Thanks again Cadman.

Cheers Graham.

A quick and dirty evaluation.

All the sixes, in Imperial measurements.

Six Feet head of water.    2.6 PSI

Six inch diameter piston. 28.27 square inches multiplied by 2.6 equals 73.5 Pounds pressure.

Six inch stroke. Volume of displaced fluid ( water ) 169.17 Cubic Inches. Mass 2.78 Kg or 6.116 Pounds.

Taking Cadman's value of 20 Pounds for the power piston and displacer piston assembly we then add the 6.116 Pounds ( working fluid to be returned ) giving 26.116 Pounds total.

By subtracting the 26.116 from the input pressure of 73.5 pounds we have a net gain of 47.4 Pounds
( 21.5 Kg ) losses excluded.

That's " my " take on Cadman's presentation. Mathematics isn't my best area of expertise so please feel free to contradict.

It's the clever use of the " displacer " piston to transfer the working fluid back to the header tank, my hat is off to you Cadman.

I can think of several means of reducing the losses like simple sliding gates for the control valves and having several vertical tubes through the displacer that can be covered by a thin Rubber flap at the top.

Thanks again Cadman.

Cheers Graham.

Thanks Graham, and hats off to Archemedies and Pascal too.
In my calculations, I doubled the displaced weight at BDC, half for the displaced liquid above the pressure piston and half for the liquid above the displacer piston. You’re spot on about several vertical tubes. I am using four 0.75” tubes that almost exactly equals the area of my 1.5” plumbing, with a flat disk valve at the top.

https://web.archive.org/web/20070225160446/http://www.theverylastpageoftheinternet.com/
"MAIN MENUE": E. L. S. A. gravity mill

That isn’t the same thing but I wonder how often this has been thought of before now. I suspect this engine fits into the ‘forgotten technology’ category.

Cadman

Floor,

That was the purpose of the pdf. I really don’t know how much simpler I could explain it. Did you see the page I linked to at Kenyon?

Assuming you know how a hydraulic cylinder works? Look at it this way, the gland is a fixed divider that separates the upper and lower parts. The lower part is a hydraulic cylinder. The upper part works like an old fashioned well pump.

Cadman

Floor,

That was the purpose of the pdf. I really don’t know how much simpler I could explain it. Did you see the page I linked to at Kenyon?

Assuming you know how a hydraulic cylinder works? Look at it this way, the gland is a fixed divider that separates the upper and lower parts. The lower part is a hydraulic cylinder. The upper part works like an old fashioned well pump.

Cadman

Appearantly the PDF did not serve its purpose very well.  Simpler is not what I requested, but rather what I requested was explain it in steps and in detail, including the purpose for and the result of each event / motion.

Yes I viewed the links.  Assuming that I know how a hydraulic cylinder works, the actions of your device and why it is supposed to work are still not clear to me.

                                 floor