Have fun, Scott.
Some of those self build designs using plumbing bits don't look very inspiring and may need a certain amount of experiment is your drive head is low or the delivery head is low in relation to the drive, but even so Rams are not very critical and as long as you keep the basics right it should work.
I assume that these are under identical heads, but if they are on different sites or with different conditions there may be reasons for the trouble.
If you have a drive head less than 3ft you may need to do some experimenting but I have got Rams to run at 18" drive head.
It is absolutely essential that the drive pipe is completely air tight and has no upward air traps ( even glove valves in the drive pipe can cause air locks). Most difficult to explain problems come down to drive pipe troubles.
Similarly as Scott said you must have and be able to maintain an air supply in the air vessel. You must also make sure that the air doesn't increase to the point where it displaces the water from the delivery valve. The delivery valve must also close completely for the thing to work. The recoil wave needed to open the waste valve is initiated by the closing of the delivery valve and any failure of that to seat will result in failure with waste valve closed.
Thoroughly check the drive pipe, check for air in the air vessel, check for absolute certainty of closure of the delivery valve and be certain that the delivery head is large in relation to the drive head. If it is less than 7 times you may have to mess with loading of the waste valve. To prove this point, block the outlet and see if it runs reliably.
Flux[ Parent ]
Darn, did not think of sucking air! Glad to hear you figured it out.
I can find no reference to a minimum head on the output other than it should be 1 foot higher than the input? If not higher than what do you need the pump for!
7x is considered the practical limit of input head to output head.
Design considerations on drive pipe diameter to length min / max (half way down page) http://www.clemson.edu/irrig/equip/ram.htm
How ram pump works for others: http://www.clemson.edu/irrig/equip/ram4.htm
Have fun, Scott.[ Parent ]
With non adjustable valves you may need 7:1 to keep it running at heads below 4ft drive.
Ratios of up to 20:1 are common and the limit is way over this at low efficiency.
Not sure where I got the 7x from, read about it some where. Remembered it as practical, like you said higher ratio are not efficient?-)
I researched it and see 20x and higher is possible! Very cool. Thanks.
1 foot higher on the output, why do anything less? http://www.clemson.edu/irrig/equip/ram.htm Paragraph labeled: Valve Operation Descriptions
The swing check valve (part 4 - also known as the impetus valve) can be adjusted to vary the length of stroke (please note that maximum flow and pressure head will be achieved with this valve positioned vertically, with the opening facing up). Turn the valve on the threads until the pin in the clapper hinge of the valve is in line with the pipe (instead of perpendicular to it). Then move the tee the valve is attached to slightly away from vertical, making sure the clapper hinge in the swing check is toward the top of the valve as you do this. The larger the angle from vertical, the shorter the stroke period (and the less potential pressure, since the water will not reach as high a velocity before shutting the valve). For maximum flow and pressure valve #4 should be in a vertical position (the outlet pointed straight up).
Therefore just over 1x is possible too! Does this agree with you?
If you can get down to 1ft above drive head it could be very useful in some applications. I have had only limited success working with drive heads below 18" but if you could get it reliably down to 1ft drive the ratio would then be 2:1 and that is possible with care.
The standing wave needed to reverse the flow in the drive pipe needs to come from doing work on the delivery side, it may be that using rather inappropriate delivery valves will provide this with lower ratios, so part of this success may also be related to the delivery valve chosen.
