The backside cannot be 100 percent full of oil with the cylinder extended. There was not enough oil in the front of the cylinder to begin with to fill that void. The rod end holds less oil because of the space the rod takes up in the bore. You're ignoring my simple example. Take a double acting cylinder. Take the piston out and throw it away. Insert the rod halfway into the cylinder. Fill the cylinder completely with oil and cap both ports. There's no piston at all, so that's a big seal leak. You can't move the rod in or out. You can't push it in because there's no place for the displaced oil to go. You can't pull it out because there's no oil to fill the void it leaves when coming out. It's hydraulically locked. Having a piston on the rod makes no difference. The only way a capped cylinder can move is to introduce more air or oil into it as it extends. It's simple, basic physics. I don't make the laws.
Take a cylinder with the piston centered and fill both ends with oil. Run an oil filled hose between the 2 ports. It still cannot move because of the displacement difference on each side of the piston.
Well I thought I understood basic physics but maybe I don't. Physics can be unintuitive at times and it wouldn't be the first time I was fooled by a force problem. Just for clarifiication when I said the backside was 100% full of oil I was talking about the partially extended state after the bucket has been disconnected. At that point the backside volume is equal to the sum of the front and backside volumes at the start of the test. We are both in agreement - it grows faster then a the front side decreases as the rod extends.
I am not trying to be argumentative just for the sake of being argumentative. Your volume explanation is quite compelling and you just about had me convinced which is why I went and did the test. But the cylinder did move with the ports plugged so what I am looking for is an explanation of that observed behavior. So far you haven't provided one that matches all of my observations. If I have introduced air into the backside of the piston why can I not compress that air by pushing the rod in?
TOH
This post was edited by TheOldHokie at 15:04:56 01/11/14 2 times.
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Today's Featured Article - Madison's County - by Anthony West. Philip Madison has been a good friend of mine for quite some time. He has patiently suffered my incessant chit chat on the subject of tractors for longer than I care to remember, and on many occasions he has put himself out, dropped what ever it was he was doing, to come and lend a hand cranking handles, or loading a find onto a trailer. Although he himself has never actually owned or restored a tractor, he was always enthusiastic and always around helping with other peoples projects.
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