Slotted cylinder sealing

I was reading an article in Invention & Technology
on the navy's steam driven catapults and got to
wondering how they sealed the slot in the cylinder.
Google turned up lots of pages but nothing on sealing.
I'm envisioning that the piston/traveler pulls a ribbon
off a spool(like a tape measure) which seals as it
goes. but this has got to be a reliability and maintenance
nightmare.
Anybody know how do they do it?
Art
Reply to
Wood Butcher
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WHAT slot?
Richard
Reply to
cavelamb
I don't know anything about the steam catapult cylinders, but what you've described is close to how band type rodless pneumatic cylinders work. The sealing band doesn't roll up, it goes thru a passage in the piston as the piston moves. This is the best cross section I could find. Note that the inner band is the pressure seal, the outer keeps the guts clean.
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They do look like a maintenance headache, but are actually more reliable than you might expect, at least operating on air.
Ned Simmons
Reply to
Ned Simmons
Not positive, but I would expect that the cylinders are longer than the shot and the portion that attaches to the aircraft is on the piston rod, rather than having the piston travel directly and have to deal with a slot to seal.
Cheers Trevor jones
Reply to
Trevor Jones
That's sure a lot simpler than what I thought of. There has to be some ex-navy experts here who know. right?
Art
Reply to
Wood Butcher
The cylinder *is* slotted and there is no piston rod. They posted the full article on their website
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half way down is a cheezy diagram.
Art
Reply to
Wood Butcher
What ever it is doesn't seal very well. If you've ever seen a shot of them launching you can see all the steam coming out of the slot.
Reply to
Wayne Cook
There are actually 2 cylinders. They are side by side with a bridge connecting the pistons. The bottom side is blocked off with bolted on plates that bridge below the piston link. The top side is "sealed" with a three layer interlocking "felt type" material. The shooter get the aircraft load and sets the cat launch pressure, the cat officer verifies that the shoe and towlink are properly hooked. They then look at the pilot who checks the aircraft gauges and such and signals go/nogo by saluting the cat officer. after that salute the cat officer assumes the position you see in many shots. Basically hug the deck and hold on. The shooter then hits the release button. This shoots high pressure steam into the cylinders and behind the seal strips. The cat launches the bird and hits the water brake at the end. Then the system is reset using a cable that runs under the shoe and pulls it back using a high speed winch. Then the process repeats. During the times when there are no aircraft being launched or the ship is in port the cat rails are sealed from the elements with a set of strip seals. They are removed prior to launch activity.
The cat is actually much simpler than the arresting wires when it comes to operation and maintenance. Those cables and drums are a PAIN to work on.
Reply to
Steve W.
...
Also see
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more steam catapult pictures and description.
Or
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or its link
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planned electromagnetic aircraft launching systems. -jiw
Reply to
James Waldby
I can't picture what you're trying to describe. Got a link?
I did find this patent
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seconds Ned Simmons' response, but don't know if it ever was implemented
Art
Reply to
Wood Butcher
It uses a sealing strip that spreads open and closesas the piston moves by. There are two pistons side by side and the connector between the two also connects to the shuttle.
Reply to
Paul Thompson

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