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From: irwin@uiucdcs.CS.UIUC.EDU
Newsgroups: net.aviation
Subject: Re: Pulsejets
Message-ID: <7900030@uiucdcs>
Date: Tue, 8-Oct-85 03:44:00 EDT
Article-I.D.: uiucdcs.7900030
Posted: Tue Oct  8 03:44:00 1985
Date-Received: Sat, 12-Oct-85 13:57:05 EDT
References: <3024@mhuxd.UUCP>
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Nf-ID: #R:mhuxd.UUCP:-302400:uiucdcs:7900030:000:1236
Nf-From: uiucdcs.CS.UIUC.EDU!irwin    Oct  8 02:44:00 1985


>"which contradicts what's been said here about starting them on the
> ground at zero speed (in models)."

I do not see a contradiction here, the man said you started them with
a tire pump, and he is correct. There was a metal "valve stem" like a
tire has, mounted on the top front. You connected the pump and then pumped
like he**. The combustion chamber had the "reed valve" for air inlet
in the front, much like the little Cox model engines. Slots in a steel
plate, with reeds behind that bend back and allow air to pass, but will
close with pressure behind, forcing the reed against the slot. The chamber
had a reduced diameter at the rear, ahead of the tail pipe, which formed
a venturi, so you had a pressure chamber where the combustion took place.

The venturi provided the compression, the tire pump provided it during
starting, pump faster than could escape through the venturi. After it
had started, combustion would force the hot gasses through the venturi
and those leaving the tail pipe would cause a negative pressure (vacuum)
in the chamber, so the reeds would open as new air rushed in to fill the
low pressure area. Really wasn't much to it, seems that I remember them
costing somewhere around $140 mid 1940s dollars.