Joey how many of these engines do you currently run??  And the one with the large intake looks interesting

Robert

Some other worm burners...   

Joey
In your top picture the top two and the bottom one appear to be necked down just after the burner can and at the start of the tail pipe.  Why, or is this an optical illusion?
Clancy

Hey loey where you get that 66% from . Last I checked that remaines a mystery if there is a charge of air after exhaust.  JB

Joey and Bill,

Flow into the tailpipe of pulsejets has been mapped for a long time.  Static tests show lots of flow up the pipe, depending on shape of the pipe end.  Static thrust is improved by a big bellmouth which boosts inflow (called "augmentation" in the aero texts which deal with pulsejets- most were written beforte 1955).  As the engine accellerates, flow up the tailpipe decreases until (depending on a lot of things) at about 200-250MPH inflow goes to zero.  The Schmidt/Argus engine in the V-1 cruise missile originally had a bellmouth at the exit, and was able to take off on its own in early tests.  Flight speed was slow- the trade-off to eliminate the bellmouth, and use a catapult to make up for loss of static thrust ( together with a couple of other speed secrets), increased speed by over 100MPH.

Bill, when you get to making pipes, try some with no flare and see what happens.  Static thrust will probably get pretty bad, but top speed may jump, like it did for the Germans.

Will