German ER90 testing

Moderator: Mike Everman

Re: German ER90 testing

Postby nitro » Wed May 10, 2017 4:11 pm

After test running the ER 90 evan more ( I think its time in went on a plane) I can give some good hard facts.The new 3 reed set up in blue spring steel is Perfect.The Germans in WW2 called this Stacking.I got the idea from the RAD Valve company in USA .They used then on 2 stroke Dirt bikes.I built my own fuel injector to spray fuel 140 Deg into the backing plate & reeds.Fuel is 20% Diesel for its Lubricating property.It protects fuel pump & reeds.80% Gasoline fires up the jet fast & both are cheep.Starting is fast & reliable.The Standard reed valve backing plate is modified with grooves to cool & help respray fuel & slots to let air in yet only fuel goes back to cool & protect the reeds.The fire does not go through there as the fuel spray is to rich at this stage.The Face plate is soft aluminium and a chipped reed damages it so I cut out of the 10 thal Blue spring steel a base plate the same shape as the face plate.When you tighten the head on it cant move yet when diesel fuel splashes it it becomes a shock absorber for the large 10 thal reed.It works so well I dont get chipped reeds no more.The biggest reed always was bad for that before.After a 40 minute run static a Medium size reed snapped first.Last tests I ran it at 50% thrust for ages & had no hot reeds at all.The afterburner I add for fun but it only adds 1 -2 lbs and uses 180mls a minute to do it.It mixes with the air coming in from the tail end.Sounds & looks better also .Static thrust is all ways about 14 - 16 lbs .The leaf blower adds drag.About 1 lbs. Best thrust was 17 lbs with afterburner ,no blower and at sea level.
The large & Medium reed have holes in & this lets air in by opening the small 8 thal reed first only about 1mm at this stage.The medium reed opens next about 1mm then the big 10 thal reed opens next .all 3 open up wrapping around the backing plate.When air goes through the first 2 reeds it makes a strong vacuum & this holds them close until the air vacuum is so strong the big reed forces them to shut when it fully opens.That high speed air helped cool the reeds & protect them from each other.Putting the holes in the reeds got rid of extra weight not being used also.Win ,Win set up I think.The conic ring it had in for holding the flame works perfect as is.Other designs I tried failed.With no flame holder the running was very erratic.The design of this pj requires it to have one.As for the 2 reed set up in blue spring steel it would snap off the big reed 4 minutes on a run.The same reeds in Spring Stainless Steel ran 8 minutes before snapping & thrust about .5 - 1 lbs less than my final 3 reed blue spring steel design.I tried different intake head shapes also and all but for standard were a failure .I had found when new the first hot runs can bend the pipe as the front holding bolt cant stop rotation.New pipe should be annealed first but to get around this I use a hose clamp to hold the pipe in any degree position until its run a few times & settled in.On a plane in use with more air it may not happen.All drawing for my modified ER90 are on Facebook under Pulse Jet Engines.
nitro
 
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Joined: Thu Jun 03, 2010 3:49 am

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