The M25

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metiz
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The M25

Post by metiz » Tue Jul 20, 2010 6:39 pm

This is an engine I've been working on. It's a Chinese, dual intakes and a couple mm over 1m. The expected thrust is just about 26 pounds.

It had its maiden testrun tonight - it'll be one I won't soon forget.... the engine mounting came undone and the engine went apeshit - Watch the carnage here!


Damage report:

1 burned through air hose
1 burned pair of pants
a slightly bruised ankle
ignition box ripped to pieces (ignition still works!)
the engine smashed into my air compressor offsetting the sparkplug by 45 degrees and buckling the endcap
Slightly deformed tailpipe (easily fixed)


So yeah quite the test :D

I couldn't acurately determine the thrust but just before Armageddon commenced I was looking at the thrust gage - between 12 and 13kg with 300 grams of test stand resistance. I will retest this thing as soon as possible to get some acurate readings. Oh yeah it was 30 degress celsius so this engine will blow even harder when it's cold :twisted:

When I complete the testing I'll release the plans.
Attachments
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PyroJoe
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Re: The M25

Post by PyroJoe » Tue Jul 20, 2010 9:20 pm

It's ALIVE!
and taking casualties at that.
Good to see you got her shut down in short order.
Last edited by PyroJoe on Tue Jul 20, 2010 9:50 pm, edited 1 time in total.

metiz
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Re: The M25

Post by metiz » Tue Jul 20, 2010 9:49 pm

I got to replace the sparkplug, my pants and the airhose but at least I've got it on film - made me chuckle :D
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parabellum
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Re: The M25

Post by parabellum » Tue Jul 20, 2010 10:01 pm

And she strikes back! Today’s lesson: don’t play with fire. :)

P.S. Very nice engine. (I do not have access to stainless steel) :(
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Mike Everman
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Re: The M25

Post by Mike Everman » Sat Jul 24, 2010 3:03 am

Nice, man, nice.
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Jutte
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Re: The M25

Post by Jutte » Mon Jul 26, 2010 9:22 am

Awesome...LOL !
Metiz - you're the inventor of the pulse jet powered skipping rope!
Almost a circular travelling pulse jet...woohoo !
Good to see that you're OK !

ace_fedde
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Re: The M25

Post by ace_fedde » Thu Aug 05, 2010 12:56 pm

metiz wrote:It had its maiden testrun tonight - it'll be one I won't soon forget.... the engine mounting came undone and the engine went apeshit - Watch the carnage here!
Haha ha,
Hahhaaahaha,
haha
haaaaahaaaahaaaa,
haha
uhh?

:( beh hehe beeeehh hehe,
Mama says "No more Pulse jet extravaganza with that dangerous type!!"
Beh hehe :(
Beeeeeeh hehehe
Your scepticism is fuel for my brain.

nickwilson
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Re: The M25

Post by nickwilson » Fri Aug 06, 2010 5:32 pm

Good job metiz! The big PJ is that the M40 with the three pice intake you wanted me to try. If so dose it help it out in any way thanks Nick Wilson

metiz
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Re: The M25

Post by metiz » Fri Aug 06, 2010 7:06 pm

Yes that's the M40 with the 3 piece intakes. The reason I asked you to use those 3 piece intakes instead of the 2 piece intakes is that they are guaranteed to work. I'm 99% certain the 2 piece intakes will do just as well but i have not tested this so I can't confirm the last 1%
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metiz
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Re: The M25

Post by metiz » Sat Aug 07, 2010 2:17 pm

I ran the engine again today. no unsuspected problems this time but the thrust was a bit dissapointing. I only got 24 pounds where in the the last test I got close to 27. I blame the propane tankt for not giving me enough pressure and the injectors as well

This engine is a real pain to start. I will have to rethink the injector position

Video: http://www.youtube.com/watch?v=ogOCHdECdN8
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Ghrey
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Re: The M25

Post by Ghrey » Sun Aug 08, 2010 8:53 am

We have lift off...

Seriously; it is nice to see a strong runner in the smaller size range. Nice work.
In the process of moving, from the glorified phone booth we had to the house we have.

No real time to work on jets, more space, no time.

Life still complicated.

metiz
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Re: The M25

Post by metiz » Mon Aug 09, 2010 8:00 pm

Hey Ghrey, thanks :)

Alrighty test 3. I got it pretty close to full throttle this time, not much more, if anything to gain

Final peak thrust is 26.4 pounds wich is pretty sweet. Sustained thrust is about 25.7 pounds

I'll prepare the plans tomorrow - and somebody had better build the fucker :lol:

video
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PyroJoe
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Re: The M25

Post by PyroJoe » Tue Aug 10, 2010 3:04 pm

Looks like a good one!

It seemed to maintain the high frequency, but lost amplitude as the throttle was reduced.

Not that it is good or bad, I just notice the same characteristics on engines I built with shortish rectifier lengths. They also tended to have that same start up mode with a pop-pop-pop- then go. A little longer rectfier lengths tend to fall into resonance a little easier and will stay locked in more strongly as the throttle is reduced. As a general recipe I began using 44% of the tail unexpanded.

What is your opinion on the low throttle side.

Looks like your hitting good on the high throttle side! That thing must be deafening :wink:

metiz
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Re: The M25

Post by metiz » Tue Aug 10, 2010 3:31 pm

Hey Joe

Throttle on these engines is limited, but not absent. Starting is easiest at fairly high throttle. After the engine heats up, the throttle is much more responsive and can tollerate lower settings. Longer rectifiers might alow for a lower minimum throttle but shorter, tuned ones alow for the same thrust in a smaller package.

I am very well aware of the length = thrust debate. Regardless of its truthfullness (my opinion on the matter is clear looking at this engine) I'll stick to short and powerfull for now.

*edit*

injector style is also very important. Rossco's don't throttle as well as different designs
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PyroJoe
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Re: The M25

Post by PyroJoe » Tue Aug 10, 2010 4:12 pm

No debates here,
just checking if certain characteristics are present.
Good job on a kick butt engine!

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