Roaring Becomes Elektra

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Bruno Ogorelec
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Post by Bruno Ogorelec » Tue Aug 03, 2004 1:16 pm

Steve, you look like the future president of Pratt & Whitney.

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Post by Anthony » Tue Aug 03, 2004 4:01 pm

I'll never fly in an airliner powered by P&W again then...

Hehe, just kidding. Would be cool to have pulsejet powered airliners, just imagine the noise inside the aircraft!
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Post by larry cottrill » Wed Aug 04, 2004 5:08 pm

steve wrote:If you can fix the mistakes then by all means do so! I'm interested to see how it turns out. I assume you won't be using MS paint for this one :-)
. . .
As for another electra, that will have to wait awhile. Right now I am in the middle of the Cross-country part of my flight training and at $250 a lesson I have NO money to spend on more engines. I'll start building more stuff when I go back to school and can use their supplies for free again.
Steve -

Don't forget to email me with your name [as you want it to appear] and mailing address. Also, don't forget that you can post any time you want to the web log -- so, even if you don't want to build another engine, go ahead and post there any time you do some more testing of the E1, or any time you have something useful to contribute!

Thanks again!

L Cottrill

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Re: Roaring Becomes Elektra

Post by steve » Thu Aug 19, 2004 1:57 am

ran the engine again today and got some great pics so here they are in all their hi-def glory!

you might notice how the injector is mounted way to far into the intake but it still runs so who cares! If nothing else this shows that the engine is pretty resistant to changes and mistakes like this.
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intake shot of elektra
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glowing elektra
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Re: Roaring Becomes Elektra

Post by Bruno Ogorelec » Thu Aug 19, 2004 6:27 am

I love those pictures! Great work, Steve and Larry. Please develop this as far as you can so that it can enter the history of pulsejet development properly, as a successful design in its own right. It is already 95 percent there.

How noisy is it?

Do the flat sides distort noticeably from pressure? Bill's 4-pipe Kentfield would push out the front plate into a dome shape rather quickly. In contrast, the flat sides of the Elektra don't seem to be affected at first glance. This is curious. An analysis and a detailed comparison of the two cases may tell us a lot.

I am really interested in this point because a lot of designs might benefit if they could incorporate flat surfaces. So far, the received wisdom (and Bill's experience) indicated that flat surfaces would be distorted but the flat pancake of Elektra seems to stay flat.

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Re: Roaring Becomes Elektra

Post by larry cottrill » Thu Aug 19, 2004 12:43 pm

brunoogorelec wrote:I love those pictures! Great work, Steve and Larry. Please develop this as far as you can so that it can enter the history of pulsejet development properly, as a successful design in its own right. It is already 95 percent there.

How noisy is it?

Do the flat sides distort noticeably from pressure? Bill's 4-pipe Kentfield would push out the front plate into a dome shape rather quickly. In contrast, the flat sides of the Elektra don't seem to be affected at first glance. This is curious. An analysis and a detailed comparison of the two cases may tell us a lot.

I am really interested in this point because a lot of designs might benefit if they could incorporate flat surfaces. So far, the received wisdom (and Bill's experience) indicated that flat surfaces would be distorted but the flat pancake of Elektra seems to stay flat.
How noisy is it? Plenty.

I have no doubt that the flats would eventually puff out a bit, if you actually ran the thing for several minutes. Remember that this is pretty thick steel, as pulsejet materials go, so it doesn't heat up very rapidly. Get them good and hot and I don't think they would stay perfectly flat for long. Of course, they are well constrained at the edge all around, and even to some degree by the engine mounts [on my prototype, not Steve's]. I think the real hot spot will always be the 'pinch zone' at both sides of the lower end of the intake tube.

If you use one of these as a Greasodyne cooker for individual chops or ground beef patties, a slight upward bulge would be nice, for natural drainage of the excess fat.

As far as development goes, I'm pretty confident that the Elektra II will be superior in almost every respect. You can see what it now looks like at
http://www.pulse-jets.com/phpbb2/viewtopic.php?t=856
way down on the Valveless forum directory.

L Cottrill

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Re: Roaring Becomes Elektra

Post by steve » Fri Aug 20, 2004 12:25 am

Larry Cottrill wrote: I have no doubt that the flats would eventually puff out a bit, if you actually ran the thing for several minutes. Remember that this is pretty thick steel, as pulsejet materials go, so it doesn't heat up very rapidly. Get them good and hot and I don't think they would stay perfectly flat for long. Of course, they are well constrained at the edge all around, and even to some degree by the engine mounts [on my prototype, not Steve's]. I think the real hot spot will always be the 'pinch zone' at both sides of the lower end of the intake tube.
I don't know about that larry because I did run it for several minutes (3 or 4) and it didn't appear to be getting any hotter then shown in the picture The sides didn't warp whatsoever, wait, let me go double check.... (walks away)

(comes back)... OK I checked it with a straight edge and there isn't even a hint of a curve. Maybe since the engine has a relatively high surface to volume ratio when compared to most engines it stays noticibly cooler and therefore dosn't get hot enough to allow the sides to flex(?)
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Re: Roaring Becomes Elektra

Post by Bruno Ogorelec » Fri Aug 20, 2004 5:29 am

steve wrote:Maybe since the engine has a relatively high surface to volume ratio when compared to most engines it stays noticibly cooler and therefore dosn't get hot enough to allow the sides to flex(?)
I don't think so. The high surface-to-volume ratio will also mean that it picks up more heat from the combustion process than other engines do.

Maybe what happens is that the swirl pattern iside the engine produces a stratified charge. If a vortex of rich mixture is enveloped in very lean mixture or in pure air, or in products of previous combustion, or a mixture of all three, only the central part with burn and the non-burning envelope will shield the walls from full heat transfer.

Some piston engines use this trick to reduce heat transfer. Maybe it just happened to take place in the Elektra.

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Re: Roaring Becomes Elektra

Post by Stephen H » Fri Aug 20, 2004 1:45 pm

FINALLY i got around to finish reading this thred, for some reason i lost it on about page 2... so congratulations larry and steve. very cool looking engine!!

Steve is your fuel supply just a tube going in at about 45 degrees into the intake? nothing fancy at the end of it ?...

Stephen

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Re: Roaring Becomes Elektra

Post by steve » Fri Aug 20, 2004 6:44 pm

Stephen H wrote:FINALLY i got around to finish reading this thred, for some reason i lost it on about page 2... so congratulations larry and steve. very cool looking engine!!

Steve is your fuel supply just a tube going in at about 45 degrees into the intake? nothing fancy at the end of it ?...

Stephen
It was at 45 degrees origionally but I made a really terrible weak weld to hold it in place so during the first test run it broke and the vibrations caused it to rotate to about 90 degrees while the engine was still running. this didn't effect the engine's performance in any noticible way so I re-attached it at 90 degrees (using my perfered method of drilling the hole too small and then hammering the tube in place. I got a little carried away with the hammering an that is why the injector sticks out so far into the intake. It would probably be easier to start if the tube was flush with the inner wall of the intake) I left the rather large hole from the first injector in place without any attempt to plug it up and mounted my new one slightly furthur down then the first one.(BTW I'm using steel brake line) It ran fine even with a big hole in the side of the intake! the more I play with this engine the more I realize that the only critical dimentions on the whole thing are the intake and exaust lengths. After all, these were the only dimentions I actually used. everything else I simply compared to larry's pictures and used TLAR.
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Re: Roaring Becomes Elektra

Post by Stephen H » Sat Aug 21, 2004 2:20 am

*cries*
just talked to my brother and found out they dont sell those electrical boxes in NZ. we have all plastic ones over here, and if we do have them he has never seen one. I might have found someone to teach me gas welding so i thought this would be a good project to work on. guess not!

Stephen

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Re: Roaring Becomes Elektra

Post by Bruno Ogorelec » Sat Aug 21, 2004 9:03 am

Stephen H wrote:*cries*
just talked to my brother and found out they dont sell those electrical boxes in NZ. we have all plastic ones over here, and if we do have them he has never seen one. I might have found someone to teach me gas welding so i thought this would be a good project to work on. guess not!
Stephen, I am sure that a similar-sized steel box of some other kind can be found -- may be a shallow drum or something. Don't give up. Doing a similar project with a slightly different chamber may in fact yield valuable new insights. I was thinking of a Danish cookie can (or 'tin' as the Brits would say) but the steel is too thin.

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Re: Roaring Becomes Elektra

Post by Stephen H » Sat Aug 21, 2004 9:21 am

so i would just need something steel with aprox the same volume ?... larry do you no the volume of the CC ??

Stephen

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Re: Roaring Becomes Elektra

Post by Bruno Ogorelec » Sat Aug 21, 2004 9:29 am

Stephen H wrote:so i would just need something steel with aprox the same volume ?... larry do you no the volume of the CC ??

Stephen
Roughly the same volume, but also at least roughly the same general shape, I think -- especially the average 'drum' diameter should probably be in the same ballpark. I could be wrong, but I think those parameters will be the ones that will determine how close you get to replicating the Elektra.

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Re: Roaring Becomes Elektra

Post by Stephen H » Sat Aug 21, 2004 9:38 am

also... what exactly was was the eletrical box for ??

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