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Post by jetjeff on Oct 17, 2016 0:12:43 GMT -5
Hi All, Thanks John and Anders for the positive comments. I didn't try a run on liquid fuel this weekend, but I did move the fish scale out of harms way. I'm not sure if by adding the aluminum pulley, if that will alter the thrust reading of the scale. I did procure 5 gallons of E-85, may try that instead of Everclear 190. Jeff
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Adam
Veteran Member
Joined: May 2016
Posts: 101
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Post by Adam on Oct 18, 2016 20:16:44 GMT -5
Hi Jeff,
Awesome!! every time I check on your thread it gives me some inspiration to go and do some work on my project (still filing the diffuser). I bought an electronic scale a while ago to use for my future test bench. I was planning to mount it to the front of the engine slide with a cable attached to the bench toward the back of the engine, maybe this would eliminate the pulley. I noticed from your videos it looks like when you are trying to lite the gas the flame on lighter gets blown out easily, I had this problem with lighting my casting furnace, then I just used a blow torch with piezo ignition which worked instantly.
Looking really good! looking forward to some more videos.
Adam
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Adam
Veteran Member
Joined: May 2016
Posts: 101
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Post by Adam on Oct 18, 2016 21:10:41 GMT -5
Hi Jeff,
You got me wondering about the pulley so i did a quick experiment, with a 2 litre milk bottle of water hanging straight off the scale I get 2kg. With the scale upside down and the bottle suspended on a rope going through a small pulley I get ~1.4-1.5 kg.
Adam ...........45 min later
I just had a look in my old text book from engineering school. It says a single pulley is a simple machine because it changes the line of action of the input force but it does not however change the magnitude of the force since the effort equals the load. So now i'm confused, maybe there was something wrong with my experiment.
...........a bit later...It depends on the resistance/friction of the rope/cable going around the pulley. when I use a lawnmower wheel with ball bearings its only about 40 grams less.
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Post by jetjeff on Oct 18, 2016 23:44:18 GMT -5
Hi Adam,
Thanks for the info, yeah, I Google it and found out 1 pulley, according to Wikipedia, doesn't magnify the pulling effect.
I'm working on replacing the aquarium valve I was going to use to a brass valve, should to able to try a liquid fuel run by next weekend, barring 'other plans', my wife might have,,,lol. I also need to incorporate some filters into the tubing, as the hypodermic needles won't tolerate even a spec of debris.
Yeah, it seems the Schreckling engines, by nature of their low pressure ratio, but high throughput are sensitive to the start method. Compressed air is a no no on these engines. I've gotten the case pressure up to 2 PSI, I think if I can get it up to 3 PSI or a tad more, she will self sustain with no glowing of the the turbine.
Jeff
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Post by jetjeff on Oct 19, 2016 4:43:50 GMT -5
Hi Adam, While on the topic of your compressor diffusor build, make sure your cover plate is concentric to the diffusor. If you look at these pics, it's clear I didn't get the front cover plate concentric to the diffusor. It's probably the main reason why this engine didn't run. I'd suggest using Delrin or Nylon for the front cover plate. I can't guarantee your turbocharger wheel wouldn't suffer damage from coming in contact with plastic, but surely it would if it came into contact with aluminum. Jeff
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Adam
Veteran Member
Joined: May 2016
Posts: 101
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Post by Adam on Oct 19, 2016 5:04:16 GMT -5
Hi Jeff,
Thanks for the tip. Do you mean the compressor wheel wasn't exactly in the center of the cover? Yeah I wouldn't be too happy if it gouged into the aluminum cover, I'll have a look around for some nylon/delrin.
Adam
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Post by jetjeff on Oct 19, 2016 5:15:53 GMT -5
Hi Adam,
Yes, it's hard to tell from the pics, but in the 10-11 o'clock position the blades are touching, but at the 4-5 o'clock position, there is at least a .020" gap.
Thankfully my machining skills improved, they had no place to go but up,,,lol.
Jeff
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Chuks
Senior Member
Joined: August 2015
Posts: 498
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Post by Chuks on Oct 19, 2016 18:12:55 GMT -5
CONGRATS Jeff,
YOu are giving me more confidence as always.......
more vids.
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Post by jetjeff on Oct 19, 2016 19:56:24 GMT -5
Hi Chuksy, Thank you sir. Your work is pretty impressive from what I've seen, can't wait to see yours run too, congrats in advance Jeff
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Adam
Veteran Member
Joined: May 2016
Posts: 101
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Post by Adam on Oct 19, 2016 20:54:58 GMT -5
Hi Jeff, I see now. My compressor/ diffuser cover is made in two pieces so hopefully I won't run into that problem, as long as I get the diffuser cover centered properly it should be all good.
Adam
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Post by jetjeff on Oct 22, 2016 1:07:11 GMT -5
Hi John,
Kamps used case pressure to estimate RPM. One of his experimental engines that used an external combustion chamber had a rotor diameter of 76mm. He stated not to exceed .3 bar (4.35 PSI) as that corresponded to an RPM of 50,000. I'm asssuming rotor diameter affects case pressure. With that stated, what pressure should I call a halt to with my rotor diameter of 90mm for the compressor and 86.5 mm for the turbine, if I don't want to go much past 50k?
Kamps said not to exceed .7 bar (10 PSI) with his micro turbine, that was more likely in the 80k range, this figure was for a stainless turbine, he stated a cast Inconel wheel could go higher (1 bar or 14.5 PSI).
Thanks
Jeff
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Post by racket on Oct 22, 2016 2:41:06 GMT -5
Hi Jeff
RPM/tip speed limits will depend on the strength of the wheel/s , I wouldn't like to guess whats safe for yours not knowing their exact construction specs, even then it'd be too risky .
LOL, just keep well away from the plane of rotation once past a few psi of P2 .
Cheers John
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Post by jetjeff on Oct 22, 2016 3:06:10 GMT -5
Hi John,
Yeah, I'm trying my best, not to be the lead story on my local 5 o'clock news,,,lol. I'm guessing if the Swedish guy that made a Schreckling compressor out of 3D printed PLA plastic, that survived 40K, mine should be able to withstand that RPM too.
Kurt gives a rather ominous warning on page 56 of his book (in regards to the compressor build), 'Please don't try experimenting with different materials or thinner plywood - you have been warned!!'.
On a serious note, if anybody is considering replicating my compressor build from carbon fiber, you MUST vacuum bag or clamp the material in a mold to reduce the resin to fiber percentage. Simply using a squeegee to spread the resin is NOT the way to go. Carbon fiber (i.e. the cloth + resin), strength is totally dependent on the resin to cloth ratio, and with hand layup you will not remove enough resin. I've been working with carbon fiber for quite some time in DN iceboat construction, windsurfer construction, guitars, and model airplanes.
Jeff
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Post by jetjeff on Oct 24, 2016 2:46:04 GMT -5
Hi All,
I tried an E-85 run yesterday, sorry no video. The turbine seemed to spool up when the E-85 valve was opened, but the case pressure wasn't building like it did on propane so I shut her down. I think the burner can temp wasn't high enough for vaporization to occur. Plan B is to switch to Kero.
Regards
Jeff
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ripp
Veteran Member
I'm sorry, I don't speak english, so I torment you (and myself) with a translation program,Sorry
Joined: January 2013
Posts: 236
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Post by ripp on Oct 24, 2016 13:22:25 GMT -5
Hi Jeff, I think, the problem is, that you have changed the original design from the combustion chamber. www.glue-it.com/aircraft/general-information/glossary/j/jet%20engine%20combustion%20chamber.htmlA combustion chamber is a delicate part, so if you make a change, you have to know exactly what you are doing. Basically, it is best to have a good building instructions and follow it. It would be advantageous to use a KJ-66 combustion chamber adapted to the compressor wheel. FD3-64/Kamps-Turbine 1996 Cheers Ralph
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