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Post by madrocketscientist on Feb 10, 2018 17:51:06 GMT -5
Alain, I just remembered that silicon tends to dissolve with fuel, it might be best to talk to an O-ring supplier and see what they can come up with for the hot side? The fluid layer may be enough in itself to provide good damping? The small amount of toxins from a couple of o-rings in your turbine exhaust shouldn't be anything to worry about, crossing the street would be more dangerous for your lungs Shannon.
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dieselguy86
Veteran Member
Joined: September 2014
Posts: 186
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Post by dieselguy86 on Feb 10, 2018 20:44:47 GMT -5
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Post by madrocketscientist on Feb 11, 2018 6:33:36 GMT -5
I spent the afternoon getting my head around the Xicoy kerostart sequence in the manual. The way it was arranged meant that I found it really hard to sort out exactly how it worked. I rewrote that section of the instructions so its easier to understand what is happening during the start sequence and how to adjust things. I would upload the .pdf file here but the add attachments button isn't working for me. If anyone wants a PDF, PM me and I can send you the file. A couple of .jpegs instead EDIT: I made a few changes to the file in the images above to make things clearer.... Shannon.
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gtbph
Veteran Member
Joined: August 2013
Posts: 101
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Post by gtbph on Feb 11, 2018 12:32:50 GMT -5
Hi Shannon, OK, no silicone then! Yes, completely without O-rings could work too I think, but there could be more air bubbles and oil foam at the ends of the film. I'm not sure what I'll do, probably I'll make the ring grooves anyway, because they will not be a problem if no rings are used. I'll come back to this topic in my own build thread when that point is reached. Thanks for the interesting link, dieselguy86! Alain
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Post by madrocketscientist on Feb 19, 2018 4:48:10 GMT -5
My GTBA CD arrived today from the far side of the planet! From my quick look, its like a history of the development of the model jet engine!
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Post by racket on Feb 19, 2018 16:58:50 GMT -5
Hi Shannon
Yep , if it wasn't for the GTBA members doing all the R and D on RC micro turbines , they probably wouldn't exist , thats why the GTBA is a bit "touchy" about copyright , the world is full of people only too happy to use others hard work for their own financial gains ..............there are undoubtedly "lurkers" on this Site hoping to do just that, right now .
Enjoy the CD and its history lesson
Cheers John
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Post by madrocketscientist on Feb 19, 2018 17:57:40 GMT -5
John,
It does make me wonder how many of the manufacturers discretely signed up the GTBA... I do see it as a sword that cuts both ways, the availability of micro turbines wouldn't be what it is today without the manufacturers. Also those that have the technical skills and time to build their own turbines are definitely a minority.
Shannon
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Post by racket on Feb 19, 2018 18:27:36 GMT -5
Hi Shannon
The manufacturers have certainly made RC turbines available at very reasonable costs , especially in the smaller engine sizes , LOL, probably so cheap that its not worth building ones own to save money .
A number of manufacturers started off as just ordinary Members of GTBA but then turned a hobby into a business once it became a proposition to do so , and undoubtedly used the R and D of the numerous other Members who had been and still were experimenting away , it was an interesting time that has sadly passed as the RC micro reached its evolutionary end .
The resources at the GTBA have been a help to me over the years even though theres been a "scale" difference , its been a great "second opinion" to turn to .
Cheers John
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Post by madrocketscientist on Feb 19, 2018 18:42:08 GMT -5
John,
I get the impression that some of those on the GTBA also build turbines for the large engine manufacturers for commercial airlines and such, although commercial and legal sensitivities they wouldn't be so open about it. There is definitely a wealth of knowledge behind the development of the microturbines!
I see the hobby engines as having the advantage that for now it is still easier to work to closer tolerances on parts fits on the engines than the cheaper manufacturers, and gain a performance increase that way. CNC machines get cheaper all the time but when manufacturing for a profit, closer tolerances always cost more.. especially when you are grabbing any two parts off a shelf and need to make a working turbine. With care the hobbyist can make that extra close compressor clearance for example...
I have a few hobbies that I could make into a business, but that would take all the fun out of it... I just enjoy making things and learning something in the process!
Shannon.
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Post by racket on Feb 19, 2018 20:05:01 GMT -5
Hi Shannon
Yes , there are some very bright guys on GTBA who do indeed input into large stuff .
Close tolerances were the reason I went back to "brass" for my bearings , turbos are manufactured to the lowest cost possible , so theres reasonable manufacturers tolerances that I can achieve on my old machinery, and the assembly procedure doesn't take much finesse..........agricultural comes to mind :-)
Cheers John
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Post by madrocketscientist on Mar 9, 2018 5:04:04 GMT -5
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Post by racket on Mar 9, 2018 18:19:37 GMT -5
Hi Shannon
LOL.............once you start reading , you'll never stop ............theres always something new to learn .
I like that Paper by Casey and Rusch , I've used it to help with designs , especially for Anders 5:1 PR engine...............a lot of the performance turbochargers are configured to allow maximum airflow so that the horsepower output is the highest for a given wheel size , not always the best for us though .
Cheers John
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Post by madrocketscientist on Mar 9, 2018 19:04:11 GMT -5
Hi John,
I really enjoy the technical side of things, and turbines are proving to be no exception. There are so many rabbit holes to go down and explore!
Calculating the optimum inlet angles shows how a compressor for a turbine could be optimized compared to the turbocharger wheels. As the cost of 5 axis machining gets cheaper, us hobbyists may be able to make use of custom designs better suited for a turbine.
Shannon.
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Post by madrocketscientist on Mar 15, 2018 22:06:17 GMT -5
Now to build a spotwelder... I finally found an old transformer out of a microwave I dismantled, I was sure I hadn't recycled it yet but had no idea where it was. I finally found it while tiding up my workshop! Now to cut the secondary windings off. Mental note to self, they are the thin wires.... I then dug out a spare solid state relay, I knew where these were so that didn't take long. I need to go over the manual to double check if these will be enough to switch a 10 amp inductive load. The relay is rated for 20 amps but since it isn't rated for inductive loads, the actual rating will be lower for a transformer due to the large inrush currents involved. I have one relay running my dust collector and that pulls 40 amps momentarily on startup quickly dropping to 6 amps while running. That relay has been working fine for years! I also acquired this timer, it 'did have' a 400-24v transformer but that burnt out, I just need to find small 240-24v transformer since the logic inside uses 24 volts. I should have one kicking around somewhere. Can't complain about the price though, it was free!!! Shannon.
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