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Post by Johansson on Jan 7, 2015 6:07:11 GMT -5
Hopefully the ones expecting a spectacular breakdown (we are famous for those at Speed Weekend with our jet kicks) will be disapointed this year, both the new twinturbo jet kick and my bike have safety features all over the systems to prevent any failure from lost oil pressure or whatnot. I would really like a safety switch that shuts the fuel pump down in case the pressure in the scavenge line gets too high, but that is a tricky one so I just have to rely on the fact that I have two pumps with separate fuses and wiring. The Svarthålet guys are working on their pulsejet sled aerodynamics and suspension, next year they plan to build an even larger engine (the valve grid can flow ~20% more air if needed) but since they haven´t tried the new fairing at speed yet they will stick to the old engine this year.
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Post by ernie wrenn on Jan 8, 2015 15:06:22 GMT -5
Use one of the adjustable pressure transducers I sent you and a 5 pin relay to control the fuel pump circuit. Let it OPEN on pressure RISE.
Ernie
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Post by Johansson on Jan 8, 2015 17:41:00 GMT -5
I would if I could.
The problem is that the scavenge line pressure isn´t constant but follows the P2 pressure due to air bleeding past the seals, so the scavenge pressure follows the P2 but stays 0.2-0.3bar lower throughout the rpm range.
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Post by racket on Jan 8, 2015 19:36:22 GMT -5
Hi Anders
Have a low spring force pressure relief valve ( even a gravity closing check valve) in the top of the drain line to "vent" the compressed air/gas component of the scavenge mix back to the oil tank air space , at shutdown with no air/gas pressures the "relief valve " will close and the scavenge pump can then evacuate the uncontaminated/solid oil from the engine to prevent oil forcing past the seals.
Having your scavenge line pressure as high as you do could be putting a lot of axial load on the thrust bearing .
Theoretically you shouldn't have such a high air pressure in the oil cavity , the air pressure behind the comp will only be ~half P2 , the numbers for the 5:1 PR engine give a comp wheel outlet static pressure of only ~37 psia or ~22 psi gauge even though static P2 out of the comp stage will be up ~59 psi .
At the turbine end the NGV will be running choked so an ~1.9 PR across it , so even if you have a 3.75 PR ( 40 psi gauge) going into the turb stage you should only have ~15 psi gauge static pressure between NGV and turb wheel , BUT , if theres "recompression/stagnation " of the high speed gases behind the turb wheel it could be whats causing the "high" static pressure leaking back into the turb oil cavity .
Yep , I'd fit a relief valve in the line so that excess "pressure" can be dumped back to the oil tank even whilst the pump/s are operating .
Cheers John
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Post by Johansson on Jan 17, 2015 16:32:01 GMT -5
Hi John, Sorry for forgetting to reply, been up to a lot lately so I haven´t had very much time for the forums. After giving it some thought I cannot say for sure that the pressures follow each other all the way up, scavenge pressure did follow the P2 while I was video recording it though. Watch from 3:35. Wouldn´t there be a risk that the air trapped in the scavenge line will push oil out through the vent like a garden hose? And by the way guys, John already know but I have to tell you that I won the first runner up prize at the Boca Bearing contest! Did my first print two days ago, a very handy toothbrush holder! Cheers! /Anders
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Post by Johansson on Jan 17, 2015 16:46:47 GMT -5
I have not only been idling around doing non-turbine related stuff, I actually got some work done in the workshop today! I had to make a temporary front fender to keep bits of the ice track from entering the air intake, so I borrowed my Triumph bobber fender and made some new brackets for it. The front bracket looks a bit weak in the pic but it is sturdier than it looks so I think it will do for a 200km/h run. Can´t go any faster with spiked tyres and 150hp. With the fender paint drying I made new brackets for the brake fluid containers, earlier I used zip ties but that was not exactly practical. Just when I had finished that my friend who would paint the fairings called and told me that they were ready so I jumped in the car and picked them up. My very crappy pre-paint job shines through but it is a race bike so as long as it looks good at 200mph I am satisfied. Cheers! /Anders
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metiz
Senior Member
Joined: April 2011
Posts: 297
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Post by metiz on Jan 17, 2015 18:16:55 GMT -5
Too bad you didn't win first price, but a 3d printer's cool too! I kinda expected you to print one of those dick-figures you have the habbit of drawing on everything Did they say why you didn't win?
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Post by finiteparts on Jan 17, 2015 18:27:38 GMT -5
Can't wait to see it going again! The bikes looking good, not so sure about the toothbrush holder! ha! Congrats on the contest...that looks like a nice 3d printer... I have a Printbot that I have been playing with making engine mock ups. I am still trying to get things to build properly, but once I get some better models of radial turbines and compressor wheels made (ones that build right) I can send you a few if you want some desk art or to make people turbine wheel Christmas tree ornaments. Here is a radial turbine wheel that turned out ok...you can see somethign funky happened at the exducer tips (look at the tips at 11 o'clock through 1 o'clock. They seemed to bend upward). Also, have you looked into lost PLA casting? I have been thinking that might be a great way to build gear housings and such. Later! Chris
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Post by racket on Jan 17, 2015 20:54:20 GMT -5
Hi Anders
Yep, there'll be oil and air getting "vented" back to the oil tank if theres considerable air/gas bypassing the seal/s , but at idling and after shutdown you might find the scavenge pump will do its job OK .
Scavenge pumps need to be sized several times bigger than the supply, even in full sized engines with better air sealing than our piston rings .
Heh heh , love the toothbrush holder ;-)
Cheers John
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Post by ernie wrenn on Jan 18, 2015 9:46:30 GMT -5
Congrats of winning the 3D printer..... What won 1st place?
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Post by Johansson on Jan 18, 2015 14:52:30 GMT -5
Ernie & Metiz: Strangely enough they haven´t even announced the winner publicly yet despite the promise of a great unveiling the 12th january.
Chris: Thanks! I´d love to get the turbine and compressor models, they´d make great decorations at work and I can print some and test different treatments to get the rough PLA surface smoother. I think coating is the way to go since acetone vapor only work with ABS.
I am considering both lost-PLA and making green sand patterns from PLA prints, I will do lots of test casings this summer to learn more about it.
John: That is a great idea, I´ll certainly write it down in my to-do list.
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Post by Johansson on Jan 18, 2015 15:13:16 GMT -5
Today my good friend Olle came by to help me fit the spiked tyres, he is in the middle of fitting a pair of Roots compressors to his Rolls Royce Meteor V12 equipped tractor puller so I am glad that he could find the time to help out. Olle has learned the hard way that it can and most often will hurt to fit spiked tyres, this is a picture from 2013 years Speed Weekend when he and a couple of equally piss drunk guys tried to replace a blown tyre on his turbo motorcycle in the middle of the night. When they were finished they had lots of holes in them and it was blood all over the place... It went really well actually, with spiked tyres you need an inner hose (correct name?) to keep the air in and it is very easy to make a hole in it with the tyre irons. My daughter Agnes decided to help out by dropping the washers for the front fairing down the workshop floor drain. Before we changed the front tyre we fitted new ceramic wheel bearings. With the wheels in place again I could fit the fairings to check of the clearance to the spikes would be enough, at least 3cm all over so I am satisfied. The color is towards cream white and I think it suits the black frame nicely, I´ll try to get the wheels and the aluminum tanks painted in the same color this summer. Enough clearance for both the spikes and the front fender, perfect! With Olle as camera man I got some shots on the bike with me on it, it will be a bit tighter with the helmet and the leathers on but still plenty of space for legs and arms. Not easy to get the head down and still see where I am heading... Cheers! /Anders
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Post by pitciblackscotland on Jan 18, 2015 15:41:06 GMT -5
Hi Anders, That's one awesome looking turbine bike you have now!! Have you ever had time to stand back and look at the bike and think of all the hard work you put into this project?
Cheers, Mark.
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Post by Johansson on Jan 19, 2015 5:34:55 GMT -5
Hi Mark, It is easy to forget that, just forging ahead muttering about some minor issue when you really should take a step back and think about how far you´ve come. I think I´ll have me one of those moments if I manage to run a full 2km course without problems at Speed Weekend this year, sure the first road test was a mile stone but the first successful full throttle run at a race will be something to remember. Cheers! /Anders
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Post by Richard OConnell on Jan 19, 2015 10:51:35 GMT -5
Congrats on the 3D Printer! How many pints of blood in total were lost fitting those tires?
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