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Post by Johansson on May 8, 2017 13:33:35 GMT -5
Hi guys, I compared the present scavenge pump to the spare one I had and it was much weaker, no idea why yet. I fitted the spare pump and tested it with positive results, not a single drop of oil coming out the drain. Time to fire up the old girl again! I can´t get my head around the high temps, they have become worse and worse every year despite several definitively positive modifications like solving the thrust bearing stricture. I´ve tried all kinds of temperature sensors and positions and right now I use an expensive Autometer sensor which should be pretty accurate. If the T2/P2 relation is compared with earlier test results there is no problem at that end, 95°C at 1bar P2 is right where it use to be. Anyone with a good idea are free to vent it before I disassemble the engine to check for wear marks around the wheels. Cheers! /Anders
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Post by Johansson on May 8, 2017 0:36:43 GMT -5
Bugger.
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Post by Johansson on May 7, 2017 14:21:58 GMT -5
Bugger Anders!, time for a new pump? We´ll soon find out, earlier with two pumps fitted they suction was so strong that I could hear air being pulled into the bearing tunnel through the shaft seals. The single pump system has not showed any signs of causing internal leaks earlier so something must have happened. The reason I removed one of the pumps and fitted a one way valve was that when the P2 start to rise I have measured a pressure buildup in the scavenge line that indicates that the pumps cannot really cope with the extra air pushed into the bearing tunnel. A one way valve should let this extra air through and lower the pressure in the scavenge line. Cheers! /Anders
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Post by Johansson on May 7, 2017 13:11:41 GMT -5
Another test, another no go. The engine idled hot as hell today for no obvious reason, after letting it cool down a bit I opened the drain plug and ran the oil pumps only to see a thick stream of oil coming out of it. WTF?? The brass gear scavenge pump (I removed the second one and fitted a one way valve this winter) has sounded a bit strange lately and with a fingertip over the suction line it feels very weak. No visible wear can be seen on the gears though. The second pump is currently fitted to the jet kick so I will go pick it up tomorrow and compare it to this one to see if it sucks any better, if not there might be an internal leak somewhere. Strange though since it idled at very moderate temps during the last run. Who said building race turbine bikes would be easy? Cheers! /Anders
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Post by Johansson on May 6, 2017 0:06:26 GMT -5
Hi Anders, Impressive work as usual! I always get amazed what you can accomplish in a few hours in the workshop! Looking forward to follow the build! Hi Thomas, Thanks a lot! The main time thief when constructing something is "thinking twice", "measuring again to make sure" and other similar habits, my workshop style is best compared with a kid running headlong down a steep hill. Cheers! /Anders Hi Anders Yep , it was always going to be a difficult job getting the gases in from the two turbos , perhaps provide a nice diffusing exhaust on the freepower to compensate for the inlet side compromises . I'd imagine it wasn't possible due to turbo installation constraints to have a pair of "tangential" inlet on opposing sides of the freepower inlet duct to promote "pre swirl" upstream of the NGV. Cheers John Hi John, Unfortunately not, I fear that the ducting for a tangential entry would end up outside the ice yacht fairings which is a no-no. Still, I spent an evening on this so if we find later that there is room for improvements I can easily blank off one inlet and fit it "the other way around" so the gasses circulate in the same direction. Cheers! /Anders
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Post by Johansson on May 5, 2017 16:11:58 GMT -5
My father will come visit this weekend (I will help him build a hydraulic forging press) so I plan to start the bike then, he hasn´t had the pleasure to witness the gas turbine bike in action yet so it is about time I recon.
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Post by Johansson on May 5, 2017 16:04:52 GMT -5
Great that you´ve started a build thread for the "Jetoped" Thomas! It is a top notch build, and with a little bit of love given to the steering arrangement it will be a jolly fun ride instead of a "shit-my-pants-full ride like it is now with the sloppy original steering wire... /Anders
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Post by Johansson on May 5, 2017 15:46:05 GMT -5
After doing this and that waiting for material and inspiration I spent an evening on the turbofan build. It feels wort of wrong to build the exhaust manifold this way, I would like to keep nice radiuses everywhere for optimal flow and so on but to keep the shaft length short and a generous air inflow area for the fan I need to compromise with the exhaust manifold. Luckily the gas producers have a bit of overcapacity so we should still be able to run the turbofan up to its max of 33.000rpm, if not I´ll just have to redesign the manifold later. After a couple of hours of plasma cutting, tig welding and coffee drinking I had a tacked together manifold on the table. Here is the power turbine NGV that it eventually will be welded to. And here it has the manifold fitted to it. I will shorten the pipes holding the V-band flanges a bit before welding everything together, to them there will be 3.5" stainless bends and a length of flexible exhaust duct leading from the gas producers placed ahead and below the turbofan in the chassis. I´ll add the drawing of the engine setup again in case someone wonders what I am doing. Cheers! /Anders
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Post by Johansson on May 4, 2017 15:26:53 GMT -5
I just got back home from a friend where we filled up my scuba bottles, now I should have air for the entire race season! Cheers! /Anders
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Post by Johansson on May 3, 2017 15:56:14 GMT -5
Looking good Stephan!
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Post by Johansson on May 1, 2017 12:57:28 GMT -5
I built one 10 years ago, but I never got around to finish it due to work and other projects. I had a nasty vibration in the engine that wrecked the ball bearings, probably caused by the home made compressor spacer surfaces being not perfectly parallel.
The idea was to build a freepower turbine for it once the gas producer was running like it should.
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Post by Johansson on Apr 30, 2017 1:34:56 GMT -5
Olov helped me to upload the new Arduino code into the throttle module, as usual my bloody PC couldn´t find any COM ports when I tried to myself so I asked him to do it before I would start yelling and screaming. Not an unusual sight when I try to do anything on a computer... I also drew up a better looking potentiometer cover and started printing before I got to bed last night. Now it looks the same as the throttle and ignition boxes. The function is flawless, now I can adjust both the fuel pump idle revs and its max revs. For JU-01 I will probably have to run the pump flat out to get enough fuel into the engine through the 0.7mm injectors but JU-02 has the larger ones so once it is installed in the bike I will need to restrict the full throttle flow to avoid overrevving it. Cheers! /Anders
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Post by Johansson on Apr 26, 2017 14:30:35 GMT -5
I was at home today taking care of a slightly ill daughter, while she was playing with this and that I drew up a potentiometer housing and 3D printed it. I will connect it to the Arduino to set the maximum fuel pump RPM, this will allow me to twist the throttle all the way to the stop while racing without risking to overspeed the engine. A very useful feature since I then can forus more on the road and less on the dashboard. Olov has sent me an updated Arduino code that I will upload into the PWM controller tomorrow, after that I will do some serious fuel pump testing to see that everything works ok before I start the bike again. A single comma at the wrong place in the code could result in an engine runaway scenario during startup and that isn´t very fun. Been there done that... Cheers! /Anders
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Post by Johansson on Apr 25, 2017 15:41:27 GMT -5
I picked up a new transistor at Olovs place today and replaced the old weak one. With the transistor in place I tested the fuel system with a 1.5mm restriction on the fuel line and got a great throttle response all the way up to 8kg fuel pressure, problem solved in other words! By the way, if you are onto Facebook make sure to follow "Mobacken Racing", that is where I post much of the more interesting things we do. Cheers! /Anders
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Post by Johansson on Apr 24, 2017 22:58:16 GMT -5
Hi Anders Always good to have them back together and working :-) Your possible temperature variation might have been caused by a previous hot streak , it'll be interesting to see how she performs. Cheers John Hi John, Exactly what I was hoping to find, a hot streak caused by a bad injector would explain why the exhaust temps have gotten worse over the years despite no visual damage or wear to the engine internals. I thought I heard the engine run much smoother than before but since it was only for a second or so I don´t want to read too much into it, the next run will show. Cheers! /Anders
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