ashpowers
Veteran Member
Joined: February 2011
Posts: 207
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Post by ashpowers on Jul 3, 2014 17:47:27 GMT -5
Great job Anders! Can't wait to see this beast at the strip! =)
Just curious, are you planning to put any kind of a scatter shield around the freepower turbine? If the gearbox fails and that wheel goes without load I'd imagine it would raise an eyebrow or two if she lets go. Just looking out for your arse.... literally! =)
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Post by Johansson on Jul 4, 2014 3:49:18 GMT -5
Thanks John and Ash, a couple of weeks from now I hould have everything set for a start. Vacation gets in the way sort of since we will spend most of it at our relatives place but at least I can promise that I will beat winter to it. Ash: Not really, the steel housing for the turbine wheel is pretty sturdy but other than that I only have a thin stainless heat shield planned. Dropping the wheel at full revs would not be very pleasant but I don´t think it is doable to fit a burst shield strong and large enough to prevent personal injury should it happen.
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Post by pictsidhe on Jul 5, 2014 15:53:41 GMT -5
That power turbine is a bit scary with little containment. How much of a job would be be to put some sort of pickup in to sense rpm? Sensing blades would get round a sheared key, but I can't think how to do that reliably. Magnetic sensor in the gearbox?. Some electrickery to sense rpm shooting up or going over a set limit that kills the fuel pump seems a good idea to me.
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Post by pictsidhe on Jul 6, 2014 10:03:16 GMT -5
I've had an idea about sensing rpm. Blades generate strong pressure variations. If you have a microphone right up close to the blades, you should get a decent signal once noise is filtered out. If yo7 have the sensing point swept by blades, you'll get a great signal. 'Up close' can be a microphone on the end of a long tube which ends near the blades with the microphone a healthy distance away (another airbox wart?) with the tube in coolish air. at At 30,000 rpm and 40 blades (is that right?), there should be a good strong 20kHz signal. Ultrasonics seem in order for overrevving sensitivity. I'm not sure a standard microphone would take the pressure. A piezo transducer seems worth trying. Do you know anyone with gear who could test this idea when you do engine tests? Kunifer brake pipe tube?
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Post by Johansson on Jul 6, 2014 13:19:40 GMT -5
I have a magnetic pickup on the gearbox output shaft, a strong LED light in the dashboard will activate when I reach top revs to indicate wheel spin.
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Post by Johansson on Jul 9, 2014 13:06:35 GMT -5
The Mercedes throttle position sensor I was going to use as a PWM throttle didn´t work out, it had a too narrow resistance width so I had to take it apart with the hack saw and modify it so I could couple a regular potentiometer to it. Works like a charm but not very fancy, I will make a water tight casing around it later. After that I fitted the ignition system to the box and wired it up, so now I have both spark and propane solenoid activation when I push the preheat button. Only some adjustment of the Hobbs safety pressure switches to do and heat shielding the bundle of cables before I can plan for a start attempt! Cheers! /Anders Tjo!
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Post by racket on Jul 10, 2014 4:39:26 GMT -5
Hi Anders
Thats become one complicated mass of wires and plumbing .............but looking great :-)
Cheers John
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Post by Johansson on Jul 10, 2014 6:52:34 GMT -5
Hi John, Yup, it is starting to become difficult to explain the simplicity of gas turbines to people visiting my workshop... Cheers! /Anders
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Post by Johansson on Jul 11, 2014 16:16:50 GMT -5
I measured the oil flow through the engine yesterday to see exactly how much that passes through it in a minute, at 5 bar oil pressure I got 1.8 liters/minute through the scavenge lines. Other than that I bundled the wiring together and heat shielded it with exhaust wrapping and aluminum tape where it will be subjected to radiant heat from the engine. Earlier I bought a lenght of heat resistant cable cover that I intended to use on the bleed air line from the engine to the gearbox. Since the bleed air line is standard pneumatic hose (to see any eventual oil leakage) I needed to shield it, if not it would probably have melted. The battery got wrapped with a section of fire blanket. With that done I adjusted the two Hobbs pressure switches, one set to 3 bar on the oil line and one set to 3 bar as well on the P2 line to the pressure gauge. If the oil pressure drops below 3 bar the fuel pump shuts off, also if the P2 rise above 3 bar it shuts off. That is a simple and bullet proof over speed protection in case the PWM controller fails and lets the fuel pump run flat out. I would never have time to manually shut the engine down in case it happens during a run so it will be a great safety feature. This weekend I will test the preheat system and when it is checked I can start filling the scuba tanks for the upcoming test start! Cheers! /Anders
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Post by racket on Jul 11, 2014 17:48:00 GMT -5
Hi Anders
Heh heh , I can almost smell the kero burning, getting very close :-)
Cheers John
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ashpowers
Veteran Member
Joined: February 2011
Posts: 207
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Post by ashpowers on Jul 11, 2014 18:08:44 GMT -5
Very beautiful work, Anders! =) Keep it up!
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Post by Johansson on Jul 12, 2014 3:32:07 GMT -5
Thanks! Just need to get a high flow propane regulator before I can test the preheat, perhaps a test run next week?
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rythmnbls
Veteran Member
Joined: August 2011
Posts: 145
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Post by rythmnbls on Jul 12, 2014 8:13:09 GMT -5
Awesome, we've been waiting since last winter to see Anders in the suit, and the bike too
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Post by Johansson on Jul 12, 2014 16:51:31 GMT -5
No suit this time unfortunately, I save it for the first time runs and this is a second so I´ll probably be in my jeans. I took the bike outside to get a video of me testing the propane preheat an hour ago, my feancee held the camera while I was busy talking my head off and getting the preheat to light off. Just before the camera was started I did a test where it lit immediately but when the camera is rolling I gave it too much revs before I hit the preheat button so it took a while before it lit off. All I need to do now is to refill the scuba tank and bleed the rear brake caliper in case I want to take her for a short run if everything seems to work ok. Fun times ahead! Cheers! /Anders
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Post by ernie wrenn on Jul 12, 2014 21:55:29 GMT -5
Way to go!!! Beautiful!!
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