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Post by Johansson on Apr 30, 2015 6:04:07 GMT -5
Hi Anders, Why have you removed the pipework and the control unit from the air bleed valve on the compressor case as this is a very important unit and is required for running the engine!!! I can understand you removing the anti-ice valve and pipework as this is not required for ground running the engine but by removing the pipework and control unit for the compressor bleed valve the engine will only be able to be run at idle, this valve is an essential part of the compressor and is required in order to keep the flows correct through the varius compressor stages and to stop the compressor from surging/stalling, by disabling it through removing its control unit and pipework the valve will now be constantly open all the way through the rev range when it is supposed to close half way through the rev range, with this valve constantly open your EGT temps will exceed the top limit half way through the rev range and the compressor could surge!!!! Interesting news, according to what I´ve been told the valve is supposed to be fully open up to somewhere around 80% RPM.
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jetric
Veteran Member
Joined: December 2014
Posts: 132
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Post by jetric on Apr 30, 2015 12:14:22 GMT -5
Hi Anders, Yep that is correct as the idle speed is around 45% the valve needs to shut at around 80% are you just going to run the engine up to this point? Seems a bit of a waste as a majority of the thrust is made in that last 20%. Rich. Hi Anders, Why have you removed the pipework and the control unit from the air bleed valve on the compressor case as this is a very important unit and is required for running the engine!!! I can understand you removing the anti-ice valve and pipework as this is not required for ground running the engine but by removing the pipework and control unit for the compressor bleed valve the engine will only be able to be run at idle, this valve is an essential part of the compressor and is required in order to keep the flows correct through the varius compressor stages and to stop the compressor from surging/stalling, by disabling it through removing its control unit and pipework the valve will now be constantly open all the way through the rev range when it is supposed to close half way through the rev range, with this valve constantly open your EGT temps will exceed the top limit half way through the rev range and the compressor could surge!!!! Interesting news, according to what I´ve been told the valve is supposed to be fully open up to somewhere around 80% RPM.
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Post by Johansson on Apr 30, 2015 12:59:59 GMT -5
Hmm, I will probably live happily ever after with only aprox. 50% of the 3000lbs thrust but since it is an easy fix I could as well fit the control unit and not have to worry about it any more.
I am a bit curious about the function of the unit, there is the Pressure Ratio Switch and the Datum Resetting Valve connected to the air pressure tap on the last compressor stage.
The Datum resetting valve is a solenoid valve that seems to release the air in the lines to the atmosphere on command. I´ve seen pics of dashboards with a Datum Resetting switch, is this to manually reset the compressor air bleed valve after it has been closed?
What function has the Pressure Ratio Switch unit? Is it simply a pressure regulator that restricts the maximum air pressure that goes into the bleed valve or what?
/Anders
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Post by Johansson on May 4, 2015 14:42:41 GMT -5
I fitted the control unit to the engine again, had to re-route the air lines a bit since the original connections had to be used elsewhere. Mr Everett seemed to have removed certain nuts and fittings before shipping the engine to the guy I bought it from... I am still curious about the function of the datum resetting valve, anyone who knows something about it is free to fill me in. Cheers! /Anders
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Post by Johansson on May 7, 2015 14:27:30 GMT -5
I got the starter coupling shaft back from my friend who made a woodruff key slot in it. He also sold me a bunch of starter solenoids cheap, they are rated to twice the labeled amperage in short bursts so I think that two of them in parallel will be enough. I´ve also made some more progress on the dashboard, after some advice from "viper" I added two push buttons, one for the starter relay and an other that pulls the relay for the ignitor and the LP fuel solenoid. I´ve also added a fuel pressure gauge. Cheers! /Anders
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Post by racket on May 7, 2015 20:13:50 GMT -5
Hi Anders
You're looking at some serious Amp draw there ;-)
Cheers John
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Post by Johansson on May 8, 2015 8:35:18 GMT -5
I figured better safe than sorry.
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Post by Johansson on May 10, 2015 14:33:24 GMT -5
The starter is alive! Today I milled a slot for the tachometer magnet... ...and fitted the starter mount that I painted last week to the starter. With a set of Nordlock washers I fitted the starter to the Viper. I had to hook it up to an old car battery to find out how to connect the starter to get the engine turning the right way around, very nice to see the engine turning over and proof that the previous owner didn´t drop anything into it. Cheers! /Anders
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Post by racket on May 10, 2015 19:58:42 GMT -5
Hi Anders
Nice to see her spinning around :-)
A bit of fuel and you'll be away .
Cheers John
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Post by Johansson on May 11, 2015 0:22:39 GMT -5
And a slightly larger battery bank.
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gtbph
Veteran Member
Joined: August 2013
Posts: 101
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Post by gtbph on May 12, 2015 3:25:41 GMT -5
Hi Anders, Nice to see that beast spin! I just had an idea while looking at those starter relays. You could make a "soft start" circuit, if you connect only one battery to the first relay, and the other batteries to the second one. Then you would have two switches, and you can connect the single battery first, and a few seconds later the other ones. The more switches to flip, the more fun! But maybe it's a bad idea, I don't know. Cheers, Alain
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Post by Johansson on May 12, 2015 5:12:23 GMT -5
Thanks Alain! I´ve discussed this with a friend earlier, but as Ernie stated a couple of pages back in this thread he starts on 24V instantly without any delay and it works just fine, so I´ll try that first for the sake of simplicity.
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gtbph
Veteran Member
Joined: August 2013
Posts: 101
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Post by gtbph on May 12, 2015 9:12:12 GMT -5
Ah, ok, I see. Yes, keeping it simple first is surely a wise choice.
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jetric
Veteran Member
Joined: December 2014
Posts: 132
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Post by jetric on May 12, 2015 17:28:06 GMT -5
Hi Anders, I would seriously suggest going the two stage 12volt then 24volt starting system or a large resistor bank that would give you a soft start that you can switch out for full starter power because just using 24volts straight off is asking for trouble you are likely to snap the drive shaft that goes from the accsesory gearbox to the bevel drive gearbox in the centre of the inlet or you could shear the bevel gears inside the bevel drive box in the centre of the inlet as these are not very strong ( trust me i have seen them inside my viper601 and my viper203 that i used to own ) my viper203 with its correct o.e.m. starter motor fitted used to draw nearly 1000amps on startup with the two stage 12/24volt setup have a look on my youtube page for the video of the engine startup my user name is jetric32 on youtube, my viper203 is now fitted to Andy Plezco's jet powered BMW Mini. Your starter motor will need to spin the engine up to about 16% 2200rpm in order to avoid a hot/hung start. I think that that isolating solenoid valve on your compressor bleed valve has got somthing to do with high altitude flight, Rich. Thanks Alain! I´ve discussed this with a friend earlier, but as Ernie stated a couple of pages back in this thread he starts on 24V instantly without any delay and it works just fine, so I´ll try that first for the sake of simplicity.
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Post by Johansson on May 13, 2015 2:24:11 GMT -5
I wouldn´t want to risk breaking the drive shaft, so I´ll make it a 12/24V start. Thanks for the suggestion, I am very thankful for the hints you guys with experience in this engine give me.
I am discussing the latest 12V rotating video with Viper, compared to his engine my one is rattling quite much. Do you have any thoughts about this jetric? Is it normal and will quiet down once I get a bit more power to the starter?
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