Technical Talk

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Engine 711
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Re: Technical Talk

Post by Engine 711 »

mtskull wrote: Tue May 22, 2018 10:37 pm
Richie wrote: Tue May 22, 2018 1:12 pm but in answer to the question, the thing on the fin is still a pitot tube :D
Or to be precise, a pitot/static tube.
Correct.

I did dare say that..... :?
Vernon
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Bluebird crash

Post by Vernon »

Hi all
I couldn't help notice during watching the spirit reborn DVD that bluebird lands on her port side in the simulation. I have watched footage & studied pictures & I can see it was an impact starboard side if I'm not mistaken. Could you clarify.
Thank you
Vernon
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Re: Technical Talk

Post by Vernon »

Thanks Mike
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Renegadenemo
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Re: Technical Talk

Post by Renegadenemo »

The boat rolled rapidly to the right whilst upside down in the air with the fin leading then rolled equally fast the other way once she righted herself in mid air so, though she landed almost level, the left hand sponson arriving first but not by much, she was still rolling fast and basically twisted the centre hull from under the front spar such that it landed left side down. The cockpit was shorn off from left to right with the left hand cockpit wall separating between frames 15 and 17 with the 15-17 section sinking not far from the impact point whilst the 17-23 (tip of the bow) piece rolled all the way under then was ejected on the other side to leave the water again like a skimming stone to land about 160m from the impact point to the NE. The front spar went 150m straight down the boat's track before splashing down with big chunks of upper sponson fairing attached. The rest of the cockpit structure disintegrated and sank not far from where the main hull came to rest.
As Mike already mentioned, look at the pic's of the recovered wreck and you can see how the LH inlet was torn open and the RH crushed shut. This is what tripped the boat up and caused that tumble seen in the footage. The damage to the fin fairing also tie in perfectly with this.
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Re: Technical Talk

Post by Renegadenemo »

Have to say a massive well done to the crew and everyone else involved because today K7 was finally lifted onto her new launch and recovery cradle, which even incorporates two of its original wheels and stub axles. We hefted the big, heavy lump onto a perfect recreation of the unsung hero that was her trailer so now she looks even more like herself than ever before. Pic's shortly.
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Re: Technical Talk

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First engine start since 2016 tonight and, like everything else, full of legacy-headaches from 1966. Despite our best care and efforts we had a rather hot-start with much fire requiring extra effort to blow the fire out, rein in the JPT then shut down and dry-crank to get the heat out of the engine. Not a conspicuous success.
The main issues were de-inhibiting the engine, as it doesn't like to burn a mix of Aeroshell 1 and kero, possible mis-adjustment of the control runs such that we didn't achieve idle, and therefore sufficient mass airflow to pull the heat away in the prescribed startup time and the shocking design of the combustor drain tank such that its pipework is higher than the tank so it doesn't actually drain. Whose stupid idea was that? At least the inhibitor is out of there now having achieved a successful acceleration to idle - eventually.
We also remain unsure on the possible influence of our second LP boost pump on fuel scheduling on startup but at least we can simply disable that.

What was an amazing success and a great team effort was getting the boat out of the workshop with inches to spare, into the yard then back again. OK - so it took a little fiddling about as it was our first try but we did it with no damage except a few frayed tempers and a late finish.

Someone remind me why we do this?
I'm only a plumber from Cannock...

"As to reward, my profession is its own reward;" Sherlock Holmes.

'Sometimes you gotta be an S.O.B if you wanna make a dream reality' Mark Knopfler
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Engine 711
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Re: Technical Talk

Post by Engine 711 »

Renegadenemo wrote: Thu Jun 28, 2018 12:02 am First engine start since 2016 tonight and, like everything else, full of legacy-headaches from 1966. Despite our best care and efforts we had a rather hot-start with much fire requiring extra effort to blow the fire out, rein in the JPT then shut down and dry-crank to get the heat out of the engine. Not a conspicuous success.
The main issues were de-inhibiting the engine, as it doesn't like to burn a mix of Aeroshell 1 and kero, possible mis-adjustment of the control runs such that we didn't achieve idle, and therefore sufficient mass airflow to pull the heat away in the prescribed startup time and the shocking design of the combustor drain tank such that its pipework is higher than the tank so it doesn't actually drain. Whose stupid idea was that? At least the inhibitor is out of there now having achieved a successful acceleration to idle - eventually.
We also remain unsure on the possible influence of our second LP boost pump on fuel scheduling on startup but at least we can simply disable that.

What was an amazing success and a great team effort was getting the boat out of the workshop with inches to spare, into the yard then back again. OK - so it took a little fiddling about as it was our first try but we did it with no damage except a few frayed tempers and a late finish.

Someone remind me why we do this?
Oh dear.... :( Sounds like it was rather too exciting.

A way to 'de-inhibit' is to do some wet motors (or cranks) - like a start, so fuel on, but with no ignition. BUT this assumes your drains work well...! ANd you need a least 1 dry motor (or crank) - so just starter only - to 'blow' any fuel left in the engine out of the back. If in doubt, do 2 or more. All of which hammers your Start system - which you don't want to really do. Bugger.... :|

Cannot see how the 2nd Boost Pump/Tank can affect starting - BUT its a HydroMech system, so anything's possible.... :?

Why...? Because the end result is worth it.
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Re: Technical Talk

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A way to 'de-inhibit' is to do some wet motors (or cranks) - like a start, so fuel on, but with no ignition. BUT this assumes your drains work well...! ANd you need a least 1 dry motor (or crank) - so just starter only - to 'blow' any fuel left in the engine out of the back. If in doubt, do 2 or more. All of which hammers your Start system - which you don't want to really do. Bugger.... :|

Cannot see how the 2nd Boost Pump/Tank can affect starting - BUT its a HydroMech system, so anything's possible.... :?
We did two wet cranks then two dry cranks, leaving an hour between the last two but the drains were rigged in 1966 configuration and simply didn't drain. We've fixed that now.

The fuel system was set up by AEC but to the 101 spec, which uses a different pump that generates servo pressure instantly. On our 1959 pump the servo pressure is generated centrifugally via drillings in the rotor so it comes up very slowly. Because of this we had to go very light on the spring in the pressurising valve that schedules fuel on startup. When we jumped the LP boost pressure from 10 to 20 psi we overfuelled. Seems incredible but the delivery pressure has to climb through 20psi on its way to idle so the appearance is that we're affected by the second pump. That question is yet to be satisfactorily answered.
In the meantime we had some good engine runs yesterday to test the drains and the hyd system. We had a failure with the hyd when the accumulator let go but we can run without that. We still have the water brake so long as the engine keeps turning, it's only in the event of a flameout that we lose the brake.
We had some failed starts later traced to the batteries getting low and not allowing sufficient time for the igniters to clean themselves. Our throttle linkage gave some setting up issues with a high idle and not hitting 100% but we've pretty much bottomed that and we had a minor fuel leak. Lots of practice in handling the boat on the cradle in and out of the workshop so our crew training is already well advanced. Bute is raring to go with the red carpet fully rolled out but not a peep from Coniston. Hopefully they're on it too.
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Engine 711
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Re: Technical Talk

Post by Engine 711 »

You are speaking 'Derby', if you call them Cranks...... ;) Two Dry is cool, after any Wet - thats on the cautious side.

Servo pressure was (AFAIK) generated by an orifice of drilling in the Pump body, which bled Delivery pressure off. Servo was generally about 100psi less the Delivery. Looking as the Bristol Siddeley Orpheus 10001 ECU Fuel System Diagram (as you do....), the Servo drilling/orifice is visible just to the right of the HM Governor Diaphragm on the pump (where the Yellow & Orange colors meet). LP Fuel Pressure is usually the 'reference pressure' that everything bleeds back too - altering it can change everything - so I am not that surprised the change in LP pressure severely messed up starting.

Otherwise - all good.... But nothing from Coniston...? Not surprised.
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Re: Technical Talk

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Looking as the Bristol Siddeley Orpheus 10001 ECU Fuel System Diagram (as you do....), the Servo drilling/orifice is visible just to the right of the HM Governor Diaphragm on the pump (where the Yellow & Orange colors meet).
Now if we had that type of pump we'd be OK. Ours predates the HM governor and generates servo by basically centrifuging fuel through drillings in the pump rotor. It's therefore dependent on rotor speed rather tapping into delivery pressure. Seeing as the servo strokes the pump it's easy to see why we had to go light on all the settings to get the engine to start. we have a couple of Orph' 101s with the later pump and the one we have run and instrumented uses double the servo pressure and generates it instantly.
I'm only a plumber from Cannock...

"As to reward, my profession is its own reward;" Sherlock Holmes.

'Sometimes you gotta be an S.O.B if you wanna make a dream reality' Mark Knopfler
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