Technical Talk

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Richie
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Re: Technical Talk

Post by Richie » Sat Nov 05, 2016 12:38 pm

Good luck for today !
Clarence come out ov zat tank at vonz !

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Renegadenemo
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Re: Technical Talk

Post by Renegadenemo » Sat Nov 05, 2016 6:54 pm

Awesome! simply awesome to sit in that cockpit and press the throttle pedal and feel the boat live and breathe and respond!
I'm only a plumber from Cannock...

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wbjohn
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Re: Technical Talk

Post by wbjohn » Sat Nov 05, 2016 9:14 pm

Thank you to everyone who attended today, without your attendance and help, days like today would not be possible. Especially members of the team who have to travel a distance.
Milestone day, well done team BBP.....

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Renegadenemo
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Re: Technical Talk

Post by Renegadenemo » Sat Nov 05, 2016 9:23 pm

Thank you to everyone who attended today, without your attendance and help, days like today would not be possible. Especially members of the team who have to travel a distance.
Milestone day, well done team BBP.....
Couldn't agree more! as I said to the TV news - there's no 'I' in TEAM
I'm only a plumber from Cannock...

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

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Stuart Baker
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Re: Technical Talk

Post by Stuart Baker » Sat Nov 05, 2016 11:49 pm

Great news guys - fantastic job, and very pleased for you.

20psi will do nicely - did it hold there as you spooled her up?

S

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Renegadenemo
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Re: Technical Talk

Post by Renegadenemo » Sun Nov 06, 2016 2:53 am

Great news guys - fantastic job, and very pleased for you.

20psi will do nicely - did it hold there as you spooled her up?
Cheers, Stuart.

Yes, the LP pressure held without flinching but it seems to have been a problem that perhaps you could shed some light on. As you know we struggled to get the engine to accelerate in the early days mostly because our piston pump just won't make servo pressure as quickly as the later model with the hydromechanical governor. The get-around fix we put on it was to reduce the pressure on the spring that controls main-burner pressurisation so it would open very early and by the time we took the engine off the test rig and put it in the boat it was performing brilliantly. But today we had a series of hot starts until we disabled the second pump and reduced the LP to 10psi. We did wonder whether our troubles were related to flushing out the Aeroshell#1 and possibly a fouled igniter (the bottom one is a bitch to get at and we went at it as a last resort) but the transformation was dramatic once we restored the LP pressure to what we'd been using before. Any thoughts?
I'm only a plumber from Cannock...

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Terminator
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Re: Technical Talk

Post by Terminator » Sun Nov 06, 2016 1:15 pm

Well what a monumental day it was now having seen Bluebird K7 strut her stuff first hand. With firstly Bill at the controls followed a little later by Ted who I must congratulate for doing a fantastic job in going through the start up procedures and running the engine up in a truly professional and controlled manor. Having gotten soaked making sure the 45 gallon drum didn’t move whilst John carefully filled the tank as the first plan of securing the drum didn’t quite work out it was time to hand over to Bill. The sound, power and passion this day has meant to me personally after many years of graft I cannot begin to describe the feeling of elation and euphoria or what it means to me personally and I would assume all members of the team present witnessing this historic milestone. However it was said to me last night on several occasion's during the evening that I must have inhaled to many kerosene fumes as I was extremely jubilant all evening celebrating with a beer or two :D Well done you old Lunatic :)

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Piston Broke
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Re: Technical Talk

Post by Piston Broke » Sun Nov 06, 2016 3:08 pm

Yes great day yesterday didn't mind the cold but would have been better without the rain (got soaked on the forklift holding the fuel up for John)
Will be downloading the video of the testing today. I know a couple of times people walked in front of the camera no doubt mike will be releasing an update video in due course

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Stuart Baker
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Re: Technical Talk

Post by Stuart Baker » Sun Nov 06, 2016 3:49 pm

Renegadenemo wrote:
Great news guys - fantastic job, and very pleased for you.

20psi will do nicely - did it hold there as you spooled her up?
Cheers, Stuart.

Yes, the LP pressure held without flinching but it seems to have been a problem that perhaps you could shed some light on. As you know we struggled to get the engine to accelerate in the early days mostly because our piston pump just won't make servo pressure as quickly as the later model with the hydromechanical governor. The get-around fix we put on it was to reduce the pressure on the spring that controls main-burner pressurisation so it would open very early and by the time we took the engine off the test rig and put it in the boat it was performing brilliantly. But today we had a series of hot starts until we disabled the second pump and reduced the LP to 10psi. We did wonder whether our troubles were related to flushing out the Aeroshell#1 and possibly a fouled igniter (the bottom one is a bitch to get at and we went at it as a last resort) but the transformation was dramatic once we restored the LP pressure to what we'd been using before. Any thoughts?
Hmm, been musing on this one today, but not sure I have a clear answer.

My anxiety about low inlet pressure comes from testing a pump with a hydromechanical governor about 20 years ago. At very low, but positive, inlet presssures, the pump performance would drop at high power conditions. Whether this was due to starving the inlet, an effect of the governor pressure balance, or a rig configuration issue, I didn't really explore. Time was precious and I just got on with getting the boost pressure back to where it should have been!

At start up conditions, I wouldn't expect LP pressure to be a big issue, and I can't think of a reason why a high LP would affect pump performance, but a low LP is not going to affect the pump running as long as it's being fed not starved. I don't have a schematic of the fuel system and will be out of the office next week, but there may be some other part of the system which could be affected although it seems unlikely.

The system you have would have been configured for the Gnat, where the aircraft tank fuel pressure was augmented using compressor bleed air, so may never have seen a high LP at start. It is possible that it doesn't respond well to high LP pressues at start up, but as I say I'm struggling for why.

I recall you having an issue with one of the pumps being seized and a certain amount of manual manipulation being required to free it. Was that this pump? Hopefully this is not a sign of any deterioration.

Anyway, I think the key thing here is that you are developing a standardised start sequence that you can use with this engine and fuel system. We could spend many hours unravelling that, but if you can get a clean start and controllable thrust without meddling with the governor then I would be inclined to declare success!

S

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Renegadenemo
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Re: Technical Talk

Post by Renegadenemo » Sun Nov 06, 2016 4:49 pm

Anyway, I think the key thing here is that you are developing a standardised start sequence that you can use with this engine and fuel system. We could spend many hours unravelling that, but if you can get a clean start and controllable thrust without meddling with the governor then I would be inclined to declare success!
There's no question it was a great success and the situation is perfectly manageable but our fuel system does seem remarkably sensitive to LP boost pressure on startup. It was dramatically overfuelling until we knocked one of the pumps off.
Next time it's on the test rig we'll put a bit more spring on the pressurising valve and see if that cures it. In 66/67 it's well documented that the engine wouldn't perform no matter what the tried until they added the second pump suggesting they had similar issues in reverse. Watching the servo pressure come up from the later pump, it's almost instantaneous the moment the engine turns but on our pump it creeps up slowly so down in the region where the engine lights, 10%-ish, there's next to no delivery pressure so to get fuel to the main burners we had to relax the pressurising valve, which I suspect has made it very sensitive to the boost pressure.
We nailed it, though, and the whole team got stuck in, got soaked, suffered the frustration of the damn thing not lighting and shooting flames across the yard to begin with but when she went - did she go!

What a day...
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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