Technical Talk

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Mike Bull
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Re: Technical Talk

Post by Mike Bull » Sat Nov 05, 2016 11:01 pm

Yes, it's been one heck of a day...I got in at daft-early-o'clock, got the heating on and pottered about on my own, putting in the first fuel that the boat has seen (tasted?!) in 50 years, and noting with interest that both LP Boost pumps running together for the first time were putting out nearly 20p.s.i.

With the air bottles charging and the rest of the team arriving thick and fast we were soon giving the engine a quick wet and then dry crank, to shift the inhibiting fluid and get the kerosene moving through. Despite a lot of misgivings about the shocking weather conditions/forecast, it was all hands on deck to pull the boat out of her little workshop and around the block into the yard. We got her there in the bright sun but within moments the sky had blackened and it was howling down- a special medal goes to John for service in extreme conditions, perched as he was on top of the boat filling the main fuel tank as it chucked down! With the old girl brimmed and Gerry from the BBC just arrived, we had a few goes at getting her running, and as ever she twisted and complained a bit at first but then, gloriously, she was alive.

Now, I've seen this particular Orph start a stupid number of times, and I've even seen and heard it run to 65% while breathing through the boat's intakes before, so why was this run so different, so special? Because, now, it was Bluebird.

A quick play with some online calculator thingy tells me that it's been 18,203 days, 6 hours and 53 minutes between in-hull engine runs and like all ladies, she can be as fashionably late as she likes... 8-)

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...

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

I have wrought my simple plan
If I give one hour of joy
To the boy who’s half a man,
Or the man who’s half a boy.

Sir Arthur Conan Doyle.

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

Well done to all the team [.][.]
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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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Mike Bull
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Re: Technical Talk

Post by Mike Bull » Sun Nov 06, 2016 4:28 pm

Piston Broke wrote: no doubt mike will be releasing an update video in due course
Indeed- busy with it now- should be up by tonight. :ugeek:

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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.

I have wrought my simple plan
If I give one hour of joy
To the boy who’s half a man,
Or the man who’s half a boy.

Sir Arthur Conan Doyle.

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Mike Bull
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Re: Technical Talk

Post by Mike Bull » Sun Nov 06, 2016 6:06 pm

Nice double page spread in today's Sunday Mirror, too.

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Renegadenemo
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Re: Technical Talk

Post by Renegadenemo » Sun Nov 06, 2016 6:16 pm

I'm only a plumber from Cannock...

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

I have wrought my simple plan
If I give one hour of joy
To the boy who’s half a man,
Or the man who’s half a boy.

Sir Arthur Conan Doyle.

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