Technical Talk

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Renegadenemo
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Re: Technical Talk

Post by Renegadenemo » Fri Nov 18, 2016 2:03 am

We now have the gutted hull back on the rollover jig and we're into the fabrication again with the outer floors remaining the last big challenge. While Jordan and Dave de-riveted the forward ends of the skins that tore loose in the crash taking the rivets with them (oh what fun we used to have in our endless sea of de-riveting) Mike wandered about with a brush and a tin of Hammerite picking up the bits he had missed while the boat was right way up. Meanwhile, I got stuck into the corrugations from the nose floor and instantly remembered what an absolute b'stard it is to get a crashed, corrugated panel back into tolerance. Please can we go back to engines that won't start? They suddenly seem so much easier.
I'm only a plumber from Cannock...

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Blackplate
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Re: Technical Talk

Post by Blackplate » Fri Dec 09, 2016 9:47 am

Hi, going off the current topic and trying to understand these jets a little better : I've done some homework and read that the boat uses a total loss battery system ad the alternator has been removed. Ok, I get that for things like ignition systems,fuel pumps and for control. Does it provide power for the hydraulic and lubrication pumps too? There's some fairly hefty looking pumps etc including a gearbox (I read) under the tinware & can imagine they have quite demanding power requirements, I'd be quite impressed if that's all running from the batteries. Or is there another way, like a hydraulic pump driven off the main shaft that does all the extra work? I can''t see one mentioned.

(I suppose an alternator would have once been in the nose cone near the air start at one point).

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Renegadenemo
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Re: Technical Talk

Post by Renegadenemo » Fri Dec 09, 2016 12:37 pm

The aircraft uses a DC generator driven from the engine gearbox as is the hyd pump. The electrical system on the boat only powers the boost pumps and igniters so for the shore durations expected on record runs it's more than adequate.
I'm only a plumber from Cannock...

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rob565uk
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Re: Technical Talk

Post by rob565uk » Fri Dec 09, 2016 1:02 pm

Renegadenemo wrote:The aircraft uses a DC generator driven from the engine gearbox as is the hyd pump. The electrical system on the boat only powers the boost pumps and igniters so for the shore durations expected on record runs it's more than adequate.
The on board batteries are 75 Ah rated and in theory could power the boat continuously for around 5 hours at full load. As Bill says, more than enough capacity for short record runs.


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Blackplate
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Re: Technical Talk

Post by Blackplate » Fri Dec 09, 2016 2:44 pm

Ok thanks, that helps. Hope this doesn't sound too dumb though but I can't find a definitive ; Where's the engine gearbox drive from? I can imagine something like a planetary set under the nose but a geared running-ring off the rotors with a hole in the pipe for a primary gear to is a mind boggling thought. Cheers all.. Bp.

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Re: Technical Talk

Post by Renegadenemo » Fri Dec 09, 2016 3:11 pm

Ok thanks, that helps. Hope this doesn't sound too dumb though but I can't find a definitive ; Where's the engine gearbox drive from? I can imagine something like a planetary set under the nose but a geared running-ring off the rotors with a hole in the pipe for a primary gear to is a mind boggling thought. Cheers all.. Bp.
Where the start turbine plugs into the nose of the main shaft, under the inlet bullet, there's a bevel gear driving a vertical shaft that goes down into the gearbox at the front and below the engine. The gearbox then drives the main fuel pump, the hyd pump and a generator, though we don't use the generator.
It also drives the main lubricating and scavenge pumps bolted to the outside of the gearbox and fed via those stainless pipes from the tank up top (one pressure and two scavenge stages in there). There's an additional scavenge pump inside the gearbox. There's also a metering pump that drip-feeds oil to the various bearings and gears including the rear turbine bearing where it's burned off.
The bearings, etc all have two oil pathways and the metering pump will send oil down them alternately so if one becomes blocked the other will still lubricate the relevant gear or whatever, but there's only one feed to the rear bearing.
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Blackplate
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Re: Technical Talk

Post by Blackplate » Fri Dec 09, 2016 5:35 pm

Excellent, thanks. I can picture that. There's a CCU and I think a blocktube (?) yet to look at that I don't 'recognise' and I'll have a much better understanding. It's not rocket science, seems more complicated! An art to balancing up the various conditions anyway. Cheers T

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Renegadenemo
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Re: Technical Talk

Post by Renegadenemo » Sat Dec 10, 2016 7:11 pm

There's a CCU and I think a blocktube
The Bloctube control is just a lever in the cockpit that opens the throttle 30 degrees for starting. The CCU or Combined Control Unit is basically the engine's fuel injection system. Fuel to the main burners is regulated through a valve controlled by the throttle. The CCU also controls startup and has a barometric pressure control to compensate for pressure changes with altitude. It's quite a piece of kit.
I'm only a plumber from Cannock...

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Blackplate
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Re: Technical Talk

Post by Blackplate » Sun Dec 11, 2016 8:54 pm

I see, it sure is an education. I haven't had the diary to refer to these past few days so this really helps. Thanks. So, the bloc tube, dare I say it, acts like a (fuel only) choke? Left off on 'hot' starts? From memory, was there a second lever? Main throttle?
Ok & the CCU I suppose is analogous to the modern ecu on a fuel injected reciprocating engine but because has no digital data input runs with/from an ambient pressure balance valve like a diver's first stage?
If that's ok, I think I get the complete general picture.
PS thanks for the daily pictures. I think being so consistent over the years with them is a winner. Bp

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Renegadenemo
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Re: Technical Talk

Post by Renegadenemo » Sun Dec 11, 2016 9:11 pm

So, the bloc tube, dare I say it, acts like a (fuel only) choke? Left off on 'hot' starts? From memory, was there a second lever? Main throttle?
Ok & the CCU I suppose is analogous to the modern ecu on a fuel injected reciprocating engine but because has no digital data input runs with/from an ambient pressure balance valve like a diver's first stage?
Once the engine is running the CCU is basically a tap that admits more or less fuel depending on throttle position. It is opened 30 degrees for starting in all conditions, hot or cold, and when closed the engine stops. The Bloctube control - so called because it was made by a company called Bloctube Controls - is just a precision lever that opens the tap 30 degrees. The tap has 90 degrees of travel all-told so 30-90 is controlled by a foot throttle but the CCU is not like a 1st stage. It merely allows fuel to pass through itself and be metred by the throttle valve.
It has some additional features for startup and altitude compensation but mostly it's as above.
I'm only a plumber from Cannock...

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

Voltaire's apology when he wrote a long letter: "I didn't have time to make it shorter."

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