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Re: Pic of the Day

Posted: Wed Jun 20, 2018 4:52 pm
by Engine 711
I hope the colour of K7's dashboard is not another puzzle.... Like Bluebird Blue.....!

Looks to be Black, in the Paul Allonby photos.... But they are Black & White photos.... ;)

Re: Pic of the Day

Posted: Wed Jun 20, 2018 9:33 pm
by Mike Bull
Yup, matt black, simple as that.

Re: Pic of the Day

Posted: Thu Jun 21, 2018 9:20 am
by Engine 711
Good to an engine back in place... :)

Surely, Scotland is the place to try the on-board Start System...? By all means have the proven off-board system there as well, but give the on-board system a go as well...? :?

Re: Pic of the Day

Posted: Thu Jun 21, 2018 10:57 am
by Renegadenemo
Surely, Scotland is the place to try the on-board Start System...? By all means have the proven off-board system there as well, but give the on-board system a go as well...? :?
If you want to decant gas at 200bar into it you're very welcome. Personally I'll hang on until it's had a thorough strip, rebuild and hydrostatic test on the bottles. Also, the LP starter is more hungry than the HP one it was designed for. We'll get it working, just not this time.

Re: Pic of the Day

Posted: Thu Jun 21, 2018 11:32 am
by Engine 711
Renegadenemo wrote:
Thu Jun 21, 2018 10:57 am
Surely, Scotland is the place to try the on-board Start System...? By all means have the proven off-board system there as well, but give the on-board system a go as well...? :?
If you want to decant gas at 200bar into it you're very welcome. Personally I'll hang on until it's had a thorough strip, rebuild and hydrostatic test on the bottles. Also, the LP starter is more hungry than the HP one it was designed for. We'll get it working, just not this time.
I thought I had read (on here) that the on-board spheres had been hydrostatic tested, some time ago - albeit to a reduced pressure...? Wrong again, obviously. But still happy to decant to whatever the current working pressure is.... :)

Am pretty sure K7 must have a pressure regulator for the air start system, to drop the pressure from 3000psi to say 250psi (for the HP starter). There could be potential to adjust and/or mod this reg (perhaps re-spring it..?), so as to deliver less pressure, to suit the LP starter.

Re: Pic of the Day

Posted: Fri Jun 22, 2018 12:58 am
by Renegadenemo
The bottles were tested to their old working pressure, 3200psi, then given a new working pressure of 2000psi, which isn't enough for a good start with our current setup. The LP starter needs a large volume of LP gas but we have to get that volume down the narrow plumbing of the original HP delivery system and so the problems multiply, hence exploring the gas delivery methods embodied in the old HP starter by nicking one from a museum engine then adapting one of the LP starters to take advantage of what we learned. We'll get it going with a methodical approach but HP gas is lethal.

What's a truck tyre inflated to? 100psi, maybe? Anyone want to be near a pair of quarter-inch wall thickness spheres with 2000psi inside if one chooses to let go?


Air start

Posted: Fri Jun 22, 2018 10:48 am
by Vernon
Hi
Regarding yesterday's pic of the day ( air start ) it was mentioned this will be carried out externally at Scotland. What is the reason behind this ?
Many thanks
Vernon

Post moved to where the answers are- see above! -Mike

Re: Pic of the Day

Posted: Fri Jun 22, 2018 1:38 pm
by Engine 711
Renegadenemo wrote:
Fri Jun 22, 2018 12:58 am
The bottles were tested to their old working pressure, 3200psi, then given a new working pressure of 2000psi, which isn't enough for a good start with our current setup. The LP starter needs a large volume of LP gas but we have to get that volume down the narrow plumbing of the original HP delivery system and so the problems multiply, hence exploring the gas delivery methods embodied in the old HP starter by nicking one from a museum engine then adapting one of the LP starters to take advantage of what we learned. We'll get it going with a methodical approach but HP gas is lethal.
Ok, thats what I recall, re WP.

Reading up on the K7 air start system (in Neil Sheppard's book), the system was adapted by Rotax, using parts from their Gnat system - '... comprising two spherical air bottles containing 39lbs of dehumidified air, compressed to over 3000psi.' I reckon thats 39lb per sphere - as the volume of 39lbs of air at 3200psi should be about a 500mm diameter sphere - which the Mk1 eyeball suggests is about right... ;)

Yes, blowing them to only 2000psi doesnt exactly help. But if the original set up gave 6 starts - which it did (tested at Norris Bros, before going North), then 2000psi potentially could give 4 goes. But only if the air consumption (so mass flow) of the LP starter can be got to be similar to the HP one. Do you know if the LP & HP Orpheus Starters look similar - could the guts be common...? Or are they totally different sizes....? The pressure drop is dramatically different (250 psi versus 40psi) - and its the drop in pressure across the turbine which creates the energy.

Found a bit of info, online. The HP Orph starter ran at 250 to 320psi, using 0.8 to 1.0 lb/sec of air - and could get the engine lit in 4 seconds using 6 lb of air...! (yes, that doesnt add up). THe LP starter is mentioned, but no detail is given.

https://www.flightglobal.com/FlightPDFA ... 200449.PDF

I agree HP air is scary, but check the speed Air Starter Turbines run at - 100,000rpm or more. (I mean the actual Turbine rotor - not the output which is geared down a lot - typically by around 20:1, to spin the compressor up to say 5000rpm.)

Re: Pic of the Day

Posted: Fri Jun 22, 2018 3:04 pm
by Mike Bull
Engine 711 wrote:Reading up on the K7 air start system (in Neil Sheppard's book), the system was adapted by Rotax, using parts from their Gnat system - '
The air start installation on Bluebird came from the uncompleted second Hunting H.126 aircraft, not the Gnat.

Re: Pic of the Day

Posted: Fri Jun 22, 2018 3:17 pm
by Engine 711
Mike Bull wrote:
Fri Jun 22, 2018 3:04 pm

The air start installation on Bluebird came from the uncompleted second Hunting H.126 aircraft, not the Gnat.
https://en.wikipedia.org/wiki/Hunting_H.126

I see that had an Orpheus 805.