Pic of the Day

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Engine 711
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Re: Pic of the Day

Post by Engine 711 » Mon Jun 25, 2018 3:54 pm

Renegadenemo wrote:
Mon Jun 25, 2018 2:29 pm
The problem there is that all the delivery plumbing is for the HP setup so it's all inch bore and that's without all the valves and convolutions in the pipework. It's easy to turn the pressure down to 40psi but the plumbing then won't flow sufficient volume to be of any use. To get sufficient volume down the pipe we need to push it with higher pressures but then it expands inside the start turbine case and mostly escapes around and past the turbine without doing any useful work. Indeed, condensation can be seen forming a foot ahead of the turbine exhaust showing that the gas is still expanding all the way out there. it's incredibly wasteful. The answer looks to be the hybrid LP/HP starter with the nozzle plate. That way the gas can only expand directly out of the nozzles and onto the turbine vanes. It must form an orderly queue to get out of the case and must go via a vane on the way. Our current nozzle plate doesn't have an o-ring seal around its outer edge so we have a loss there but initial tests suggested it halved our gas consumption for the same engine speed. The noise it makes, however, is horrendous. an awful ear-piercing scream.
OK. That makes sense. I would put any orifice as close to the Starter as possible, so that the pipework is still as high a pressure as possible.

The LP Starters and Start valves I worked with (Trents & 211's), had connections around 3 inch diameter - in order to flow enough air at 40psi to actually work. The start valves were butterfly types, mounted fairly close to the starter - sometimes even right on the starter inlet. In contrast, the HP systems (Olympus) were around 1 inch or 1.5inch diameter. Could even have had common parts with K7's system.

The HP starter sounds like it was a Impulse turbine, with HP air being 'shot'/expanded through fixed nozzles directly into the turbine rotor (so there are no stator vanes) - whereas the LP starter was probably more of a Reaction (*) Turbine, with a set of stator vanes before the rotor (which increase the velocity of the aire, before it goes into the rotor, where it expands).

(* - strictly probably a 50% Reaction/50% Impulse Turbine - which is normal for gas turbines)

You could perhaps add an O-ring to better seal your plate....? The awful scream is probably unavoidable..... ;)

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thunderer
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Re: Pic of the Day

Post by thunderer » Tue Jun 26, 2018 5:17 am

Any "scream" in relation to compressed air is unavoidable unless a "muff" (silencer) is utilised. It is the interaction between velocity of the air, the size of the orifice it is venting from and air turbulance that causes it. The higher the pressure, the higher pitch the "Scream" will be. The greater the volume of air, the longer it will last.

Working with compressors and compressed air taught me many things but most notably, that compressed air is a killer, even at low pressure. One other notable point is that when draining off a system/allowing air to freely vent to atmosphere quickly, you should always wear ear-protection as prolonged exposure to the higher pitch "scream" of escaping air can and will cause damage to your ears and induce early deafness.
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mark-f
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Re: Pic of the Day

Post by mark-f » Tue Jun 26, 2018 8:46 am

Does anyone know what happened to the original cradle? It was certainly still up at Pier Cottage in the mid 1980's. It was just outside the gate on the right hand side as you went in.

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Mike Bull
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Re: Pic of the Day

Post by Mike Bull » Tue Jun 26, 2018 8:58 am

We pursued leads and believe it got taken south and scrapped, in fairly recent times. I've written a diary about the new one, which will go online soon. 8-)
'I am not what is called a "civilized man", Professor. I have done with society for reasons that seem good to me.'

Black Knight
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Re: Pic of the Day

Post by Black Knight » Tue Jun 26, 2018 9:38 am

How far behind is pic of the day to the stage the boat is right now?

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Mike Bull
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Re: Pic of the Day

Post by Mike Bull » Tue Jun 26, 2018 10:44 am

It isn't, really; if anything, with so much going on I've been really brutal with picture choices so I could get it more up to date again. The cradle was wheeled out last Thursday and the boat put on it then- you'll see that in a couple of days. Only significant things to happen to the boat herself since have been the canopy arriving and finishing the off board air connection, and you've seen those here.

Don't forget though, the boat won't be finished-finished when she goes to Scotland.
'I am not what is called a "civilized man", Professor. I have done with society for reasons that seem good to me.'

Black Knight
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Re: Pic of the Day

Post by Black Knight » Tue Jun 26, 2018 12:06 pm

Thanks Mike, I was only wondering as following the pics then a video diary appears & that seems way ahead.

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Mike Bull
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Re: Pic of the Day

Post by Mike Bull » Tue Jun 26, 2018 12:26 pm

I always used to wait until all the pics had appeared online before I put a video up, but these days such is the rate of things I've been letting the videos go a bit early sometimes. From comments etc it's amazing how many people only ever see one or the other, but never both, so there's always a grey area as to who's seen what.
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Black Knight
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Re: Pic of the Day

Post by Black Knight » Tue Jun 26, 2018 12:27 pm

Is there a pic of the boat hanging from the ceiling???

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Mike Bull
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Re: Pic of the Day

Post by Mike Bull » Tue Jun 26, 2018 12:30 pm

*sigh*

You're getting greedy now...why not wait and see? ;)
'I am not what is called a "civilized man", Professor. I have done with society for reasons that seem good to me.'

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