Blackplate wrote:Once again, many thanks! I get it all so much clearer now. I thinks it's fantastic that the boat would be close-on competitive today with the speeds achieved in those days before digital control of engine, boat systems and CAD modelling. It's designed the old way, through intelligence, experience & the 'seat-of-your-pants' development. I've got to respect that. I'm somewhat impressed by the rebuild and the tin bashing involved, I think its a bold thing to have taken on all those years ago. Its a deeply impressive set of skills from fishing it out of that depth of water to up-and-running (so I do put my hands in my pockets for the project now and then in my own small way).
One small question left and I'll try and leave it for the while (honest!), How are the ignition signals generated, don't tell me they use a distributor & points?!
Because a turbojet has no cycle like a 4-stroke engine, there is no need for timed sparks. The Orpheus uses two Igniter plugs which are controlled by an on-off switch in the cockpit. When the Igniters are switched on, 24 volts from the batteries is converted to continuous HT (High Tension, in the 20-30, 000 Volt range) by the Igniter Modules, which are both original and beautifully rebuilt by Barry Hares. The HT causes a continuous spark at the Igniter plugs. Once the engine has started and stabilized, the Igniter plugs could be switched off because combustion should be continuous, but leaving them on is a good way to ensure a quicker re-light if the engine flames out for any reason - spray/water ingestion being an obvious risk in a fast hydroplane like K7.
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Re: Technical Talk
Posted: Mon Dec 12, 2016 2:19 pm
by Blackplate
Thanks for the input Rob, I'm not that up on how that is done but doesn't it need to be converted from your DC battery to a AC signal somehow to 'shake' through the coils to keep them contiuous? (Those rebuilds by Mr Hares are beautiful). Thanks all for taking the time with me I really do appreciate it. Bp
Re: Technical Talk
Posted: Mon Dec 12, 2016 2:29 pm
by rob565uk
Blackplate wrote:Thanks for the input Rob, I'm not that up on how that is done but doesn't it need to be converted from your DC battery to a AC signal somehow to 'shake' through the coils to keep them contiuous? (Those rebuilds by Mr Hares are beautiful). Thanks all for taking the time with me I really do appreciate it. Bp
Yes, the Igniter Module is a Trembler Coil, where the applied 24 Volt DC input is continually and regularly interrupted by a solenoid and the resulting pulses transformed up to HT by an associated coil. Simple but effective!
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Re: Technical Talk
Posted: Mon Dec 12, 2016 4:26 pm
by Blackplate
Oh right, I was having a bit of a think about this after my last post and thought it may be a resistor and capacitor circuit generating its own natural frequency through a low tension side of the coil, I am pushing my old physics O level here! (with a higher resistance 'before' the capacitor than the LT's side). Wrong again it seems! I have just enough knowledge to get it all wrong. Ha ha!
Re: Technical Talk
Posted: Tue Dec 13, 2016 9:24 am
by Blackplate
Yes, the Igniter Module is a Trembler Coil, where the applied 24 Volt DC input is continually and regularly interrupted by a solenoid and the resulting pulses transformed up to HT by an associated coil. Simple but effective!
I was discussing this with a colleague who does special effects and robotics. His solution was all digital and solid state. Hmm not exactly 1950's technology, daunting even.
Then I found the circuitry you describe above, by googling it. Blimey, how simple is that compared! I might rip some bits off an old motorbike and try making one for myself.
Re: Technical Talk
Posted: Tue Dec 13, 2016 12:01 pm
by rob565uk
It's good old analogue, electro-mechanical simplicity at its best really!
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Re: Technical Talk
Posted: Tue Dec 20, 2016 8:10 pm
by Renegadenemo
These guys are brilliant... Imagine the bulls**t that would have to be gone through to make this part in the UK when some teamwork and common sense is all that's needed. Then the world complains that the Chinese make stuff on the cheap. Now who has all the sense here?
Re: Technical Talk
Posted: Tue Dec 20, 2016 10:11 pm
by Jordangbr
Were they drop forging you a new bog seat Smith?
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Re: Technical Talk
Posted: Thu Feb 09, 2017 1:19 am
by Renegadenemo
The main planing wedge went back on today using all of its original bolts. It's been a fortnight's work culminating in a splendidly coordinated operation involving all the crew and the biggest dish of choccie we've ever mixed. An outstanding effort to put it back once and for all eleven years after it came off.
Re: Technical Talk
Posted: Fri Apr 14, 2017 2:10 am
by Renegadenemo
Got the little plastic racing car back on the road today after a few years' absence. She's been for a heavy maintenance visit at HHC Sportscars (http://www.hhcsportscars.co.uk/) - old friends of mine - and is fighting fit once again. It's a good omen.