external safety loops for fast ic power

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8 September 2013 at 14:39 #43604
captainslog
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@captainslog
I am now in a position to continue with my 48" virgin challenger. This boat is going to be heavy and whilst not a racing boat will be producing quite a bit of torque and power. Therefore in an emergency will require a quick engine cut off in the way of an external loop. It is powered by an SC 60 marine glow with a large 3 blade brass prop. I have seen safety loops for electric powered cut off (easy enough) and petrol/gas also easy enough. but never for a glow engine. apart from attaching the end of the loop to the fuel line (disconnects from carb or filter) I cant see any other way to stop the motor. any ideas appreciated please

thanks keith
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8 September 2013 at 14:39 #5252
captainslog
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@captainslog
8 September 2013 at 14:51 #43606
Paul T
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@pault84577
Keith

Look up SparkOut from DocandDave **LINK**
8 September 2013 at 16:08 #43610
Telstar
Participant
@telstar
Keith Disconnectin the fuel line seems a bit drastic. Could you not incorperate a ON/OFF fuel valve similar to this **LINK** , this could be operated by a safety loop, or with an electronic safety circuit

Cheers Tom

Edited By Telstar on 08/09/2013 16:09:19
8 September 2013 at 18:01 #43611
John Shire
Participant
@johnshire55937
Disconnecting the fuel line as a method of stopping the engine seems more like madness than drastic, what will happen when the free flowing fuel reaches the hot engine or exhaust? I am no expert but I assume that a loud bang followed by a fireball might be expected.

John
8 September 2013 at 18:02 #43612
Dave Milbourn
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@davemilbourn48782
The SparkOut only works for petrol engines but if anyone knows of a small, cheap 5v solenoid valve which we could adapt then there's no reason why it shouldn't work for glowplug motors (somehow ca't bring myself to call them "nitro" motors).
Dave M
8 September 2013 at 19:37 #43619
captainslog
Participant
@captainslog
Interesting thoughts so far, paul I`ve seen a system for sparkout but as dave says that seems to be for petrol/gas with a spark plug. and lol at johns comment. yes john I realised that , which is why I asked for a possible solution. Telstars could be adapted I suppose, by attaching 1 end of the loop to the arm of the valve so that when it is pulled the fuel could be directed to a dump bottle in the hull.( loads of space for 1) This doesn`t seem to be straight forward as I thought. Surely there must be a system that the off shore racing boys use? they cant all be using gas engines. Or even for the smaller engined boys, I would have thought it was a requirement for insurance purposes to race. I dont know never taken an interest in the racing scene. I`ll have to troll my many mags somewhere someone would have explained it thanks all anyway
10 September 2013 at 08:18 #43648
Dave Milbourn
Participant
@davemilbourn48782
You will have to run over water at a frightening speed to use a fuel loop in an operational emergency. The only remote system I can envisage – apart from a solenoid valve in the fuel line – would be to use a servo disc, shaped as a cam, to squash the fuel line when signalled either by a failsafe state or via a second channel of the radio.
Dave M
10 September 2013 at 23:31 #43665
Malcolm Frary
Participant
@malcolmfrary95515
I've never been interested in either I/C or racing, but the simplest solution might be a switcher controling a fuel valve such that both a valid signal AND electrical power were needed to hold the valve open. No signal, switcher cuts, stop. No power, valve doesn't hold open, stop. Or have I missed something?
11 September 2013 at 08:31 #43670
Dave Milbourn
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@davemilbourn48782
Malcolm
Essentially that's what we've been on about, but the main problem is finding a suitable solenoid valve. The failsafe unit we already have. **LINK**
Dave M
11 September 2013 at 11:49 #43671
Malcolm Frary
Participant
@malcolmfrary95515
Theres a bunch of candidates here – **LINK** – most will probably be unsuitable for controling fuel, but an infernal combustion engine needs air as well. Cut the air supply, the motor stops. The devices are generall normally closed, run on 12 volts and want about 1/4 amp to stay operated.

This was pointed out to me by a guy who had had a static diesel do a runaway – the automatic sump oil replenisher had overfilled and the thing was running on the sump oil that it was firing up past the piston rings. The answer was to shove his dust coat into the air intake and run away until it went quiet.
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