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How to wire in a Hobbs meter correctly.

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  • Gary Taylor
    replied
    Do yo think this will work, if so it’s sooo simple

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  • Mike Cowlishaw
    replied
    How to wire in a Hobbs meter correctly.

    > Mike's suggestion is just idiotic, as most of the engine wear will occur before the oil temp reaches 50°C, yet his Hobbs meter won't even have started yet. There's a word for that Mike: Fraud!

    Well, I thought the idea was to log the flying hours, not the engine hours. Original poster might want to clarify his or her intent....

    But yes, maybe a trolley that's dragged along with the aircraft (big wheels, heavy), stays on the ground when the aircraft lifts off, pin is pulled out (insulator between two brass strips) and that starts the Hobbs? Avoids the wind problem, but (sadly) also avoids sealing wax and string.

    Mike

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  • Alan Batchelor
    replied
    How to wire in a Hobbs meter correctly.

    Running the Hobbs via a mag switch won't work as you'll miss vital seconds of every flight whilst you do your mag checks!
    How about installing an oil pressure switch and running it off that?

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  • Guest's Avatar
    Guest replied
    How to wire in a Hobbs meter correctly.

    talk about getting over complicated.

    A SPDT mag switch wired so that the common (centre) connection is the ground. One end terminal is connected to one of the mags, as usual, the other end is the ground for the Hobbs. The live for the Hobbs comes from somewhere that is live when the battery master is on.

    Voila! master on and mags on runs the Hobbs meter.

    It doesn't matter which mag switch you wire it to or even if the Hobbs connection goes to both mag switches.

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  • Guest's Avatar
    Guest replied
    How to wire in a Hobbs meter correctly.

    If you connect two wires from the generator (yellow wires) into a bridge rectifier and a 12volt regulator (78 series) the output goes to the hobbs meter. Therefore, when the engine is running approx 24-18volts ac from the generator, rectified to 12volts dc, and on to the hobbs meter. Only 3items, all from maplins and cost less then £2.50. simple….

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  • Guest's Avatar
    Guest replied
    How to wire in a Hobbs meter correctly.

    I think that the problem with that would be that wiring to the output side of the regulator is like wiring direct to the battery, unless you use diodes... the cable works both ways otherwise!
    Simplest solution is definately the microswitch on the prop arrangement, with an DPDT switch on the mags coming in a close second. Mike's suggestion is just idiotic, as most of the engine wear will occur before the oil temp reaches 50°C, yet his Hobbs meter won't even have started yet. There's a word for that Mike: Fraud! :rofl:

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  • Guest's Avatar
    Guest replied
    How to wire in a Hobbs meter correctly.

    I haven't read all of this thread, so forgive me if this has been mentioned before, but surely the simplest way is to wire the hobbs meter straight to the regulator? That way it would only get power when the engine is running. No, thats too simple, i must be missing something!

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  • Mike Cowlishaw
    replied
    How to wire in a Hobbs meter correctly.

    Ah yes, I forgot to mention the automatic airbrake on the turbine that only releases when the oil temp. gets up to 50'C ... [IMG]/forums/emoticons/smile.gif[/IMG]

    It's a piece of thread tied to one blade of the fan, fastended to the crankcase at the other end with sealing wax. Only a tiny blob needed before each flight, and when the wax melts the thread winds up around the turbine shaft and hence is neatly stored during flight.

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  • Guest's Avatar
    Guest replied
    How to wire in a Hobbs meter correctly.

    That's ridiculous Mike! Imagine that you parked in a windy spot for a couple of days... You'd be due a 50 hour service and a new wing spar by the time you got back to it!

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  • Mike Cowlishaw
    replied
    How to wire in a Hobbs meter correctly.

    Hmmm, how about a small wind turbine (fan driving a generator) mounted aft of the propeller. When the propeller is turning, the airflow spins the turbine that then generates power that runs the Hobbs meter.

    Downside is that after an engine failure in flight you'll still get charged for engine hours .... :-(

    Mike

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  • Guest's Avatar
    Guest replied
    How to wire in a Hobbs meter correctly.

    Rick, you're not taking this seriously are you. Now that's just being silly isn't it :yeah:

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  • Guest's Avatar
    Guest replied
    How to wire in a Hobbs meter correctly.

    :lol:

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  • Guest's Avatar
    Guest replied
    How to wire in a Hobbs meter correctly.

    How about this?

    http://shop.airworlduk.com/powergeni...id=63160226708

    John

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  • Guest's Avatar
    Guest replied
    How to wire in a Hobbs meter correctly.

    You're all going about this wrong. What you need is a microswitch attached to a prop blade, with equal weights applied to the same position on the other blades to keep everything in balance (obviously). Then you attach a small weight to the trigger of the microswitch so that as the prop spins, the centrifugal force operates the switch. Then, a simple commutator type arrangement at the prop hub will allow you to operate the Hobbs meter. The beauty of this system is the simplicity with which one can alter the weight on the microswitch to operate it at different revs!

    Genius. Pure genius.

    Carry on.

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  • Guest's Avatar
    Guest replied
    How to wire in a Hobbs meter correctly.

    Hmmmm.

    DPDT would actually have 3 positions wouldn't they Conrad? Wouldn't the centre position have them both off (which would actually be on for the mag). I didn't think of that but the DPST method makes the throw the same as the other one which is unobtrusive.

    Suppost it goes to show there are more than one ways to skin a cat! You inspired me whatever your suggestion. :smilewinkgrin:

    Cheers

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