Vibration hour meters

Does anyone have experience with the vibration activated hour meters, the ones with the 8 year battery?
Specifically the ENM ones, as sold by Aircraft Spruce (and others): http://www.aircraftspruce.com/catalo...clickkey=49513 I help maintain some vintage aircraft types that don't have recording tachometers, or electrical systems, and I thought these would be good for tracking hours, but we put one in my dad's Tiger Moth, and after about 6 hours of flying the ENM meter showed 14.1 hours. If they're that inaccurate they're worthless, or maybe we got a bad one?

http://www.aircraftspruce.com/cache/...s/10-04782.jpg



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I wonder if they operate when the aircraft shakes in wind gusts while on the ground?

I e-mailed the manufacturer yesterday, and got this back this morning:

The meter can be activated by any vibration.
If the plane sits outside and the wind is blowing and moving the plane it can collect time.
Or if the plane is towed on the ground it can record time.
The loop of wire that was cut when you installed the meter is used to short the meters vibration circuit.
If this loop is reconnected when the plane is not in use there will not be extra time logged on the meter.
Also the time recorded will not be affected by disconnecting and reconnecting this loop.
Some Customer tie it to a toggle switch.

If they're that sensitive I guess they aren't that useful. The Tiger Moth is in a hangar so the wind shouldn't be a problem.



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I have an hourmeter on my boat by the same company that uses an inductive pickup off a spark plug wire. It costs ~$25 and works great!

Quote:

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Originally Posted by martymayes

I have an hourmeter on my boat by the same company that uses an inductive pickup off a spark plug wire. It costs ~$25 and works great!

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Added something similar to my Fly Baby.... acts as a tach when the engine is running, but displays hours when the engine shuts down.

http://www.bowersflybaby.com/tech/tach.html

Ron Wanttaja

mine has the tachometer feature as well but I don't use it because the gizmo is in the engine compartment.

Yet, if you installed that great working $25 hour meter in a certified airplane, the FAA would be all over you, Marty. If there is an FAA certified one built under a PMA and has an STC for your airplane, you could probably pay as little as $300 or more for it. What a bargain!!! What our bureacrats cost us is a sin.

Well, in this case its not that bad. Aircraft Spruce will sell you a Hobbs meter, which is an FAA approved part (through MIL-L-3971B), for about $75. Then you need an oil pressure switch, which cost $32. So the parts cost is around $110 if your airplane has an electrical system.

I will suggest that the original poster might try wiring the Honeywell oil pressure switch to the hour meter and see if that combination gets the job done. Hmmmm.... I see that the description in the Aircraft Spruce catalog says the switch contacts are normally open. But further digging might find an oil pressure switch that has normally closed contacts.

Update: ACS sells the Honeywell Hobbs 76575-4 which has NO contacts. The Hobbs 76577 has NC (Normally Closed) contacts. Google will find a distributor for you.

Best of luck,

Wes
N78PS

Yabut the OP is talking about a Tiger Moth which has no FAA type design constraints and I'll go out on a limb and assume it has no electrical system, which is probably why the battery powered (non FAA approved) ENM vibrating hour meter was installed.

If the FAA constraints do not apply, and the British Aviation Authority constraints do not apply, then life is easier. That said, if the aircraft is in the US with an Experimental Exhibition Airworthiness Certificate, a log book entry is a good idea.

Now the original poster reported that there is a jumper wire on the back of the unit that enables and disables the vibration sensor in post #3. So routing that wire through a MIL-Spec Hobbs meter oil pressure switch can enable and disable the meter when the engine is run. And the meter has its own internal battery so no airplane electrical system is needed. Make sense?

Best of luck,

Wes
N78PS

I see your problem - it is likely a Chinese meter in an English aircraft. Different systems of measurement, don'tcha know? :)

Nope, both the British and the Chinese use Metric time.

;)