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Other › True reading on a tach?
05-03-2005 03:10 PM  12 years agoPost 1
lloyd

rrKey Veteran

Perth,Australia (South African)

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hi chaps
i bought one the othe day (micro prolux tachometer)but dont know how to use it to get a true reading.meaning does the heli stay on the ground,does one hold the heli by u/carage,do you hover about 1m off the ground and get your mate (not wife) to measure......
dont bite my head off but the instructions only say point and shoot
thanks
lloyd

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05-03-2005 03:31 PM  12 years agoPost 2
rckrzy1

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Hurst Texas

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Did you buy a tach for airplane props? Heli tachs are optical where you
look through a window.



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05-03-2005 04:17 PM  12 years agoPost 3
richie1967_uk

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London UK

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i have a prop one but it works for helis just fine....you need to set your pitch curve at 0,0,0,0 and get someone to hold your heli, spool up and position the tach under the heli wth the sensor point up towards the rotor disc. You can do it on your own if you set your curve so you have -ve pitch across the curve (enough to push the heli firmly on the ground, place the tach on the floor pointing up as before and stand back and spool up. The optical ones (the type you look thru a little view finder and adjust the reading until the blades seem to stand still) are better as you can read your head speed while performing manouvres (with help ofcousre) but for someone like me (not 3D capable yet) the prop one works fine....

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05-03-2005 04:44 PM  12 years agoPost 4
vertolfan

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Bloomington, Illinois

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What good does it do you to tach a machine at 0 degrees pitch?

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05-03-2005 04:50 PM  12 years agoPost 5
richie1967_uk

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London UK

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it is the head speed you are measuring...in my case i run governor mode so the headspeed remains the same whatever the pitch (in theory) In practice it drops a couple of hundred rpm with a sudden input of full pitch....

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05-03-2005 05:03 PM  12 years agoPost 6
lloyd

rrKey Veteran

Perth,Australia (South African)

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hi chaps
all i said to my LHS is that i a would like a tach for my heli.....and thats the one i got.dont know if its a plane or heli one.what i do know is that i did see one on modefos site that looks like mine....
thanks for the info richie1967_uk
lloyd

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05-03-2005 05:05 PM  12 years agoPost 7
steph280

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Irvine, California

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0 pitch doesn't represent real world value since no matter how hard your ESC governor trys to hold the headspeed, it will be different under load. You could give it negative pitch on the ground and take measurement that way.

To get your hovering RPM, just leave the tach on the ground under the shadow of the blades. Careful not to place it too close to the center of the shadow since it will pick up flybar as well.

For measuring inflight RPM, you will need a dedicated heli optical tach.

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05-03-2005 05:22 PM  12 years agoPost 8
steph280

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Irvine, California

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This is a heli optical tach. You look through the viewfinder on top, adjust the speed until the blade looks stationary, then the speed will be displayed on the LCD.

This is a regular airplane tach. You just point at the spinning prop and reading shows up on the display:

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05-03-2005 05:32 PM  12 years agoPost 9
lloyd

rrKey Veteran

Perth,Australia (South African)

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hi stef280
then i guess mine is a plane tach.you point and shoot.are the other tachs expensive?
thanks
lloyd

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05-03-2005 05:43 PM  12 years agoPost 10
rckrzy1

rrElite Veteran

Hurst Texas

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I think the model avionics heli tach is the cheapest now, maybe $80 USD , my MA tach was $140 I think.



Wildcat Fuels

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