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Gas Powered Thoughts Advice for Gas Helicopter Success from Carey Shurley


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Old 11-05-2012, 09:32 PM   #1
carey shurley
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Default Field Accessories - Model Avionics SkyTach



A useful tool to have at the field is a head speed tachometer. If you're wondering why you probably haven't struggled with setting up throttle curves or setting the RPM on a governor that doesn't have any sort of RPM display. Even with a governor you need a way to fine tune the setup

If you have onboard telemetry, you can collect this data with your telemetry system. If not, you need an RPM tachometer of some sort

There are a few options, I'm going to show you the SkyTach from Model Avionics (the same folks that make the Throttle Max governor)

So here's the Skytach, its a small plastic box that includes everything


The Model Avionics SkyTach

You'll get the tach plus an operation guide.


Whats in the box

So if you've never seen or used one of these, you may be wondering how it works. The key is this rotating shutter.

By varying the RPM that the shutter rotates, it provides an optical tool to determine the RPM of the rotor head.

you hold the tach up to your favored eye and sight through the lens and the shutter at the rotor head of your model while it is running. The speed of the tach can be adjusted up or down using the rocker switch on the right side of the tach. When the blades appear "frozen" the shutter speed matches that of the rotor head (two bladed head)

To be fair, you can't do this effectively while you are flying the model so you'll need someone to help with taking these readings


RPM Shutter

The unit does NOT have an on/off switch that can be accidentally left or turned on. Instead the unit turns itself off after 30 seconds of non-use and turns on when you move the rocker switch in either direction

the unit will power up at the last RPM that you were reading. Note that the readout is only 3 digits, the least significant zero digit is left off. So any reading you see would be multipled by 10.

In this case the unit powered up reading 1650 RPMs, the last reading taken


Power up at last RPM

The slowest RPM the unit will read is 1000 rpm, more likely for scale type helicopters


Minimum RPM Supported

and the highest RPM the unit will read is 3190 RPM. At least in todays terms thats high enough for all but extreme performance micro/mini helicopters


Maximum RPM Supported

The unit has a rated accuracy of +/- 2.5 RPM which is well within the 10 RPM readout capability.

Video Overview



The Bottom Line


Unless you have onboard head speed RPM telemetry with a live downlink, you at least need access to an RPM tach. Its valuable not only for setup but for ongoing tuning of your throttle and pitch curves.
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Old 11-06-2012, 12:40 PM   #2
MotorRotor
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I have found this tach to work very well on helis from 250 size to my big gassers.
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Old 11-07-2012, 07:27 PM   #3
Mr.HillBilly
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I have used the SkyTach and it worked great but I never picked one up.

I was at a FunFly and I found one of the HobbyKing versions brand new for $15 so I picked it up.



It is a basically a clone BUT it is slow on the speed up and the slow down when you are trying to find the HS and you end up overshooting and then you undershoot. You can get good readings it just takes longer. They have a LCD shutter version now that I figure would work a lot better since there are no moving parts but I have never seen it yet.

It does not have a power switch also but it will kill the battery even if you have it sitting on a table without anyone touching it.
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