LeoTao

Hi guys:

I just want to know how did you do to accurately measure the rotor speed ?

I heard a optical tachometer called Magic mirror tachometer can do this, everybody knows?

chris6414

My Feedback: (10)

Get a airplane prop tach and strap to the boom. May work.

ATVAlliance

Guy in one of the clubs Im in has some type of tach that you look through like binoculars.  Im sure its a pricey thing though.

It can give rotor speed while a heli is hovering 30 feet in the sky and say 100 feet away.  Really neat, but like I said...Im sure its kind of pricey.

BarracudaHockey

My Feedback: (11)

Optical Tach

http://www.heliproz.com/prodinfo.asp?number=804260

ATVAlliance

Not as pricey as I thought, but still pricey enough.

Thats the exact one he has...or at least looks very similar.

madmorgan

My Feedback: (2)

whats the matter arent the head speed calculators good enough?  they have to be pretty close !

ATVAlliance

You would have to see one of these handheld optical tachs. Its just neat! Plus a big time saver too, especially for glow powered like a Raptor.

1. Start heli
2. Adjust carb
3. Hover and use optic tach
4. Land heli...tweak carb
5. Hover and use optic tach
6. Land heli...tweak carb
7. rinse repeat till done

All the while never having to kill the heli and restart it.

Not to mention the safety factor.

Ive never used the head speed calculation...so cannot comment on it. But I will say that Iwould think that any type of mathmatical formula/calculation is only going to be accurate if your motor/ESC is performing EXACTLY as spec'd. Over time if motors get weaker....and batteries too....your result could be off.

I think I"ll stick with a tach...maybe not one as costly as this. But then again 90 bucks. Not that bad when I think of how much easier it would make getting a headspeed reading, and safer too! My last trip to ER to get 5 stitches in my hand still cost me almost 300 bucks after insurance! LOL

LeoTao

the magic mirror tachometer looks pretty good.


Features：

â–* RPM Measurement Range: 800~4200RPM

â–* 4ï¼�digit LCD screen display

â–* Accuracy: +/ï¼� 1 RPM

â–* 10 Level aperture adjustment

â–* Ultraï¼�wide viewing angle

â–* Highï¼�speed electronic shutter

â–* Shut off automatically after no operation for 30 seconds.

â–* Power supply: CR2032/LIR2032 button battery

â–* Operating Battery Drain: 3mA, Idle Drain: 10uA

â–* Low Battery alarm

â–* Weight: 40g

ATVAlliance

Thats a nicer looking one...but cheapest I found was on ebay @ 117 bucks shipped.

Thats a lot of money...and to be honest I have only tach'd my helis a couple of times. I use my handheld tach to tune my glow and gas planeengines idle speed for the most part.

If I had an optical "sky" type tach...Id probably use it though. Just hard to tach 450's and larger safely with a handheld tach. Always thought about making some sort of heavy base that would hold the tach firmly on the ground pointing at the sky and just hover right over top of it in idle up to check...just never made the effort to make a base.

madmorgan

My Feedback: (2)

well i guess if your running nitro or gas you would need it but electric using the calc its almost spot on, as long as you get the data in correctly.

ATVAlliance

True to a point. But how can you be sure the battery pack is putting out the same current it says it is. Over time packs get weaker and ultimately will need to be replaced. Same thing with the motor. Id say ESC has the least to do with it unless it burns out something and doesnt pick up the correct cell count or something of the like.

The "math way" will work if ALL of the variables remain the same. Probably most accurate when everything is brand new out of the pack. I would "guess" that over time your results wouldnt be accurate unless you used a tach. This is just my guess though as I have never used your method or seen it. Would definitely be interested in seeing the formula and what variables you enter into it to see if my thoughts ring true.