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CarbonXtreme . Midland Helicopters . HeliProz

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Tools and Field Equipment > tachometer optical vs digital?
 
 
Screwhead
Heliman
Location: Tucson Arizona USA

My Posts This: Topic  Forum		The optical tachometers seem higher in price though we use it to "see through" the hole to come up with the rpm? It sounds more cumbersome to get the rpm while a digital tach reads the rpm automatically at a touch of a button. Why the optical tach is consider better (if so?) and people prefer the optical to the digital? For example this costs only about $25 http://www.helidirect.com/hobbico-l...eter-p-2215.hdx and fully automatic and seems easy to use, but this popular optical tach http://www.helidirect.com/model-avi...eter-p-7027.hdx is $85, three times as much, and doesn't read the rpm for you automatically. You must "see through" it to get the rpm, then yada yada yada. Thanks.
10-26-2009 10:53 PM
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FlaG8r
Elite Veteran
Location: Florida

My Posts This: Topic  Forum		This is why you don't want to use the digital tach, from the comments
"Hold tach 4 to 12" away from propeller"


Tough to do that when you're hovering and the blades are spinning at 2100 RPM.

Life is tough, it's tougher if you're stupid
www.jaxrc.com
10-27-2009 01:58 AM
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Screwhead
Heliman
Location: Tucson Arizona USA

My Posts This: Topic  Forum		Doesn't the optical one also require the same holding, aiming, etc while hovering whereas with the digital at least you aren't required to see through it. I've never used a nice optical one, but if the optical one is somehow superior, I'm willing to invest in one. I've heard a skilled person can just hear and tell an approximate RPM, which off course I can't do that.
10-27-2009 05:24 PM
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Farrell
Senior Heliman
Location: Huntington Beach, CA

My Posts This: Topic  Forum		A regular tech needs to be close to the prop or rotor to give you a reading... it uses an IR sensor to look for "flickering" light... light that is obscured by the prop or rotor blades with each rotation. That is not practical for heli use as you can't safely take readings.

A optical tach is used on heli's, and you look through the hole in the tach and make adjustments until your rotor disk appears stationary.

I think Thunder Tiger used to make a regular tach that could be secured to your tail boom. No need for an expensive optical tach and no need to put yourself in harms way while using a regular tach... but it was a weird way to check headspeed. You had to look at the LCD on the tach / tail boom to get a reading, so it would not be very useful except to check hovering headspeed. I'm not sure if their tach is still available, I don't think it was very popular.

-Farrell
10-27-2009 05:59 PM
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Heli_Man_Bob
Senior Heliman
Location: Miamisburg, Ohio, US

My Posts This: Topic  Forum		How would you be checking your head speed with the Heli hovering inverted with the non optical Tach.

Why an opticle tach? Safety is the reason as well as more capability.

With the optical tach you can observe the model in all modes of flight from a safe distance.

You do not operate the optical tach and heli by your self this is a two person task.

You don't necessarily have to own one just need to know someone who has one and will offer to tach your Heli.

If you intend to be in this hobby a while its a worth while investment.
10-27-2009 06:07 PM
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HeliFisher
Veteran
Location: Verdi , Nevadafornia

My Posts This: Topic  Forum		Try this......

Have your buddy lift off into a steady hover. Now walk over to the hovering heli and hold your hand 4-12 inches from the main rotor.

I think the laser tach is for airplane props, where you can go full throttle and hold the plank (or plane) stationary while you tach the propeller. The optical tach allows you to remain a safe distance from your heli, since we need to be in a hover to get an accurate headspeed reading. You can also see the rotor disk bog with the optical tach. I dunno how useful that would be to see the bogging, but it looks cool!

I have found the headspeed calculators are very accurate as long as you enter all the proper numbers, as far as motor efficiency and that kind of thing.

The less a man makes a clarative statement, the less likely he is to look like a fool in retrospect.
10-27-2009 06:14 PM
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greenboot
Veteran
Location: St Louis, Mo

My Posts This: Topic  Forum		It may be clearer when you understand what the optical tach does. It contains a spinning disk with a slit. You sight through the spinning disk and adjust it's RPM until the rotor blades appear stopped. At that time, the disk and your rotor are turning the same speed. Now you can read the RPM of the disk on the display. The heli can be VERY far away and it works fine. Of course you need a second person to operate it.

Tom
10-27-2009 08:20 PM
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JRjoe
Elite Veteran
Location: Portage, IN USA #1

My Posts This: Topic  Forum		That cheap Hobbico tach is for planks. If you want to know rotor head speed you need an optical tach and a helper. No real way around it.


JRjoe
Indoor plumbing??? No, we don't need that!!!
10-28-2009 02:42 PM
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GyroFreak
Elite Veteran
Location: Florida ... 28° 52' N 81° 16' W

My Posts This: Topic  Forum		Get an Eagle Tree on board data logger. Then you have a record of your rpm all through the flight. No need for a 2nd person and it is about the same price.

Bacteria They're the only culture some men have
Growing old is mandatory; growing up is opti
10-28-2009 02:52 PM
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Screwhead
Heliman
Location: Tucson Arizona USA

My Posts This: Topic  Forum		Thank you very much folks. You gave me lots of helpful hints and information regarding my possible purchase of a tach. I'd probably scratch the idea of digital tach. I have heard that reading of the rpm with an optical tach may take 2 persons. I'd also read about the Eagle Tree on board data logger. I may consider that if not expensive. If the logger is expensive however, I shouldn't get it because I may crash and break the whole heli including the logger.
10-28-2009 10:05 PM
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Screwhead
Heliman
Location: Tucson Arizona USA

My Posts This: Topic  Forum		Hi, this review of Eagle Tree data logger says there are types of RPM sensors available.

http://www.rchelisite.com/eagletree...gger_review.php

The optical "second" type is being said not usable for measuring the heli headspeed, which works in the similar manner as the digital tachometer, as you explained to me (therefore not great for helis.)

Which would you think better between the electronic RPM sensor "third type" (to be put between the ESC and motor) and the magnetic "first type" (a physical sensor installed near the rotor blades) better? The article recommends the third type.
10-28-2009 10:26 PM
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OICU812
rrProfessor
Location: Grande Prairie, Alberta, Canada

My Posts This: Topic  Forum		"IF" you want to consider a fantastic sky tach look at the western robotics chinook. Brushless motors, large window, they work a treat I really enjoy mine!

...Once upon a time there were Nitros, flybars and frequency pins...
11-05-2009 08:00 AM
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Smok
Heliman
Location: Antwerp, Belgium

My Posts This: Topic  Forum		There is also a third option - a governor or speed controller
which allows to set the RPMs in all idle-ups.

Futaba GV-1 can do that and also CastleCreations Phoenix controllers.

Both work fine for me ..

Smok
11-05-2009 11:43 AM
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HeliFisher
Veteran
Location: Verdi , Nevadafornia

My Posts This: Topic  Forum		Also......

If you have an I-phone, you can download a tachometer app. I used my buddies the other day and it worked well.

The less a man makes a clarative statement, the less likely he is to look like a fool in retrospect.
11-05-2009 08:25 PM
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Screwhead
Heliman
Location: Tucson Arizona USA

My Posts This: Topic  Forum		Hi, The western robotics chinook have been mentioned in my research to look for a good quality optical tach. OICU812, your comment confirms that. Thank you. I'm leaning toward the Eagle Tree data logger that some of you mentioned. Thank you for useful recommendations, folks.
11-06-2009 04:35 AM
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Tools and Field Equipment > tachometer optical vs digital?
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