Bought a hobbico tachometer from a local hobby shop. The guy in the shop showed me it worked by pointing it toward a duct fan in the ceiling. Took it to the field and can't get it to work with a Super Tigre 90 running a APC 13 X 6 prop. Someone at the field stated I needed to paint the prop tips? What's the story on why this doesn't work.....

Mini Tachs work by light interuption of the sensor, maybe you just had too much/too little light as a contrast to the prop. You shouldn't have to paint the prop tips. When using the Tach try to have the plane at an angle to the sun but not as far as 90 degrees, take the readings from about 3-4" from the prop, looking into the prop arc from the rear of the plane just to be on the safe side.

As Merlin has said: point the tach at the prop from behind the engine for safety. Try having your model in the shade, with the front of the model pointed in the direction of the sun.

Also on that Hobbico tach,make sure you have the correct number of blades punched in.After you press the on button continue to press it until the number of blades your prop is.2 or 3.Try and put the sun at the rear of your plane and take a reading from front,or sun at the front of the plane and read from rear.

NEVER take a tach reading or do ANY type of engine adjusting FROM THE FRONT! Here's your sign!

Dr.1

Absolutely. NEVER EVER do anything in the front or the sides of a running motor. Props can and do break or come off. You don't want to be in the path of one that gets thrown. Always stay away behind a running motor. See attached diagram.

First thing on the tach is to test it to make sure it is working properly. Turn it on to the two blade setting and point it at a fluorescent light, it should read 3,600 RPM. The reading may differ, but the reading should be a multiple of 60 (this is because your electricity runs at 60 hertz and a fluorescent light actually "flashes" on and off with the electricity. And yes, other countries run their electrical current at 50 hertz). If the tach is working properly then you should do as stated above. Take the reading from behind the prop, and try to have the sun on the other side of the prop.

Hope this helps

Ken

Strange how you have to start the plane in the danger area.[X(]Sorry for the misinformation,I guess I just don't know any better.

Don't be a smartA, BANJO. If you've ever been in the area of a flying prop or a runaway plane, you wouldn't make jokes. Although you DO need to be in the danger zone to start the plane, REALLY smart pilots quickly move to the rear to do any adjustments.

However, if your engine will start with a chicken stick, and you can reach the prop around the fuselage/cowling, the engine CAN be started from the rear.

Also, several years back, a device was developed that held an electric starter in place in a stand. The pilot held the plane with the spinner pressed into the starter cone, and the starter was triggered with a footswitch.

Dr.1

I admit I made a statement that was incorrect.My bad.However I didn't deserve the disrespect of Here'S Your Sign.I'll shut up now.I did not intentionally offend anyone.

With my tach, I find I get better results on sunny days if I point the plane away from the sun and check from behind the plane. I do not paint any blades.

I have my own Question I'm using a Hobbico mini tach one of the ones with the button on the side well last year the batteries died and i pulled them out now I can't find them and don't know what kind they are LOL i lost the old ones the new has AAA but this i thought had button type but what size? AS far as you question lighting has a lot to do with how it reads, somes getting close I dare helps it read better, face it towards the brighter light source and the shadow of the prop will do the rest be sure settings are correct for 2 & 3 Bladed props

My Hobbico Mini Tach has a single 9V battery in it.

And Tower shows the new one with AAAs.

Good luck.

So how does one use a tach to tune an engine? Is using a tach the preferred method of tuning?

Thanks.

I don't bother with A tach with smaller two strokes for just sport flying unless it's for something special like racing or I'm really having problems with it.
I do use the heck out of mine on four stroke and gas engines.
I have three of them under A bench that are useless, one very old one and two that everyone has seen advertised and probably have one. I had to finally break down and spend the money on A TNC for all the four strokes I was tuning, sweet!!! Is it worth the money?? Only when I really need it.

I usually use a tach when setting four strokes and gas engines. I also use a tach on two stroke glow engines to check idle speeds. When you lean the high speed needle the RPM increases until it peaks. Then you richen it out a little. It's easy without a tach when tuning a two stroke glow engine because you can hear the pitch of the engine increase and decrease. All engines tune that way, but it can be more difficult to hear minute pitch differences in a four stroke or gas engine because the pitch range is lower. This is where the tach comes in handy since the numbers don't lie.

Thanks Nathan; sounds like a more accurate way of performing the 'pinch test.'

I guess my engine just likes to run RICH. I can never seem to get to the point where you pinch the line and the RPM's stay the same or decrease - it stalls out before it gets there. Every time I pinch it, the RPM's jump up, so I lean it 2 clicks, the RPM's jump again, lean it 2 clicks and it dies. [&o]

I have one of those Hobbico tachs and like it bunches. It has changed the way I tune engines. For the high speed I set the engine to max rpm and then open the needle richer until it drops 300 rpm or so. That's it. A richened out setting that is fast to set and easily repeatable. I love it.

Set the high speed needle first (the big one that sticks out the carb)

Low idle is still trial, error and fine adjustments as always. Run at high throttle for three seconds, drop to low (I have idle-down and throttle cut switched programmed into my 9C), then gun it. If it cuts out suddenly richen the low end (back out the little screw in the carb barrel) and start over (always run high rpm between low end adjustments to get the fuel flowing). If it stutters and hesitates then picks up lean (clockwise) the low end needle.

Life is good. You can still do the pinch test (and not a bad idea) as a secondary check.

Thanks Chuck, I think I'll get a tach

I bought the hanger 9 voltmeter/tach. The tach is sensitive to how you have the sun/shade positioned. At night with the throttle wide open under a spotlamp I was reading 3,000 rpms no matter what. At the field on a nice day it reads fine.

Is there any real diff between the Tower tach and the Hobbico tach?

Towers: http://www3.towerhobbies.com/cgi-bin...&I=LXPT31&P=ML

Hobbico: http://www3.towerhobbies.com/cgi-bin...&I=LXPT32&P=ML

They are extremely similar.

Hi Gray B. Where did you get your TNC tach from?.My search engine doesnt bring back much info.Cheers

i bought mine here,
http://www.darrolcady.com/Accessorie...ies_flight.htm

scroll down a little and it's there..................best money i ever spent.
nice thing about the TNC is that it holds the top RPM reading while adjusting for high end................it shows 2 readings at the same time.

I think, don't quote me on this because this is off the top of my head. I think I got mine from Don's Hobby Shop. You can go direct to www.fromeco.org and cut out the middle man. This tach is so good I can stand five feet behind the aircraft and get A perfect reading.
Eric, I tested my friends H-9 tach/volt one day against mine. The reason was we couldn't get A reading from his at all at the field that was even close to the same from time to time. We found out that under different light conditions and back grounds his tach just wouldn't read. All we had was direct over head sun. Once we got the plane at home and in the shade with some background the H-9 unit was dead on. It just didn't like the desert sun we had that day. Out of the different makes of tachs I have tried the H-9 is one of the better ones and that volt meter comes in handy.

The TNC tach is now made by Fromeco at:

http://www.fromeco.org/Products/05FRCTNC/Default.aspx

For other sources google "tnc tach".

Bruce