bcripe

Has anybody tried the iPhone tach, Engine RPM? In the ap store? Just curious of how it is before I buy a goo bee.

thanks!
BC

steve111

Yes, I use it all the time (in fact I don't bother with my regular tach any more since getting it). It gives identical readings to a good Fromeco tach that a friend has. It doesn't care about light conditions, and you can tach your engine with the model in flight. It doesn't cope well with a diesel that's set in a misfire, but perfectly good otherwise.

aspeed

Maybe I am showing my age, but what is a Goo Bee? There are also Apps for a decibel meter. I have been thinking of getting a cheap mini Ipod or pad or whatever, just for that. Not really into the phone thing.

bcripe

I meant glo bee. The great planes tach. http://www.amazon.com/Great-Planes-G.../dp/B001BHK650

bcripe

Thanks Steve. Is it pretty easy to set up? It just listens to the engine? I want to use it to set up a couple of four strokes.

steve111

Yes, it just listens to the engine. The display shows a waveform with big spikes where the harmonics are, and there are red index lines which lock onto the harmonics. (You may need to swipe l/r to set the approximate ballpark rpm so the index lines will lock on.)

The 'Help' button explains it all pretty well, but for the settings I use harmonics 1-10 and 'track rpm' 20%/sec. You can select the number of cylinders, and 2/4 stroke.

All of that sounds like complicated gibberish, but once youve done the initial setup to your liking, all you have to do is swipe the rpm to about the right reading to lock on to the harmonics (quite obvious and easy in practice).

1QwkSport2.5r

Curious what app exactly you're talking about. Anyone got an app name I can look up?

steve111

"Engine RPM" (as per the first post). Not sure if there's an Android version or just iOS.

1QwkSport2.5r

It wasn't noted specifically that was what it was named. It is now. I'll check it out. Thanks.

downunder

Steve, have you tried it out with an engine doing a 4-2-4 break? I'm guessing it should also work with youtube videos where guys run them on a test stand or maybe even flying videos. I've done something similar by recording sound from a video using Goldwave then slowing it down 100 times and counting the peaks over a few hundredths of a second period. It's interesting playing back the sound at that speed because you can hear each individual exhaust pulse kind of going flub-flub-flub . The photo shows the peaks in my son's car engine and counting from the .03 second mark to the .07 mark there's 19 peaks so it was doing 28500 revs. I did the same thing once with that famous CL world speed record which ran 19000 on release but jumped to about 37000 after the pipe cut in. I had to be careful with that one though to avoid any Doppler shift.

aspeed

Wow, I am from the stone age. I did use a digital guitar tuner to check RPM. It would give the note, b, b flat or whatever, and then I would look on the chart. You could be out half , or double if you have no clue where it should be. I checked one of Carl Dodges flights, averaging the high and low readings, and I figured either 20,000, or 40,000 rpm the one time. Each octave is double the rpm. Downunder's speed record motor check doubled when on the pipe too. The pipe controls the ground and air rpm. The control line planes are best checked from inside the circle if possible. You can tell the laps from the louder and quieter differences, but the Doppler isn't there.

steve111

Hi Brian, "yes" in both cases. It works a treat with YouTube videos; it's also interesting to tach your CL model in flight from the centre of the circle.

1QwkSport2.5r

I guess my only question is this app really worth $9+tax and will it be accurate enough all the time to just leave my Hobbico each at home?

aspeed

Surely there must be another place with a free app. The decibal meter had a few free ones, as well as paid ones.

bcripe

I downloaded it and am running on auto. 4cycle 1 cylinder. It's pretty jumps up and down about 500 rpm. I'm going to try the more advanced settings later today.

steve111

Good question. It'd be fair to say that it's an expensive app but a cheap tach. For my purposes it completely replaces my regular tach (with a few additional advantages), and I'm entirely satisfied with the accuracy, so it's definitely worth it. Other people may find different. For example, if you do a lot of testing of 4-strokes where you're varying rapidly between high power and idle, I suspect it wouldn't do as well as a regular tach.

flyoz

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Interesting app I especially like the Manual match RPM great way to tune by ear (and increase your mental sound recognition skills )

SuperNash

I've used 'rc-tachometer' for android. It works ok. Fairly slow response to engine speed changes but easy to use. Much the same to operate, tell it low rpm and high rpm, and engine type, and it does the rest.