Cheap optical tach...

dans2992

dans2992

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Dans2992
Anyone know the cheapest optical tach that would work for a 3-bladed single from inside the cockpit? I want to check my mechanical tach and see if it's accurate.

It could be intended for aviation use (or not) I don't care as long as it works.
 
I have a prop tach...not really cheap...but it's worked flawlessly for about a dozen years.
 
I had good success with the Engine RPM app on my iPhone. Found it mapped very well to my tach. It might cost a few bucks but it's probably the cheapest option.
 
dans2992 said:
Anyone know the cheapest optical tach that would work for a 3-bladed single from inside the cockpit? I want to check my mechanical tach and see if it's accurate.

It could be intended for aviation use (or not) I don't care as long as it works.
Click to expand...

You want to borrow mine? Pay postage and you're welcome to use it.
 
GeorgeC said:
http://www3.towerhobbies.com/cgi-bin/WTI0001P?I=LXPT31&P=8
Click to expand...

Hmmmm..

You have bigger balls then me....:redface:..

FEATURES Durable ergonomically-designed, durable black case with rubber bumper
strip increases ease of use and durability.
Includes two pre-installed "AAA" batteries
Auto-OFF after 5 minutes, if not in use.
One-touch switch operation with a protective ring that prevents
accidentally switching the unit ON in the Field Box
Operating range 0-32,000 RPM
Measures 2-, and 3- Bladed props
Can be used up to 12" away from propeller
Large easy-to-read .5" (13mm) LCD display
One Year Limited Warranty through Hobby Services beginning at date of
purchase
 
iflyvfr said:
I had good success with the Engine RPM app on my iPhone. Found it mapped very well to my tach. It might cost a few bucks but it's probably the cheapest option.
Click to expand...


Wow, interesting app. I may try that. So it really did work?
 
Are you friendly with your mechanic? He probably has a Trutach or similar in his hangar. To buy a good optical tach will cost you close to $200 for 30 seconds of use. Borrowing is a better plan for most guys.
 
Stewartb said:
Are you friendly with your mechanic? He probably has a Trutach or similar in his hangar. To buy a good optical tach will cost you close to $200 for 30 seconds of use. Borrowing is a better plan for most guys.
Click to expand...

Or the OP can have his prop dynamically balanced..

Win /Win

He/She get's a smoother running motor,,, AND,, a very accurate Tach check..;);););)
 
dans2992 said:
That's for model aircraft and can be used "up to 12 inches" from the prop. I found those already, but ruled them out. Thx.
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I bought one.....and it doesn't work on a prop. It requires applying reflective tape....and the distance is just to far removed. It works on things like fans or other turning items where you can be 12-18 inches from the moving surface.
 
Stewartb said:
Are you friendly with your mechanic? He probably has a Trutach or similar in his hangar. To buy a good optical tach will cost you close to $200 for 30 seconds of use. Borrowing is a better plan for most guys.
Click to expand...

I use mine almost every time I fly to set cruise power because the error of my tach fluctuates with the temp. This time of the year it can be dead on (or maybe not). In the winter it can be 25 to 50 rpm low.
 
Ok. My partner is going to fly it up to our shop tomorrow and borrow the mechanic's tach. Thanks anyhow!
 
At night put an airport streetlight to your backside and the prop will appear to stop at hmm, three blade? 60 cycles per second is 3600 cycles per minute, divided by 3 is 1200 (and will stop again at 2400). No need to buy anything!
 
Mine worked fine for me from inside a PA28. YMMV, some restrictions apply, not a guarantee.

dans2992 said:
That's for model aircraft and can be used "up to 12 inches" from the prop. I found those already, but ruled them out. Thx.
Click to expand...
 
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coloradobluesky said:
At night put an airport streetlight to your backside and the prop will appear to stop at hmm, three blade? 60 cycles per second is 3600 cycles per minute, divided by 3 is 1200 (and will stop again at 2400). No need to buy anything!
Click to expand...
ok....do that again at 2,700 rpm and tell us whatcha get. :goofy:
 
I had a really nice Optical tach made by Stihl. It was a hand held unit. You just pointed it at any spark plug and it would give RPM. Worked on any size engine.

Someone needed this more then I and today its gone. I purchased this through stihl some 15 years ago when I was working. Today I cannot find one of these. I have seen other makes and models, but these have not performed like that Stihl unit. Stihl had all their techs use one of these when setting up or repairing any stihl chainsaw. Its really the only way to get those little engines set perfect.

If I ever come across this tach I will post it. I have not gone into the stihl dealer and tried to find one. But one day I will. Its not really cheap, it cost over a 100 bucks. But you get what you pay for.

Tony
 
A friend the other day told me to put a light bulb in front of my prop and my prop would look still at 1200 rpm's. I am worried about my tach being correct. He explained why and all. I thought if it works at 1200 rpm's it will work at 2400 rpm's. Is this correct? What will happen at 2700 rpm's? I am getting ready to do this test in the next couple of days.

Tony
 
1600vw said:
A friend the other day told me to put a light bulb in front of my prop and my prop would look still at 1200 rpm's. I am worried about my tach being correct. He explained why and all. I thought if it works at 1200 rpm's it will work at 2400 rpm's. Is this correct? What will happen at 2700 rpm's? I am getting ready to do this test in the next couple of days.

Tony
Click to expand...

Your friend didn't explain it very well. "Light bulb" has to be a fluorescent as it "fires" 120 times a second working from house power. It also has to be at night or in a VERY dark hangar. And it is better if it illuminates from the BACK side so you can see it from the pilot's chair.

More better you go back three or four answers and see the comment about the airport ramp or street light. That way you don't need any extra lights.

Jim
 
coloradobluesky said:
At night put an airport streetlight to your backside and the prop will appear to stop at hmm, three blade? 60 cycles per second is 3600 cycles per minute, divided by 3 is 1200 (and will stop again at 2400). No need to buy anything!
Click to expand...

As I vaguely recall, the light fires on both the positive and negative half-cycles so it is 7200 strobes per minute.

Jim
 
dans2992 said:
That's for model aircraft and can be used "up to 12 inches" from the prop. I found those already, but ruled them out. Thx.
Click to expand...
I have a similar type of unit, mine works from the cockpit. Use it every conditional inspection. Doesn't require special tape on the prop or anything.

Ron Wanttaja
 
It's just amazing...you can do just about anything with your freakin' phone these days!
 
The streetlight thing works. Put the streetlight to the BACK of the airplane. It has to be a fluorescent light, and most are. There are different kinds of lights, but the light I used made the appear to stop at certain rpms, I believe it was a 2 blade prop, that one goes at 1800 etc. Just try it, 1200 an 2400 will be the magic numbers for a 3 blade. If that's wrong, let us know what happened and where it DID stop and well figure it out. Some bulbs may flash twice a cycle, which will change the numbers but the concept will work, just have to get the numbers right. If it flashes as some odd amount like 2300, that is an indication that the tach is really going 2400 when it indicates 2300.
 
I have an "RPM from Sound" program on my computer that was free on the internet, I think it was on this web site, several years ago. It works fine if your laptop has a mike. It is probably a precursor of one of the apps for cell phones that people have mentioned. If you want, PM me your email and I'll send it to you.
 
coloradobluesky said:
The streetlight thing works. Put the streetlight to the BACK of the airplane. It has to be a fluorescent light, and most are.
Click to expand...

Ehhhhh...sort of...fluorescent lamps indeed use Mercury vapor, but streetlights are H.I.D. lamps and can be Mercury vapor, high or low pressure sodium, metal halide, or some other, less common lamps. While they are similar in concept to fluorescent, I don't think they're considered fluorescent.

All an aside, of course.
 
timwinters said:
Ehhhhh...sort of...fluorescent lamps indeed use Mercury vapor, but streetlights are H.I.D. lamps and can be Mercury vapor, high or low pressure sodium, metal halide, or some other, less common lamps. While they are similar in concept to fluorescent, I don't think they're considered fluorescent.

All an aside, of course.
Click to expand...
I have done the "streetlight" thing 30 years ago and it worked... Most of my planes had 2 blade props and the U.S standard is 60 cycles a second, So any multiples of 60 will give the strobe effect....

Also, back then streetlights were incandescent light bulbs...
 
poadeleted20 said:
I've tested "head speed" apps for smart phones against electronic tachs, and it's always been dead-nuts on. For Androids, here's one I know works.

https://play.google.com/store/apps/details?id=at.idsoftware.headspeedtach&hl=en

Maybe the best three bucks I've ever spent. Note that it includes a "number of blades" setting.
Click to expand...

+1 on Headspeed Tachometer. Run it on my Android tablet mounted on the yoke. Since it analyzes the propeller sound there is no need for it to actually see the prop.
 
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