hand held tachometers

amtrac

Member
Any way to check the rpm of a John Deere 2 cylinder engine with a hand held tach? After researching on the net for an hour, there seems to be a multitude of different instruments out there. Will any of them work on a two cylinder John Deere? If there is, any suggestions for a quality tool, say under $75 bucks?
 
I have a mechanical one that we used to use to check the rpm of the cylinder on a combine. You simply held the tach against the end of the shaft and the shaft spun the tach.

If you could find something like that, there's no reason you couldn't hold it against the end of the crankshaft.
 
I have a photo-electric one which will work on anything you can stick a little piece of reflective tape on. I don't remember how much it cost.
 
I have one that I bought from Northern Tool & Supply that is a hand held electronic gizzmo with a spring sticking out the end. You lay the spring on the spark plug lead and it reads out the RPMs. Only thing is there is a couple of different scales and you have to figure out which one to read. The deal is you have to figure out if the motor drops a spark on the exhaust cycle or if it fires every other revolution like a car or if it's a two cycle that fires once every revolution. I've used the photo tach at work when we need to verify speed of a shaft for a pump or fan to figure out where we are on the curve or to insure we have the centrifuges running at the correct speed (we had some that had a fluid clutch on the drive and if they got to slipping to much the speed would drop off so we checked speed periodically). At the golf course I had the little hand held with the rubber tip that you put up against the end of the shaft and it read out, worked like an old speedometer. I like the electronic one bst as in a lot of todays lawn & Garden equipment you can't get to a shaft through all the guards.
 
I have a laser one similar to what Bob Bancroft described. I bought it from Snap on 15 years ago, it uses a little square of reflective tape you stick on whatever shaft or pulley you need to measure the RPM of.
Very accurate and easy to use, at the time it was around $400.00.

See lots of them on the internet now for $30-$50 might be worth a try.
 
I purchased a hand held laser tachometer on ebay last year for less than $15. You put a piece of reflective tape on something that rotates and it will give you a reading. For your JD, a piece of that tape on the pulley would do the trick. I tested it against a strobe tach and they were within 2% of each other.
 
I use the reflector tape method and works well on my JD "L". '48 IH Cub and 8n Ford. It is also use on my 9 inch South Bend lathe, drill presses and one milling machine.It keeps the hands out of the moving parts.
 
I usually hold them on the belt pulley cover center. Most models have a dimple there to help center it.
 
I bought a tack that you wrap a wire around spark plug wire. Mine was around $30 give or take. I wanted a tack I could replace the battery. Some cheaper ones, the battery is soldered and glued in place and no way to replace it.

I needed to set the idle speed of my fuel injected Kawasaki mule to be 1000 plus or minus 50. Too slow oil light comes on. Too fast, you will grind gears and spin tires when you put it in gear.

I was impressed with mine.

geo.
 
Ever hear of a "Treysit" tach?

It works off vibration, no battery, nothing to connect, just hold it against the running engine.

They've been around a long time, never actually used one, but they were popular in the past.

Good thing about them, they can sit in the tool box indefinitely and still work.
Treysit Tach
 
I can sell you a digital one that fits in the dash holes for $35. You can read your rpms for the seat anytime you want.
 
(quoted from post at 11:25:53 05/13/17) I have a mechanical one that we used to use to check the rpm of the cylinder on a combine. You simply held the tach against the end of the shaft and the shaft spun the tach.

If you could find something like that, there's no reason you couldn't hold it against the end of the crankshaft.

That is what I used to check the RPM of my Farmall M. Held it against the PTO shaft. Initial test showed the PTO was spinning at about 500 rpm. I played with the governor and achieved the correct rpms.
 
My father had a nice Stewart-Warner tach that you held on the end of the shaft, most exposed shafts have centers. I don't know what happened to it, when he passed it was gone. I have this old revolution counter, same thing, but requires a watch with a second hand, and I don't wear a watch anymore.
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(quoted from post at 05:50:07 05/14/17) My father had a nice Stewart-Warner tach that you held on the end of the shaft, most exposed shafts have centers. I don't know what happened to it, when he passed it was gone. I have this old revolution counter, same thing, but requires a watch with a second hand, and I don't wear a watch anymore.
a160137.jpg

I have one very similar. It is hanging on the wall. Haven't even tried to use it.
 
I second what Steve/Advance already posted. A hand-held vibration
tach. No batteries and no mechanical contact with the engine. I still
use the one I bought in 1975 for $5. Works great. I also have a few
of the contact-necessary AC and Stewart Warner mechanical tachs.
Problem is - sometimes there is no safe place to get a reading from a
rotating shaft. That is the beauty of a vibration tach. Put it on the
shelf for 10 years and then go to use it - and NEVER a dead battery.
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I've had one of those little Briggs tach's for years.
I have a Extech digital contact tach I've use to check pto speed, it has interchangeable tips and a wheel I use for checking belt and roller speeds in ft per minute at the mill I worked at.
I have a Tiny Tach in my diesel pickup but consider them to be more of a permanent install than a test unit.
I like the looks of the laser photo tach's listed, they would be handy when access to the end of the crank or equipment shaft is difficult or dangerous.
 
This Model "Jaquet Hand Tachometer no. 628-630" was the Cadillac of Tachs. It served me well in my 40 years around Rotating equipment:

This Puppy has a SIX speed selector:

10000>50000 RPM:

3000>15000

1000>5000

300>1500

100>500

30>150

I purchased a Sawmill, this Tach. was used to set 48" Blade RPM. Hand held and you require a watch.
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There is a hand held direct read tach at the farm that I bought over 60 years ago to check the RPM's of electric motors back when I was working on those. It is very accurate. I left it at the farm, brother still uses it on occasion.
 
I have a PET. it picks up on the ignition pulse from the sparkplug wire. Accurate to over 14000 rpm. It only works on engines that spark every revolution. Not cheap, over $100 8 years ago.

(Well, if yours only sparks every other revolution, multiply the reading by 2)
 
Thanks to all you guys for the education on Tachometers. I like the idea of the light sensor because I could use it on my lathe. But, I cannot find a suitable place to get a reflector mounted on the JD 40 though. The electronic ones are interesting, but I am not comfortable using that stuff. Too many buttons. I would have to get my 4 year old grandson to help me figure it out. I'm gonna digest all this info for a couple of days before making a purchase. Again, thanks for all your help.
 
They are a good compact tach. My only suggestion is to remove the batteries if you store them any length of time. SON liked mine, so I bought another one. An inferred temp gun is another great tool to have.
 
It was probably on ebay but I bought a new one for the ridiculous price of about $10 new. It was electronic and came with a page of white reflective strips, like the red and white reflective strips you see along the sides of trailers. I too had to set the rpm for a Trail Wagon so it too wouldn't die nor rip out the tranny when you shifted. Just put a strip on the flywheel turn her on and read the dial.
Must have been accurate as the TW worked when finished.
 

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