TC45D tach calibration

[JC-jetro]

Any of the non-contact tach that Jim suggested works just fine for your application. Although Strobe tach is much superior mainly due to safety I can not recommend it for you application. The one I bought where I use it commercially is in the $1500 neighborhood where I bought many years ago. They are still pricey. A $20-$30 works just fine for your application. The only caveat is the rotating shaft and pulley should be turned off or engine killed. You then put small piece of reflective tape, turn the engine on and have to get close enough about 6" or maybe little less and try to shine the light on the reflective tape for the device to register the rpm. So with the engine off you need to decide where it is best to put the tape and where to hold the device in advance and how to keep it steady. You can see that it can be dangerous let say if your next to a prop, rotating shaft. All the HVAC test and balance contractors I know elect to buy non-contact tachs like Jim suggested. Strobes are used in more dangerous or difficult industrial application.

JC,

 

[Professor Marvel]

Thanks JC and Jim

 

[dhyayi]

Amazon has all types and price ranges of non-contact tachometers. I don't have a particular strobe type to suggest.

btw, thanks for this link....

 

[Professor Marvel]

Hey guys I am back with the continuation of this problem.
It is mowing time again and I find my tach problem is haunting me again because I am concerned about PTO speed. I used a timing strobe and my tach is over 500 high. At 500+ over when i am at PTO speed my tach is basically red lining to maxed out.
I took all wires out of my alternator and the problem still exists. I actually cut the pink wire behind the cluster and problem still exists.
I went to Messicks and see that the instrument panel is 500 dollars and I do not see the tach separate. Any other possibilities? If a wire was grounded I would think my battery would drain or not charge correctly.
Thanks

 

[JC-jetro]

How did you use a timing strobe light to measure RPM? did you buy a non-contact, non strobe light tach with a reflective tape? how did you perform the test?

JC,

 

[Professor Marvel]

It is the kind with the reflective tape. I used the pulley at the front that turns with the crankshaft for the engine RPMs and I used the PTO shaft and compared it to the PTO rpm notation on my tach. They seemed pretty consistent. IE The percentage that the engine rpm was off was similar to the percentage that the PTO RPM was off. Sorry for my lack of correct description. If I am not clear I could try to describe it again.
Thanks for your help.

 

[JC-jetro]

It is the kind with the reflective tape. I used the pulley at the front that turns with the crankshaft for the engine RPMs and I used the PTO shaft and compared it to the PTO rpm notation on my tach. They seemed pretty consistent. IE The percentage that the engine rpm was off was similar to the percentage that the PTO RPM was off. Sorry for my lack of correct description. If I am not clear I could try to describe it again.
Thanks for your help.

PM,

What are the numbers you got, such as Engine rpm vs PTO rpm. For example at about 2500 rpm for the engine I should expect to get 450 rpm at the pto. Do you get numbers like that? What PTO rpm do you get or expect to get. The relationship between engine rpm and PTO might not be linear or in straight line. What that means is if the relationship was linear the following could be expected. Let's say @ 1000 engine rpm you got 300 pto rpm and at 2000 engine rpm you got 500 pto rpm then you should expect for sure to get 400 rpm right at engine 1500 rpm. You need to look at your Owner's Manual and if it says for example 540 pto rpm at 2600 engine rpm then that's where you need to run your tractor at.

You can monitor your pto with your optical tach, keep increasing or decreasing your engine till you reach 540 and that's where you need to run the engine at. If that does not appear to be severely overramping the engine, then I stick to it for pto driven operation.

JC,

 

[jinman]

It sounds to me like your needle may have slipped on the pin coming out of the tach. You may be able to pull the needle, rotate it to zero, and put it back on the pin. If my tach had a 500 rpm offset when I turned on the key, this is exactly what I would try. You've established that there is a set offset of your tach all the way up, so this is not a linearity problem. A slipped needle is a definite possibility. I used to build aircraft instruments and used a tiny jeweler's socket for a pin/needle pusher. If your needle has been tacked in place with adhesive, you may have to heat it a tiny bit with a soldering iron tip or something, but you should be able to pull the needle if you are very careful. You can damage the needle just as easily, so be careful.

EDIT: The tachometer IS available by itself. The part number is 86540854 and is around $182. That's a bunch, but much better than the whole $788 they want for the entire instrument panel.

 

[JC-jetro]

Good point on the needle Jim. I'd probably put a small drop of crazy glue so it'll stick. I'd had to the same on a clock that the needle would get lose from time to time. We still don't know what actual rpm the OP got on his PTO.

JC,

 

[jinman]

Good point on the needle Jim. I'd probably put a small drop of crazy glue so it'll stick. I'd had to the same on a clock that the needle would get lose from time to time. We still don't know what actual rpm the OP got on his PTO.

JC,

JC, I just looked at the needle in one of my photos and it seems to have a wide area around the pin that could help pull it off. The proper way to get it right would be to remove the needle and then power up the tach with the ignition key. While the tach is powered, place the needle on the pin with it pointing toward zero. Let it stay powered until the glue dries if glue is needed. If it feels firm without glue, turn the power off and the needle will move down to the lower stop peg. Power the tach on/off a few times to make sure the needle is going to stay put and then try it with the engine running to see if it has not improved. It won't be 100% accurate, but it won't have a 500 rpm offset either.