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Using a laser tachometer


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#1 tysonkad OFFLINE  

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Posted May 28, 2017 - 12:32 PM

Quick question, where would be the best place to put the reflective film for a laser tachometer? I would think that putting it on the outside of the flywheel would give a lower rpm reading than if mounted on the driveshaft?

I want to set the governor to make sure I'm at 3600 rpm.

Thanks!

#2 bbuckler OFFLINE  

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Posted May 28, 2017 - 12:34 PM

I use flywheel or pto pulley


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#3 petrj6 OFFLINE  

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Posted May 28, 2017 - 01:05 PM

doesn't matter where, rpms don't change with diameter just surface travel speed.


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#4 LilysDad OFFLINE  

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Posted May 28, 2017 - 01:29 PM

doesn't matter where, rpms don't change with diameter just surface travel speed.

Hmmm . . .         Is the surface travel speed the same at the crank as it is at the outer flywheel? The tach measures RPMs, rotations per minute-how many times that piece of tape comes past the light in a minute. That doesn't vary with diameter.


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#5 tysonkad OFFLINE  

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Posted May 28, 2017 - 01:42 PM

Ahhh right, that makes sense! The speed at the outside of the flywheel would be greater so the RPM would measure the same.

Thanks for the fast replies!

#6 petrj6 OFFLINE  

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Posted May 28, 2017 - 04:20 PM

   The rpm stays the same no matter what the diameter of the wheel, the difference would be the distance traveled per revolution or IE the surface speed.  that's how you can change the speed of a tractor by changing pulley sizes, don't change the rpms but it will change the speed.  I used one of those digital tachs awhile ago and was happy but I think if I had to do it again I would just get a tiny tack and just wire it in.


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#7 LilysDad OFFLINE  

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Posted May 28, 2017 - 05:29 PM

As I said in another thread, I have no good place to put the tape on my Ingersoll. The flywheel is covered.


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#8 James Bosma ONLINE  

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Posted May 28, 2017 - 06:54 PM

As I said in another thread, I have no good place to put the tape on my Ingersoll. The flywheel is covered.

Doesn't have to be on the flywheel  I put mine on the universal on the drive shaft by the engine

Drive shaft spins same RPM speed as the engine does


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#9 lyall OFFLINE  

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Posted May 28, 2017 - 07:26 PM

I have used bright white paint and it works okay about an inch square


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#10 petrj6 OFFLINE  

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Posted May 28, 2017 - 07:51 PM

    Lost the tape for mine (my daughter liked it) so I would up using trailer reflective tape and it really only needs to be a 1/4" strip.  when I used mine the only good spot was the end of the crank on the front of the engine, only a 1.5" dia shaft so not much room for a 1/2" strip



#11 LilysDad OFFLINE  

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Posted May 28, 2017 - 08:26 PM

Doesn't have to be on the flywheel  I put mine on the universal on the drive shaft by the engine

Drive shaft spins same RPM speed as the engine does

Ingersoll doesn't have a driveshaft. I put it on the PTO, but the mower has to be on and that slows the engine down an unknown amount. I'll just have to pull the mower off one day. . .  or find a cheap deal on a Tiny Tach.


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#12 ol' stonebreaker OFFLINE  

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Posted May 28, 2017 - 08:36 PM

  I've put the tape on the screen on top of the flywheel on some and it worked fine. Checked and adjusted RPM on a friend's the other day and the only place I could see was a small opening that exposed the rim of the flywheel where the blade brake contacts it. I had the blade brake handle held down with visegrips so it worked OK for me. I had to attach the tape with a pair of needlenose and a screwdriver. 

                                        Mike



#13 cheluIS OFFLINE  

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Posted May 29, 2017 - 06:47 AM

Self adhesive silver tape :

 

https://www.youtube....h?v=X1c92L47qEg


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#14 tysonkad OFFLINE  

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Posted May 30, 2017 - 02:36 PM

Just got the tach in from Amazon today, came with reflective tape. Thanks for all the advice, I'm going to put it to use tomorrow. Cheers!






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