Measuring RPM with laser

paddymk2
Member

Posts: 210

Measuring RPM with laser Dec 16, 2017 6:40:44 GMT

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Post by paddymk2 on Dec 16, 2017 6:40:44 GMT

Hi,
Among other things, I wanted to measure RPM. I've borrowed one of those little handheld RPM meters and put some reflective tape onto the fan blade. But I'm not sure; is the fan turning at the same rate as the engine - of if there is some ratio between the two.
Cheers

dave1800
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Posts: 3,589
Attribute: Technical Guru.

Measuring RPM with laser Dec 16, 2017 10:03:54 GMT

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Post by dave1800 on Dec 16, 2017 10:03:54 GMT

The fan speed will not be the same as the engine unless your fan pulley is exactly the same size as the crankshaft pulley. You will need to measure the diameter of both to calculate the ratio, alternatively turn the crank one whole turn using the timing mark for reference and see how far the fan turns. I believe there were different size fan (smaller) pulleys in Australia to improve the cooling.

Plenty of digital tachos on EBAY for very little money.

regards

David

paddymk2 Member Posts: 210	Measuring RPM with laser Dec 17, 2017 2:42:38 GMT Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by paddymk2 on Dec 17, 2017 2:42:38 GMT Thanks - makes sense.

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Post by paddymk2 on Dec 16, 2017 6:40:44 GMT

Post by dave1800 on Dec 16, 2017 10:03:54 GMT

Post by paddymk2 on Dec 17, 2017 2:42:38 GMT