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a tach thing, ever heard this before ???

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Old 09-10-2007, 04:43 PM
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the Wasp
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Default a tach thing, ever heard this before ???


hey, though my tach was bad,,

my H9 DVT tach was always spot-on with all other brands of tachs I tested it against,, well the other day my tach didn't read right, numbers were all over the place (will I knew I had to send it back, eerrrr),, well then I thought "the sun was coming down and the tach was pointing right into the sun", so I turned the tach so it was pointing away from the sun and it worked great,,

anyone ever heard of this before ???

Jim
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Old 09-10-2007, 05:05 PM
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Default RE: a tach thing, ever heard this before ???

so far all i buy is ragie tach s
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Old 10-26-2007, 02:17 PM
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Default RE: a tach thing, ever heard this before ???

Mine┬┤s like this too.
I think this is nothing to worry about. I believe the sunray┬┤s can mess with the sensor readings.
Mine is spot on when checked against a lamp plugged in the wall outlet.

Lars.
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Old 10-26-2007, 07:21 PM
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Default RE: a tach thing, ever heard this before ???

I don't know the differences in all the tachs out there, but almost any tach that used reflector tape will do that when pointed into the sun.
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Old 11-01-2007, 11:16 PM
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Default RE: a tach thing, ever heard this before ???

broke_n_bummin,, I can see the light now LOL



well I have never seen this happen at the field, so what I'm now think happened is,,

I had the motor mounted to a picnic table under a 2nd floor porch-deck, under the deck it was a bit dark, the sun was located directly in front of the prop, so it was dark behind the prop, so with the tach behind the prop the tach had no reflection on the prop to read,, as I said I have never had this happen at the field where there is sun on both sides of the prop..

Jim
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Old 11-02-2007, 07:24 AM
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Default RE: a tach thing, ever heard this before ???

I met up with a guy a few months ago that wouldn't own an optical tach. He's rather hold his tach to the point of his spinner. He was convinced that the optical tachs couldn't be reliable. I observed his technique, and... well ... I think he needs to contact Sylvia Browne to see what he was in his last life, and just how long it lasted. It wasn't too bad up to about 7K ... then it started wabling and vibrating. When it did that, he'd just apply more pressure. After I saw 9K, I couldn't watch anymore. All that kept running through my mind was that joke about a Rednecks famous LAST words. " Hey Y'all ... Watch this"
Optical tachs are pretty sensitive and fairly accurate. I have found that if I put my tape on the spinner and hit it at an angle I don't get as much variation caused by different light sources. Most of the time I use the one we have at work. I'll have to get back to you on the brand, but it's an industrial model with 2 lasers that constantly check against themselves. They have it calibrated twice a year, and so far this year all it has measured is rpms on my engines. I have tried to make it mess up with the light and couldn't. I'll try your method tonight and see what happens. We have some UV lights I can use to duplicate sunlight. The people we bought the tach from sent us a card wanting to know if it ever messes up, what the conditions were and what it did. So far, the other equipment we've bought from them has been nothing but the highest quality (infared heat guns, pyrometers, spectrometers).
I have a Raytech tach that I use here at the house, and in order to get it to read right, it has to be a certain day of the month, the planets have to be alligned just right, and you have to recite an incantation while burning insence.
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