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#1
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BTIZ wrote:
Why do you have to thread it through everything? Tach cables come in two parts: cable and housing. If you disconnect both engine and tach ends, you can pull the cable out and thread a new one back in, using the old housing. Be sure to use plenty of moly grease, to keep the cable well-lubed. BTW, any speedometer shop can make up a new cable, with the proper ends. Question... is a tach cable made up at the local speedo shop an approved aircraft part? Does it need to be? Or does a DAR have to approve it as a suitable replacement part? Or can an IA do that? BT Well... maybe it requires a DAR... or maybe it could qualify as an "owner produced part"... or maybe it could fall under the category of "I don't know... it was like that when I bought it." Anyway, I went out and looked at my cable and housing yesterday. After fiddling around with it for some time, I concluded that that cable and housing sure looked good to me. I ordered a new tach from Spruce which should be here Thursday. When the cold weather hits, if it WAS the tach, I will know it. If it WASN'T the tach, I'll know that for sure as well. I would have preferred to do an accurate diagnosis first, but for the price, I've done SOMETHING to advance the resolution process. Rich |
#2
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Had a similar problem on my Arrow a couple of years ago one bitter
cold morning - went up to 3000 RPM, then back to 2700 but no audible change in the engine. I just decided (#*$& with this technology and installed a digital tach. In addition to getting perfectly accurate readings, the digital unit (Horizon) also monitors both mags continuously. |
#3
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In article ,
Rich wrote: I sure would welcome counsel from people on this list who may have encountered this problem. Was turning base to final one day when suddenly there was a horrible screeching. A quick check of my wife and her friend confirmed that neither of them were screaming at the moment. A peek at the tach and I notice the needle going crazy!! Moving back and forth so fast it's a blur..until TINK and the needle falls off and the screeching stopped. I replaced it with a digital tach. FYI if you buy a tach you can have the hours set to whatever you want...makes the record keeping easy. -- Dale L. Falk There is nothing - absolutely nothing - half so much worth doing as simply messing around with airplanes. http://home.gci.net/~sncdfalk/flying.html |
#4
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Pull the center cable out and clean the old sticky oil off with a solvent. Re coat with new motor oil and reinstall. If you do this soon enough it will not break and you will not have to buy a new cable. On Mon, 11 Oct 2004 09:14:44 -0400, Rich wrote: I've got a problem that seems to be cold-weather related, and I'm trying to determine whether it is more likely the tachometer or the tach cable. Happened a couple of times last spring, and once last week when we had a cold snap in Michigan. On the ground, I hear what sounds like an intermittant 'chirp... chirp' sound. Sounds like a shaft vibrating in a loose bearing, kind of like you sometimes hear when you fast-rewind a cheap VCR tape. In the air, I get a drift toward an overspeed reading (2900 - 3000 RPM instead of maybe 2700). Based on sound, power settings and airspeed, I am convinced that the engine did NOT overspeed. After a few minutes (5?) the tach settled down to "normal" readings and stayed there the rest of the two leg flight. Some people suggest it is the tach cable, tightening up and untwisting due to either a kink or stiff lubrication. The tach, they say, is reading the instantaneous velocity of the highest rotational speed. Others say it is the tachometer (bearing noise) because they say "they had that once and when they replaced the tach, the problem went away". Tach cable is relatively cheap to replace, but difficult to thread through the firewall and behind the panel. New tach is easy to replace but more costly, and will add confusion to future record keeping in the logbooks. I sure would welcome counsel from people on this list who may have encountered this problem. Rich |
#5
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