Tach cable left or right hand on C145?

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pistolagrande
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Joined: Thu Feb 23, 2017 12:02 am

Tach cable left or right hand on C145?

Post by pistolagrande »

After extensive work on my accessory case, which did include a new tach seal on the adapter on the rear of the accessory case. I now have a very slow leak of oil coming from the back of the Tachometer.
I figured I am looking at replacing the Tach Seal, again, but this time I also wanted to replace the tach cable because I understand that there might be an oil seal incorporated into the end of that cable as well.
So the first question is in a 51 170A with a c145 engine, do I need a left hand or right hand tach cable?
Is there something else I also should be looking to resolve this issue?

Thanks,
Scott
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n2582d
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Joined: Mon Apr 29, 2002 4:58 am

Re: Tach cable left or right hand on C145?

Post by n2582d »

Click to enlarge
Click to enlarge
From Aircraft Spruce:
To determine cable rotation, note the rotation direction of the tach drive socket on the engine while looking at the engine. If the drive socket rotates clockwise, a right lay inner cable is required. If the drive socket rotates counter-clockwise, a left lay inner cable is required. The rotation direction of the tach needle does not affect which lay should be used.
Gary
pistolagrande
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Joined: Thu Feb 23, 2017 12:02 am

Re: Tach cable left or right hand on C145?

Post by pistolagrande »

I guess I was hoping there would be a standard for all c145 engines....
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n2582d
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Re: Tach cable left or right hand on C145?

Post by n2582d »

Scott,
The tach drive comes off the driven gear of the oil pump. This rotates in a clockwise direction when viewed from the rear. Here's a nice write-up on changing the seal. I'm surprised oil made it all the way up your cable. Does your tach cable housing have the drain hole described in the link above? I'm not familiar with another oil seal on the tach cable itself. I think the seal in the housing should stop all oil from migrating up the cable. Maybe someone got too zealous lubing the tach drive cable and that is what you have dripping in the cockpit?
Gary
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GAHorn
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Re: Tach cable left or right hand on C145?

Post by GAHorn »

The tach-drive seal CAN and DOES control engine oil from travelling up the tach drive cable and if you have a bad seal (PN 642714) you can end up with oil inside your tachometer... AND INSIDE YOUR COCKPIT and dripping down the backside of your instrument panel and onto your floorboards and carpet. I've seen it personally when the generator gasket was changed but the tach drive seal was not. (The tach drive housing must be removed to allow the gen gasket to be replaced properly. Cutting the gen gasket is a bad idea, as I've discovered and written about extensively subsequent to the Las Vegas convention trip.

Here's one post I wrote about it: http://cessna170.org/forums/viewtopic.p ... egas#p7652

Short version: Don't cut the gen mount gasket. Change the tach drive seal at the same time.

The tach and the drive cable for our TCM-powered airplanes is clockwise rotation.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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