Tach cable routing

[gnflyn]

Am replacing my tach cable with a new 42" inner cable and outer housing. My BC-12 with an A65-8 has very little clearance between firewall and tach cable output fitting. I can just get it connected by bending outer housing. Is that normal (the original was that way)? Or do some setups use a right angle drive? Thanks,,,

[TimHicks]

Re: Tach cable routing

90 degree on my '46

[M Towsley]

Re: Tach cable routing

Just bent on my mine. I believe that is original but some folks use the 90 degree fitting.

Tim, he is talking about the tach output at the engine.

[LostnSpace]

Re: Tach cable routing

This reminds me, if anyone is looking for a very good tach for an A-65, I have an original that was rebuilt by Quality Instruments about 5 years and 80 hours ago, I am putting a C-90 in the plane and don't need this. e-mail: acmech46 at yahoo dot com, gary

[Hank Jarrett]

Re: Tach cable routing

I used two 90* fittings since I had very little clearance on either end. At least one needs to be one of the ones you can change rotation direction on to be sure you don't spin eh tach backwards. You also want to be sure the cable is spinning so it winds TIGHTER not looser. The cable will last a lot longer.

Hank

[gnflyn]

Re: Tach cable routing

Okay, I am really confused here. Installed new inner/outer tach cable, fired her up and the tach reads zero. Removed cable from engine and using an adapter I made spun cable with my cordless drill, tach worked fine. Reconnect cable to engine and disconnect from the tach itself, ran cable out through left glove box door (I removed box and door for access). Fired up engine and see the tach inner cable spinning just fine where it protrudes from housing. Remove tach and angle drive from panel, connect tach to cable and fired up engine. Tach works fine, so I start moving it around flexing cable to about where it should be with tach installed and tach quits till I straighten cable back out.
I brought everything home and set it up on bench, spin it with drill, all works fine......
I am perplexed.....................

[gnflyn]

Re: Tach cable routing

Okay, I am really confused here. Installed new inner/outer tach cable, fired her up and the tach reads zero. Removed cable from engine and using an adapter I made spun cable with my cordless drill, tach worked fine. Reconnect cable to engine and disconnect from the tach itself, ran cable out through left glove box door (I removed box and door for access). Fired up engine and see the tach inner cable spinning just fine where it protrudes from housing. Remove tach and angle drive from panel, connect tach to cable and fired up engine. Tach works fine, so I start moving it around flexing cable to about where it should be with tach installed and tach quits till I straighten cable back out.
I brought everything home and set it up on bench, spin it with drill, all works fine......
I am perplexed.....................

[M Towsley]

Re: Tach cable routing

Cable may not be engaging either end, too short?

[gnflyn]

Re: Tach cable routing

I laid out old and new side by side, if anything new inner cable is 1/32 longer. Wondering if its an engine internal issue.

[Robert Lees]

Re: Tach cable routing

I laid out old and new side by side, if anything new inner cable is 1/32 longer. Wondering if its an engine internal issue.

Less likely...and you'd rather hope not!

Are you sure, to which Hank alluded, that the rotation is in the correct sense for the instrument?

[3Dreaming]

Re: Tach cable routing

Less likely...and you'd rather hope not!

Are you sure, to which Hank alluded, that the rotation is in the correct sense for the instrument?

He started out in the other post with a tach needle that had started jumping around, so I doubt that the engine or tach changed direction of rotation.

With the tach cable removed from the engine take a small screwdriver and insert it into the tach drive and make sure it rotates with the engine. Also make sure it doesn't rotate when the engine is not turning.

[woodmw]

Re: Tach cable routing

According to the Aircraft Spruce website, the inner cable effective length is decreased 11/16" per 360* of bend. My bet is, when you bend to approximate being mounted in panel, the inner drive cable is pulling out at one end. Have you compared length of old and new outer housings? Maybe old is slightly shorter. Is the new routing the same, or are there any new bends, however small? Wild guess, but could it be that the old drive cable was not engaged 100% and thus causing the fluctuations?

[astjp2]

Re: Tach cable routing

Check your engagement in the engine, there is only a little tang to engage the cable with. Tim

[gnflyn]

Re: Tach cable routing

All is well. I got a used tach and cable from lostinspace on the forum. It seems the tach I got from him has the right angle drive built into the tach. So I was able to use a cable provided by him that has a male thread in coupling on the tach drive end. I flushed it out several times to get dried lub out and relubed everything. Cool, it works fine..... Thanks, Gary

[LostnSpace]

Re: Tach cable routing

Glad it work out for you, next i want to sell the US Gage oil pressure, but I can't get the picture small enough to attach, fly safe, gary