Piano Key switch grommets

How to keep the Cessna 170 flying and airworthy.

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james_layman
Posts: 56
Joined: Sat Jan 29, 2005 4:15 pm

Piano Key switch grommets

Post by james_layman »

Am in annual for my 1949 170A and found most if not all of the rubber grommets for the piano key switches had fallen apart and were in need of replacement. So I ordered some thinking this can't be all that bad.

Thought I could disconnect the wires from a switch, back it out and simply replace the grommet. Nope.

When that did not work I thought, well I will just remove the switch bar bracket but that did not work as the switch mounting bracket seems to be part of the switch bar bracket and all of the screws all come out easily except for the 2 hidden behind the plexiglass panel!

What have we missed?

By the way it is possible to replace a grommet using dental tools and at least 2 hours of daylight!!!!
doug8082a
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Post by doug8082a »

This might not be what you want to hear, but it's a LOT easier to do if you remove the entire switch assembly. To do so you'll need to remove the plexi panel, which you can't remove until you remove the control cables and lower left and right panel covers, which you can't remove until you remove the control columns... So, the process would be something like this:

If you still have the lower left and right overlay panels (if not, go to step 3):
1. Remove the control columns
2. Remove the overlay panels (you'll have to remove the cigarette lighter/accessory plug (if installed) and primer).

3. Remove control cables
4. Remove the plexi panel
5. Remove the switch assembly
6. Disconnect the switches and fuses/CBs (if installed in their original locations)
7. After spending all that time ($$$) you can replace your $0.66 worth of grommets 8) :twisted:

Do you have the Illustrated Parts Catalog for your 170? It has a decent drawing of the assembly.

This *can* be done from underneath but as you've probably noticed it could be a royal pain in the butt.
Doug
james_layman
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Piano keys

Post by james_layman »

Correct. I did not want to hear that I had to take half the airplane apart just to replace some little rubber things that have fallen on hard times.

Guess if a switch ever fails I am looking at the same thing?


Jim
doug8082a
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Post by doug8082a »

I'm afraid so. The way the various brackets are formed there's no real way to get at the nuts that hold the switches on. The nut that holds the switch on the bracket is concealed by a J-shaped piece (p/n 0411889 - Clip - Switch Limit).

As a side note some people look to replace these switches in favor of a 3-way switch without realizing that is what they have already. These switches are all designed as UP - On, DOWN - On, NEUTRAL - Off. The only reason you can't operate them that way is because Cessna installed the aforementioned switch limiting clip (0411889) which only allows for DOWN - On (actually it's UP - On, the piano key "cams" the toggle switch in the opposite direction. Down on the piano key = up on the toggle switch). If you look at the back of the switches you'll see that they all have the provision for an extra connection.

Anyone who had the Stewart-Warner heater installed would have one of these switches without the Switch Limit Clip installed. That's because for the heater UP was for FAN (which also searved to prime the heater) and DOWN was for ON.
Doug
bagarre
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Re: Piano Key switch grommets

Post by bagarre »

I'm about to take on the task of installing breakers and all new switches behind my piano keys.

Has anyone come up with a trick or made a tool for removing the switches without having to de-install the whole panel?

Is it at all possible to remove the switch brackets from the back?

In my case, I want to remove the Switch Brackets ( 0412475 ) that hold the fuses to make room for the new breaker bracket.
Is this possible? From the IPC, I can't tell if the Switch Bar ( 0413240 ) needs the other bracket for support.
I didn't want to cut the fuse mounts off if I didn't have to.

Thanks much,
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LBPilot82
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Re: Piano Key switch grommets

Post by LBPilot82 »

It's been a while, so I don't remember specifically how, but I do know that the switches can be replaced without much other dissasembly. I replaced my landing light switch and did not have to dissasemble the front plexi cover. As far as mounting CB's, DO NOT cut the current bracket unless you want to relocate it completely. I mounted a single plate on top of the existing fuse bracket with holes drilled to match the old fuse hole and mounted the new CB's to that. The plate covers all 6 original holes and allows you to mount additional CB's in the middle. The CB's sandwiched the new plate on top of the old to hold it in place.
Richard Dach
49' A Model N9007A
SN 18762
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Bruce Fenstermacher
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Re: Piano Key switch grommets

Post by Bruce Fenstermacher »

I did the same thing as LBPilot (or did he copy me :? ).

Anyway it is very easy to do, requires no modification other than removal of the fuses and looks good. You could probably mount an extra CB or two in the middle if necessary but I didn't do that. Can't remember if I didn't want to crowd the T&B CB that is mounted high in the center or whether I was going to mount CBs at another location and didn't need them in the middle. I have an overlay plate and some CBs I can take a picture of later for you.

BTW double the time you think it will take you to do this job.
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bagarre
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Re: Piano Key switch grommets

Post by bagarre »

I thought about using the bracket in that way but, I'm adding a few more breakers than will fit that way.
That and I wanted to move them forward more. I've made a new bracket out of angle aluminum that I plan to mount under the panel.

Do the switch brackets need the fuse brackets to be properly supported?
I can't tell from the breakout in the manual or even from looking underneath.

Cheers,
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KS170A
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Re: Piano Key switch grommets

Post by KS170A »

bagarre wrote:I thought about using the bracket in that way but, I'm adding a few more breakers than will fit that way.
That and I wanted to move them forward more. I've made a new bracket out of angle aluminum that I plan to mount under the panel.

Do the switch brackets need the fuse brackets to be properly supported?
I can't tell from the breakout in the manual or even from looking underneath.

Cheers,
I had my assembly out while re-working my panel last year. I found a photo that may give you some insight. The brackets that hold the fuses also hold the entire assembly in place when screwed to the panel. I now have a total of 12 c/b's that I squeezed in the space that the six fuse holders were.
Attachments
switch assy lower.jpg
43A Panel.jpg
--Josh
1950 170A
bagarre
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Re: Piano Key switch grommets

Post by bagarre »

That's how many I'm trying to fit under there.
I'll have to go look at it again because that would be SO much easier.
What's your center to center spacing on the breakers and which of the 12 are using the original 6 holes?

I still need to get the switches out to replace a few grommets tho.

On a side note, how do you like the turn coordinator way over on the right like that?
I still use the ball a lot and like it in front of me.
The next project is to re-organize the instrument panel to accommodate a horizon but there are only so many holes.
(I want a horizon but I really have no need for one as a VFR pilot...but thats another thread)

Thanks for the photos!
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KS170A
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Re: Piano Key switch grommets

Post by KS170A »

I have only flown maybe 1.5 hours with this new panel, so far I like it. IMHO, the T/C is not terribly important to VFR flying, and in the initial test flights I've noted where the ball "appears" from the pilot's seat when it is actually centered when viewed from straight-on. The blank hole in front of the pilot seat will be an attitude indicator at some point, if the bank account ever allows! :lol: My goal was to have the top part of the "six-pack" directly in front of me, then the supporting instruments next to them.

I don't exactly recall what the spacing was, I'll see if I can get that information. I believe there are only two c/b's that use original fuse holes -- the outer two. The others I had to elongate to make fit. The photo is my 3rd attempt at a breaker panel. Originally I had much wider spacing, but found it interfered with the rheostat, so went to the smaller spacing. I'm thinking maybe 1 inch, maybe slightly less? Like I say, I'll double-check.
--Josh
1950 170A
bagarre
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Re: Piano Key switch grommets

Post by bagarre »

After spending a few hours upside down with a flashlight, mirror and a bent up wrench, I decided to approach the problem from the front of the panel.
I ALMOST removed every cable to pull off the Plexiglas panel...but I went another route.
Since I plan to replace that panel next year and the previous owner already drilled some ugly holes in it, I decided that two more 3/8ths holes wouldnt hurt.
I carefully drilled the holes right over the screw heads so I could get a screw driver on them.
Bingo!

I'll pop in two little plugs to cover the holes and it wont look any worse for wear.
bagarre
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Re: Piano Key switch grommets

Post by bagarre »

OK. Quick shot of the short cut.
This is a GREAT idea,...so long as you don't mind two tiny little holes in your plexi panel.

Don't mind the silver plug over the throttle or the extra "Don't Panic" cover...they are hiding holes made from the previous owner to mount a Garmin GPS :?

Cheers.
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dstates
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Re: Piano Key switch grommets

Post by dstates »

This is a great thread talking about adding switches/grommets/CB's. It appears some of the pictures are no longer tied to the reply's. Anyone have those somewhere?

I'm also considering drilling two holes in the plexiglass to access the two hidden screws like bagarre did (my panel is not that pretty to begin with). Any suggestions on how I would I find those exact locations?

I'm in the midst of re-wiring the plane and will be adding a new circuit breaker panel in front of where the original fuses were located (see cardboard mockup). To do this I will likely cut the bottom of the old fuse mounting bracket off to make room. Any concerns with this (besides originality)?

Thanks!
Doug
CB_mockup.jpg
fuse_hole_removal.jpg
N1235D - 1951 170A - SN: 20118
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Bruce Fenstermacher
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Re: Piano Key switch grommets

Post by Bruce Fenstermacher »

Doug, I installed CBs but spaced them so they would go through the original holes. I cut two identical pieces of aluminum with the correct size holes spaced so the breaker would pass through the old fuse hole which is to large for the breaker. Put one plate on the back side of the original fuse tab and one on the front and put the breakers through all three with the breaker acting like a bolt holding them all together. Worked great. Below are some other panels I made for my current 170. They are not the same as the holes are for fuse holders and the spacing is not correct to put CBs through the old holes but you get the idea what kind of plates I'm talking about I hope.
Layout 1_Page 1.jpg
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