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[bigrenna]

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[GAHorn]

If you go to page 8/9 of 2011 4th Quarter, The 170 News, http://cessna170.org/forums/membersOnly ... ws4Q11.pdf ... you will see the article I wrote about this item, and how I replaced the GE 1819 lamp with LED lamps. One of the pics posted includes the square "can" in which the 1819 lamp-holder is mounted, and attached to the roof with MS screws.

[bigrenna]

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[cessna170bdriver]

As I remember, an original speaker has a bracket built around the magnet. The bracket (about 1/8 - 3/16 thick) is tapped for two screws that come through the cabin roof. The speaker baffle is hung from the speaker.

When I replaced my speaker many moons ago (A LONG time before I knew the speaker could be re-coned), I used one from an old cheap stereo I had when I was a teenager. Of course the speaker didn't have the bracket built in, so I used construction adhesive to attach a 3/4" thick block of hardwood to the magnet and attached it with 1/2" long flush wood screws with trim washers on top of the cabin roof. That lasted about 20 years before the glue got brittle and gave up. I'm not sure what I'm going to do this time around...

[blueldr]

Miles,
Your problem is that your glue did not have a basis of approval for that job.

[cessna170bdriver]

Miles,
Your problem is that your glue did not have a basis of approval for that job.

It SHOULD be approved; it outlasted two engines!

[n2582d]

Greg,
I'm on the road now but I'll try and remember to take some pictures of the mounting location of the dome light when I get home. For what it's worth here is a picture of my '52 dome light (the ugly one) and one I picked up at a salvage yard from a later model Cessna. The IPC shows a bushing spacer to mount it on the later 170s but it doesn't give a p/n. Not sure if the '52 just mounted straight to the roof without a spacer or not. I would guess it too had them otherwise the dome light would ride too high and pull the headliner up.

The speaker Miles wrote about is attached with two mounting screws which have washers (p/n 0311001-27) under the screw heads. I believe these washers were originally made from cork. These same washers are used on the screws in the fuel filler adapter and on the screws of the windshield center strip. That washer is now p/n S350 and is made of Nitrile. A Stat-O-Seal made from Viton, p/n NAS1523C08E would also fit here. Anyway, these same washers (maybe with different I.D.) would be good to place on the dome light screws going through the top of the fuselage.

By the way, if anyone has an extra cover plate (p/n 0413139 - IPC #46) and lens (p/n 0413141 - IPC #49A) for this I'm in the market for them.

[bigrenna]

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[Bruce Fenstermacher]

Aircraft serial 20267 thru 25372 (this would be the '52 model) did not have the entire plate assembly with the dome light intergal to it as shown on the left and lower left of the part of the IPC page Gary posted. It only had the rectangular dome light.

And as Gary tried to say, there is no structure for it to mount to. It was apparently mounted to the skin of the airframe with screws and standoffs that you can see (but has no part #) over the dome light on the left of Gary's IPC page.

Part of Fig 18 pg 34 170B IPC

Part of Fig 18 170B IPC.png (27.86 KiB) Viewed 5559 times

If you refer to figure 18 page 34 of the IPC (right) you will see that you have all the structure that was ever there. The bracket #51 was added for serial 26996 (56 model) and on.

[bigrenna]

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[cessna170bdriver]

As I remember, an original speaker has a bracket built around the magnet. The bracket (about 1/8 - 3/16 thick) is tapped for two screws that come through the cabin roof. The speaker baffle is hung from the speaker.

When I replaced my speaker many moons ago (A LONG time before I knew the speaker could be re-coned), I used one from an old cheap stereo I had when I was a teenager. Of course the speaker didn't have the bracket built in, so I used construction adhesive to attach a 3/4" thick block of hardwood to the magnet and attached it with 1/2" long flush wood screws with trim washers on top of the cabin roof. That lasted about 20 years before the glue got brittle and gave up. I'm not sure what I'm going to do this time around...

DOH! Not sure where my head was. The subject is clearly "dome light". I guess its proxmity to the speaker sent me off on a tangent. I thought I might have a better picture of the installation, but this is the best I could find; it just happened to get in the shot (just below the main spar in the photo below) when I was documenting the windshield install. If you want to make the standoffs and install in the original location, I'd be happy to take some measurements for you, and take some better photos if that would help.

[Bruce Fenstermacher]

Miles got me thinking about that toilet bowl speaker housing.

On the right is fig 70a which shows that piece. A note in the IPC says it was optional serial 26996 and after. So you might conclude it was standard on all the other B models back to 20267. So while this piece isn't required in order to install the dome light on a 52, it does show that Cessna was not afraid to mount things to the cabin top as that was how the speaker was attached.

[jrenwick]

When I replaced my speaker many moons ago (A LONG time before I knew the speaker could be re-coned), I used one from an old cheap stereo I had when I was a teenager....

A friend of mine tells a story of replacing the speaker in his Cessna 140 with a speaker from Radio Shack or some such. It turned out to have a big enough magnet in it that the compass couldn't be swung to any accuracy. Be careful out there!

[GAHorn]

When I replaced my speaker many moons ago (A LONG time before I knew the speaker could be re-coned), I used one from an old cheap stereo I had when I was a teenager....

A friend of mine tells a story of replacing the speaker in his Cessna 140 with a speaker from Radio Shack or some such. It turned out to have a big enough magnet in it that the compass couldn't be swung to any accuracy. Be careful out there!

That sounds like another anecdote to me. But... the problem with aftermarket speakers is that the original used a special, integral bracket which accomodated the mounting screws. Aftermarket speakers do not, and this makes it a bit more complicated to mount them in the same manner as original.

[jrenwick]

That sounds like another anecdote to me....

Yes, it's an anecdote, but it's the first-hand experience of a man I trust -- former Navy pilot, Alaska bush pilot, CFII, current airline pilot, C140 owner. Not a "FOAF" story at all.