The International Cessna^® 170 Association

ronjenx wrote:

N9149A wrote:So the BIG question is has anyone had any problem with the Cessna steel mounts?

How about this:

Cut a piece of cardboard the shape of your panel.
Stick a steel screw (about the same mass as the steel panel mounts) in each corresponding location.
Hold the cardboard in place, then pull it away. See if the magnetic compass moves.
Do this with the aircraft pointing in the 4 or 8 major compass directions.

That should tell you if the steel will be a factor.

Wouldn't this depend on if the steel has become magnatized or not? I can see where a new part might not be magnatized, but after a few years could become magnatized. Just wondering. My mounts have brass studs - think they came from Wag-Aero.

bsdunek wrote:

ronjenx wrote:

N9149A wrote:So the BIG question is has anyone had any problem with the Cessna steel mounts?

How about this:

Cut a piece of cardboard the shape of your panel.
Stick a steel screw (about the same mass as the steel panel mounts) in each corresponding location.
Hold the cardboard in place, then pull it away. See if the magnetic compass moves.
Do this with the aircraft pointing in the 4 or 8 major compass directions.

That should tell you if the steel will be a factor.

Wouldn't this depend on if the steel has become magnatized or not? I can see where a new part might not be magnatized, but after a few years could become magnatized. Just wondering. My mounts have brass studs - think they came from Wag-Aero.

The truth is anytime you take your instrument panel apart and replace anything including mounts, your magnetic compass must be reswung.AC43-13. Doug

My old '56 172 has the same rubber instrument panel mounts as the 170's. While I can't give specifics, I think all of them will sag as time goes on and gravity does its thing. The IA who recently did my avionics & wiring work told me that if I ever wanted to remove the old mounts to just go back with bolts because modern instruments (he says ) don't need to be shock mounted like they did when our planes were built in the 1950's. I am not saying he is right or wrong, but he has a 195? Bonanza & a late 1940's Navion for which he has replaced the original instrument panels with new ones and he eliminated all shock mounts on the new panels. He has also built new panels for several other Navions & Bonanza's using the same method and as of this date hasn't had any difficulties. Any opinions on his theory?

170C wrote:My old '56 172 has the same rubber instrument panel mounts as the 170's. While I can't give specifics, I think all of them will sag as time goes on and gravity does its thing. The IA who recently did my avionics & wiring work told me that if I ever wanted to remove the old mounts to just go back with bolts because modern instruments (he says ) don't need to be shock mounted like they did when our planes were built in the 1950's. I am not saying he is right or wrong, but he has a 195? Bonanza & a late 1940's Navion for which he has replaced the original instrument panels with new ones and he eliminated all shock mounts on the new panels. He has also built new panels for several other Navions & Bonanza's using the same method and as of this date hasn't had any difficulties. Any opinions on his theory?

Doesn't sound right to me.
Wouldn't such a change require some approval paperwork?
Not all instruments in use today are "modern".

I have found a good source for the instrument panel shock mounts - Trimcraft Aviation. They sell List for $3.15 and can provide to dealers for $1.89.

Website http://www.trimcraftaviation.com/products.htm

And minimum order $20. They have lots of other useful items too.

I forgot to mention - I have seen panel installations using the shock mounts, but where the weight of the panel itself is suspended from above and behind by a heavy long spring. Thus the sideways (down) load is taken off the shock mounts.

The shock mounts can typically hold a load of 20 pounds in inline compression, but only 3 pounds in shear - sideways - load, which is what the panel exerts on them. As they age that capacity will drop a lot. So having the spring takes that load off of them.

I have 170B model and need to replace broken shock mount. Ordered Lord mounts, but the rubber is 1/2 in. And the ones in my panel are 3/4 in. Cessna said their mounts are same as Lords and the difference is the rubber will stretch after several years. I find it hard to believe that the rubber on all 10 mounts would stretch to 3/4 in over the years. I could replace all 10 with the Lords however I have a problem with spacing on an instrument. There is no room to reduce the space a 1/4 in. Does anyone have a recommendation or different supplier for the mounts??

Could you fit a 1/4" plastic spacer behind the one to make it the same length as the others?

These are the ones I used when I did my panel but it was all of them at once.
http://www.aircraftspruce.com/catalog/i ... ckkey=6334

bagarre wrote:Could you fit a 1/4" plastic spacer behind the one to make it the same length as the others?

These are the ones I used when I did my panel but it was all of them at once.
http://www.aircraftspruce.com/catalog/i ... ckkey=6334

Or instead of plastic spacers just spin a plain nut all the way on each side then install. This will only work of course if the studs are long enough to still get a nut on each side to hold it all together.

Instrument panel rubber shock mounts with 8/32 screws are available from Grainger for a whole lot less than Cessna.

blueldr wrote:Instrument panel rubber shock mounts with 8/32 screws are available from Grainger for a whole lot less than Cessna.

Yes. Go to www.grainger.com and search for vibration isolators. Some of them have one or both ends with female threads, which would allow you to add a threaded shaft with spacers to give you what you need.

Bruce Fenstermacher wrote:

bagarre wrote:Could you fit a 1/4" plastic spacer behind the one to make it the same length as the others?

These are the ones I used when I did my panel but it was all of them at once.
http://www.aircraftspruce.com/catalog/i ... ckkey=6334

Or instead of plastic spacers just spin a plain nut all the way on each side then install. This will only work of course if the studs are long enough to still get a nut on each side to hold it all together.

Now I remember.
Wasn't my idea but another reason to be a member of this club

http://cessna170.org/forums/viewtopic.p ... =15#p71277

You should probably buy one of these to make the spacers. Tools are always useful:http://www.elitetools.ca/en/product/met ... gQodxbsA1A

Has anyone used the steel stud shock mounts from Spruce or Grainger? Did you have any compass issues?

Thanks.

Frank

The original mounts are brass with brass nuts and are cheaper then the steel.
http://www.aircraftspruce.com/catalog/i ... ecfer=9802