Hello, I have a 1954 C170B with the original C-145 engine.
I am about 70% done with a total remanufacture (OK, restoration) of the girl and am about done with the panel. I am about ready to put the firewall on and then the engine to finish it up.
My question is this: I am really wanting to put on a new stainless steel firewall. I have spoken with the FAA and they said I could do it but it would be easier if I could get them a tail # of a C170 that already has it done. That way, we could basically modify the paper already done on it with our own information.
The reason I have first thought about doing this is because I noticed in a few pictures of a 180 HP conversion that they had a new firewall in the plane but it did not have any of the factory "flutes" that my origninal firewall had for stiffness. It was basically just a flat piece of metal polished. I am curious if that is only covered with the conversion STC of it was just a 337 issued during the engine change.
As always any and all help on this topic would be greatly appreciated.
Several years ago I visited Del-Air in Porterville, CA. Harry Delicker said he had a hydropress that he used to form stainless steel firewalls. Whether he has a PMA to manufacture them is another question. His number is (559) 784-9440. Schedule a free hour before you call him--he likes to chat!
All of the firewalls were stainless. The roll-formed stiffness beads
could be easy enough to form (with the right equipment/tools).
I have a roll-form beading machine (with a number of different
sized dies) that would make quick work of manufacturing a new
firewall out of the proper gauge thickness of stainless sheet....
Needless to say, I don't suppose new 170 firewalls are available
from Cessna....?
If you're going to replace the firewall with an "owner produced
part", I'd highly suggest replicating the re-enforcement beads
per the original firewall (long story short, replicate the original
part down to a T). The firewall itself is a load-bearing, "monocoque"
element of the complete structure, and as such, any replacement
piece fabricated should have the same form/function/stiffness/strength
as the original piece.
Bela,
I just went to my shop to check my firewall--slightly rusty and magnetic. It seems to be made of .020-.025" galvanized steel. I like the idea of replacing it with stainless. On one of the links to this site I saw a member had removed his firewall and had it regalvanized--it looked great. I found some galvanizing paint at Home Depot but havn't tried it yet. Still debating on whether to replace the whole thing since it has more holes in it than swiss cheese. How hard is it to find a roll-form beading machine? Would this be a common tool at a machine shop?
n2582d wrote:Bela,
I just went to my shop to check my firewall--slightly rusty and magnetic. It seems to be made of .020-.025" galvanized steel. I like the idea of replacing it with stainless. On one of the links to this site I saw a member had removed his firewall and had it regalvanized--it looked great. I found some galvanizing paint at Home Depot but havn't tried it yet. Still debating on whether to replace the whole thing since it has more holes in it than swiss cheese. How hard is it to find a roll-form beading machine? Would this be a common tool at a machine shop?
Gary Friesen
Interesting... Now I have to go check mine to see if it is
magnetic! I thought they were all stainless.... We removed
the firewall from a '53 C-180 project recently and I know at
least it is stainless.
Harbor Freight Tools has (had?) a bench-mounted, hand-cranked
roll-form beading machine available for awhile (don't know if they
still have them....).
Harbor Freight's website has this available: http://www.harborfreight.com/cpi/ctaf/D ... mber=34104
Is this what you have Bela? The beads on my firewall are around 1.25" wide--much wider than what this tool can form.
A couple of additions to my previous post. The paint I bought from Home Depot is "Rust-oleum Cold Galvanizing Compound" in a spray can. It claims to be "93% pure zinc in dry film" offering maximum corrosion protection and excellent adhesion to galvanized metal". For those that want to restore their firewall the right way see the firewall in these photos: http://www.birdofprey.us/pages/2/index.htm
"Hot dipped galvanized" is the only galvanized. That spray-can stuff is just paint with zinc in it. Which is not to say it will not help protect the firewall. Just don't con yourself into believing that it's the real deal.
My boss (I work in construction) tried to get away with rattle-canning some structural steel for one of our jobs with that stuff,when it was rejected his explanation was "the spec's didn't say HOT-DIPPED galvanized". Needless to say,that didn't cut any mustard with the inspector. And rightfully so. ( I warned him......)
From what I have heard,I thought that all Cessna factory firewalls were galvanized steel.
BTW,the "bird of prey" website documents the restoration of member Guido Perla's 170A. He lives on Vashon Island WA. The restoration work is kinda stalled out now,so it might be a while....
The firewall sheet (pre-formed) PN 0513101-1 is available from Cessna thru Hill aircraft for $365. http://www.cessnaparts.com/ It is galvanized. The stainless firewalls may be a solution for those plagued by compass errors due to magnetising.
I've used the cold-galvanizing sprays in fairly corrosive environments and it's pretty good if there's no abrasion going on. I've sprayed it on bare angle iron in a seacoast environment and 9 years later there's no sign of deterioration or rust. The angles I did not spray are heavily coated now in rust.
'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.
n2582d wrote:Harbor Freight's website has this available: http://www.harborfreight.com/cpi/ctaf/D ... mber=34104
Is this what you have Bela? The beads on my firewall are around 1.25" wide--much wider than what this tool can form.
A couple of additions to my previous post. The paint I bought from Home Depot is "Rust-oleum Cold Galvanizing Compound" in a spray can. It claims to be "93% pure zinc in dry film" offering maximum corrosion protection and excellent adhesion to galvanized metal". For those that want to restore their firewall the right way see the firewall in these photos: http://www.birdofprey.us/pages/2/index.htm
Yeah, that's the tool. FWIW, seems like it wouldn't be too difficult
to fabricate a die set to replicate the beads you have (know anyone
with a lathe who likes to drink beer?).
That being said, I think I'd opt for a $365 new one (by the time
you buy the beading tool, fabricate dies and buy a box of beer,
I bet you'd be real close to that amoun!).
Many grades of stainless are magnetic. I examined my firewall today and think it is an aluminum coated steel. As I recall this was a practice during that period. I think it was pure aluminum and don't know how it was applied. It makes sense to do it that way as it helps prevent galvanic corrosion. I believe that the beads were put in with an expensive sheet metal machine I can't remember the name of. The key to that machine is making good dies. Expensive. To try to roll a bead that size and depth with a Pexto type machine will most likely produce a potato chip. Another alternative to the forgotten machine would be stamping or hydro. I'm probably just going to do the best silver paint job I can do and live with it.
So everybody out there has their original firewalls still in? I was hoping that someone who has restored their plane would have done something in regard to putting on a new one that wasn't from Cessna.
Look at this guys firewall. This is a C170A with the 180 HP conversion. He just has a square of aluminum angle riveted on to the firewall for stiffness. Its in tradeaplane online, does this look legal to any of you?
Those angle stiffners are called out in the STC for the 180 conversion. The A model has fewer rolled and angle stiffners and the top ones he shows in his photo are for the A whith the conversion. The B has a horizontal one about ten inches down stock from the factory that makes the angled top ones unneccessary.
I can't make out in the photo if the firewall is stock or not but it seems like it has no rollled in stiffners.
I looked for & couldn't see any stiffening beads on that firewall either. Man,that guy's pretty proud of his A model,judging from the price!
FWIW,my firewall (48 model) is magnetic,appears to be galvanized steel or maybe aluminized steel. Has stiffening beads in various places.
