Posted: 10/13/2010 10:59:31
Has anyone ever used titanium for their firewall? If so which titanium did you use --- commercial pure or 6AL-4V? Where you able to find titanium rivets, or did you use something else? What challenges did you encounter fabricating titanium?
Thanks for your help.
Posted: 10/14/2010 22:06:00
I have not and probably would not consider titanium for a fire wall. But I have not build an airplane yet, so have a huge grain of salt with what I say!
I recall that titanium is much more expensive than other aircraft metals in common use.
I also understand titanium is much more difficult to work, weld, or machine.
Stainless Steel or mild steel with corrosion resistant coating is easier to obtain, fabricate, and in common use as a fire wall material. That my 2¢, take it for all that it is worth!
Posted: 10/14/2010 22:25:49
I have worked a little bit with titanium. I understand that others have built their firewalls out of it because of its light weight, great corrosion resistance and resistance to high temperatures.
It is difficult to work with because of its high abrasion to tools.
1. I have found that it requires about half the drill speed of steel and lots of pressure and cutting fluid.
2. If you can find some of the stuff at a scrap yard, do so, if it is the right dimensions and thickness.
3. It can be formed, but with care.
4. aluminum or stainless steel rivets will work.
Posted: 10/15/2010 11:17:59
Consider the temperatures at which the metals burn ... ignite would be better, but this is what I found on the web:
Titanium: 2,190 °F
Steel 2498 °F .. (Steel wool)
Magnesium autoignition at 1,166 °F ... burns at 5,610 °F
Looks like aluminum is a good choice considering Cost, Weight and Temperature. I was cutting a lawnmower magnesium housing in half to place in the trash. A steel bolt was cut in the process. The red-hot, piece of steel "skated" across the magnesium housing creating extra sparks and was self-sustaining as it bounced around. I had to flip the bolt off the housing. Magnesium made a great housing but it also is used in fireworks. I was lucky.
S. Steve Adkins, EAA 9221
Posted: 10/15/2010 11:34:59
Modified: 10/15/2010 11:35:58
Well, I definitely wouldn't want to use magnesium. The FAA recognized titanium as a viable firewall material and not aluminum because of melting temperatures, which become a concern well before ignition temps do. Here are some melting temps to contemplate:
Material Melting temp.
301 Stainless Steel 1/2H 2590 deg. F
304 Stainless Steel 2650 deg. F
Com’l. Pure Titanium 3040 deg. F
6AL-4V Titanium 3000-3100 deg. F
1008 Steel (mild) 2600-2700 deg. F
4130 Steel 2600-2760 deg. F
Not Acceptable for Firewalls
2024-T3 Aluminum 950-1180 deg. F
6061-T6 Aluminum 1080-1200 deg. F
7075-T6 Aluminum 890-1180 deg. F
The workability problems with titanium are a clear deterrent, as is the cost. On the other hand, it resists heat very well and saves about 2 pounds compared to a similar stainless steel firewall. I am just trying to find someone with hands-on experience to tell me how much trouble it was to work with.
Posted: 10/15/2010 12:38:54
Dave, probably the best folks to direct your question to would be the F. Atlee Dodge bunch -- I bought one of their PA-18 titanium firewalls from them, and it didn't seem to be any harder to drill a bunch holes in (around the flange to attach the boot cowl to) than any other material. As you can see in the attached pictures, the flange was formed from / as part of the firewall, and they 'fluted' the curves to follow the drawing dimensions.
Posted: 10/15/2010 12:58:47
Thanks, Andy. I see from the photo that they used comm. pure titanium, which is much softer than 6AL-4V. I'll get ahold of them and see what they charge for one of these.