flyrotary@lancaironline.net Mailing List Archive

If you are not yet expert at welding 4130, might I suggest welding with Oxy acetylene gas torch. This is a slow process and there is plenty of time for heat to build up outside of the weld area. Then drape the weld with a ceramic cloth to hold in the heat and prevent local air currents from chilling the weld. If the parts being welded are small enough drop them into a metal box full of lime. This will slow the cooling process to an hour in some casses. Of course never cold quench a part in water or let it sit where cold air can blow on it.

It is typical to have an alloy part very hot before welding begins. If not the TIG weld is very hot, but in just a tiny space near the weld. And then as the weld shrinks and applies immense forces onto the local area, cracks appear right around the weld bead. A great looking TIG weld can fail with a light hammer blow if it has been chilled right after the weld process is completed. A good looking sprint car cage can turn into a kit when inverted at speed. Close off the area to be welded with drapes to control air movement and to protect the eyes of onlookers. The first time you flash yourself will be memorable. Your eyes feel as though sand is stuck in them for a whole day. Try to get off of an autodarkening lens and into a regular helmet. Use the foot pedal even when it is not required for power control. If it saves your eyes just one time each week it is good.

Lynn E. Hanover

In a message dated 4/13/2016 3:00:41 P.M. Eastern Daylight Time, flyrotary@lancaironline.net writes:

Dave,
Using the propane torch is OK. This is all you can do if the parts are still together. It is also a great idea to preheat many parts if possible. (Super important if you do TIG aluminum welding.) Check some of the suggestions in a welding book for the needed temperature. You might need MAAP gas to get the area hot enough. If you do a fully welded engine mount from scratch it is suggested, (if you use 4130 Chr/moly), to heat treat the full assembly. The need can be overstated, since we are in the era of litigation all literature will suggest the max! The thing is the high strength steels are more prone to notch sensitivity and crystallization. I really like the racing books from Carroll Smith. Great advice and practical too. I love his "Engineer to Win" for down to earth engineering advice. Great metallurgical advice. Amazon has all his books. I love my TIG. The only way to weld!

Bill Jepson

On Wed, Apr 13, 2016 at 11:39 AM, David Leonard <flyrotary@lancaironline.net> wrote:

on gosh, that adds another wrinkle... Can I use a generic propane torch?

Dave Leonard

On Tue, Apr 12, 2016 at 5:09 PM, William Jepson <flyrotary@lancaironline.net> wrote:

Dave,
The tig is great. One thing to remember is to anneal the area around welds whenever possible. Tig allows you to weld many metals but annealing prevents cracking right next to the weld later. If it is a motor mount it is a good idea to shot peen as well.

Bill Jepson

On Apr 12, 2016 5:02 PM, "David Leonard" <flyrotary@lancaironline.net> wrote:

Charlie,
Your post below reminded me that I wanted to thank everyone who suggested I get a TIG system rather than some other form of welding set-up. After getting up to speed on the benefits of the different types of welding, it is clear that TIG was the only solution for my needs (most versatile and most appropriate for the lighter gauge metals used in aircraft). After spending a couple weeks learning to not destroy everything I touch with it, I can finally create ugly looking things that would loosely fall into the category of a weld. But is is fun, and great to have the ability to fix a lot of things that were previously thrown out or limped along with JB weld.

I have been able to repair cracks in my exhaust system and beef up my 4130 engine mount, not to mention a ton of projects at home.

Wish I did it sooner.

David Leonard

On Tue, Apr 12, 2016 at 3:28 PM, Charlie England <flyrotary@lancaironline.net> wrote:

Several years ago, some rotary users tried various flattened exhaust tips, as seen on a lot of European homebuilts. (Supposed to help with making exhaust tone less irritating.) IIRC, everyone found that the rotary would destroy the tips very quickly. Well, while walking through the Fantasy of Flight museum about a week ago, I noticed these tips on (IIRC) a P-40. Looks like they maintained a curved shape but were still able to have the pinched outlet. Don't know if it would actually work with a rotary, but it should have a better chance than the purely flat tips.

Charlie

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