Chrome Moly 4130 Motor Mounts - Prefab Parts?

[cwilliamrose]

The homebuilding movement never would have happened (and we wouldn't be here discussing this) if the welding required a certification.

[Aaron Novak]

Hi: I am an aircraft mechanic and certified Non Destructive Testing Specialist (x-ray weld Inspector) with 40 years of experience. I don't usually comment on forums like this, unless I see a problem that is personal safety related. In the case outlined here 'welding an aircraft engine mount' - unless you are a certified AIRCRAFT welding specialist (either AWS or CWB), you should not be welding any LIFE CRITICAL components. You could be risking not only your life, but any passengers, or innocent bystanders on the ground, when you fall out of the sky. If you intend to continue with this folly, at least go out and buy the best Ballistic Recovery Parachute you can find, plus no passengers and no flying over populated areas.

Every certified aircraft engine mount was designed by an aeronautical engineer, a welding engineer, as well as a level 3 welding inspector. Each has a specific area of expertise. It starts with the computer design and testing of the mount and they will use stress analysis to make sure there are no weak spots in their design. Then a welding jig will be designed and built by the welding engineer and level 3 weld inspector, as well as the weld procedures, which a certified aircraft welder will follow to the letter. The procedure outlines the specific filler rod, the amperage settings, the speed and angle of the welding process etc etc etc. It follows with dozens of trial and error tests to make sure the welds will hold in the most impossible situations you can imagine. All this preparation before they even begin to weld the mount.

Welding is never as easy as it looks, especially on LIFE CRITICAL components. My recommendation - find a certified aircraft welder, who has extensive hands-on experience with this exact type of welding, as well as an approved weld procedure and welding jig. It does not matter how much it costs, if the end result is you do not kill yourself or others. OR the BRS is your last resort. I worked for two years in a helicopter search & rescue squadron - I carried more than my fair share of body bags.

I appreciate your input from a safety perspective, but I do have to disagree with you on a couple points. First off on engine mount design, considering the time period most GA aircraft were designed in, I doubt most were designed by an engineer. Most were designed by the designer/fab shop and later analysis was done for TC approval, and as they are really over designed it was never an issue. Now bigger AC and Military, oh you bet they had a team designing them. A lot of what you are talking of applies to new production, and if you look back in homebuilding, the homebuilders used to seem out info from the OEMS and learn as much as they could. Now is seems there is this attitude that being a homebuilder means they can ignore history and do whatever they want and it will be fine. As for being a certified welder.....im mixed on that. The AWS criteria is really just a copy and paste from the old Military and Civilian aircraft welding tests for being and airframe mechanic, back when they taught that. That being said the certification only covers whatever process they tested in. In reality what you need is to approach this with the right attitude, test and calibrate yourself and your equipment, and make the best decisions. In general I think homebuilders should be doing more engineering themselves, more analysis and more NDT type work instead of treating what they are building as a "hot rod" with wings.

[BoKu]

Hi: I am an aircraft mechanic and [blah blah blah]...

Trebuchet ride!

[Aaron Novak]

Trebuchet ride!

???

[BoKu]

???

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[Aaron Novak]

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Wow.......

[nixrox]

The homebuilding movement never would have happened (and we wouldn't be here discussing this) if the welding required a certification.

That is the reason so many pilots have ended up dead. Murphy's Law - if it can happen it will.

So if you are not a professional journeyman welder, EVERY weld you complete is marginal at best and blind luck if it holds.
Transport Canada dictates what welding is acceptable for an aircraft and so far everything I have seen says NO DEFECTS ALLOWED - none, zero, zip, nada.

If you have never taken any welding training courses, how can you guarantee that you used:
1. A proven weld procedure, the proper amperage settings and the proper welding or filler rod, whether MIG, TIG or STICK may have been the better choice
2. the proper metal stock that comes with the original chemical composition forms from the manufacturer
3. maybe the composition of the filler rod and the metal required you to preheat the base material before commencing welding and post welding heat to reduce HAZ cracking.
4. The welding you carried out might have required it to be stress relieved - which is a very long gradual heat reduction to reduce cracking
5. the list is endless and the potential defects are limitless

Which is why I have rejected thousands of welds and in several cases pushed welding companies into bankruptcy - because they could not weld to aircraft standards.

So once again - if you weld any parts on an aircraft and your are not certified as an aircraft welder - PLEASE do not take any passengers on your aircraft and never fly over a populated area. PLUS always fly with one hand on the BRS.

Have a nice day

[jim_p]

Seems a little over the top.

Do you have any actual data from the extensive FAA crash reports that backs up your alarming claims? Sounds like there should be quite a few documented cases of E-AB planes crashing due to failures of bad welds. I don’t doubt that it has happened, but I don’t recall it being in any of the lists of reasons for E-AB fatalities that the EAA, FAA, kit mfrs, and others have been working on diligently.

If you want to help people, educate them on the risks and proper procedures. Don’t come in and call everyone incompetent idiots if you want to be taken seriously.

[nixrox]

Like I said at the start of this - I never reply on these kinds of forums because I learned a long time ago that it is difficult to educate someone who thinks they know everything already - which has been clearly demonstrated by the above responses.
I see a number of glaring problems that are safety related and I express my opinion - if the people who read this forum reject my opinions (which are based on actual hands-on experience) I don't really care.
If they want to risk their own lives - I don't really care.
It is when they involve others - that is when it bothers me.

One last comment to the individuals who are TIG welding 4130 steel tubing - If you are not adding shielding gas (argon) to the inside of the tube in the same amount as the front side - I can pretty well guarantee 100 percent - there are a number of of oxygen induced defects in your welds. They will be full of porosity.

Which is why I intend to bring this matter forward to Transport Canada.
If you want to build an aircraft and you weld it yourself without any welder training or x-rays to prove the quality of the welds - then you should never be able to sell the aircraft, or carry passengers, or fly over populated areas.
If you want to commit suicide - knock yourself out - just don't take anyone else with you.

Twenty five years ago, I was asked by a friend of mine to x-ray the door frame tubing of a old Piper Cub he was considering purchasing. I found visual evidence of severe corrosion. To demonstrate - I took a ball point pen and was able to push it right through the tube at the worst area. How many people do you know have ever taken the time, when they are rebuilding an antique aircraft, to take a few x-rays of critical areas. That was the only time in my career and my friend did not buy that aircraft and no I did not charge him for the x-ray film.

[cwilliamrose]

Surprise surprise, no data to back up the panic.