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Aerospace Welder / Engineer recommended I not weld the W818 aileron rod.

Technically, you want any weld running parallel to the load being applied. So, the "fishmouth" puts the welds much closer to the direction of load, along the pushrod.

But.....an analysis of a "butt" weld around the circumference of the rod, assuming a 1/8" throat, gives a low enough stress in the weld that something else will fail before the weld does.

I think the weld is at least as strong as the root of the threads on the stud being welded to the rod itself.

The weld is just not a problem.
 
As to whether the vee cut is needed or not, you can calculate the strength for each weld configuration and see which meets the needs of the part. There's no need to make a stronger joint than is necessary, once you've considered all the loads and the cyclic environment.

The rule is, get it good enough and get on with things. The thing that's tricky is to define what's good enough. I'd build that part to the plans and not worry about it.

Dave
 
Grain has nothing to do with it, the angles are to put the weld in shear (more parallel to the load) and increase the weld area (length, really).

I don't think it's an issue; this is the way suspension components (push and pull rods, tie rods and a-arms) are made for most lower level race cars, and the loads there (for a given tube size) are much much higher.

Worrying about this just doesn't pass the smell test, my guess is that the threaded bit breaks off first... But we'll find out when I receive the parts and test them in the lab. I sometimes call the load frame the meter-o-truth...




jrs14855 said:
The majority of metals used in EAB construction have a grain. There are numerous references to grain and welding protocol. These include The Techniques of Aircraft Building, published by Acro Sport Inc, as well as numerous EAA Publications. The consensus of all this is that welding across the grain should be avoided to the extent possible.
AC43.13 does not specifically address welded rod ends. However the principals involved are the same as for welded steel tube repairs. Welded steel tube repairs are addressed in AC43.13 Pages 4-62 thru 4-78. In each example on these pages, the end of the tube is either a fish mouth(two 30 degree V cuts) or a scarf (30 degree straight cut). The purpose of this is to avoid, to the degree possible, welding against the grain.
Just one more reminder that several Aviat Pitts models are type certificated aircraft. None of the Vans Aircraft are type certificated. The testing and engineering that the Pitts aircraft were subjected to far exceed any similar process for any Vans model. I have to sincerely question any one who would choose and promote their own "empirically proven" method, which goes against decades of established protocol, on thousands of aircraft, many of them type certificated.
Regarding "Aerospace Welder" this is a rather meaningless generic term. There are many different categories of "aerospace welder" most of them having little or nothing to do with welding on EAB aircraft. If you refer me to someone who has every Aerospace Welding certification known to exist, now we are having a meaningful conversation. Aerospace Welder, as a stand alone statement, means nothing.
Click to expand...
 
Chuck,

I am looking forward to your test results with great interest. It is rare we get actual structural data on these airplane parts. I love the build 'em and bust 'em techniques. Until a part is tested to failure, one does not really know the capability of it. It is a fantastic feedback mechanism for design engineers.

Having spent some of my career in that arena, and years on study of HOW to validate, (FMEA's loads, frequencies, temperatures, shock, vibration etc) I have a soft spot for this arena. It is a true art form for yielding high performing, yet elegant, designs.

Oh - this has to be the longest and most contested thread ever for two approved options provided by the "factory". It was once said " i believe we are in vigorous agreement! "

Thanks for doing this.
 
BillL said:
Oh - this has to be the longest and most contested thread ever for two approved options provided by the "factory".
Click to expand...

I was thinking the same thing this morning when I logged on and saw yet another response to this thread.
 
Weld

David Paule said:
As to whether the vee cut is needed or not, you can calculate the strength for each weld configuration and see which meets the needs of the part. There's no need to make a stronger joint than is necessary, once you've considered all the loads and the cyclic environment.

The rule is, get it good enough and get on with things. The thing that's tricky is to define what's good enough. I'd build that part to the plans and not worry about it.

Dave
Click to expand...

This has very little to do with the strength of the weld. Welding with the grain, to the degree possible, is established protocol that probably goes back to the earliest aircraft 4130 structures in the 1930's.
Were the pushrod and the rod end made of mild steel, there would probably be no issues with the straight weld. But 4130 is a different situation.
Many years ago a friend decided to add some "reinforcing washers" that were not called for on the plans. These were main spar fittings for a well know design. After welding round washers to the flat 4130 fittings, someone raised some questions about the round washers. The builder magnafluxed the fittings, all were cracked around the washers. The cracks were no visible. The fittings were replaced with teardrop washers added, no cracks.
 
There could be many reasons for those cracks, none of which have anything to do with the strength of this welded joint, which is drastically different than that situation.

Dave
 
Welding

Thankfully Vans does not offer a Rag and Tube plane , Doug would have to set up a new Webb site devoted to Welding !!!

I decided to thread mine and screw them together !!! No rivets or welding required .
 
g zero said:
I decided to thread mine and screw them together !!! No rivets or welding required .
Click to expand...

You tapped the tube and turned threads on the insert? That gets my Spidey sense tingling, thinking about cracks in the bottom of the tapped hole....

Hopefully you're taking about something else...
 
jrs14855 said:
The majority of metals used in EAB construction have a grain. There are numerous references to grain and welding protocol. These include The Techniques of Aircraft Building, published by Acro Sport Inc, as well as numerous EAA Publications. The consensus of all this is that welding across the grain should be avoided to the extent possible.
AC43.13 does not specifically address welded rod ends. However the principals involved are the same as for welded steel tube repairs. Welded steel tube repairs are addressed in AC43.13 Pages 4-62 thru 4-78. In each example on these pages, the end of the tube is either a fish mouth(two 30 degree V cuts) or a scarf (30 degree straight cut). The purpose of this is to avoid, to the degree possible, welding against the grain.
Just one more reminder that several Aviat Pitts models are type certificated aircraft. None of the Vans Aircraft are type certificated. The testing and engineering that the Pitts aircraft were subjected to far exceed any similar process for any Vans model. I have to sincerely question any one who would choose and promote their own "empirically proven" method, which goes against decades of established protocol, on thousands of aircraft, many of them type certificated.
Regarding "Aerospace Welder" this is a rather meaningless generic term. There are many different categories of "aerospace welder" most of them having little or nothing to do with welding on EAB aircraft. If you refer me to someone who has every Aerospace Welding certification known to exist, now we are having a meaningful conversation. Aerospace Welder, as a stand alone statement, means nothing.
Click to expand...

I made this original post... I used the words Aerospace Welder loosely to describe the individual who is a welder, business owner and engineer... He provided advise and his opinion... The things going on in his shop are very advanced including projects but not limited to Boeing and NASA... I'm pretty sure there not using AC43.13 for there process specification. I guess you ran out of things to attack or disect... very interesting... :confused:
 
Jason, go easy. The why, or the specific need in this application may be subject to discussion, but the v-notch method is in fact standard procedure.

BTW, Jim flew his welding to to the EAA Convention in 1964, if you get my drift.
 
Just for the technical benefit of those interested. Dan shows a variation (v-cut) to the circumference weld that helps the strength of that approach (nice). I was taught (Carroll Smith) a slightly different approach and have done so for a long time; four staggered rosett welds along with the full circumference weld. This is a long accepted race car fab technique.
Side note; I have fabricated all steel parts in my aircraft and heat treated after TIG welding. The bill for heat treat was $100 (and that is for every single ferrous piece in the airframe). Of higher importance here is the selection of filler rod - ER70-S2.
 
DanH said:
Jason, go easy. The why, or the specific need in this application may be subject to discussion, but the v-notch method is in fact standard procedure.

BTW, Jim flew his welding to to the EAA Convention in 1964, if you get my drift.
Click to expand...

Haha sure thing:D
 
jj_jetmech said:
Haha sure thing:D
Click to expand...

Sorry...wrong drift, my fault. I was trying to say Jim has been building welded tube airplanes more than 50 years, which is something to be respected.

larryj said:
Side note; I have fabricated all steel parts in my aircraft and heat treated after TIG welding. The bill for heat treat was $100 (and that is for every single ferrous piece in the airframe). Of higher importance here is the selection of filler rod - ER70-S2.
Click to expand...

"Heat treated" can be a highly confusing term. Was the goal stress relief or a significant strength increase above the as-welded condition?
 
Welding

DanH said:
Sorry...wrong drift, my fault. I was trying to say Jim has been building welded tube airplanes more than 50 years, which is something to be respected.



"Heat treated" can be a highly confusing term. Was the goal stress relief or a significant strength increase above the as-welded condition?
Click to expand...

Dan- I understood you the first time. The last time I checked which has been a while, my welding was still flying in ND after 50 years. Couple of dozen others, I don't keep track of most of them.
Regarding post weld treatment, many years ago I had a number of visits with the then manager of Aviat Pitts. At that time they were not doing any post weld procedures on any of their welded steel structures. An article in
Sport Aviation a few years later confirmed this.
 
Quote:
Side note; I have fabricated all steel parts in my aircraft and heat treated after TIG welding. The bill for heat treat was $100 (and that is for every single ferrous piece in the airframe). Of higher importance here is the selection of filler rod - ER70-S2.

"Heat treated" can be a highly confusing term. Was the goal stress relief or a significant strength increase above the as-welded condition?

Dan you're right. "Heat Treat" can mean a lot of things. I had my parts "normalized"; this is the condition the base materials came in and I wanted to both stress relieve and make sure the weld zone had consistent and even distribution of the carbon - and this is why the filler rod is important. I'm reaching the limit of my technical knowledge here; I'm not well-versed enough to go into the austenitizing temperatures etc.

"Heat Treat" would commonly refer to taking the part to a higher hardness and tensile strength; 4130 has enough carbon to go to roughly RC40-42 and a maximum of RC48 and this would not be appropriate for our use here.
 
larryj said:
Quote:
Side note; I have fabricated all steel parts in my aircraft and heat treated after TIG welding. The bill for heat treat was $100 (and that is for every single ferrous piece in the airframe). Of higher importance here is the selection of filler rod - ER70-S2.

"Heat treated" can be a highly confusing term. Was the goal stress relief or a significant strength increase above the as-welded condition?

Dan you're right. "Heat Treat" can mean a lot of things. I had my parts "normalized"; this is the condition the base materials came in and I wanted to both stress relieve and make sure the weld zone had consistent and even distribution of the carbon - and this is why the filler rod is important. I'm reaching the limit of my technical knowledge here; I'm not well-versed enough to go into the austenitizing temperatures etc.

"Heat Treat" would commonly refer to taking the part to a higher hardness and tensile strength; 4130 has enough carbon to go to roughly RC40-42 and a maximum of RC48 and this would not be appropriate for our use here.
Click to expand...

Most 4130 welded tube structures shouldn't be heat treated past Rc 26-28 or so; certainly not higher if you haven't back purged, used 4130 filler, used lots of pre-heat, etc. That really requires complex parts to be heat treated in a fixture to avoid excessive wapring during the quench.

Most race car fabricators just do a normalization in the shop which consists of heating to a dull red glow with a propane or other large torch (to spread the heat out) then allowing it to cool as slowly as possible (putting it under a metal box to keep the breeze out works fine). Certainly doing it in an oven/furnace would be better, but usually isn't practical for large items. The goal, as alluded to above is to let the alloying elements get evenly distributed and to also allow the grain to reset, removing preload/internal stress and resulting in a better (tougher) weld, overall.
 
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Buckling is the weak link

I also wondered about the strength of riveting vs. welding of the ends of the W-818 so I decided to run the numbers and do a stress analysis on the pushrod system. The weak link in the system is "column buckling" of the tube. The buckling strength of a 0.50" X 0.035" 4130 Normalized tube (Length = 27.625") is approximately 520 lbf. This works out to about 10,170 psi in the tube. The shear strength of the AD4 rivets is approximately 3X stronger than what the tube buckles at and the "fastener bearing" (i.e., failure of the tube due to the rivet "smashing" the tube wall) is about 3.72X stronger than the buckling load. As far as the weld is concerned, it's not hard to get 10 ksi weld strength. The "fish mouth" technique described earlier on is the "preferred" method of closing out the tube but the "circumferential" weld would probably be fine.

I also did the analysis of the W-716 pushrod (1.125" X 0.035" X 69.281"). The buckling strength was 370 lbf. Rivet shear strength of the MSP-42 rivets was 5.46X stronger; the fastener bearing strength of the tube and VA-111 were 4.08X and 5.21X stronger, respectively. The thread pullout of the rod end threaded into the VA-111 (assuming a 370 lbf tension load and only 0.250" of thread engagement) was 6.05X stronger.

In both cases I used the "bearing yield" strength (e/D = 2.0) of the material for the fastener bearing calculations. The "bearing ultimate" strength will be higher. I used the ultimate allowables for the fastener shear calculations.

In short, I just riveted the ends in via the plans...

Jeff
 
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