Lift strut pictures and info

[Guest]

Here are some pictures of a lower front strut section. That bolt fitting on the end has been bent as you can see. I call the tab that sticks out the bottom and has the bolt hole in it the bolt fitting.

Also notice that there are two small drain holes on the bottom of the strut fore and aft of the bolt fitting.

The bolt fitting appears to be made from the steel plate about 3/32" thick that is welded to the bottom of the strut. You can see it in the inside photo attached, its the steel plate inside the tube.

The bolt fitting is thicker on the outside of the tube than it is on the inside. The reason for that is because the butt end of the tube (I drew a black loop on it) is a flat plate that has been welded on to close off the bottom of the strut tubing BUT is really not a flat plate at all rather it is an "L" shaped plate. It bends about 90 degrees and one leg of the "L" actually runs parallel to the plate that you see internal to the tube and is welded to it. Thus the bolt fitting is thicker than the piece that's in side the tube because it consists of two pieces. The other leg of the "L" is welded to the butt of the strut to close it off. So that piece with the black loop drawn it is one "L" shaped piece. Hope that makes sense to you.

This strut is NOT rusted inside.

This strut was from and F model made in the early 80's as I recall.

The wall is about .036" to .038" best I can tell but the cross section was very big. I have some the full cross section tube around I can measure later. I think it was 3.9" front to back much bigger than the 3.3" you are used to but in the 80's that was what they had to work with.

[Guest]

Re: Lift strut pictures and info

The bolt fitting is welded in on both sides on the top and both sides on the bottom that makes 4 welds.

Each weld line is about 2" long.

MIL Handbook #5 allows this load => P=32,000 x L x t

Well actually my aircraft structures text gives this formula and says it comes from MIL Handbook #5 but I am too lazy to double check so I will believe it for now. My paper version of MIL Handbook #5 is in North Carolina so I have to double check using a version on softcopy. I hate doing that on a computer so I believe the text for today.

P=32,000 x L x t assuming low carbon steel struts were allowed.

L=2" and is the weld length

t=.038" and is the thinnest metal piece being joined.

P=32,000 x 2 x .038 = 2432 per weld

total load the welds can hold= 2432 x 4 = 9728 pounds tension or compression

Oh yeah, forgot, no fitting factors or any other factors have been applied.

[tawadc95]

Re: Lift strut pictures and info

the weld in pic 4 on top l to r looks broke..did you do that or did it happen on it's own? you can see between the weld and the parent material at the bottom of the weld is what I am seeing.

[Guest]

Re: Lift strut pictures and info

the weld in pic 4 on top l to r looks broke..did you do that or did it happen on it's own? you can see between the weld and the parent material at the bottom of the weld is what I am seeing.

Its not a break but good eyes!

It is a piece of long thin debris left over form the cut off operation when the strut was made. It got tucked inside before welding and creates that illusion for the camera. In real life it is easier to see.

If you ever see a tube cut with an abrasive cut off wheel you will see this type of debris caused by the wheel. Often it is removed with a deburring tool, file, grinder...

[N96337]

Re: Lift strut pictures and info

Thanks for the post, Dave...good job!
JH

[Ragwing nut]

Re: Lift strut pictures and info

The tab is two equal sized plates merged to make one thick one. The one plate extends into the strut and carrys most the tension load. You can see where the tab is welded on edge the full length. The other is bent at a 90* angle to form the other half of the tab and the strut close out. The front strut attachment is made very similar. That strut is a good example of corrosion on the outside, but none on the inside.

Mike

[Guest]

Re: Lift strut pictures and info

The tab is two equal sized plates merged to make one thick one. The one plate extends into the strut and carrys most the tension load. You can see where the tab is welded on edge the full length. The other is bent at a 90* angle to form the other half of the tab and the strut close out. The front strut attachment is made very similar. That strut is a good example of corrosion on the outside, but none on the inside.

Mike

Mike this is a front strut. I had described the "L" shaped piece best I could but added a phrase or two from your description to make it more clear, Thanks, Dave.

[Ragwing nut]

Re: Lift strut pictures and info

That is positively a rear strut. The front strut tab is located approximately in the center of the strut, and has a welded miter cut on the back side to clear the rear strut.

Mike

[Guest]

Re: Lift strut pictures and info

That is positively a rear strut. The front strut tab is located approximately in the center of the strut, and has a welded miter cut on the back side to clear the rear strut.

Mike

Hi Mike

blue text above- Yes it does you are absolutely correct, just like the mitered cut that is welded up on the trailing edge of this strut as seen in picture 2 thru 5

red text above - the reason this looks odd is because the strut material is very wide almost 4" as compared to the 3.2" (approx.) original tube. They must have put the tab aft of center so the struts could converge at the fitting. That was the tubing t-craft went to for a while in the 80's.

Hope that clears it up.

I cut this piece off the bottom of a T-craft front lift strut myself and used the rest to do a repair.

[Forrest Barber]

Re: Lift strut pictures and info

THIS is good information for the group and the FAA will see it too!
those pieces are numbered A-8136 , A-877, A-879 A-82 etc... for front & rear struts , later on E.O.'s were produced to change that angle on the rear strut for the different cross sections. I do appreciate the stress nalysis input, We did do proof testing at the factory on material strength and that was quite interesting.