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  #1  
Old 11-19-2018, 09:37 PM
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N941WR N941WR is offline
 
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Default Tip-up Lift Strut Test

There has been a lot of talk about adding quick release for the lift struts on a tip-up, should the canopy need to be jettisoned.

I just ordered a new set of lift struts for my canopy, thus I will so have a pair that we can experiment with.


I was thinking of taking a flat foot sheet of plywood approximately the size of the canopy and hinging it at the bottom, attaching the struts 1/3 of the way from the top and securing them on a trailer and see at what speed they pull out.

I suppose I could make the sheet half the width and mount the strut in the vertical center of the sheet so I can run two tests.

Dan, you are much better at this than me, do you or any others have a suggestion for running this test?

My theory is that the struts will pull apart at a fairly low speed.
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  #2  
Old 11-20-2018, 06:13 AM
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snopercod snopercod is offline
 
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I'm unclear on what you are trying to do here. Are you trying to verify how many pounds the strut is pushing with?
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  #3  
Old 11-20-2018, 07:31 AM
Desert Rat Desert Rat is offline
 
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If you're just looking to simulate an air load to see where the struts come apart, seems like a more actuate way to measure that would be to just hang a strut from one end and then keep piling weights on the other end until it separates.

On the other hand, it sounds like a fun project from the standpoint of getting to test something until you break it, so I vote for that option, preferably with a camera or two filming in slow mo...
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  #4  
Old 11-20-2018, 08:21 AM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by Desert Rat View Post
If you're just looking to simulate an air load to see where the struts come apart, seems like a more actuate way to measure that would be to just hang a strut from one end and then keep piling weights on the other end until it separates.

On the other hand, it sounds like a fun project from the standpoint of getting to test something until you break it, so I vote for that option, preferably with a camera or two filming in slow mo...
Terry,

Exactly what I was thinking but running down the runway until the thing rips free sounds like a lot of fun.

Maybe we will do both a pull test and a truck test. Cameras will be in the mix, for sure!
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  #5  
Old 11-20-2018, 08:23 AM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by snopercod View Post
I'm unclear on what you are trying to do here. Are you trying to verify how many pounds the strut is pushing with?
A number of people feel the need to add complex quick release mechanisms to the lift struts because they feel they are needed to jettison the canopy.

My contention is that those struts will pull clean with very little force.
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  #6  
Old 11-20-2018, 09:03 AM
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N941WR N941WR is offline
 
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If any of you have struts you are willing to donate to the cause, PM and I'll give you my address.
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  #7  
Old 11-20-2018, 09:39 AM
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Bill Boyd Bill Boyd is offline
 
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Default Bill, Bill...

Make this easier on yourself (and provide the rest of us with better video to watch later): call Myth Busters with your suggestion.
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  #8  
Old 11-20-2018, 10:27 AM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by Bill Boyd View Post
Make this easier on yourself (and provide the rest of us with better video to watch later): call Myth Busters with your suggestion.
The thought crossed my mind but they got rid of the hot redhead!
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  #9  
Old 11-20-2018, 11:29 AM
Desert Rat Desert Rat is offline
 
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Not trying to take over your project here, but if you do this, it would be nice if the test article simulated the canopy and airframe attach points as well as the relevant airloads. That way you could get some idea of whether the strut is going to come apart in the middle, or would it fail at one of the attach points first?

I don't have a dog in this hunt (yet) but it seems to me that if I were in the middle of this particular catastrophe, I'd prefer that the struts yank out of the airplane and depart with the canopy, rather than coming apart in the middle and either spritzing me in the face with whatever oil and spring combo is inside of them, or flailing around and beating me in the face as I'm trying to deal with a crashing airplane.
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  #10  
Old 11-20-2018, 12:38 PM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by Desert Rat View Post
Not trying to take over your project here, but if you do this, it would be nice if the test article simulated the canopy and airframe attach points as well as the relevant airloads. That way you could get some idea of whether the strut is going to come apart in the middle, or would it fail at one of the attach points first?

I don't have a dog in this hunt (yet) but it seems to me that if I were in the middle of this particular catastrophe, I'd prefer that the struts yank out of the airplane and depart with the canopy, rather than coming apart in the middle and either spritzing me in the face with whatever oil and spring combo is inside of them, or flailing around and beating me in the face as I'm trying to deal with a crashing airplane.
Terry,

That is the plan. I hope to simulate the canopy airload with plywood.

The challenge will be the shock loading when the "wind" gets under the front of the canopy rather than ramping the airload up slowly as we accelerate our test right.

I'm 99% sure they will pull apart, leaving a skewer behind.
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