Brake loads/Spring gear

[Alister Yeoman]

Hi Alex,
Pleased to hear you had a good time in NZ, when you are back
next look me up, it would be a good excuse to go for a fly!!!:-)

And Brian, I actually had my money on Paul Cayard. it was a bit of a
surprise

Cheers All

Alister

-----Original Message-----
From: AzAlexR@aol.com <AzAlexR@aol.com>
To: murphy-rebel@dcsol.com <murphy-rebel@dcsol.com>
Date: Tuesday, February 08, 2000 2:38 PM
Subject: Re: Brake loads/Spring gear




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[Dan Morehouse]

Hello!

I originally sent this in but didn't get see any response, maybe because nobody got it, although it does appear in the archive

Dan

----- Original Message -----
From: Dan Morehouse (DanMorehouse@home.com)
To: Murphy Rebel Builders List (murphy-rebel@dcsol.com)
Sent: Wednesday, February 02, 2000 12:25 PM
Subject: Re: Brake loads/Spring gear


Oooh! I think I'll wait to install my SG-13, in that case.

Thanks for the feedback, Alister. Look forward to hearing what you come up with.

Take care,
Dan
R280

----- Original Message -----
From: Alister Yeoman (yeoman@voyager.co.nz)
To: Murphy Rebel Builders List (murphy-rebel@dcsol.com)
Sent: Tuesday, February 01, 2000 1:29 PM
Subject: Re: Brake loads/Spring gear



Hi Dan,
Sorry about the delay I got a little tied up for a few days. Yes the last message was the first.

Thats right, about 2" back from the end of the fingers along the rivet line connecting to the floor bulkhead there is fatigue and working rivets.

I intend to run the 63 thou SG-13 well back to probably the double bulkhead further back. The reason being if the brakes are applied and you get someone to push backwards and forwards on the prop simulating braking loads the lower floor skin 'pants' quite badly. The floor skin probably does not need to be this heavy but remember I want to repair this without pulling the carrythough apart so I am limited in the way I can approach the problem.

I am not entirely happy with the doubler on the side panel fix, as you are asking the doorpost to accept the majority of the load of the braking, this is putting a lot of stress on the wing strut attach brackets ( remember these join the bottom carrythrough to the doorpost). Once again when you apply the brakes and push backwards and forwards on the aircraft it is possible to feel the strut attach bracket flexing, over time this could ( will?) lead to cracks forming.(not a good place to get them!)

All I can say at this time is that I am still working on the problem, I have the plane out of the air now and will progressively add strength to the area until I am satisfied. The end mod may end a little radical!! I will keep you posted.

Cheers

Alister

-----Original Message-----
From: Dan Morehouse <DanMorehouse@home.com (DanMorehouse@home.com)>
To: Murphy Rebel Builders List <murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)>
Date: Sunday, January 30, 2000 12:02 PM
Subject: Re: Brake loads/Spring gear


Hello Alister and company!

...On further inspection distortion of the outer floor skin directly behind the 63 thou fingered plate (SG-13) with some cracking of the paint around some of the rivets in this area. This distortion is worse on the outer edges of the aircraft around the Fus 35. but is still evident right across on a line with the bulkhead just rear of the tips of the fingers on the SG-13...
Between the end of my fingers of SG-13 and the bulkhead is about 2" or 2 rivets, the second connecting the floor with the bulkhead. Have you found stress fagigue along either one of these rivet lines, or is it in the last rivet of the fingers, or ...?

...I intend to transfer the loads further back from the SG-13 by increasing the skin thickness' in that area as well....

Do you mean transfer the loads from SG-13 back to the next bulkhead 2" away? .. or even further? If it's just to the nearest bulkhead one way for me to do it since I haven't riveted this area yet is to redo the SG-13 2" longer to tie into this bulkhead. Otherwise the thickness of SG-13 would make a doubler problematic, for me at least. How had you planned your doubler or otherwise 'increase the skin thickness' ?

But if you mean transfer the loads clear back to the next bulkhead, the double bulkheads, then maybe some more channels or stringers could be placed between the existing ones from the single bulkhead to the double one.

Also, I have already replace the Fus-35 angle with one that is roughly 2" x 2". Do you think this would be enough to avoid your problems? Or I could take the old Fus-35 and use it as a doubler on the inside of the corner wraps between the bulkheads if this is where it is needed most.

But Murphy's suggested fix to me was a doubler covering the lower doorpost area attached to the skins fore and aft of that and increase the size of the rivets into the lower doorpost.

Does this mean from the post to Fus-11 Side Panel, Fus -70 Corner Panel, and/or Fus-26 Lower Side Panel?

Let me know what you think and happy drilling!

Dan
R280

PS: Is the original message the most recent on this topic?

----- Original Message -----

[Dan Morehouse]

Thanks for the report, Alister, but.....

don't you know I only want to hear good news? ;-) Edison supposedly tried over a thousand different filaments when designing the light bulb. Hope you don't have to go that far!

Take care,
Dan

----- Original Message -----
From: Alister Yeoman (yeoman@voyager.co.nz)
To: Rebel (murphy-rebel@dcsol.com)
Sent: Sunday, March 26, 2000 12:36 AM
Subject: Brake loads/Spring gear


Hi Dan,

Yes we did receive that last message, I did not report back because I had nothing to report at the time!!

However I have since repaired my lower floor skin damage and put heavier gauge skins in that area and I have to report that it really was a waste of time. It has added weight without adding any support with the tortional loads of braking. ( we check this by clamping a piece of right angle on the top of the gear leg with it extending back about 2 feet along the fuse, we then apply the brakes and rock the aircraft backwards and forwards and measure the deflection).

The conclusion has to be that beefing up that area does nothing (or very little) to help distribute braking loads.

My concern is this. The tortional braking loads are being transferred up the door post and are being distributed to the fuse via this method, in fact placing a trapeze shaped doubler over this lower doorpost area was Murphy's idea to distribute these loads. The problem is that the wing strut attach brackets that also attach the carrythrough to the doorpost are flexing as loads pass through them. This is not good practice, over time this could cause cracks to develop in the wing strut attach bracket ( not a good idea!! )

I believe that the braking loads need to be isolated before they reach the strut attach brackets.

It may be possible to isolate these loads internally with some sort of structure, but because of the type of operations I do ( and weight, and simplicity) it is my intention to do this externally as described to this forum some weeks ago under this same subject.

I hope this gives some food for thought.

Cheers

Alister

email: yeoman@voyager.co.n (yeoman@voyager.co.n)z

[Alister Yeoman]

Hi Dan,

Yes we did receive that last message, I did not report back because I had nothing to report at the time!!

However I have since repaired my lower floor skin damage and put heavier gauge skins in that area and I have to report that it really was a waste of time. It has added weight without adding any support with the tortional loads of braking. ( we check this by clamping a piece of right angle on the top of the gear leg with it extending back about 2 feet along the fuse, we then apply the brakes and rock the aircraft backwards and forwards and measure the deflection).

The conclusion has to be that beefing up that area does nothing (or very little) to help distribute braking loads.

My concern is this. The tortional braking loads are being transferred up the door post and are being distributed to the fuse via this method, in fact placing a trapeze shaped doubler over this lower doorpost area was Murphy's idea to distribute these loads. The problem is that the wing strut attach brackets that also attach the carrythrough to the doorpost are flexing as loads pass through them. This is not good practice, over time this could cause cracks to develop in the wing strut attach bracket ( not a good idea!! )

I believe that the braking loads need to be isolated before they reach the strut attach brackets.

It may be possible to isolate these loads internally with some sort of structure, but because of the type of operations I do ( and weight, and simplicity) it is my intention to do this externally as described to this forum some weeks ago under this same subject.

I hope this gives some food for thought.

Cheers

Alister

email: yeoman@voyager.co.n (yeoman@voyager.co.n)z