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  #1  
Old 04-28-2022, 04:41 PM
Pilot135pd's Avatar
Pilot135pd Pilot135pd is offline
 
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Location: Vaca Moo Airport - TA37 in East TEXAS
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Default 4130 and other metals

So I'm rebuilding my carb heat box flap (closes off filtered air and allows exhaust heated air to the carb) and apparently it hadn't been maintained or inspected since 1968.

As you can see in the pictures I need to fabricate a new shaft to hold that flap. I bought new bearings and now need to buy the metal rod. Everything I find online shows 4130 and locally they didn't even tell me the metal number, they just told me that it's hard enough and will do fine.

Since all this does is when it's cold before you land you pull the cable and the flap opens, then when you land you close it, why would that shaft material have to be so strong?
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Sadly sold my RV-8 however still trying to enjoy life by living on my airport with FREE campsites & facilities for ALL visiting pilots to enjoy www.facebook.com/VacaMooAirport/ & flying my OnSpeed equipped C-177 while waiting for my next experimental plane !

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  #2  
Old 04-28-2022, 05:15 PM
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Default Metal rods

My local hardware store and Home Depot have racks of metals
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  #3  
Old 04-28-2022, 05:50 PM
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Pilot135pd Pilot135pd is offline
 
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Default

Yes I went there but they didn't have the correct diameter. A local steel company has it, just $6 for a 20' long stick so I guess when it wears out again I'll have plenty to fabricate another one

I'm just wanting input regarding the strength. Does it have to be a stronger metal or is the worst that can happen that I have to fabricate another one in a few years because this one wears in the same place with the bearings like the current shaft did?
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Sadly sold my RV-8 however still trying to enjoy life by living on my airport with FREE campsites & facilities for ALL visiting pilots to enjoy www.facebook.com/VacaMooAirport/ & flying my OnSpeed equipped C-177 while waiting for my next experimental plane !

Exempt by 3 out of the 10 ways but I still donated.
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  #4  
Old 04-28-2022, 06:12 PM
terrye terrye is offline
 
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Default 4130 and other metals

And this is for your Cessna C-177 Cardinal? You are making new parts without even doing a metallurgical or hardness test on the old part? Why wouldn't you buy the actual part from Cessna?
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  #5  
Old 04-28-2022, 06:25 PM
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Pilot135pd Pilot135pd is offline
 
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Because I like to learn. If it were a landing gear I'd buy an original part but when a 1968 part costs over $2,500 you can bet I'm going to research a owner produced part as per the FAA Regulations.

By asking experienced builders here I can learn about these things. When my IA comes this weekend I can show what I have and if she's ok with it then it's a go. If not then we move on to step 2.
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Sadly sold my RV-8 however still trying to enjoy life by living on my airport with FREE campsites & facilities for ALL visiting pilots to enjoy www.facebook.com/VacaMooAirport/ & flying my OnSpeed equipped C-177 while waiting for my next experimental plane !

Exempt by 3 out of the 10 ways but I still donated.
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  #6  
Old 04-28-2022, 06:48 PM
BillL BillL is offline
 
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Default Why use unspecified material??

I usually get 4130 from Spruce by the foot. 5/16" is . . . . well you can figure that. And . . make a machined bushing to match if 0.005" of diameter is critical. Personally, I would not hesitate to use 4130 since it will depend on the weld of the pivot arm to the end. Get some 4130 flat stock for that too.

5/16" rod is $2.64 at Spruce. First class mail and it is at your door.

There are some 4130 pivot pins on my Kubota now. It is cold rolled, stronger, and harder - -precision diameter- just do it.

It will be better than a big nail.
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  #7  
Old 04-28-2022, 06:49 PM
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DanH DanH is online now
 
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Quote:
Originally Posted by Pilot135pd View Post
YI'm just wanting input regarding the strength. Does it have to be a stronger metal or is the worst that can happen that I have to fabricate another one in a few years because this one wears in the same place with the bearings like the current shaft did?
Given hardness to resist wear was the real interest, readily available 4130 was the better choice. It's an air-hardening steel. Heat it, quench it, and you get high hardness.
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  #8  
Old 04-28-2022, 07:07 PM
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Pilot135pd Pilot135pd is offline
 
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That's the info I'm looking for. I'll call the local company to see exactly what they have, they have to know what kind of metal they're selling, it's a big multi state company. If not then Aircraft Spruce it is. Thanks.
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Sadly sold my RV-8 however still trying to enjoy life by living on my airport with FREE campsites & facilities for ALL visiting pilots to enjoy www.facebook.com/VacaMooAirport/ & flying my OnSpeed equipped C-177 while waiting for my next experimental plane !

Exempt by 3 out of the 10 ways but I still donated.
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  #9  
Old 04-28-2022, 07:08 PM
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n82rb n82rb is offline
 
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Default

Quote:
Originally Posted by Pilot135pd View Post
Because I like to learn. If it were a landing gear I'd buy an original part but when a 1968 part costs over $2,500 you can bet I'm going to research a owner produced part as per the FAA Regulations.

By asking experienced builders here I can learn about these things. When my IA comes this weekend I can show what I have and if she's ok with it then it's a go. If not then we move on to step 2.
here is what your IA should know. one part of an owner manufactured part for a certified aircraft, is that it must conform to the original approved design data. what does that mean? it must be made the same as the original part, same dimensions, same material. so, do you have the manufacturers drawing of the part calling out the dimensions and materials? if not, then you must duplicate that part, dimensions are not hard to do, a certified caliper and set of mics will get that done. the materials are another story, without the manufactures drawing, the only really legal way to do it is to pay a lab to analyze the material and determine what alloy it is.

bob burns
RV-4 N82RB
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  #10  
Old 04-28-2022, 07:11 PM
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Pilot135pd Pilot135pd is offline
 
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Quote:
Originally Posted by n82rb View Post
.... determine what alloy it is.

bob burns
RV-4 N82RB
I'll call Cessna tomorrow. Thanks.
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Sadly sold my RV-8 however still trying to enjoy life by living on my airport with FREE campsites & facilities for ALL visiting pilots to enjoy www.facebook.com/VacaMooAirport/ & flying my OnSpeed equipped C-177 while waiting for my next experimental plane !

Exempt by 3 out of the 10 ways but I still donated.
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