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  #21  
Old 10-07-2006, 05:49 AM
mlw450802's Avatar
mlw450802 mlw450802 is offline
 
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Location: Payson, AZ
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Quote:
Originally Posted by Jonathan Cude
In your messages and your classified add you draw attention to your desires:
1. Safety --> your part increases safety margins... Great!
2. Experienced Machinist since 1982 --> as stated in your classified add, I am humbly going to have to question your skills as you claim 2 hours per pair.
Jonathan,
I am going to have to come to Alan's defense here (by-the-way, there is nothing to be gained by ad hominem attacks and we all would benefit if we could remember that).
I respectfully suggest that you prepare a set of drawings with appropriate material callouts and submit them to any machine shop in the business of making money. You would be extremely lucky to find a shop willing to charge less than one shop hour for anything, which, in my part of the country, would cost a minimum of $60.
$45, while not cheap, is not exhorbitant either. If the machine tools are already paid for and you treat that resource as free (it is not), you are not considering the true economics of this situation and it may seem a little pricey. But if you have a $100,000 machine you're trying to make the mortgage on, the order needs to be many hundreds if not thousands of parts to get the individual costs down.

-mike
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  #22  
Old 10-07-2006, 08:07 AM
jbDC9 jbDC9 is offline
 
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I don't get it... what's with all the hubbub over $45 for a pair of 4130 push rods? All you gotta do is call Vans and get a pair of VA-256 flap push rods, $12 each, $24 for the pair. I bought two but haven't flown 'em yet; they're pretty heavy duty and drilled/tapped by Vans, so I don't have to worry about screwing anything up.

Easy.
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  #23  
Old 10-07-2006, 08:08 AM
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cytoxin cytoxin is offline
 
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Location: south carolina
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Default scare tactics even though unintentional

they used to do this at sears,,,scare the cutomer to death then offer up a solution that will make it all better. just offer the parts for sale on the basis of their strengths. i charge 70 bucks an hour for a trans overhaul i know the time is worth it. so 3 rods out of 9000(4500) failed wow thats like .001% most would argue those are acceptable margins

note: the math is wrong as pointed out by gil should be .033 another .967 and we'll have a whole 1%
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Last edited by cytoxin : 10-09-2006 at 11:56 AM.
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  #24  
Old 10-07-2006, 09:38 AM
casper casper is offline
 
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To clarify the post by alan judy about the airplane he saw in dodge city that the flap push rod failed on was the second time that airplane was wrecked. I believe the push rod was damaged in the first wreck and failed because of prior damage.
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  #25  
Old 10-07-2006, 09:54 AM
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Pmerems Pmerems is offline
 
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Location: Tucson, AZ
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Default 4130 rod pricing

The man can set his own price if he desires. If it is too much then he will not sell many.

If the need is real, and 4130 is the answer, then I would contract out 50 or more pairs of rods with a local machine shop and the price per pair would drop significantly. Then this saving could be passed on to customer with lower prices. If I were only machining a pair every now and then it would be rather expensive and most likely would sell many.


Food for thought.

Paul
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  #26  
Old 10-07-2006, 11:42 AM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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The big news here -- for me -- is I just learned I'm building a $100,000 airplane.
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  #27  
Old 10-07-2006, 01:53 PM
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rv8ch rv8ch is offline
 
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Location: LSGY
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Default flap push rod

Quote:
Originally Posted by Jonathan Cude
How about a standard safety factor of 1.5... now the critical load is reduced from 888 lbs to 592 lbs.

For the rod to fail within the 1.5 safety margin (ie exceed 592 lbs), the flap must transfer more than 592 lbs to the pushrod. A hinge moment equation exists to calculate this, but is beyond my thoughts at the moment (no pun intended.) ...
Interesting topic. Assuming your calculations to get to 592 lbs are correct, and they look ok to me, would it be possible to get anywhere near that much force on the flap pushrods? Think about it for a minute...imagine you flipped your wing upside down, and stood on the flaps while they were down (up). Do you think they would survive being stood on by a 200 pound builder? I wonder if the flaps themselves would bend before the pushrod buckles.
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  #28  
Old 10-07-2006, 02:07 PM
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Default Vans hex flap pushrods

Vans hex flap pushrods. Can anyone provide a part number? I did a search in the online catalog and didn't come up with anything.
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  #29  
Old 10-07-2006, 02:25 PM
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IowaRV9Dreamer IowaRV9Dreamer is offline
 
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Location: Marion IA
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Default hex pushrod part number is VA-256

On my drawing 33, view C-C. The drawing is for both RV-7 and RV-9. and the rod part # seems to be the only difference:
RV-7: F-759A (round)
RV-9: VA-256 (hex)

I wonder why they are different?
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  #30  
Old 10-07-2006, 02:33 PM
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Mel Mel is online now
 
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The flaps on the -7 are "plane" flaps. On the -9, they are "slotted" flaps, so the pushrods are different.
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