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wnorth(at)sdccd.edu
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 Posted: Mon Jan 21, 2008 9:35 am Post subject: On fuel pumps and rivets |
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Blast the fuel pump with a really brief shot of shop air, or turn on boost
pump and spin engine to see if diaphragm action will open the check valves.
On rivets, while the number of times something is whacked does very slightly
alter the amount of cold working that occurs(as in less than 1%), the
primary factor that causes cold working is the amount of distortion, not the
number of blows. (This obviously varies greatly for differing materials, but
2117 aluminum used in 426/470 standard rivets will be equally strong if
crushed in 2, 3, 4, or 5 blows)
It does not matter which end you crush the rivet from. When a gun is
correctly used the first blow starts a cycle where the next blow and the
buck come back together in sequence, but it is the shop end shank that is
being formed, not the manufacturer's end. (hopefully) The reason we call
them bucking bars is that they are supposed to buck.
If the shop end is formed correctly as per AC43.13 it matters not how one
got there.
For -3's I use a pressure and bucking bar that gets me there in 3-4 blows,
(as in ba-da-bop) if possible, some bars need to be lighter to get into
those tiny places so the pressure gets backed off and it takes more blows.
For -4s I aim for 4-5 blows although they can be done in 3, but at that
pressure it is easier to lose it and over shoot causing the base metal to
distort.
There are many applications in really stiff frames where back riveting is
the only way to get there because the gun won't move the base assembly
enough to get proper bucking bar action.
For those of you new to this you should play with holding the bucking bar
too tight or stiffly, and then really loosely in thinner practice material
to see what that does to both the rivet and the base material. You'll be
amazed at how different the two look. It does take time to get a feel for
this... The problem with a longer sequence of blows is that I tend to hold
the bar too tight for that pressure getting high rivets and base metal
puckers.
I would also add, that for those of you who use squeezers, you are back
riveting every time you squeeze.
Happy MLK/Northridge Quake Day
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Mark Phillips in TN
Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN
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| Posted: Mon Jan 21, 2008 8:16 pm Post subject: On fuel pumps and rivets |
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In a message dated 01/21/2008 11:37:21 AM Central Standard Time, wnorth(at)sdccd.edu writes:
| Quote: | Blast the fuel pump with a really brief shot of shop air, or turn on boost
pump and spin engine to see if diaphragm action will open the check valves. |
Kinda watching the notes of fuel pump and was curious if it wasn't "possible" that you might have the "IN" connected to the "OUT" and vice-versa? These pumps can be configured either way- on the advice of a particularly astute builder of whom I enjoy the benefit of being in my circle of intelligentsia (thanks Charlie Bravo!) I ordered a pump with the in-out as out-in which allowed a routing to the carb with an improved distance from the exhaust pipes. See:
http://websites.expercraft.com/n51pw/index.php?q=log_entry&log_id=5457
From The PossumWorks in TN
Mark
Start the year off right. Easy ways to stay in shape in the new year.
[quote][b]
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From The PossumWorks... |
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