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To: <
murphy-rebel@dcsol.com> (Murphy Rebel Builders List)
From: Bob Patterson <
bob.patterson@canrem.com>
Subject: Re: New Aluminum tail spring
Message-Id: <
E10yodK-00028J-00@mail4.toronto.istar.net>
Date: Mon, 28 Jun 1999 23:32:30 -0400
Happy to help, anytime !! I'm only a 'builder helper' out here, though, and
I'm NOT always right - just another opinion to add to those you've already
collected ..... hope it helps !! The factory is always the final authority.
Many years ago, the tail springs on our Piper J-4A used to break off
regularly - I'd just take out the pieces, clamp the bolts tight on a spacer,
hold the brakes to raise the tail, and take off to fly down to our mechanic
to get it fixed !! Hold the brakes on landing, to keep the tail up, then let
it down gently.... We eventually went to an automobile spring shop and
had a half-dozen sets made up, slightly heavier material - no more problems
!
(Not quite 'certified' material, but it worked !) Certainly stirred things
up when I made a low pass before leaving, waving the tailwheel, to let the
guys who just arrived know where & why I was going - they couldn't figure
out how I climbed out & removed the tailwheel in flight !!! :-)
The spacer would be the same width, just thinner - you <could> just grind
down the present one, to leave room for a bit of inner tube, clamped
tightly...
The thicker spacer might have been needed because of the bent-in curve of
some springs - to clamp them without exerting a bending load just from the
way they were fastened.... Most of this stuff is just common sense & good
judgement - if it looks reasonable, and is secure, with no built-in stesses,
it's probably OK. If you're tightening up the bolts & bending the spring
just to get them tight, that's NOT "a good thing"(tm).... :-)
Sounds like you've done everything right, up front ! If needed, some of
the builders have moved the battery to the back of the firewall, on the
passenger side, above the pedals. This involves a special hinge on the
back of the box, but does move the battery back a fair bit. We have one
builder here with the Sky-tec starter, who used the small, square (about 4")
motorcycle battery, on the front of the firewall. It cranks over fast enough
to taxi !!! You don't need a LOT of battery with those geared starters !
These batteries are small, LIGHT, and cheap - we've used them in our Rebel
for 8 years - they usually last 2 or 3 years (the Canadian winters kill 'em
!).
I suspect that your C of G will come out very close to being OK -
Good Luck !!
.....bobp
--------------------------------orig.---------------------------------------
-
At 07:13 PM 6/28/99 -0700, you wrote:
Thanks Bob. It really helps to have "field" information. I sent a message
to MAM on
this issue, too, but haven't got a reply yet.
Using a thinner spacer would be the best solution, if it can handle the
load. I
don't understand why they added the additional spacer, TS-7, though, if not
for
added strength. I can see why the rubber would be a good idea for
cushioning the
impacts, but it would again lower the tail strut attach bracket which then
gives me
that undesirable negative dihedral.
I am using a lightweight Skytech starter and a Sprint alternator, along
with the
Warp Drive prop. Also, my firewall is cut back 3 inches. So I have taken
whatever
steps I know to reduce forward weight. However, I still have my battery
mounted on
the firewall, and I realize I may be dreaming, if I think that can remain.
I just
got my newly upholstered seats back, so am almost ready for that big C of G
test.
Thanks again for your help.
Bob Patterson wrote:
I had almost forgotten the earlier aluminum springs - we used one for
a
season. It went flat after repeated bumps .... (aluminum is not a great
material for 'springs' :-) )
If you can use a thinner spacer, that would be great. As I mentioned,
some have added a thin piece of rubber between the spacer and the spring.
The spacer is only to get a good angle for the spring, and to distribute
the loads from the spring to the tail post over a larger area, so making
it thinner shouldn't hurt.
If you do go to the Scott tailwheel, you will likely find that it
doesn't fit the spring. You can grind the spring a bit, and there are
spacer blocks available to help with the fit. Have a look through the
archives of this list - I think someone described these a few months ago.
I think Scott make different size attachment fittings.
You can move your battery back to adjust the C of G - several here
have used a long, narrow battery (about 3 1/2" thick, by about 10 - 11"
long). These can be positioned on the right side of the fuselage, between
the bulkheads, leaving the floor open for sleeping. Just move it back
until
you get the desired position....
The Murphy kick-out tailwheel works GREAT, once it is broken in. Be
sure to grease it regularly, especially the pin at the top. There should
be a grease fitting there for it, but it's not in the design, so you just
have to stuff a glob of grease into the underside with your finger, at
least once a month....
If you haven't already, you can save a LOT of weight up front by
going
to the B & C lightweight starter, and a lightweight alternator, (over 30
lbs),
as well as the (now-almost-standard) 3 blade Warp Drive 72 inch prop with
17" of metal on the leading edge, and SQUARE tips !
Sounds like you're making good progress - keep at it. It's worth it
!!
.....bobp
-----------------------------------orig.---------------------------------
-
At 09:04 PM 6/27/99 -0700, you wrote:
Bob, my Rebel had an aluminum tail spring which was even before the
composite
one. My serial # is 107R. With the newer replacement tail spring, an
additional
spacer TS-7 was added on top of the extra thickness of the new tail
spring,
which is what lowered the strut attach bracket. I am not sure what
purpose it
served, so I removed it, leaving only the original TS-2 spacer in place.
That
gained back some altitude on the strut bracket, and now I have only 1/4
inch
negative dihedral. Do you think this is still a problem? I could replace
the
TS-2 with another spacer that is 1/8 inch less thick, and that would
bring me
back to the original stab height. I am using the Murphy tail wheel
modified to
kick out on a sharp turn. I hope it works. I am almost ready to do a
weight and
balance, so might still go for the heavier Scott tail wheel if I have a
problem.
I am using an O320.
Bob Patterson wrote:
are
use
it
outside
strips,
spring,
to fit
stability,
way.
spacer -
you
:-( ).
fit
cheaper,
the
-----------------------------orig.-----------------------------------------
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The Murphy Rebel Builders List is for the discussion
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Archives located at:
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*----------------------------------------------------*
*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*
*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*
