Welcome! Becoming a registered user of ShortWingPipers.Org is free and easy! Click the "Register" link found in the upper right hand corner of this screen. It's easy and you can then join the fun posting and learning about Short Wing Pipers!
I am trying to fit a new univair tailspring bracket (rear one) to the tailpost and lower L tubes.
I see in the piper drawings CD--- there used to be 2 different part numbers that were cut a little different.
One had a -00 suffix and other had a 002 suffix (if I remember right) The New Univair part says that their
current part number replaces both of them. ----- OK ..
The bracket has a rear slot then the end of the post weld into. The slot i3 3/4 inches tall. When that slot bottoms out on the end of the post--- I still have about 1/4 inch to go before the scalloped (other side) touches
the longeron tubes (where you weld them in)
Either the end of my tailpost is a bit too long--- (maybe-) or the slot in the bracket needs to be cut a little deeper so the bracket can go a little further onto the post and the gap between the longerons and the bracket will close up.
I suspect my post is a bit long yet- ( since I double sleeved it) there may be some remnants of the
old bracket and its welds lingering there --- im thinking maybe 1/8 ?
How proud should the post be past the surface of the longeron tubes ?
It LOOKS like I have about a good 1/4 inch to go ----that the bracket has to go on the post more in order
to close the gap with the longeron tubes..... for those of you who have done that lately--- did you have
to deepen the rectangular slot in the new univair bracket some ? (the two shown on the CD show two
different slot depths --- but it doesn't say which one to use where....) Did you just cut the slot deeper until the canoe shaped cut on the bracket touched the longeron tubes ?
I was looking at steve's picks where he had good pictures and I am trying to duplicate what he did with his
longeron tubes where they terminate into the bracket--- that looked nice and clean !
I found some 17mm liner tubes for the longerons that just made the perfect interference fit ! I have them
running from the bracket at the rear- to the first crosstubes - so they should be good and strong.
Have the tail post sleeved from the bracket up to within 1/4 inch of the vert. fin post. (al lI could get-)
The old longeron tubes had two splices in that last bay between the spring bracket and the last bay--
so I was able to eliminate the old splice that was just forward of the front spring bracket. cant see in th epic but I have a tubular sleeve ready to fit inside the forward bracket to resist any crush from the spring bolt.
A little more fine fitting to make sure longerons are level (and bracket parallel with the deck) and get this
gap closed up--- and I will be ready to start welding. ( I hope)
The bottom of the bracket isnt supposed to be parallel with the longeron. The two different part numbers provide a different angle on the spring perch, one for the narrow gear, and one for the wide gear. Look on the fuselage fitting drawing to see what the angle is supposed to be for the type gear you have.
It is true that the angles are different based on the wide or narrow gear. On the master drawing for the 20611 assemblies the differing angles are in a reference table box marked "C". On part 20611 no suffix "C" is 73 degrees and on part 20611-2 (suffixes -002, -0002) "C" is 83 degrees.
The real difference is the geometry between the leg of the bracket with the angle and the aft facing vertical leg of the bracket with the cutout notch. The notch on the 20611 is referenced with item "B" which is 1 1/8". On the 20611-2 "B" it is 3/4" just like you described in your post. Obviously when the angle is closer to 90 degrees from the tailpost, like the 20611-2 at 83 degrees, that you must have, it will be flatter or I should say at a right angle to the tail post. This is why you have a 1/4" gap, when the geometry changed for the wide gear it moved it away from the bottom longerons.
The new Univair part number L1027-02 is for the PA-18, which also used the earlier 20611 with the longer cutout of "B" 1 1/8". I used the Univair L1027-02 when I converted from the narrow gear to the wide gear on a PA 20. I did not experience the problems you stated when it was installed. I cannot confirm that it was indeed cut out to 1 1/8" in the slot. Perhaps you could contact Univair and confirm the dimensions. That would prove that the L-1027-02 has a 1 1/8" cut out with a 83 degree angle from the back or aft vertical leg of the bracket.
Todd
Last edited by Vagabondblues; 03-24-2020 at 02:21 PM.
about 3 owners ago-- converted it from 22 to 20 using the "old" kit supplied by LPC (pre-univair).
Whoever did it apparently neglected to notice that mud/snow laying on the lower flying wire bracket had
rusted outside-in holes in the lower longeron tubes. (small ones- through on one side and all most through on the other)
I had to cut the existing bracket off to prep the tail post (remove the old longeron attach welds) and also grind off
the remnants of the bracket's welds. So some of the "end" of the tailpost is the end of the bracket. I THINK I have
ground about an 1/8 off - but it could still be a bit long. The end of the post is what "stops" the bracket in that rectangular
slot. So if the post is long yet-- the bracket does not go on the post deep enough to make contact with the longerons where
they weld in.
I did not know to measure the old bracket before I cut it off--- but it sure looks the same as the new one.
I believe the main gear would have to be the wide gear- (though there is no serial numbers on the gear legs)
I guess I could put the spring back on and see if the rear face of the bracket is parallel with the post (where that square slot is-) I think that should be parallel to the post on both versions of the bracket since the bracket get a weld bead onto the
rear facing surface of the post there. (unless you had a mis-match between spring angles and brackets....)
I would THINK that any one that's replaces that bracket doing the liner tube job would have had to use that bracket if
that is the only one univair makes now. (short of heat and re-bend.... )
I will try a trial fit of the spring and see what that looks like...…
Will look again at the drawings cited too ----(continue to study)
Vagabond--- If I have the the incorrect bracket somehow-- the one which is closer to 90 degrees--- THAT would bring the
front contact point (where it touches the longerons) down and away from the longerons.... so maybe I need a pa-18 bracket and NOT a pa-20 bracket---- easy enough to measure the angle on the bracket--- and I will look at my recipt from univair
--- I THINK when they say that the current bracket takes the place of both old part numbers-- I think that means both pa-20 brackets. have to stare at it some more --- cant get THAT messed up now......
I put the spring/wheel on hand tights and looked it over. The bracket has an 83 degree angle on its bend line.(FYI)
(its a Univair L1027-02) Sitting on the post- the bracket's rear face is 1 or 2 degrees different than the post's angle.
(this looks like it will correct if the bracket goes on to the post another 1/4 inch)
The front of the bracket has a 1/4 inch gap holding it off the longerons. appears that this the same 1/4 in that needs to be removed from the rectangular slot in the bracket. The fit at the front attach bolt looks like it needs to be another 1 or 2 degrees in order to sit exactly square on the perch. (the same 1 or 2 degrees mismatch between the tail post and rear face
of bracket.) So- it appears that if I cut the rectangular slot about 3/16 to 1/4 inch deeper--- everything fits---
Another data point ---- the piper blueprint (picture) CD shows a measurement from the lowest point on the bracket
(at the bend line) to the center of the longeron tube--- of 1.032. When I measure that distance --- I am about 1/4 inch
too long...….
Here are some more pics-- (just for fun--- everyone screams if there are no pics right ?)
about 3 owners ago-- converted it from 22 to 20 using the "old" kit supplied by LPC.Tim
This may be redundant but the old LPC modification drawings are on the SWPC CD. The are on the second to last page of the numeric index.
The drawing shows the L1027-2 as the correct bracket. It is unclear from the drawing how far the tail post goes into the bracket. What is different is that LPC shows the angle to be measured from another confusing reference point of 97 degrees. It also clearly shows the top of the vertical leg of the bracket does not go past the lower rudder bushing mount, which would lead you to believe that it has the 3/4" cut.
I put the spring/wheel on hand tights and looked it over. The bracket has an 83 degree angle on its bend line.(FYI)
(its a Univair L1027-02) Sitting on the post- the bracket's rear face is 1 or 2 degrees different than the post's angle.
(this looks like it will correct if the bracket goes on to the post another 1/4 inch)
The front of the bracket has a 1/4 inch gap holding it off the longerons. appears that this the same 1/4 in that needs to be removed from the rectangular slot in the bracket. The fit at the front attach bolt looks like it needs to be another 1 or 2 degrees in order to sit exactly square on the perch. (the same 1 or 2 degrees mismatch between the tail post and rear face
of bracket.) So- it appears that if I cut the rectangular slot about 3/16 to 1/4 inch deeper--- everything fits---
Another data point ---- the piper blueprint (picture) CD shows a measurement from the lowest point on the bracket
(at the bend line) to the center of the longeron tube--- of 1.032. When I measure that distance --- I am about 1/4 inch
too long...….
Here are some more pics-- (just for fun--- everyone screams if there are no pics right ?)
Looking at your pictures and the drawing I posted, you do know that the slot in the bracket is installed so it goes around the lower rudder bushing mount? The way its installed in the pics is sitting on top of the tube.
when I look at the drawing in your last post--- their drawing is not really even self consistent between the views.
Note the upper left drawing - they left out the line representing the end of the post. (in the other drawings it appears to be about even with the tops of the longerons) also the upper left view shows the tip of the bracket just below the lower edge of the bushing base. The upper ight one show it just above the edge of the bushing base.
I just ground/cut off about 1/4 inch from the inside of the slot so it goes on to the post another 1/4 inch deeper. That seemed to have now made nicer contact with the longerons--- and both the angles of the front and rear perch look pretty good. I wasn't too worried about the slot-vs.-lower bushing -- yet----
It LOOKS like the geometry is in the ballpark----
not quite clear by what "around" means ---- it looks like the rear of the bracket should be about flush with the rear surface of the post---- and you weld around the 3 sides of the slot onto the post. Looks like if it went any further down on the post-- the angles on the perches would be off----
have a look at it now I made the slot 1/4 inch deeper and the bracket went down some----- here goes---
Here are 2 of the main ones I was using as a visual guide --- I THINK I read that this was one Steve repaired--
( I could be mistaken on that though--- but it looks like a nice neat job whoever did it-----)
Trying to generally match that roughly speaking----bad tail post 3.jpgtail post repair.jpg
Thanks: 
Likes: 
rear tailwheel spring bracket Q
Reply With Quote
)
Originally Posted by violinmaker
