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Re: Carb Heat Box
Great info on the part numbers. Thanks.
The cable end does not look to be frayed or broken. I'll take a closer look at it when I drop the cowl.
I just called Univair and Wag Aero. Like you said, nada. With the poor reviews regarding the Spruce box, I'm not going to bother. I'd rather have mine rebuilt with the McFarland piece or get one from a salvage yard.
Anybody out there have a servicable carb box for a PA-22 with the O320A2B sitting around?
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Administrator
Re: Carb Heat Box
OK, Rick at Univair looked at the drawings and figured out that the 11950-007 box is .63" from the top of the box to the flange that bolts to the carburetor and the 12746-004 box is 15/16" from these two points. There were two spacers part # 91499-000 that were used on the Tri-Pacer from serial number 22-1 to 22-2424 except serial number 22-2378. Serial number 22-2378 and 22-2425 and up used the 12746-004 air box. Therefore it appears to me that Piper eliminated the two spacers by making the air box neck longer on the 12746-004 air box. From what I remember and see in the data I have these were used on Tri-Pacers and I believe it was a clearance problem with the Tri-Pacer cowl or nose gear. Probably not needed on a Pacer conversion. Rick did bring this up to Jim Dyer (Univair owner) that this is a commonly requested part. They make the box with a different neck so it wouldn't be hard to make this one as well. Will keep you posted.
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Re: Carb Heat Box
I measured the clearance between the top of the Bracket Air Filter and the cowl above it; just a hair under 3/4". Since there is only about 1/3" difference in the air box tube lengths between 11950-007 and 12746-004 then the 11950 should fit without modifications or spacers. I suspect the extra 1/3" was for the nose wheel mount, but I don't know for sure since mine has the taildragger mod.
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Re: Carb Heat Box
We are looking for a fix for our box also. Rex pulled it out and bead blasted it and the shaft that holds the flapper is corroded on the opposite side of the linkage arm (barely hanging on). The box is in great shape except for that. It would be a shame to spend $600 for a whole box when the only problem is the shaft.
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Re: Carb Heat Box
McFarlane and some other suppliers sell a kit which consists of a shaft and new bushing mounts to rebuild the box if you only need a shaft. While the kits are advertised for Continental applications, I know one of the models works with our airbox. Basically have to remove the bushing bosses, cut the shaft an remove the diverter plate. I have seen the new bushing mounts brazed and welded on, shaft then inserted and a plate has to be welded or somehow securely attached to the shaft. All well and good but since I do not believe they carry PMA or any other approval for Lycoming aps, a field approval would be required. Using the words "fabricated new shaft and bushing" would work as an owner produced part though.
"Progress is our most important problem"
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Re: Carb Heat Box
My airbox carb heat pivot plate failed in the same way back about 9 years ago.
Below is a report I posted on the old SWPC email list back then describing the repair.
The repair is still working well with another 500 hours or so on the tack.
Brian
My air box had the hollow tube that the carb heat flap pivots on
fatigue and severd resulting in the need for repair. I went by Aircraft Spruce in
Corona to get a hands on look at their repair kits and the PA-22 airbox they
market. I wound up purchasing the repair kit they show in their catalog as the
C-85, C-90, O-200 repair kit PN 07-00110. This kit has a solid steel shaft and
comes with a 1/4 28 stop nut to secure it as opposed to the brazed on end cap of
the original unit. The length of the shaft is a perfect width for the 22 airbox.
The two flanges are well bushed with brass bushings and are very similar to the
original unit in look and diameter. I let the old box soak in mineral spirits
for a few minutes to loosen up the Brackett filter goo and then worked it over
in the blast box for a while to get it down to shinny metal. The box was then
turned over to my IA who put it in the que on his to do shelf. The kit install
involved unbrazing the heat flap from the old hollow tube shaft and sliding the
tube out which lets the flap drop out of the box. The original flap has two spot
welded saddles the shaft slides through, which were left intact and reused. The
new shaft was drilled and tapped for 6/32 screws in tree places between the
saddles along with three holes in the flap for the screws to pass through. The
existing flanges were removed with a air grinder disk down to a level to
accommodate the new flanges. The kit flanges come with three 1/8 " holes in a
triangular pattern. Corresponding holes were drilled in the sides of the airbox
and the flanges were riveted with 1/8" AN rivets. The flap was then placed in
the box; the shaft was slipped through the saddles; and then working through the
outlet to the carb the 6/32 screws were placed to secure the flap to the shaft.
In addition, miniature 6/32 all metal stop nuts were threaded onto the exposed
ends of the three screws to prevent the screws from backing out. The friction
lever on the kit is a vee shaped type notch as opposed to the round dimple on
the original. New grooves were filed into the built up brazed material to
accommodate this vee shaped lever. The repaired box was then primed, panted and
returned to service. A simple log book entry was made by the IA to document the
repair.
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Re: Carb Heat Box
Cathy liked your packaging. It just arrived.
Yeah, after 17+ years those things accumulate. They're great for working on cars and airplanes. Not so good for welding.
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Administrator
Re: Carb Heat Box
Box is fixed thanks to a donor shaft and arm from a box that got crushed. A friend of mine is going to braze the shaft back to the flapper tomorrow. He is a master at brazing. I wanted to stick with the original design, nothing to come off the flapper and go in the intake etc. I think it would be a good idea to clean out the shaft and apply some anti-corrosion something to it and seal the open end so moisture can't get in. I wouldn't go through all this if the bushings were worn out but would go the route of Andy and Brian.
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