Panther Builders Manual

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Drilling Tail Wheel Spring

Note: SPA offers the tail wheel springs predrilled as an option for those not wanting to drill the stainless spring themselves. Contact SPA for details.

We recommend drilling the tail wheel spring before permanently installing the P-T-TC-tail wheel socket into the tail cone. We recommend the API stainless steel spring and tail wheel. The spring is shipped over length, so you will need to trim it to the proper length. The tail wheel is available in several sizes and styles. We use the 20° socket, single fork, and either a 4, or 6 inch wheel. If you are using a light engine like Corvair, UL 350, Jabiru 3300, etc. we recommend the 4 inch wheel to help keep CG within range. With larger engines the 6 inch wheel is an option, but in our experience, flying almost exclusively from grass strips, it is not needed.

Drilling tail wheel spring before P-T-TC-tail wheel socket is mounted

1.The tail wheel spring will need to be trimmed before installing it the P-T-TC-tail wheel socket. Make sure to trim the larger end. Trim to 20 1/8 in (511.2 mm) total length. See photo

drillingtailspring

2.Drill a ¼ inch hole in the front plate P-T-TC-tail wheel socket per photo

drillingtailspring2

3.The tail wheel spring needs a snug fit in the socket to prevent long term wear, which would allow the spring to flex in the mount. Without a snug fit it can lead to possible bolt breakage. SPA reams the sockets to ¾ in during manufacturing. For a snug fit to the exact spring you may need to polish the inside of the socket. We make a “flapper hone” out of a scrap piece of rod (steel, aluminum, or even a wooden dowel) and course sand paper. See photo.

drillingtailspring3

drillingtailspring4

4.SPA predrilled assemblies We coat the end of the spring with anti-seize or LPS3 preservative and press the spring fully into the socket with a hydraulic press (see photo). You can use a hammer etc. to install if needed. Use care not to bend or damage the P-T-TC-tail wheel socket.

5.Mark the P-T-TC-tail wheel socket for the bolt hole per drawing below

drillingtailspring5

6.Clamp in a drill press making sure the hole will be on center and square to spring, drill press and drill.

7.Use a short length cobalt drill (.180 dia) first and then ream to .1855-.1875 for a tight fit of the AN3-13A bolt. Do not “step drill” using a small bit first. When drilling use good cutting oil (not WD-40) and 350 RPM or less (less is better)! Use a heavy pressure, and do not allow the drill to “slip” against cutting surface, or you will quickly dull the bit. The bit must be cutting (making chips) the entire time or you will dull the bit and work harden the stainless, making it very difficult to drill through.

Note: The tail wheel spring bolts must fit in a “tight hole” or they will be subject to movement and wear over time.

drillingtailspring6

8.Install AN3-13A bolt, MS21044N3 nut and AN960-10washers needed, with the bolt head up.

9.Cleco the tail wheel socket with spring into the Tail cone

10. Slide tail wheel mount onto the spring. Verify the tail wheel mount is fully onto the spring and aligned with bulkhead 5. You want the tail wheel mount to be parallel to the vertical centerline of the fuse. Mark the tail wheel mount to the spring.

11. Remove tail wheel spring socket/spring/tail wheel mount assembly and clamp in drill press vise with the hole in tail wheel mount aligned with drill bit

12. Drill the tail wheel spring, and ream for the AN3C-15A bolt as above.

drillingtailspring7

13. Install the AN3C-15A bolt with the head up. Install MS21044N3 nut and AN960C10 Washer as needed

Drilling tail wheel spring before P-T-TC-tail wheel socket is mounted

If you have already permanently mounted the P-T-TC-tail wheel socket into the tail cone you will need to use a slightly different process.

1.Mark the tail wheel socket per above and drill bottom side of tube only to .180

2.Cut tail wheel spring per above.

3.Mark tail wheel spring slightly less than 7/8 from the front end and drill .180 on center in a drill press.

4.You will need to use a “flapper hone” (see above) to carefully open the ID of the tail wheel socket tube. The goal is to have it a snug fit but be able to be removed so you can drill the tail wheel mount itself in a drill press. The aft “bushing “in the P-T-TC-tail wheel socket can have a little “play” in it, but use care not make a loose fit in the front bushing. If needed you can insert a rod into the ¼ inch hole drilled earlier from the front side and tap the spring out of the socket. It is a balance between a snug fit and being able to remove the spring.

5.With the spring fitted in and the hole in the bottom of the mount socket aligned with the hole in spring, drill through the top wall of the tube. Ream to .1855-.1875 for a snug fit of the AN3-13A bolt.

6.Install the AN3-13A bolt, MS21044N3 nut and AN960-10 washer s needed, with the bolt head up

7.Slide the tail wheel mount onto the spring, and align vertically with bulk head 5.

8.Mark the orientation, remove spring from the fuselage socket, and drill in drill press .180.

9.Ream for a tight fit of the AN3C-15A bolt.

10.Install the AN3C-15A bolt, MS21044N3 nut and AN960C10 Washer as needed, with the bolt head up.