Steerable Tailwheel for your Mighty Mini

by circle&stripe | December 31, 2015 | (17) Posted in How To

 

 

 This article demonstrates how to create a simple Steerable Tailwheel landing gear for your FT Mighty Mini scratch build. Following the FT philosophy of "keep it simple" this can be made from parts you already have. Unlike most main gear installations all your bends can be inexact and it will still work fine. I know that a skid would work fine but this adds about 1.3 grams and makes your plane fun to taxi.


 

1) Gather the following materials

  • 15 cm of 0.81 mm piano wire (.032")
  • 1 each used Prop (a soft black Gemfan 5x3 works great)
  • 1 each Prop Adaptors
  • 1 or more used Ink Pens or used mechanical pencil 

 

 

2) Remove the ink cartridge from the used pen.

 

 

3) Cut the clean portion of the tube off the ink cartridge and dispose of the remaining cartridge. 

 Approximately 40 cm of clean tube will be necessary so if you're using new pens it might take a couple. You don't need to cut the tube into parts yet, but eventually 4 separate pieces are required : 1 each 5 mm collar, 2 each 15 mm guides, and 1 each 8 mm axle bushing



4) Create the tire portion of the wheel 

Break the remaining blades off the used prop hub and carefully cut the rough edges off. Finish with 200 grit sand paper until smooth . Note the soft Gemfan prop works great for this, but I would not even attempt to use a DAL prop. This sounds like a lot of work but the Gemfan props are really soft and takes only a few minutes

 

5) Determine the correct prop adaptor insert to use.

Select the adaptor that fits your clean tube best

 

6) Paint your parts.

I used a silver Sharpie for the hub and  black Sharpie for the tire portions. If you have a black prop to start with it will look a lot better


7) Bend a square with the wire  to form the axle

You want it small but also large enough to allow the wheel assebly to roll freely. I have found that I can keep my bends small with sharp angles by forming it without the wheel installed.



8) Prep & Install the wheel Assembly.

After getting the wire shape as square as possible without the wheel installed. Put the prop adaptor into the prop hub and install both onto the wire square. Note you will find that the assembly will slip around even sharp corners at this point.

 

 

9) Bend the wire leads vertically (see the photo for correct orientation)

 

 

10) Create and install a binding collar.


Make  a collar from the clear tube. Cut a piece of clear tube approximately 5mm long and install it to bind the wire ends as shown. Note how well this cleans up any bend imperfections.

 

 

11) Form the rudder guide

Bend the longer wire end just short of 90 degrees to eventually align approximately with the rudder.

 

12) Form the axle bushing

Cut a length of tube just short of the axle width.  Slit one side of the tube the entire length. If you kept wire square tight it should be about 7 to 10 mm in length

 

13) Install the axle bushing

Deform and slip the tube onto the axle as shown below. Slide the tube though the prop adaptor

 

14) Finished axle bushing installation

It should look like the photo below. Apply a drop of CA to hold tube the prop hub if desired. Note the bushing provides the rolling surface of the wheel assembly on the axle and prevents the assembly from riding up the side of the wire square while removing most of the sloppiness. Look at this carefully to see what's going on here.

NOTE: The split tube axle bushing is trapped by the prop adaptor while the wheel is centered and trapped by the bushing. CA or not this is never going to come apart

 

15) Cut two guides from the remaining tube

Cut 2 each pieces of clean tube to form the vertical stabilizer pivot point and the horizontal rudder slider. Both should be 10 to 20 mm long. The completed tailgear assemble is shown below with both guides installed and it weighs in at 1.3 grams

 

16) Prepare the fuselage for the tail gear installation

 With a wood skewer poke a hole in the fuselage and vertical stabilizer assembly as close to the rudder as practical.


17) Insert the vertical stabilizer guide tube

Dab a little hot glue into the hole push then push the vertical stabilizer guide tube in until flush with the fuselage. Note in the photo below the tube is not pushed in completely and thus does not show the completed installation 



18) Install the tailgear assembly into the vertical tube



19) Secure the horizontal tube slider onto the rudder

Make your final adjustments to the tailgear assembly and secure tube horizontal slider onto rudder with hot glue. Note once secured the assembly should be somewhat sprung against the fuselage if it is installed correctly. Cut the horizontal wire to length but note it should always extend past the end of the slider tube to prevent it from jamming



Final Thoughts

 This same technique can be scaled up for larger aircraft. Hope you got a least one good idea from this article. Thanks for looking and good luck your builds!


Wheel for my FT 3D next to the mini

 

 

Demonstration



Taxi Test

COMMENTS

The-One-Who-Never-Crashes on January 1, 2016
Fantastic article and design! I had an idea for a replacement for the pen cartridge: a coffee stir. Great job on the build, too!
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circle&stripe on January 1, 2016
Thanks for the kind words and the careful read. It might work with a coffee stir, but let me know if you try that? Look forward to more of your articles too.
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The-One-Who-Never-Crashes on January 3, 2016
Thank you!

I used to use old pens before I found out about coffee stirs... Aluminum O.D. tubing should also work.
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Fearless FPV on January 1, 2016
Excellent! Love it!

Happy new year!
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circle&stripe on January 1, 2016
Thank you and to you too!
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Flynn on January 7, 2016
Genius! Fantastic idea! I love the way you used common items to do this, 5 stars! I can't wait to try it. Thanks so much!
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circle&stripe on January 7, 2016
Thank you very much, I just completed my Viggen and I stole your landing gear design
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jonmierke on January 10, 2016
Thank. You for this wonder full idea I think I'm giong to try it out with my sport cub.
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circle&stripe on January 11, 2016
Thanks! Good luck with your build, post pictures.
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NCC1701 on December 31, 2015
Great work!

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circle&stripe on January 1, 2016
Thanks I'm glad you looked at it!
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Ron B on January 2, 2016
I just finished up a spitfire with landing gear and wanted a steerable tail wheel but not the expense of a store bought one as I was keeping this build real cheap and I was concerned about the pressure put on the rudder. I ended up just doing a tail skid. Next time I will try this out
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circle&stripe on January 3, 2016
It's a good observation you make that this does not significantly load the rudder. Sounds like this might be be a good solution for you, thanks and good luck!
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quimney on January 4, 2016
Thanks for sharing this article. The way you took the load off the rudder is something I have never seen before. The control arm sliding in a tube is brilliant, it completely eliminates the alignment issues that always come up when I try to add a tail wheel and it does it without springs or other complications.
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circle&stripe on January 5, 2016
Thank you, I am very happy how the loads were distributed too.
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jamboree1 on January 15, 2016
Such a great article. I will be using this for my Re-Vamped Spitfire. Pics of this plane is on forums under ft designs and other swappables. Quite a unique design that solves 3 problems with steerable tail mount all in one stroke.
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circle&stripe on January 16, 2016
Thanks! I like what you are doing with the Spitfire, look forward to the completion.
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DOOM on January 1, 2016
Awesome, this is like RC-Hobby Origami, Black belt RC-hobby Origami!
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circle&stripe on January 1, 2016
That's high praise, I wasn't sure anybody would read it to the end. Thanks!
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TimmyGT on January 1, 2016
I had no idea where you were going with this till I got to the end, then I was like "ooohh, that's brilliant!!" Excellent job, can't wait to try it
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circle&stripe on January 1, 2016
Yeah the article seems to take the long road to get what I thought would be an easy idea to convey; but once I sat down to write, it just grew and grew. Glad you stuck it out to the end and thanks for the kind words!
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guggyman123 on January 3, 2016
Awesome article!
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Steerable Tailwheel for your Mighty Mini