Tail Wheel Spring

[Murray Randall]

Maybe the sliding tail post with compression coil shown in the attached pic is lighter than a conventional leaf spring. The weight of wheel, bracket, both springs is just shy of 1.5 lb. The smaller tension spring keeps the assy attached when the tail is off the ground. The fuse tail post is .75 .035 with a .625 in long .75 .049 extension but welded on the bottom to better guide the .625 .035 8 in long sliding pillar tube. The castering wheel is a buck sixty nine, the compression spring is 5 buck item both from the hardware store. You really need the expansion reamer to clean up the tail post bore. I use expansion reamers from drills and cutters.com often. I installed a grease fitting in the tail post to lube tubes. The system gives me 100 lbs per inch rate at the tail post. You might notice that I have two positions for the tail wheel steering arm. I do that to vary the steering angle of the tail wheel. If you have equal length aero rudder cable arm and tail wheel cable arm the rotation angles will be equal. If you reduce the tail wheel steering arm length you can get more angular wheel rotation than the rudder stops allow.  The wheel itself I turned out from a 1 inch thick piece of nylon. The axle is a .625 .035 tube.  Incidently I tried making a carbon fiber leaf spring and failed miserably.  I would like come up with a better assy retention system than the tension spring shown.....any ideas?    thanks Murray

[rockiedog2]

hey Murray thats cool. antiquey lookin. i turned out a nylon wheel one time. light as a feather. looked just about like yours...put it on the axle with a fender washer and a fiber lock nut cinched up kinda loose. went over to the big airport and landed on the pavement...next thing i knew i was out in the grass looking the other way. got out and lkd at the tailwheel. the thing had vibed or something and ran the fiber lock nut up against the big washer and locked the tailwheel solid. ground most of the bottom half off the wheel...nylon has no traction on pavement...went around like a top. the airport bums laughed their ass off at the jet pilot ground looping his legal eagle. (i never told em anything about the tailwheel). turned it around, fired it up took off went back to the strip no prob. that tailwheel is on the wall now with the busted up props and stuff
 i like the return spring.
glad to see you back out

[Poorman2]

Murray, thats what I call thinking outside the box. It looks very interesting, but will it work? Thats yet to be seen I guess. Thanks for sharing.

[Murray Randall]

Yeah safe and sound sideline laughers can't ground loop.

I set this up with a .626 hole in the wheel running on a .625 axle tube, no bearings. Its a little tight as it stands now. The tube is drilled both ends for a hair pin that runs thru little tabs on the arms to prevent rotation of the axle. The wheel should hopefully spin on the axle. I had a similar sliding pillar on a Fleet 16B but of course it had sophisticated bronze bushings. This a pretty crude.  And then I haven't landed on a paved runway in a very long time now. The 4 in dia wheel was turned from a piece of hard white plastic scrap from a local boat yard so I really don't know what the material is. But is light and machines pretty cleanly. 

Now I'm puzzeling over a really light floor board that would serve also as bottom skin. Any brilliant ideas out there? I appreciate the advice on using peel ply for covering. I might try a small piece to see how it goes.

[PropMan]

Murray, what made you abandon the X-country ski for a tail wheel spring?

[Murray Randall]

I had to give up the X-country ski to get a desirable caster angle.  I have raised my tail post to get a higher angle of attack when in the tail wheel is on the ground. My thinking there is when landing full stall I wanted the wing stalled or at 15 degress.  And if you get a bounce off the mains raising the nose and the wing goes to higher higher angle of attack and is not stalled you ballon up more. And when I rotate smartly on take off I don't like the tail wheel to smack the ground. So I raised the tail. Then I bent the tail post six degrees to help get the caster back toward neutral. But I still need six degrees more caster. So I think that kinda forces me into a tail spring bend. Thats several unnecessary changes to the XL! But its an experiment and I'm having a good time.  The X-c skis from the town transfer station were wood that looked like stika to me, so I had doubts about the strength, but would have gone ahead if I didn't need the bend.   Simple question with a long drawn out answer eh? 

[PropMan]

Well I'm still interested in a laminated tail spring, I got lots of laminate!

Good to hear and see different ideas.

Keep up the fun;D

[Jlwright]

I will make my own carbon fiber and fiberglass tail wheel spring. You can also buy one from George on the Tennessee Lonesome Buzzard forum.

[Murray Randall]

Here's pics of my attempt at a carbon fiber tail sprg.  Its got 20 plys of very thin glass in the center with 10 to 20 layers of unidirectional CF on top and 10 layups of CF on the bottom. The weight started to get up towards one lb, the stiffness was still shy of the 100 lbs per inch that Joe says works well. During spring rate testing and proof testing the thing broke just under the tail post.  I quit.  Not stiff enough stifness and getting too heavy.  Every day polyester resin was used, not epoxy though.  I could make 10 layers before it started to harden up and I was clamping to squeeze out excess resin.  Used maybe 30 to 50 clamps. You can see the wicked curve in my spring! The roll of CF coast a mean $130!  There's also a pic of my stick mounted dual brake handles very much modified from Leading Edge brake handles with my method of extending the Mikuni two into one cable and throttle lever. I still don't like the Mikuni spring to close.  Good for motorcycles put not airplanes. I'm thinking about the ramifications of take the closure springs out of the Mikunis. These are just like the old SU carbs on all 1950's British motors. What do you guys think on that subject please?

[Tom H]

Hey Murray, I noticed that old Singer in the background.  What's it used for?

I have a Singer 21W180 from early 1900's, came out of the Jeffersonville, In. Quartermaster Depot, where my grandfather used to work.  It has all kinds of one-of-a-kind attachments that he made for special projects.  Good for medium weight fabrics.  Probably used to make tents and leggings for WW1.

It wasn't running very good when I got it, but, amazingly, I found the service manual for it on the internet, and got it running good.  I used it to make the sling seat for our LEU, Treehugger.

[Murray Randall]

That Singer is a 29-4 oscillating shuttle extended arm machine that allows you to sew say boots. Its an early 1900's machine that is popular in all the third world countries to make and repair shoes and in the US for ranch work, holsters, saddles. The foot will rotate 360 degrees to sew in any direction. It is really useful to us for making full span wing envelopes as there is plenty of room to gather up the sewn material. The model was in continuous production for 50 some years. It is foot treddle operated and tires the legs though.  It will sew any leather that I have used, but I also have a conventional electric commercial Singer that frankly does the bulk of my sewing. The Singer is 21W is a great old double needle machine.  Double needle is what you get with a commercial aircraft envelope. I personally do not bother to double needle or double stich as all my seams are tape covered but I'm in the small minority on the subject.  Your 21 is wonderful and fully deserves your attention! Great for envelopes.

[Tom H]

My 21W180 does not have double needle.  Maybe that was an option for that model series, though.  Probably a gazillion of them made way back then. 

I know I'll need some parts for it some day, such as the rotating hook.  You know of any sources for parts?

[Murray Randall]

Yup.  I'm off base.  I saw a pic of your 21W218 that looked like it had two needles.  But that is not true, none did. There is a piece on the web collectorsweekly/19062 on the machine. I tried to send it to you but wasn't able. It has a half interesting history.

[weasel]

.  I would like come up with a better assy retention system than the tension spring shown.....any ideas?    thanks Murray

Hey Murray,

How about a very small cable with a loop on each end. run a 3/16 bolt through the tail-wheel tube and one loop of the cable and then another 3/16 bolt though the tail post and the other loop of the cable.  I don't know if this could be done lighter than the spring or not.