What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Tip: DIY Locking Tailwheel

Toobuilder

Toobuilder

Well Known Member
While fully functional, I've never been a fan of steerable tailwheels with the external chains, springs, etc. So in the spirit of "why not?", I decided to try a locking tailwheel for the Rocket. And of course, I didn't like what was commercially available, so I decided to whip up a prototype and see how it worked. Admittedly, the design goals, even if fully realized, are hardly a clear cut advantage over the Vans or similar designs. The design goals in no particular order are as follows:

Lighter (nailed it- this one is half the weight of the standard setup)
Less drag (probably - but doubtful I'm going to see a speed increase. I'm going to claim 50 knots until testing proves otherwise)
Less likely to snag on stuff (the wheel is smaller, but the whole assembly is shaped to slide over obstructions)
No load on the rudder (yep, no connection at all)

And the big one: satisfy my restless need to change a perfectly functional design for no apparent reason.

Anyway, the concept of operation revolves around a spring loaded pin that locks the kingpin within a few degrees of center. When locked, I have enough slop and flex in the stinger to perform shallow s turns on the runway, but I need to unlock for tighter stuff. I have made a few landings with the thing completely unlocked as well as locked. Neither are a problem in normal wind conditions. Now that it's installed "permanently", we'll see how it holds up in regular service.

I'll keep you posed as I get some hours on it.

wwgait.jpg


huoy04.jpg
 
Last edited:
very cool Michael, any weight savings, that far back are important. Do you use a cable to unlock the pin?
Get flying, I want some flight reports!
 
Thanks Tom. The locking pin is a 1/4 inch piece of hardened shafting that rides in the tube on top of the stinger socket. Also in that tube is a compression spring which provides the motivation for the pin to remain locked. Finally, and not very visible in the picture, is a cable guide that runs out of the tube, along the stinger, and up to one of the fuselage bulkheads. I was going to use a motorcycle throttle cable here, but I found a surplus push pull (heater, vent, etc) cable assembly laying around the shop. Since one end of this thing already has a nut for a bulkhead connection, it worked out well. I have a piece of music wire pulling the pin. This design differs from others I've seen in the respect that the actuating mechanism is completely enclosed - there's no wires to snag on brush, rocks, etc. Anyway, Fwd of the bulkhead connector, the music wire is crimped to 1/16 aircraft cable running through snap bushings all the way up to the fuselage bulkhead near my left knee. Currently, I just grab the cable and pull a little sideways to unlock the pin. Future plans include a dedicated lever mounted low on the throttle which will snap over center in the "unlocked" position. If This works out as planned, advancement of the throttle will automatically move the lever back to the locked position in case I forget.

Before anyone asks why I didn't do it like a T-6 or P-51 and have down elevator unlock the pin, I'll tell you that I did not want to find myself in a situation where I needed "down" elevator taxiing a Rocket. The tail is just too light and I don't want to get in the habit of casually moving off of full aft stick. I think that's a prop strike waiting to happen.
 
Stick operated

Michael, save some more weight by attaching the cable to your elevator pushrod, the way all Air Tractors are done.

With the elevators level, the stick is locked. With the stick all the way forward, it's unlocked and we steer with brakes and rudder taxiing, no cables at all.

Best,

Edit..didn't read your last paragraph regarding down elevators.
 
Last edited:
How about this:

pierre smith said:
Michael, save some more weight by attaching the cable to your elevator pushrod, the way all Air Tractors are done.

With the elevators level, the stick is locked. With the stick all the way forward, it's unlocked and we steer with brakes and rudder taxiing, no cables at all.

Best,

Edit..didn't read your last paragraph regarding down elevators.
Click to expand...

Make it so the lock is engaged with the elevs full up, and dis-engages at the point the elevs are in trail. Seems like this would be owners- choice (the F1 has a heavier tail weight, so down elev is a smaller problem) as the owner could set it up either way (cable clamps to the elev push tube).

If the cable attached to the elev horn, the setup might be easier.

The Beech 18 uses a twist-lock cable to unlock a small pivot-mounted pc of 1/4" thick steel bar that lays in a slot to lock the wheel. As with your design, it allows some deflection so taxi is not such a problem. Operating this system is easy, and intuitive.

Great stuff, Mike!

Carry on!
Mark
 
Michael, It looks like you have created a well thought out design to meet your needs. I continue to be amazed by all the great ideas folks on this site come up with to improve their aircraft. Nicely done!

Frank
 
vfrazier said:
Clever design. There is always more than one way to skin a cat. I do have to ask, what's the weight of that long cable?
Click to expand...

It's 10 feet of 1/16th aircraft cable (no outer sheath) running through a few snap bushings.... It's only a few ounces.

The whole tailwheel assembly, cable, etc. weighs a little under 2.5 pounds on my digital fish scale. Contrast that with the vans assembly, chains, etc at a touch over 4.5 pounds
 
Tailwheel

You can have the best of both worlds by using a single steering arm and disconnecting the steering arm for tight turns and moving the airplane around.
The release pin is set up on the steering arm, requires a retainer for the top.
 
Steering requirements ?

Please educate me. I fly an antique biplane with no brakes an no tail wheel. There is enough rudder authority for normal taxi requirements . However, crosswinds and "sharp" turns are a problem.
Here is my question; with brakes, why would an RV need a steerable tail wheel. This is not a rhetorical question. I have never flown an RV, just looking forward to the grin soon!
 
You don't normally "need" a steerable tailwheel at all - it just adds one more element of control. I have done several landings to full stop with this tailwheel completely free swiveling, and the rudder is powerful enough to keep you pointed in the right direction.

The one drawback that I've experienced with the Vans and similar Aviation Products tailwheel is the tendancy to unlock just at the wrong time in the landing roll. I'm hoping that my design will be more consistent and remain locked no matter what I throw at it.
 
Larry DeCamp said:
Please educate me. I fly an antique biplane with no brakes an no tail wheel. There is enough rudder authority for normal taxi requirements . However, crosswinds and "sharp" turns are a problem.
Here is my question; with brakes, why would an RV need a steerable tail wheel. This is not a rhetorical question. I have never flown an RV, just looking forward to the grin soon!
Click to expand...
A steerable tailwheel gives you more authority when taxiing, and reduces the need for using the brakes to make turns. With anything but a nose-on wind, I find I need to ride some brake to stay straight on the taxiway... The small rudder on the -6 isn't quite enough in crosswinds at taxi power settings.
 
Be nice to your tailwheel

Toobuilder said:
The one drawback that I've experienced with the Vans and similar Aviation Products tailwheel is the tendancy to unlock just at the wrong time in the landing roll.
Click to expand...

This is almost always a maintenance problem. The locking/steering tailwheels like Van's, Aviation Products, Bell's, or ours work very well, but they do require periodic lubrication and inspection. Virtually all of them can be made to steer like new with about $30 of new parts (control arm and locking pin). With normal maintenance, your tailwheel should perform reliably for many hundreds of hours.

Stated another way, these tailwheel systems should not unlock during the takeoff or landing roll ever. They should only unlock when the aircraft is asked to turn very sharply, such as when parking. If they do otherwise, fix them!

We have a free maintenance/tech sheet that I'll gladly email to anyone, just email me a request to [email protected]

When you think about what you're asking the tailwheel to do, a bit of periodic maintenance is a small thing. The tailwheel assembly gets dragged through mud, ice, grass, and other nastiness while covered with engine oil dribbles. Is it any wonder that it needs a clean and lube once in awhile?

Last comment: To maintain any of these TWs properly, you must disassemble them by removing the large AN364-820 nut and then dropping the fork out of the mounting housing. Then wipe it off, inspect the pin and its mating notch in the control arm, deburr the pin if needed, grease, and reassemble. It's a 10 minute job and easy to do.
 
+1

vfrazier said:
<snip>

When you think about what you're asking the tailwheel to do, a bit of periodic maintenance is a small thing. The tailwheel assembly gets dragged through mud, ice, grass, and other nastiness while covered with engine oil dribbles. Is it any wonder that it needs a clean and lube once in awhile?

Last comment: To maintain any of these TWs properly, you must disassemble them by removing the large AN364-820 nut and then dropping the fork out of the mounting housing. Then wipe it off, inspect the pin and its mating notch in the control arm, deburr the pin if needed, grease, and reassemble. It's a 10 minute job and easy to do.
Click to expand...

FWIW my arm/pin lasted a bit over 300hrs, with normal ops involving a not very smooth sod runway, and the 2"x3/4" expansion tips at Reno/Stead. New parts brought 'er back to new standards, and added a tail tie-down ring: no more tying a rope around that always nasty weldment.

Carry on!
Mark
 
vfrazier said:
This is almost always a maintenance problem. The locking/steering tailwheels like Van's, Aviation Products, Bell's, or ours work very well, but they do require periodic lubrication and inspection. Virtually all of them can be made to steer like new with about $30 of new parts (control arm and locking pin). With normal maintenance, your tailwheel should perform reliably for many hundreds of hours.

Stated another way, these tailwheel systems should not unlock during the takeoff or landing roll ever. They should only unlock when the aircraft is asked to turn very sharply, such as when parking. If they do otherwise, fix them!

We have a free maintenance/tech sheet that I'll gladly email to anyone, just email me a request to [email protected]

When you think about what you're asking the tailwheel to do, a bit of periodic maintenance is a small thing. The tailwheel assembly gets dragged through mud, ice, grass, and other nastiness while covered with engine oil dribbles. Is it any wonder that it needs a clean and lube once in awhile?

Last comment: To maintain any of these TWs properly, you must disassemble them by removing the large AN364-820 nut and then dropping the fork out of the mounting housing. Then wipe it off, inspect the pin and its mating notch in the control arm, deburr the pin if needed, grease, and reassemble. It's a 10 minute job and easy to do.
Click to expand...

630 hours on my Van's standard (Bell Fork). Take it apart every 25 hours. Clean fork post, bushings and pin, polish the edges of the locking pin, grease with Aeroshell 5, put it back together. Never had a problem with it and it has never unlocked when I did not expect it too. Takes ten minutes.
I do admire your design and ingenuity.
 
vfrazier said:
We have a smaller version of our Screaming Eagle tailwheel assembly that is intended for Sonex and other light taildraggers. It may be possible to put it on an RV or Rocket, but we haven't tested it on them. It weighs 33 ounces with the 4" tire.

http://www.flyboyaccessories.com/product-p/1130.htm
Click to expand...

Hey Vince, don't forget, I have your prototype Screamin' Eaglet Fork, and Dayton's 4" TW. Tested it prior to racing it at Reno this year, both with and without a steering arm. It works really well, and I ran it at Reno with no arm.

IMG_1262.jpg


Those monster expansion joints at Stead that Mark mentioned makes the ride kinda rough with the 4" TW, so it is a racing-only mod for me, since Stead is the home-drome. However, I did find it to be very comfortable in operations off of more normal ramps and strips.

I run the standard Screamin' Eagle Fork and 5" DJM TW in normal ops, with a steering link. Concur with the simple maintenance requirements. Periodic cleaning of the assembly, and touching up any burrs on the pin, keeps it working well. Occasionally it'll stick, and make the wheel release early, but that's when I've let it get too dirty (or have been blowing a lot of smoke at it).

I've not had my B-18 checkout yet (Mark), and haven't flown a P-51 yet (yet? ;)), so I'd like to ask what a locking TW feels like. The steering link is great on the ground?no brakes for taxiing, and a good feel on TO and LNDG roll. What does the locked TW feel like on the roll?

Mike, I also like the ingenuity?interested in how it flies, and how it fees to operate the mechanism.

Cheers,
Bob
 
rvmills said:
... What does the locked TW feel like on the roll?

Mike, I also like the ingenuity?interested in how it flies, and how it fees to operate the mechanism...
Click to expand...

Just got back from a Vegas weekend with a bunch of "stuff" in the baggage compartment. While I fell a bit short of my claimed 50 knot speed increase, I did see a faster cruise than I'm used to. Of course the temperature is significantly cooler than the last time I flew, so that's likely the key. As an aside, I can see that my efforts to get this thing to cool in the heat of the summer is now working against me. My oil temp settled in at a way too cool 150 degrees in cruise and my hottest CHT was only 335.

I was happy to feel the tail tire touch down after an hour of flight. I half expected it to drop off in the desert somewhere. Rollout and the lengthy taxi were non events. Though the small tailwheel does make its presence felt on every bump, it's not too bad. One mistake I made was allowing too much slop in the locking mechanism. I only have a few degrees off center, but even that is too much. Also, the pin tends to get stuck if I have the caster pre loaded in a turn. I can't change that, but my attachment method is going to have to be beefed up so it can handle a healthy tug on the cable to disengage.

The experiment will continue.

And Bob, you're welcome to fly it next time you're in town.
 
Tail wheel will come unlocked in Full Side Slip

In my RV4, in a full sideslip (full rudder) when wanting to lose altitude the tail wheel will come unlocked. And if your dealing with some good cross winds and still using lots of rudder there is a good chance when you touch down and the tail wheel will still be unlocked and it will be free swiveling (unlocked) when the tail comes down. Not a big deal unless your X wind component is higher than 15+- knots when your tail comes down then you may not have enough rudder to counter the weather vane tendency.

And we know what happens at that point.:D
 
If you want it to stay locked you can mill the internal cam groove inside the mounting housing further around the ID, thus delaying the unlocking.

Obviously, there is a sweet spot between unlocking when you want it to and shearing parts when trying to make a sharp turn. Your rudder chain springs should allow enough "bounce" to allow the wheel to unlock before bad stuff happens.

YMMV! Have fun!
 
Hey Michael, how is the locking tail wheel working? I'm still interested in something like that.

Thanks

Tim
 
I need to make the spring that pushes the locking pin home stronger, but other than that I'm perfectly happy with it. I have purposely abused it to get it to misbehave and it just doesnt.

Much of that credit goes to the basic Rocket design however... It just does not need much help to go straight. In fact, locked or free swivelling, it just doesn't matter much. The only reason I'd like a stronger locking feature is taxi in a crosswind.
 
Yes that is what I'm looking for as well. Coming in after a full sideslip in a strong cross wind and unless you have the freedom to kick the rudder straight prior to touch down and hope the wheel locks in place it may still be unlocked when you land.

In most cases the ground handling is good on my 4. But in strong X winds there is not enough rudder authority for a free castering rear wheel once the little wheel touches down. The little extra safety with the wheel locked would be nice to have.

Tim
 
Yep, there is a certain speed where the rudder just cant keep up. I'm thinking about a 2nd version of this tailwheel with a larger spring tube. I'm at 1/4 ID right now and I cant seem to find the right spring for it. Too stiff or too light... I believe a larger diameter tube will open up the spring selection possibilities a bunch.
 
Last edited:
You must log in or register to reply here.
Back
Top