UNIVERSAL MAINTENANCE FREE TAIL-WHEEL

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Blackhawk

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My new designed tail-wheel could be of interest to the group for any type of tail-wheel homebuilt aircraft.


Specifications are:

CNC machined 6061-T6 billet Torsion block and axle with polyurethane compression bars

CNC machined 6061-T6 billet wheel cheek plates

316 stainless steel mounting shaft

2 x sealed 316 stainless steel case bearings with ceramic balls for pivot in torsion block

All bolts are 316 stainless steel

6" x 1-1/4" pneumatic wheel with 2 x sealed 316 stainless steel bearings and black alloy rim

Total weight as shown in photo is 1.68kg

GraemeTAILWHEEL 002a.jpgTAILWHEEL 004a.jpgTAILWHEEL 005a.jpgTAILWHEEL 010a.jpgTAILWHEEL 012a.jpg
 

cluttonfred

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The polyurethane torsion suspension is a very interesting approach and it looks like quality work but this probably belongs in "Supplier / Manufacturer Announcements." If you are looking to sell them, then pricing and shipping costs to various countries would be helpful. I'd also be interested in how you are recommending connecting this tailwheel for steering. Not many people use free-swiveling tailwheels anymore and yours does not appear to be locking. Also, how would you recommend connecting the shaft to the fuselage? Bolted-on flat springs seem more common.
 

Blackhawk

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Hi Matthew,

At the moment I'm looking for feedback to see if there is a market for these as I'm sure there is.

But to get pilots opinions on the design first will help in the decision to manufacture or not.

I will be posting more info for fitting when I fit it to our plane.

Graeme
 

Dana

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I like the poly bushings. How does it mount and where are the control arms?

Dana
 

Blackhawk

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Hi Dana,

Because all installations are different, the control arm will be built by the aircraft builder to suit their installation; there are 4 mounting holes for the control arm to be attached to the torsion block. (photo)TAILWHEEL 003a.jpg

I will show the mounting in the next couple of weeks.

Graeme
 

cluttonfred

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Very cool, Graeme. If you were to decide to sell sell these, I'd suggest a standard, longish dual control arm that builders could drill for the control chains and cut down/trim as needed. I'd also suggest a short shaft and bracket options to suit common sizes/angles of flat or round tail spring. I'd be interested in any calculations or tests you might have done regarding force on the tailwheel and deflection of the polyurethane as that should suggest what weight this design could handle.
 

Turd Ferguson

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How much friction on the swivel? Is it adjustable? Are there any mounting requirements to avoid shimmy?

What is the steering range and can steering be disconnected to allow for free swivel without tools? Specifically, if I want to push the plane backwards into a hangar, can I do it with plane on the gear? Or will I have to raise the tailwheel off the ground?

Also curious about the mounting as it doesn't appear to fit the universal type tailwheel mounting provisions.

What kind of load /speed range is the tire rated for? It looks like a scooter tire?
 

wsimpso1

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What is the spring rate and energy storage of the tire/wheel and of the polyurethane system? Is this intended to be hard mounted, or would it still require a spring arm mount?

Billski
 

Blackhawk

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Hi Billsky,

It gets hard mounted to the fuselage and does not require a spring arm mount or control chains.

I should mention it is designed for aircraft up to 1400lb.

But if needed a larger version will be available later.

More information will be available in the coming weeks.

Graeme
 

cluttonfred

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Graeme, I can see how your design would not require springs or chains to the control arm because the shock absorption happens at the swing arms/polyurethane bumpers. The control arm isn't bobbing and weaving like with a conventional tail spring. I'd be very interested to see how this could be securely mounted to a wooden airframe. It almost looks like you could cut flats in the forward and rear surfaces of the vertical shaft and drill a pair of holes to through-bolt it to a vertical surface (bulkhead, reinforced rudder post, etc.).

For my someday VP-2 project, I had in mind the steel tailwheel spring from the plans and something like a Matco 6" single-arm tailwheel. Total weight of that arrangement with all the hardware, chains/springs, etc, would be about 4.0 kg since the spring alone weighs about 1.0 kg and the tailwheel assembly 2.3 kg. It looks to me like your design would come in substantially lighter and I don't mind if it doesn't free swivel.
 

Dan Thomas

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As a longtime taildragger pilot and homebuilder, I can tell you what is needed: a fully steerable, castering, shimmy- and dirt-resistant tailwheel. I have a much-modified unit on my Jodel that doesn't shimmy and is steerable and castering.

The popular certified wheels, Scott (and clones) and Maule both have steering and castering functions. The Maule usually has lots of slop between the steering arm and fork, the Scott less so. Both use friction devices for shimmy control, which also make steering sluggish and sticky and doesn't work well anyhow. Neither of them are well sealed against dirt, and mine is no better that way.

Shimmy has to do with several factors: dynamic balance of the wheel itself, the angle of the steering pivot, and the flexibility of the tailspring suspension. Without addressing these, shimmy has to be controlled with something that will allow rapid-enough movement to give quick control, but damp the very rapid movement that shimmy creates. A hydraulic, eddy-current or polymer damper could work but it all has to fit in a tiny space and be dirt-proof.

And there are many types of tailwheel mountings, just to make it really interesting.

Designing a tailwheel that solves all the problems is a lot harder than it looks.

That type of suspension in the OP's assembly is a really good idea. It's been used in small trailer axles for almost 50 years and has worked well.
 

FritzW

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I really like the (cast?) poly compression bars.

...there are 4 mounting holes for the control arm to be attached to the torsion block
I drew up a Matco-style ultralight full swivel control arm that looks it would be a plug and play fit to the top of your torsion block.


...I'm looking for feedback to see if there is a market for these as I'm sure there is.
It looks like a great design but the vertical mount isn't optimum for most of the airplanes on my "lust list".
 

Toobuilder

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Looking at the details of the components it appears that there is no spacer between the inner races of the caster bearings. If that is the case, how do you eliminate preload on the bearings when you torque the caster bolt? Also, it appears that the caster "axle " ends at the top bearing. This leads me to believe that the caster bolt is functioning as the axle between the bearings and therefore loaded in bending in addition to loading the threads directly on the shear plane. Am I seeing that right? Also, what secures the center suspension block in place to keep the fork plates from moving off center during side loads and fretting on the main body?

Neat bit of machining, but I'd suggest a more "conventional" mounting scheme... If it won't bolt to a stinger or a leaf spring mount, it's going to be a tough sell.
 
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Victor Bravo

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Congratulations on inventing and designing a new aircraft accessory. But I'm confused by the photos.

What are polyurethane "compression bars", where do they mount, and what do they do exactly?

If these "bars" that I cannot see will replace the traditional leaf spring or "stinger" rod spring, how much movement do they allow? My traditional leaf spring allowed the tail of the airplane to move downwards about 4-6 inches after the tailwheel contacted the ground. This provided a very soft impact. I cannot see how or where this type of movement occurs with your design.

If I am reading Fritz' post correctly, he has drawn a control arm similar to the Matco system. If this is true, and if it will fit on your tailwheel, it will allow a very clever and robust "full swiveling" capability that would make the tailwheel much more desirable to the market. The Matco swiveling/steering system is brilliant in its simplicity, and IMHO puts the other swiveling mechanisms to shame.

EDIT: Never mind, I can now see the pink colored "bars" in the block. I now understand the torsion/impact system.
 
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Dan Thomas

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Looking at the details of the components it appears that there is no spacer between the inner races of the caster bearings. If that is the case, how do you eliminate preload on the bearings when you torque the caster bolt? Also, it appears that the caster "axle " ends at the top bearing. This leads me to believe that the caster bolt is functioning as the axle between the bearings and therefore loaded in bending in addition to loading the threads directly on the shear plane. Am I seeing that right? Also, what secures the center suspension block in place to keep the fork plates from moving off center during side loads and fretting on the main body?

Neat bit of machining, but I'd suggest a more "conventional" mounting scheme... If it won't bolt to a stinger or a leaf spring mount, it's going to be a tough sell.
The beauty of this design is the ability to bolt it to a rigid tailspring. Most springs, as they flex, let the pivot axis tilt forward, one of the worst sources of the instability that causes shimmy. Just look at the bent, shimmying caster on a shopping cart. If this new idea was mounted stiffly, and the torsion system took the bumps, the pivot axis doesn't change and shimmy is less likely.
 
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