Wing wheel from Craggy Aero

On Thursday, April 30, 2020 at 7:20:25 PM UTC-7, Andrzej Kobus wrote:
On Thursday, April 30, 2020 at 7:38:39 PM UTC-4, 2G wrote:
I wanted to replace the Cobra wing wheel I had been using because 1) it goes with the ASH26e I have for sale and 2) the tire scrubs the tarmac as I go around turns, putting stress on the wing. I ordered the CA WingWheel from Craggy Aero because the wheel swivels with the direction of travel:
http://www.craggyaero.com/ground_handling.htm
And the length is adjustable which helps greatly for storage. It is also has a spring shock absorber that the Cobra wheel does not have. I tried it out today and towed my ASH31Mi (with the 21M tips) around the Richland, WA airport (KRLD). The wing wheel worked great and put no stress on the wing.. The Cobra wing wheel would bend inwards as the tire was dragged sideways in a turn - the CA wing wheel tracked perfectly and was always in a vertical position. The height of wheel was more than adequate to keep the wing tip above obstructions (taxiway markers and signs). This version also has improved straps over the earlier design. Fabrication of all components is excellent - no thin walled aluminum tubing, for example. The tire is not pneumatic, so it can't go flat. It is wide enough so it will not drop into pavement cracks. It is well worth the additional cost over the Cobra wing wheel - I was always holding my breath when I used it.

Tom

The best wheel I have had is the one from MM Fabrication. Very sturdy, well fitting and does not stress ailerons.

That wheel does not swivel, so it will suffer from the same scrubbing problem that the Cobra wheel has.

On Friday, May 1, 2020 at 1:31:09 AM UTC-4, 2G wrote:
On Thursday, April 30, 2020 at 7:20:25 PM UTC-7, Andrzej Kobus wrote:
On Thursday, April 30, 2020 at 7:38:39 PM UTC-4, 2G wrote:
I wanted to replace the Cobra wing wheel I had been using because 1) it goes with the ASH26e I have for sale and 2) the tire scrubs the tarmac as I go around turns, putting stress on the wing. I ordered the CA WingWheel from Craggy Aero because the wheel swivels with the direction of travel:
http://www.craggyaero.com/ground_handling.htm
And the length is adjustable which helps greatly for storage. It is also has a spring shock absorber that the Cobra wheel does not have. I tried it out today and towed my ASH31Mi (with the 21M tips) around the Richland, WA airport (KRLD). The wing wheel worked great and put no stress on the wing. The Cobra wing wheel would bend inwards as the tire was dragged sideways in a turn - the CA wing wheel tracked perfectly and was always in a vertical position. The height of wheel was more than adequate to keep the wing tip above obstructions (taxiway markers and signs). This version also has improved straps over the earlier design. Fabrication of all components is excellent - no thin walled aluminum tubing, for example. The tire is not pneumatic, so it can't go flat. It is wide enough so it will not drop into pavement cracks. It is well worth the additional cost over the Cobra wing wheel - I was always holding my breath when I used it.

Tom

The best wheel I have had is the one from MM Fabrication. Very sturdy, well fitting and does not stress ailerons.

That wheel does not swivel, so it will suffer from the same scrubbing problem that the Cobra wheel has.

Not true, the other wheels have scrubbing problems because they are flimsy and they fit poorly. I tow on concrete all the time, never have had a problem. I had all kinds of wheels before and they were all terrible, especially on concrete. I had the same concern as you before I bought the MM Fabrication wheel and I asked Mark to modify the wheel to include swivel. He said to try it they way he makes it and it works perfectly. He uses precise wing airfoil to manufacture the wheel, so each wheel fits only one glider type. This is why it sits on the wing perfectly and it does not move at all. I am a very happy customer!

On Friday, May 1, 2020 at 4:09:16 AM UTC-7, Andrzej Kobus wrote:
On Friday, May 1, 2020 at 1:31:09 AM UTC-4, 2G wrote:
On Thursday, April 30, 2020 at 7:20:25 PM UTC-7, Andrzej Kobus wrote:
On Thursday, April 30, 2020 at 7:38:39 PM UTC-4, 2G wrote:
I wanted to replace the Cobra wing wheel I had been using because 1) it goes with the ASH26e I have for sale and 2) the tire scrubs the tarmac as I go around turns, putting stress on the wing. I ordered the CA WingWheel from Craggy Aero because the wheel swivels with the direction of travel:
http://www.craggyaero.com/ground_handling.htm
And the length is adjustable which helps greatly for storage. It is also has a spring shock absorber that the Cobra wheel does not have. I tried it out today and towed my ASH31Mi (with the 21M tips) around the Richland, WA airport (KRLD). The wing wheel worked great and put no stress on the wing. The Cobra wing wheel would bend inwards as the tire was dragged sideways in a turn - the CA wing wheel tracked perfectly and was always in a vertical position. The height of wheel was more than adequate to keep the wing tip above obstructions (taxiway markers and signs). This version also has improved straps over the earlier design. Fabrication of all components is excellent - no thin walled aluminum tubing, for example. The tire is not pneumatic, so it can't go flat. It is wide enough so it will not drop into pavement cracks. It is well worth the additional cost over the Cobra wing wheel - I was always holding my breath when I used it.

Tom

The best wheel I have had is the one from MM Fabrication. Very sturdy, well fitting and does not stress ailerons.

That wheel does not swivel, so it will suffer from the same scrubbing problem that the Cobra wheel has.

Not true, the other wheels have scrubbing problems because they are flimsy and they fit poorly. I tow on concrete all the time, never have had a problem. I had all kinds of wheels before and they were all terrible, especially on concrete. I had the same concern as you before I bought the MM Fabrication wheel and I asked Mark to modify the wheel to include swivel. He said to try it they way he makes it and it works perfectly. He uses precise wing airfoil to manufacture the wheel, so each wheel fits only one glider type.. This is why it sits on the wing perfectly and it does not move at all. I am a very happy customer!

While the clamping of the Mark's wing wheel is better than Cobra's, scrubbing is inevitable because of the geometry of towing. I actually tried to buy Mark's wing wheel and even mailed him a check after he complained about others cancelling orders, but he still didn't want to make it. The CA wing wheel works better, is adjustable, has a shock absorber, is well made and is cheaper. And it was in stock.

Tom

Not exactly true. Tom inquired about a wing wheel, wing cuffs and a tow bar.. I explained that tow bars were out of stock and wing wheels and wing cuffs are custom fabricated. Because of my involvement in another project, I informed him that delivery times were questionable, if at all possible. I don't recall receiving a check at all.

As far as "scrubbing" being "inevitable," also not true. Over 300 of my wing wheels are out there, and if properly positioned and aligned with the direction of travel, they track well.

But you can't convince Tom, since he is always right.

On Friday, May 1, 2020 at 10:36:38 AM UTC-7, wrote:
Not exactly true. Tom inquired about a wing wheel, wing cuffs and a tow bar. I explained that tow bars were out of stock and wing wheels and wing cuffs are custom fabricated. Because of my involvement in another project, I informed him that delivery times were questionable, if at all possible. I don't recall receiving a check at all.

As far as "scrubbing" being "inevitable," also not true. Over 300 of my wing wheels are out there, and if properly positioned and aligned with the direction of travel, they track well.

But you can't convince Tom, since he is always right.

Come on, Mark. I sent you the check - I've got a copy of it - along with a purchase order, which I also have a copy of. You said you could make more money on another project. I said, "Ok, then shred the check and forget it, no hard feelings."

Scrubbing is what happens when you turn a tire on a radius. I have seen it happen with my Cobra wing wheel. If the wing is long enough and the turning radius tight enough, you get to the limit where the wing wheel is at the exact center of the turn and is being turned around a point. This scrubbing pushes the wing wheel sideways and is very obvious with the Cobra wing wheel. It's not me that's right, it's physics that's right.

Tom

But you can't convince Tom, since he is always right.[/i][/color]

Come on, Mark. I sent you the check - I've got a copy of it - along with a purchase order, which I also have a copy of. You said you could make more money on another project. I said, "Ok, then shred the check and forget it, no hard feelings."

Scrubbing is what happens when you turn a tire on a radius. I have seen it happen with my Cobra wing wheel. If the wing is long enough and the turning radius tight enough, you get to the limit where the wing wheel is at the exact center of the turn and is being turned around a point. This scrubbing pushes the wing wheel sideways and is very obvious with the Cobra wing wheel. It's not me that's right, it's physics that's right.

Tom[/quote]


Go back to school Tom.

Go back to school Tom.

Brett- Don't bother. Tom installed diodes on his brain. All TX, no RX

I am a convert to the swivelling wing wheel - for me the IMI one which is beautifully designed and has a decent sized wheel unlike some others.

There are 2 factors that can make any fixed wheel twist or rock. Firstly the tight turn or on the spot rotation when if the wheel is not precisely longitudinally aligned it will twist badly. Secondly, if the wheel is not absolutely vertical then there is a castoring effect as you tow straight. This pulls the wheel in or out. On rough ground with unballasted wings it can self-correct with each bounce of the wing and wobble along. When ballasted, especially on smooth grippy hard surfaces, the cuff can't twisted sufficiently to dent the wing skin or damage a control surface - both of which I have had over the years with three different wing dolly designs on three different gliders.

A broad rigid custom fitted cuff masks the underlying concept flaw but a good swivelling wheel eliminates it. The worst designs have heavy legs, a fixed wheels, and a generic cuffs with spongy padding.

On Friday, May 1, 2020 at 8:47:48 PM UTC-7, 2G wrote:
On Friday, May 1, 2020 at 10:36:38 AM UTC-7, wrote:
Not exactly true. Tom inquired about a wing wheel, wing cuffs and a tow bar. I explained that tow bars were out of stock and wing wheels and wing cuffs are custom fabricated. Because of my involvement in another project, I informed him that delivery times were questionable, if at all possible. I don't recall receiving a check at all.

As far as "scrubbing" being "inevitable," also not true. Over 300 of my wing wheels are out there, and if properly positioned and aligned with the direction of travel, they track well.

But you can't convince Tom, since he is always right.

Come on, Mark. I sent you the check - I've got a copy of it - along with a purchase order, which I also have a copy of. You said you could make more money on another project. I said, "Ok, then shred the check and forget it, no hard feelings."

Scrubbing is what happens when you turn a tire on a radius. I have seen it happen with my Cobra wing wheel. If the wing is long enough and the turning radius tight enough, you get to the limit where the wing wheel is at the exact center of the turn and is being turned around a point. This scrubbing pushes the wing wheel sideways and is very obvious with the Cobra wing wheel. It's not me that's right, it's physics that's right.

Tom

If the wing wheel is biased forward, so that it is inline with the main gear axle, there will be no scrubbing as the geometry is correct for any radius turn. The further behind the main gear the wing wheel is, the larger the problem. My complaint on the Cobra was the wheel was too small for rough ground, so I fitted a much larger one. It seems like the Craggy wheel is much smaller still. Probably works well on pavement.

Scrubbing is what happens when you turn a tire on a radius.

If the wing wheel is biased forward, so that it is inline with the main gear axle, there will be no scrubbing as the geometry is correct for any radius turn.

Ignoring who said and did what, I just learned a useful geometry lesson.

Assuming 'scrubbing' is when the rubber on a tire rubs instead of rolls over the pavement.

Another symptom is 'hopping' where the wheel tracks wrong and rolls out of position flexing the mount. Eventually, there is enough force from the flex to make the wheel hop back into position. Definitely some 'scrubbing' involved as well. Definitely a worrying situation because the flex is putting weird loads on the flying parts.

If the wing wheel is vertical and in line with the line of travel, why would there be scrubbing when you are going straight?

If in addition, the axle of the wing wheel points to a line directly above the main wheel, why would there be scrubbing when the glider makes a turn?

Maybe in the limit, neither one of these can be aligned perfectly, but if you put the wing wheel in the right place it ought to work pretty good.

That explains why my old wing wheel still hopped on curves even after I adjusted it so it points straight ahead. Also why the new MM one doesn't.

Guess a swivel might be another out of the hole, but not the only way.