Wing wheel from Craggy Aero

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

On Saturday, May 2, 2020 at 5:54:05 AM UTC-7, wrote:
Go back to school Tom.

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

I have had one each of MM Fabrication products WingRigger, WingWheel, and TowBar for at least 10 years maybe more. They are great! Thanks Mark.

The only problem I have with the CraggyAero Soaring XX Wingwheel is everytime I set one up for my glider a customer buys it and I have to go back to the old standard MM Wingwheel.

Richard
www.craggyaero.com

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.

On Sunday, May 3, 2020 at 6:17:40 AM UTC-7, wrote:

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.

To be correct geometry for a specific radius turn, the wing axle must point towards center of the turn radius. The axle lines of the main and wing wheel intersect at this center. If the main wheel is the center, then the wing axle must point towards it. A swiveling wheel will align itself to this geometry. For a non swiveling wheel to be correct geometry for *any* radius, the axles have to be in line (more specifically their projection to the ground plane has to be on a line), guaranteeing that both axle lines intersect at the circle center regardless of radius. The wing wheel will then not scrub, even if it is the center of the turn. It will turn about its vertical axis, just as the main gear (or indeed the swiveling wheel) must, in other circumstances. That is not "scrubbing" as the term is usually applied.

And now, back to the popcorn....

On Sunday, May 3, 2020 at 4:48:52 PM UTC+1, jfitch wrote:
On Sunday, May 3, 2020 at 6:17:40 AM UTC-7, wrote:

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.

To be correct geometry for a specific radius turn, the wing axle must point towards center of the turn radius. The axle lines of the main and wing wheel intersect at this center. If the main wheel is the center, then the wing axle must point towards it. A swiveling wheel will align itself to this geometry. For a non swiveling wheel to be correct geometry for *any* radius, the axles have to be in line (more specifically their projection to the ground plane has to be on a line), guaranteeing that both axle lines intersect at the circle center regardless of radius. The wing wheel will then not scrub, even if it is the center of the turn. It will turn about its vertical axis, just as the main gear (or indeed the swiveling wheel) must, in other circumstances. That is not "scrubbing" as the term is usually applied.

And now, back to the popcorn....

That is true assuming that the leg of the dolly is vertical and a non-vertical leg would make a negligible difference on a single tight turn. However with a noticeably non-vertical leg and a fixed wheel (e.g. and in my case, on the dihedraled outer part of a D2C or V3 wing) then on a straight tow, no matter how accurately the cuff is alinged, the wheel will tend to turn itself (like how you lean to turn a bike). It will then either relieve itself by bouncing, or by skidding back to position, or it will twist the dolly until you stop and go and sort it - depending on the surface and the weight on the dolly from ballast.

On Sunday, May 3, 2020 at 9:54:13 AM UTC-7, wrote:
On Sunday, May 3, 2020 at 4:48:52 PM UTC+1, jfitch wrote:
On Sunday, May 3, 2020 at 6:17:40 AM UTC-7, wrote:

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.