A question about ME 109 landing gear...

[muddyboots]

Why didn't they just add some shims between teh tire and the mount, sort of extand it an inch or so, and cut the wheel well a little more? Wouldn't that two inches have made a little difference? Or too little difference?

[Augsburgeagle]

Not entirely sure what you are getting at but tyre sizes and wheel well size was increased through-out the war. Well size going from a small bulge on the top of the wing right through to a nearly wing chord length fairing for the 660x190 tyres

[muddyboots]

I'm thinking a once inch or two inch lng extension to how far out from the landing gear main strut. THis would widen the width of the landing gear, and help stabilize the plane. I'm pretty sure it's a dumb idea or German engineers would have done it. I'm mostly asking why they didn't? Was it too much stress on those extension, or would they have made it tough to get the gear IN the wheel well? or both

[Augsburgeagle]

The G10 and K-4 did have a different style undercarriage mounting bracket to earlier 109s and the undercarriage width enlarged through-out the war.

[Bill Walker]

Extending the length of the gear leg, or growing the tire size, can be a much bigger change than it appears.

First, you need a bigger hole in the wing, further out, to store the gear when retracted. The wing is full of structure, fuel tanks, armament, control linkages, etc. Moving or enlarging the hole is a big undertaking. It is very easy to do when I trim the plastic on my models, but much harder to do on a real airplane .

Second, changing the location of the tire tire contact point on the ground changes the loads the tire transmits to the airplane. Generally, a bigger tire or a tire further out will produce bigger loads. Now you need a bigger strut (and a bigger hole where the strut goes) plus bigger attachment structure at the top of the strut, plus bigger retraction mechanisms, and bigger attachments for the retraction mechanisms. As an old boss of mine in the design business used to say, there are no small changes.

All aircraft design (or any complicated machinery design) is a compromise. The Bf 109 and the Spitfire designers gained some things with their choice of landing gear style. The attachment points are further inboard, where the wing is thicker and the structure already beefy. Also, the holes for the wheels are further outboard where the wing is less crowded internally, and needs less strength. Once major decisions like this are made, they are not easy to change.

The Bf109 and the Spitfire gear did grow gradually in width during their design lives, but these changes were usually part of a bigger change, like increased weight and/or power, that needed a major wing re-design anyway.

[muddyboots]

See, I was thinking of making the strut shaped like an L with the bottom of the l benig where the wheel is attached. And when the wheel raises up the covers form a sort of hump similar to the one on the wings of a cannon equiped spitfire. I figured most of the stress would be on that corner of the L, and taht was why theu didn't do it, or that the bump on the wing would have screwed the airoedynamics so much it wasn't worth it. I Do know about the inboard placement saving a lot of weight on the wings, which gave them design bonuses. It seems like our carrier planes also had this design, right?

[MX304]

For all that trouble I'd move near a lake and put it on big widely spaced floats.

[marine air]

Starting even before the Bf-108 Taifun, Willy Messerchmitt had an obsession with building an aircraft as light and efficient as possible. Putting the gear in the fuselage saves a lot of weight in the wings. Think about how beefy a P-51 or F8F wing has to be to support all that weight on landings. A second quality of saving weight in the wings is increased aileron roll rate and effectiveness.
Prior to 1940, most airports were grass and sometimes mud and snow,. Hence the snowplow design of the 109's gear. the wheelwell of the BF-108's and Buchon's that I have looked at have a liner made of canvas or leather and hemmed in with leather bootstrap type lacing. If you stripped that out, maybe there would be a tiny bit more room in the wheel well.
Muddy, I have tried to think of solutions also from time to time. Here are a few tries;
1) Nascar tires are shaven at an angle to give better grip on their angled tracks, why not fit a type of tire that can be shaped so that much more of the rubber actually touches the landing surface than the existing type?
2) the A-4 Skyhawk has small main tires with a tire pressure of 310 psi. What about fitting a high pressure tire and wheel that would be better suited for paved runways and would offer better grip at higher speeds?
3) completely redesign the landing gear so that while retracted , they fit into the wing as original, but when extended they move farther forward so as to put more weight on the tail. This would allow much heavier braking sooner and help get the aircraft stopped on landing sooner. Similar to the design of the Maule M-7, and L-19 birddog. Once you get the airplane into the three point position you can really get on the brakes.
4) Redesign the brakes with disc brakes and with a more precise distribution of braking.

[warbird1]

4) Redesign the brakes with disc brakes and with a more precise distribution of braking.

Did disc brakes even exist when the Me-109 was designed? Anybody know anything about the history of disc brakes on aircraft landing gear, just curious!

[Bill Walker]

Muddy, I have tried to think of solutions also from time to time. Here are a few tries;
1) Nascar tires are shaved at an angle to give better grip on their angled tracks, why not fit a type of tire that can be shaped so that much more of the rubber actually touches the landing surface than the existing type?

The rubber tire will deform until the contact area times the tire pressure equals the weight on that tire. NASCAR shaves tires to generate side forces.

2) the A-4 Skyhawk has small main tires with a tire pressure of 310 psi. What about fitting a high pressure tire and wheel that would be better suited for paved runways and would offer better grip at higher speeds?

310 psi needs really good paved runways, or steel decks.

3) completely redesign the landing gear so that while retracted , they fit into the wing as original, but when extended they move farther forward so as to put more weight on the tail. This would allow much heavier braking sooner and help get the aircraft stopped on landing sooner. Similar to the design of the Maule M-7, and L-19 birddog. Once you get the airplane into the three point position you can really get on the brakes.

Moving the tires forward will effect the takeoff performance. Willy M., in his quest for light weight, would have placed the tire contact point very close to the centre of gravity. Then you only need a small lifting force from the horizontal stab to raise the tail wheel and reduce the drag during the takeoff run. With the wheels further forward, you need a bigger (and heavier and more draggier) h stab, or you settle for a longer takeoff run. The Maule and L-19, by the way, have unusually large h stabs for their size. The loss of a few knots top end, and a few pounds of useful load, was a worthwhile trade off in these cases.

Not trying to rain on any one's parade, just pointing out that there are no small changes.

[Wheels up]

Did disc brakes even exist when the Me-109 was designed? Anybody know anything about the history of disc brakes on aircraft landing gear, just curious!

From this SOURCE

1932 Six-hour day inaugurated to spread the work and alleviate unemployment caused by the Depression....The first hydraulic disc brakes for airplanes developed by Goodyear.

Goodyear multi-disk brakes were standard equipment on 1939 Waco Custom Cabins. A grossly complicated design when viewed from today but likely dramatic improvement over Hayes expander tubes. There certainly was the technology available for inclusion as an improvement. I would hazard a guess that Goodyear was the pioneer in this field in the 30's. But, like all early versions of new innovations...they are so crappy I would choose the Hayes conventional shoe style....but then again...they are not even needed when avoiding hard surface.

The bottom line is...nearly any landing gear arrangement is adequate. Just keep it on grass as they nearly always did. This is akin to any other period aicraft (and those older). Putting them on hard surface is like taking an Erie freighter out to the Atlantic: You might get away with it...but......

If you want to draw out rare and bashful aircraft.....hold a non-public flying event on nice sod 4000' long by 400' wide and wind down the runway. You'd be surprised what would show up.