Tilting bogies

[MkVIII]

Another one of my whimsical "Why is it so" questions. Bogies, the type with wheels attached (not unidentifed aircraft or snot).

Is there any advantage per se in which direction the bogies tilt - some manufacturers have the leading wheel set tilted down, whilst other manufacturer's prefer the rearward wheel set tilted down.

To me, it seems "more natural" for the later - downward rear set - as forward down tilted ones seem to be harder to "grease on", and would appear to suffer more landing stress as there is bound to be SOME rearward torsional forces (whereas the rearward torsional force on a rear tilting bogie would not be transmitted directly through the bogie structure).

Just wondering...

[Notso Fantastic]

From a previous discussion, it would appear the main parameter of bogie design and appearance (apart from keeping up to 300 tonnes of aeroplane away from very hard runway) is simply undercarriage bay layout and stowing one within the other. I thought there was some deep secret in it (bogies forward or backwards), but engineering efficiency and simplification seem to be the main factors.

[MkVIII]

Yep, that's what I surmised as well.

Although, certain manufacturer's seem predisposed one way or the other :p

Always find it interesting in A340's with the extra centreline unit (same with the DC-10 most likely) - nice landing, then THUNK as the centre touches and compresses. A nice landing is NEVER over till ALL wheels are on terra firma (or terror BLOODY firma for some landings!)

[Snigs]

The reasons are as stated above.

If you look at the A340 -600, the wing landing gear pitch trimmer trims the gear for rear wheel touch down first, but the centreline gear is trimmed to touch front wheel first. If you look along the alignment of the gear the wheels that touch first are almost in line, for obvious reasons.

[fruitloop]

Comparing the 757 with the 767 ??

[Virginia Plane]

Snigs - the reason the center gear tilts the other way on an A340-500/600 is to allow the doors the neccessary space to swing open and closed without fouling on the forward 2 wheels.

[gas path]

And then just to complicate it along came the L1011 with truck levelling cylinders for the self same reason.;)