pic: Don't do this. It's a bad idea.

[Borisdamole]

Originally Posted by squirrel

There are different ways of doing it, the Corvette used Ujoints at both ends of the axle shaft, so it isn't really a swing axle like the early VW. The axle and control arm make a parallel arm setup, so the camber doesn't change dramatically like on the early bug

but Corvette is using that strange leaf spring setup....

And this drive train could improve traction by using a sealed diff, and using silicone diff fluid to prevent the module from "diffing out"

A limited slip diff is normally all mechanical, and uses helical gears to prevent "diffing out" (but there are others that operate on clutches or springs)

a traditional limited slip setup would be VERY costly for this size (the gears would be expensive), but silicone would be a great option....

Many small differentials are easily available from any rc car shop or ebay

Cool idea!

[Aren Siekmeier]

Odd how this comes out the day before I return from a week long vacation when I had enough time to think this up in my head. This is exactly what I was envisioning, mechanically anyways: a swerve module that can be pivoted effortlessly due to the differential box.

Several people have explained it already, but I'll take a stab too. You turn the coax shaft as usual and it turns the differential box turning both wheels, like a normal differential drive (this also allows for some interesting turning cases without most of the wheel scrub). Turning the module drives the wheels in opposite directions while the differential box remains stationary. He added the fourth bevel in there just cuz (for strength?), it seems to me, as most differentials operate with only three. Now try flipping one wheel's input to the box (by putting the two perpendicular bevels on the same shaft or any of a number of other things), and now it can translate freely, but must be powered to rotate.... An interesting, though usually useless, prospect.

The universal joint suspension was definitely not something that entered my head. Why you would ever need that, no one knows. Then again, why would you ever need any of this? It's just awesome, that's all.

[Borisdamole]

Originally Posted by compwiztobe

He added the fourth bevel in there just cuz (for strength?), it seems to me, as most differentials operate with only three.

Mechanically 3 will work, but it creates alot of load on the center gear.

Acutually many diffs use 4 center gears(total of 6 gears)
like this

[JesseK]

iirc, this is eerily similar to the front landing gear for planes.

[MrForbes]

Originally Posted by Borisdamole

Acutually many diffs use 4 center gears(total of 6 gears)

Most of the automotive differentials I've seen use two "spider" gears, for a total of 4 gears. The only common exception is the heavy duty Ford 9" rear from the 1970s-80s. But I haven't worked on many late models either!

[Chris is me]

Originally Posted by JesseK

iirc, this is eerily similar to the front landing gear for planes.

The suspension is definitely similar, but I thought the landing gear for planes were unpowered casters? I'm no expert by any means, though.

[Ian Curtis]

Originally Posted by Chris is me

The suspension is definitely similar, but I thought the landing gear for planes were unpowered casters? I'm no expert by any means, though.

No, the nose gear is actuated for taxiing. The rudder is very ineffective at low speeds. Think about it, would flapping the rudder around give you a whole lot of moment when you are sitting on the ramp? Some very old planes have a tail skid in place of a nose wheel, and occasionally this isn't actuated (but it makes ground handling a royal pain).

[Garret]

I may be wrong, but I don't think that this will even offer the right type of suspension. From the picture it looks like there is only one universal joint on each side, meaning that the wheel can only rotate up and down, not just move up straight up and down as in a more traditional suspension. I would think that there would need to be at least 2 universal joints on each side in order to allow it to move up and down. However I do like the idea a lot.

[Tristan Lall]

Originally Posted by Ian Curtis

No, the nose gear is actuated for taxiing. The rudder is very ineffective at low speeds. Think about it, would flapping the rudder around give you a whole lot of moment when you are sitting on the ramp? Some very old planes have a tail skid in place of a nose wheel, and occasionally this isn't actuated (but it makes ground handling a royal pain).

On most aircraft using tricycle gear, the nose wheel is unpowered, unbraked and mechanically or hydraulically steered.

There are numerous exceptions, however. Some early Boeing 727s had nose gear brakes, but they were omitted on later aircraft (and often removed on early ones) because the added braking capacity was of little use compared to the weight penalty (something like a hundred pounds). There was an aftermarket kit being evaluated by Air Canada on one of their Boeing 767s which added an electric motor to the nosewheel for taxiing. While saving wear and tear on the main engines was a good idea (I believe it could run on the APU's generator), again, it weighed too much, and there was concern it could lead to higher maintenance costs for the nose gear assembly. On a few small aircraft (Diamond's DA20, for example), the nose wheel is freely castering. Steering is accomplished with the toe brakes controlling the main wheels (differential braking), and the rudder pedals at higher speeds.

Incidentally, the suspension on the nosewheel of most aircraft is not located beside the wheel like that—it's usually in the strut. (Gas-over-oil is common.)

[PAR_WIG1350]

Originally Posted by Tristan Lall

On most aircraft using tricycle gear, the nose wheel is unpowered, unbraked and mechanically or hydraulically steered.

There are numerous exceptions, however. Some early Boeing 727s had nose gear brakes, but they were omitted on later aircraft (and often removed on early ones) because the added braking capacity was of little use compared to the weight penalty (something like a hundred pounds). There was an aftermarket kit being evaluated by Air Canada on one of their Boeing 767s which added an electric motor to the nosewheel for taxiing. While saving wear and tear on the main engines was a good idea (I believe it could run on the APU's generator), again, it weighed too much, and there was concern it could lead to higher maintenance costs for the nose gear assembly. On a few small aircraft (Diamond's DA20, for example), the nose wheel is freely castering. Steering is accomplished with the toe brakes controlling the main wheels (differential braking), and the rudder pedals at higher speeds.

Incidentally, the suspension on the nosewheel of most aircraft is not located beside the wheel like that—it's usually in the strut. (Gas-over-oil is common.)

Another exception would be the Boeing B-52 Stratofortress Which has a quadracycle undercarriage and 4-'module' crab steering to facilitate landing the behemoth of an aircraft in high crosswinds conditions. Most aircraft have to approach flying sideways and straighten out after they land to roll down the runway instead of off it, the B-52 simply rolls sideways .

[Tristan Lall]

Originally Posted by PAR_WIG1350

Another exception would be the Boeing B-52 Stratofortress Which has a quadracycle undercarriage and 4-'module' crab steering to facilitate landing the behemoth of an aircraft in high crosswinds conditions. Most aircraft have to approach flying sideways and straighten out after they land to roll down the runway instead of off it, the B-52 simply rolls sideways .

To be fair, the B-52 only has ±20° of strafing ability.

Actually, the reason for those steerable gear is the use of ridiculously-small control surfaces on the B-52. The engineers designing it in the late 1940s were not confident in the reliability of early hydraulic flight controls, and therefore adopted all sorts of unusual compromises. Instead of using a large hydraulic rudder to control the plane in a crosswind, they just added steerable gear, and stuck with a very narrow (though still about 20 ft tall) spring-tab-assisted rudder.

It seems to have worked, because the early-1960s-built B-52Hs are likely to be in service for at least 30 more years....