Gear shift linkage

[woohoo]

HI!
In the days of old, when the gear shifting was done manually, how did the gear shifting mechanism work ?
How did the actual movement of the lever end up in the gearbox ?

I can imagine a rod connecting the two, but still, how did it work...

[MattF1]

Hi, this page should give some basic background info on a manual gear linkage.

http://auto.howstuffworks.com/transmission3.htm

[woohoo]

I know how that works
The thing is, how is the actual link made between the driver's handle, and the gear box.

The gear box is behind the engine, and the engine behind the driver, yet the gear handle is on the right side of the driver.
I have seen a few photographs where the link looks like flexible pipe, or tube in which, I can imagine, a rod runs.
how does THAT work ?

[MattF1]

Think it was probably some cables, one to pull - one to push.

[scarbs]

The old gearbox linkages were extremely simple, but they did create a lot of packaging problems, which in part lead to Barnards introduction of the semi automatic transmission.

The gear lever was a simple lever pivoting on a spherical bearing operating the main linkage. This is effectively a long rod that extends from the lever back to the selector mechanism at the back of the gearbox (in the old days the gears were behind the differential, only later did they bring the cluster inboard). The long rod was a single tube that passed the forward\backward and rotary motion of the gearlever. It passed inside the cockpit under the drivers arm, through the fuel tank area and exited through the rear bulkhead and passed alongside the engine, through the rear suspension to meet the gearbox.

Scarbs...

[woohoo]

I understand as much, but the pipe in the tube, if it is flexible, how can it convey the rotary motion ?
I would assume that if it is flexible, the torque would "disappear" on the other end.
Are there any videos / pictures on the internet ?

[safeaschuck]

O.K. here goes, something I might be able to answer correctly let down only by my poor description.
Single clutch sequential gearboxes have a barrel which is used to move the selector forks which engage the gears. The barrel can be slightly bigger than a smartie tube up to the size of a baton (like the relay runners use), The barrel runs parellel to the gears and has grooves around the circumference, one groove for each selector fork.
The the tip of the fork sits in this groove. (on a dinner fork this would be the bit where your hand goes)
Selector forks each engage one of two gears (so one fork for 1st & 2nd one for 3rd and 4th etc.) the groove is a straight track exept for an S shape at one point which moves the selector fork right and then left to engage each gear in turn (the S is at a diferent place on each track so the gears don't all engage at the same time).
At the end of the barrel is a ratchet which operates in both directions and means that the barrel need only be turned 1/6th or 1/8th of a turn for instance (depending on number of gears) clock or anti-clock. this is acheived by a lever on the outside of the gearbox. After this rotation the barrel remains in place while the lever which turns it snaps back to the start position. This lever can then be joined to the gear lever or paddles via a tube, cables, solenoids and wires, pneumatics or by a stale baguette and some self tapping screws.
Hows that? Is that what you meant?

[riff_raff]

safeaschuck is correct. The later versions of racing gearboxes were "sequentials" that only required the gear lever to be moved forward or backward. The gear lever was connected to a push/pull rod that indexed a grooved drum in the transmission (just like a motorcycle transmission). The grooved drum converted the angular rotary movement into an axial movement that shuffled shift forks back and forth. The shift forks in turn engaged/disengaged the dog rings in the proper sequence for each gear ratio.

Older versions of racing gearboxes use a combination of rotation and translation by the push/pull rod to engage multiple shift levers; usually one lever for each pair of gears. Thus the "H" pattern movement required by the shift lever.

A big problem with most stressed, mid-engined race chassis is that the shifter push/pull rod linkage usually ends up passing just under the exhaust header as it goes back to the rear mounted transaxle. Inevitably, during a long race it gets hot, expands in length, and causes problems shifting the transmission.

[scarbs]

The older H gate gear selectors, were steel or Alu tubes, they were able to reach the gearbox via universal joints as in steering columns. in a good design they only needed two, one behind the rear bulkhead and one near the geabrox casing.