A bit of gear fun,

[DesertRunner]

THis is a 2 directionial gear, "I think & I hope".  Have this gear change idea on a car gear box and I want to drive the gear in 2 direction from 2 seperate gears.  This gear is on the end of a gear change shaft on a car gear box and the two smaller gears are driven from electric motors so they select the disered gear in the "H' pattern.
What do you guys think and how do we cut it?  The pdf is 3D so double click and you can look closer.
Tony

[JustinO]

Is this in the power train, or just in the control linkage?

Machining is easy, you would cut a pair a involute spur gears (purple and blue), and a rack and pinion (blue and red), the rack being cylindrical.  Problem is, the pinion will be pushing on the gaps between the blue rack/gear's teeth half the time. Pushing on nothing is usually a problem, but stranger things are done, especially when "gear fun" is evoked. Separating the two functions of the blue gear into two elements would simplify things, perhaps.

Is the goal rotating a shaft around its axis, and also translating it along it's axis?

If you have a shaft with two helical thread patterns, one left handed, one right handed (like a Yankee screwdriver), and two driving gears, one for each pattern, all three parallel shafted, then when the two driving gears are going in the same direction at the same speed, the shaft would rotate only, and when they are going in opposite directions at the same speed, the shaft would translate only, along its axis in proportion to the difference. It would be a differential, but instead of two rotary inputs, and one rotary output, there would be two rotary inputs, a rotary output, and a linear output. R ~ (r1+r2)/2 and T ~ r1-r2, or something like that. It's the wrong time of the day here in the northern hemisphere for these thoughts.

[DesertRunner]

Its the gear change control linkage.

Moving forward and back is 3 positions centre position is N forward is 1, 3, 5, & back from N is 2, 4, 6, R.

Rotating the shaft will give 6 positions.
Each of the drive gears only move when the other is in position.

Tony

[JustinO]

If the gears are not rotating 360, you might consider using partial gear "sectors", or even just using linkages.

My telescope drive uses a 360 degree worm wheel to rotate the telescope slowly with the stars, but it uses "sector arms" for the finer faster tracking motions. These sector arms have only about five degrees of range, and are a screw mechanism, rather than a gear mechanism.

What kind of motors are you thinking of for actuating this? A gear head servo?

[DesertRunner]

Hi Justin,
It has to be cheap, so I was think of a couple 12V planetary gearboxs doing about 12rpm.  If the change is to fast it will smash the sycrono rings,
Your suggestion is interesting.
Tony