Gearbox question

[dbostream]

I want to create a gearbox with the following properties:

Forward gear: Only allow forward movement

Neutral: Allow movement in both directions

Reverse gear: Only allow backward movement

Is this possible? I cannot figure out a way to restrict axle movement to one direction only when not in neutral.

There is not gonna be an electrical motor involved in my car.

EDIT: I have found a way that kind of works, to have a brick get stuck between two teeth on a gear at a certain angle. The positive thing is it locks in one direction but the bad part is that the direction that doesn't get locked makes some noise. Any ideas are welcome.

Edited May 19, 2011 by dbostream

[T_Tank]

Well in normal twin countershaft truck transmissions there are no parts inside them to keep the gears from turning the wrong way if the engine starts spinning in reverse.(This happened at my school had a run away diesel after the key was turned off an it started running backwards, the instructor had to hop into the truck an put it in reverse with the parking brake engaged so it would cut the engine out)

[Ape Fight]

I want to create a gearbox with the following properties:

Forward gear: Only allow forward movement

Neutral: Allow movement in both directions

Reverse gear: Only allow backward movement

EDIT: I have found a way that kind of works, to have a brick get stuck between two teeth on a gear at a certain angle. The positive thing is it locks in one direction but the bad part is that the direction that doesn't get locked makes some noise. Any ideas are welcome.

I think you might be eluding to this in your above edit, but a toothed 1x4 brick (like those used on old steering racks) held with a loose grey pin over a gear wheel does the trick. When the gear turns the wrong way the toothed brick locks it. All you need to do is add a gear and the toothed brick to the input shaft - you can even have it built onto the engine so the engine makes a noise as it turns : )

I think I've made the most compact gearbox with forward, neutral and reverse, which can be found here: http://www.mocpages.com/moc.php/77288.

[allanp]

Ok, i've come up with these for you. The first is probably the simplest way of doing it:

However if you want the non-reversing feature to be silent then you may want to experiment with something like this:

I can't say how successful the silent version will be without building it but I hope it at least gives you some ideas to work from.

[dbostream]

Thank you Ape Fight and allanp.

My current attempt looks similar to your first solution allanp, unfortunately I don't have the parts to try your silent one.

Edited May 19, 2011 by dbostream

[AndyC]

One option would be to take advantage of the way a worm gear will slide along an axle depending on the direction it's turning in. That should allow you to disengage an output that's turning the 'wrong' way.