Reversing gearbox

[chlang]

I'm building a swinging ship to go with my amusement park.  I'm trying to drive the thing with a large rubber tire underneath it, but I'm out of my depth when it comes to gears.  I need the wheel to spin clockwise for a few seconds and then switch to counter-clockwise.  I have tried using a power functions switch, but without enough momentum to flip it, it always gets stuck in the middle off position.  I tried using the remote and the IR sensor and manually controlling it, but I'm running my PF motors off of the old 9V train controllers, and there isn't enough power that way to run the IR sensor.  I don't want to go with batteries.  I wish there was a wall power option for the PF product line, but there isn't.  So now I'm trying to create a gearbox that periodically reverses direction, but everything I've tried is close, but not quite there.  Does anyone have the know how to create a gearbox that reversed the output direction every 2-4 seconds?

[Carsten Svendsen]

On the top of the ride, connected to the ship it self, run a 90 degree gearing with axles running down it, into a gearbox. This gearbox is a one way to two way converter, easily done with a differential. Between those two outputs, put your PF switch.

On your tyre that is operating the ship, put a differential between it and the motor like you normally use it. Have the other output of the differential go to a counter weight (think heavy wheel) or some other form of heavy resistance, so that the tyre will always go a little faster than the ship, making it speed up.

For speeding down, you could replace the heavy counter weight with a lighter one, essentially moving the energy created from the ship to the weight.

[kolbjha]

I don't know if it gives enough torque, but what about making a rocking mechanism, where a smaller rotating wheel/crank is rocking a bigger wheel (with rubber tyre?) using a link? Perhaps this also gives a more realistic rolling of your ship also?

[suffocation]

Can you post a picture of the base? Just to get an idea of how much room there is for the reversing mechanism.

[Snorrowitz]

Maybe you can get some inspiration from the system JKBrickworks demonstrates in this video:

 

[Limga]

Oddly Youtube put this in my recommendation:) I guess this is something you need. You can adjust the period by length of the links. 

 

[chlang]

Thanks guys - I think Snorrowitz's suggestion of the JKBrickworks method is going to do exactly what I need with about the right timing too.  If I get it working I'll post pictures but the show I'm building for is in 2 days.