SP3 feature: Gears.

CPhillips

Gears allow you to synchronize objects that are connected to gears. You make a gear by connecting jointed objects together using the Joint Connection Tool (JCT). NOTE: It is important that you make gears exactly right or they wont work.

[flash=648,480:1iyblcg0]http://youtube.com/v/YGZp9SEfTeo[/flash:1iyblcg0]

Here is how to make a simple gear:
-Create a floor
-Use the wheel tool to create a wheel that is connected to the floor.
-Create a second wheel the same way.
-Select the JCT and click on the hinge joint in one of the two wheels.
-Press CTRL and click on the hinge in the other wheel.

If you do it right you will see a message box asking if you want to create a gear. Say "yes". Now press play and when you rotate one of the wheels the other will turn.

If you look in the UI of a joint with a gear you can set the gear ratio.

There are 3 types of gear. Gear (two wheels), Pulley (two lifts) and Wormgear (one wheel and one lift).

Issues:
-Gears are very particular about the type of object they connect. That is why I suggest you start with Wheel, Door and Lift because they are the right type of object; A group with a single joint connected to an external object.
-When connecting wormgears you must select the hinge first and connect to the slider
-Large numbers dont work for a gear ratio(I have no idea why)
-Gears on top of gears dont work (I have no idea why).
-Gears can and will slip. Nothing can be done about it.

Gear1.skp

Wacov

Here's a half-finished differential that doesn't work... I think I understand why, but will this kind of setup work in a future release?
diff.skp

CPhillips

@wacov said:

Here's a half-finished differential that doesn't work... I think I understand why, but will this kind of setup work in a future release?
[attachment=0:17xt3zr9]diff.skp[/attachment:17xt3zr9]

I confess I don't know exactly what a differential is, so I cant tell exactly what is wrong with this model. How is it failing?

Wacov

Well, I didn't know until recently... it distributes power to the drive wheels, while allowing one to spin faster than the other whilst turning. Most handling problems with SP cars could be fixed with a diff. The box that the gears are housed in should rotate on the axis of the (so-far) unused motor joint, moving the middle gear with it. In real life, this would turn the side gears and so transmit the power, but with the way gears work in SP, this doesn't happen.

CPhillips

Again, I don't know how the gears work in a real diff but this is working about how I would expect. I put it on a pedestal so the wheels could turn and if I turn one wheel the gears turn and the other wheel also rotates. If you want the wheels to turn in the same direction rotate one of the wheel hubs 180 degrees.

Wacov

I didn't explain it properly... this model shows what the diff is meant for, and (hopefully) what it isn't doing.

diff.skp

CPhillips

I thinkI see. Try adding a gear connection between the motor and the central wheel hinge.

diff-3.skp

shareck

this is wrong. the big wheels should turn when the middle gear isn't spinnig but its moving together with the motor joint (turning arond the wheels axis).

Wacov

In order for the diff to work, sketchyphysics would have to allow this example to work as if the gears were meshed.

Gear problem.skp

Wacov

Actually, I think I've worked out a way that would work if gears could work in reverse... so if the object the gear was connected to was moved while the gear stayed still, the gear would still work.