Ok the discussion has been talked about in the advanced gear thread. But lets get more specific.
The defferential is an open differential.
Open Differential
When one tire slips 100% of the torque goes to the slipping wheel.
Limited-Slip Differential (LSD)
When one tire slips a series of clutches and springs transfers 30 to 60% of the torque to the non slipping wheel. ( commonly found on cars )
Locking Differential
When one tire slips a series of clutches springs and gears transfers 100% of the torque to BOTH wheels. ( typically found on 4x4’s ) This also does not allow any wheels to freewheel while turning. ( Live axel ).
There are many advantages and disadvantages of these types of systems. What I would like to do is open up a discussion on how one could modify an open differential system to be one of the other two types.
There are times when the bots will traverse uneven ground and since there is no suspension as of yet for vex that means zero chassis flex. unless you forgot to tighten your bolts up, or have a weak frame. What are you doing to overcome the issues that arise when your wheels slip?
Now There is a link in the advanced gear topic that shows how someone modified a lego open differential. Well lego does not handle torque like vex does. so the lsd that idea demostrates will not work. For those of you that have not seen it it’s the left and right side connected to a common shaft with strong rubberbands. which allows for slippage. This is a great idea and works well for low torque operations.
http://home.online.no/~selode/lego/limited.html
I have built a system that when activated will become automatic locking. It’s very crude needs refining and better design work. Each output shaft uses a chain to tuen an auxulary shaft. one of the shafts is movable, as in able to slide in and out. It has 2 springs on it to keep it in open position. and when needed a servo could slide the shaft and push it into the other shaft. ( will post a pic of it in the morning ) Though it is not powered yet it is very effective under hand power. ( tangent… got another idea already to help lock the two shafts use a clutch… )
Eventually after it becomes more refined I would like to see a program that reads 2 optical shaft encoders on the aux shafts. and when one is no longer turning it will auto engage the locking mechanism for a durration of say… 5 seconds that would be enough time to get across the problem area i feel. if not it would engage again when it “sensed” that only 1 wheel was turning.
Anyway, Lets brainstorm. toss around ideas on what you think that will work. There is no wrong questions. If there is something you don’t understand ask. I’m betting that the Vex community can make this into a more valuable asset than what it already is.
Good luck.
dee
