Incorporating the vex ball shifter into a WCD Drive

[JB]

Originally Posted by AdamHeard

The CAD is very clear here. The plate is flush, the bolts go through the tube, through the plate, into the tapped standoff.

We remove the bearing block faceplate, remove the two 1/4-20 buttonhead, and the gearbox is removed. Identical in function to our current designs. We consider the bearing block an integral part of the gearbox.

None of this is untested, all we did was make the ballshifter the same black box more or less as our current designs.

What are the gears that you are using in the third stage, standard IFI ones? One of the possible issue's I noticed with IFI's third stage is that it sits below the bottom of the plastic housing from the previous two stages, causing an issue if you want to mount the housing to the bottom of a robot with very little clearance. I was thinking about changing up the gear ratio and was wondering if that is what you did.

[MichaelBick]

Originally Posted by David Doerr

Are you looking at using belts or are you thinking strictly chain-drive?

I don't want to answer for 973, but sometimes it can be very hard to get belts out of a WCD. In some games you may have to use an inner member(s), preventing some of the belts from being taken out. However you could still run belts if you run no inner member or putting the member over the side rails(both things that 973 likes to do).

[Brian Selle]

Originally Posted by jb1403

What are the gears that you are using in the third stage, standard IFI ones? One of the possible issue's I noticed with IFI's third stage is that it sits below the bottom of the plastic housing from the previous two stages, causing an issue if you want to mount the housing to the bottom of a robot with very little clearance. I was thinking about changing up the gear ratio and was wondering if that is what you did.

In the CAD file he is using 34/50 for the 3rd stage. With 4" wheels this gives a theoretical 7.6/17.2 fps. If you drop down to the next IFI option of 24/60 that gives you 4.5/10.1 fps. It'd be nice to have something in between... like 30/54 which gives 6.2/14.1 fps except IFI does not have a 54T gear. It shouldn't be too hard to find a 54T gear from another source.

Having the gear hanging below the bottom of the frame shouldn't be an issue for traversing perpendicular bumps as the gear is concentric with the wheel. Parallel "ruts" might be an issue... regardless wouldn't be a bad idea to extend the mounting plates and create a guard. I really like the low CG of this design.

[scottandme]

Originally Posted by jb1403

What are the gears that you are using in the third stage, standard IFI ones? One of the possible issue's I noticed with IFI's third stage is that it sits below the bottom of the plastic housing from the previous two stages, causing an issue if you want to mount the housing to the bottom of a robot with very little clearance. I was thinking about changing up the gear ratio and was wondering if that is what you did.

Edit: above poster beat me to the punch

Look at the part names in the CAD - it's a 34:50 3rd stage. The stock 3rd stage is 24:60. The stock ratio is probably a touch slow for 4" wheels (80% speed loss gives 3.6 and 8.1 ft/s). The 34:50 reduction yields 6.1 and 13.8 ft/s. I don't know why they don't list that possibility on the ballshifter page, but any combination of gears that add to 84 teeth would work. 40:44, 34:50, 24:60 and 20:64 are the only possibilities using vex gears.

You can always cut out your belly plate to accommodate the 60T gear, it will be within the OD of the wheel regardless, so short of sliding perfectly sideways off of a ledge, it's unlikely to contact anything.

The mount Adam posted might interfere a 60T gear, depending on the OD of the standoff some modification of geometry would be necessary.

[AdamHeard]

The ratio is 34:50, which is a number we're pretty happy with.

A 60T gear just barely kisses the existing standoffs, we would likely just neck them down in that scenario. Ideally, we never have a reason to deviate from smaller wheels and this isn't necessary.

Originally Posted by David Doerr

Are you looking at using belts or are you thinking strictly chain-drive?

We haven't made any really firm decisions there, chain is certainly less work.

[arun4444]

Quick question,

for the pancake cylinder, how are you guys wiring it? Total noob at pneumatics, so what pressure, and how to actuate. Just asking before purchasing.

cheers