Incorporating the vex ball shifter into a WCD Drive

[Adam.garcia]

Since I had heard about the new line of vexpro products, it has gotten me thinking about all the ways that teams can incorporate these products into existing proven designs.

Does anybody know the best way for a team to utilize vex pro's ball shifter on a 6 Wheel 254 style West coast drive? I know that this ball shifter gearbox is enclosed, preventing the addition of internal drive sprockets. Are there any other ideas about how to make a cantilevered drop center 6/8 wheel drive?

Thanks, and I can't wait to hear the ingenuity of the chief Delphi community!

[MichaelBick]

973 is planning on going with the ball shifters this year, and adapting them to their WCD. After talking with Adam, he said he might post a paper on what they are doing some time before kickoff.

In the meantime, I've though about changing the 3rd stage. While they have the default output ratios, you could easily adapt their other gears to get a little bit more reasonable direct driving speed. Also, you probably want to make a custom waterjet mounting plate to mount the gearbox too. This will allow you to screw your bearing blocks into this plate, and make an easy, customized adaption to your frame.

On the other hand, I highly reccomend looking at the new WCP gearboxes.http: //wcproducts.net/wcp-00100/. RC said he will release the prices for them soon, and assuming they will compete with the new supershifter prices, it might be worth the extra money for drive gearboxes that is made for running a WCD.

[AdamHeard]

We will post a rough draft of our "Vexpro WCD" before the end of the weekend, and maybe follow up with a more refined setup before ship.

We are also heavily tempted by the WCP gearboxes. They are an iteration of our custom gearbox design, so they'd likely be a good fit into our designs.

[Walter Deitzler]

Wait, is there any reason why a ball-shifter with the right ratios would not work with a WCD?

[Andrew Remmers]

Wait, is there any reason why a ball-shifter with the right ratios would not work with a WCD?

No,

I to want to do some designing with the Ball shifter on a WCD. I should be posting something withing a few days as well.

- Andrew

[Adam.garcia]

Wait, is there any reason why a ball-shifter with the right ratios would not work with a WCD?

The main problem is that there are no internal sprockets inside the gearbox to provide power to the front and back wheels.

[AdamHeard]

The main problem is that there are no internal sprockets inside the gearbox to provide power to the front and back wheels.

This isn't necessarily a problem, be creative. The solution we're posting in a few days isn't innovative or crazy at all.

[billbo911]

Based on calculations with the JVN Design Calculator and input from various sources, I can say without a shadow of a doubt, it will all depend on what you want to achieve.

That said, it looks to me as though a VEXPro Ball Shifter 2 stage will need an extra reduction to get it where you might want it with 4" wheels. Somewhere in the neighborhood of 26:15 or 28:16.

There is a version of the WCP that "should" work for direct drive and 4" wheels.
It is spec'd at 16.4:1 and 6.1:1.

Again, I am NOT an expert on this subject......yet. Please determine your needs and do your own calculations before you make a decision.

[Walter Deitzler]

The main problem is that there are no internal sprockets inside the gearbox to provide power to the front and back wheels.


I feel like you could just run a sprocket off of the shaft, then chain the front and back axles to it, then direct drive the middle wheel. As long as the sprockets have the same number of teeth, I do not think that there would be a problem with this.

[MichaelBick]

Last year we used supershifters on our WCD. We just made an adapter plate to mount the supershifter to our drive. If I were to run the Vex ball shifters this year I would mount in this same way.

[AlecMataloni]

In 2011, Team RUSH (27) used 221's "Super Light Rolling Chassis" with the chains mounted outside the chassis perimeter. Would this work for you?

[BJT]

The two stage version has that nice curve on the bottom, which looks like it would be nice especially with small wheels, but, at least in our wcd, we would need the 3rd stage which makes the whole package a lot harder to work with.

[Timz3082]

Based on calculations with the JVN Design Calculator and input from various sources, I can say without a shadow of a doubt, it will all depend on what you want to achieve.

That said, it looks to me as though a VEXPro Ball Shifter 2 stage will need an extra reduction to get it where you might want it with 4" wheels. Somewhere in the neighborhood of 26:15 or 28:16.

Again, I am NOT an expert on this subject......yet. Please determine your needs and do your own calculations before you make a decision.

Actually, using the JVN Design Calculator, the overall reduction should be between 15:1 and 7:1 so gearing down off the gearbox about 2:1 should result in those ratios which would be a good all around performing drivetrain!

[connor.worley]

I feel like you could just run a sprocket off of the shaft, then chain the front and back axles to it, then direct drive the middle wheel. As long as the sprockets have the same number of teeth, I do not think that there would be a problem with this.

Remember: WCD chains the front and back wheels separately.

[Walter Deitzler]

Remember: WCD chains the front and back wheels separately.

I was thinking either two separate sprockets or one of those double-sprockets.

[JB]

We will post a rough draft of our "Vexpro WCD" before the end of the weekend, and maybe follow up with a more refined setup before ship.

We are also heavily tempted by the WCP gearboxes. They are an iteration of our custom gearbox design, so they'd likely be a good fit into our designs.

I CANNOT WAIT TO SEE THIS.

We are thinking about doing this with belts and just using the 1x3 as the mount plate for the third stage with larger standoffs. Which would allow for the pulleys to be contained in the 3rd stage of the gearbox.

[James Tonthat]

I made this yesterday, but I think we might be pursuing a different option at this time.

The ratio on this is

12:50 1st Stage - CIMs
14:50 1st Stage - Versaplanet 4:1 (I like just putting it in on the plate just to have the option.)

50:44 High
34:60 Low

30:40 3rd Stage

Edit: Probably should have added another view to be more descriptive.

[Nemo]

I'm picturing a wider custom version of the 3rd stage add-on that Vex sells. Put your two sprockets inside and change the 3rd stage ratio to be appropriate for direct drive. Sounds like a fun winter break project.

[Brian Selle]

If you are able to remove the hex output shaft pressed into the ball shifter shaft and replace it with your own, you could just add some pulleys/sprockets and a couple standoffs like the attached picture. The picture shown has 30 tooth pulleys and the clearance with the 4 standoffs is close... to get more clearance with smaller pulleys/sprockets you could rotate the entire gearbox slightly about the output shaft and use the 2 standoffs in the upper left/lower right corners (2nd picture). Would be good to work in some more support for the cantilevered gearbox.

13286
13288

[MichaelBick]

If you are able to remove the hex output shaft pressed into the ball shifter shaft and replace it with your own, you could just add some pulleys/sprockets and a couple standoffs like the attached picture. The picture shown has 30 tooth pulleys and the clearance with the 4 standoffs is close... to get more clearance with smaller pulleys/sprockets you could rotate the entire gearbox slightly about the output shaft and use the 2 standoffs in the upper left/lower right corners (2nd picture). Would be good to work in some more support for the cantilevered gearbox.

13286
13288

If I remember correctly, the output speed of the ball shifters without the third stage is a bit too fast to direct drive.

[AdamHeard]

Posted CAD of the implementation here (http://www.chiefdelphi.com/media/papers/2567).

This is a real rough model showing our concept for mounting the ballshifter only, it's a bit clunky now and if we ran with this we'd likely refine the mount a bit more.

Don't interpret this as a specific decision by 973 to do 8wd with that spacing, those wheels, etc... but rather focus on the ball shifter interface, and that we're switching to 1/2" hex all around in hex bearings.

Hopefully this helps a few people.

[MattC9]

Posted CAD of the implementation here (http://www.chiefdelphi.com/media/papers/2567).

This is a real rough model showing our concept for mounting the ballshifter only, it's a bit clunky now and if we ran with this we'd likely refine the mount a bit more.

Don't interpret this as a specific decision by 973 to do 8wd with that spacing, those wheels, etc... but rather focus on the ball shifter interface, and that we're switching to 1/2" hex all around in hex bearings.

Hopefully this helps a few people.

Adam, unfortunately my cad is not working :( could you add a picture or rendering of what y'all have come up with? Also... I see Hodgepodge and Viper, what are those? Again my Solidworks isn't working so I can not see these models.

P.S. I didn't mean to put that purple smiley next to the post... and I don't know how to take it off.

[JB987]

Adam,
Can you post a screen shot or two?

[AdamHeard]

Sheesh, nobody is ever satisfied :rolleyes:

Here is an iso with the frame supressed, and then with the mount plate made transparent.

[BJT]

Thanks for the pic. thats essentially what we do with supershifters, but this got me past a mental block I had with implementing the 3 stage ball shifter.

[AdamHeard]

Thanks for the pic. thats essentially what we do with supershifters, but this got me past a mental block I had with implementing the 3 stage ball shifter.

Yup! Trivially different from what we did w/ SSers in 09.

The biggest pain was how to cleanly attach to the face of the ballshifter w/ the extra standoff we had.

It's clear in CAD, but not in the pic. The lower hex standoff doesn't attach to the ballshifter, but rather to that .25" thick plate with a hidden flathead 1/4-20. The plate then attaches to all 3 ballshifter mount holes and is a large bearing surface on the face. This should really adequately handle the moment reaction.

Since we don't have one on hand, we were unsure of the strength of that face. We assumed that since IFI put in hex bores for standoffs, that small local face contact for moment reaction would cause damage. So right now we're assuming we need that large plate to touch so much.

[DampRobot]

Sheesh, nobody is ever satisfied :rolleyes:

Here is an iso with the frame supressed, and then with the mount plate made transparent.

Thanks for posting the pics. (It's great to be able see what you're talking about without downloading it and waiting for SolidWorks to load.)

Is that plate supposed to be flush with the 2x1 tubing? If so, there's going to be some interference between those two button head screws and the tubing wall. Also, how would you plan to remove the gearboxes in competition?

[AdamHeard]

Thanks for posting the pics. (It's great to be able see what you're talking about without downloading it and waiting for SolidWorks to load.)

Is that plate supposed to be flush with the 2x1 tubing? If so, there's going to be some interference between those two button head screws and the tubing wall. Also, how would you plan to remove the gearboxes in competition?

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.

[JB987]

Sheesh, nobody is ever satisfied :rolleyes:

Here is an iso with the frame supressed, and then with the mount plate made transparent.

I'm satisfied now:D

[David Doerr]

Posted CAD of the implementation here (http://www.chiefdelphi.com/media/papers/2567).
Don't interpret this as a specific decision by 973 to do 8wd with that spacing, those wheels, etc...

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

[JB]

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]

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]

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]

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.

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