VexPro VersaBlock center-wheel drop

Hi all,

We recently got our drivetrain running (w/ WCP DS Gearbox, 6WD, VersaBlocks & VersaChassis).

We have our center VersaBlock with the curved section facing upward, and the outer VersaBlocks with the flat face upward in order to drop the center wheel.

However, the drop in the center wheel is very concerning. It’s more than 1/16th. Closer to an 1/8th. About 0.1" from what we’ve measured.

The drivetrain is much more noticeably tippier than the kit bot.

Is this bad? Is it good? Should we be worried? Personally, it feels bad to us… doesn’t feel right.

Hoping someone can elaborate.

The drop should be 1/8". Each block is 1/16 off center, so when you flip them it adds up to 1/8. Thats been the FRC standard for a long time. With the shorter bots, it does need to be closer to .1, but 1/16 drop will not be able to turn, even with the short chassis. It should be fine, and thats what we are running.

Not next to a real computer atm (I’ll try to answer as much as possible),

But the VersaBlock was designed for a .125" total drop. It was never designed for a 1/16" drop, its offset 1/16" from center. So .0625 + .0625 = .125" total drop. Our team has ran between 3/32" to a 3/16" drop along with a handful of others. Our robot this year has a .125" drop as well for reference.

Do you have a full loaded drivetrain (148 lbs?) Or is it just the chassis.

Hey there,

Because your center wheel is 1/16" lower than the middle of the 2x1 frame and the outer wheels are 1/16" higher than the middle of the 2x1 frame your current drop is an 1/8" ON EACH SIDE totaling to 1/4".

If you flip only one of the outside blocks you will have an 1/8" total drop.

Cheers, Bryan

Gotcha.

And it’s just the chassis. We all assume that the tipping would be considerably less noticeable (and more beneficial) with added weight, but are still hesitant and weary as of now.

This is actually our first 6WD, which may sound weird for a third-year FRC team, but first year we did a wide chassis w/ 4WD and last year we did mecanums so we’re finally transitioning!

Makes sense,

Once loaded, you’ll be more than fine. Otherwise you’ll have a fun time turning :wink: Your probably running a similar/identical setup as Team Copioli did for build blitz.

I believe so! Except we’re running WCP WCD DS Gearboxes instead of ballshifters.

I believe we’re running the de-facto VersaChassis; 6 versablocks, versa wheels, 9mm HTD belts on the inside, versa wheels, WCP WCD DS gearbox, and VersaFrame.

Yeah you’ll def be fine, it seems a bit weird the first time. But once the drive is loaded and the robot is built you’ll be glad there is a nice drop.

Fantastic. One more question - what’s the proper means of attaching the CAMs?

On this Page:

http://www.vexrobotics.com/catalog/product/gallery/id/26220/

http://www.vexrobotics.com/vexpro/west-coast-products/bearingblocks-g.html

The picture above should show it, all you do is mount the cam dead center. Put a 10 hole through both sides of the tube. Thread a #10-32 bolt into the cam, don’t fully tighten.

Make sure the bearing block/VersaBlock can slide by hand, then just rotate the CAM. The CAM will push the block away from it and tighten the piece of chain/belt. Then just tighten the VersaBlock/Bearing Block & CAM. That’s about it.

If you feel the drop is too much try only flipping the front or rear ends instead of both.

The 1/8 drop is a bit much for today’s robots, back when all the bots were 38" long it was ideal. With any robot less than 30" 1/8 is a bit much, with a squarish drive train it is overkill.

As mentioned flipping either the front or back block would result in a 1/16 drop. You just need to decide which one. If most of your weight is towards the half with the two flipped blocks then you can expect the frame to sit parallel to the floor most of the time.

The machinist in me came up with a different solution:
When I was considering the Versa chassis my first thought was to fabricate a custom center block, or at least modify the existing block. You can do this by milling the slot so that it is larger in the opposite direction you want the wheel to go(if you wan to raise the center, mill the bottom slot. You can then use sheet metal of the same thickness to shim the excess, as long as the shim is 1" it should be contained by the blocks. The milling has to be rather precise, so be careful when doing this. Consult a machinist if you must, this has to be set up square and in line with the table. The tolerance of the slot against the tube is quite tight.

In a long robot configuration you might find that it is not as exaggerated as it initially appears once it is at full weight and on carpet, so test it out before doing anything drastic. A little extra drop won’t effect you that greatly in this year’s game.