Re: VEXPro 2014: After The Season
 

I believe you aren't able to shift because the VEX solenoid valves are not entirely actuated by electromagnets, they by require ~30 PSI (iirc) to trigger properly. Someone from VEX should be able to verify/refute this.

Re: VEXPro 2014: After The Season
 

Maybe, but you could hear the cylinder engage and the driver could feel it trying to get in gear. It doesn't really matter anyway, shifting under 40 psi is more than I would expect from a shifter. We were able to get through a match with 2 black clippard tanks charged to 60 psi.

Re: VEXPro 2014: After The Season
 

Unfortunately, if the solenoid is the known limiting factor in the shifting, it does not help me much.

I had an idea for an electric shifter, and less force means faster, so delivering 14lbs of force (0.75" bore piston at 30psi) is much more ideal than 28lbs (60psi equiv), if it does the same job but quicker.

Re: VEXPro 2014: After The Season
 

Update!!!

3 CIM Single Speed, Single Reduction gearbox (7:1)
After 2 Districts, 1 District Championship, 1 six hour demo, and hours of drive practice, one of our drive axles snapped clean in half

Details:
We have become known in the NE and specifically CT area for our drivetrain. At the Groton District Event we even recieved the Engineering Excellence award for it. We give credit mostly to these wonderful, simple, and great looking gearboxes. Our defensive play became a force to fear! We could push almost anyone which put alot of stress on the gearbox.
Our setup is our own custom drivetrain. Tank drive, with 1/16 drop. Six 4 inch HiGrip wheels that are ran by belts . The belt that transfers all motion from the transmission axle has a tensioner. Their are many other things that put us above others but it isnt too important to this.
After awhile we noticed slop in the gearboxes, so we added some extra bolts, tightened some axle collars, and added belt tentioners. This eliminated most slop but there was still some in the transmission axles. We went like this for 1 1/2 more districts, demos, and drivers practice.
Finally at CT State Championships after 4 matches our new driver lost all control to the right side. It was discover the axle could spin freely by hand. After opening it up and finding a broken axle, our day was over. No one had any spare gearboxes. With no choices, we had a barbeque in the parking lot and could no longer compete. (The barbeque was a blast and no one was that upset about dropping out due to the team bonding)


The gearbox was overall fantastic but I hope no one else ran into this problem. This problem ended my last competition as a student a bit too shortly :(

Re: VEXPro 2014: After The Season
 

You couldn't machine a new one? It's a pretty simple part to make.

Re: VEXPro 2014: After The Season
 

CT State Championships, had pit sizes of 6 X 8 . Due to this smaller size everyone brought very limited parts. Mostly just basic tools. Also it did have some parts to it that would require more machining like a lathe which this venue didnt have.

Re: VEXPro 2014: After The Season
 

Did it fail at e-clip groove?

Re: VEXPro 2014: After The Season
 

Do you have photos? We have just used hex shaft in those gearboxes with out any issues. No custom machining needed, did you do custom work after to make it work in your robot? We just added a 2nd shaft collar to lock everything in place and swapped the rear bearing to a hex bearing.

Re: VEXPro 2014: After The Season
 

To be honest I didnt look to closely, but it did seem like it broke in a groove. Basically a weak point. I do know it was in a part of the axle that was 1/2 inch.

Edit: I will see if we can find it, to take pictures of. No changes except putting a pulley with set screws on the hub at the end of the axle for the belts which added more pressure to the axle due to how far it was placed.

Re: VEXPro 2014: After The Season
 

Same thing happened to us at CMP last year, we discovered that one of the internal bearings can work it's way loose and cause the cantilevered output shaft to put force directly on this groove. It's for this reason that we recommend using either the WCP single stage, or a custom gearbox

Re: VEXPro 2014: After The Season
 

On a different note - it seems like VEX does not have a lot of their items in stock right now. Most notably items that fit with the 3 CIM Ball Shifter.

Is there a production problem, or will we be expecting upgrades that would make the latest rendition obsolete?

Our team is looking to order a certain configuration for off-season training and development, but we don't wish to commit until the items are in stock.

Thank you.

Re: VEXPro 2014: After The Season
 

With this type of thing, it's probably best to email VP directly. I'd suspect that if they are listing items as out of stock, they aren't in VP's warehouse and are being reordered, but I'm sure you'll get a lot better information out of them than me.

You can also check WCP, they might have some 3 CIM Ball Shifters in stock. Alternately, you can see if a WCP DS (if they're in stock) fits the bill.

Re: VEXPro 2014: After The Season
 

I'm a bit new to all the nuisances of drivetrains, but these statements seem almost contradictory to me. A 7:1 ratio on 4 inch wheels should give you somewhere in the ballpark of 14 ft/s (less when loaded). How were you able to push so effectively with such a low gear ratio?

Re: VEXPro 2014: After The Season
 

As the driver, I can tell you a few things that put us above others, drive train wise (other than my 3 1/2 years of experience)
- 6 CIMs
- 1/16 drop instead of 1/8
- belts very tight and tentioned
- within a pound of 120lb (without bumpers and battery)
- due to how low our center of gravity is and little clearance our chassis couldnt be lifted up while pushing which kept all wheels on the ground.
-change wheels after comps in order to keept treads on them
- wheels pushed outwards as possible to increase support polyigon and stability. (Instead of a wheel inbetween 2 pulleys, 2 pulleys are side by side and then attached to one side of wheel, thus pushing each wheel 1 inch more outwards)

As a driver, 1 of my favorite memories this season included a 3 on 1 match. We were alone to score with 2 defensive bots on us. I ignored them and just pushed them with me the length of the field if they got infront of me. We won that match.

Overall we were very impressed by these gearboxes, and would like to give VexPro a huge thanks, for the hard work their putting in, to produce quality products. We will most likely be using these again but supporting the axle on the other side.

Re: VEXPro 2014: After The Season
 

We are in process of deciding which components we will be adding/updating based on feedback we received this year, some parts that are out of stock may be receiving updates, as always we aim to have any updates as backwards compatible as possible.

-Aren