WCP SS gearbox on AndyMark KOP chassis am14u3?

[beerobber]

So we want to use 8" pneumatic tires for our drivetrain, and we currently have the KOP chassis and its provided Toughbox Mini gearbox. AndyMark has a conversion kit, but it is out-of-stock until Wednesday as key parts are not available: tires, tubes, timing belts, and extended hex output shaft for the Toughbox Mini gearbox.

I can source the pneumatic tires and tubes locally, and the timing belts are available elsewhere--but not the output shaft. Given time pressure, I am looking at the WCP single speed, double reduction gearbox at http://www.wcproducts.net/single-spe...uction-gearbox. It looks like the output shaft *might* be long enough. I'm thinking about replacing the Toughbox Mini gearboxes with the WCP gearboxes. Has anyone mated this WCP gearbox to an AndyMark chassis? Any other suggestions for a KOP-compatible gearbox with single-speed double-reduction in the neighborhood of 9:1 - 10:1 and a long hex output shaft?

[Thad House]

As long as the AM14U3 has the same wheel width spacing as the AM14U, that will work. In addition, Vex even provides a guide on how to mount that gearbox properly. Its kind of built for Vex shifters, but the instructions also have help on getting WCP gearboxes in as well.

http://content.vexrobotics.com/vexpr...ive-System.pdf

[beerobber]

Your reply prompted me to check the 8" conversion kit page at AndyMark for a CAD file. And there was one. The width between bearings looks to be 4.6". While the AndyMark extended hex shaft (out of stock) is a comfortable 5.7", the shaft that comes with the WCP gearbox falls short at 4.1". Unless I can substitute other WCP extra-long shafts and cut them to length, I will have to wait on AndyMark to restock.

By the way, I also discovered this morning that Rhino3D for Mac has a 90-day trial license, and works great to open the STEP files AndyMark provides. After the trial expires, the installation notes tell me it will stop saving but will still open and view files. Might be all I ever need on my Mac!

[Sperkowsky]

Originally Posted by beerobber

Your reply prompted me to check the 8" conversion kit page at AndyMark for a CAD file. And there was one. The width between bearings looks to be 4.6". While the AndyMark extended hex shaft (out of stock) is a comfortable 5.7", the shaft that comes with the WCP gearbox falls short at 4.1". Unless I can substitute other WCP extra-long shafts and cut them to length, I will have to wait on AndyMark to restock.

By the way, I also discovered this morning that Rhino3D for Mac has a 90-day trial license, and works great to open the STEP files AndyMark provides. After the trial expires, the installation notes tell me it will stop saving but will still open and view files. Might be all I ever need on my Mac!

Why don't you just download inventor (it's free for students and probably teachers) or apply for Solidworks licences next year.

[beerobber]

Originally Posted by Sperkowsky

Why don't you just download inventor (it's free for students and probably teachers) or apply for Solidworks licences next year.

Sounds like you aren't a Mac user!

We have SolidWorks for CAD running on Windows machines, and some of the kids use BootCamp to run Windows on their MacBooks so they can use SolidWorks. I'm the scrounger sourcing parts, and I'm not interested in licensing Windows for my Mac. Pulling up CAD and STEP files read-only in Rhino for Mac is perfect for my needs.

[KrazyCarl92]

Something you would likely benefit from exploring are different gear ratio options. AndyMark's Tough Box gear ratios really are not well-suited for 8" wheels, especially given that this years game has a very divided field.

On a field that is not as open (like this year's field, 2012, 2010, etc.) acceleration will be more important. In years with a more open field (e.g. 2013, 2014), top speed will be more important.

For this year's game I would strongly suggest your gear ratio correspond to a top speed of roughly 8-10 ft/s for a SS drive train if you can get ample practice, and roughly 6-8 ft/s for a SS drive train is you are going to go to competition cold turkey. My personal ideal top speed would be 9 fps for this game with a SS drive train.

Based on my calculations, the standard KOP gearbox with the 8" pneumatic wheels will gear you for about 14.1 ft/s top speed. This will still work, but you may not fare well in pushing matches. If you are going to put the money and effort into the WCP gearboxes (which are great gearboxes by the way), you may as well get yourself closer to an optimal gear ratio and get a different ratio, such as their 17.86:1 ratio available by using the 12 tooth pinion with their 60:14 gear set to achieve a top speed of approximately 8.4 ft/s.

[beerobber]

Thank you, thank you for that! I spent half an hour this morning trying different setups in the JVN mechanical design spreadsheet and had realized that the 8-inch wheels needed a higher ratio than the Toughbox Mini. The single-speed gearbox you mentioned comes with a hex shaft that is the correct length for the chassis we have, and I was just wondering if the 60:14 gear set was the right one. I'm going to give it a go.

[KrazyCarl92]

Yes, that is the gear set I would suggest for this game and 8" wheels. I notice that your rookie year is 2015, so this would be the first time you and your team have faced a challenge where you really do have to consider the high current conditions your motors may see (pushing matches, field obstacles, etc.). Last year these were insignificant for the most part because of the lack of interaction between alliances and the basically flat field.

The one case where I might consider going a bit faster (maybe add 1-2 ft/s on the top speed) would be if your strategy involved fast cycles going from the secret passage straight through the low bar over and over again because the sprint distance involved would be a bit further than most other strategies. However, that is a bit of an edge case.

[Sperkowsky]

Originally Posted by beerobber

Sounds like you aren't a Mac user!

We have SolidWorks for CAD running on Windows machines, and some of the kids use BootCamp to run Windows on their MacBooks so they can use SolidWorks. I'm the scrounger sourcing parts, and I'm not interested in licensing Windows for my Mac. Pulling up CAD and STEP files read-only in Rhino for Mac is perfect for my needs.

No I am not. If you just want to view parts Grabcad has a decent in browser viewer.

[Thad House]

Originally Posted by beerobber

Your reply prompted me to check the 8" conversion kit page at AndyMark for a CAD file. And there was one. The width between bearings looks to be 4.6". While the AndyMark extended hex shaft (out of stock) is a comfortable 5.7", the shaft that comes with the WCP gearbox falls short at 4.1". Unless I can substitute other WCP extra-long shafts and cut them to length, I will have to wait on AndyMark to restock.

By the way, I also discovered this morning that Rhino3D for Mac has a 90-day trial license, and works great to open the STEP files AndyMark provides. After the trial expires, the installation notes tell me it will stop saving but will still open and view files. Might be all I ever need on my Mac!

Are you looking at the WCD version of the WCP gearboxes? The WCD version uses the same shaft as the standard version, however the WCD bearing block, and space for sprockets take up alot more room. When using the standard version, the shaft is probably close to 6 inches long from outside the gearbox.

[Ryan Dognaux]

This is the exact setup we're using this year and the output shaft fits fine on the AM KOP frame. We should have a video of it up and running here in the next day or two. Feel free to PM me with any of your questions.

Here's an image of it while it's still being built but the gearboxes are attached. You'll see a lot of shaft that we actually need to chop off.

Note: Don't use WD-40 to lubricate your gearboxes, that can was just sitting there for some reason.



The great thing about the WCP SS gearboxes is you have four options for pinion gears, so if you feel like you're going a little too slow or a little too fast, you can easily change pinion gears to adjust your top speed.

[KrazyCarl92]

Originally Posted by Ryan Dognaux

Here's an image of it while it's still being built but the gearboxes are attached. You'll see a lot of shaft that we actually need to chop off.

How did you get the holes in your inside rail for mounting? Use the bearing in the outside rail for alignment, then match drill? Some other method?

This information would be instructive for those looking to your image for inspiration on how to integrate WCP SS gearboxes into their design.

[Ryan Dognaux]

Originally Posted by KrazyCarl92

How did you get the holes in your inside rail for mounting? Use the bearing in the outside rail for alignment, then match drill? Some other method?

This information would be instructive for those looking to your image for inspiration on how to integrate WCP SS gearboxes into their design.

Yep, exactly. Put a bearing through the drive side plate which will partially stick into the outer gearbox plate. Depending on how you align them, there's a chance for one of the 1/4-20 AndyMark gearbox mount holes to overlap the WCP gearbox mounting holes. We rotated ours until there was a good amount of material for all 4 holes, clamped the plate and then drilled using a 3/16" drill bit.

I would do this prior to assembling the gearboxes. You'll also want to really think about which side is which before drilling them to ensure that your gearboxes end up as mirrors of one another and that you're actually mounting on the correct side of the plate (belly pan flange should point inside).

To avoid confusion we wrote which side of the left / right and marked the front of the of the drive with an arrow pointing forward. The process of drilling the holes took all of 3 minutes but ensuring that we were doing it correctly before drilling the holes probably took 10 minutes of triple checking.

[beerobber]

Wow, thanks for the picture! My WCP SS gearboxes are (hopefully) being picked for shipping right now. I'm psyched about the easy gear change options. It looks like your front and rear wheels are free-spinning, no belts. So you are just using the 2 center wheels for traction? The AndyMark kit I'm waiting on includes timing belts and hub extenders and moves the outer bearings another inch or so towards the end of the output shaft. I'm curious about whether you've prototyped this 2x6 drivetrain on the defenses?

[Ryan Dognaux]

Originally Posted by beerobber

It looks like your front and rear wheels are free-spinning, no belts. So you are just using the 2 center wheels for traction.

We are running #35 chain to the front and back wheels from the center wheel / shaft stack up, it's just not shown in that picture yet. I'll try to get a photo of this tomorrow. I'm sure belts will work fine, but we just really wanted to make a drive that could stand up to the abuse of the various defenses.

We did a combination of AndyMark and VEX parts to make that happen easily. We're using 8" AndyMark tires and VEX VersaHubs, Sprockets, and the plate mount versahubs. You can use 1/4" ones on the side of the wheels that don't have a valve stem and 1/2" ones on the side that does have a valve stem.