WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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?

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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?

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

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.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

That sounds robust. So the VersaHubs attach to the AndyMark hub assemblies for 8" pneumatic tires? I would think it simplest to use the 12-tooth sprockets with hubs, double for center wheel and single for the others with spacers to align everything, but there's probably a reason to use plate sprockets instead. I would love to see another photo if you do have a chance, it is very helpful to me as we try to sort through all our options.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

You can actually press the VEX Versahub into the opening of the AndyMark hub because they're both 1.125" in diameter. The 6 hole bolt pattern lines up with the AndyMark hub and gives you a versapattern to easily mount plate sprockets to.

The smallest #35 plate sprocket VEX sells is the 22 tooth and that's what we went with. Anything smaller and you can't easily attach it to the wheel. We're running what is commonly referred to as 'dead axle' on the outer wheels - meaning we are just rotating the wheels on a shaft instead of rotating the shafts to drive the wheels.

I should also note that we had to drill out all of the VEX components because the AM hubs require a slightly larger diameter bolt. Not a big deal for us and it allowed us to use 10-24 screws to assemble everything.

Attached a few photos, one from our CAD that shows the wheel stack up and one I snapped tonight from underneath the drive itself. The CAD needs to be updated to reflect the use of 1/2 inch versahub sprocket attachment pieces and we didn't use all those hex bearings on the center wheel because it's unnecessary when you use 1/2" hex versahubs. The chains aren't very aligned yet and we still need to cut spacers for the dead axles that allow you to really clamp down on them, but we were able to clear all the static defenses tonight. Feeling good about the drive so far!

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

How did you attach the hex versahubs to the andymark wheel hubs? Our team is having a little trouble trying to attach those to our pneumatic wheel hubs (Andymark), we're trying to run these wheels on a custom chassis using chain also using the WCP SS.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

Is it just me or does it look like the wheel valve stem will run into the drive plate?

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

They just pressed in for us, with a bit of force. A rubber mallet is a good tool to help persuade them. Make sure your 6 bolt pattern is lined up before you really get them seated all the way. You can put a bolt or two in to help keep them on track. I'd highly recommend taking a 1/2" hex shaft and make sure you can slide it through both sides of the versahub just as a test. Here's some clarification, let me know if you were asking about something else though.



It's definitely a tight fit but so far we've only seen some minor rubbing from our non low-profile nuts and bolts on the center wheel stack up. Once we switch to the correct hardware everything should clear completely. We ordered both the 1/2" and 1/4" spacer versions of the sprocket attachment versahubs and used the 1/2" version on the sides that includes the valve stem. On the outside wheels we just always made sure to flip the wheel so that the valve stem was pointing to the area with the most clearance.

The middle wheel is a bit of a challenge. The valve stem cap barely rubs on the chain, we're looking at different caps or a way to just keep the valve stem slightly out of the way.

Our team usually ends up packaging tight drive rails to free up more space on the inside. It means a little tighter work space if something goes wrong with the drive train but we've gotten pretty good at handling those situations.

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

Thank you for the clarification! I still have one more question (hopefully :yikes: ) that I'm gonna post here, since it might benefit other teams too.
What size bolts were you guys using to secure the hex versahubs to the hubs? Last night we were trying to figure out how to secure these to the hub itself, without the risk of the having the versahub fall out (or slip) and allow the wheel to get misaligned, free spin, etc.

Thanks in advance!

Re: WCP SS gearbox on AndyMark KOP chassis am14u3?
 

We used 10-24 bolts, I'm not 100% sure on the lengths though. I know we didn't have the correct ones on hand and just to get it done we got them assembled and then used a disc grinder to cut off the excess. I'll check tomorrow in the shop because I know the correct lengths came in for our competition version of the robot.