The Ultimate West Coast Drive Guide presented by 3506

Technical Technical Discussion
1

The students and mentors of 3506 have been helping teams in our area build West Coast Drive systems for a number of years and we finally compiled all of our knowledge and tips into one specific source we are calling the Ultimate West Coast Drive Guide.

What makes it the Ultimate Guide? Well, we want to collaborate with everyone in the community to make this project into an ongoing and living guide for how to build in our opinion(Swerve guys cover your ears), the best drive system out there. With the development of NEOs and newer tech, this guide should evolve too!

We have started by creating a step by step guide on how to go from concept to ordering parts for the system in five steps posted here in our video series;

These steps are:
1)Robot Characteristics (strategy and concept)
2)Doing the Math using the JVN design calculator
3)Framing and CAD creation including the specific designs behind drop centering and wheel well spacing
4)Belly pans and bumper considerations
5)Components and hardware ordering

We have specifically aimed this at teams who have never created a custom chassis before and want to get off of the kit. There are many ways to build an awesome West Coast Drive system out there but we wanted to keep it as simple as possible for a newer team to tackle this challenge and show that it is not as difficult as it may seem to make a custom chassis if you have the right tips and tricks.

With the above being said we want to expand this into a much deeper guide on how to maximize everything West Coast Drives have to offer including sprint distance calculations and more complex topics. We are taking all requests and collaborations here on this thread for these additional video topics and any constructive criticism is welcome and wanted so we can improve this data! You can tell us where to go next with this!

Since we have taken several months to compile the first part of the series we plan to record an assembly video after the holidays that will most likely happen during build season in the form of a live stream during week 1 using our two new robot chassis. At that point we can answer questions during that stream on assembly. We want to record and post this as well assuming the audio is good enough.

We would love to include every single detail and minutiae possible but we feel that this level of detail is sufficient for a walk through. However if questions do come up this thread will help serve the purpose of making the entry level to this capability easier than ever before.

Since it is about that time of year where Chief is flooded with WCD and drop centering questions, we hope that this information can help some team out there who is thinking about making their first custom chassis system.

Happy Holidays and see you all in 2019!

1 Like
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I just watched the first two videos in the playlists and these look really well done. Good job.

3

Robbie,

Just thumbing through your video series and liking what i see so far! Thanks for putting this together for the greater community. I think its a very detailed guide for how to do a WCD, between the triple helix videos and your series i think teams are in good hands!

Thoughts for a possible 7 video, fixed C-C distances with chain adders or chain in tube concepts (CIT)?

4

I definitely want the students to get a C-C distance video going as well as some basic do and do nots around degrees of wrap on a sprocket. Too many good designs have gone poorly because of silly chain mistakes and it hurts my soul to see it.

(Anyone ever just jam a floating sprocket between two long lengths of chain to watch it go?)
http://team228.org/media/pictures/view/6874

We have yet to try chain in tube style because of the deviation from stock parts but we certainly want to give it a go! There has been some shakeup recently with parts used in most of these designs so we may wait it out a bit longer because we would want to experiment with the difficulty first before recommending it to other teams. There is an active discussion on where to get the sprockets for that here:
https://www.chiefdelphi.com/forums/showthread.php?threadid=166540

Since Triple Helix has an excellent machining guide on how to do chain in tube, I would direct you all to this video series here which is well done for the machining strategies if you go the chain in tube route. Oh, and also air cooled gearboxes!:

5

We did that this year. We somehow messed up when doing our C-C this year (I believe tried to add a little too much to the centers for tightness). We had some 26 tooth sprockets left from years ago that were never getting used so we stuck them in and they worked. It wasnt surprising to have it sitting on the field from getting in a pushing match but we just picked them up and put them back in. We ended up crushing a couple sprockets during push matches, and ultimately it destroyed our encoder through impact at WMRI this year. We even did a floating pulley for belts this year. We had issues with belts getting loose very quick so we had a large pulley float in our intake.

And for the chain in tube, have you seen the new sprocket AM released to help move chain in tube towards COTs parts? 25 Series 17 Tooth 0.5 in. Hex Sprocket - AndyMark, Inc

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I like it! Have you guys thought about touching on belt drive?

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I just measured in Solidworks and it looks like this sprocket would work for 25 in tube but probably not #25H (.010 is too close for me!) I can certainly try to buy a couple and try them if a student on YETI wants to design one up with an appropriate gearbox or utilizing some old equipment.

Flipped CIM and chain in tube would be interesting because maintaining the system would be easier but it does not really fit the exact style of what a West Coast is.

I see the benefits but the drawbacks for a newer team would cause me to steer them away from this route especially if they are competing in a district where repair times are painfully short when something goes wrong.

8

we usually dont do belts but most of the same design considerations need to be taken with respect to tensioning them using cams

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Great series guys! well done! I would like to see a more in depth video on bumper mounting.

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We have been talking about this internally and we may just incorporate a bumper section during build season for the 2019 specific challenge when we do our frame since these parts usually come in at the same time as our belly pan.

Every game is different and every challenge will ultimately change the bumper height and mounting. One thing to mention is that when we do our frame analysis and check for field and game piece collisions, we do have our bumpers drawn since bumpers can and will interfere with game elements.

You can see @ 5:30 here how we do this:

11

A couple of quick updates and questions have come in from a few sources on this guide:

  1. The first one was about the gussets we use in the corners. Our bumper brackets serve as our corner gussets for most of the designs that are shown in the video but yours may vary because it depends on your bumper design. Ours happen to be formed sheet metal pieces that actually bolt on for maintenance and these take the place of the rivets we typically put in the belly pan. These holes are 5/32 for 10-32 bolts.

You can see this easier at 6:48 in this video:https://www.youtube.com/watch?v=1u2NJYlP5YQ&list=PLfta28txoIIqAjocoOT69-1wFxw9t0KIk&index=5

Some of the wheel spacing values would not allow for the standard Vex gusset to fit in the corners without shaving them down some. When adding these designs to CAD you would see if this would be a problem for your particular wheels spacing. Our belly pan gives our team the most rigidity but it is true that you should tie the top corners together with some sort of gusset whether that is riveted or bolted.

  1. Someone asked what the tools used in this video at 12:41 are : https://www.youtube.com/watch?v=IDgdbo9Z-oo&index=6&list=PLfta28txoIIqAjocoOT69-1wFxw9t0KIk

These are called Cleco removable rivets and they are used in multiple industries. I had never actually seen these before until recently when one of our mentors who is an aircraft mechanic brought these in and I can say that they are amazing. They are great for mocking up a riveted connection without the need of adding the rivets and drilling them out if something goes wrong.
We own these in 5/32" and 3/16" for our rivet sizes.

Source for these if you want some:https://www.rivetsonline.com/rivets/cleco-fasteners-temporary-rivetsside-grips#1

  1. If using the 1.5" hole for the outer wheels on the drive rail will the bearing fall out of the block? Yes, this can happen if your don’t put spacers inside which is why we use the slot we show in the CAD video. In this video series example, we gave a larger hole size so that the chain could be tensioned with enough space such that the axle wont hit the frame. You could go with a smaller hole like 1" but you will have less room to tension the chain - slots are better that the 1.5" hole. We use a 1.5"x .75" slot at our wheel centers but teams who do proper C-C chain calculations will not even require an oversize hole. I will make sure we point this out during our assembly video.

Thank you all so far for the support!