Thank you for your feedback. Yes the gearboxes are mounted on by only 2 bolts, i was wonderig of a way to fix that and R.C. has responded with a great idea. I will be editting the cad to allow better contact. If you would still lile to see the exploded view let me know and i will happily render it out with the frame’s transparency changed, it just that knowing we will probably be changing to chain it we wont have that issue any longer
If you are concerned about running chains inside the frame perimeter you can easily put the sprockets on the back of the wheels and run the chain system that way. It will reduce the interior available space but will eliminate the need for chain covers. The chain covers will reduce the interior space available so in reality it about the same amount of space. If you like I can send you our CAD from last year.
Here is one of our CAD models with chain runs behind the wheels. Pardon the overly large sprockets… We ended up moving the chain to the interior for that year.
http://www.chiefdelphi.com/media/img/976/976dd0fc301f62b964f598cc9ae90ccd_l.jpg
Last year we used the WCP 3CIM DS transmission with chain runs inside the frame perimeter. We installed chain covers, like on a bicycle. The chain covers worked just fine but this year we are going to run the sprocket & chains in the frame…
http://www.chiefdelphi.com/media/img/1e0/1e0bc1a0882c360654d550dbe70e30e9_l.jpg
Keep it up!!
Aloha
Mr H.
I would love to see your cad from last year to reference the chain idea. Being our first time with WestCoast, anything will help!
Do you have the center wheel dropped lower? If so, how much lower? I think I have seen some teams that did not drop their center wheel, how much of a difference is this? Is it beneficial or not? For those that did not drop the center wheel, would you recommend it?
The current design has a .125" drop.
Many of the suggestions here have been incorporated into an updated version. I will see if I can get the improved version up soon.
If there is no drop center you will run into scrubbing (robot hopping from the outer wheels having too much traction to allow smooth turning). I have seen the use of Omni wheels to resolve this on a non dropped WCD.
1/8" drop is the norm for the center wheels. If you keep the weight centered well enough, spinning around is very easy! As mentioned, even when weight is not centered, on a drop center drive the robot will rock to one end and essentially be 4wd with a short wheelbase, which will turn much easier with less scrubbing than 6wd non drop…
Yeah robot doughnuts!
Aloha!
I’d recommend using colsons and then shaving down the center wheel till happy with your drop. We started out with 3/32 and ended up with 1/16 or none.
Did you find 1/8" gives too much rocking of the chassis?
By intentionally shaving down the center wheel, which usually wears down fastest anyway, aren’t you introducing a different effective FPS from the center wheels than the front and rear wheels? I know this is done on purpose with some 4x4 vehicles to increase traction on surfaces that will allow slippage, like sand or gravel. Are you suggesting to do this as a way to determine optimum drop, or something else.
^THIS ^
We started with 1/8" and kept it. By championship it was worn close to 1/16th and ran like a champ… Though might of been that WCP 3CIM DS transmission… 
With the deformation of the carpet and the Colson wheels, it was ready to go at 1/8" !
I will get the CADs up over the long weekend… like the end of it because the weather is great!
Aloha
Thanks everyone who gave suggestions and comments. This is almost becoming a “Design by Community” project.
Here are two new renders. Most of the suggestions have been incorporated now. In the oblique projection, we noticed the tension cam is on the wrong side of the block. Ooops! It is corrected in the overhead render.
The people running the wiring and the pneumatic tubing will be much happier with this version.
You may want to move the solenoids and the Spike a bit so you can move the Digital Sidecar away from the CRio to allow space for PWM cables.
You may want to mount your pressure gauge in a small, protected space in your upper structure that makes it visible.
You may also want to add a voltmeter next to the pressure gauge. We found it handy for knowing when to stop the practice and change batteries.
I may have to grab a couple of those meters for myself. let alone the robot(s).
Many of the items included in this render will not be located where they are due to the new RoboRio controller and speed controllers. No DSC’s with the new controller, so that will give a bit of extra room.
Additionally, the new game will dictate changes that can’t be anticipate at this point in time.
Is there a Digital Pressure Gauge too by any chance, hopefully we will never rely on air again, but any information during a match is great to know as a driver.
With a pressure transducer similar to this one, and a digital displaylike this one all being driven by our good buddy Mr. Adruino, we can cook up one of our own!
Who on the team would be a good candidate for this project?
Tyler 2.0, aka Daniel is amazing when it comes to Arduino, he would be perfect for this project.
Another option would be to use wider tubing. If you aren’t riveting to the top or bottom of the tube (so clearance isnt’ an issue), I would recommend 2x2 tubing and 15mm belts. If you can make your own pulleys, you can fit it in 2x1.5 tubing with some creative counterbores. Since it does seem like you are riveting, 3x1.5 tube is safer, but that’s definitely adding some weight.
We planned on using belts because of their minimal stretching, but after recieving all this feedback to switch to chains, we will probably be doing so.
Honestly, I think some of the feedback against belts is a bit unfair, and maybe not based on hands on experience. If you design your belts right, you should never need to perform maintenance on them inside a tube; we’re going into season 5 without a belt failure. Even with an in-tube design it is possible to change a belt in 10-15 minutes if you think carefully and know what you’re doing. You do not need to remove the entire gearbox to change an (internal) belt - you slide it out a few inches until the pulley is free, then slide it back in once the next belt is in place. An access window above the middle wheel will help with this. If you leave the ends open you do not need access windows on the outer wheels.
All of this said, there are compelling reasons to use chain over belt, particularly if you are running the power transmission external to the tube. Chain drive external saves weight in using a smaller extrusion profile, and I guess it saves a little space too. In the case of using belts outside of the tube, a belt drive failure would require removal and disassembly of the gearbox, and that’s no fun. It’s really up to preference, and whether or not you want to tension after the fact or not. If you like tensioners and bearing blocks, chain is a lot easier. If you can machine “exact centers”, where your wheels are fixed the exact distance apart that a belt calls for, and you don’t mind a “fatter” drive tube, belt drives are nice.
So maybe they weren’t wrong… Just thought I’d add some data and explain the logic behind internal belt drives a little bit more.
I think a lot of people are debating belts is its possible to put too much load on certain combinations in a drivetrain. The smallest chain system you can buy is 25 chain with 16t sprockets. The torque calculations with 4 inch wheels are still within spec of 25 chain, even with 6 cims. Whereas with 9mm belts and 24t pulleys, you are out of spec for the belts. I saw alot of teams (including us) use that combination this year, and it did not work out well. Had we gone up to 30t pulleys we most likely wouldn’t have broken a single belt, but if you have a baseplate mounted under 2x1, like in most WCD’s, you actually cannot fit a 30t pulley without pocketing the baseplate, or spacing it out. And inside a standard WCD its harder to fit 15mm belts.
So if you make sure to put the right size belts in, they can be a great system. But I would not use 9mm belts with 24t pulleys. You will most likely have a bad time if you do.
We’re also looking at WCD this year and doing something similar to your setup. We are mounting the gearbox with the WCD mounting block and then using chains & sprockets to get to the other wheels. Pic show concept - brown items are the chains (not belts).
Definitely planning some sort of chain guard/cover.
