Re: pic: Shifting Drivetrain with Transmissions
 

Keep in mind traction-limited versus power-limited. IIRC, 8-10 fps is the "traction limited" range (there's a calculator on West Coast Products for this). Your high gear should be at 15+ fps and your low gear should be close to the maximum traction-limited range.

Re: pic: Shifting Drivetrain with Transmissions
 

10 fps is almost certainly not going to be traction-limited for a 4CIM drive unless you have a really light robot or really slippery wheels.

Re: pic: Shifting Drivetrain with Transmissions
 

Oh, 4 cim. I didn't notice that. :o

Re: pic: Shifting Drivetrain with Transmissions
 

It needs encoders. Encoders are usually a trivial thing to do, but on this particular design it looks like an idler sprocket, gear or wheel would have to be used?

Re: pic: Shifting Drivetrain with Transmissions
 

West Coast Drives typically put the encoder on one of the outer wheel shafts.

Re: pic: Shifting Drivetrain with Transmissions
 

So? WCD's usually do not drill/tap the ends of the shafts either, and that's the #1 thing which complicates adding an encoder to the outer wheel shaft. What would you do to mount an encoder?

For example, could one of the button head bolts could be replace with a hex head bolt, and that hex head bolt be drilled out to the diameter of a grayhill encoder shaft? What happens to the encoder if the bolt works loose?

Re: pic: Shifting Drivetrain with Transmissions
 

I don't know about other teams, but I know that we always drill the outer shaft for a 1/4" encoder shaft.

Re: pic: Shifting Drivetrain with Transmissions
 

We have a bunch of Grayhill encoders, so my plan was to put one on the back of the gearbox, and use a piece of surgical tubing as a shaft coupler between the gearbox and the encoder shaft.

254 puts one of the US digital encoders (the S4, IIRC) with ball bearings on the end of their outer wheel shaft, and just zip ties it in place.

Re: pic: Shifting Drivetrain with Transmissions
 

I'm going to guess that you drill out a hole in the axle then press fit a smaller shaft into that hole for the encoder to attach or do you guys just lathe down the end of the axle and use a collar or roll pin to keep the sprocket attached?
-Ronnie

Re: pic: Shifting Drivetrain with Transmissions
 

For encoders,

A handful of teams (254/1538/973/1323 etc..) have just drilled a hole at the end of the shaft, shove an encoder in there, and zip tie the wiring down.

http://puu.sh/bSXmC/4694259cf2.jpg

I would atleast snap ring the sprocket side and use a bolt/washer on the other side. If you don't have the resources you could always just buy the VersaChassis hex shaft:

http://content.vexrobotics.com/vexpr...awing-Rev2.PDF

Re: pic: Shifting Drivetrain with Transmissions
 

What's your experience with the 0.251 ream on the encoder bore? I've wondered how close of a fit we'll want, and we haven't tested anything yet. How easily can you insert and remove the encoder, and how well does it stay engaged with the shaft?

Re: pic: Shifting Drivetrain with Transmissions
 

Aren,

We've done a .2505 - .2510 ream for the past few years. We have never had an issue, most of the time we've been able to slide in and out with little force. We used to just drill the hole but switched to a drill + reamer to get a nicer fit.

We use the S4 with a ball bearing so there is very little drag.

Re: pic: Shifting Drivetrain with Transmissions
 

We've also had success drilling the hole out with a regular 1/4" drill

Re: pic: Shifting Drivetrain with Transmissions
 

Aloha!


Been away from the CD scene for a little bit. Turns out this thread is what our team has been working on for the off season.. So I thought it would be a good time to share it.

Transmission:
http://www.chiefdelphi.com/media/img...2202479c_l.jpg

Drivetrain:
http://www.chiefdelphi.com/media/img...40fec228_l.jpg

Here is our Tiki Tech Transmission and prototype drive frame.

The transmission plate is based on the awesome stuff from West Coast Products and Vex Pro.

This transmission is set up to run two motors on either side of the frame rail. We have designed this to use on our 2015 prototype drivetrain. It has enough clearance to go over our newly designed 1.5x3” chain and sprocket in tube frame. We have changed the mounting points to a much wider and easily accessible for quicker removal.

The system uses basically everything you get in a WCP 2 speed (DS) transmission. Plus one idler gear. Which is a duplicate gear of one that is already in the kit.

Great thing about it is that it uses any of the dog gear sets from WCP. Mix and match pinions as well, so you can get that speed ratio that suits your approach best. It is nice and compact at less than 3” (2.3 to be exact). With the pneumatics and encoder there is still lots of room in the center for use.. Battery centered is easily done!

It has an encoder mount as well. Which easily adapts to your preferred encoder.

Since this transmission plate uses WCP gears it is quite easy to setup. Just purchase their 2 speed transmission (or just the gears) and all that has to be done is turn down the input shafts to desired length (depending on if you are running the chain/belt in frame or not) and purchase the extra idler gear, input shaft and bearings. In fact when we turned down the input shafts, we just made one longer and let the one protrude past the bearing into the encode. That is how we discovered where to put the encoder mount it.. It can be done very easily with limited tools!

This new plate can be made as a solid plate or milled (as shown). Depending on your machining capabilities.

The second prototype has grooving along the outer edge for Lexan covers to keep fingers and debris out.

Questions or comments let me know, we love to hear what you think.
Enjoy!

Re: pic: Shifting Drivetrain with Transmissions
 

Looks like an awful lot of weight with that 4-gearbox setup - any particular motivation for that rather than a single 3-CIM gearbox?