Drive train and gearboxes

Hello all,

I’m a West-Windsor plainsboro HSN(NJ) team 1923. This is my team’s first year so none of us are experienced. I have a few questions:

-The chassis video is 2005. It shows the drive train with 4 of the smaller CIM motors. We have been provided with 2 of the smaller CIM motors. IFI kitbot shows us a way of building a drive chain with 2 wheel drive for this year. Is there any way we can build a 4 wheel drive with the materials of the kit only? We have no money (we’re in debt) and we have few experienced people.

-If so, could you show me how?

Thanks,
Naveen

with the purchase of some sprockets, you can make it a 4 wheel drive using the kit transmission and one CIM. (look in the good practices portion of the manual, section 5) The only disadvantage is most teams will be using 2 CIM per transmission. Theh kit is really optimised for a 2 wheel drive system. You can try posting to the CD swap for some of the additional parts that you need. I know that alot of veteran teams end up with a lot of parts hanging out on the shef.

at the very least to get a 4WD drivetrain on your robot, you are going to have to purchase at four more sprockets to get power to the other two. we solved that problem last year by getting power to one set of wheels as shown on the video, then bolt a second sprocket to the wheel that has power and put a sprocket on the other wheel that has no power. then run chain from the transmission one of the wheels, then from that wheel to the other.

the kit only provides enough sprockets to do a 2WD, at least as far as i know and can imagine.

i hope this isnt too confusing.

**also remeber that the KOP is NOT an erector set type deal, it’s just enough to get you started and on your way, but by no means “all that you need to build a robot”

good luck :slight_smile:

I’m not sure if this is possible, but I’m trying to offer help.

The kit transmissions need 2 CIM motors each to run efficiently. I think that you will need to aquire the 2 additional CIM motors to have the Kitbot that is assembled in the video you watched. I’m pretty sure some of the more veteran teams can spare two CIM motors if you are in debt. Just ask!

Also, there is a conversion kit for the transmissions that you can purchase that will allow the transmissions to use the Larger CIM motors provided in the kit if you would rather go about that route.

Hope this helped you out in some way.

Hello Veteran teams,

Can any of you spare some chain sprockets and two CIM motors? Thanks!

Naveen

I helped when our team did this same thing last year and it worked great! very reliable and sturdy once we got it up and running. If i remember corretly there was a lot of lithium grease involved in that process. One thing that it did with the 2 motors per gearbox was it made a lot of noise from the gears grinding. due to somewhat poor design when 2 motors were used they would naturly spread apart putting pressure on the gears and not aligning them correctly. to achive 4wd we used a idler sprocket and a chain design that is very to explain. but it does use A LOT of chain so it may not be very cheap for a new team. since it is very difficult to describe the chain pattern if you are intrested email me and i will draw it up it paint to give you a better idea.

This is not true. They will run perfectly fine with only one CIM per side. You just lose the advantage of having extra torque and being able to share the load between motors.

Thanks for the clarification and correcting me. I knew that they would run on one CIM motor, just wasn’t sure of the advantages/disadvatanges.

Hope that helps. albeit, we arent one of these $9,000 teams, but we are much closer to that then these $50,000 teams that are few and far between. I would recomend this solution if you want to have a 4 wheel drive robot. I am unsure whether or not this configuration will be great at making it up the ramp myself, I have not tested it out yet. Good luck and have a great season.

JT
229

We are a “have not” team. We have $9,000 this year, which is the most in our team’s three years. The advice you get from most of the $50,000 teams just won’t be relevant to you. Here’s my realistic advice for a rookie team with really tight finances:

  1. Don’t sweat the 4WD and 6WD and holonomic and every other kind of drive train arguments. I’d build what we did last year: use the kitbot chassis, mount the transmissions and motors near the center, and drive two of the 8-inch Skyway wheels that came in the kit with short chains. Put two hardware store casters (non-swiveling) on the front. Put two more non-swiveling casters on the rear. Set the casterheights so that either the front or rear just barely touches the floor. You want the weight off one of the sets of casters just enough to make it barely touch. You will be fast, maneuverable and reliable. You won’t win pushing matches, and won’t be able to get up on the ramp. It’s a straight-forward design that will serve you well, and won’t break.

  2. The KOP transmission works fine with two CIMs. We ran ours like that during testing last year, and only added the other two when we were underweight. Our top speed didn’t change, and since we enthusiastically avoided contact, we are pretty sure the extra two motors didn’t really make much difference.

  3. Avoid contact during your matches. Your first-year bot will have enough problems without worrying about making a bullet-proof chassis. You will get more recognition by showing up with a working robot for each match than by smacking other 'bots around. Finishing every match while contributing to your alliance is a good realistic goal for a rookie team.

  4. Look for an experienced team in your area and ask them for help. I can’t tell you how many teams have helped us over the last two years. As a third-year team, we are just now experienced enough (and have a couple or three tubs of old parts) that we could help another local team.

  5. Use all the KOP parts you can. Don’t get obsessed with high-tech solutions to your problems. Pick one function and do it really well, and remember that baltic birch plywood can be used in a lot of places that others will use Lexan or aluminum, and it can cost a LOT less.

Most of all, keep reading Chief Delphi and working on your robot.

Rick Tyler said
"I’d build what we did last year: use the kitbot chassis, mount the transmissions and motors near the center, and drive two of the 8-inch Skyway wheels that came in the kit with short chains. Put two hardware store casters (non-swiveling) on the front. Put two more non-swiveling casters on the rear. Set the casters so that either the front or rear just barely touches the floor. You want the weight off one of the sets of casters just enough to make it barely touch. You will be fast, maneuverabl and reliable. You won’t win pushing matches, and won’t be able to get up on the ramp. It’s a straight-forward design that will serve you well, and won’t break.
"

I saw it in competition. (I’d say we competed against it but that wouldn’t be accurate :slight_smile: ) It ran very well. On a flat carpeted field you have many advantages to this type of design.
You Won’t be able to get up the ramp though, But if you can stop the other side for getting just one robot up you will “pay” for that loss by preventing the score against you.

Get something running ASAP and practice practice well you get teh idea.
A below average robot with a practiced driver is worth much more than teh right robot with a nervous, untrained driver.

Rick is right.

You will have very positive experience if you are running. You’ll learn about making a FIRST robot from now until… forever. But running and practice are more important that you (at least I) could ever imagine.

Good luck!! And have fun!!

I would like to second, no third,no fourth, or whatever it is what everyone has said. PRACTICE. Our driver last year only had 2 days of practice with our bot :ahh: . they spend all of the regional just learning to drive. After the region and at an off season comp, we placed second at battle cry. Practice does count for something.

You don’t actually need four sprockets on the tranny to make a 4WD. We had a 4WD last year that was so effective, the first time we lost a pushing match was at nats by a tank treaded robot. (can’t remember who) We mounted the tranny in the center of the bot than ran one chain around it and the two wheels, than had idlers (literally HDPE blocks) that performed double duty as tensioners and gave us enough contact on the tranny to avoid slippage.

Although using a single loop of chain to power a four-wheel-drive robot may seem like a good idea (especially in the weight department), just remeber that “stuff” happens. At some point, that chain may break. If this said chain broke, your robot will basically be a paper weight for the remainder of the match. However, if you were to use two chains from the transmission - with one going to each wheel - you could still have at least one powered wheel if the chain broke. Thus, your robot could still “limp” through the rest of the match and try to score as much as possible. Redundancy is always a nice feature to have. :slight_smile:

http://www.team228.org/images/2005/Championship/drivetrain.jpg

Yeah this happened to us a couple of times at VCU. (loose chains) Hence our motto on TIMS is “Sometimes stuff just happens… oops.”