The team we’re mentoring stopped by yesterday and I found myself giving them a lot of tips for the KitBot. I’d like to briefly outline them for your viewing pleasure:
Use loctite on all bolts. The 1/4 20 nuts do have lock-washers, but we’ve found that because they are coarse thread and because the frame is brushed, they still come loose quite a bit.
Read the instructions: You’re missing a few things that you can pick up at the hardware store: bolts for wheel hubs, pvc for spacers, 3/8" bolts and nuts, etc.
Use Grade 8 or 9 bolts for the axels to prevent bending/breaking. Most hardware stores carry higher grades.
Cover the extra hole on the transmission boxes to prevent junk from going in there. Duct tape it for now, find something legal latter.
The compressor can be mounted upside down between the motors, attached to the motor bracket plate. Be sure to use red loctite though
The plates that attach the transmissions to the chassis tend to slip because the drive train is powerful. Consider adding a bolt through a new hole in the plate (i.e. so that there’s no way it can slide) - but do this after you’re sure you have it in the right place (plenty of chain tension).
The gearbox was designed to optimally run with 2 CIM motors per gearbox and I strongly recommend using 2 CIM motors per gearbox. It is legal to purchase 2 more CIM motors and they are only $28 from IFI. (From Paul. Thanks!) Also, consider asking other teams (veterans) if you cannot afford more motors this year.
there is a video that illustrates how to assemble the transmissions and chassis, thanks to NASA…Chasis and transmission assembly video (From Vince. Thanks!)
Consider placing extra material over the bolt holes of the axles. This will help prevent the holes from wearing out and expanding. Basically, just take some flat aluminum extrusion and bolt it over the hole. Then redrill the 1/4" hole for the axle. (From Nitroxextreme. Thanks!)
Once you have the transmission boxes made up, run them for 10 minutes with a little oil. This will break them in and produce better and more consistent results. (From Andrew. Thanks!)
I think that’s all, if I have more I’ll add them or if others have more to add, please do so.
(Note: I did not yet add welding because there is valid debate below about whether it’s a great suggestion.)
The gearbox was designed to optimally run with 2 CIM motors per gearbox and I strongly recommend using 2 CIM motors per gearbox. It is legal to purchase 2 more CIM motors and they are only around $24 from IFI.
Reinforce the axle holes by bolting on another piece of metal so that you will have 4 pieces of metal the axles go through not only 2
2 although it seems strong enough wont be…last year we didn’t reinforce and after the season we had to create a new mounting bracket for the axles because the kit-bot holes were at about 150% normal size
The gearboxes can be very good, but be sure to assemble them with plenty of LockTite. If you don’t, they will comeaprt, and they will jam. We had this happen a couple of times, and total, from three gearbox jams, we found five pieces of loose hardware inside. For some reason, the stuff in there is attracted to the gears.
Also run the gearboxes in for about ten minutes straight. They’ll run a lot better for it.
Use caution when welding the frame. The heat from welding can distort and weaken the frame. I believe it can actually destroy the heat treatment of the frame and cause the weld to be the weak point in the frame. Also, a super rigid frame may not be a good thing. I believe the kit frame was designed to flex a little across the corners for a reason. Sort of a built in suspension. To reduce the weight of the steel fasteners in the kit frame consider using 1/4" aluminum rivets. They are strong, light and can be removed and replaced if needed.
We assembled the Kit Bot for early program module development, but are having troubles with traction with the stock wheelchair wheels. I suppose this is from a combination of low robot weight (bare minimum for bot to run mounted), and running the bot on a slick tile floor.
Does anyone have suggestions on how to get more traction from the stock wheels? We are planning on adding more weight over the driven wheels tomorrow, and possible putting zip ties around the wheels.
I think the zip ties will be counter productive if you are trying to increase traction. Chuck up the wheels in a lathe and turn the “crown” off to make them flat. Cut some grooves across the face of the tread. If that isn’t enough wrap some better traction material (wedgetop/roughtop) around the new flat wheels and glue it.
[ul]
[li]Try different configurations!!!-Particularly with the chassis[/li][list]
[li]Your robot can easily turn much better if you have wheels on shorter side (28") and then use the Longer beams for your Width (38") The further you get away from that, the harder its gonna be on your robot to turn.[/li][li]Drive Train Basics[/li][/ul]
[li]Review some of the documents IFI published, from their design process to their analysis after last year’s usage of the kit chassis/gearbox[/li]
[ul]
[li]Chassis Design Process[/li][li]Drive train Improvements (its a really good review of the 2005 Kit Bot, which is just about the exact same thing), side note, its one of the most interesting documents I have read in awhile.[/li][/ul]
[li]They mention it a few times in the Assembly manual, look into using the kit gearbox in the “Arm” Configuration, you never know you may get something handy out of it.[/li][li]Worried about nuts and bolts coming out and your bot falling apart? Use a lock washer and a Nylon Nut, its a great alternative to lock tight, and i’ve yet to have a problem with it.[/li][li]Most of all, have fun with the Kitbot[/li][/list]
Two suggestions one for general info http://www.usfirst.org/robotics/2004/Workshops/champwork.htm
check out the drive line ppt’s
The second is conveyor belting. The gum rubber variety is a First staple. You can get more info from the IFI site they make the controller and also some new bolt together wheels which you pop rivet the belting to other wise teams get the wheel chair wheels lathed flat and glue the belting to the outside. Also try a search of the forums here, Hope this is helpful.
Make sure you test the robot on carpet. Our first year in the competition we had these beautiful, big pneumatic tires that worked great on the cement floor in our shop. When we got to Toronto we discovered… that our 4x4 drive couldn’t turn worth a darn on the carpet! We solved the problem by reducing traction on one set of wheels by wrapping them in hard plastic duct work held on by zap straps/zip ties. Last year we did 4x4 again, but with pneumatically activated casters on one end. It would have been easier and lighter just to put omni wheels on one end.
This year… 6x6.
Jason
P.S. Skyway has some nice pneumatic wheel/tire combinations.
