In the event you have problems with the casters, you may want to consider omni-wheels from AndyMark. The omnis offer all the rolling/turning abilities of a caster, but with a larger diameter wheels and without the need for the caster to rotate in order for a directional change to occur. Heck, you can even run a chain up to them and have four wheel or six wheel drive… and they should be an incredibly simple retro-fit for your machine.
But if the casters are working… go for it.
Jason
NO CASTERS!!! WE LEARNED IT THE HARD WAY LAST YEARR
You people are scaring me like crazyy!!
I’m going to talk to my mentors and team leaders tomorrow and find out exactly how WELL these casters are working for us…
In the mean time, thank you guys forr the comments, always appreciated!
OH NO! Casters!
Sorry for the initial outburst. But Casters are not a pretty sight. If you’re not steering in the wrong direction, you’re dragging like no other. I’d say make a quick fix and upgrade to tank drive if you want the skid-steer thing going. That’s what my team’s decided to do.
Good luck convincing them otherwise. Perhaps redirecting them to this thread will change their mind.
To answer the question asked most… The bot weighs approx. 94 lbs. So we still have lots of weight to still play around with!
Muffinxo chill out thus far we have had little to no problems with our casters thus far!
Hey guys,
Castors are smooth, and will work well if you have some smooth programming skills. I know several teams that use them year in and year out. We are from central jersey, and I think team 56 (from a neighboring town) uses them every year. I hope I am not mistaken, but they work very well for them and they are almost always at the top of the rankings.
I would suggest practicing for the next week, and if you just dont like it, switch em out.
Also, you might want to consider some sort of ball grabber, I can’t see one, but maybe its just me not looking hard enough.
Good luck!
I agree with Jason in 2006 we had major problems with caster wheels and fixed everything by switching to omni wheels.
i’m gonna add to the no casters vote or at least in the setup you’ve got them in.
The main issue is you have no direct resistance to turning, if you had the traction wheels in the back you’d at least have the resistance of the inertia of the front of the bot.
i’d say either get traction wheels in the back too
or switch out the casters for omnis
nice, ya our team is also aiming for that sorta bot…
i like your your arm is,
how well does your ball catcher work?
our ball catcher that we are probly going to use looks so much bigger…
Okay so I totally talked to my team and we’re like PERFECT on the casters they are doing exactly what we want them to do and I saw the bot go down the hall at half speed today while they turned sharp corners and tried to stop really fast etc. and it’s all perfect. The bot moves amazingly (not that I recommend casters)…
The arm has not worked to it’s full potential yet because it hasn’t been welded down yet… but I’ll let you know how it works when we’re there!
Realistically, you can beat many of the problems with casters with sensors and programming. Throwing a gyro on there, with a PID loop to control rotational rate should keep your drivers happy, and you bot from freaking out when hit. Our team is going with rear omni wheels, and i’ve come up with a system that should eliminate many of potential issues. Also, with unmovable defense pretty much nullified this year, bot’s spinning each other out should occur much less.
Very impressive. I’ve always been a big fan of two wheel center drive. It looks like you guys have it down.
About the casters- In many instences, casters are not the greatest idea. Normally you see them on rookie robots with two up front and two driven wheels in the rear (the shopping cart method). This is a inherently unstable design and a real bear to drive. However, what this team is doing is very different.
If you look closely you’ll notice that there are 4 casters, one at each corner of the bot. In the ‘middle’, are two large wheels, presumably powered. These wheels will be slightly lower then the casters. The robot will be balanced such that the majority of the weight will center over these wheels. In other words, if you were to put your hand on the robot, it should slightly seesaw back and forth on the center wheels.
This is an excellent drive method for this years game. Unlike a 4 wheel drive train there is no scrubbing when turning. The robot can spin in place all day with no more strain or current draw then if it were going straight ahead. This means that the robot is very quick and easy to turn and has real neutral handling. Point of fact, it’s just like a Segway.
So how do the casters fit in? Well, unlike a Segway, FIRST robots aren’t quite clever enough to dynamically balance (somebody prove me wrong, please!). The casters just keep the robot frame off the ground. Other teams have used plastic skids or idlers in place of casters, but it’s really a matter of preference. Because there is so little weight on them and the drive train so efficient when turning casters won’t present any hardship. When turning the casters will either orient correctly or just scrub, but with out much weight on them it won’t be noticeable.
I think this will be the year of the center drive.
-Andy A.
Other center wheel drive robots:
I commend your team on a neat design!!!
You are much further along than many other teams…
If you can conquer the problems encountered with the use of standard casters… more power to you… just give yourself a lot of swing room around them and you can do this.
I would suggest that you use something called a ball transfer rather than a caster. Take a look at something like McMaster Carr part 6460K47
They have a variety of these… and they are much more resilient to the rigors fo the game than standard swiveling caster.
Although, if you guys are making it work…
GREAT JOB…
I hope you really do well in the competition…
Thank you Andy, I was relieved to see your postivie post! I think our team is very happy with the caters. I don’t know if I mentioned this before but they are spring loaded and yes the bot does seesaw just a tad.
About the ball transfer, I believe our team has looked into them before and had found out that they are not recommended for carpeted applications due to the fibers etc. that can get stuff stuck up inside the ball.
I want to thank you guys again for your input. We’re really excited about this years robot!
I’ve tried to stay away from casters for a long time. They tend to “kick” to one direction or another during slow movement. Simple delrin or nylon pads in place of the casters could be better. (Think of it like moving a sofa with those nice plastic pads underneath.)
I love the arm though, not sure why I keep thinking everything has to be straight.
hey, my team, 2026 (i think) is new this year, and were having a similar design, as far as the forks go. i was just wondering how good your bot controls the ball if you have tested it out. thanks in advance
Looks good, but how do you plan to get the ball off of the overpass, or put the ball up at the last 15 seconds?
I’m back! To answer some more questions!
For starters: We have fixed our problem with the steering being touchy! WoOt! I am SO 
happy about that 
! Our programmer fixed that!
Well Aren, here’s the deal, we have used omni wheels for the past 3 years (including the years as 1596) so we decided to do something different. We decided that casters would be the best idea in spite of the fact that everyone seems to hate them!
We haven’t had a chance to test it yet, because we found a problem with our arm. It did not have enough power:mad:! So we are doing some redesigning of it. But when we do I’ll be happy to let you know, Corcarter.
If anyone else has questions I check this thread daily and answer the questions if I have the answers from my team!
Have a good one,
Boonski
WOOT!!
i cant see very well because of the pictures angle, but is there a motor on the end of your arm there? obviously to dump the ball on the overpass?