Robo-Cross B

[WrightStuffMonster]

The design and testing of the robot is way way way more important than what yoru materials are in robots. That said expensive parts do give you some advantages. The thing I like the most about them is that they were very reliable to the point that I did not have a single part on my robot fail last year except one (which was replaced under warranty) and they can be faster and more precise. That is a really good record considering I spent at least a couple hundred hours testing the robot. I dont think a robot made out of vex could have beat my robot last year no matter how good the design was and how experienced the testers were.

If you use lego mindstorms I suggest you glue the blocks together or something. I have seen some pretty dramatic break ups before.
What is the best time anyone has seen for full points?

[computernerd4826]

The design and testing of the robot is way way way more important than what yoru materials are in robots. That said expensive parts do give you some advantages. The thing I like the most about them is that they were very reliable to the point that I did not have a single part on my robot fail last year except one (which was replaced under warranty) and they can be faster and more precise. That is a really good record considering I spent at least a couple hundred hours testing the robot. I dont think a robot made out of vex could have beat my robot last year no matter how good the design was and how experienced the testers were.

If you use lego mindstorms I suggest you glue the blocks together or something. I have seen some pretty dramatic break ups before.
What is the best time anyone has seen for full points?

what did you use?
also, what times did you get last year? because the robot that did win was vex
was this for ramble or robo cross ( i can see that you are div c now)

[WrightStuffMonster]

what did you use?
also, what times did you get last year? because the robot that did win was vex
was this for ramble or robo cross ( i can see that you are div c now)

You can see pictures of my robot in the scioly image gallery under WSM robot in the Image Gallery
I am not particularly proud of the construction (it looked pretty ugly) but it was pretty functional despite looking like an ugly duckling.
Highlights include:
A 2 channel 25 amp speed controller from Dimension Engineering that I choose for its regenerative braking and built in current protection and protection for Lipo's http://www.dimensionengineering.com/Sabertooth2X25.htm

The robot had 5 of the 36mm planetary gearboxes (16:1 for drive and 125:1 for lifter) from banebots for driving and the lifter with the stock motors replaced with lathe motors (35T for drive and 85T for the lifter) http://banebots.com/c/MP-36XXX-540

All of the servo are Hitec digital and most of them are the Al or Ti geared versions except for the JR digital servo i used for the sweeper. http://servocity.com/html/hitec_servos.html

Other highlights include all aluminum and carbon fiber for the chasis, servo brackets from lynxmotion.com for the arms, a Castle Creations Mamba Max motor controller for the lifter http://www3.towerhobbies.com/cgi-bin/wt ... XUTA3&P=FR, a 7 chan Futaba computer radio, a 6 channel Airtronics computer radio, 2 5000mah Lipos, and dual 5 amp switching regulators to power the servos.

All of this cost me a fortune and I pretty much emptied my college account/life savings to do it all but I think in the end it was worth it. (makes for good college essays) While it all seems like overkill it all made sense at the time and usually I only upgraded after something died. For example the only reason I used a $130 motor controller on the lifter was because the motor on it had to go into lock/stall conditions during the run and the previous two controllers I had could not take the abuse. Another nice thing is that the parts can be reused for other robots.

Sorry I am refering to div C from last year. I did robot ramble not robocross sorry for any confusion. My time at nats was 29 and my best time was 15 with average runs around 22. Here it is one youtube http://www.youtube.com/watch?v=6dXXDX4zF8k

[captbilly]

Is there a limit to the number of batteries that you can use this year. Last year there was only a maximum voltage limit, not a limit on the number of batteries. We used two 7.2 volt batteries plus a 4.8 volt battery on our Nationals robo and made a special point to tell the event coordinator that there were this many batteries (and that they were not in series so no circuit got more than 7.2 volts.) and were not DQed.

I also want to throw out my oppinion of the VEX stuff. Electronically it may be OK for what you want to do but mechanically it seems pretty junky to me. We used VEX for our regional and state competition and did pretty well, but it was definitely not reliable enough for Nationals use. I can't even count the number of gears we stripped and motors we broke with the VEX. I like to use a motor or sevo that will not break even when stalled, and the VEX stuff definitely cannot be counted on to hold up to anything like a stalled condition (unless you severely limit the current to the motors). In addition the tolerances on the bearings, motors, gears etc. are pretty coarse and there is lots of play in the parts. I don't doubt that a reasonable robot could be built with VEX but I would be curious about how many top 10-20 teams used VEX at Nationals.

vex did just fine for us, and we won nats.......
we used clutches on the motors, and all year we only stripped one clutch.
also, the only problems with gears were a few teeth breaking of now and then, because we had an insane gear ratio with a lot of gears (it was slow, but strong) and even then it only happened when we lifted the scoop while going into zone d because the weight bounced around and put more force on it. in about 300 runs, we broke 5 12-tooth gears.....
in my opinion, vex is one of the strongest kits that you can buy

I guess you have a very different threshold for reliability then I do. You broke five 12 tooth gears and stripped one clutch in 300 runs and you are OK with that? That is more then a 1% failure rate per run. What would you have done if that failure was during your Nationals competition? As I said, we did fine with VEX also, but we broke a few gear trains on the "motors"(probably less than 5), and were unhappy with the general fit and finish of the parts. I would want to use something that isn't going to break even 1 time out of 300, much less 5 times out of 300. On the other hand VEX is very easy to work with and very easy to get, perhaps that more then offsets the few parts failures that you had.

[WrightStuffMonster]

I guess you have a very different threshold for reliability then I do. You broke five 12 tooth gears and stripped one clutch in 300 runs and you are OK with that? That is more then a 1% failure rate per run.

1% failure rate for the mechanicals is nothing compared to average robots operator failure rates for most robots. I would imagine that it would be much more likely that he would have messed up driving than his robot dieing mid run. I would bet that most of the top 6 teams at nationals every year in both robocross and robot ramble mess up at least 10% of the time. Vex is probably the best way to start out with robo cross if you dont have much experience.

[computernerd4826]

I guess you have a very different threshold for reliability then I do. You broke five 12 tooth gears and stripped one clutch in 300 runs and you are OK with that? That is more then a 1% failure rate per run.

1% failure rate for the mechanicals is nothing compared to average robots operator failure rates for most robots. I would imagine that it would be much more likely that he would have messed up driving than his robot dieing mid run. I would bet that most of the top 6 teams at nationals every year in both robocross and robot ramble mess up at least 10% of the time. Vex is probably the best way to start out with robo cross if you dont have much experience.

thanks WSM
the teeth that broke didnt even disable the robot
that is why it wasnt a concern
the dumping mechanism would go down a little and keep going back up it would only drop every one rotation of the gear
it would have added time, but if it was that big of a concern, we would have machined metal gears
as for the clutch, it was at the beginning when i didnt know the machines limits

[robotman]

the only issue ive had wiht vex is my arm falls off occassionly

[computernerd4826]

that might not be very good....

[robotman]

yea i fixed that problem had to tighten some screws

[madscientist]

i already quit this event it is SOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO hard trust me take another building event