Feather weight robot build question

Hi all,

This is my first post here, so be gentle :-)

I was at the leicester space center on the weekend and had the fortune to see a combat robot demonstration. This has kind of re-ignited my interest in the whole robot wars thing. My son is now at an age where he can join in and is also interested - with my son on side, I finally have an excuse to build my first combat robot.

I intend to build a fairly simple ram bot for the feather weight class, but would like to get some opinions before I start buying bits and putting the thing together. It would be made from steel tubing and armour, using aluminium internally where possible for other things like motor mounts etc. to keep the weight down.

Anyway - here are my questions

Motors and gears
obviously, rambots rely on speed so the right combination of motors and gearbox/transmission is important. What sort of motors should I aim for? I see drill motors touted around the forums as a cheap way to move a robot, but would they be any good in a rambot? Also - Gearboxs / transmission. Should I be aiming for motors with gearboxs, building my gearbox or would a simple chain drive be the best option?


Speed controller

Advice please - which make to go for..?

Radio Gear

27mhz or 40mhz 2 or 4 channel?

Rambots and anti-shock/vibration

If the mechanics are sufficiently secured, is this nessasary - are the magnets in
the motor likely to fall out? How are the electronics affected.

I want to build a robot that is competitive, so any advice would be appreciated.

Greetings Peter,
Glad you enjoyed the Space Center event, before you start anything please download and read the FRA build rules....

http://www.fightingrobots.co.uk/documents/buildrules2006.pdfhttp://www.fightingrobots.co.uk/docu...drules2006.pdf

These will answer a lot of your questions regarding things like radio, allowable battery types, etc etc..
Once you have got your head around the rules, Im sure there are plenty of people on this forum who will be more than happy to point you in the right direction.

great questions Peter, its obvious youve given this a great deal of thought, which is the first step taken already (a few people try to skip this step)

The best advise I can give you is to look at what the other good rambots have, and decide on which one would suit you best. For your first robot at least, copy something that works.

examples.

pillow torque - astroflight 940 with 15:1 gearboxes and vantec control. brilliant but expensive.

stiff breeze - 12v gold motors, over volted with 2 stage 10:1 (could be wrong ratio) and sidewinder control. good balance of power to cost.

one of tonys dragons - ev warrior drive, with gearboxes, not sure of ratio, sidewinder control. massive power, but heavy solution.

or drop me an email, as I sell complete drive solution, speed controllers, etc etc

good luck, and id speak to the rambot builders about you questions on shock mounting etc, as they would know better than anyone. contact me anytime if you want info on which bits to buy.

Hello Peter,

As far as radio is concerned, 40Mhz is the only option, as long as the Spektrums are not legal yet, and for a rambot you can make do with 2 channels (forward/backward 1 channel, left right the other), but if in a later stage you want to make a remote controlled weapon, a third channel would be needed, so its better to start off with 4 channels so you are set for the future.

As for speed control, there are various flavors, all in different priceranges. The best in my opinion are the sidewinder and the mini vantec, but Electronize and Mtronik also are very nice.

As for power, you can go to obscene amounts of power in a rambot, but if you cant get that power to the floor, it is of no use. So make sure you get some good wheels to match the drive train you want. James already posted some good expamples.

Have fun building and battling.

Hi there Peter - glad you enjoyed the event at the Space Center, the amount of positive feedback weve had from it has been overwhelming !

If youre starting out Id suggest starting at the simple end of the scale. Youll want gearboxes and motors that come as integrated units - all you need to do is fit your wheels on. Cheapest source of these are cordless drills http://www.gimsonrobotics.com/electricmotors.htmlhttp://www.gimsonrobotics.com/electricmotors.html is a good source, most expensive source is http://www.robotcombat.comhttp://www.robotcombat.com (Astroflight 940Ps). Either way start simple, you can always upgrade later.

Speed controller - for out of the box usage Id reccomend a Sidewinder which you can buy from James Baker above. http://www.robotpower.comhttp://www.robotpower.com for details on that.

Radio gear - yes 40Mhz is the way to go.

As for shock mounting, yes youll need to think about the shocks but for a general rule make sure you can pick your robot up by any other part of the robot (and that includes batteries, motors and speed controllers). If you can do that you should be on the right road.

Youre bound to get plenty of information from the builders around here on what to do !

Welcome to the family ;)

Ed
http://www.teamstorm.comhttp://www.teamstorm.com

As mentioned above really, drill motors are a very simple an very effective source for drive. Ewan Gimson sells them at a good price, and he overvolts them in his robot at 18v giving him a very good reliable system (using the sdewinder speedcontroller). I guess you are looking at 4wheels drive? If so, then the simplest method of using all four wheels is probably to use four motors(wheels directly onto the motor gearbox)-espcially when a set of pulleys can cost more then the motors!
I would recomend using a 4channel 40mhz transmitter (futaba is always a good choice)as this will give you the option to add a weapon at a later date.
almost everything except the motors are now shock mounted in my robot, using rubber gromets for speedcontroller/baseplate mounting, and neoprene(or any good rubber/foam) for surrounding my batteries. Since i did this my robot has become MUCH more reliable.

Good luck

I shall be getting my act together with the new Gimson Robotics website asap which will stock a range of new products ideal for your machine Peter!


To answer your queries so far:

Drill motors are an ideal budget drive solution, and drop the requirement for an external gearbox as the one provided is perfectly adequate (though in some conditions it may be best to exchange the first stage gears from plastic to metal as used on the second stage). There are also wheels available which will screw directly onto the output shaft of drills shafts and would be ideal for your use.

The speed controller(s) will often be your most expensive purchase and so making the right choice is paramount. I happen to have a fantastic low-budget solution up my sleeve for the near future so your choice may depends much on what dates youre setting yourself for this build.

40mhz is the best radio control option. Two or four channels depends much on how you see your designs expand in future and your current budget - it may be worth investing in a four channel model for the future.

The motors and electronics typically used are pretty well adept to impacts, Ive never personally come across a magnet issue with drills for one thing. It is adviseable to mount electronics with shock absorbing materials such as foam or high-strength velcro.



Please dont hesitate to ask any further questions!
_________________________________________________
Many Thanks, Ewan

Electronize speed controllers (with external relays),drill motors, 40 MHz radio and Nicad batteries. James sells excellent wheels which wind on to the thread of drill motors (just ask for grippy blue wheels). Good luck. Its not hard.

Hi all,

Thanks for answering my questions. It seems drill motors are the favorite for my first machine. Im a great believer in learning to walk before running.

Another question - a bit premature as I havent bought any bits yet, but solder or crimps? I previously worked as a hardware technician for a company that got involved with electronics and electronics that moved. We found that one of the main failures out in the field was due to metal fatigue on the solder joint - but not where the solder met the PCB, where the solder finished up the wire - not sure if it was due to the disimilar metals or because the solder was stiff and the wire was flexible creating a stress point. Does anyone have an opinion?

Cheers

Pete Curtis

I believe a lot of roboteers like to use crimps as it is an easy way to remove the batteries, speed controllers etc when there is a problem, but these can over time fall off leaving the robot dead in the water, so i personally prefer to solder want i can.

p.s tidy wiring is always a plus

Wayne

but dont overheat the motor brushes, batteries, or speed controller when soldering or you can do £££s of damage.

in other words, only solder if you know what you are doing, and DONT, (like someone whos name I wont mention) SUPERGLUE your battery cells together!!! Yes, someone I know was that dumb, and no, they didnt work.

Peter,
Unless you have no other option... solder every time!!
What you discribed sounds like a problem with the wire rather than the solder it may have been a fairly stiff steel stranded cable that failed due to work hardening at the solder junction. We use an extremely flexible, pure copper very high strand count silicon rubber covered wire that goes by the wonderful name of wet Noodle in all our machines http://www.robotmarketplace.com/marketplace_wire.htmlhttp://www.robotmarketplace.com/marketplace_wire.html
We have never encountered the problem you discribe, but to be 100% safe you would could provide some sort of strain relief at the solder conection to hold the cable still reletive to the joint and allow any movement to be absorbed by the main body of the cable run.

(On the other hand you could just wire up the whole machine to NATO milatary standard using Raybraid 101 steel braid sleaving and be done with it!:wink:)

dont get me started on the wiring of NATOs Tornado, talk about time bomb waiting to happen!!! :)

i would also suggest regular inspection, as everything in a robot can come loose, so keeping on top of them, such as a good look inside with every battery charge, can help to gradually eliminate these types of problems as they start to occur. Im sure youll be fine though, as you already have a really good grasp of what you need to be doing.

A good crimp is always better than a solder joint, however you need both the right tools and the right materials to get a good crimp. Soldering often produces better results.

As suggested, soldering can induce a stress point, but this is rarely ever a problem, properly fixed cables wont be moving.

crimp it, then solder it, then duct tape it...
then duct tape it again... just to be sure

For my drill motors I crimped the connections (so it would be easier to remove them if I burnt a motor out) and then put a layer of hot glue on them to make sure any hits wouldnt dislodge them easily. Two months later though when it came to removing my motors, it wasnt too difficult to pull the connectors off - so maybe not the best solution! :lame: