Answers on a postcard.

[Roadrunner]

Greetings fellow hermits.

I have some questions.... but first off let me tell you i'm no stranger to building mechanical devices, although my machines are those quite a bit more delicate.

I've spent many years in the Rc car areas, building, racing, modifying more so in my much younger days today its more of knowledge is there but no desire to take up that again.
I guess as age starts to creep in, family's grow and take over for those who still want to have a hobby you need to find a niche that fits without taking over, mine now being building model boats something I've been doing now for a little over 15 years.
If anyone is interested in my projects past and ongoing then you can follow my content on my own forum... http://www.thercmodelboatforum.com/ my username is the same here as there. (In no way is that an advertisement, admin feel free to remove the link if it violates such T&c's of this forum. i only hope to prove my ability's and knowledge in these fields sharing similarity's)

This for me isn't a change in hobbys by any means, ( my Passion for fine scale boats is my life) nor is it a whim given the new series of robot wars to think i can just 'ave a go'.
My actual interest has been there for many years since i was in my early 20's and its something i just didn't really pursue ( when your that age drinking, girls and well spending money on pointless rubbish made more sense)

Its actually my eldest son and daughter who have taken more of an interested then me so much so that they have pestered me to the point of where i'm here now making an effort to for-fill their little dreams.

So here we go... my kids have a few ideas they want me to build for them as a combat machine, either a spinning weapon machine much like the drum's or that of a flipper bot. ( i guess we'll decide better with some first have information and much research over the coming winter months.

Keeping to some sensibility i want to keep this machine in the light weight category, making it easier for me to work on and transport. my kids want to drive it and control the weapons on their own terms in battle, i'll just be the mechanic and the taxi to events!

Now my questions begin... feel free to correct any mistakes or misinformation i may provide in my questions, i am a boat builder so questions will be based of knowledge on how boats use electronics and may not be the same for robots.

First up is after reading those many posts, it comes to my attention a lot of people are opting for drill motors as primary drive for either 2 or 4 wheel machines...

Anyone's thoughts to use planetary gearboxes? given that they are vastly more efficient such as these linked here
http://cpc.farnell.com/mfa/949dra516...97?CMP=CPC-PLA
They operate using a standard 540 motor and gear box ( gear reduction can be changed as with all MFA geared motors, that's from experience owning several types) is it a cost thing given their prices,not much knowledge or is it they are unpractical for the job at hand?

Second question is about ESc's ,most 540 Brushed motors amp draw is 11 at initial start up dropping to around 1-2 amp continuous draw,(regardless of gear ratios added) is their a reason why its recommended to use 85amp esc's for each motor? I understand stall ratings but also know from facts and usage of such motors 540's when stalled under load will draw no more then 20 amp which makes me wonder why much larger esc's are used when a 20 amp esc is more then suitable, surly this is just asking to burn out the motor much faster, it certainly wont give you extra RPM?!?!

I didn't mention brushless here for drive as i have no intent to use for this project since its for the kids to combat with rather then me going full throttle at this.

Third, approximate sizing of the machine min- max- average? suggestions would be appreciated to give me a better sense of size i would be looking at building this machine into, knowing some items will use a lot of the allocated 13.6kg weight limit so an over sized robot will undoubtedly make an overweight and unusable machine.

Forth, Armor options, Steel, alui, hardox, HDPE, others i undoubtedly missed, what are people using and what thicknesses for each materials work well? using mix and match?

Ok i've yacked enough hopefully i haven't come across like a right dick, look forward to reply's, more questions to come over the coming weeks i'm sure, and Thankyou for responses in advance.


RR

[daveimi]

Most cheap drills use a 550 12v motor with a 2 stage planetary gearbox built in, hence why they were once popular. A company used to make wheels that go straight on but they've stopped doing them. There are a ton of threads just like this with all the info in.

The best thing to do is go and watch a live event and chat to people, then read through the build threads and feather forums. Gives you a brill grounding before you throw money away cause it gets expensive quick.

[daveimi]

Hi, me again, sorry for the double post but it's early lol. Not a morning person. Was just going to say that I came from RC Car back ground and am rubbish at fabrication. I basically build wooden boxes with scoops on of one form or another, but have got to the stage where they are doing reasonably well. I've been entering the beetle stuff but been looking to have a go with the feathers again as the beetle events have been non existent here oop norf.

I don't have a problem with with the electrics as its basic, just battery, speedo, receiver and motors just the same as in my losi buggy except there's two motors coming out of the speedo instead of one. I have two main bits of advice for you to be honest that I **HAD** to tell you lol. The first is build a pusher/wedge/bulldozer for a first time round, and the second is that which ever drive train you decide to use, order it as a package. By that I mean if you are useless at machining and fabricating accurately then making your own hubs is hard.

I have aspergers so I don't have the accuracy to make hubs up, so I order gearmotors, hubs and wheels almost as a package and it's been really reliable. I used to use drill motors and then by the wheels that fitted, but since they've stopped doing them I struggled making my own. I'm building a feather using some untested low powered motors as my new robot is a thwack bot and doesn't need much shove. I like the beetle class because it's huge in america so all the stuff is readily available off the shelf. You can even by a kit for a drum robot for a couple of hundred and it comes with most of the stuff you need.