Need a bit of help - EPQ project

[Flag Captured]

Hello all, I'm pretty new to the whole combat robot thing though I've been watching Robot Wars/Battlebots for as long as I can remember. I'm 17 so my school's opened up an 'EPQ' project to me which essentially is 'do something and get an AS-level from it' but the catch is that we can't do something we already know about - we have to learn about it from scratch (or at least, that's what they told me).

Long story short, I've gone for a project revolving around a featherweight build, and I was wondering if anyone would be kind enough to help me with a number of things with it, mainly the wiring and internal stuff - I've already got a design worked out that's kind of like Tornado or Storm-II (Simply because I'm a complete novice with combat robots, but have done a bit of RC-Car stuff in the past so I thought I'd go with a ram-bot).

The project title I've come up with is Is it possible to make a competitive combat robot for less than £150? (Well, give or take a bit) and I'm just wondering if anyone knows any way I'd be able to achieve this, or if I've bitten off way more than I should have here...

And again, I'm a complete novice to this, the only thing I've done is taken a basic RC device/circuit thing and made a robot with forward drive only (Only have one motor/speed controller, see) so I've got a lot of stuff to learn, but I've been told this'd be a high-grade project if I can pull it off...

So yeah, couple of things - Would anyone be prepared to show me how to wire up my robot so it doesn't catch fire or something, and also show me the best parts to buy on a budget?

Thanks a lot for reading as well!

-Matt

[plargen]

Re: Need a bit of help - EPQ project

this is a good start on how to build http://teamorr.com/how-tos/how-to-build ... ght-robot/

cheapest motors are drills generally argos or you can find some bare units on ebay

[plargen]

Re: Need a bit of help - EPQ project

battery ... either ebay or http://www.vapextech.co.uk/acatalog/Hig ... eries.html and http://www.component-shop.co.uk/html/large_packs.html

[Anttazz]

Re: Need a bit of help - EPQ project

Wish I could have done something like that when I was at school

Anyway, welcome! Keeping it simple is a great idea, and you can build yourself a 4WD rambot no problem at all If you're trying to make something as cheap as possible though, you'll probably want to limit the number of components to as few as possible, so maybe a 2WD rambot would be a good idea? Similar as it'll save about £25 on 2 extra motors and about £10-15 on wheels.

I'd get myself a set of the Argos drill motors (£12ish each) suggested earlier in the thread and cannibalise them for the motors, and if you're trying to demonstrate how inexpensively you can do it you could use the batteries from them too. If you ever were to compete you may want to change the batteries for a set suggested earlier in the thread, but that will add more £££ to the total and if your main objective is to build something for little money and not build something extremely effective then that'd be your way to go, to begin with at least.

Your most expensive part is probably going to be speed controllers (ESCs), not sure how your project is going to work on keeping track of cost, but you could put an advert up on here and get them second hand (might be cheaper but if you're keeping track of costs new it might not be so good) or the cheapest ones at the moment I think are either Blue ESCs (ebay marine esc to see what I mean) or the new BotBitz hacked brushless speed controllers (http://www.botbitz.com). Could maybe even have a go at hacking them yourself if you have the equipment in house, might give you extra credit. If not buying them is almost as cheap, could probably get away with the 25A version.

As for wiring it up, I don't want to do your project for you but if you get all the components you're going to use and draw a wiring diagram of how you've wired them up then either post it here or PM it to me or something then i'd be happy to give it the once over.

For radio gear, I assume you have your own if you do RC racing?

[Ellis]

Re: Need a bit of help - EPQ project

First off, welcome to the forum!

It is certainly possible to make a decent robot for under £150. You'll have to be clever with parts, though, as sadly, this ain't a cheap hobby.

As has been said, you will probably spend the most on control. Basic 4ch radio gear (must be 2.4Ghz to compete) can be had for as little as £25 - http://www.giantshark.co.uk/giantcod-24 ... 03779.html - If you go for second hand you may get away with even less.

ESCs are preferable but they aren't necessarily your only option. There are ways using microswitches and servos that give you non-proportional (hence less preferable) control, for much reduced cost. A tutorial on this can be found here: http://www.youtube.com/watch?v=E9EaenXANGQ - another disadvantage of this is that the system won't failsafe, and you wouldn't be able to compete unless you used a separate failsafe (all starts getting more complicated than you need!)

As for cheap ESC options, I have (and many if not most on this forum do too) very positive personal experience with Electronize (http://www.electronize.co.uk).

What ESC you go for depends on the demand from your drive motors. You can make a perfectly viable pushbot with 4 cheap drills. If you have a good design you can with just 2. Our first robot had 4 cheap 12v drills over-volted to 18v with 100mm diameter wheels and it worked very well for us (so well that we're reusing the very same setup in our next machine). We used two 30amp type Electronize ESCs (as against to the less capable 15amp models, for safety), 1 for each side; two motors each.

If you don't intend to fight it, you could build a plywood chassis for very little money, use wood screws and homemade wheels, etc. If you wish to compete, wood isn't advised, instead you might want to look into a tough plastic like HDPE or Nylon, found here for example: http://www.directplastics.co.uk/

Battery-wise, as has been said, you could use the cells that come with the cordless drills, as we initially did with moderate success. Or you could opt for a cheap (and heavy and bulky!) 12v SLA (sealed lead acid) battery, or some sort of slightly more advanced NiMH pack such as the ones posted above.

-------------------------------

All of what I just wrote is subject to whether you intend to actually fight this thing in anger or use it to bash about a classroom. A wooden machine may not be favourable in combat but against unsuspecting tables or chairs it'll still be very impressive, and far from a toy. If you wish to compete, there are rules you must follow electronics-wise, though they don't complicate things too much.

Best of luck!

[PJ-27]

Re: Need a bit of help - EPQ project

We built Bitza Mk1 for £100 and competed at the 2011 Uk Champs, even got through to the playoffs and came out alive!!
So it is possible to do, but it took a lot of scrounging, boot sales, scrap yards, second hand purchases and eBay.

We have continued the mantra and make our robots from bits-of-this-and-bits-of-that, recycled materials and components etc...
Its a good cheap way to make robots that also prove robust.

Here are our build diaries:
viewtopic.php?f=240&t=4463

The way we think is to consider our challenge and then think what pre-existing component could do this, and then find it on the cheap!

For instance our weapon is powered by a car fan motor (£1 from a scrap yard) and power is delivered via chains and sprockets from an old bike (free) which spins 2 groove cutters picked up at a car boot (50p each).

Some costs you can't avoid though, like ESCs, batteries etc...

Cordless drills are a good example, You can buy them for as little as £12 and you get a motor, gearbox, batteries, drive shaft (with thread and reverse screw end) charger and some speed control via the MOSFETs in the trigger. But some components simply won't last, the trigger and batteries for instance, and you end up with more costs in the long run.

Hope that helps.

[Leonardomayo]

Re: Need a bit of help - EPQ project

I'm 17 so my school's opened up an 'EPQ' project to me which essentially is 'do something and get an AS-level from it' but the catch is that we can't do something we already know about - we have to learn about it from scratch (or at least, that's what they told me).

Well, that's not what i've been told. I'm doing it now and I was told I could do anything. With no restrictions.

[Flag Captured]

Re: Need a bit of help - EPQ project

Thanks for the response everyone! Apologies about not replying sooner, apparently internet upgrades means that you get no internet for a bit. Figures D:

@plargen - thanks, I've had a look at that guide and it's extremely useful, and thanks for the Battery links!

@Anttazz - Keeping it simple was the idea, but I'm willing to pay as much as I need (within reason for a Sixth-former :P) to make it at least somewhat competitive. I do have my own radio gear too buy it's 27mhz, relatively old stuff and I don't think that's legal by the rules so I'm going to have to upgrade that. Thanks for the help with the wiring though, I'll be sure to send you a copy of the wiring diagram once I've done it, if you're alright with that - thanks!

@Relentless - Thanks for the link to that site - I do intend to go with ESCs because they're a bit more what I'm used to than servos, and I have no idea really how to put failsafes in... I do intend to fight also, so I don't think I'll get away with a plywood chassis in the arena :P I am going to build a bit of a prototype first though, and battle some evil looking chairs or something, so I might use that until I can afford to build a proper one, thanks :P

@PJ-27 - That's encouraging stuff! Might have a good look round see if I can get some parts on the cheap like that, thanks!

And @Leonardomayo - Really? Our school's notorious for giving us slightly incorrect information like that, so it wouldn't surprise me if you actually can do anything... good luck with your EPQ project also!

Thanks for the help, I'm just about to start the build so I'll update this with a few images once I've got the basic things built like the chassis and/or electronics...