Well, I've decided to have a go at this...

I used to love watching Robot Wars when it was on several years ago, but being 12-13 or so then I wanted to build a robot but really didn't have the technical knowledge or any idea where to start, really... now, however, in the middle of an engineering degree and almost a decade later, I've found that people are still doing it...

...so I think it's time to actually have a go myself! I'm pretty confident in what I know and have access to CAD, analysis packages, CNC machinery, rapid prototyping, etcetera... so I'm hopefully going to be slightly more ambitious than building a straightforward wedge or pushing machine, especially when what I really enjoy is the whole visual aspect... it's always the machines which are really exciting to watch that I'd be interested in, rather than just something which wins a lot of fights but is, to be honest, a bit dull I find.

I understand that the best way to go is to use cordless drill motors (with an integral gearbox) for power, as they're cheap and reliable, and easy to drive with standard speed controllers and radio gear - so that's what I'll do for a drivetrain. However...armament is the big thing I've been thinking about and are perhaps looking for advice with. Much as making things fly looks cool, I think full pressure pneumatics are out, as although I've worked with compressor-powered equipment, 700+ PSI of full bottle pressure combined with the issues of handling liquid CO2 in the system, rapid cooling and icing / loss of seal properties due to extreme cold, and all the other issues are things I don't have experience with and I wouldn't want to try and get working without advice from someone who's done it all before... so I think it's down to a spinning weapon (possibly a bar, due to the high tip speed and good energy transfer properties... though as I understand it I wouldn't be able to use the robot terribly often due to safety concerns and a lack of arena protection), an axe (though I haven't seen very many effective ones) or a hydraulic or electric (linear actuator) crushing device like that on Razer. I know all of these have been done on featherweights, so anyone with good (or any!) advice would be welcomed...

first off welcome to the robot world you have amade a good decision :talker:

i have been doing the sport for 3.5yrs or so and have built 3 fws so far Psycho Fling Block Of Wood (very famous :P ) and my newest bot crumple zone a crusher robot with 700kg of crush on the tip

i am currently thinking of changing the lifter weapon on psycho fling to an axe bot

i would suggest buying a spektrum radio set early on and build from that

personally a spinner as your first bot may not be the best pln but axe bots are rare bit can be real fun

hope this helps

Alex

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Originally Posted by psycho_fling

first off welcome to the robot world you have amade a good decision :talker:

i have been doing the sport for 3.5yrs or so and have built 3 fws so far Psycho Fling Block Of Wood (very famous :P ) and my newest bot crumple zone a crusher robot with 700kg of crush on the tip

i am currently thinking of changing the lifter weapon on psycho fling to an axe bot

i would suggest buying a spektrum radio set early on and build from that

personally a spinner as your first bot may not be the best pln but axe bots are rare bit can be real fun

hope this helps

Alex

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Yeah, I've been looking at the spektrum dx5e or dx6i for radio as it seems the best bet for reliability, programming options and not having to deal with crystals, as well as being more tolerant of interference... all plus points for me :)

What are you using to power Crumple Zone, linear actuator? If I did a crusher I'd probably lean in the hydraulics direction myself (has anyone else done it at featherweight?), I know of a few places that do sealed electro-hydraulic actuators in a weight range that could probably be fit in...

Hi Nick and welcome to the fra forum.

Read the Build rules first and there are plenty of roboteers willing to help.
http://www.fightingrobots.co.uk/rules.php

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an axe (though I haven't seen very many effective ones)

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Have you seen LittleHitter or Basher? two good axe bots.
ROB....

i use a linak linear actuator army spec

yeh i think there is a hydraulic fw crusher in the Netherlands??? But none in the UK i know of - Tiberius is a great robot hw that uses hydraulics

btw the spektrums never get interference thats basicly why everyone has one lol

alex

Hi Nick welcome to the forum. I would go for the dx5e unless you are sure you will need the six channels they have been much more reliable in binding to the reciever. There is one other currently unfinished feather that uses hydraulics that I know of, predator (a mini warhead) but I know roughly how much the hydraulics would cost for such a system, not worth considering. My advice would be since you seen to have all the facilities CAD, CNC etc then go for an axe, possibly
pneumatic, probably a rack and pinion type like Terrorhurtz, cos there are too many flippers and we need some axes.

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btw the spektrums never get interference thats basicly why everyone has one lol

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And now that everyone is on Spektrums, all the oldies who still use 40MHz (like me :)) almost never suffer frequency clashes and I've never had a major problem with interference.

Welcome to the forum Nick. Sounds like you've got a good grounding, knowledge and resources (CAD, CNC etc) to hand which is a pretty good start even before you've designed or built your bot. Where are you studying your degree, and what year are you in? (just slightly off topic, as I'm studying for a Mech Eng degree)

Although plunging straight in to building a robot with a weapon for your first attempt quite doesn't work out for some people, it sounds like you're competent enough to take a sensible moderate approach to it, rather than jump in and try to make your weapon super-awesome-better-than-everyone-elses. After watching Robot Wars as a kid too, I finally got into the sport (about five years ago) with a basic wedge and while it is an easy starting point for beginners, they do get a bit dull to operate after a while!

As for your weapon choice, where are you based? Because that could have a bit of an effect. I would definetly recommend a spinner as they're so much fun, but as you are aware, they can only operate at a few events a year. If you're based in what seems to be the nucleus of roboteering (mid-England, Birmingham and surroundings areas), you may be better off leaning towards an axe or crusher as you'd be able to run these at both Roaming Robots and Robots Live events (plenty of them running each year) as well as the full combat events thereby getting regular use out of your machine. You could even go that step further and build modular weapons units, so that you could run an axe or crusher at most events, and then whack a spinner mechanism in there when the full combat events come around.

As for advice on the wepaons themselves;

Spinners: while you must take care working and operating them, I wouldn't say they're actually that difficult to make. Basic parts are a motor to power it, a means of transferring the motion from the motor (timing belts and pulleys, gears, chains or friction), the spinning mass itself, a shaft for it to rotate around, bearings to improve efficieny, and a frame to hold it all together. While there are other little bits and pieces to help fine tune it (tensioners etc) they can vary from bot to bot and is something you're bound to come across and form a solution to it in your own bot. For frames, aluminum and steel are the most obvious ones and they can usually withstand the loads from spinner impacts, but plastics work very well too. I use 20mm thick Nylon 6 on my robot and will be changing down to 12mm polypro for the rebuild. Rather than bending from impacts and stresses, they elastically deform to dissipate the energy and then resume their original (or pretty close to original) shape. They're also cheap and very easy to work with.

Axes: the two most successful axes without a doubt are Little Hitter 2 and Basher. However they both utilise CO2 and since you're keen to stay clear of that until you've gained a bit of experience and advice, the next best method of power is electric. Simply a motor connected by a chain and sprocket setup (the most popular choice) to the axe and you have yourself a weapon. Its similar to a spinner in the sense that you need an axle/shaft for it to run on, but you'd need a larger gear reduction to decrease speed and increase torque (compared to a spinner). I've not made a proper axe weapon myself so I don't really have much to add to the above info but there are plenty of others who will be able to expand on the subject. This Australian Robowars Wiki article may help too: http://www.robowars.org/wikka/ElectricAxeWeapons

Crushers: hydraulics have not yet featured in a fully working featherweight but as Alex has mentioned, there is a European featherweight that is due to have working hydraulics and I believe a UK roboteer is working on creating a micro-hydraulic system from scratch. Until then, the most popular powerplant for a crusher is an electric actuator. Alex has a gem of an actuator in his robot that gives 700kg of tip crush; I have an actuator that will give 400kg of crush. Anything less than this any you'd be struggling to pierce an opponent's non-metal armour (metal armour these days is superbly strong and thick and most likely won't get pierced by a feather crusher, only bent at most).

If you can find an actuator that gives somewhere between 600kg and 1000kg then you've got a good force for a crusher. Downsides are that most actuators of that rating are quite large and may have to be partially exposed in order to save weight (http://www.teamdragon.org.uk/html/dragonsclaw.html). The other thing with crushers is to make sure they don't destroy themselves! Strong bulkheads running the length of the robot to add rigidity and strength and hopefully stop the baseplate from bending, strong shafts or axles at the pivot points, and a strong claw construction will all be essential - lots of strong basically :lol:

If you use MSN, feel free to add me lenny_1024(AT)hotmail.com. Many other roboteers use MSN too and its a useful way to bug other roboteers for useful advice :)

Finally, best of luck for when it comes to building your robot 8)

Daaaaamn, that was one long post :shock:
I really ought to get back to studying

Remember that with an acutor you can double the voltage of the actuator then the crush value goes up by 4 times :idea:

Cool, thanks... I'll be picking up one of those then! I've found a couple of Makita 12v drills with missing batteries knocking about that I'll rip apart, lock up the transmissions and use for drive motors... get some motor mounts CNC'd including a HDPE surround for the gearbox to give it a bit more structural strength if (when) it gets smacked by something.

Any suggestions on speed controllers? I foresee many blown up mosfets if I end up working out my own, so I imagine I'll be buying them - I've heard the best are from robo-challenge with regards to not blowing up, but their store seems to be down at the moment?

Awesome posts guys, this seems to be going well so far... as for the CO2 thing, I'm happy working with regulated CO2, but full bottle pressure has me a bit concerned at the moment... at least until one of you guys fills me in on how to do it right.

As for weaponry, the problem I've foreseen with a big axe is that such a light machine would just go flying off the ground from the recoil of a powerful pneumatic axe, which is what's put me off the idea a bit... that, and the fact that everyone and their mother seems to be amoured up with Ti, 10mm HDPE, Hardox etcetera. from what I've read on here, and the kind of power needed in an axe to put a dent in that would definitely send me bouncing all over the place... ahh, what the hell, it'll be fun trying :D

If anyone knows how the hell Terrorhurtz seals their ram, I'd like to know... from what I know of their mechanism the rack teeth cnc'd into the ram would chew up the seals horribly. I suppose on the return stroke you don't need too much efficiency or force though, so an imperfect seal wouldn't be all that much of a disaster...

Once again, thanks guys! :D

[Edit] I'm pretty much leaning towards a rack and pinion axe, or Final Destiny-esque skirted bar spinner for the design... now to go ahead and work on details.

Welcome to this strange world Nick, I'm building/planning/designing something over the summer as well so should be interesting to see what I can learn from seeing the efforts of someone with better engineering facilities than me :proud:

Axe recoil can be solved easily by having a counterweight on the other end of the shaft...it adds weight (obviously :P) but Iron Awe 2 used that very successfully and had a very powerful axe as a result, running off full bottle pressure CO2 with no real recoil (although they tended to spend more time flipping people than axing them, heh)

I remember reading Thz had a custom made rod and the stock seals in the ram do the job nicely, might be worth looking at their site and see if there's anything on there.

If you want to talk spinners add me on msn - xzibit206@hotmail.com

I've been playing around with spinning bits of metal since I was 14 and know a lot of the ins and outs of effective spinners.

Easy to build, difficult to master:wink:

Yep, just found the details on Terrorhurtz's ram seals... I would have thought that rack piston would have been absolute death to pneumatic seals but there you go, it works! Nice, lightweight, simple mechanism... though I'd put a guide roller underneath the rod on the other end of the mechanism to give things a little more support, as it wouldn't weigh much more.

I think it's going to be an axe... hell, maybe I'll build two of the damn things someday, or go for a modular setup... I can see a spinner being great fun, but barely being able to use it seems to be the problem.

What I envisage is CO2 bottle --> bottle valve --> Regulator --> master arm solenoid valve --> buffer tank with safety burst disk and system depressurisation valve (open to the air) --> high flow firing solenoid valve --> Single action ram with spring return (to save gas giving me more axe hits, and if the return isn't gas-actuated then I wouldn't need to worry so much about the cylinder end seals being compromised by the rack toothed rod) --> another solenoid coming off the bottom of the ram, to vent it once fired and allow the spring to return it. Safety-wise, that would allow a startup as follows:

Radio removable link in --> system dead
Motors/weapon removable link in --> system dead, verify solenoid valves closed (they would have indicator LEDs across them).
CO2 bottle ON, Regulator ON --> System live up to arming solenoid
Close depressurisation valve --> System post-arming solenoid now gas tight and ready to receive pressure.
Remotely via radio:
Master arm ON --> System fully live, buffer tank fills with CO2. Axe now ready to fire.

To close it down:
Turn off master arm solenoid remotely - no further flow from bottle/regulator.
Open cylinder vent remotely and hold open while firing the axe (axe return button)
Fire the axe remotely, everything in the system downstream of the master arm solenoid will then flow out of the vent solenoid. Empties lines and the buffer tank.
Take the links out.
Close the CO2 regulator and bottle.
Open the system depressurisation valve to ensure system can no longer hold pressure.

Just thinking this through... obviously a pneumatic axe would make a mess of anyone foolish enough to be in the way when it went off, so this seems to be the most sensible way I can think of to do it while minimising the risks of it taking my head off while working on the robot... If anyone sees anything really stupid I've overlooked, please do point it out!

I just added both of you on MSN, by the way.

Well, I've decided to go for a very low profile machine with a horizontal overhead spinning bar... the thought of clashing metal and showers of sparks just got too tempting. A big rack and pinion pneumatic axe therefore remains a potential future project, perhaps for a second robot...but that's a long way off.

The design is a low UHMWPE box (at least the chassis) robot with the overhead bar spinner, and spring loaded anti-wedge skirts all round... influenced by Hazard and Final Destiny from Battlebots. Ideally the skirts and top will be Ti, but we'll have to see about that... power will come from two 12v drill motors to move the thing around, driven on two front wheels and with the back end supported by a pair of captive ball bearings in place of the wheels...keeping the box level and allowing me to chuck the back end about nicely. (I'll consider that further as it comes, if it comes in lighter than the plan I'll go for chain drive and AWD).

I'm planning to go with a Sabertooth ESC, along with the dx5i Spektrum radio and lithium ion cells (A123s) for power. Weapon drive is something I'll decide on when I get the bar... I'll take a look at beefing up the existing gearbox with the bar (ex-2500w angle grinder), and if that doesn't look too practical I might end up biting the bullet and spending the ridiculous outlay on one of the TW 'boxes as they're for all intents and purposes bulletproof, or so I've heard, and pretty much dead reliable even under the battering dealt out by big spinner-to-spinner smashes. For drive, the Magmotor route seems tempting after a chat with Gary due to the sheer amount of grunt the thing has... an expensive beast, though, so we'll consider that when it comes. Plus, talking about Magmotors is getting to sound awfully vapour-bot-ish, so I won't get onto that QUITE yet... the weight for one and its batteries should be left available, though.

I'm planning to go ahead and start piecing the drivetrain together and getting hold of the bar, checking everything works, and then doing the old cardboard layout routine to finalise the dimensions - before transferring it over to CAD and CNCing the chassis and structural components.

Oi, nothing wrong with talking about 'vapour-bot-ish' things :P

UHMWPE should be good, Craig uses it on The Saint's wheels I believe and it's quite stiff at 10-15mm thick (it's what I'm planning on using anyway, so it should be...if it isn't I may have problems)

I take it you're planning on the skirts to prevent you from getting flipped then? Having a big bar whirling around the top and the gyroscopic forces thereof will help keep you down, but with the sheer amount of flippers around at the moment I wouldn't assume that you won't get flipped. It does sound very mean though, hope the design works out...and hope I never come up against it :proud:

Oh, I fully accept the risk of getting flipped and not being able to right myself... that's what you get only being able to run one way up and no self-righter, after all :( The idea of the skirts is two fold: to minimise ground clearance and therefore avoid flipping, and to try and guide any really obscenely low rammers/lifters/whatevers upwards to get smacked by the big spinning bar. If I get lifted up there's a third defence which is the bar knocking into the ground and hopefully throwing me away and back down... but we'll see when it comes to that!

As of now, the preliminary design is approximately 3 and a half inches high, with the bar spinning ~4 inches off the ground - which should send it smacking into most things out there I've heard about.

I haven€™t read the rest of this thread so I€™m not sure if anyone has said this, but can I just advise you, before you start collecting parts and start the build. Come to a show and see what kind of opposition you will have, how things have changed since RW and what we do etc.

I have seen quite a few people build feathers and then go to their first event with them. After the event, they will scrap the whole robot and start again. This is ok but...expensive.

Goodluck!

personally id make the bar spin lower becuase there are many low machines out there

Oh, I'll try to make it up to see what's going on when I can, hopefully sooner rather than later...

As for the height issue, with the bar on top I really can't see how to get it spinning much lower than 4 inches from the ground... maybe 3.5 or just over with both the top and bottom chassis plates in Ti, and that's pushing it. The disc motor and gearbox limits how thin I can make the machine. The idea of the sprung skirts is to force the lower machines up into the blade... I'll see how it goes talking to people. If it's too much of a problem I could always scrap the current plans and go for an undercutter...

like other people on here i talk alot on msn so u can add me if you want

I think you'll be fine having the blade 4 inches off the ground. I've just gone through my pictures from the most recent featherweight championships and while there are a few low robots out there, there are more that are 4 inches or higher, so you should make contact with a lot of them. And even if they are lower than 4 inches, you'll have the skirts to coax your opponents up into the blade :twisted:

If you decide to go for an undercutter, I'd suggest trimming the blade to about 600mm long max (depending on design) as you'd probably be looking at a very large and structurally weak robot otherwise.

Sounds like, with the CNC and all, that it should come together pretty quickly. Think you would have it ready for the tag team championships in September if you throw a drag-racer together too? :)

Pretty sure I will do, once exams are all over and I finalise designs it should come together worryingly quickly.

Nope, not going to be an undercutter :twisted: as I was saying before, that's what the skirts are for...

As for a drag racer, while it would be tempting to get a trashed kart from the kart track my mate works at, hammer it back into shape, and weld a bunch of chainsaws on to power the back axle... I'll probably (if I go) just end up getting a battered old belt sander or circular saw or something, and cable tying some poles on to make it go in a straight line :P