My impression from this thread is that you are vastly under estimating the forces involved which is not unreasonable based on your inexperience
Printable View
My impression from this thread is that you are vastly under estimating the forces involved which is not unreasonable based on your inexperience
Apologies if I'm misunderstanding here (I'm a geologist, not an engineer!) but how good is the non-Newtonian armour idea going to be against subsonic weapons? All your ideas so far seem to be geared towards stopping bullets, but I'd say the vast majority of more conventional materials used in heavyweights would do that too...I could see the logic of using reactive fluid armour against a spinner with a high tip velocity (assuming tip velocity is something that exists and not a measurement I've made up) but surely something like Tibs will just go straight through it with about 6 tonnes on the tip at low speed?
Two reasons joey,
One is that kevlar is great against an impact since the fibres don't break and it acts like a safety-net, containing the impact. But anything that might force its way between the fibres, such as a highly pointed object can get through.
Sheer-thickening fluid made with silica, solves this. I suspect tiberious wouldn't get through.. BUT, you don't need penetration to do damage: The armour underneath could still be cracked or bent by tiberious and damage done to the internals or overall structure. I am not sure whether I'd prefer to be punctured in one spot, actually!
More conventional materials yes, but I'm looking for weight save at all opportunities.
The second reason for using it, would be that I'm thinking in terms of having the armour plates (each of which is small, and many of them layered-up) attached to the spaceframe with some slower-acting non-newtonian foam bushes and springs. Shock absorption, basically. I am not totally convinced on that one, yet...
With regard to weaponry, I plan to try the crossbow style actuator first because it has the likelihood of storing a huge amount of force for little weight using carbon fibre.
I have a more reliable plan as backup, but which is far heavier. I feel that it is too easy to overestimate how much weight benefit I gain for walking, since the walker is complex and therefore heavy anyhow, and it has to drag that extra weight around making it even less efficient yet again.
It may be that what I end-up with is dictated by cost as much as anything of course. That's the most likely picture.
The real way to do this, would be to have ceramic plates, loads overlaid. But seriously, would you want to find the broken ones and replace them after every battle? No tah!
When dealing with armor and Hydraulic weapons some times it pays to think outside of the box. With Saint I looked at the maximum height the beak Of Tiberius could be raised, and then made the robot that bit taller, Problem solved.:proud:
also it can only chew at the edges of most robots. because the tip pressure reduces with distance from the fulcrum. the beak arm has a short reach.
Axes are harder the way I reduced the damage from them, was conveyor belt wrapped round the body of Saint, this has worked for years.
The lesson
Know your opponent. design round their weapons.
BLIMEY i've just had an idea!Quote:
Originally Posted by Bacon Wizard
*sends tea flying while scrambing for calculator, pen an paper*
"mumblemumble 995psi, mumble..... Bladders... Made to fail... Mumble...composite layers...."
hehehe oh gawd he's off again!!
It's easy to push a robot forwards or backwards, but very difficult to push one sideways. So, mount yer crossbow sideways. :)
Whilst the fancy armour is lovely, it's a real pain in the arse when it gets damaged. Typhoon 2 had an aluminium honeycomb base. Granted this was mainly structural but still the lesson works none the less. Stunning stuff that you would think would have many uses in robots but when it got damaged in the states it recently took 3 days to manufacture and fit a replacement piece. The nice thing about steel or titanium is that with a big enough hammer you can mend on the fly at a competition.
Couldn't you have used a really, really, really big hole saw?
I can't forget the resurrection of Bigger Brother after the fight with Hypnodisk.Quote:
Originally Posted by typhoon_driver
http://www.youtube.com/watch?v=QbKPPp4wBQ0
Afther this beating, Bigger Brother just needed a cheap arc welder, hammers and angle grinders.
Try that with High Tech armor.
And yes, I was there.
True enough lol (great stuff!!)
i'm hoping the layered-scales nature of the armour will asist and mean i get to replace individual scales. HOPING...
Weaponry still remains very open right now, but bringing together some of the othe ideas and with ever more research into them I have some better sketches now and can begin cardboarding.
it looks an aweful lot like a multi-legged tortoise with the segmented plates and gomboc-shaped body. Potentially prophetic :(
Rename: Turtle War?
Just working on the "plug-ends" for air-muscles. The muscles are contained in kevlar so are pretty solid, but the ends can pop-off on home-made versions.
I don't want to risk a poorly made or worn one going regularly, nor do I want to dedicate my time to the fiddly manufacture of each and every one, potentially needing fixed after every fight. So thinking of having them made according to the following ideas. Ignore the figures: they're an accurate representation but not necessarily what I'll actually be running.
Attachment 3661Attachment 3662
Any comments? Glaring errors spotted?
I can see this type of pneumatic actuator shows promise. if the end assembly could be made at reasonable cost this would be an interesting project to follow up Are there any Roboteer machinists that can quote for these parts?
They can exert around 35 x the force of the same size cylinder (at rest) and weigh a fraction of the amount. The downside is they only move 25% of their overall length as a rule of thumb.Quote:
Originally Posted by craig_colliass
Hence why they are the basis of mi proposed walking system, and potentially of a weapon too.
Am about to order a roll of kevlar braid from Australia :)
Had a chat with the carbon fibre layup company finally.
The low-down is this. We can lay up as much carbon fibre as needed to make a very high-power spring and expect a draw-weight of a couple of thousand pounds. But I can't afford it, and it'll all go wrong (break) if it gets a dry-fire at the wrong time, or smacked at just the wrong moment.
The weight is not an issue, although higher than I had thought because of the re-enforcements I would need to make to the arm-ends and cams, and to prevent anything from possibly flying-off and hurting folks. And then I have to have an actuator to re-set the spring.
Despite all this, it would still be both light and powerful. But not, I suspect, quick to reset. And the layup folks give me some rough dimensions and it'll take up a LOT of room in the bot.
All for the princely sum of circa £1000 !!!
In short, I think we're looking at plan B. It will not surprise you I'm sure, that plan B is based on the spiked-club of a mantis-shrimp lol
Managed to acquire 13 festo pneumatic solenoids, some of them fast-acting and a couple of which are actually vacuums. Happy days. All 24v.
What is the general opinion on the following? This weapon could be best described as an upside down axe, or spiked-club.
Theory is that the bot will have a spinning gyro/flywheel inside, and that by engaging a clutch I can use some of that energy to actuate the following loose design. Firstly, is this simply a loophole in "no heavy weight spinners" which it would nevertheless get disqualified-for? In which case, the obvious alternatives are my next port of call.
And secondly, how about the concept in general? The idea of the spike is to potentially get under the other bot, or if not then give some penetration.
Attachment 3686
It's designed to be a kick in the nuts. lol
OK.. wow this is a learning curve! But that's good :)
Have been playing with circuits.. still not used to the maths, but it's all simple really just a bit of a shock after years of not doing any...
It turns out that bumping-up the voltage from 24v to anything between 24 and 72v is really rather easy. People have been talking about discharging huge capacitors which I guess is good for weaponry,. but for overvolting motors off the max allowed battery cells in series something far less "OH F**K"-ish is required.
I bought a 555 noise circuit from maplin, which ends in a Transistor.. that all creates a square wave in your main supply (ie, oscillating) which because it's oscillating can be transformed up by the usual means,. Or a lighter version simply charges a series of 24v capacitors (smallish ones) in turn and then discharges them in series. An inductor is required to drive the circuit and to pull current from the batteries, but it's not as big as a toroid transformer if you don't want the weight. A bridge rectifier, and various capacitor/inductor combos can be used for a smooth result.
Job Done.
I am playing with using the same toroid core for both inductors, because some of the feedback and amplification effects are really interesting albeit over my head at the moment.
This may be very naive of be, but I'm gonna look at using motors as the inductor or even transformer in circuits too.. that way, there's little added weight.
This is a stupid question but what do you need an inductor for?
Nothing stupid about it.Quote:
Originally Posted by daveimi
Couple of reasons why you might want one. One is to smooth the current. They don't like to change quickly and so are to current as capacitors are to voltage in that respect. Think flywheel, only electrical.
The other way, is to drive the rest of the circuit during the off-duty cycle of your oscillating dc source, if you need to: again, flywheel. Buck booster circuits use this, as per picture:
Attachment 3726
Another but complex (to my new eyes) thing is by winding it with 2 solenoids and supplying these from different directions, you can set-up feedback loops which cause their own oscillation as the field reaches saturation, and then collapses. You need oscillating DC if AC is not available, and in this way an inductor can perform several functions at once, including a transformative one that is considerably greater than a traditional toroidal transformer of the same size.
And finally, my understanding is that in the correct setup, an inductor with a decent ferrite core, due to it's inherent stability (current) can actually pull greater current from your battery than would otherwise be the case. This of course discharges it faster and I can see that you need to take care not to damage the battery. Believe me, I'm still working much of this stuff out.
Considering it's basically a loopy wire, I think they're quite amazing bits of kit.
So how come you need this in the design?
Need? This is Robot WAR. It's not about doing the minimum required, it's about making your opponent cry like a girl in the arena, then going for a pint afterwards. Nobody NEEDS better weapons, faster speed, more grip.. but it's all a bloody good idea if you can get it, no?
I have one, single, serious motor. It's an Etek and is driving my pneumatics and the weapon. ie, everything.
It can run on anything between 12v and 96v providing it's cooled and that the time is kept shorter with high voltages. 10Hp @ 48v
I could stick with what it will do without such measures.. but why the hell would I limit my bot to that? I want to smash the crap out of my opponent up to the point where I've won the bout, not politely tickle it and then wait in line for my turn. I want to shove them wholesale into the wall so that they're left dizzy and nauseas, not just amble to my death. I want the weapon to knock them into next century.
I want to be faster, stronger, more mental.. if I have a chance to squeeze a bit more out of my motor when I need it, I'm taking it. My design is already dodgy enough, being a walker. I'm not going to muck-about with anything else. I'm taking every advantage I can.
Frankly, I am a newbie at this, but working out a circuit that can instantly turn 24v into 72v (minus losses) wasn't hard, and I don't understand why everyone doesn't have that option. The weight of the circuit isn't significant for a heavy.
My 3 x 24v battery packs will be in parallel, and most of the time I'll want to keep it to 24v, and last the distance.
But when I absolutely need to treble my output, it's there for me, instantly.
Will you not be exceeding the 50v AC maximum rule wity your design? I don't fully understand it but it sounds like you are turning it to AC, bringing it up to 72v then converting it back to DC. 72V AC obviously excess 50v AC
It just seems a bit "over-engineered" ie...why do you need an inductor simply to bring in more voltage (which you could do with a simple remote switch)? As engineering apprentices at 16 we were given the train of thought that in most cases simplicity will equate into reliability.
Max, DC boosting is well-known, normal, ordinary and old (WW2)
All you have to do is turn the supply on to charge caps, and turn it off again to discharge them. You don't even have to turn the DC off, just re-route it.
Intermittent or unregulated DC is way different than AC.
Quote:
Originally Posted by daveimi
That might be right. I'd just like to smooth the supply out after the result, and I don't want to treble the voltage at a third of the duty-cycle or third of the amperage, either. It seems to me that an inductor is useful.
If you want to run 24V with bursts of 72V, surely it's as simple as using a remote switch to bring the other two packs in series with the circuit?
I understand you want bigger and badder, it's the DC - AC conversions and Inductor packs I don't see the point of. It's quite probably in my ignorance, but is there a benefit to using inductance and ac-dc conversion to achieve the step up in voltage?
Ok that's fine, I thought you were converting it to AC and didn't want you to be caught out by the rules. Although I imagine this concerns the "loopholes" part of the rules so you should ask if it is acceptable before building and I would also ask the event organisers if they are happy to have a 200kg robot in their arena- there aren't any superheavyweights for a reason.Quote:
Originally Posted by Bacon Wizard
It's a walker. double weight allowance. I think it's pretty much established that a 200K walker is ok, if it's within the regs.Quote:
Originally Posted by Max
It's not the weight of the robot that's a problem per-se I don't think, it's the power of weaponry and mass of flying bits against the arena wall. But yeah, EO always get the final say of course.
I bet the whole voltages thing is about fire safety more than anything, but I'm in the habit of asking these things, yeah.
Not using AC conversion.Quote:
Originally Posted by daveimi
But in answer to your question, the regs limit the number of battery cells that can be wired in-series. You can't get anything like 72v by doing that.
Oh ok that's cool.
I wasn't trying to come across as an idiot and appear to be putting down your design, it was just trying to understand the reasoning for the inductors and so on :)
DC-DC inductor boosting is fine just needs some careful thought. The tricky part is getting the circuit to handle the current needed. You can't get around the basic physics that a weapon using x amps at y voltage is after the inductor is going to demand 1/3Y and 3X before it. Also DC-DC boosting is prone to failing or overheating in high power setups. Just suggesting that you make sure that this setup will definitely be able to provide the power needed.
Sources: DC boosting is very common in coilgun making, spent my last few weeks researching it.
EDIT: The voltage limits are to do with regulations concerning what is low/high power equipment. I believe the 72V is the threshold. If there were robots using over 72V it would affect the event insurance or precautions needed to be taken I presume.
You can pretty much boost up to a few kV still with minimal fire risk.
Forewarned is forearmed, cheers.