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Yes you are correct with those figures, but the new one goes up to 10:1 and 6S to keep the speed up.
I should point out, Hardwired II has a lower ratio (less torque) and also about 4kg shy of Satanix (I was tipping the scales on Thursday), an mine also has the vast majority of that weight on/on top of the wheels (my lid is 1.5kg, I have a bar of 10mm steel attached to the motor gearbox plates, my front wedges are hollow).
Yeah, HWII's battery is a bit OTT but I had no idea at the time! And it fits in with the rest of the machine and it's 6.5mm hardox haha
I'm tempted to go with magnets, but they're still debatable in terms of their effectiveness overall... And I'm going for a hardox baseplate next time so I'd have to get creative with mounting them...
Yeah, that's all about right Dave - I need plenty of weight redistribution! And some scales, I genuinely thought HardWired was pushing 13kg... Turns out I was a bit off! Harry's spare bar made a decent counterweight, and did improve handling and grip so it's definitely a priority to adjust weight distribution now...
10:1 on 6s though should be formidable, nothing's going to stop that!
More weight would definitely be a start but you obviously have to watch your weight distribution as Hatchet proved this year, the wheels were up front and the scooter motor, batteries, esc's and axe head were all at the back of what was really a very squat chassis, even the 2kg scoop from Hardwired wasn't enough to tip the machines weight forward. In short trying to make Hatchet as compact as possible hindered it's overall freedom of movement which is why i'm going for something more like thor which is longer towards to back for better weight distribution, with Hardwired though you shouldn't have too much of a problem because of the size of it but obviously trying to add 3 - 4 kg of weight to something so small is difficult.
Yeah, that'll be ideal - I think you could do with a little more ground clearance too, though you've got the axe in case you get beached...
You could always try 4WD too, if you have any spare weight, that'd mean you've got all your weight underneath wheels. With a lipo and TZ85s, you'd easily be able to manage that!
That's definitely a problem with having it so small, but it's definitely doable. If worst comes to worst, I could always stick a thicker back plate on it too, or a mace like thing to make it a sort of thwackbot. It'd be quite effective but I'm not entirely sure what it'd do for handling!
Hatchet 2 will definitely have better clearance, i think at the champs it was the first scoop causing a clearance issue as well as the tires having very little tread and just running on the screws as Hatchet ran fine for a while once i'd taken the scoop off. Hatchet 2 will actually have smaller wheels, around 80mm but a thinner baseplate ( 4mm - 5mm aluminium) but the shape won't allow 4 wheel drive as it will get narrower towards the back.
I would love to see HW2 as a thwackbot, they seem quite big in Australia, just a solid fast box with some from of hammer on the back that they spin. i imagine it would affect your control somewhat as the hammer would act as a pendulum but as the robot will spend the majority of time spinning i doubt that would necessarily be a bad thing.
That's true... Definitely keep posting updates with the design though on your page as you do it - the input from other people always helps! I'll be doing that with HardWired III, just having someone else look at it can mean it'll end up with one less problem or something! At least we've got plenty of time till next year's champs though, that's always a good thing!
I'm extremely tempted with the thwackbot thing too, I think it'd be well suited to it if I can get the grip problem sorted. All I'd need really is something like your axe, welded onto the back of my machine, or I'll have another backplate made specifically for it... I initially thought they were a bit more for show than anything but I distinctly remember seeing one that was very damaging and it's an idea that's always been in my head since... If I can get the centre of gravity balanced right too, it'll handle like a dream in theory. I'm tempted to put some spikes on the front too, to act as both catchers and damaging points as well as on the sides so I can cause damage by driving past. Going to stick to getting it running first though, and the weaponry'll come later, but it's something I'd quite like to run! Chances are that I'll run something like a 1.5kg attachment on the back, or a 1.5kg backplate so I can switch them round if needs be... I'd like to leave the weapon on the back but it'd be insanely open a target for some spinners. Though if I could design something well...
The spinning wasn't intentional either a few times! There were a few cases where I started spinning, and intended to go directly to forwards, but it carried on spinning, or there was a delay in response time with the ESCs for some reason - the main one being in the Gianto/Joule fight... that's when I spotted the problems, seems like there was some kind of function kicking in on the ESCs that meant I couldn't go straight from reverse to full forward. It was very intermittent, but I think a rebind sorted it...
I doubt I'll post much in the wway of designs as atm I don't have a computer good enough for any cad but there will be plenty of updates once the build gets going. I'm actually considering changing the design of Hatchet 1's chassis, as much as I like how it looks it isn't a very efficient shape.
It sounds like a trim issue to me, might be worth experimenting if it happens again
Just do some drawings and/or cardboard aided design haha
If there's one suggestion I'd give, it'd be more angles - I think 30 degrees is the optimum angle, but the ones on HardWired have worked wonders on top of the 6.5-ish mm Hardox. Perfect if you're worried about spinners again! That, and see if you can move that scooter motor down into the bowels of the machine a little more if it'll go, purely because it looks a bit vulnerable there. That, or protect it with some thicker material so that verticals can't get to it again!
Yeah, I'll give it a go eventually if it happens again, not sure what caused it - could be interference but on 2.4ghz I'm not sure that's likely... weird in any case. A lot of the spinning was me just giving up and trying to go all Melty Brain - towards the end of the event I just used to skid so it ended up being the most effective thing to do instead of trying to be all precise!
Unlikely to be interference, maybe just a signal or trim issue or like you said something in your esc settings.
Not much I can do with the current Hatchet really, the shape can change a bit but component placement will have to remain the same due to size constraints. I was tempted to start the new one as soon as but I think Hatchet has a good few events left in it with a few updates. I'll get some designs/specs on the new one in the next few months , should be a huge improvement as I've learned from my mistakes.
Yeah, maybe - I'm switching to brushless soon anyway on HWII so it'll not be too much of a problem. It's not happened again though so that's a good sign! HWI's getting the old brushed ESCs, maybe motors and then HWIII will use whichever drive system proves itself to be most suitable... I'd like brushless but it depends how it works - if it ends up not being suited to that shape/design/weapon then I'll stick with standard brushed. Brushless would be better though.
That's the best thing too, we both had no idea what we were doing going into this (granted, I had a lot of help from Mario which I really appreciate and has definitely been the reason I lasted more than 15 seconds in the arena) but now we've been part of a competition we know exactly what parts of our machines work and don't and what to change. For me, it's definitely been the most useful part of the ongoing design process!
I'd just leave Hatchet for a while too, give it a few more events and then work out what works and what doesn't - the featherweight shows at heavy events are utter chaos so that'll test your design loads too! I think the general outline of your machine works great, but the internals and chassis need reworking slightly as you've already mentioned... Having LiPos and TZ85s will sort your drive, the drills should still be fine and your axe mech is still fine - refine your body shell and you'll be fine! Just have some angles and try not to leave any 90 degree corners and you'll be sorted. Also, you could try 3mm Hardox for the base, or Ti or something if you wanted to go that route, it'd be pretty rigid!
Hatchet 2 will be very Thor/Joule esque in it's design so angles will be a given i think, i was thinking alu for the base but if i can get a suitably sized hardox offcut for a good price i may go that route providing i can get it in weight. Definitely no 90 degree angles on the next one!.
Not a bad plan at all! Just need to be careful on the grade of aluminium you get, but I'm sure that'd be suitable - Hardox or something that strong would probably be better, depending on the forces at play with your axe and whatnot - I doubt it'd bend with it being a bulkhead construction but better safe!
In other news with HardWired II, it appears to be dead. Namely, one of the ESCs has just stopped working, which is very weird... they're TZ85As but one of the two just isn't powering up which is odd. Going to see if there's a connection break somewhere, there shouldn't be but testing it on its own should solve that. It doesn't smell like it's blown, so it's got to be some kind of break or the ESC has literally just packed in - I doubt it being the latter, given the proven resilience of them but I obviously can't rule that out if it comes to it. The next one will definitely have neater wiring, I know that for sure...
Hmm that is strange, probably just a loose connection though, maybe that impact from 720 caused something to come loose. I doubt very much it's broken/burnt out as i think you would have seen something or smelt something, tbh though if it has gone you can get one from hobbyking unhacked for around £25 and i'm sure somebody will hack it for you if you ask nicely.
Indeed, I thought it was 720, but I had it working after that, before I went home... It'll be fine though, it'll just mean I upgrade to brushless a little quicker! I'm sure it'll be nothing major, there's no reason for it to have blown, I'm fairly sure it'll be something and nothing but if not it'll be alright, I'm only using them for HardWired I I think now, 2 and 3 will both be brushless
I would have had them off you but if you're saving them for hardwired that's okay, in sure you'll get it fixed like you said it's probably nothing major
I might be, a friend wants HardWired I to drive next year (may be looking to upgrade it to an LP flipper instead of a lifter) so keeping it as basic as possible drive-wise is ideal, and brushless... I'm not sure how easy that'll be to drive yet. I know it needs time to speed up, like brushed are instant torque whereas brushless take their time to get up to speed, so it might prove a bit more awkward to drive. I'll be able to manage it regardless since I'll be able to practice with it, but they'll literally have to drive it on the day so yeah...
May sell them on someday though if plans change, will let you know if you haven't got any by then!
The brushless drive may take its time byt that might work in your favour, if you think about it with most brushed systems if you gun the throttle you just get loads of wheel spin, the slow start up of the brushless might actually mean you get a better start.
That's true, it could do but if I solve the grip issue, it'd be more of a hindrance than anything.
Also to note, whilst the tires shredded quite heavily during the champs, it turns out I'd not put the screws in properly after adjusting the tread pre-champs, so they were sticking up above the tire more than they should have done, basically I ran on the screws alone for most of the event... nobody to blame but myself for that one!
I was having a few thoughts on the brushless system, I could use a hybrid system - instead of using just sensorless, I could use that as a 'turbo mode' and have some brushed torpedo 800 motors for my low-end drive. It'd be a squeeze to get in, but it'd mean I have the best of both worlds in a fashion. Could always downside on the brushed motors, I don't need those to be my main drive, all I need is something with enough torque to still push things about but slow enough to give me plenty of control.
It'd kind of be like Firestorm's differential in theory, I guess. No idea if it'd work, but if I could fit the brushless motor/s to a forward/backward switch on a DX3, or maybe even program it in so that it kicks in when I've got the throttle for the main drive at about 50% or something.
The lack of start-up torque would be a killer for turning just on sensorless brushless, perhaps a dual brushed/brushless setup is the way forward? I'll see how it works in practice first before mucking about with a hybrid system though, I've never driven a brushless machine so I can't really comment on how effective it is!
Edit: Actually, that's a thought... how would a removable link for a Firestorm-style differential work? Not that one would fit in HardWired II, but it might work in something else potentially...
Depending on what motors you use, brushless drive should be as fast and responsive as a similar sized brushed motor. You probably want far more powerful motors than the 540 sized ones I use in Mr Mangle. Look around for 1/8 scale motors like this: http://www.hobbyking.com/hobbyking/s...or_1900KV.html
http://www.hobbyking.com/hobbyking/s...g/22409(4).jpg
I haven't used that exact motor but its the size I would expect to get a heap of torque from in a featherweight.
Oops, didn't read your post until I had already submitted mine. Basically, sensorless drive motors are rubbish in robots and particularly at low speed and when reversing - go sensored motors for torque and precision control
Cheers Nick, I'll give them a look!
The only problem I have is that I can't seem to find any that are affordable and a low enough KV rating to work on my current setup, which means I'll have to go two-stage or planetary, which is just more stuff to go wrong but if it works it'll be fine! Especially considering I'm a rambot, sluggish turning could be a bit of an issue... it's possible that this 4.5:1 reduction might solve the low-spin up of the sensorless, especially with a low KV motor, but there's not widespread usage of brushless for drive so there's not many accounts of them. Definitely that startup is potentially a killer though, especially with machines like Beauty 2/8 that can just flip you straight out of the ring. Guess that's what testing is for though!
I've been having a chat with Mario about using the NTM 42-38s (sensorless) on my current gearing, I'll probably give them a go at the Barnsley Robot Wars event this year and see how they get on - I've got another project that's using the same motors so it's no loss if it's not as controllable as I'd like... Definitely liking the sensorless though, still open to changing ideas though to get the most out of the drive.
How did you get on driving Mr Mangle at this year's champs by the way? Was meaning to ask you but completely forgot!
The KV of those sensored motors is a problem if you want to use your existing 4.5:1 reduction. According to a great engineering article I read, that's also not ideal for sensorless drive either. After showing some maths and test results, the author concluded that a higher KV motor with over 20:1 reduction worked better than a low KV motor. That was for powering an electric scooter with outrunners but I think the results will be the same at smaller scales. The other problem with a low reduction and sensorless motors is that low speed manoeuvring is very jerky as the motors go from stationary to a relatively high speed. A large reduction smooths that out a bit but your 4.5:1 won't.
Sorry to pour cold water on your plans, its just a combination of studying other people's issues and local experience - I'd rather you got a good result first time rather than putting up with problems. Can you add another 4.5 reduction stage in the bot? That will give you a very handy 20.25:1 reduction that will work with a wider range of motors.
Almost forgot: Mr Mangle drove quite well - you can probably tell that I am the world's worst bot driver :). The only things I am changing is increasing the braking in the ESCs to 100% and increasing the expo steering rates in the transmitter a bit. That should take out the over-steer.
Change the reduction yeah. Maybes shove a planetary stage before the spur gears or something?
Oh no, you're not pouring cold water on anything! I'd rather have as many opinions and accounts as possible, helps me design something that's more likely to work well! I'll still be getting the NTMs so there'll be nothing lost, but if that's the case I might try and squeeze the two-stage in with some beefy sensorless motors. Depends which method would be the most size-efficient and lightest, but it's definitely a good idea! I'd quite like just a pair of gears similar to the ones I have now over a planetary, but I'll see how I could make a planetary that'll have enough strength to stand up to that kind of force...
Good to hear Mr Mangle worked well too, it seemed to handle pretty nicely I have to say! Did the motors have to come to a full stop, then brake before they'll reverse or was it more or less instant?
Just using an identical 2nd stage sounds ideal - you already know it holds up in use. You might get away with a single stage Banebots P60 as a first stage but motors you want have too much torque for a 2 stage P60.
The brushless set-up I have is instant reverse and plenty of other ESCs have the feature, particularly the sensored ones. Its important to download and read the ESC manual before buying anything; the reversing details are often vague. There is at least one Hobbyking sensorless ESC that has instant reverse, I will try to find a link.
Another option is to add sensors to an outrunner. Its been done before and someone even had a kit for it. It only works for motors with a certain number of poles but that still leaves a wide choice. A sensored outrunner would be a fantastic resource for bot builders; it would offer low speed torque, instant reverse and lower cost.
I found the sensor ad-on kit here: http://e0designs.com/products/hall-effect-sensor-board/
It only works with 14 pole motors and down to 50mm can size but that still leaves plenty of motors to choose from, including the NTM 50mm series. I might just have to try this out myself! If this works out, I predict an invasion of fast & reliable wedge bots
Yeah, that's the problem with the Banebots stuff... at the most, it was designed for 775 motors I think, putting a massive brushless in it can only only end badly!
I shall have a look at the sensored ESCs too, I've found one non-hobbyking ESC that's got instant reverse but it's a little too expensive. Going to trawl through the manuals when I've got chance!
That's fantastic too, thanks! Though I have to say, if I can get that to work with a 2.5kw brushless NTM on 8s... I think that might be the scariest rambot known to man. That's like, 6 horsepower in theory? Crack a massive magnet in there and we're good to go! Perhaps the two-stage would be ideal there as well, though not quite as heavy a reduction...
Would definitely be a good thing for robot combat as a whole too, might make brushless a lot more accessible if it proves similar to high power brushed motors that seem to slowly be dwindling in numbers...
Its hard to find an ESC that runs on 8S and has reverse. This HK one ticks the most boxes for me: http://tinyurl.com/ofe6mc5 its only capable of 6S but that still gets plenty of power out of an NTM 50mm outrunner. I think you need to get some MUCH wider & grippy wheels to make use of all that power :)
Yeah, that's one of the ones I spotted, it seems alright! Perhaps not 8s but that's way OTT anyway (that said, that is the name of the game with HardWired haha!) might get some on order when they're back in stock...
Definitely too! I'm aiming for thicker wheels, but will definitely have better tread on there! I think I wore the current set of wheels out during testing, going to get plenty of spares made up next time! I'll probably use some kind of magnet downforce too if I can't get enough grip from the wheels, I think with that much power it'd almost be a requirement. I'll see how it performs though first and make changes accordingly! I'm definitely having a gyro in next year too, it'll help dramatically with the steering. It seemed to drift off to one side and spin during long run-ups which is a pain to deal with, but nothing that can't be sorted!
I was rather disappointed with gyros when I tried them several years ago - do the UK builders have a recommended model? I can use all the driving help I can get!
Hmm, if I follow the trend in this topic, I should suggest to keep hardwired II for fun, and build a Hardwired II evo for monsterpower. The way Hardwired 2 is build ain't really suited for upgrades here discussed.
Nick: been using one of these in Satanix for years, couldn't drive without it:
http://m.ebay.com/itm/141256473060?nav=SEARCH
Interesting - quite by accident, there is a perfect gyro mounting point between the motors in Mr Mangle. Its cheap enough to try and not worry if it doesn't work out.
Mario, that sounds like the best plan - was thinking about it today/last night, it'd mean quite a major overhaul to get everything where I wanted it to go, maybe it'd have all fit (just), but a rebuild might mean I could get more weight over those wheels, and have plenty of space for everything else in-between... Will definitely get to designing that on paper! I have had a few ideas based around how Satanix works with the majority of weight being directly on top of those wheels, that'd be ideal for putting that power down. May keep HardWired II but as a thwackbot instead because that might be a heck of a lot of fun - would just need some additional parts put on the back, and it'd be fine I think, but I'll not mess too much with it. Definitely taking it to all the spinner events I can though because it literally does not care about any hits from them!
Also, cheers for that gyro post Dave, I might get one of those too, would be very handy in this new machine, and indeed in HWII, it seems like it works very nicely in Satanix and more control is definitely what I need in a robot like this. How fast does Satanix go too? It seems to go insanely fast at full pelt,got to be a lot of kinetic energy behind that!
22mph in theory. The new set up will take it down to 18mph but the increased grunt means I should still be hitting them as hard (hard to generate full speed with another 13kg on top).
I think personally you should make the new one four wheel drive you'll have more than enough weight if you keep it small , plus you'll save weight going to brushless and it would be easy to distribute the weight evenly. Not to mention the fact you could push just about anything with ease!.
Something that's been interesting me of late is what's the maximum amount of grip possible by a thirteen kilo robot? I say this as my dad is a racing car builder. In a certain championship he's been building for, the car's are front wheel drive, and among the community for this class there is a general consensus that more than 220bhp or so just becomes wasted wheel spin. To this end they'll build the car, and then set the turbo boost on a rolling road so it JUST touches about 210 - 215bhp at the wheels.
This has made me think...I wonder if there's an amount of torque that past a point becomes wheel spin, and you can keep putting bigger n bigger motors in, but you're still sort of restricted by not being able to put the power down. I have been watching your build like every night after work lol to see what sort of results you got. I'm right right on the cusp of building a big power drive train for my robot. But when I've over-volted the drills and locked the clutches up, it will happily push a 10kg weight lifting plate up and down the driveway. If I double the weight the robot tries its best but just smokes it's tires (which feels way cool I may add!!).
Erm...so to sum up...I know building some sort of s900 torpedo 800 type drive train will definitely benefit my plywood La Machine clone given the type of robot that it is. However...if it will happily shove 10kg about, is it worth me spending what I predict will be about £150 sorting a big drive train out if the £30 drill setup is at the invisible border of grip anyway? Would it be best to move onto four wheel drive? Would it be best to get six wheel drive? These are all of my curios wonderings!!!
My working layman's hypothesis is: NO MATTER WHAT MOTORS AND WHEELS YOU HAVE, YOU STILL ONLY HAVE 13KG OF DOWNFORCE TO WORK WITH.
Don't forget though if you have a scoop you have 13.6kg + some of the weight of the other bot. In addition more torque will help in the event of a wheel becoming clamped to break the clamp or some such. And you still have acceleration to consider (though even drill motors are pretty good for that one). Other things to consider are matching the drive train to the weapons you're running. If I'm running an axe on 6 cell LiPos I'd like a drivetrain that can take 6 cells without large overvoltage.
EDIT: Interestingly I did experiment with this in the antweight class with a 4WD pusher using small pololu wheels. Moving from 1 wheel per motor (4 in total) to 2 (8 in total) was a massive improvement. But I tried 3 per motor (12 in all) and performance suffered, for that I found 2 wheels per motor was optimal.
I have to disagree, softer tires will give more grip than harder ones.