HardWired II

Unfortunately, it turns out I'm not going to be able to make it to any more events bar the champs next April (I'm assuming they're at the same time again-ish), at the minute at least. Kind of a shame, but it means I can put a little more money into making these robots at least kind of decent. And when I say that, I mean send things off to be watercut and welded or whatever so I can then bolt it all together and not mess anything up

Today I made some wheels for the beetle that ended up as heptagons. You know you've messed up when you set out with a circle in mind, and end up with a heptagon.

Anyhow, little bit of progress on the design portion of both Archangel and HardWired 3. Somehow, archangel is seeming actually doable, got a solid hardox inner body like I mentioned before with HDPE pods attached to that. The front and back plates will probably both be hardox still, which gives me more solid foundations to bolt each side to I guess, but either way it means I can make it wider without worrying as much about it weighing more than a cruise liner, even if it is the size of one. Will post some drawings tomorrow or something, but very rough maths says it should be doable with 15-20mm HDPE, which is great news and means it may actually be able to keep the ludicrously overweighted bar. Which also still needs designing.

Beetles have taken a back step though, given they'll have no outings until at least next year. Shame but prioritising is a thing!

Anyone know of any commercially available drill motor mounts? I've wasted half a sheet of HDPE attempting to make some and I need them to get stuff running haha.

Also wheels with nut inserts already in them, need something cheap too because this is super budget territory...

I could knock you some up if you want, and I've got 2 of the 75mm robochallenge blue wheels with nut inserts, pay the postage it's all yours.

You don't need HDPE mounts just some hose clamps. Drill 10mm holes in your base plate and wrap some insulation tape round the gearboxes so it has something to bite into. I've run a few robots like this and never had any trouble. Hose clamps are a couple of quid each from halfords or amazon etc. See picture below. Also makes it extremely easy to remove a blown motor ie. 1 min or less.


http://i174.photobucket.com/albums/w...ps1af63cbf.jpg

I used some in Balsa Steel and wasn't entirely convinced, though I used a different style of hose clamp so maybe it's worth a shot. Do want something more solid for this though, if possible - I'm intending to use them as part of a structure too!

Design question time

Welcome to another installment of 'Matt has absolutely no idea what he's doing but wants to build a silly bar spinner anyway so will spam the forum with questions' or something.

Few things - it dawned on me that spinning the weapon faster would be more beneficial in terms of the stored energy in it than just simply increasing the weight - whilst I don't really want to drop the weight of the thing a lot (2.5-3kg would be the lightest I'd like) is it worth reducing it down from 4kg, and making it faster?

Truth be told I wanted a 4kg bar spinning at about 5000rpm with two massive blocks of tool steel either side of an aluminium/Gr5 ti bar a little like NST/Scissorhands use but I'm thinking that it might not have as much power as something with more speed, if that makes any sense?

Or failing that, go for monstrously high speeds, a lighter bar and a single tooth a little more towards like Electric Boogaloo's? I am more towards the 'build it and see how it works' type of philosophy but the cost to have all this lasercut and for the materials means I'd rather get it (much closer to) right first time!


And as an aside, I've been offered some bits of Stainless plate of varying thickness to make future machines out of - how would say, a 6mm welded stainless chassis hold up compared to the equivalent in Hardox in a design like HW2's? I know that Hardox loses some of its strength after being welded, which is why I ask really. Maybe it won't be as strong overall as Hardox, but in that thickness... is it really needed?

Thanks for any help too, and I really do apologise about the onslaught of questions, I need to learn to engineering better before doing something this ambitious again haha.

Cheers!

Increasing the speed is very effective; the equation for kinetic energy of a spinning disk or bar is:

Kinetic energy = ½ × moment of inertia × angular velocity squared (where moment of inertia is basically the weight and angular velocity is the RPM).

That means a large reduction in weight can be made up by a relatively small increase in the RPM to give you the same amount of energy. The downside of a high RPM vertical bar is that the bot will gyro dance something wicked.

EDIT: since you mentioned Scissorhands, its weapon only weighs around 2Kg and spins at 2,400 RPM. If you doubled the speed on that it would have 4 x the energy. OTOH, the bar is spun by a Mag motor with a peak output of 2.2KW; doubling the speed will need a correspondingly larger motor.

Thanks! Yeah, it seems a lot better to have it spinning faster, truth be told I'd love to have a 4kg bar spinning at 8000rpm... but the likelihood of that either happening or not tearing itself apart is just not too high at all haha. That is something that is quite a bother too, the weapon motor - the NTM 5060s, I've heard, are pretty monstrous when it comes to their power output but it's certainly something I'll have to keep an eye on...

Whilst I'm on the topic of all this, what type of software is good for designing spinny things like this? I think it might be a case of playing about with designs and plugging it all into that equation, see what hits hardest!

You'll see the results of Valkiri's 4 kg disk as it was used last weekend soon enough. But Valkiri's welded ali frame is now officialy "Eschered". No longer useable.

5mm steel buckled upwards, 35mm 3.5mm woodscrews ripped out of the PE

Attachment 4775

Thanks to little old valkiri...

The best free software is actually a very old site: http://www.teamcosmos.com/ke/ke.shtml. You have to use simplified shapes but it can give you a good idea of what your design will do. It works best with IE explorer, I have problems using it with Firefox.

Stepping up from that, you can use CAD software like Solidworks; there may be cheaper & easier software about but I don't know of anything else.

The NTM 50-60 motors have is similar output to the Mag motor in Scissorhands, which is pretty impressive for 1/8th the cost and 1/4 the weight. If you are increasing the bar's weight and tripling the speed VS Scissorhands, you will need a motor like Hobbyking's Rotomax 50cc.

Just remember my motto: 'With great power comes a great big motor to spin it' :lol:

We use that NTM in Valkiri on 4S.
And we're thinking of downgrading, lower rpm on an smaller disk. Even with a wheelbase over 500mm the gyrodance limits any kind of turning to "use a calendar to measure time to turn 180°".

That's why both my vertical spinners are eggbeaters - so much less gyro effect at high RPM :)

On full speed they turn fast enough to be meassured with something more accurate than a cuckoo clock?

Wait for our National championship next weekend to find out. As long as Mr Mangle can turn a bit faster than all the disk spinners, that's a a win for me. There is some complicated maths to prove that gyro forces favour small diameter spinners but I never attempted to work the equations.

Nikc, you know I'm a follower of your building thread. And I'm eagerly awaiting the fights over there.

I can't resist a free plug to get everyone else watching the event:http://www.robowars.org/forum/viewto...1978&start=180, There should be heaps of video and possibly a live stream.

My theory at the minute is to have the bar very torquey so that I can essentially have it on tick-over and then when I end up lining an attack up I can spin it up to full in very little time... of course, it's all just a theory but I can see it being at least somewhat usable I guess. Going through a little bit of a redesign once again though on the drive side of things, may or may not look alarmingly similar to Electric Boogaloo now... That said, I'm borrowing from the best! The utter carnage that caused against Original Sin was frankly incredible.

I'm also looking forward to those fights too Nick! If you happen to need a livestream chat moderator or something whilst it's all going, give me a shout and I'll be on hand to help! Particularly looking forward to seeing how everything pans out though, there seems like there's going to be some really solid matches!

Wish you'd go and build something so we can have some piccies!

http://i1355.photobucket.com/albums/...ps8a1efbf1.jpg

Seriously though, I'm hoping to make a crack at getting HW2 running soon... it's just about money and time, being a student I have little of each! Not to mention a few side projects I need to get doing. Robots have definitely taken a back seat, but it should only be temporary!

It seems counter-intuitive to have what will essentially be 3 machines running for the champs I realise, but if I have HW2 running I have a fallback - if I get the other two running then it's a job well done! HW3 should be simple but expensive, Archangel a lot more complicated but cheaper. Just depends on what I can get sorted really...

Oh, and I found a solution to HW2's drive problems - single stage RS775s. With a certain combination of gears I can get something like 9.5:1 on 80mm wheels, which might tax the motors a little but the thing will move, and that's good enough for me at this rate! Would love a pair of 900s to just drop in, but unfortunately I simply can't afford the asking price for them these days, and then there's the worry of breaking one too... RS775s are much more common I'm led to believe (hence, cheaper) so would potentially be viable to at least get it operational.

I've done some interesting things to the design of HW3 though, which in turn should hopefully negate this sort of problem in the future... hopefully!

Or at least, I've built it with edits/upgrades in mind, not just to directly fit the size of the 900s, which has naturally led to many problems with it being a relatively compact gearbox choice length wise - would stick a pair of drills in there but it plain and simple isn't big enough!

Archangel MK1 (Aka Matt can't CAD part 2)

http://i1355.photobucket.com/albums/...ps5f9d9fdd.jpg

http://i1355.photobucket.com/albums/...psc8ffbe3c.jpg

http://i1355.photobucket.com/albums/...ps28562771.jpg

http://i1355.photobucket.com/albums/...psc075d21e.jpg




Still plenty of refinements to make, however this is the sort of thing I'm going for on Archangel. Those Hardox bulkheads are 233mm front to back and 5mm thick, will be welded together with a 30mm fixed shaft acting as the 4th wall on that inner box, if that makes sense?

Black sections are HDPE, and the box section bits are mild steel - 4mm wall, 50x60mm. Bar's 330mm now and about 4kg.

It's 530mm wide too, not including those wheels (which are only placeholders, as is the bar) - do intend to have a single toothed bar and some monstrously chunky wheels but you can get the rough idea of what I'm going for with this! Still plenty of improvements to be made, but it's on the way now to being finalised.

I like the rear wedges / stabilisers :). There seems to be more 'dead air' than needed in that central section; I'd look at moving the bulkheads in towards the blade a bit to give you more space for parts in the rest of the frame - it won't affect the strength either way and might save weight by allowing a smaller frame. Also with those bulkheads, adding some cut-outs in the area just behind the box section will save plenty of weight with hardly any strength reduction.

Those small triangular front wedges are going to get hammered by horizontal spinners; of course if NST is retired for next year, you won't have anything to worry about :). You might still want to make them out of two layers of Hardox. The floor level front prongs are also going to be spinner bait; depending on how far out they stick, you might find floor scraping spinners like 720 will hit them before you make weapon contact. Based on fighting Demon for years, I would change the prongs to just one wider and shorter prong which will be stronger for the same or less weight.

Thanks! I got the idea after seeing how Demon occasionally flips itself over backwards, thought it'd be handy to keep everything on the floor at least!

The plan (though I realise it's not clear in the slightest from that awful, awful CAD) was actually to have both the front and back wedge things as bolt-on pieces so I could replace them if needs be, or just do away with them entirely if fighting a drum. Would need to watch the speed of the bar though, given I'd not have the stabilisers on it!

Regards the bulkheads, I need to refine the whole weapon system so I can push them closer together, it's an NTM 5060 that and already is half sunk into the bulkhead , need to get that sorted as soon as I've refined the mounting method too (thinking an aluminium block which would then be bolted onto the bulkhead itself). I will certainly look at some cut-outs though! I'm going to attempt to learn to use a higher end CAD software that has the stress-testing function to see exactly what I could cut out without losing any strength.

Hopefully I'll end up learning to CAD properly sometime soon and can keep making adjustments but it's a lot tougher than I thought haha!

Well, the inevitable's happened and Archangel's had to be shelved for the time being. Because 'massive vertical bar spinner' and 'student budget' don't seem to get along too well. Instead, I'll be putting HardWired 2 back in the ring. Probably with a weapon though!

On that side of things, does anyone know if there's anywhere else other than AlienPower that sells sensored outrunners? Alien's have been out of stock for quite a while now if I recall rightly, rather hoping they haven't gone out of production for good...

I know of one other place and they have been out of stock for a year or more :(. I can't see why sensored outrunners are so scarce!

I would assume it's because they're 'custom' (at least in the case of Alienpower) but I can't understand it either to be honest! Rather wish Hobbyking would do a range of sensored NTMs but I don't know if that'd work out cost effective for them...

Shame though, guess I'll just have to keep waiting for the Aliens to come back in stock!

Actually, I've just seen this on there... http://alienpowersystem.com/shop/ser...nsors-service/
Not sure if this replaces the existing stock of sensored outrunners!

Question for anyone who's relatively spinner-savvy, are inrunners or outrunners better for a small, high RPM disc?

Plan I have at the minute is to go for a 150mm OD single tooth disc, probably made of 10mm hardox 500 (or whatever gets it to about 1/1.5kg) on 20mm HDPE bulkheads (fixed shaft if possible) and I'd like to aim for around 10-15,000 rpm which might be pushing it a bit but means it'd get some very nice engagements. There are a few outrunners that would do it on the 6S I'm planning to use at maybe 1:1/2:1 sort of ratio, but is it a smarter idea to just go for an inrunner and gear down some more?

The problem with using a small diameter disk is that there is less space to use a high reduction unless you want to risk the pulley on the disk getting hit. In this scenario, I would go for a high KV inrunner and a lower gear reduction. Will the disk be single toothed? 10K rpm and above is a bit high for a multi-toothed disk.

Definitely single tooth, more awkward to design I guess but definitely worth the effort!

As for motors, I'd spotted this - http://www.hobbyking.com/hobbyking/s...or_2350KV.html which for, let's say a 15k-ish rpm on 5S would need a 3:1 reduction... Not sure if that'll be good enough though. I don't know how brushless motors react to overvolting either, but it could be an option to run it on 6s, perhaps?

In an ideal world I'd like to put a really small pulley on the disc and essentially hide that within the bulkheads, but it's if the reduction suits it really. 2-stage isn't that much of an option given it's going to be sitting on top of a machine that's no bigger than a postage stamp either!

I'd say that 150mm is too small for a disc, especially considering there are beetle weapons bigger (Newton/Red Wedding). I'd say go for 200mm OD and make it closer to 2kg, that should give some nice impacts.

He is restricted by weight and size due to the geometry and current weight of the machine. Ideally you should go for the biggest Diameter you can but looking at Rango its not totally necessary if you have out right speed. I cant remember the graph shape but you can gain back your RMI in speed but doing it in the mass of the weapon is ^2 in terms of efficiency... I may have that wrong.

A 1.5-1.8Kg Rango style Drisk doing 12'5000 would pack a massive punch either way!

If the size permitted, I'd definitely go for something huge to get a really powerful spinner, but I'm having to make it super compact given it's an addition to a machine which didn't have a great deal of internal space anyway, but also because I'm building the uberspinner (Archangel) at some point in the future, this is more just a small spinner to help add to the existing pushing power.

Also, if we're using the 'there are beetleweight weapons bigger than that' argument... Lynx says hello ;) (in fact, I'm fairly sure Lynx's bar is bigger than HardWired 2 itself...)
I'd go bigger with it all, but it presents so many problems by doing that really... I do have about 4/4.5kg to play with but I'm adding some more armour and a few bits of things to improve general reliability and I'm not sure how much that'll add!

The inspiration is somewhere between Rango and Enigma I guess, it's not designed to be the most damaging thing in the world, but consistent hits and that high speed are pretty vital to the whole thing. I don't mind changing it to be a more drum/disc hybrid thing but I'd rather keep it as a plain disc for now if I can get away with it!

~Sorry if I sound daft but is this the same robot the money's run out for or is that another one? I couldn't work out if you had a few feathers on the go.

I have more feathers on the go than there are machines that compete in the champs haha

Seriously though, this is just a bunch of upgrades to HW2 to make it more competitive (and weaponised), Archangel (the one that the money ran out for) is going on the shelf for a bit until I get the cash to do it properly. I've got a few other plans in the pipeline for potential feather designs, but I doubt any of those will make it past the drawing board to be honest.

If you want to keep the pulleys as small as possible, that means using a timing belt. All belts have a minimum pulley radius and the thinner the belt, the smaller the radius. Just keep in mind that the smaller the motor pulley is, the more likely it is to slip and strip the teeth off the belt.

In theory, brushless motors should over-volt better than brushed motors; they are more efficient and generate less heat, plus they don't have brushes to burn up. The main problem is still overheating; most brushless motors don't like to get over 60 or 70 deg. C. If you used a motor that is power full enough for the job and has some built-in cooling, then over-volting shouldn't be an issue.

Keep in mind that the motor you linked to has a maximum power rating of 2,400W and the continuous rating will be half that or less.

Lynx's weapon WAS bigger than Hardwired, i've seen sense and had the new one designed at 250mm...that's sensible...right?

I don't really see the problem only having the disc/drum at 150mm, if it's for HW2 i'm guessing you'll be using it as more of a kinetic flipper alongside the robots speed. Besides how big is the disc on Satan's Mutt? if i remember correctly it had enough power to flip robots up in the air and it was only about the size of an ants bumhole.

Yeah, that's my worry with going smaller, Nick - I've learned that in a roundabout way with wheels too!

I'm more than happy to amend the motor too depending on what I can find/afford (got to get a working drive system/battery and this done for £250-ish at the most) but I think that may be a nice starting point - after all, I'll be pulling the most current on startup I'd imagine and 2.4kw sounds like enough. Of course, I've not a single clue as to whether this is actually enough but the potential for overvolting may make it more viable. Could be worth a few experiments at least if it comes to that!

That bar was insane too Sam, I did measure the dimensions you gave me for the machine against HardWired, and you've either built a feather-size beetle, or I've built a beetle-size feather haha
The idea for the disc was basically along the same lines as Rango/540 used their spinners, drive being the focal point and then the spinner being there to add just a dash of chaos into the mix haha. After seeing the hits that Rango and 720 got this year though by driving into things at relative speed, I think the engagements it could make at high RPM might potentially be utterly insane... but time will tell!

Have you thought about axle size and bearings for the disk? Its a real PITA trying to get a small pulley and a large bearing fitted into the hub of a disk.

Ideally I'd like to go for a 20mm axle, may be OTT but makes it reliable at least. I was tempted to go for a fixed shaft and bushings on it rather than bearings, but I'll see how the cardboard mockups go and work from there, might be better going for conventional bearings in the end