"Precision engineering" I laughed so much
Looks just like my new bot too!
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"Precision engineering" I laughed so much
Looks just like my new bot too!
Looks like, but is probably built a LOT better than this monstrosity haha!
I don't think I did that bad considering time/money/tool constraints, but the next one will at least look passable!
Going to try and make something a bit more robust internally, then pile wood on the outside so spinners have something nice to chew on haha
This is so awesome!! Pls can you put pictures up of the insides!
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Best picture I have! It's extremely basic, just a pair of drills, drill battery and receiver. It's as basic as it gets, but it works I guess!
Not bad for a bunch of scrap parts I wouldn't say haha. Really won't last long in battle though! Do intend a rebuild with a (thin) aluminium inner shell, and a ton of balsa/ply round the edge to let it get battered, still be extremely cheap to do but it'll look pretty spectacular, especially at the spinner events!
Archangel Rises!
So, it's been a while since I've done a proper update, and now thanks to help from Alex (designing the bar) and Jarvis (Cad'ing up the machine), here's Archangel!
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It's a 200mm radius single tooth bar, powered by a Scorpion 5020 450kv on a 4Ah Optipower 6s, 1.4/1.5:1 ish ratio leading to about 7000 rpm. Tip speed is upwards of 230mph, and with a sharp tooth it'll cause plenty of damage! Rather hoping it'll tear holes in Hardox, definitely seems like it has the potential to!
Drive at the minute is 775 banebots, at present 16:1 on 124mm wheels but I'm looking at maybe going 64:1 because magnets, but I'll get to that in a minute.
The black material is all HDPE, on this Cad it's 10mm but I'm thinking that could be upgraded a little, potentially, if not reinforced with some other kind of material. The rust coloured stuff is 3.2 hardox, but bent into shape rather than welded (though could still be welded, just helps to keep the strength up) and I'm maybe going to reinforce that at some point with HDPE too if needs be. Bulkheads are aluminium, looking at 7075 or just some kind of good grade, would like alumec but I'm told that's really expensive... heavily machined of course, given the size. Fixed 20mm shaft, seems like a far better option than a free one in this type of design at least!
The base is 3.2-4mm stainless, which will have magnets dotted around the wheels, I'd like to say something like 100 kg of magnets would keep it stable, but that'll be a heavy strain on the motors and will probably cause problems against other spinners, so maybe an absolute maximum of 20kg around the wheels, keep those on the ground, or at least keep the machine from tipping when it turns! I could alternatively go with maybe 100kg and have 64:1 motors, but that'd lead to about 6mph top speed which wouldn't be that fun. I think it's going to be more a case of trial and error than anything...
But yeah, that's Archangel, there'll be plenty of little refinements and adjustments to make as the build goes along I'd bet but that's the bulk of the machine. Won't be long until I can start building it, hopefully!
Big thanks again to Alex and Jarvis for the help!
I like the design and the bar looks deadly, it would get good engagement at RPM and bar diameter aswell.
Thanks! It's roughly based on Electric Boogaloo from the US, that seems pretty scary so why not haha
I think Alex said to me that the bar has 60mm of bite at 7000rpm, which would be insanely scary! good news too as it means that I can up the voltage a little bit at a later time if I feel a little bit idiotic to get even higher speeds with a still usable bite...
Yeah its a pretty successful robot from what I've seen, nice to see a vertical bar too. And at 7000rpm you probably wouldn't need magnets at all, the robot should be fairly stable with the width on the CAD model, I'd also worry that at 6S, the motors will be worked too hard with the reistance of magnets on top of the over voltage, thats assuming they are the 18v ones.
Very! I believe it was ranked 3rd in the 2012 Combots cup after only ever competing at Robogames before or something? It really does hit hard that one! I believe a lot of it is in the bar design, it's a weird kind of single tooth, quite different from this one though I hope they perform similarly!
Thanks, I never thought of that! I'd have just assumed they'd kick out more torque to deal with it! Still pretty new to motors as a whole haha
It might be that I either go for a split battery (5s and a 6s) or see how it goes without magnets after it's built. It can run inverted so if it does lift it can get back over... just don't want it to be near enough uncontrollable! They are the 18v ones too, I've been having a look to see if there's the equivalent motor in 24v but don't seem to be having much luck.
I think magnet-less could work too but may need simply to get good at driving it... I might leave at least a little bit of magnet downforce in there to reduce the likeliness of it lifting, but perhaps nothing as substantial as it was. Like I said earlier, it might end up being a trial and error sort of thing, see how it copes with everything. Might be worth trialing a set of Banebots drives on 6s to see how it copes in that sense, I know if they stall at that voltage, I can say goodbye to my speed controllers haha!
Archangel has a great design and will pack a huge punch. You might want to reconsider the weapon motor though; the 5020 is meant to run at 12S and on a 6S pack, its only going to produce 942 watts (1/4 power) and top no-load speed with a 1.5:1 reduction of 6,600 rpm. You will need to go to about a 10S, 37V pack to realistically get the bar spinning at the speed you want, or find a motor with at least an 850KV rating to stay with 6S packs.
Without knowing the weight and MOI of the bar its hard to work out the power rating of the motor needed to run it. Some of the best high KV motors I found are the Scorpion HKIII-4025-890KV Motor and the Hacker A50-8S Turnado V3 Motor - they may have the power & torque to spin that bar up with a 2:1 reduction.
I think the smartest thing is to use two 5S packs with a bit lower AH rating and then do split voltage wiring like I did in Mr Mangle. that will give you 5S to keep the 775 motors happy and 10S for the 5020 Scorpion motor. You could go with completely separate packs for the weapon & motor, but its likely to weigh more.
I'm planning to run the same drive setup at 6S too on my new robot, I'm hoping they will take the extra bit of voltage ok, just need to make sure there is lots of airflow around them and it should all be fine :) split batteries could be good if you have the weight and space for it, which I don't.
775'S on 16:1 with 124mm wheels with magnets wont be very reliable, without magnets its the same as drumroll i think, so should be pretty quick.... maybe a tad too quick for a vertical bar that big... you'll find turning difficult.
200mm radius.... 400mm OD? Pretty big! should be good.
The initial design weighed in at a theoretical 12.6kg, with the 6S 5000mAh 50C Lipo and 16:1 gearboxes, assuming the weight of the bar to be in the realm of 3kg. This factors in everything, the weight of the belt and pulleys, the 20mm weapon shaft, bolts and 8mm ali motor mounts. With the bigger and slightly heavier 64:1 gearboxes and 2 5S 3650mAh packs instead of the monster 6S, it comes in at 13.1-ish, allowing a bit of room for error. This is the current layout in CAD:
http://i1234.photobucket.com/albums/...ps37e7ccb5.png
As you can see the two batteries and slightly longer gearboxes fit into the chassis easily.
I always design towards a goal of around 13kg so I have some spare weight for error and/or any modifications or additions that need making. On 10S the weapon ratio would need to be ~2.5:1 to achieve the 7000rpm desired. The 64:1 gearboxes will give a max speed of 5mph, which is a bit on the slow side but might come in handy in a pushing match, not to mention the added control it'll give.
Cheers Nick! I hope so, I think with 60mm of bite and 3.5kg of bar, it may end up getting a few big hits! Just need to make sure everything's up to scratch when I build it to make sure it can take the force in the case of a really good hit... would hate for it to break itself!
I'm not too sure of the MOI of the bar, I'm sure that the weight is 3.5, though I may need to double check with Alex on that one...
That's a shame too, but I guess I could work with that. I always thought that it was that the motor always kicked out as much power as it had on tap, but efficiency and speed was dictated by the voltage... Might mean a slight redesign, I do like the idea of split voltage (seems to work great in Mr Mangle) so might be a route to explore. Failing that, I'm sure there could be other lower voltage motors to fit... could be a case of going for 5s and running it all off one beefy pack or something!
It might be a little bit fast too Dave, it's just a shame that Banebots don't really do anything between 16:1 and 64:1 reductions! Granted I could get smart with some belts and do a 16:1 with a 2:1 from motor to wheel, but I'm not sure that's the best way to do it... I could also have something custom made but I'd imagine that'd be pretty expensive and I've had it if a gearbox goes! It is indeed too, there abouts 400mm, should hopefully make a few nice dents! I'll see how reliable it is when it's built and how it handles, but I'm very tempted to drive this instead of HardWired 2 in next year's championships...
Thanks too Jarvis, that's a huge hand! There's plenty of space in it, so for once with my machines room isn't an issue! I'll have to watch the weight during the build naturally, but I reckon that'd work well. I'm still a little concerned about it only being 5mph but that might bring more benefits than having it go crazy fast on the 16:1s! I think if I can find a way to get it to more 32:1 territory that'd be ideal, but I feel that's going to involve more messing about than it'd be worth or expensive custom part territory, neither of which would be preferable!
As a side note, does anyone know how much the import tax or whatever on the Banebots stuff is? I've never bought from the US before so it's still a grey area for me!
I think banebots do a 4:1 gearbox, so maybe it is possible to combine this with the 16:1? Might be more compact than a belt system, not sure if its possible to combine them like this though..
It could be managed if it came to it, though that'd give 64:1 I think, their 64:1 gearbox is three stages of 4:1 (the 16:1 is two stages of 4:1) so would just be better going for the 64:1 in that case, assuming I've got my numbers right!
Yeah, my mistake - that would definitely be a better way of doing it lol, would it also be an idea to have the wheels further to the front to help stop gyro? I guess they can't go much further forwards whilst also keeping the robot invertible though, and not as much weight will be at the front to get under other robots.
I could do but it then loses invertibility. Granted with a bar that big it'll probably get itself back over with that, but in a worst case scenario when I don't have the bar, I'd like to be able to push things about a little bit. I guess 4WD (with belts) could be a thing with some major weight saving but I can't imagine it'd help too much...
Tiny little bit of magnet downforce round the wheels and some driving practise might help solve the gyro-ing though! I think you'll always get it on vertical spinners like this, it's more learning to deal with it than negating it entirely I think... gyro effects shouldn't be too bad at lower RPMs and if I get a motor that allows for quick acceleration I'll just stick the power on when I'm lined up!
If you want something mid, go for the 16:1 and an additional 2:1 reduction with some belts or something, will give the desired speed plus will limit the stresses on the gearboxes as they wont be in direct contact with the wheels
That was an idea but I'm a bit worried about how it'd affect weight distribution, if I moved the motors back to fit a belt drive in there there'd be very little weight over the wheels, so it'd probably not drive so well, I'd assume...
How thick is the bar? I can't see how that design weighs 3.5kg, as it looks quite thin. Also, a design like that looks menacing but the MOI for the weight will be quite low, as much of the mass is near the bore (in the counterweight).
A shape like this measures 200mm tip-bore and has an offset bite of about 17mm, but it would have to be more than 15mm thick to weigh 3.5kg... http://i.artangle.net/t/P8F.PNG - could be made to look nastier, just an example. It could be mostly 10-12mm thick with thicker ends to bump up the MOI.
Can't see how the one in the CAD weighs the same? It looks like it's mostly 6-8mm thick?
Either way it will be nice to see a bigole vertical bar spinner, they're always intimidating!
This may be worth looking at as a banebots alternative- http://www.vexrobotics.com/vexpro/ge...planetary.html
Drumthing Else ran a pair for drive at Motorama with 775's iirc and the gearboxes seemed to hold up fine.
A pair of ruggedized Gimson GR02's with 18V motors* and 36-1 gearratio will do well enough I think.
Put everything on 5S and simplify the logistics train a lot.
* 2500-3000 KV Brushless inrunners with 1/8" axles are a possible replacement for the original motors.
@Ellis; The bar in CAD is quite possibly thinner than the actual design, Alex designed it and I roughly remade the shape with the same dimensions in the CAD. This may give a better idea:
https://fbcdn-sphotos-h-a.akamaihd.n...ba94249396eec4
@Mike; That URL gives me a 404 :/
The bar in cad weighs 3.6kg. Its made of 3 pieces of 10mm thick steel (Could be Hardox or stainless or whatever) Its 400mm effective radius with 60mm of bite.
That explains it! The massive tooth is pretty awesome.
With some clever wiring you can set it up so that with 2 5S packs one powers each drive motor and they both power the weapon. You would need 2 links and high discharge lipos but it would give you the 2 voltages in the same system. the atlernative is two totally independent systems like in Binky & Conker: binky running a 2.6Ah 4S for drive and 2x 2.6Ah 5S for weapon. Conker has 1x 3.3Ah 4S for drive and 2x 2.7Ah 6S for the weapon.
There is no UK distributor for the Vex Pro components. I had a long dialogue with the current Vex distributor but it didnt seem to get to the point of him picking up the Vex Pro line. So the only alternative is order direct from the US with very high courier costsQuote:
Originally Posted by MikeNCR
You can always gear down with smaller wheels. To keep the inverted driving ability, add a set of friction driven wheels above the regular pair. By the time you get around to buying parts there may be a brushless motor option with the right KV or a 3mm shaft that will work on 26:1 Banebots gearboxes - just keep your options open as long as possible.
I did a very rough kinetic energy calc using a straight steel bar with the weight & diameter you mentioned - 11.1 Kj at 7K rpm! Your bar has more weight at the tips so its going to have an even higher energy. That would probably be the highest energy rating for a featherweight in the UK.
Update: with a 3.6Kg weight, a straight bar would have more like 13.5Kj
I have a pair of those and they are VERY disappointing! The internal gears are fine, but the output shaft is aluminium :(. Its also quite short at 1.5", so you can only use a very narrow wheel if you want to use an outside support bearing. Changing the shaft to steel might be possible but looks like more work than most people will want to do. If VEX came out with a better output shaft, I would definitely recommend them.Quote:
Originally Posted by MikeNCR
Yeah, I really like the massive tooth on it! I guess things could always be refined but the general idea seems to be spot on! I'd possibly like to up the diameter of the bar's shaft a little (20mm to maybe 25/30) to account for the power in it, but I don't think it'll be too big of an issue considering it's fixed.
The tradeoff with such huge bite is that it might not have as much KE in it I think, however it does mean if I'm feeling truly insane I can maybe up the speed and still get nice bite. 14000 rpm anyone? (I'm kidding, that really would cause absolute carnage, for precisely one hit. If I could hobble over to another machine before everything got all nice and firey electronics-wise.)
Keeping options as open as possible like Nick says is probably my best plan here. I like Mario's suggestion of the strengthened GR02's since that'd help save a nice bit of weight that could go on helping strengthen everything else (or even extra batteries). Those Versa gearmotors look pretty decent too, Mike, but the problem is that the site's saying they don't ship to Europe... which could be a bother. I do like how they appear to be customisable though, might be a good way to get the exact reduction I'd need!
I'm thinking having dual voltages through separate systems may be a better option in this case, it's more weight but perhaps it'll end up working better, especially if I have a 4s/5s drive and something like a 12s weapon motor. I don't know, but I certainly will keep my eye out for motors that may be more efficient at a lower voltage. Probably will look into the types of motors that such as Demon or maybe even Unmakerbot use for inspiration. Particularly Demon, because Demon terrifies me with how brutal that is...
I've been looking at the design too, and perhaps the wedge at the back being how it is may be a little unnecessary? I don't know, perhaps a more angled slope and less long design, but keep it as wide? Could have a little angled tail at the back too to house the bulkheads whilst keeping the wheels to the front... wouldn't be able to be invertible though if I did that, though could possibly allow me more weight to go towards making the belt/bar system as reliable as it can get... It would, however, make things a tighter squeeze inside the machine and I'm not entirely sure how I feel about that! Shock mounting is definitely something I'm looking into more across the board too, it was certainly my downfall this year.
That's downright scary as well Nick, from the sounds of things - thanks! 11-13kj might cause some serious carnage! I'm almost starting to worry about keeping it in the arena at this rate, it'll just take something to catch it right and it's off out, though I suppose that is the danger with spinners!
Starting to sound crazy powerful lol, also what you said about the belts upping the ratio with banebot gearboxes and what matt said about having the motors not directly attached to the gearboxes might be a good idea with the energy that could be going through the system, maybe you could do some kind of suspension or shock mounting with this? goodluck with the build.
I did the maths on the bite depth and with weapon at full speed and the bot moving at around 14 KPH ( what it would do with 775 motors and 32:1 reduction) the bite depth is 35mm, still very destructive. Once you finalise the choice of the drive train and it's top speed. you can adjust the bar design to make the counterweight side longer and lighter, like Ellis pointed out. I can put the maths into a spreadsheet for you if you want to run different scenarios.
With the gearboxes, the GR02 sounds ideal for lower weight and the gearing is about right without messing about with extra belts. The VEX gearboxes can be bought from resellers that ship internationally, I found a couple with Google if you want to go that way. I am testing a pair out with in-runner motors and so far, I like the results.
Glen used a custom wound Scorpion in Demon, but he has recently upgraded it to a larger model, making it even more lethal. To swing a large diameter blade like yours, you either need some good start-up torque of lots of gear reduction. Whatever you chose, I would go for the largest diameter outrunner as they have more start-up torque. If I was going to pick a dream motor, it would be a Scorpion 50 series with a custom winding to get a higher KV.
The wedge at the back worried me; if an opponent drove up it the weapon would act as a high speed crusher on the down stroke and much of the blade's energy would be transmitted into the frame. If the bar hit something really solid, the frame could get severely bent. I would still give the back panel a slope, just not enough to wedge up an opponent.
@ Andy: with a vertical spinner, you don't want any suspension as it wastes impact energy - the stiffer the frame and wheels, the better the hits. Adding outside support bearings would be a really good idea though, the gearbox axles will need to take a beating.
Update on those VEX gearboxes: one of mine just jammed solid after barely 5 minutes running with no load. They are complete junk and not worth using at any price!
That's still pretty strong, thanks Nick!
My understanding is that with more bite there's less KE, but the more bite you get the more of that KE can be transferred into the target?
Yeah, I think the back may go to being a little more like Hardwired 2's is with a slightly slanted piece of something, maybe just HDPE to allow for a little bit of ability to push and resistance from spinners but nothing too wedgey... It does mean I'd not be able to run invertible wheels maybe but I guess that's just a tradeoff I'll have to take. Besides, I don't think I'll need it if I can put that weight being saved into making the bar more reliable, since it'll right itself anyway when the bar catches the floor or something!
Whilst it may seem completely OTT, would something like this perhaps be suitable? http://www.scorpionsystem.com/catalo...KIII_5035_500/
It's a lot of power, though perhaps with a custom winding for higher KV, it'd be something quite powerful, and maybe a motor that size not running on it maximum capacity might not get as warm either? Granted I'll need to make provisions elsewhere because it's quite a big motor, but I'm sure I could save it by chopping some of the back scoop off and running GR02s or something. Mario's suggested brushless too which could save a nice bit of weight as well, assuming the speed controllers are also light (which the stats say they are).
If that's a little much (7kw peak probably is) then there's the 5020 which is 4kw continuous and about 5.5 peak, which should do just as well. That extra bit of power might make startup a lot nicer though, perhaps... I could attempt to go for the best of both worlds and try a KV rating towards 1000 and go for more belt reduction, maybe 3:1 or something. At 6s that'd be ideal, though I do intend to try and up it to something a little crazier like 10 or 12s at some point for extra punch but it's a question of how reliable it'd be on that sort of voltage as well as if the rest of the machine would take it...
I'm looking at ways to save weight armour-wise if it's needed too, the front plate will be hardox and aluminium bulkheads, but everything else will be hdpe I think.
That solves a debate with the VEX gearboxes haha! Wouldn't want that to happen whilst they're in a machine...
The 5035 is probably overkill, and on 6S it probably wouldn't pay off as Nick mentioned about the 50 motor in an earlier post. It would probably be better do use a hk40 with a higher kv and gear it down more, cheaper too :p
KE and bite are not directly related, the RPM of the blade is the only thing they have in common. For a high KV, you want plenty of weight (better if its distributed out to the edge) and high speed. For more bite, you want either less speed or fewer teeth, plus a higher driving speed.
As your design has a heavy blade going at a pretty high RPM with only one tooth, you have the best combination of high KV with a large bite depth to help transfer the energy into opponents. About the only thing to change is moving the counterweight a bit further out and making it lighter.
You can probably still run inverted with less sloped rear armour, the wheels would just need to be moved further back. This bot has vertical rear armour and could still theoretically drive inverted:
http://www.nswrfc.org/Nick/P2160083.JPG
The only problem with moving the wheels to the back is that there is less weight over them and they get less traction - its all about compromising one way or the other.
The weapon motor is tricky; its probably better to go for more gearing and limit the motor size a bit - I can't find any large, high KV motors in the first place. Just looking at the Scorpion range, the largest motor with a KV over 600 is the HK3 4025 series. All the larger motors are around the 500KV mark and higher voltage. An over-sized motor is definitely going to run cooler, its a question of whether there is the space and weight to fit it.
It is total overkill. Conker Runs a HK 5020 on 12S and gets 11000 at the weapon, with a 2:1 reduction. I ran that as it was a better shape for my machine than the longer HK 4035. The massive stator give it a huge amount of torque. I believe you could run it 1:1 on that bar and be fine, so long as you ran 10S or more.Quote:
Originally Posted by Andy
The alternative is go like 720, running a 5S pack and have a high KV inrunner and a greater reduction. It simplifies your wiring and means you can save on the cost of batteries, and high voltage ESC's. However I believe in a machine shaped like yours that a HK 50 would fit in better than a long thin inrunner.
EDIT: I have also tweaked the weapon design to have 40mm of bite rather than 60, and it now weighs 3.45kg. With all the bearings and supporting parts it will weigh around 4Kg... that is one hell of a weapon!
Are you referring to how much offset there is between the tooth tip and the counterweight? Because the maximum (theoretical, and so in unrealistically perfect conditions) bite is just 23mm (6mph and 7k on bar). That's based on the lip/edge you're going to hit entering the sweep of the tooth the instant after it passes by, getting full depth bite on the next rotation. A 15-20mm offset will give a very marked single tooth effect and a higher MOI, as there is more mass further from the shaft.
To contain the amount of energy in a bar like this won't be easy! :P