HardWired II

[overkill]

What Ellis said! Even if if the bite depth increases due to the weapon running slowly, the worst case is that the counterweight hits the opponent. Just fashion a small cutting tip on the counterweight and its going to do fine.

@ Alex: Reducing the gear ratio has a huge impact on the spin-up time; it increases with the square of the gearing. The motor power required also increases by the same amount.

[Eventorizon]

@ Alex: Reducing the gear ratio has a huge impact on the spin-up time; it increases with the square of the gearing. The motor power required also increases by the same amount.

Conker 3 goes from 0 to 11'000 rpm in less than 1 second when I need it too. And that is with the massive amount of air resistance. On 3:1 that would give Matt a 260mph weapon. I understand why people go for the inrunner I am just giving him an alternative which I believe better suits his machine.

[Eventorizon]

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).

I went with the 35mm that Nick gave a few posts back. I cant see 15mm or less making a difference on the weapon. The RMI increase will be negligible in comparison to the total RMI.

[overkill]

I did notice Conker 3 spin up very fast, I'm just not sure about this bar with probably quite a bit more MOI and 1:1 gearing. I'm more of a fan of high motor RPM and plenty of reduction.

[Eventorizon]

The newer bar has an RMI of 45877! C3's old weapon has just 5008... Wow! 9x the inertia!

OK... I am not sure what that means for motor choice but I would still say that the HK 5020 would do the job. Maybe you would need 4:1 or even 5:1.

[overkill]

Um, what does RMI stand for?

[Eventorizon]

Rotational Moment of Inertia. Solidworks give it to you in in the Mass Evaluation tool in each place and axis, and around the objects centre off mass and the origin.
On its own its not much use but its great for comparing designs. I think as I have weird settings the numbers are in Kg/mm.

[overkill]

OK, the same as MOI. Its a very useful value to know as its possible to calculate the exact KE for any speed.

EDIT: I think its also now possible to calculate some of the motor specifications, particularly the average power needed to spin up the bar in a specified time. The maths is a bit daunting but I will see if I can get my head around it - I really should have paid more attention in maths class

[Eventorizon]

OK, the same as MOI. Its a very useful value to know as its possible to calculate the exact KE for any speed.

EDIT: I think its also now possible to calculate some of the motor specifications, particularly the average power needed to spin up the bar in a specified time. The maths is a bit daunting but I will see if I can get my head around it - I really should have paid more attention in maths class

I remember Grant showed me how to do it when he was explaining how he made Predator so potent. The weapon RMI, the gearing and the motor power are perfectly optimised. You put in the RMI and the speed you wanted and a time and it spat out a wattage that was needed for a 1:1 ratio which you could then tweak for other ratios.

[Flag Captured]

My phone doesn't like this site too much for some reason, sorry about the late response!

Catastrophe is a very good machine so any pointers I can take from it are good! I am a little concerned about the lack of grip though that could be caused by it, mainly because the vast majority of the weight will be where the weapon is, so a lot less over the wheels. Same reason HardWired 2 was driving on ice this year I think... It's worth a try though, I'll get semi-decent at CAD then I'll see how it goes (or sketch it, that could also work) and go from there! I do think those supporting beams that Demon and Catastrophe both have on their bulkheads may be a useful idea to borrow too...

I think there'd be enough space to use a motor like that, maybe an inrunner may be too long to fit in effectively, perhaps. If it's a huge advantage though I guess there could always be a redesign or something, albeit wouldn't need to be major but I could get it to work hopefully! I still would like to try and get a custom winding on a Scorpion though, I'm not sure how doable it is but I guess a higher KV motor on high voltage with more gear down would give me the best of both worlds, right? I probably need to lern 2 engineer some more haha

Thanks for the explanation too, that clears it up! I think a cutting edge might work nice on the counter weight but even if it is going moderately slow I'm sure it'd still do something, sharp or not - might be something to look into though! I am looking at maybe having a pair of bars at some point, one designed to cut and another designed with blunt teeth to bludgeon or something purely because of those thick HDPE armoured machines, I guess it's potential that a sharp cutting blade could get stuck in the side of one or something... bit more of a side issue that but I suppose it's something to consider!

That sounds ludicrously dangerous too Alex, cheers! If I can keep that bar where it needs to be and spinning at full pelt, there'll be some pretty huge hits at next year's champs... Can start fitting your robots with parachutes now if you want
Do you happen to have that calculation to hand too? That'd be really handy to work out, much as I want to have a 1.21 gigawatt motor it's a lot better to have something balanced... Or even if I do keep a 50-series Scorpion and can get one wound for a higher KV, I could then gear it down to a much more efficient level or something.

One thing I do want is a tiny little bit of slip in the belt (or something along those lines) for when the bar hits, purely to limit any damage to the motor - I know it just happens sometimes but given how much energy is in that bar, the last thing I want is for each hit to write off a motor or something like that!

[Mouldy]

Do your self a favour dont bother trying to mod a scorpion there awesome out of the box... and more importantly there built to be reliable... also stop talking maths... its going to be sweet... start cutting metal and upload some pics!

[Flag Captured]

Haha, I wouldn't touch it with a barge pole, I'm nervous enough about taking the back off one of HardWired 2's 900s to fix that, don't think I'd even attempt to change an even more expensive scorpion!

It might be worth looking at the inrunner options then too, truth be told I do need an inrunner (and an outrunner) for another project at some point so maybe making a mount that would suit both could work... More expensive but I'd be needing one of each anyway - see how both behave!
Personally I'm liking the outrunner option for size, but the inrunner might end up being more preferable voltage wise, and I'd worry about finding an inrunner that could cope with spinning the bar up to speeds I'd want it at at a lower voltage...

Got no money at the minute with which to buy stuff for it, but come September I'll be getting plenty done! I hope it's pretty menacing... I'll probably end up with the two sides of the coin by the time I'm done, Archangel being all offence and HardWired being all defense haha

I do like the maths though, I see the big numbers and in my mind I'm hearing this https://www.youtube.com/watch?v=e_DqV1xdf-Y

Won't be too long though I'd imagine, I'd like to get it done before the year's out, by the end of January at the very latest... HardWired 2 wasn't finished till the week before the champs and it definitely showed in my driving ability! Need plenty of practice this year, certainly...

[overkill]

Custom winding a Scorpion using one of their kits would give you more power with your choice of KV but its not for the faint-hearted and plenty of research is needed! Its probably a 'plan C' rather than a first choice.

Part of Catastrophe's driving problems are simply the no-grip wheels; they are a a very hard compound and the Banebots wheels will undoubtedly do better. Ideally, the wheels should be right up at the front, but then inverted driving is not an option.

I will see if I can work all that maths into a spreadsheet and maybe do a table or a graph to visualise how various design changes affect the performance.

[GlenR]

Sup yall, That design looks good! Wheel placement and all looks nice

The 4*** series scorpions are wildly powerful! Demon has a 3L V-belt and it slips non stop at anything above 2000w~ the 4035 puts out much more than that so i would say going to the 5*** size is abit much if you're trying to keep the weight down, however the bigger diameter motor will draw less current so if you're having battery problems it might be worth trying (that's the reason i have upsized).

With the rewinds, Demons blade pulley is integral to the bearing block on the disk so it's size is fixed. It used to run the old 3026-880kv which is the lowest powered variant they had by 300w or so. I wanted the power of the higher KV versions but the stock speed so i pulled it apart and rewound it given i had two partially burnt ones. Definitely don't recommend it The stators are epoxy dipped so you have to heat gun it as you slowly unwrap the individual winds, half the time the stator insulation comes off with it and that needs to get redone. So so tedious... That was all due to having to make do with the original design constraints, Just design around an existing scorpion motor and you'll be fine. Although they have an aggrevating habit of changing specs constantly. Good luck trying to buy the same motor 2 years from now

Catastrophe runs some cruddy 5*** size $30 motor from hobbyking and it draws next to no current nor builds much heat at all. It's a really nice setup, but heavy. IMHO use one of those to begin with then get a scorpion if you need the additional power. I doubt you will though, they have so much torque Specially the SK3 turnigys which are rebranded hacker outrunners.

The support bars - They're an afterthought too :P Catastrophes weapon arms are way too small as you can see from the mega amount of pocketing, plus the way it was designed means they couldnt be welded on fully (cant get the tig torch in where the front plate slopes in). Demon has a big cut out in the base the blade runs through so the vertical arms weren't rigid enough at all thus the support arms. Surprisingly they work really well, but if the robot is designed proper to begin with you wont need them. Makes working on the robot a pain in the butt too lol.

Shouldn't need a sharp blade for plastic bots. With enough energy it'll just displace the material without slowing the blade down :P I had to fight this plastic square that was about 200mm thick at our last nationals. The disk would just plow straight in as far as it could go lol. Unfortunately doing that for 3 minutes melted my lipoly :P Got outsmarted on that one haha. Looks like most of the plastic armour robots are quite thin in the Uk however. So you should be okay there

Get building

[overkill]

I thought you bought that custom wound 3026 - kudos on getting it done yourself! I think the idea for a custom wound motor was to start with one of the motor kits rather than pull apart a perfectly good Scorpion - still a difficult job though.