HardWired II

[GlenR]

I have both Back when you could order the motors directly from them they'd do specific winds for you. My own are just single larger winds that are apparently better for getting more copper on the stator and the scoprion ones were parralleled fine winds that im lead to believe are easier to wind. They both performed about the same really. The DIY cores are about the same price anyway, easier to just use the existing options unless there's a specific need for a certain KV

[Flag Captured]

Cheers Glen!
I see with the 50-size ones, I am tempted to go for a 50-20/25 because I've seen some cheap ones, though if the belt slips like mad even with smaller motors, it's nice to know I could probably downsize a little! I guess I'm stat chasing a little, but the torque and just general power of those 50-sized motors is something I'd like...

That said, I did find this motor after having a quick look at those SK3s you mentioned http://www.hobbyking.co.uk/hobbyking...ize_heli_.html which is a high power and surprisingly low voltage motor, which could help me out with the whole battery issue, and saves more precious weight that can go onto the bulkheads! Not sure how suitable it is but may be along the right lines! Certainly won't be rewinding one myself though, sounds like it's an incredibly difficult task and it's not really something I reckon I'd be able to do with my tools/skillset haha!

Afterthought the may be, but they seem to do their job nicely! The reason I wondered about using some on Archangel was more to offer protection in case they were to get hit by a horizontal spinner or something... I'll have to mill down the bulkheads a fair bit and I'm worried about their strength as a result. Perhaps I could bolt them to the front/back plates more securely and use those as the support bars?

I think I saw that fight too, Plastic Fantastic or something? That looked a brick of a thing if ever there was one, I feel sorry for the person who had to clean the mess up afterwards! Most over here I believe use around 15-20mm (Ricochet uses the thickest I think at 30mm) so that's plenty below the 200mm mark haha! Won't be too long till the build now I reckon, few creases to work out in the design and then I'm on it!


Side note too, been cracking on a little with HardWired 2's planned upgrades - given that it's designed around Speed 900s which are literally more expensive than solid gold these days, I'm running into plenty of problems now that one of the motors I have is broken... I've had a few ideas, some of which involve cutting the robot in half and replacing the back/middle sections with pieces of longer hardox (same 6.4-7mm thick) and then putting some banebots gearboxes and accompanying brushless motors (high power) in there or something. Effectively, the machine will probably be about 10-ish cm wider. Other option is a silly compact two-stage gearbox (or in-wheel setup) and using those outrunners I posted earlier at about a 16/24:1 ratio or something to carry on with the silly speeds, but enough torque to deal with as many magnets as I'd like in there. I'm still not fully sure though...

One thing I do know is it definitely won't be making it to the northern tour either, or indeed any upcoming events for that reason! Only got one working motor now, so it's pretty pointless bringing it until I upgrade the drive system with new motors...

[overkill]

That SK3 motor is very similar to the Hacker out-runner I have in Mr Mangle; a higher KV winding and the same dimensions. I am really happy with the motor's performance but your weapon would have 4 or 5 times the energy of my beater and the SK3 motor is going to struggle to spin it up. That 4,150 watts is the maximum power, probably only for 5 to 15 seconds and the continuous power is going to be closer to half that.

[Flag Captured]

Hmm, that's unfortunate
It is looking more like the better option will be to go for a higher speed motor (inrunner, I'd assume) and gear down a lot. The Scorpion does seem a good option but if I can get the same sort of effect with a cheaper motor, it's probably better...

What sort of power would I be looking at for this sort of bar? I am starting to realise that 7000rpm is a pretty hefty target too, may be pushing it a little!

[overkill]

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.

Can you check the units that Solidworks is using for that RMI figure? I scaled the number to Kg/m, plugged it into the calculation for kinetic energy and got 12 million joules of energy! When I used a RMI calculator for a straight bar 400mm long and weighing 3.45Kg, the RMI was 0.156 Kg/m - less than what your design would have, but not too far off.

[overkill]

its just about impossible to calculate the amount of battery capacity required as there are so many variables. Most people look at equivalent designs and use whatever worked for other builders, while others build the bot and test it to find the battery capacity required.

Having a look at other designs, Archangel's bar is heavier and almost 3 times the RPM of Scissorhands, which uses up most of a 4.2AH, 6S pack during a full length match. NST might be another example to extrapolate from. Given the much higher speed and KE of Archangel's bar, my guess is that its going to need somewhere between 2 and 4 times my battery capacity. Its beginning to look like there is a lightweight class weapon being squeezed into a featherweight ...

[maddox10]

Don't worry, Valkiri 2 uses a 4S 8000mAh pack, and is 2 kg underweight.
The 3 kg 395mm disk ain't somthing to sneeze at.

[overkill]

Have you calculated the MOI and measured the RPM of the disk? That battery pack holds 118 watt-hours of energy and could be a great baseline for Matt to work out his battery size.

[maddox10]

I use gut feeling. And it seems to work.

[overkill]

Fair enough - I like doing the maths. Numbers are really cheap and don't catch fire

[Revsmin]

If you take.Archangels base and make it 3mm Ti instead of 3mm stainless you save all the weight you need for a bigger battery.

[overkill]

Wouldn't that make it harder to join the base to the side armour? There's no chance of welding it and screwing it together adds weight and is weaker. How about staying with steel and adding some cut-outs where strength isn't important?

[Flag Captured]

They do if you're me, Nick! That picture of Homer Simpson with the breakfast cereal on fire springs to mind...

Whichever way, it sounds like I'm going to need a pretty beefy battery pack which probably points towards me needing a lower voltage motor so I can get a bigger capacity for the same weight, if that makes sense?
Been having a few chats and the NTMs may be a way forward, specifically the 5050/5060 on 6s... I wouldn't be able to get as high a reduction in to get that 7k I'm wanting, but I've heard good things about the torque on them... at the very least it's worth a shot!

I may look at that too Jarvis, thanks! I was looking at making the bulkheads a little stronger instead and just going for a thin ti base instead, but I'll see how it goes probably. I'll need to do plenty of adjustments to the design but nothing particularly major I reckon, just adjustments on the bulkheads themselves!

[Ellis]

NTMs may be a way forward, specifically the 5050/5060 on 6s...
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I was looking at making the bulkheads a little stronger instead and just going for a thin ti base

These both sound like good things to me! You can always upgrade should a cheap brushless setup not suffice, but I think it will and if it does you've saved about a billion pounds.

[Flag Captured]

Certainly! For one it's a lot cheaper, and that means spares are easier to come across for when the inevitable happens...
Bulkhead wise I'm only using 6082, not Alumec or anything like I initially planned to use for cost purposes so the chunkier the better! Would ideally like 20mm solid ones but that'll be extremely heavy I'd imagine so probably not the best plan, I'm not sure!

Probably need to Cad it up again with the adjustments and see what the weight comes out at, probably.