HardWired II

[Flag Captured]

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!

[Flag Captured]

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...

[mrsam]

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.

[daveimi]

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.

[Flag Captured]

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!

[overkill]

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.

[Flag Captured]

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!

[maddox10]

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.

[Niels - Team K.a.L.M.]

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

IMG_20140927_175208_zpsd11d90ca.jpg

Thanks to little old valkiri...

[overkill]

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'