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Thread: HardWired II

  1. #401
    Yeah, it worked well in Inertia XL but obviously didn't see the long term effects that had on the HDPE itself! That, and with how much power is in this bar, last thing I'd want is it to warp itself after a couple of hits. Problem with it too is that it'd have to be structural as well by design and I'm not sure how the lot would last!

    I see, I think I get what you mean! It's a bit of a debate really, though if it's strong enough I won't really need to take it apart, I guess?

    I'm starting to side away from aluminium for this one to be honest, looking at the steel bulkheads as more of an option now, after looking at how Catastrope and Demon do it, it's actually starting to sway me a lot more towards that kind of design. Nice as aluminium would be, I'm worried it'll be a little too heavy, or not strong enough by the time I've machined them down as much as I'd need...

  2. #402
    Precision engineering hour!

    Quick design question for anyone who has experience with beefy vertical spinners, when I'm looking at wheel placement, where about should they go? As a VERY rough sketch of the planned layout (minus batteries and escs) this is the sort of thing I'm going for, bar's 400mm high, body of the machine, probably about 150mm high all the way round. That's what the wheels will roughly be anyway, so that's something to base it on...



    Red = mild steel (3mm wall)
    Red arrows = weld points
    Blue = brushless motor (weapon, probably some NTM 5060)
    Orange = drive motors/gearbox
    Purple = Wheels
    Black = Hardox, 3.2mm
    Silver = bar, definitely not proper dimensions


    Right, so here's the rest of the 20 questions haha

    Should the wheels poke out of the back? I'd like to say yes for mobility reasons, but at the same time it concerns me a little that it'd ruin the structural integrity of the machine.

    Would 3.2mm hardox be alright for the job? Demon runs a similar setup to this, but I believe that uses thicker steel... I'd hate to think it's too thin on that front and I'm going to end up twisting the entire chassis after one hit, if not - would 5mm be more suitable, or a higher grade even?

    I've got a few welds on the robot, would it be better to weld that back plate on all 4 points, or bolt on for the support bulkhead type things running through the middle? I'd worry about over-welding it, but I don't know if the support is needed... I do have a fixed shaft for the bar though, so that might help too...

    Finally, stability - would this sort of design be too top heavy to accommodate a 400mm bar? The bulkheads would reach probably something like 200-240mm tall, and let's say 430mm tall with the bar upright - whilst this sort of design would mean it's a lot wider so better for stability when turning, I don't know if it'll end up being too top heavy and knocking itself over too much...

  3. #403
    The wheel placement looks fine to me; its always a bit of a compromise in vertical spinners. Placing them at the back often causes steering problems as they have less weight over them. Placing them right at the front is better for steering but means they are taking more vertical recoil when you hit something. IMHO, about the best place is just behind the centre of gravity, with a skid surface at the front to take all the impact forces. Having the wheels poke out the back makes them targets for other spinners, I'm not sure its worth it...

    How come the wheels are so large? 150mm diameter wheels don't get you any advantage in a bot like this and just put more strain on the gearboxes. Most vertical disk bots I can think of use relatively small wheels to save weight.

    Stability is always the weak point of vertical disk & bar spinners; its just something you have to live with. The main problem is gyro forces when the bot turns and the larger the weapon diameter, the worse it gets. You can counteract that with a wider frame but eventually you run into the weight limit. Magnetic hold-down is another option but its all or nothing; if the gyro forces overcome the magnets, the bot will flip really fast.

    Its just a guess, but this design might have an extra instability problem. When bots gyro, they are usually balancing on one wheel and either a front or back corner. With your tapered front on the frame and the wheels fairly near the rear of the bot, the front corner is well behind the axis of the weapon and that might cause the bot to topple onto it's front in extreme cases. Its *just* a guess, might not happen.

    Demon uses freakishly strong military grade steel and its definitely more than 3.2mm, more like 4 to 5mm. As a weight compromise, think about making internal parts in thinner steel and keeping thicker steel on the outside walls. You can also preserve the strength of thinner panels with gusset plates like I use in Mr Mangle.

  4. #404
    Some notes on Binky that might help...

    -She only has 73mm wheels and she is still quick enough to land heavy hits when she needs to.

    -The wheels are just behind the weapon axle. Means the steering is easy and predictable.

    -The chassis flexes by the 4mm ground clearance letting the machine bottom out in a hit. Once that happens all force is transferred to the opponent.

    Also...

    -Your design lends itself to an exo-skeleton design with thicker armour to make its structure stiff. try using thinner walls with aluminium blocks bolted to them to support your weapon shaft.

    -Inertia XL had its wheels so far back that it would pitch up almost onto its side in a hard turn, waggling its other wheel in the air. Try and keep the distance as short as you reasonably can to prevent the robot lifting itself to far up.

  5. #405
    Thanks Nick!

    Yeah, it does appear to be a compromise - the reason I debated the wheels out the back was purely in case I got stuck upside down and for reversing off wedges. I might not end up needing it, but it's more just covering my bases than anything! Will certainly have outside bearing blocks for the wheels though and lots of shock mounting to try and minimise the impact on the motors. I've learned my lessons from this year!

    I was looking at magnets too, but I'd rather use them to compliment an already stable-ish design than rely on them entirely - though if the drive will take it I'll definitely use it to my advantage... Might use something like 1kg either side next to each wheel just to help keep it down, but I'll see how it gets on I guess. Reason I debated larger wheels was purely to allow for better grip at speed, and also so I could get something with a bit more of a foam style tread so I could keep plenty of the tread on the floor when it's gyro-dancing, if that makes sense? I'm probably describing it badly!

    Ahh, I see what you mean - would that be remedied perhaps by adding a small thin wedge or spikes on the front? I can probably amend that in the design, I got the design idea from Electric Boogaloo and a little bit of Inertia XL too (as well as Demon for the setup) and they don't seem to have many problems, though I don't think they're quite as top heavy as this!

    I worried about that too, it looks ridiculously tough - I put two and two together and assumed it was thick mild steel, not sure how high grade Hardox would stack up to it (looking for some 650+ instead of the 450 that's usually used) but thicker stuff on the outside may work a lot better. That was really the reason for welding it to those two internal beams, just to keep the lot a lot more rigid, but I don't know whether that'll be enough... I'm trying to make the baseplate non-structural too where possible, though it definitely will bolt to the lot so it'll provide a little bit of support!

    Edit: Thanks too Alex, completely didn't see your post there! Shows how long I take to reply D:

    Binky does seem very nippy when you want it to be! I have noticed it seems to lose a bit of that speed though when the disc's at full, though that may just be my eyes...

    Aluminium blocks too, how would you suggest working those? Little bit confused (it's late, my head stops working past midday!)
    There will be HDPE bolted to the outside probably too, I thought I should mention - it won't be structural nor will it help out in anything but armour, but it's worth noting I guess.
    Last edited by Flag Captured; 20th August 2014 at 21:06.

  6. #406
    Yeah wheel placement is tricky. Not only do you have to consider weight distribution but how the robot will react when it starts tilting over. Something like the drawing might pitch forwards and fall on its nose cause its quite short in length, but couldn't really say. They drive great (until the blade is going too fast to turn ) with the wheels just behind the axle but obviously no invertibility then. On the other hand having the wheels jut out the back compromises the frame strength quite a bit. Damned compromises

    Having some blocks or something the robot can squat down on is pretty much essential, though most already have something like that in the form of a wedge etc.

    Demon is 6mm too and yes its super high brinell steel. You have to take care welding the high hardness steels as they will crack easily due to the high carbon content. Gotta use stainless filler and Tig it else it will absolutely hydrogen crack everywhere. That and you aren't supposed to tack weld it either due to the rapid heating and cooling. Makes things tricky!

  7. #407
    I'm not sure foam wheels would work on a bot that gyros; as the bot tips to one side, that wheel will take all the bot's weight on it's outside edge. A foam wheel would probably distort and crush, letting the frame bottom out earlier. Perhaps this explains what I' thinking:



    You would probably be better off using a harder wheel with a wide tread like the fat Colsons that Mouldy has just put on 720. They have a large contact and won't distort. The other point here is that keeping the wheels as close to to the side walls as possible lets you keep some control as the bot tilts and also helps driving off wedges.

    This video of Inertia XL perfectly demonstrates several of these problems:



    Because the wheels are at the back and far behind the centre of gravity, they don't have much weight over them and that reduces their traction so Inertia can't drive the wedge under Tilley very well. When Inertial turns fast, the wheels lift off the floor very early. That's because the bot is pivoting over a line between the front corner of the wedge and the front corner of the frame, like this:



    Right at the end of the match, Inertia props itself on the arena and the wheel placement doesn't help it drive off the wall - it looks like the lower wheel is off the floor due to the tapered front end.

  8. #408
    Now I've got a couple of minutes spare I can offer what I have learnt after running Inertia XL for a few years

    The 2013 version that keeps being mentioned was by far the worst of the ones that I have built. I tried to make it too powerful for its own good and as a result found loads of issues with it. The first one being that to fit the Sidewinder in to drive it (was the only speedo we had at the time that could handle 8s) I had the move the entire disc mechanism forward by around 30mm which meant that the wheels were too far back. That, coupled by the switch to the A123 batteries meant that there was no weight over the wheels. The original one had 1.5kgs of Mi-Mhs at the rear to keep it level. This is why the old one had the big boxy back end. Also the change in design did allow it to drive upside down should the disc stop working.



    In the video that Nick linked to above there was only one wheel working fully as one was completely loose. When this was fixed the drive was significantly better which can be shown in the two fights with Tormenta 2 from later on in that event.

    Also the HDPE bulkheads worked very well and I still have both sets intact and could be used again. The black ones fom the 2013 spec had bearings fitted and worked perfectly even with the 10mm HDPE base as it meant that there was enough flex to absorb big impacts without permantly distorting.

    That being said for the latest version I am switching to the 15mm Aluminium bulkheads and moving to a different design with 4WD. The front wheels are in line with the disc to hopefully give good control. Now that I have a reliable source of income it may make an appearance in some whitboards next year as I've got the inclination to finish it at last.

    Hopefully this makes some sort of sense as I didn't really plan what I was going to write first

  9. #409
    Quote Originally Posted by teamshock View Post
    the drive was significantly better which can be shown in the two fights with Tormenta 2 from later on in that event
    Yes, much to my dismay! Secret plan all along methinks.

    (you can continue with the topic now)

  10. #410
    Thanks for all the input as always!

    That worries me a little then if Demon's 6mm haha - I'm not sure how the stuff you use stacks up to Hardox, Glen, but I'm not sure I'd like to try 3.2mm knowing that! Maybe 5mm Hardox could work, maybe... My main worry is that I'm aiming for essentially a 4kg bar, at 7000rpm+ with probably quite sizeable bite - that'll put A LOT of force on the whole machine, and whilst I'm going for a static shaft, I definitely don't want the whole thing twisting after one hit! That said, I don't want to make the whole thing so shock absorbant that I end up losing a lot of the power out of the bar - I'm not entirely sure that's how it works but I'm sure I'd lose some of that energy, right?

    I haven't entirely written out anything though, I did think about 20mm HDPE for bulkheads at one point and they are still on the cards if they'd work better! It all depends really. I'm starting nothing on the build until I've got the plans sorted!

    Hmm, I see where you're coming from there Nick, my way of looking at it was softer foam wheels - more wheel on the ground when it gyros, but I can see that being a much better benefit! I'm hoping to stick a bearing in that outer side, so might end up with 10mm between the wheel an the outer edge, might be alright...

    Thanks too Will, Inertia was one of the ones I was looking at for design ideas! The weight distribution is definitely something I'm aware of now - I learned the hard way with HardWired 2 I think haha! I'm trying to build Arch so that everything is pretty much in line with the drive so there's plenty of weight around it (will probably help control the gyro-ing too) but the bar placement is something that's being quite changeable and I'm really trying to get right - at the minute I think it might actually be a little too close into the rest of the machine...

    Again, the size and weight of the bar is something that concerns me - I know it's utter overkill, but I'd rather aim high with it all, create something that'll cause carnage haha.

    Something I will ask though - is there a calculation that can be use to determine say, what thickness of material you'd need to use for a set of bulkheads, or is it more just trying it out and seeing how it gets on?

    Thanks again for all the help too (and apologies if any of this is horribly worded, I'm very tired haha)

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