"£50" Heavyweight

[Rapidrory]

Ok, so I've done antweights and featherweights before, and I've never yet spent more than £50 on a robot (at least, before it's first fight). Now the question here is, can I do the same for a heavyweight? Having looked through my parts collection, I think I may well be able too..

Wheels:
yDeevL1.jpg
I have a few go kart wheels (given to me years ago by a friend) and a load of wheelchair wheels (from an old school project) lying around; Ideally I'll use two of the small go kart wheels if possible.

Batteries:

GWUOxxP.jpg

Picked up 3 of these UPS SLA battery banks for free that were being thrown out by a local law firm. Each individual battery was originally 12v @ 5Ah, however they're down to about 1.5Ah now.. But since I have 30 of them I can just add a few more if need be! They still give out plenty of current which is the important part

Drive Motors:

6e1m8qr.jpgn94dUnY.jpg

This one's a little more tricky; I've got two pairs of 20 year old wheel chair motors (left) lying around... However they have very little power (less than 200W I think), which is hardly ideal. The other option is a set of lawn mower starter motors (right). Not particularly efficient, but have plenty of torque at quite a low speed, meaning single stage reduction should do (I've got plenty of small cogs and chain around). However, I only have one atm, but I know where I can hopefully pick up a few more for <£10.

Armour and chassis:


Just blown half my budget on two square metres of 10mm Polycarbonate from John, but also have plenty of resin bonded 20mm plywood if need be... Not exactly Hardox, but should keep the dirt out at least :P
I have plenty of good solid steel lying around for the chassis; should be plenty enough for a heavy at least!

ESC:

Another tricky one. All my my robots have used homemade ESCs up to this point, however buying parts for ESCs can get expensive (my featherweight one was ~£20). A (hopefully) cheaper way to do it is to buy a pair of these and basically do a complete rebuild of them so they're usable. More details on that plan can be found here.

Weapon:

PGbFIrK.jpgbsLhGj8.jpg

Haven't got any exact plans yet. Found a couple of 2 foot long hardox spikes on one of the old bits of farm equipment, and either a full hydraulics system, or a 6 foot x 2 inch screw thread that I could make a lifter from... Leaning more towards the screw thread atm as it's less messy..


I've spent £25 on armour so far, about another £16 or so will be spent on ESCs, and the rest'll probably go on another drive motor... I'll be very impressed if I do actually keep it under £50, but definitely don't plan on going over £100 :L

Time to get building!

[Mega Masher]

Good luck with the build

[Rapidrory]

Ok, bit of an update:

I've put off starting the build until next easter/ summer, which gives me plenty of time to source cheap parts. My main sticking point atm is drive motors, with a second lawn mower starter motor not forthcoming (The guy I was gonna get them off didn't have any). I'm going to keep an eye out on eBay for any suitable cheap motors. Hopefully with a year to browse I'll find something half decent; I'm currently leaning towards some wheelchair motors to keep gearing simple.

I'm also looking at scratch building the ESC again, as the cheap ESCs I was looking at before were missing proper gate drivers which makes them unusable for this even with hacks. Having done a bit more research and reverse engineering various ESCs such as the TZ85, I've been working on a design for a dual ESC capable of ~40A continuous @ 40V which is pretty simple and cheap on parts (~£20) and can easily be upgraded to more amps with different/more FETS, though if it's just wheelchair motors, 40A should be fine...

As for weaponry, I'm still going for the forked lifter, however I'm thinking of using a cable/ rope winch with block and tackle pulleys along with tensioning springs to stop it all getting tangled... largely because it's cheap, light, and it'll look cool though the polycarb; I'm aiming for a bit of a steampunk or post apocalyptic look for this one (might get some riveted corrugated iron or something over the polycarb in places for that Fallout 3 look :P )

I've decided to up the budget to £100 just so I can get some parts that'll work for more than one fight. As I say only thing I'm really missing is drive motors, but there's always plenty of small parts which add up quick. My aim is to make something that may be a bit useless, but is fun for the crowds and as solid as a rock

[Rapidrory]

The first prototype for the ESC is working nicely:



(Yes, it's a terrible test rig, but it's what I had around)
This is just a proof of concept i threw together last night to check that all the components I'm planning to use work together as planned, and that the MOSFETs are all switching efficiently. The drill motor is several times smaller than a HW drive, but it can control it without warming up at all which is what I was aiming for. Worked first time as well, which has never happened before when I've developed previous ESCs! :P

The PCB layout for the full version is mostly done; It'll be able to drive two motors at 24V, and have 2x100A surface mount FETs in each 'corner' of each H bridge, though given the pins on the FETs mine would likely have about a 40A continuous rating. (for comparison, a TZ85 use 3 x 191A FETs on each corner, but when mounted, their pins limit them to 28A. 3 x 28A giving ~85A which is where they get their rating from, despite the fact that the FETs themselves could handle up to almost 600A continuous, 800A peak... No wonder no one ever seems to kill them! :L)

The parts for this cost about £15 in total, which is a fair bit cheaper than £50 for a pair of TZ85s

When it's done I'm planning to run it in my featherweight until I get my heavy going; if it gives me any trouble running in my feather than it's gonna be useless in a heavy :L

In other news, I'll hopefully get my £20 postage back for my polycarb, as I collected it in person at Maidstone. This'll free up a nice chunk of my budget again

[harry hills]

I've got a welded steel grab/lifting mech from an old middleweight someone built and I used in the "heavyweight" I half made at some point you can have for free if you can pick it up. Got some nearly new SLA sitting doing nothing much too if you need them.

[Rapidrory]

Ohh, I'd be very intrested; I'll PM you.

[Rapidrory]

The ESC is now mostly complete; needs a few final touches like bigger cables, more caps, heatsink etc, but otherwise is working nicely.

10855149_10152495606661845_8226861271647350884_o.jpg

All the major parts for this project have now been acquired, largely through generous donations from various people (thank you very much to all contributors ). As such, I've so far spent £19, though this'll go up closer to the £50 mark when I've bought all the little things like bearing, high current sockets etc..

Dunno if I'll get a chance to start the build over Christmas; if not, it'll all have to wait till the summer holidays.

[daveimi]

If you get to a point of selling these ESC's for heavies I'll have one of you as well as one of your ant controllers

[Rapidrory]

Got a few hours at home today where I could get the parts for the heavyweight together, and so was able to have a look at the layout:

11059670_10152704329021845_5061949178672831418_n.jpg

This is becoming less of a low budget Heavyweight, and more of a community Heavyweight:

The motors were donated by Dave Lawrie and passed on by Craig Danby
The wheels, which were originally on an old version of the Saint, were also donated by Dave Lawrie and passed on by Dave Weston.
The batteries and lifter grabber weapon (though the weapon is not in the photo and may not actually be used in this robot) were donated by Harry Hills.
And the 2 square meters of Polycarb for the armor came from Jonno for £10.

Thank you so much to everyone who've provided parts I hope you won't be disappointed by the outcome :P

I now have all the major parts needed to put it together, and it's not likely to be much more than a few days work, so I'm hoping to put it together over Easter and have it at Burgess Hill.

It's currently planned to be a larger version of my Fleaweight, Nuts:

1kSjFBN.jpg

It's probably going to share the same name; It was going to be called Big Nuts, but that might be stretching the innuendo too far

Just working out a way of securing the giant nuts in a way that there's no way they can't come off, whilst being flexible enough to flail properly but without getting tangled. Currently thinking a combination of chains and thick steel cable... though I need to source some good chain first.

[Flag Captured]

I'd double check with the EO's to make sure it's all alright (I don't know how heavy those weights will be, nor how fast the machine will spin) just in case it ends up coming under classification as a spinner but other than that, definitely looks good! Looking forward to seeing how this comes together!