Torrent's build diary - a dream coming true!

[harry hills]

12 awg silicone wire comes with the Tz85. get it from ebay or component shop or hobbyking. Red plugs are probably deans plugs. Ebay or hobbyking.

[Rapidrory]

My featherweight uses 3 argos drill motors (two for drive, 1 for the weapon) all running off a Zippy 3 cell 2.2Ah 25C battery (http://www.hobbyking.co.uk/hobbyking...arehouse_.html). It gets quite warm after a long fight, but I've only recently blown the 30A fuse in it (upgraded the fuse to 60A as a quick fix for the event, but really need to downgrade it to 40A or similar). You should be fine on a 40A fuse or there abouts if you're only running 2 drills on a 4 cell battery.

I use a random mix of cables, but they're all around 12 awg. A good rule of thumb is to look at what size the cables coming out of the battery are and go for something around that..

I use XT60 connectors (http://www.hobbyking.co.uk/hobbyking...dProduct=46611) for my powerlink/ other connections. As it's the same as what's on your battery, it makes sense to use it for the rest of the robot.

You may have seen this already, but no one seemed to have pointed it out on here; TZ85 ESCs are brushless ESCs, so won't work with drill motors without being reprogrammed first. I believe you can get them pre-reprogrammed on some websites, otherwise you'll need to get someone to reprogram them or do it yourself. Someone with more experience double check this; I've never used them myself, though I have heard/ seen that they are pretty much bullet proof.

What parts have you got so far out of interest?

[MudnuK]

2650mAh 20-30C 4s Li-po battery
Two Botbitz TZ85a ESCs (these hacked ones do work for brushed motors, according to the manual)
Two cheap Argos 12V drill motors
Spektrum DX6i transmitter and AR6210 6-channel receiver
10mm- and 12mm-thick HDPE

Also looking at:

125mm diameter plastic-centred wheels with solid rubber tires (wheels are big because I'm going to go invertible): http://www.bearingboys.co.uk/BZMM125...e_Wheel-8716-p

50W li-po charger (I know I also need a battery bag): http://www.hobbyking.co.uk/hobbyking...arehouse_.html

[Rapidrory]

Ah ok you got some pre-hacked TZ85s; those'll do you nicely

You won't get much grip out of those wheels as is; they have a hardness of 85 Shore A acording to the datasheet (https://www.bilcastors.co.uk/images/...12_114_115.pdf) which is pretty hard as things go (http://www.smooth-on.com/pdf/durometer_with_logo.pdf). You either want something around 30 Shore A, or just get those ones and screw bike tread to them using wood screws, which is what a lot of people do to add grip; my feather has wheels just made of plywood wrapped in bike tread which works fine! It would also add some extra diameter to the wheels which might be useful; make sure you have at least 10mm ground clearance around the wheels, or you will spend all your time stuck in potholes in the arena floor caused by the heavies!

Charger looks fine; I use a cheaper version of that and haven't had any problems with it.

[Flag Captured]

The rule for batteries is that it must be fused for below your maximum discharge of the battery (I think), I'd give this plenty of leeway though, especially if you're going for a Turnigy pack or something. Whilst it is part of the rules, the last thing you'd want is to overdischarge your battery and cause yourself a fire because you don't know what you'll lose in doing so. That said, drill motors don't draw too heavily, I know robots that have used 2 drills on one TZ85 and they've been fine on those.
Drill motors technically draw 85A on stall I think but as long as you don't keep it on stall if you have a broken motor, you'll be fine. Mounted correctly too, the ESCs are pretty resilient to most things. Battery-wise, that sort of capacity sounds fine. Could probably even upgrade that if you really wanted, depending on how much weight you've got left - might be handy if you want to take part in more side events at the FW champs, for instance. Not sure how often/long the feather fights are at the Heavy events because I haven't been to one of those yet...

Have you got a design planned out for your machine, at all? Might be handy to post something, even just a Microsoft Paint diagram of it so people can probably try and advise further!

[Rapidrory]

Argos drill motors have a static winding resistance of around 1 ohm, giving them a stall current of ~12A at 12V; I've been running mine on £6 chinese 20A ESCs for a few events now without much trouble (ok, so I had one FET die, but that's more to do with the fact it had no cooling and was wrapped in heat shrink). It's going from forward to reverse suddenly that causes the high current peaks, but those are very short lived unlike a stall... If they had an 85A stall at 12V they'd be giving out more than 1 KW, which means it could give a Bosch 750 a run for it's money :P
Basically, you're never gonna toast a TZ85 in a fight even if you ran your Lipo straight through it; they say 85A, but the FETS in there are collectively rated to 260A continuous, and they've been shown to handle peak currents around that; You'd blow your battery long before you blew the ESC (Which is potentially worse, but not the point :L)

The fights at the Heavy events are 3 mins long with up to 30 feathers in the arena at once (though it's usually less than half that)

[Flag Captured]

Ahh fair enough, I used the Gimsons GR02 stat sheet to figure that out, though I realise they may be slightly different motors...

Will certainly back up the point though that you're highly unlikely to cook a TZ85 - I was running a stalled speed 900 on one of mine for a good 20 seconds, and that's still in the machine now so you've no worry in that sense. Mount them right and they'll be fine for a long time, just don't velcro them to your baseplate like I did then take a direct hit from a spinner haha

[Rapidrory]

On the subject of spinners; I've so far found it's much more important to design a robot that can survive a fall from 15 feet onto solid ground than can take a spinner hit; there's only the championships and one or two other events which allow active spinners to fight; the majority are all just featherweight melees where the Heavyweight floor flipper is your main enemy :L I've been hurled into the arena ceiling a fair few times by that thing (and also thrown around by Explosion and Flow to name a few) and driven off fine, whereas I'd likely be toast in seconds if I came up against a spinner (my armour is only 5mm HDPE). You should be fine with your 10mm HDPE though, just need to make sure it's all held together fairly well.

By the sounds of it once you've got your wheels you should be well set to build a fairly solid little feather

[MudnuK]

Going for a kind of fw dantomkia mark 1 look, but flatter and wider, with shorter wider prongs and more sloped sides. And without the paint job.

I drew some designs up in plan/side-view and have made a cardboard model (which was unfortunately stepped on, so it's a bit worse for ware at the moment). Unfortunately my camera's out of battery at the moment, so I'll get some photos tomorrow.

I've now ordered some 12awg wire, that li-po charger, a bag, a few pairs of XT60s (all from hobbyking), a couple of those wheels and some 40W blade fuses. Once that lot comes I can get properly to work. I guess in the mean time I could mark out the panels for the body.

I have around half 12mm and half 10mm HDPE. I was going to use the thicker stuff for structure (i.e. baseplate and bulkheads) and the thinner stuff for the outer armour.

[Rapidrory]

All sounds good to me!

How are you mounting your motors out of interest? I found that to be the hardest part with those drill motors...

[MudnuK]

HobbyKing bits came today. Time to get cracking.

I was planning on cutting my motor mounts from HDPE. Although it could be tricky to get a perfectly comfortable fit, it doesn't have to be absolutely perfect. I'm sure I can find a way to fill any gaps. I know RoboChallenge sell mounts but they may not hold the motors to the right height. Also, I can't find their website - did I miss something?

Planning to go to AWS 45 in Coventry as a bystander, so maybe I'll see a few of you there. How much is the entrance f-, ahem, donation?

[maddox10]

Hotglue kinda works on HDPE. Not the most solid connection, but it sticks and can fill gaps.

[Rapidrory]

The voluntary donation for AWS 45 is £1 per robot entered to help cover the costs of the venue... So wouldn't apply for a bystander... I'll be the one trying to orchestrate the 6 robot cluster bot, and will have a sign about N2xV speed controllers in my pit area :L Hope to see you there!

[daveimi]

Hiya. Thought I should jump in here and give you some of my dodgy help. My robots are a load of rubbish and extremely crude. I seek out and try all sorts to find the most extremely simple way of making everything. Below is my current featherweight and a picture of the insides with my dodgy hose clamp mountings. I like to give hope to people lol in that if I can get a robot into the arena then absolutely anyone can! I'm going to AWS on Saturday with another of my plastic fantastic creations so if you would like me to charge my feather up and chuck it in the boot your welcome for a sneaky shot round the carpark etc. I can also explain any of the basics if ya stuck with anything If your on your own I'll be on my own generally making people feel uncomfortable with my needy and slightly demented disposition So feel free to come and say hi n stand awkwardly the same as me not knowing anyone if your stuck for somethin to do lol.

[MudnuK]

Thanks, look forward to it! Would be great to drive a feather around just to get an idea of how it feels, especially in a big open space with nothing to hit! Drove around one of the little public-driven things at RoboChallenge last year and wedged myself in the arena wall thrice... Don't worry, I'll be more careful with this!

Tried to do a bit of soldering. First time with XT60s so I wasn't too sure how to go about it. How do you melt solder inside a connector? So I tried soldering just at the top of the terminal. Went alright but it was a bit loose and I didn't belive that's how you're meant to do it Looked it up online and this guy in a video I found pre-heated the terminal a bit, melted some solder into it and, whilst it was 'still hot' quickly bunged the wire in. Piece of cake.
Well, the solder solidified pretty much instantly. Guess I didn't pre-heat the terminal enough or something. Anyway, I was left with solder blocking up the terminal. My attempts to remove the blockage ended with me heating the terminal enough to melt the plastic around it, causing the terminal itself to slide about half way out of the connector housing. I decided it couldn't be salvaged so I cut the wire I had semi-soldered in.

This is with my ESCs. I know, I lack experience (this isn't my first time soldering, I just haven't done it too many times) and I didn't really know what I was doing so I probably should have started with something less expensive. Anyway, the wires come with pre-soldered tips. Nice and neat. I thought I could do that. This guy in the video had just melted some solder over the wire and it had soaked it up. Easy. I ended up with a sort of wiry club that didn't fit into the connector terminal. So, one hour later, I'm minus a female XT60. I'll try to clean up this mess tomorrow and practice my soldering on random little bits of wire and the ruined XT60 so I can figure out what I'm meant to do.

Sometimes I feel like I'm too inexperienced, but then so is everybody before they get some experience in. I guess the difference between you lot - professional engineers, seasoned robotics enthusiasts, specialist-subject university students - is that I'm only beginning to have these experiences.