Questions/builds thread.

Hi again.

It's been a while. My dad has been busy for the past couple of weeks but last night we got a small bit done. We cute the holes for the motors in the inner bulkheads. With some packing pieces, we should be able to get the motors sitting roughly square. Right now they're all over the joint! Also amazed by how heavy this thing suddenly is. It's not even got it's front battering ram, weapon or armour on it yet.

Pics with its drive innards and wheels more or less in place on the photobucket...
http://s1088.photobucket.com/albums/i32 ... elentless/

About time I updated this!

The robot is coming along quite nicely. We have decided on a 4bar lifter afterall, for simplicity, cost and weight allowance. We have also plugged everything in so to speak and got it driving, as you can see here:

http://www.youtube.com/watch?v=5t3f-8X_pPA

This video is at 12v onto a single drill battery. The machine will run on two 18v (we have tested it at 18v, as is to be expected it's an entirely different piece of kit next to 12v) drill batteries in parallel, giving us 2.6Ah. This isn't enough we don't think (opinions? What's your average battery capacity in a FW? This is 4x 12v drills at 18v and a motor or two of some sort for a lifter mech) but we can't find a suitable replacement yet. As I am sure is the case with anyone building a bot, we have to juggle size, weight, cost, capacity, voltage, max. discharge rating and charging. We reckon these cheap 1.2v 1.3Ah NiCd cells are capable of around 10c? Does that sound right? If so that means we have a max. discharge of around 30A, which we feel isn't quite enough. Again, opinions on this?

Also, does anyone have any experience with these cells? - http://www.ebay.co.uk/itm/4-x-C-Recharg ... 2a14e8e3c7

They seem like a brilliant deal. Cheap, very high capacity, etc. We asked someone selling them for a max. discharge rate, and they replied with 3c. Does that mean that if we had 2x 18v battery packs made up of these cells wired in parallel, we would get 19Ah and around a max. discharge rate of 54Ah? Is that correct, and if so, what do you think? Good/bad brilliant/terrible fantastic/useless?

Sorry for all of the questions, feel free to watch the video and leave, lol, although some info on our current drill cells and the linked ebay cells would be brilliant!

Uh-oh, house is busted up, play time over :lol:

I'm impressed :)

Looks a bit like a featherweight Stamper (although that never got finished) but it's certainly agile and pretty nippy, and I imagine it would be more so on 18V. 2.6Ah is a bit lower than I'd normally go (3Ah or over for me) but it might actually be alright, as I'm sure several robots only use around half their capacity in a battle. Also depends how long the battle lasts of course!

If I were you I'd go for a 14.8v or 18.5v lithium polymer- you can get ones with over 20C discharge rating at 3500mah+ that will still save you weight over drill batteries. Here's a pretty good range http://robotbirds.com/catalog/index.php?cPath=63_469

Very impressive, looks like it drives nicely.

I noticed your using what looks like a 1/4 jack for a link, neat idea that I've often considered, just remember it won't be up to much current.

Thanks for the interest fellas! PJ, the reason we went for a jack and not a deans or something similar is for its mountability (is that a word?). It's hard to solidly mount a deans into a chassis, but the jack socket has a screw thread and nut.

However, as you say, we have been having one or two problems with it getting hot. My dad is adamant it shouldn't. It's like a nail going through the middle, much thicker than the thinnest wire we're using for testing (our positive line, the grey one) and that doesn't get even remotely hot. Still, all can be changed and modified, so if needs be we can change it for something with a higher rate of flow.

Right now we're stopping for a refuel (dinner) and then we're off out to the workshop again. We have taken the whole thing apart. The inner bulkheads are now modified so that they can just slide in and out if necessary. All we need to do is do some unscrewing and they're out. We've also mounted some small fans into them, to try and combat the massive heat generated by the cheap drill cells. Also thinking about the lifter geometry as we go. Any pics worth taking will be posted!

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Originally Posted by Relentless

My dad is adamant it shouldn't.

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Well go tell him he's wrong! (Go on, you know you want to :rofl: )

Jack plugs are used on microphone or guitars etc all of which use cables which are designed for low current and high impedence so that's essentially what the jcak plug is designed for. OK they're used for speakers which have a higher current but that problem I assume is why the SpeakON connector was developed.

If you're concerned about mounting a deans connector Robochallenge do a nice mount for them http://www.robochallenge.co.uk/Events_a ... rical.html

Andy

My dad agrees completely having been in the music business for about 106 years (producing music and playing) it's not the ultimate solution but for now it's convenient.

-adamant dad :lol:

I'm pretty sure mountability is a word...... If not I'm going to make it one!

On another note, what does you Dad do?

I'm interested since I'm a composer and producer and we're a rare breed!

PJ, I'm an MTech and used to be a roadie for all sorts of huge bands. Also do studio, radio and video editting and have an entertainment company :D

I guess audio engineering is close enough to normal engineering!

Not openly admitting your wrong is a sign of maturity. Seems your dad is very mature :rofl: .

Anyways, one thing i found if you have an electric plane, it's generally easier to make two bulkheads out of wood which are the same size and the use them as supports either side of your plane which does HDPE and nylon 6 very nicely.

May help if your struggling to get two bulkheads the same hieght.

BTW looks really cool and nicely built. Very interested to see the weapon when it's finished.

Andy

Thanks for the tip. We have been bodging them into the same-ish shape with a mixture of tools. As for the weapon, after showing my dad some Robo Challenge videos on YouTube, he is the one (could it be true!?) that thinks we need a more powerful weapon than a drill-powered lifter. If I am honest, I too am very interested in seeing the weapon we come up with! :)

As for my dad's work, he has been in the music business professionally since he was 18, and for the past 36 years he has played and produced music for various artists. His website is http://www.parrothouse.co.uk if you're interested.

The videos of the FW Champs don't really do it justice. It's not until you're there that you realise just how powerful some of those machines are.

We have a weapon in mind that is simple, relatively cheap, and could be quite entertaining. Not revealing anything yet, though, in case it goes horribly wrong. :wink:

Today we put everything back together into a test-ready base. No switches or LEDs in yet, just the link. We want to test it at 18v before we get into making all of the switches and lights and connections and charge ports and so on. Speaking of 18v, we made our packs up today. They are designed to be separated down the middle, so that when the thing is sealed, the fans we installed will channel air through them, and blow air out of vents in the back. We're not expecting much but it may help with cooling, since as I think I said somewhere, these cells get really hot. Pics are the most recent on the photobucket page... http://s1088.photobucket.com/albums/i32 ... elentless/

Tomorrow, or soon, we will modify the charger and charge the thing up. If all goes to plan we should get an 18v test video, stay tuned!

Bare in mind that fights are only 3mins so you only have to stay cool that long!

Well we have the control panels well on the way to completion. Drive has it's own switch with power LED, weapon switch (not yet connected to a weapon of course) with it's own power LED, fans with their own switch and power LED, charge port with it's own LED that needs some tweaking (we want the LED to be on when charging and off at all other times. We need a diode to do that, which we missed when designing the wiring diagram, so the LED currently is on all the time) and the receiver has it's own switch and LED yet to be setup. This means that when the link is out, nothing can be done but charge the robot, which will be signaled by a red LED. When the link is in and we want nothing but fans on, say after a match, all switches and therefore LEDs are off other than the fan's (yellow LED). Same can apply to the receiver (green), same can apply to the weapon (red), same can apply to the drive (green). Everything can be fully controlled like this from outside of the robot. Should make maintenance less troublesome.

When it's all made and on the robot, we will take pics. All that needs to be done once the control surfaces are in is a modification to the charger, and we should have a fully plug-and-play 18v drive system testbed!

Pics will come in the next few days. :)

A few points to consider for your control panel. The link should only be in when in the arena or testing, you can't have it in whilst sitting in the pits to run the fans, even if you have a switch. Your charging diode/LED may upset your charger as there will be a voltage drop across them. I would avoid using fans, they fail very quickly in robots due to the shock, i would just try heat-sinking, if things are getting that hot after a fight your probably pushing them to hard.

Thanks for the input. We were aware but not openly saying it to ourselves that the business with the link is a possibility. It would be merely a minute or two of running them, if that, just after a fight, to keep things under control. We would use heatsinks, but for the space and weight we have they are not practical. Especially since they may capture heat, but if that heat is not removed or dissipated somehow (i.e., fans) then they're useless. Regarding fans failing, you make a good point. If they shake themselves to bits then oh well, lesson learned. Truth is the likelihood of us being able to enter a robot into a competition (like the UK FW champs, when are they by the way?) is quite small, so they will be fine for just demonstrations and such.

You could participate in one of the 2 German events. Also called MMM's. Those are Full Combat, that means spinners included.

Most Dutch events are also FCC.

Hi, quick question. Does the power for a receiver, be it via a BEC or a separate battery pack, have to pass through the main link? So the main link kills main drive motor batteries, and also the receiver battery all in one go? We're having one or two issues since we are trying to do this. Either we have a fault in our wiring or we suspect the speed controllers are leaking so to speak, lighting LEDS when they shouldn't be lit, etc.

It seems slightly odd to me if the receiver battery must pass through the main link too, considering that if the link is out, the receiver can go wrong and send as many signals as it likes all day long and since the link is out, no speed controllers will be listening, and so nothing can move or do anything potentially dangerous.

Either way, would be nice to know. If it doesn't need to go through the link, it will make our lives rather more simple!

Thanks.

no it doesnt, you just have a switch at the side of your link. Most people use a BEC, therefore the RX power is killed by the link, i prefer using a BEC as its easy to forget to turn the RX off, and when you go to the next fight found your RX battery is dead.

It doesn't? That's brilliant news! OK great, so if we keep it like so, we only need an external switch, which we already have anyway. This makes things much easier! Feels a little like being defeated, since we simply can't work out where our fault is and now we'll just bypass it anyway. Never mind. Also, it hadn't occurred to me, but as you say a BEC would kill all power to the RX when the link is out anyway.

OK, thanks again, I can't believe I almost didn't ask the question! :proud:

We just got an 18v test run...

Mother of God. :shock:

Any vids of it? :)

fast? im guessing, i ran 2 12v argos drills at 18v, was a bit dissapointed with the speed, it seems to be too fast for everyone else

Yes, fast! I don't have any vids yet, we need more space to let it stretch its legs and so as to not put anything at risk (I can't control it in my house well enough). We will probably go to the local sports centre and run it. Big open rubbery floor - should be perfect.

I was very surprised at 12v by it's agility, but as I say 18v its a whole different ball game. I don't know how you could be disappointed in it to be honest! Much faster and it starts getting impractical. We discovered that without components that can take the current draw, it's much slower. Still nippy, but restricted. We have big thick cables, a battery capable of discharging fast enough (we think), a just-about meaty enough link, big high current switches, etc. Then again with everything in but armour and a weapon, it weighs 8kgs. Maybe that's why it's so batty, no real weight to it yet. I have 4 drills, not two. And 100mm wheels...

i think the murphy's law that ran 18v was about 9-10kg 2wd, on a 4000mah nimh pack, didn't really see any change from 12v

Well for us there is certainly a big difference. The video I have uploaded at 12v was pretty much full throttle, I haven't been able to go quite full throttle yet with the 18v in my house due to lack of space, and it's already significantly faster.

My feather runs 4 of those motors on 19.2v now and I saw a big difference compared to other bots running the same setup on 12v. It had a very decent amount of power. Increases the rpm from about 550 to 850 after the gearbox so not sure how you didn't notice an increase in speed Harry :?

When Cicatrix works in the 4WD configuration (which isn't often), for a drill powered bot I thought it had a pretty decent amount of push.

I have just realised how different my plans in the initial few posts in this thread (almost embarrassing, oh well!) are to what we have ended up making. Most simple box possible? Happily we haven't quite lived up to that!

My dad came home today with 2 meters of 2cm x 2cm steel box section for our lifter thingy, and a bunch of M10 nuts and bolts. I will keep info coming when we think of it, we're still very much working out what we want to do. :)

Video footage soon, hopefully.

Finally got a video!

http://www.youtube.com/watch?v=X8l9ejRogTc&feature=channel_video_title

Not a very good example, to be honest. The uneven surface doesn't do the machine justice (in places it has only 5mm of clearance) so we reckon this isn't top speed. Still, pretty good! :D

And some stills of various things added to the photobucket: http://s1088.photobucket.com/albums/i32 ... elentless/

Enjoy! :)

Looks very good. Fast enough to not be dull :)

For your first build I am very impressed actually :)

Couple of things I wanted to ask:
a: How come you used wire rather than battery tabs for your packs
b: Whats with all the switches on the back of the robot

Thanks!

a: Ease, really. It hadn't occurred to us that it may be slightly odd to use wire. We just, had lots, had it there, knew it could take the strain, so... yeah!
b: They are the drive (big switch, green LED), weapon (same but red LED), fans (small switch on the other side, yellow LED) and receiver (same side, small switch, green LED). Then there's the charge socket and heat sensor, and the link.

:)

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a: How come you used wire rather than battery tabs for your packs

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a: Ease, really. It hadn't occurred to us that it may be slightly odd to use wire. We just, had lots, had it there, knew it could take the strain, so... yeah!

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I think a few roboteers have found from experience that bits of wire are actually better than tabs. There's more flex in the wire, which means that a bit of twisting or impacts are less likely to fracture the joint, compared to if a pack was soldered using tabs.
Then there's cost. Okay, so tabs aren't that expensive in the grand scheme of things, but chances are most roboteers will have short (and otherwise useless) scraps of wire kicking about that can be used without having to pay out for some fancy bits of metal.

I'm also very impressed with what you've produced for a first build. Best of luck getting the weapon together for it :)

I too am Impressed with your first robot.

Thanks for the kind words. My dad's work has picked up again so we're able to do less, but tonight we got the back armour panels on. 10mm strips, it's remarkably solid. We got a new toy for cutting the stuff, it works a treat! Tomorrow we will get the top panels on and it will finally start to get sealed up and ready to take some bashing.

We also wedged some wood underneath the motors to support them a little better.

Pics of the armour additions as ever on the photobucket :) http://s1088.photobucket.com/albums/i32 ... elentless/