Questions/builds thread.

Hi all.

Instead of making 98,056 threads or posts to ask nooby questions, I'll put them all here. I'll use this as a build thread too.

I have no access to a machine shop and very limited money, so I'm using chopping boards as against to plastic bought online, metal of all types from just around the house, etc. I bodge things, sadly robots must be bodged too.

I am quite far down the line of building a featherweight box. I can't use it to compete because I live in Spain, so for now it will literally be a box with 4 drill motors, 100mm blue wheels and the fewest electrical components possible. I'm not going to bother with kill switches or what have you, I don't see the point yet.

I'm also hoping to piece together a drum spinner beetle. I have the ideas and some raw materials. I know what components I am likely to use but, my first question is this...

Is there any particular reason not to use batteries from phones? They're low volts, just 3.6v normally, but I have one sitting in front of me that is tiny and claims to be 930mAh. What's the consensus? Stay away? Good idea? Never used before? I have many more questions but that's the main one for now since they're cheap and readily available, let alone tiny!

Thanks. :)

Ellis

I've just realized how hopeless a question that is. Ignore talk about phones! I'm just starting to get into Li-Po and brushless motor talk and it's all very confusing. I thought Li-Po batteries and chargers would be far more expensive than they are. Again, sorry for making such a confused introduction.

I'm likely to have Li-Po and Brushless motor questions soon. Brace yourselves! I'll try and be as light on you all as possible. :wink:

Hi, quick question... is there much of a difference between inrunner and outrunner brushless motors? I seem to see more outrunners in robots, is that for a reason?

Thanks.

inrunners are similar to regular dc motors in that the inside rotates, outrunners, the outside rotates. The outrunners generally have a lower kV rating so have greater torque and lower final rpm meaning less gearing is required.

Don't look at using batteries from phones etc as these are low discharge devices and so the battery isn't designed to deliver the high currents that a drill motor requires. Chances are you would get nothing more than a very toasty battery potentially leading to a fire.

I would like to add that the kV rating tells you how fast the motor will rotate at a given speed. Multiply the number of volts through the motor by this number and you will get the final number.

Also, if you are using standard speed controllers then these will generally come with failsafes. ALWAYS build a robot with failsafes. A 30lb ramming bot with 4 drills could break your ankle if it got out of control.

I made this thread only a few days ago but since making it I've learned a lot when it comes to brushless motors and Li-Pos. I'm aware that the whole shell of the motor spins on an outrunner as against to a more traditional inrunner style motor. I meant (maybe I should have specified) that if in power to weight, or cost, or if they're different in any sense like that. I see mainly outrunners in robots and wondered if that was for a reason. Thanks for the info, interesting to know inrunners generally have lower kv...

Also aware that phone batteries or anything similar is barmy. I've understood how Li-Pos work now (or enough to know phone batteries are pretty useless!) and having realized that Li-Pos are relatively cheap and that I need a high enough C rating, the right number of cells/volts, etc, I'm comfortable with simply buying some.

On a different note, today I sat down with my dad today and we begun the plans for the featherweight box. We're looking into a four-bar lifter and how something like that could fall into our design.

Thanks for the help, I'll keep this thread updated! :)

Ellis.

Good good, this sport is all about learning

Hi again.

So, I'm tempted to run at 18v instead of 12v. Reason is, I'm likely to use a drill motor for a lifting mech, and I happen to have a 14.4v drill laying around. Installing 14.4v for the lifter motor and using a separate set of batteries for the drive seems over complicated and pointless.

To get more torque and speed out of both the drive motors and the lifter motor, I want to run 18v. I've looked around and I'll probably get an 18v drill battery or two. That's all straight forward.

The problem is, if I choose to run 18v to power the drive, I'm not sure how my ESCs will like it? I've got 2x 12v drills on 30a Electronize each side. Will 2x 12v drills on 18v draw too much for my ESCs? Thanks!

im using the 15a version with 25a fues on 18v and its fine :)

Two drills over-volted to 18v on a 15a?!

15a switch but with 25a fuses. little tip i learned from jamie who built drumroll, he uses the same set up as me but with 19.2v insted on my 17.8v

I think its Carcinus he uses that in rather than Drumroll II, so if your looking for pictures thats where to hunt. I ran 2 drills on 19.2v on 15a electronize and they worked fine too.

I used them in the first Drumroll, and it was an idea I borrowed from Gary. The 25A fuses will blow before the controllers will, but if you were to use 15A fuses, they might be more likely to blow on a semi-regular basis and you'd get fed up of replacing them.

They're in Carcinus now, but without the fuses. One of the controllers needs fixed though, so might need to put them back in.

I see.

So, am I understanding this right?... I can run 2x 12v drill motors, over-volted to 18v, on a single 30a ESC?

If so, happy daaayyzzz! :o

yes but if your planning on using electronizes you'll need 1 on each side

Yep, that's what I have planned. Now to find some 18v batteries and a charger for cheap! Thanks again.

Will 18v NiCd drill batteries (cheapest option I think) be able to supply power to 4 12v drills and possibly another drill for a lifter weapon? If not, will NiMH?

I have looked at the thought of wiring two 8.4v, or maybe 9.6v NiMH packs in series but I don't know how I'd charge them? The problem it would seem for any kind of battery, is that the battery itself isn't very expensive, it's the charger for the battery that leaves a serious dent in the wallet.

Any ideas for getting 18v batteries (in the region of 2-3Ah), and a charger, for around 20-30 quid? Drills still seem to stand out to me but they're often NiCd and I don't know if they can supply enough amps for what I'd be asking for.

Hi.

Looking for a large car fuse (for protecting the whole bot) in the region of 75-100a. Would I be able to use a fuse as a removable link? When removed it completely disconnects power to the robot, and I can protect the thing at the same time. I am referring to something like this... http://www.ebay.co.uk/itm/100-AMP-100A- ... 4150aa2598

Also, anyone know if the name Dust Devil has been used? Sort of a play on Storm II/Tornado since this robot will effectively be a box with a lifter of some sort.

Thanks. :)

its not the best idea since your controller would probably blow at 100a and if it blew before your esc, then the bot will also be dead. just buy a bag of deans connectors and make the up that way :)

Yeah it occurred to me that a global ~100a fuse would be useless, since the chances of every motor in the thing stalling and reaching more than the fuse's rating are pretty low. Also suppose only the motors on the left side stall and due to some act of God reach 40a between them, the main fuse wouldn't blow and the ESC would be at risk.

I think I'll get a 40a fuse for each side, then just as you say, make up a removable link from deans.

If I mounted a decent sized heatsink on each Electronize, would that increase their amp rating?

Thanks.

Hi all! :)

So today we spent a little time making up really crude grub screws for the motors, which are now all done. Next we made brackets up for the front motor mounts. Other than that we brainstormed...

You can JUST picture it now! :D http://yourimg.in/m/9z9vfp5.jpg

If you hadn't gathered from the photo, our plan is for an axe weapon :twisted:. So far we're still at the stage where we're just making a base plate (1cm chopping board, lol!) with the motors and wheels (which I think it's worth mentioning were ordered on the 22nd or so, and have yet to arrive! I'd be lying if I said I'm not a little frustrated. Oh well, so's life...) to make a little run-about testbed. Next stop is battery packs and charger. We plan to make 2x 15 cell (18v) NiCD packs from old drill batteries, and attack an old charger we have. Should be interesting, lol.

As for powering the axe, we're not even sure yet. We know an electric motor > chain and sprockets > should be reliable and proven. But, we've been thinking about elastic and springs... still thinking.

If we were to go for an electric motor system which I think is most likely, we're unsure about motors. I have 2x 200w 24v scooter motors which we WOULD use if they were 18v or less. They're not really good for us because of that. Has anyone ever used a car starter motor for an axe-like weapon? They're readily available, not stupid expensive, 12v, and they move cars. Surely they're ideal?! This brings me on to my next question...

A car starter motor would draw in the order of 100-130a at stall we reckon (about right?) and because of the nature of the weapon, it would more or less always be stalled. That means we need a speed controller that can handle in excess of 100a continuous. Our budget won't do that. How would a 30a Electronize fair with a MOTHER heatsink? Any ideas? If not, I uhm... don't... know! :uhoh:

I think that's about it. Tomorrow we're hoping these :x wheels will arrive. Plus we'll be out buying bolts and whatnot for construction. Tonight we'll order some 50a fuses, some deans and some heatshrink.

Sorry for the long post, we did very little yet somehow all that ^ came out. God help us when stuff actually starts moving. :rofl:

you could use a relay for the axe

If you friction drive the axe then you can avoid stalling the motor.

Not the best solution but not breaking speedo's is worth it.

rick maas does a controller specificlly for an axe weapon you set the amount of time you want the motor on for

You may have problems with a starter motor as they need modifying to make them go in reverse

Thanks for the replies. ^

Today and yesterday we made our battery packs. We took the old 12v drill batteries, and made up two 18v 1.2Ah packs (15 cells each). We wrapped them in plastic bottles, heated the plastic with a hairdryer to shrink it and voila! The cells have been sitting for quite a while, so we're having to cycle the batteries quite hard to bring them back to life. I'm confident that they'll improve, since with each charge>discharge they're taking longer to discharge. I have to say I'm happy with them. They're big, but for a first bot, they will certainly suffice. Also, notice our charger... found in the bins down the road. :proud:

You can see some pics of the process and the result. All build pics will be uploaded to here. :)

hi, you seem to have your photobucket album set on private :?

That's odd. I didn't set anything to make it private. :?

Anyway, thanks for the heads up. Should be public now. :)

much better :)

Nice work with the battery packs :)
Many people consider making your own battery packs to be a daunting challenge (I used to think so too). But it's one of those things where, after you've done it once, it suddenly seems easy and you wonder what you were ever worried about in the first place.

Well the amount of soldering and such involved was daunting, that's for sure. I somehow expected it to take hours. Between me making the short wires up and my dad soldering, we did all of the so called daunting stuff in mere minutes!

Also, for the record, the bottle thing works a treat. I think I saw it on a video for making a cheap battlebot (American video) by RoboGames on YouTube. Standard hairdryer and an old bottle or two and away you go. They're remarkably solid too. Impossible to buckle or twist. Once the stuff shrinks, it's shrunk! Nothing you can do about it. :proud:

I agree, altho using a big model of a soldering iron would help alot, i struggled a bit using my small one when making the FW pack

Still waiting for wheels, but today was pretty productive. We cut out the two side bulkheads and angled the base-plate's edges to fit. The material is astonishing, in a bad way! It's sort of... self healing. We passed the blade through the material 4 times, yet the material remained joined. It was like magic!

Anyway, after much fiddling with the speed and sanding and fretting, we battered something into shape. It's a really bizarre material to work with. We made endless amounts of mess on the drill and scrollsaw. WD40 + what look like toenails, and at other times it was like weird papery snowflakes.

So we cut our 20mm (in theory) 6cm (also in theory) strips, then shaped the back and angled the front. We shaped the base-plate and angled the two ends, then effectively eyed-up our wheel positions. With our lack of knowledge when it came to the material, the material itself being really imprecise (it's 20mm thick in places and I kid you not, 15mm in others), our limited precision tools etc, we got something to within a few mm of precise. Good enough for a first robot. We will definitely use more formal materials when we come to upgrading.

Pics are here: http://s1088.photobucket.com/albums/i32 ... elentless/

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Quick question, what grub screws do we need to lock up the drills? Our homemade ones are functional but big, ugly and... for not much we can do better. Thanks.

yeah most plastics have that healing bit if you try and cut them too fast.

looking very good so far, and STOP DISSING CHOPPING BOARDS :lol:

im with harry on this, look at bitza, used chopping bords and was 10th at the last FW champs, and was build for something stupid like £100 :)

looking good, if you think working with chopping boards is a pain in the asp you've obviously never worked with nylon :mrgreen: robot is coming along really nice though!

Thanks guys. :)

Well today we ended up screwing the bulkheads down at about 85 degrees instead of 90, so we set about rectifying that. We wedged washers under one edge to straighten the pieces, and sort of succeeded. We wanted to make that permanent so we decided to ram glue into the gaps. We ended up using the wrong glue and using some sort of cement like stuff.

*facepalm*

Anyway, if we're not lucky enough for it to work anyway, we'll pull it apart tomorrow and do it properly. :rofl:

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Today we also decided that this material is officially the most awkward material ever. Nothing really sticks to it, it melts really easily, it varies in thickness by 5 mm, it's got holes in it and it's relatively heavy.

So,

Why don't I see robots made out of plywood? It's half the weight, a good deal stronger, cheaper, REALLY EASY TO WORK WITH and readily available. The only logical explanation I can come up with is that it's the psychological side of things. Knowing you're pitching wood against hardox must play on your mind. And not only that, if painted it's really obvious when you've lost a chunk of armour or bulkhead or what have you. Does that mean that even if you're structurally as sound as you were to start with, and fully functional, it looks like your robot is in tatters and therefore you lose points?

We're seriously considering dropping the chopping board and using plywood, I just wondered why no one else does that? Is there any immediately obvious reason?

Thanks.

Yeh Bitza was only £100 to build and came 10th.

The chopping boards were very cheap and seriously tough, but still go destroyed by Little Hitter so don't underestimate the power of other people's bots.
Also although the chopping boards were advertised as 'High Density' Dave (Satanix) advised me that actually they were LDPE.

HDPE has an incredibly high impact resistance, which is what makes it so popular, I'm pretty sure Plywood doesn't compete on any level.

Wanna use Plywood though make a Wooden robot!

Today has kind of reinstated my trust a little. Wood is on hold for a while, haha.

Anyway, we removed the glue/concrete stuff we used by accident because it hadn't set at all. We bought a hot-glue gun yesterday, and so we glued the gaps between the bulkheads and the base-plate. It's pretty rigid now and we're on the kind of angle we want, far closer to 90 than we had hoped in fact. We put the wood screws back in and after just letting the glue sit for a moment it's suddenly massively rigid. No upper support yet, but still, plenty strong. Success, I think. As long as I don't jinx it!

We also put in the motor mounting brackets. We had a bit of a fiddle with it but they're well and truly in now. It's gradually starting to look less like a chopping board and more like a... a, thing.

Not much new to see, but I uploaded a few pics. :)

http://s1088.photobucket.com/albums/i32 ... elentless/

Next stop is the inner bulkheads, then front and back support. Then well put the motors in and wire them up. We're still waiting on the wheels, ordered over 6 weeks ago! :?

Today we made the bulkheads. I wish it were as simple as just making them, lol. I won't go into too much detail but in short, we spent hours doing something so technically simple because of the unique properties of the material, and the end result isn't that great in truth. We managed to use pretty much every tool in our arsenal, and we had to break our scrollsaw blade to remove it from the material, which had melted and dried solidly around it. It was interesting, to say the least.

Anyway, yeah, the two inner bulkheads are cut. Need to be refined a little since one is significantly shorter than the other, then mount them. Photos below!

http://s1088.photobucket.com/albums/i32 ... elentless/

:)