Pulverizer Build Diary

[Mega Masher]

Sorry, forgot to add the link. Here it is
http://www.robotmarketplace.com/products/0-TRA2849.html

[Mega Masher]

btw, tom posted this on 360's build diary:
"Youd never get a translational spinner anywhere near as good as one of the others"
I see this as a challenge ........

[Ellis]

There's no need to purchase from the US, postage will be ridiculous, you can get quality lipos from places like optipower.co.uk, and if your pocket isn't quite so deep, some of the packs on hobbyking.com and giantshark.co.uk will do nicely.

Also, battery maths don't work like that. When you wire in series, you double the voltage, but the capacity is that of a single pack. When wiring in parallel, your capacity and discharge figures double, but the voltage stays the same. You can't get 8Ah and the equivalent of 6s from two 4Ah 3s packs, it's a one-or-the-other thing.

[Mega Masher]

Yeah, I don't know much about batteries.
I've heard that hobbyking isn't trustworthy. Is this true?

[Ellis]

Their products are cheaply made. But then, they're also cheap to buy. With most things I am of the philosophy that, for example, if you can buy 5 Hobbyking brushless motors for the price of a single high end mark motor, and their performances are the same, I'd prefer have slightly reduced reliability and 4 spares.

That said, very cheap LiPos could be a safety hazard, so get the best you can afford, and run as far below their rated figures as you can. We're using super cheapy packs originally from HK, that were also second hand (generally considered a nono), and they've been perfectly reliable, very powerful, and completely worth the 12 quid (yes) we paid for them each.

As for Hobbyking themselves being reliable, there are some who claim they're terrible as a company, but I can't really say if that's the case or not. I'll let others who have dealt with them before say more. I ordered a package a while ago from them, but due to a shipping issue (not their fault), it never arrived. I have been in an email conversation with the HK support team for a while now, and whilst it hasn't been resolved (they haven't received confirmation that the package was returned to their warehouse, yet), they have been very friendly and apologetic.

In short, if you're smart with your choice, cheaper products from places like HK will do the job fine.

[Mega Masher]

Hi there, not been up to much lately, but this is it:

Shred:
My melty robot Shred melted itself after getting the accelerometer working well(for vids search for TheRobotPizza in YouTube)
basically, the positive and negative wires going to the arduino melted together and made some sparks and i hope to re-wire the robot with proper wire that won't melt. but on the plus side, by filming the robot spinning in slow-motion with the LED lighting up, it gave an aproximate speed of 750RPM!!!!!!!!!

Pizza Cutter:
Been doing more sketches and designs of it lately, and have come up with various ideas, such as the robot being single-toothed. trying to get funding for it looks to be hard and i won't make the 2014 champs

Cookie Cutter:
The project has stopped for now, as i think it isn't tough enough for proper combat.

Antweight pizza bot thing:
Had ideas of a 80mm diameter melty ant using 31mm green banebots wheels, fingertech pulleys, scorpion HKII-2213-14 motors, a pololu baby orangutan microcontroller, and much carbon fibre and titanuim.

no pics of robots yet but some will follow.....

[Mega Masher]

Pizza Cutter is dead. I've decided to stop it in favour of a simpler, cheaper, and possibly more dangerous idea .
Here's a pic of a design I've made-http://i1280.photobucket.com/albums/a492/Robot_pizza/1387620796086_zpsde80e218.jpg
It will consist of:
24v dewalt motors-http://www.robotmarketplace.com/products/BP389010-00.html
RMP motor mounts-http://www.robotcombat.com/products/0-DWMOUNT.html
a pololu baby orangutan-http://www.robotmarketplace.com/products/0-PL1220.html
this lipo battery-http://www.hobbyking.com/hobbyking/store/__19142__turnigy_nano_tech_3850mah_6s_65_130c_lipo _pack.html
10mm laser cut 6082 aluminium bulkheads-http://www.aluminiumwarehouse.co.uk/cutting_calc.php
6mm polycarb all round-http://www.directplasticsonline.co.uk/PolycarbonateSheet/6mm/
16 mosfets wired to make 2 h-bridges with 8 mosfets in each h-bridge-http://uk.rs-online.com/web/p/mosfet-transistors/5412127/?searchTerm=541-2127&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6 265724D504E266C753D656E266D6D3D6D61746368616C6C267 06D3D5E5C647B337D5B5C732D2F255C2E2C5D5C647B332C347 D2426706F3D313426736E3D592673743D52535F53544F434B5 F4E554D424552267573743D3534312D323132372677633D4E4 F4E4526
Sparkfun ADXL193 +/-250g single axis accelerometer-https://www.sparkfun.com/products/9332
12mm silver steel shafts-http://www.technobotsonline.com/silver-steel-12mm-x-333mm-33173.html
12mm id needle roller bearings-http://uk.rs-online.com/web/p/roller-bearings/0514164/?searchTerm=514-164&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6 265724D504E266C753D656E266D6D3D6D61746368616C6C267 06D3D5E5C647B337D5B5C732D2F255C2E2C5D5C647B332C347 D2426706F3D313426736E3D592673743D52535F53544F434B5 F4E554D424552267573743D3531342D3136342677633D4E4F4 E4526
T5x10 25mm pulleys-http://www.technobotsonline.com/synchroflex-timing-pulley-t5x10mm-14t.html
T5x10 64mm pulleys-http://www.technobotsonline.com/synchroflex-timing-pulley-t5x10mm-36t-33881.html
73x20mm BaneBots green wheels-http://www.technobotsonline.com/banebot-wheel-73x20mm-1-2-hex-shore-30.html
3mm lasercut stainless steel-http://www.merseymetals.co.uk/stainless_sheets.html
And various screws and fixings

Please say if anything on the list seems not good enough or whatever.
Thanks
Mega Masher

[Pinski1]

Don't try and build your own H-Bridge. Buy 2 TZ 85As, mod them, it'll cost you £60. Building your own H-Bridge is extremely hard, like, even electronic engineers won't bother hard.

Are you 100% certain that T5 pulleys will be able to take the power you want to put down?

What do you have planned for the accelerometer?

[Max]

Your links dont seem to work without copying and pasting it into the url bar so its hard to check all your parts. I think you may have unchecked the box " Automatically parse links in text"

It will be very expensive getting all those parts laser cut and I doubt 10mm aluminium will laser cut very well as I imagine it will melt. I would still suggest starting simpler just making a cheap rammer/wedge/lifter as you will learn a lot about being at an event and about what works in a robot, you don't want to spend lots of money to find it doesn't work or gets destroyed in its first fight.

[Mega Masher]

Max, what about 3mm stainless steel. And max, no offence, but I'm not just gonna give up on this idea. Ive seen the rammer bots, bit I want to build something never done before in the uk (I think). I'd much prefer to try hard to build a good bot than get a not-so-good one built in 10 mins. See what I mean??????
Pinski1, research melty b, it shows you what it is used for. The robot reads a value from the accelerometer, and from there works out the speed it is spinning at, then lights up an led to light up the "front" of the robot. Then it can turn on or off a motor dependant on where it is in each rotation to make the whole bot drift in the general direction I tell it to with the controller. Hope that helps. Btw I can't use tz85's as I need to give the motors 70amps continuously and up to 190 for stall current. Tz85's can't do that.

[Pinski1]

Ah, right, I see what you're planning now. Neat. I must admit without wanting to go further into the maths behind "melty brain" robots it seems a gyro would be a better choice. *shrug*

I'd definitely advise against using a DIY speed controller just because it's very hard and expensive to make something that is as reliable as the £30 TZ 85As.

[Ellis]

You can get aluminium watercut quite cheaply.

Unless there's a huge shell to go on this, a 10mm end-tapped (meaning no finger joints or anything) aluminium box structure doesn't sound very sturdy as the exterior of the robot. It would be fine for a regular style machine, but one which is spinning is going to attempt to skew the chassis; squares are inherently weak in the direction of forces this shape would suffer.

Do you intend to attach teeth directly to this chassis or is there a shell to go around that just hasn't been designed?

[Mega Masher]

Pinski1, yes, you could use a gyro, but it would have to be an optical gyro, which is very expensive.
Ellis, I see what you mean, but I'm not sure what I could do to solve the problem of it not being to strong. I could add in bracing or something like that. What shapewould you recommend????

[Ellis]

Well, triangulating the corners with "gussets" would help, as triangles are strong and resist compression a lot better than squares. But then, a circular body is probably the most efficient shape, in terms of strength/weight, as well as it seems logical for a spinning robot (hence others tend to build fullbody machines round or near-round polygons). I don't know the maths, but there's a chance the wind resistance of a square will make for quite significantly reduced electrical efficiency, and a circle, apart from the teeth surface area, doesn't suffer this at all.

I realise it's harder to work with a ring design with the average set of tools, but it might be worth looking into what you have available. If there's a scrapheap near you, a rummage around might bring something up, some steel drainpipe or something could be an ideal starting point. In the past I've had thoughts about using a motorcycle wheel hub as the basis of a full body on the cheap.

[Max]

Ok, just another thing, it looks like you are only getting the dewalt motors without the gearboxes- you need these unless you are going to make a large external gearbox.
You need one of these for each motor:
http://mobile.robotmarketplace.com/0-DEWUT.html