Mecanum Wheel Rover 2 (or 1.1)... mmm floating switching regulator looks funny

The parts list

A sample of the little bits and pieces

Assembly Instructions

1. For each wheel, attach the circular servo horn that comes with the servo with the hub using 4 M2x4 self tapping screws.  Take care to hold the servo horn tightly to the hub while screwing.
2. For each wheel, insert 7 bearings into the ‘flanges’ of the wheel.
   • Depending on your printer, this should be a tight fit.  If it doesn’t fit, gently file the inside of the hole or using a M6 drill bit to clear.  I recommend using the file to keep the tight fit.
3. Attach the rollers onto each wheel with a M3 bolt and nut combination.
   • Again depending on your printer, the bolts should fit through (maybe a bit tight).  If they don’t fit use a M3 drill bit to clear the roller holes.
4. Attach each assembled wheel onto the servo.  Remember to install the horn screw!
5. Calibrate the centre position of the servos using the small adjustment pot at the rear of the servo.
   • Send a centre 1.5ms signal to each servo and adjust the pot until the servo doesn’t move.
6. Attach each servo onto a frame using the mounting screws that come with the servo.  Note the orientation of the wheels!  An extract out of MWRover.js shows not only my horrible ASCII art skills but how you should attach the wheels.

MWRover Axes
         F
       _____
   [\]|2   1|[/]
L     |     |      R
   [/]|3___0|[\]

         B

1. Connect each servo to the USB Servo controller as per the numbering above.  e.g. Wheel ’1′ goes to channel 1.
2. Mount the battery holder frame and chumby holder frame to the servo frame using M2x8 self tapping screws.
   • Note : The servo frame has numerous mounting points for you to mount to, and you could mount other components if you wish.  Use a 1.6mm diameter hole, and an optional 4mm diameter x 2mm deep recess for the mating component.
3. Connect the electronics and load the software! [Hope you can figure it out, if not ask away!]
   • Its slightly different depending on the electronics you use.  For the C1 I connected a second USB Connector on the empty footprint, for the Infocast you see above I soldered a Mini-USB cable directly to the breakouts, for the Chumby Hacker Board I suspect you can do the same.  WiFi Dongle pointing up for max range!

Software

Full source code is available for download from :-

http://code.google.com/p/madox/source/browse/#svn%2Ftrunk%2FMWRover

Android accelerometer/magnetometer control might be coming soon…

Edit : Typed this up for someone else so might as well paste it here :-

• Copy the MWRover directory onto the /mnt/storage partition of the Chumby/Infocast.  If copying directly to the SD card, this is probably the largest partition on the card.
• Power on the Chumby/Infocast, and run the shell script install.sh.  You can run the command via serial terminal or SSH.  Power cycle the Chumby/Infocast.
• Once it boots up, it should start up a WiFi access point called MWRover.  Connect to it using your Android Phone or even your PC.
• Once you’re connected, open your browser and point it to http://10.10.10.10:8080/MWRover.html [Sorry about this long address...forgot to make it something sensible... so bookmark it if you need].
• You should get a page where there’s a blue top bar, and a blue bottom bar.
  • Touch and drag anywhere in the middle black area moves the rover.  Let go to stop the movement.
  • Touch and drag in the top blue bar left/right to rotate the rover.
• No software install required on Android/PC/iPhone, its all browser based.

Videos

Test video of the new Rover…first 135 seconds is me figuring out what was wrong…

Video of the first rover…software is the same except a ‘-’ sign moved

]]> http://www.madox.net/blog/2011/01/24/mecanum-wheel-rover-2/feed/ 40 http://www.madox.net/blog/2011/01/19/mecanum-wheel-rover-reprint-with-slight-improvements/ http://www.madox.net/blog/2011/01/19/mecanum-wheel-rover-reprint-with-slight-improvements/#comments Tue, 18 Jan 2011 13:47:44 +0000 Madox http://www.madox.net/blog/?p=795 Reprinting the Mecanum wheels again for someone else but decided to improve the design somewhat.  One of the most common questions by new users of the Up! 3D Printer is how to remove the raft.  The raft is one of the love/hate things of the Up! printer, some people want to get rid of it without understand the importance of it.  Some thoughts and tips on this ahead…

The raft is there for several more reasons than simply acting as support material.  One of those is to cater for imperfect calibration of the nozzle vs platform height, as well as platform level.  Can you figure out how?

Rather than complain about the raft, it is not too hard to design around it.  One of the annoying things about assembling the original mecanum wheels was, you guessed it, removing the raft off the rollers.

The raft/support material is VERY easily removed off curved surfaces.  Large flat areas are also not a problem, but try to avoid sharp 90 degree features on the bottom of your models.  Adding a 0.75mm 45° chamfer was all it took to get the rollers to snap off the raft easily!  The wheel hub also had an recessed bottom (2mm deep x ~10mm radius) which originally served to fit the servo horn, but the raft was painful to remove from here.  Fix?  Remove the recess.

Another tip is to loosen the raft around the edges first, and then peel along the ‘grain’.  Yup, if you look carefully the raft is laid out at diagonal probably 20 degrees to one of the print axis.  Having a dense (4+) raft and peeling with the grain gives you greatest chance of removing the raft in one piece cleanly.

Probably should add a video showing this but experimenting yourself can’t hurt you.  I deliberately added a photo where I was half-way removing the raft/support material on the various pieces.  Oh can anyone guess why I would print that frame in the orientation I did?  Rather than ‘flat’ on the bed and avoiding all that support material?

Raft-o-rama... guess why I printed the frame with supports rather than upside down?

Look how cleanly the raft comes off!!!

"Cleaned" bits and the junk above!

F-up...forgot to change the support settings and printed without supports! Compare this with how nicely it can out with supports! Ooo can you see the funky wheel hiding not very well in the background?

PS : I’ll upload to Thingiverse when I assemble it and make sure it all works nice

PPS : The red mat is from IKEA…not a bad background… the white tray is from IKEA and its around 600mm x 200mm… not bad for using as a tray for cleaning support material.  Both $3 each!

Quad-Hyperboloid - Pink Monofilament <-- That's a mouthful

I ordered the ‘stool’ in 4 materials, corrogated cardboard, 3mm Bamboo, 3mm Black Acrylic and 6mm Clear Acrylic.  The 6mm Clear acrylic is what you see here.  The top of the stool is supported by 4 ‘pillars’ with an additional 4 support beams for the 3mm materials.  The idea is to use monofilament wire to create multiple hyperboloid surfaces from top to bottom to create a ‘cool’ look.  Of course it helps that the monofilament I used is fluorescent and would glow under UV light

Can you count 4 hyperboloid surfaces?

The clear acrylic with pink monofilament example shown is a classic demonstration of the fact I’m slightly hopeless counting.  I had originally planned for 2 criss-crossed hyperboloid surfaces but due to a miscount I realized I screwed up on the first reverse weave.  Deciding to run with the mistake rather than going back to fix it I ended up with 4 hyperboloid surfaces, doesn’t look THAT bad… You can see the concentric ‘rings’ of each hyperboloid surface in the next photo.

Concentric circles look cool

A better selection of how many surfaces and curvature would improve the aesthetics greatly.  Its also rather big, would suit someone with a large bottom I suppose.  Overall not a bad experiment result though.

I’m looking forward to the Bamboo and Black Acrylic versions  Really looking forward to taking a photo under UV light too!

WTF Laptop Stand - Cardboard & Acrylic

¹Welcome to Finland / Waratah Train Fleet / Wednesday Thursday Friday / Worse Than Failure etc – Its not what you think.

Why the?

Lots of WTFs!

Ever since visiting Finland last year, it really nagged me that they didn’t have any souvenir T-shirts that read ‘WTF’ (Welcome to Finland).  Add to that the announcement that the Train project at work I’ve been working on has been named ‘Waratah‘, a fleet of trains called Waratah… Waratah Train Fleet, there really can not be a more suitable name.

How the?

A quick doodle on a notebook, quickie sketch in Inkscape and an upload to Ponoko later comes the WTF Laptop Stand.  The design is simple, two parallel sheets of acrylic or cardboard with joined WTF letters and a cross beam/bar to hold it together.  Snap fit so it can be taken apart quickly and put into a bag.

Cardboard WTF Laptop Stand Frame

What the?

Of course with the ‘quick doodle’ and ‘quickie sketch’ comes a price – I screwed up by not remember to actually measure how wide my laptop actually was! Argh.  Luckily its rather trivial to cut up the cardboard version and shorten the joining piece to come up with something usable.

I also forgot to do some fancy logo engraving/cutting in that cross beam too

Cardboard WTF Laptop Stand Frame (Shortened)

Now now, all better.  Now my laptop will actually sit on the stand properly

WTF Laptop Stand - Cardboard Side View

HP ProBook 5310m sitting on a Cardboard WTF Laptop Stand

WTF Laptop Stand - Cardboard Side View Closeup

The last shot above shows how the ‘W’ actually holds the laptop up in place.  It also shows a minor design flaw where I forgot to add a fillet on the inside of the ‘W’.  A fillet is important on materials such as acrylic to avoid create an unnecessary stress point where the piece might break.  Infact I broke a few trying to snap a piece that wasn’t fully cut through … [Ponoko shipped me extra in the package which made up for it].

Where the?

Where are the design files so you can make your own?  Is anyone actually interested?  Let me know through the comments and I can post the ‘fixed’ [Cross bar length and the fillet on the 'W'] design files on Thingiverse if people ask.

Edit : Added to Thingiverse!  http://www.thingiverse.com/thing:3529

What the? (Again)

Oh just remembered to preempt the ‘what are those holes?’ question, they are an optional feature for threading monofilament (fishing wire) between the pieces to form a weave.  Just thought it might look cool but haven’t gotten around to it.  Recent obsession with monofilament will show in the next post…

Yippee

I was seriously thinking ‘Yippee!’ when I got the first of my Ponoko orders today… then I saw the ‘Yippee’ on the packaging… that was weird!

This is a gallery post of the unwrapping, too tired to assemble the bits tonight.  Can you guess what things I’m making?  [The 'Welcome to Finland' one is rather obvious...]  Post your guess in the comments!

Go on, use your QR Reader on this

Yes, that is “Colour” not “Color” for all your Americans out there!

QR Code is one of the more widespread/popular 2D barcodes out there.  Sure there are others that are used commercially in airline/train ticketing, but none wide as much ‘reader’ support in the form of mobile phones and software.  Almost all phones in Japan are able to read QR Code, add to that Nokias and various WinMo apps.  Not to mention the wonderful ZXing open-source app that’ll work on any mobile that supports Java or Android.

One of the beautiful things about QR Code is that it can tolerate errors in the code.  Depending on the encoding used, up to 30% of data can be lost and the full content can still be retrieved.

I caught onto QR Code a few years back but the ZXing Android app reminded me of this wonderful piece of technology.  A little curious, I thought I’ll add a bit of colour to the otherwise dull and boring black/white QR Code.  Others have noted that if you have enough contrast between foreground and background, most readers will still recognise the code – but lets make every block a different colour!  Yup, it still works!  Its a lot more prettier and fancier, but a thing to note is that you should still use colours that are a high contrast to the background.  I guess I could have used a pale yellow instead of a white background to add more…but that’ll be just over doing it.

Have a play with QR Code.  There are numerous generators online if you do a search, here is the ZXing Generator link.

(Anyone want to write an extension to a generator to make random colour QR codes?)

Model boat fleet fun

Glorious model warships pounding at each another with cannons, and in the midst of all that is my ‘floating camera’ contraption that didn’t work too well but worked…it floated, it took photos…it lived up to its name…madox Floating Camera…

That's no battleship...

Nice sunny day, perfectly still water, a lunch box floats with one thruster on to skew it to the 'right'...

The results weren’t too bad from the onboard video recording, just a few issues with camera alignment and disconnections when using my friend’s laptop (mine ran out of juice).  Here’s a sample clip of the captured footage :-

And one more super nice video courtesy of Andy (aka not me) :-

Read on for more photos and videos

EDIT : PHOTO GALLERY UPDATED, NEW VIDEOS ADDED! CAPS LOCK IS EVIL!

Image Gallery

Video Clips

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Just a short photo/video post of a couple of test runs in the bath tub…

Read on for more videos and photos of this test run…

Pictures :-

Picture time :-

Most of the gear laid out on carpet

Read on for a little bit more…

All crammed into a waterproof case for a test fit

Motor/pump mounts attached by cable ties...

Motor/pump mounts attached by cable ties...

Water Float Test

Water Float Test

Parts List so far

• Asus WL-520GU Wireless Router
• Denkovi USB 8 Channel Relay Board
• AV-Tech AVI202 IP Camera
• Johnson L450 Cartridge Bilge Pump
• 12V 7Ah SLA Battery
• 6V 3.2Ah SLA Battery
• $8AUD Waterproof Case from the discount store

Video time :-

Johnson L450 Bilge Pump Thrust Test

The various rings from Shapeways next to a Ponoko test card

The ‘thin wire one’ (can’t think of a name) has never been printed before.  It was first dreamt up in the shower , I’m surprised how well a scribble on the fogged up glass of the shower turned out printed in stainless steel!

Lets have a better look

Stainless steel and bronze rings

Stainless steel and bronze rings

Hey look, there’s my invoice.  $1.32 USD for the ‘thin wire one’ (have to think of a name…or have to remember what I named it  on Shapeways…) – great price eh?

The print quality is very good though it appears (not sure) that some post processing (polishing?) was done.

Nothing much else to say!  Have to move on to the next post…Ciao!