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!

The design originally was intended as a pendant for my niece that’s customized with her name and printed using wax and cast into sterling silver… it was originally 3 tone too…

...and pink...

However the design has to be simplified in order to be printed ‘hassle free’ using the Up! printer that’s based on a FDM process.  Complex overhangs either end up sagging or require support structures that are impossible to clean in such an enclosed space.  Inside the wall edges have a 45° chamfer applied to minimize the need for a support structure.  This is intentionally done on the ‘side’ as printing and applying the chamfers in the ‘tall’ orientation affects the air chamber flow too much it almost makes no sound.

Don’t know where the chain holder ended up in the simplification…you can always add it back yourself.

Printed using Up! printer, fine settings, 0.2mm layer,  solid fill, raft settings – dense=4, angle<40, area<10mm.

Works straight out from the printer even without removing it from the platform!  Blew into it and it sounded

Whistle - Works straight out from the printer! This is the orientation you need to print in.

Oh did I mention I’ve been a good boy and uploaded the files to Thingiverse already?  Here you go :-

http://www.thingiverse.com/thing:5312

The ‘quick and nasty’ software files are still the same as in the previous post.  Pure software test only, couldn’t resist the temptation to try it via WiFi on a stock Chumby instead of USB tethering.  As such the hardware frame is a bit too flimsy and the batteries aren’t enough to power the Chumby without brown-out resets.  These will be improved upon soon

This demonstrates the ‘touch’ (initialize) and ‘swipe’ (move/offset) control on touch screens.  Will try the DeviceMotion Javascript API on iOS 4.2 devices (iPhone 4G/iPad) if I can get my hands on that filth…

Video!

Previous Posts :-

• http://www.madox.net/blog/2010/12/19/mecanum-wheel-base/
• http://www.madox.net/blog/2010/12/24/mecanum-wheel-base-software-test/

The concept

There is no concept… I just wanted a wheel base that is cool and can be controlled by a *cough* iPhone [Android phone...] via Wifi.

The parts list

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.
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.
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.
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.

How it shouldn’t look like after fitting the processor board…

Obligatory super short demo video

Product Endorsements

• Designed using Alibre CAD Software – Made drawing and modifying the wheel very easy.
• Printed using Up! 3D Printer – The print quality is superb
• Parts purchased primarily from LowPriceRC – $3.40 for continuous rotation servos? Meh
• Robot Simple – Pololu reseller with free worldwide shipping!  (Wins a lot of points for me in Australia…)

I’m not receiving any kickbacks from any of these companies but definitely wouldn’t mind some <wink wink nudge nudge>

Where’s the Software?  / Where is the Chumby(Infocast)?

Patience… I’m still waiting for my Infocast to rip up…

Need to borrow an iOS 4.2 device to test too…

Propeller Hats!

A picture post showing the latest delivery from Shapeways.  Joris just posted guidelines on stainless steel printing so I thought I’ll post some photos to show what tiny detail can be achieved.

Fits quite nicely on the shirt cuff...

Back side of the cuff

Blurry cam of a shirt that obviously needs ironing

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!

The heart shape rings came out in perfect crisp detail!

Photos after the break…

One quick photo to summarise the result :

Iris blades painted with Rub 'n Buff without the buffing...

The finish is pretty good for a 20 second rub on.  I only used tissues to apply the rub n buff because i couldn’t get my hands on any decent cloth and I didn’t want my fingertips all silver again.  With some experimentation I noticed that it is much easier to apply the paint along the ‘grain’.  Keep it mind that using this paint could get a bit messy so remember to work ontop of some tissue/newspaper!  (I used tissue ontop of this very laptop I’m typing on now).

Give it a try!

Here are some photos with some explanations/captions :-

The Heart Shape Ring

What is it meant to look like?  See here : http://www.madox.net/blog/2008/12/03/cute-colourful-heart-rings/

What its meant to be like...

Lumpy rings...

More rings together...Notice the inconsistencies in heart shapes and that there is excess material within some of the heart cutouts

A close up of the 'silver' one where I used some 'Rub & Buff' silver leaf paint applied using my fingertips. A lot of hand-washing afterward. Notice the ring just on the right and the 'blob' of excess material on the right side of it.

Showing the deformation on the other side of that blob.

Rings in a line. Notice the two right most rings I

The Mechanical Iris Diaphragm Mk 2

What is it meant to be like?  See part section view here :- http://www.madox.net/blog/2008/12/04/rapid-prototyping-mechanical-iris-diaphragm-new-improved/

The reverse side of the iris. Notice there is absolutely no gap/separation/distinction between the two inner/outer rings, it just looks like a frisbee....

A little chip on a support rib...no matter...

Top side of the iris. You can see a 'hint' of the blades in the centre but they're all fused together.

Another bottom side, you can see part of the blades through those holes on the bottom.

Top side at an angle...Nothing new

The miniature trebuchet…

I had a model ready to print, infact I was going to order it before I received these but thought I’ll wait to check the clearances work.  Lucky I didn’t order it yet… I hope Shapeways figures out what’s wrong with the latest batch of prints.