Tuesday, November 26, 2013

QUADframe Battery Tray

battery tray on QUADframe Pro Six

One of the goals of our hexacopter is long flight times.  Our hex is large and relatively heavy (3.3 kg without batteries) so that requires large batteries.  We planned to fly with either three 6S 8,000 mAh batteries or two 6S 10,000 mAh batteries.  These batteries are large and heavy.  QUADframe sells a battery tray that mounts between the arms.  Unfortunately those mounts are designed for much smaller batteries.  Time to design a new battery mount.

QUADframe battery tray

After some playing around with the frame and batteries, I determined the best place to mount them was over the center plates of the frame.  I removed the protective dome and decided to mount the plate on the four standoffs that supported the dome.  I wanted to make the tray out of honeycomb carbon fiber.  Unfortunately I didn't have any left and I didn't want to wait to order it.  So I made my own carbon fiber laminate.  I epoxied some thin carbon fiber sheet I had to both sides of some good quality 1/8" plywood.  I clamped it in a vise between some boards as it dried.  The next day I cut it to size on a wet tile saw with a diamond blade.  Sorry, I forgot to take pictures as I made the laminate.

over-sized plate attached

Next I marked and drilled the holes to mount the tray.  The GPS mount that I made was in the way of the tray.  So I cut a groove in the tray for the GPS support.  Had I known the batteries were going there, I would have mounted the GPS somewhere else.  With that done I mounted the tray and tested the fit of the batteries.  The tray was longer than needed, so I cut it to the same width as the center plates of the frame.

screwed to standoff

To hold the batteries in place I used some heavy duty Velcro tape and Velcro straps.  I cut a slot in the tray to pass the straps through.  The standoffs were higher than needed so I cut about 1/2" off of each to bring the center of gravity down.

finished tray on frame

The tray is very strong; doesn't even budge with over 6 kg of batteries on it.  As a bonus, it also protects the flight control systems from crashes.  The 10,000 mAh batteries mount front to back, while the longer 8,000 mAh batteries mount lengthwise.

10,000 mAh batteries

8,000 mAh batteries
Even with all of that weight on top, the hex flies pretty well.  The 8,000 mAh setup balances slightly better because the third battery mounts below the hex on the landing gear (see first photo).  At some point in the future I may move the GPS mount so I can move the 10,000 mAh batteries closer to the center of the hex.  But for now, it works.

QUADframe Boscam Mount

hexacopter camera mount

The hexacopter I am building will feature a Boscam FPV camera and pan/tilt mechanism.  The camera unit needed a solid yet lightweight mount for stability.  There was no room on the frame plates so I decided to mount the camera between two of the arms.  The carbon fiber tubes will provide a solid mounting platform and will also offer some protection for the camera system.

honeycomb carbon fiber

I needed a mounting plate to reach across two arms of the hexacopter.  It will be mounted to a boom block on each arm.  We had ordered some carbon fiber honeycomb sheet to play around with.  It is light and very stiff, perfect for the camera mount.  I made some rough measurements and got to work.

cut carbon fiber plate
If you do a web search on how to cut carbon fiber it is easy to get overwhelmed.  It is either as easy as cutting plywood or harder than herding cats and bad for your health to boot!  Turns out, it is super easy to get clean cuts in carbon fiber.  I had a cheap wet tile saw that I picked up for another project with a diamond blade.  I taped the cut line on the carbon fiber and cut it wet.  The tape prevents the carbon fibers from fraying.  The water keeps the cut cool so the resin doesn't melt and suppresses any dust that is bad to breathe and can short electronics.

I cut the plate to size on the tile saw.  The plates came out looking like factory cuts.  I laid out the boom blocks and mounting plate and carefully measured for the mounting holes.  I drilled the holes according to the blueprint below.  I finished the mount by rounding the sharp corners.


finished mounting plate

One of the biggest complaints about the Boscam camera are the mounts.  Using anything other than the factory pan/tilt mount can be problematic.  Since I opted for the factory unit, mounting was easy.  I just used the pan/tilt as a template, centered it on the mount, and marked the holes.

Boscam pan/tilt mechanism

attached to frame

The final mount weighs just 28 grams, not including camera and pan/tilt mechanism.  It is rock solid, no flex or vibration.  The edges of the honeycomb plate look a little shaggy.  I need to dress them with some tape or glue to give it a more finished look.  Other than that, it almost looks like a factory piece.

Monday, November 25, 2013

Aluminum Pen

my aluminum Bic pen

I've got a thing for metal pens.  I've been planning on making my own but I haven't settled on a design yet.  So I have been collecting any decent metal pens that I can find.  Kickstarter is chock full of nice pen projects.  I've backed a few and been generally pleased.  One that I missed was the Baux Pen.  So simple, it's elegant.  It's nothing more than an aluminum tube machined to fit Bic pen parts.  Very cool idea.

the Baux Pen, my inspiration

Not too long ago, I posted about some landing gear I assembled for my hexacopter.  Turns out those landing legs weren't so great so I took them off and swapped them for a different design.  As I did that, I noticed the aluminum tubes on the bottom of the landing legs looked to be just the right diameter for a pen.  I checked with a Bic pen I had on hand and the outside diameters were almost identical.

drilling inside diameter

First I cut the tube to rough length.  Then I chucked the tube in my lathe and opened the inside diameter of the tip end with a letter G drill bit to a depth of 1/2".  Then I turned the tube around and parted off the other end to the correct length.  Drilled that end with a letter E drill bit.  The end plug is a bit more narrow than the tip.

parting off

Only thing left was to add a few grooves for a better grip and some visual appeal.  I used a 60 degree insert and spaced the end rings 0.020" apart and 0.010" deep.  At the tip I made the grooves 0.030" apart and 0.010" deep.  I was going to polish the tube but I really like the shine of the grooves against the bead blasted finish of the tube.


The Baux Pen must use tubing with a larger diameter than a Bic pen to achieve the step-down look at either end.  It gives the pen a much more interesting look than the straight sides of my pen.  But I used what I had on hand at the time.  Overall not bad for about 20 minutes work.  The metal body feels better than plastic and balances better when writing.  I may have to do this again in stainless steel.

QUADframe Sonar Mount

I am running the APM 2.6 autopilot on my hexacopter.  That system uses a sonar sensor to accurately measure altitude when flying close to the ground.  Mounting the sensor is somewhat critical.  It must have a clear view of the ground, be mounted away from any electrical wires which may cause interference, be clear of any mechanical interference from the props, and be isolated from vibration.

MaxBotix MB1240 Ultrasonic Rangefinder

The QUADframe that I am using does not come with a mount specifically for this sensor so I had to make my own.  I decided to mount the sensor on one of the landing legs.  I started by cutting a piece of aluminum angle to length.  I drilled two mounting holes in the mount and legs.  Then I scribed the contour of the leg into the aluminum.  I shaped the end of the mount on my belt sander to match the curve of the landing leg.

finished mount

sensor in mount

Next, I drilled the holes for the sensor.  I attached the sensor to the mount with nylon screws and standoffs to prevent shorts.  After that I added the wiring.  MaxBotix recommends making a power filter to eliminate electrical noise.  You simply add a 10 ohm resistor and 100 micro farad capacitor to the power supply lines.

power filter circuit

sensor wired up

I attached the senor to the APM according the the diagram below.

I added a piece of Kyosho Zeal between the mount and the landing leg to cut down on the vibration transferred to the sensor.  As a final measure, I wrapped the entire sensor in foam to cut down on acoustic interference.  The sensor appears to work pretty well.  It gives accurate readings when the hexacopter is static.  During flight the readings seem to get a bit erratic.  I may just need to adjust the sonar gain in the Mission Planner software.

ready to fly

Friday, November 22, 2013

Hideaway Book

You'll never find my stash!

I've always wanted a hideaway book.  I don't know why, it's probably not the best hiding place.  But it seemed like a fun project and a good use for an unwanted book.

I searched my bookcase and found an old dictionary.  The internet has pretty much made printed dictionaries obsolete, so why not do something useful with it.  I started by sealing all of the edges together with Mod Podge.  I weighed it down while it dried.

sealed the edges

Laid out the cut.
Then I started cutting.  At first, I used a hobby knife.  The cuts were nice and clean but it was taking forever.  So finally I got lazy and broke out my Fein Multimaster.  I used an E-Cut saw blade to slice through the pages.  The cuts weren't that clean (dull blade didn't help) but it was fast.

Started out nice and clean...

...finished ugly.  Hopefully, no one will ever see the inside ;-)

Once I had the book hollowed out, I vacuumed out the debris and sealed the edges with more Mod Podge. To hold the book closed, I used a pair of neodymium magnets.  I drilled a hole and epoxied one magnet in the hole and the other magnet to the cover.  The magnets are strong enough to hold lots of weight.

magnet set in pages

Back in the bookcase it goes.  Now if only I owned anything of value to put in it...

My secret is safe.

Laser Cut Company Emblem

Laser cut acrylic emblem

I am starting to make a few things to sell.  I want to brand the items with my company logo (They are mosquito claws, fyi).  Originally I wanted to have some hard enamel badges made.  The price per badge isn't too bad (about $2.50), but most places require minimum orders of 100 pieces; too much money.  I thought about just painting the logo on; but I decided a plastic 3D emblem would look much better.  The idea was to make a nice badge, much like what you would find on old radios.

company logo

I decided to use the laser cutting services from Ponoko.  The process is fairly simple.  Draw up your design in Inkscape.  Cut and paste the design into one of the Ponoko templates.  Adjust your line colors and weights to fit the Ponoko guidelines.  Then upload your design, choose the material, and order your parts. They have a large selection of materials to choose from.  I chose a bright red 0.118" thick acrylic sheet.

Ponoko template in Inkscape

Turnaround time was a bit slow.  It was 15 days before Ponoko even made my order.  It was a bit nerve wracking waiting as I had no idea how everything would turn out.  All that worry was for nothing as Ponoko delivered exactly what I expected.  To attach the emblems, I used heavy duty double sided tape for smooth surfaces or glue for rough surfaces or fabric.

Cut panel as delivered

I am very happy with the results.  The emblems look great on vintage electronics; exactly how I pictured it. The prices aren't too bad.  These cost me $35.46 including shipping.  I fit 49 pieces on one 7" x 7" sheet, so the cost per part was only $0.72.  Now that the design is on file, I can order more at any time in a multitude of colors.  It adds nothing to the function of my projects, but it does give things the professionally produced look I was going for.  I have plans to place another order for a slightly different design.  I'll post about them when they are made.

rebranded radio