Sunday, December 21, 2014

Attempt at The Aesthetically Pleasing Quadrotor

I've always loved flying things despite my evident affinity for ground vehicles (they're easier to put a person on). This summer I was given a few small motors so I bit the bullet and bought a complete set of parts. My hesitation up to this point was that homebuilt quads out there are, for the most part, kinda ugly. Yes, hobbyking sells some cool frames, but my real issue is the exposed wires and other electronics...and the overall 'janky' look. Things like landing gear and some of the more intricate wiring organization haven't been totally fleshed out but here's my attempt at a 'pretty' 3D printed quadrotor.

Inside, you can see the motor controllers (red), the flight controller (green), the battery (blue), and the receiver (gray). I don't think I forgot any parts but I'm honestly not sure.

Top is held on by a few screws

The base

Section view. Wiring between motors/controllers will run through the hollow tube arms and up through the holes at the bottom center. 

Printed a draft of the bottom on Rufus. After this I made a few modifications to avoid unnecessary support material.
Updates soon to come!

The guitarist's best friend: Kaye-Po

A friend of mine named Kaye plays guitar. She lost her capo. I made her a Kaye-po. Ha, punny. Don't tell her yet - it's a surprise.

The whole concept is pretty straightforward. It took only two tries to get the locking mechanism to work. The purple stuff is PLA and the orange stuff is O-Ring cord stock to protect the guitar neck and mash down on the strings a bit more gently/consistently. The model in the pictures was intended as a prototype but at 50% fill it is plenty strong. The pieces are held together by 8-32 screws and the holes for the rubber bits are tight enough to hold them in place. The final versions will be 100% fill for safety, will ideally have black rubber bits, and the pieces will be printed in a consistent orientation.

The teeth on the ends lock into each other and can be adjusted for different neck sizes and tightnesses. A friend named Chris also found that this capo has a convenient quick release feature.

Screwdrivers are like guitars.

Text on the side

Thanks to Dan and his guitar for being wonderful models

MacroKart - Transient Version 2

Wow, this hasn't been updated in a while. Since the last post on MacroKart, just about everything that was made of wood is now metal, and the thing went through a brief period of complete functionality before I decided things needed to change... but we'll get to that. This summer I had a friend machine a few parts for me since I was at work during shop hours. These parts included the front wheel uprights, the motor mounts, and the brake mounts. I also borrowed a stem from a friend's bike for the handlebars.

3D printed steering column support

The tube was too small so I had to improvise.
 I also changed the throttle to a twist throttle. The pedal required my foot to be uncomfortably extended at full throttle.
Brakes partially complete

Brake assembly after a bit of use

Here's a short video of the brake supports moving. I don't have a video of one with the complete system, unfortunately.

At this point, the kart was complete. I rode it up and down the street many many times. I did a few time trials and found that I was going about 17 miles/hour. It was fun, but I wanted MORE. So I bypassed the current shunt on the controllers. this involved removing the loop of wire in the picture below and replacing it with a shorter copper wire. The picture below also shows the capacitor that fell out of one of the controllers when I opened it. I guess it wasn't important. I soldered it back in anyway.

This was a huge success. Big boost in acceleration and about a 30mph top speed. As a result, I was blowing 60A fuses like it was my job. At 33V, that's two '350W' controllers burning through 1kW each. Below are two of three that I blew the first week. After that, I was more careful and did fewer 'full-throttle-from-a-stop' runs. I had 5" wheels - the acceleration was something fierce, I'm tellin ya.

Sadly, all good things must end. Not that my controllers were particularly good, but they both died after about three weeks with the current boost.

On to bigger and better things. I pulled out some 8" pneumatics and put them on the front wheels, yielding a pretty goofy looking setup.

Just for fun, I threw a controller on the left motor and did a few runs up and down the street. I ran into my friend Amir, who took a lovely picture and then went on his way.

Summer also participated in the Imagineering 500 and took both first and last place.

Current status: I have two Kelly KBS36101 controllers and sensors mounted on both motor cans. Rear wheels have been replaced with razor scooter wheels that come with brakes! I need to mount the controllers, wire precharge circuitry for the controllers, attach throttle, sensors, power and finish the brake supports/cabling. I'll also probably redo the steering column and have something a little more robust holding the handlebars in place.

Sunday, November 30, 2014

Electric Longboard - GoBoard

Over the thanksgiving weekend I sat down for a few hours and cranked out a rough electric longboard. And then I ordered $100 of parts. So maybe this will happen. We'll see. Everything was designed around a very simple deck and standard trucks and wheels from the interwebs. The only custom bits will be the motor mounts, whatever connects the pulleys to the wheels, and the battery enclosure. I may look around for a simple charge controller so I don't have to take the thing apart every time I want to charge it, but let's leave that for version 2.

From the side - modeled with a flat board.

The board was designed around a motor and batteries I already had. I don't totally remember but a top speed target of 20 seemed pretty reasonable and realistically I'll go about 15 anyway. Safety first?

Closeup of pulleys/tensioner. 7.5" belts is what SW came up with. 5:1 ratio 

Obligatory 'the top comes off' picture. Battery assembly will be 3D printed.
Hooray for efficient-yet-dangerous transportation

Tuesday, October 14, 2014

Electric Surfboard (extreme sports in slow motion)

After my last post, the surfboard got a brief water test in the Charles and there was evidence of a very slow leak in the tail. To remedy this, the board got two more hot coats to (hopefully) seal things off. (Spoiler: it worked)

Fins and fin mounts (compatible with commercially available fins) were hastily 3D printed from ABS. Fins were reinforced with aluminum rods but the fins were actually very strong without them. The weakest point of the fin is by far the point where it is held by the mount. The fin mounts were attached to the board with epoxy/microballoon slurry, where balloons were added until the mixture had the consistency of yogurt.

Fin mount

The aluminum bits are where the screws contact the fin and push inward/up to hold it in place.

The lab's resident Hawaiian and surfing expert noted that these fins are WAY too thick.  Next came the 'waterproof' battery. I built a 22Ah 13.2V pack and submerged it in epoxy. When you do this, you prevent the cells from being able to vent, which is bad. I tried to remedy this by attaching pieces of foam to the pack to allow for some displacement but the foam just soaked up the epoxy and by then it was too late. The pack is completely sealed and will not be happy if it ever needs to vent.

Attempt at foam with kitchen sponges. This did not work.
After the epoxy had set fully, I put on a plastic cover and cut a section out of a smoothie bottle to allow for sealing off the battery while still allowing access to power and balance leads. This was done in a rush. Adrian, don't do this again. Bad. It still worked fine in the water, but we must remember that the Charles is freshwater. No sea legs for this setup.

Sealed up
Another precaution I took was a 'deadman' switch. This is so if I fall off the board, it doesn't keep going. There are controls on the motor itself, but they don't require the user to give continuous input and it will stay on if it isn't turned off. The monstrosity below is a springy 3D printed frame with aluminum contact pads that come together when pressed to complete the circuit. When released, the circuit is opened and the motor will turn off. Umm. The glove makes it waterproof. Yeah.

Next was the motor mount, which involved very very drippy microballoon epoxy and an aluminum plate with holes for 80/20 to be attached. It looks like crap and I know it.

It's a surfboard?
The motor was attached next and damn was it heavy. Not pictured: the battery on the nose of the board for counterweight.

Sometime in October, a few friends and I headed out to test. It wasn't a sunny day but the weather wasn't bad. I had a wetsuit so I stayed pretty warm throughout the trip. Huge thanks to Tommy, Calvin, Dan, Rodrigo, and Andrew for helping out!

Everything was tied down with twine, especially the motor and GoPro.

By the way, the battery is in my backpack along with a whole bunch of foam for buoyancy in case it falls off.

It floats!
It floats... but lower

Here goes...

I went about 1/3 of the way across before turning back.

There is footage of the trip but it's 30 minutes long and I haven't edited it yet. Overall, the trip was a success. The motor didn't push me nearly fast enough to stand up. This was partially due to the motor's power being fairly lacking (it is the smallest of its class) and also because when I was just sitting or laying on the board, I was mostly underwater, providing more resistance and making it more difficult to gain speed. I topped out at about 5 mph, which was still quite a lot of fun. Also I haven't grown any extra limbs since being in the river, so I've got that going for me, which is nice.