RepRap Mendel
Scott Tse and I have been slowly building a RepRap Mendel, which is a DIY open-source 3D printer. It extrudes melted plastic to ‘print’ objects. We started nearly a year ago, and progress has been very slow. We’ve certainly learned a lot about surface mount soldering with a hotplate, and how to order millions of tiny electronic parts online.
The photo above is what it SHOULD look like when done. So far we’ve built all the electronics, but have been having issues with the extruder controller board. Once we get that figured out, we can start the physical build.
Heavy Lift Quad Copter
I started yet another audacious project this summer, a heavy-lift quad copter, which, when finished, will carry a video camera into the sky and capture amazing footage for my projects. I started with a ‘recipe’ gleaned from hours of reading aplanding.com and rcgroups.com. Thanks to AJ, DJ, MorenoNYC, Mark Dana, Tkeeg and countless others.
Here is a list of what went into this so far:
1x MK FlightCtrl ME
1x MK Pressure Sensor (mpx4115)
1x MKUSB
1x DCDC regulator (for servos)
4x 1hoch4 BL V1.0 30A max (16 kHz)
Radio: JRX9503 TX
4x APC SF et SFP 14×4.7 props (I think I got smaller props later)
4x 12″ Align 450 tail booms
Rusty’s Frame
iCharge 206b w/ cables and PSU
2x 2S5000mah 7.4v Thunderpower Lipos
4x AXI2820 motors
Currently I’m able to fly for about 10 minutes on a charge, which is quite a bit less than I imagined. Some of this is certainly due to the foam landing gear that I cobbled together, which blocks a lot of wind. I was hoping to get 20 minutes without a camera onboard. I haven’t started on the camera mount yet, but hope to soon.
Shoulder Mount v1.1
Today I finished some upgrades to my first attempt at a shoulder mount. This new version includes separate rail-mounted hand-grips (thanks to some mt biker who left his bar-ends in my basement). The grips can be adjusted on the rails, or turned on the rod they are attached to. They are extremely light weight.
The mount sits on the shoulder, and is adjustable for length, but not height. It attaches to the rail mount under the camera with a simple wing nut, and can be removed easily, though as you can see in the photos, you can leave it on while it’s on the tripod, and it works fine. Nearly all parts of this mount are recycled. The large square pieces of aluminum are cut-offs from my stalled steadicam project. The tubes are from an old tripod. The shoulder ‘pad’ is a piece of the old foot rest in my Eskimo Salto kayak may she R.I.P.
Steadicam Prototype v3 Test
I think I’m making some progress! Here is some video I shot of the steadicam prototype arm curling some weights. There are still some obvious problems, but at least it’s encouraging.
3A style topstage
Starting to think about the other parts of the steadicam, working on a 3A style top stage, here’s what I have so far. I worked off some photos I found online, so the dimensions are a total guess. I found a rack and pinion gearset on mcmaster carr, the rest should be pretty straighforward. Going to glue the rack in the top plate, and add some screws to add friction to the sliding parts, as well as some hard stops to make sure the camera doesn’t fall off.
Changes changes
Did some thinking, and I’ve made several changes to the cam/ride mechanism which should help with the issues I’ve been having.
1) made the bottom of the lift assembly thicker so it will have less chance to twist on it’s bearings. I may at some point change this further to grip the post tighter- right now it’s just a set screw, but it might need to be a clamp instead.
2) the ride mechanism gets new larger bearings and shafts- going from 1/4″ to 3/8″ should help with the twisting.
3) I moved the lift adjust screw to the side so the pivot for the ride mech. can be closer to the post, meaning a shorter moment on the twisting action
4) see #2- did the same thing on the bone side of the ride mechanism.
5) changed the cam, now it’s a single piece with a 3/8″ post sticking out.
Hopefully these changes will help.
Design + Development = wow, I respect engineers even more now.
I added a second cam and connecting rod to my arm yesterday. It definitely solved the twisting problem. In the long run, I’d rather just have a single cam, because adding the mechanism to adjust the offset from the cam will be twice as difficult with 2 cams. For now, twin cams, fixed connecting rod length.
The most obvious problem right now is that as the cam switches from pushing UPwards on the connecting rod, to pushing DOWNwards on the connecting rod, the whole assembly clicks and jumps a bit.
I’m also getting way too much friction in all the little rods and bearing surfaces, part from the design, and part from my lack of holding tight tolerances in the machining process. This friction is so great that the arm is sluggish, and I doubt would do much stabilizing in use.
Prototypes are frustrating
I finally completed a prototype of my Steadicam G-series style arm. Yippie!
The bad news is that there are some pretty severe design flaws in my plans. Not sure how the G-series arms cope with this issue- that the cam at the top is pushing only on one side of the top of the spring attachment mechanism… makes the whole thing torqued sideways, as you can see in the top view. Going to try to add a matching cam and rod to the other side to compensate. I’m starting to see how things get over-engineered.
Shock mount for boom pole
So I finally made the first usefull thing with my new machining skills and tools. My good friend Aaron sent me a boom pole that he got free for some reason, and finally got around to making an adjustable adaptor to mount my DIY shock-mount on the pole. The shock mount is 4″ ABS pipe, cut off in the middle, and some elastic shock cord from an old pair of pants.
The top of the boom pole has a 5/8″ threaded rod poking out of it, so I machined up some 1/2″ aluminum, added a thingy to adjust the angle of the shock mount, and voilla! I actually made something usefull! Probably not going to get it anodized, since it’s not exactly fine craftsmanship. It works though.
DIY HMI pt 3
After even more research, I’ve decided to retrofit one of my Lowel Omni fixtures with a 70W HQI bulb.
~$86 for the bulb – Iwasaki EYE Color Arc MTD70/D #56227 which is4000 lumens, 6000hrs, 6500K 92CRI. the bulb is 120mm wide, so it’ll have to go at a 45 degree angle in the square fixture. The specs say it has an up to 15min restrike time, but I’m betting it’ll be more like 5mins, like the other Iwasaki HQI bulb that I have in my soft box. Here are the specs for the bulb- http://www.eyelighting.com/tb/MH/ColorArc/EQS-N-52-78-56227.pdf
~$98.43 for the ballast- 120v-277v input – electronic ballast for 70W bulb
~$5 for a lamp holder for this bulb
I ordered 1 bulb, 1 balast, and one lamp holder from Steve from Dyna-Brite Lighting in Tuscon (Phone: 1-520-882-4404). I’ll have to do a bit of metal work to get everything inside the fixture, and then will need to make some special cables to connect the light to the ballast, and ballast to the wall.
If it works, then I’ll have an openface/spot/flood adjustable Lowell Omni that puts out ~ 300W worth of light (in Tungsten terms) and pulls 70W from the wall. Not to shabby for a hair/rim light.