Post your DIY exploits


Continuing the discussion from Scientists create blackest black yet:

Here’s your benchmark, folks:

[quote=“shaddack, post:35, topic:36995”]

Hmm, it’s probably more of a suction pump; now I look at it the gauge is in increments of 20mmHg.

Niiiice! Document it when done?  Can’t wait to see how it works inside!

Do the “normal” model servos have enough torque and enough resilience to last in service for significant time?

Actually, it’s sort of two-fold; I’ve (AFAIK) pioneered [this arrangement][1], which pretty much requires electronic shifting to be worth a damn. (Half-step triples aren’t new, but this exact kind is.)

I talk about the electronics and post an early and embarrassing version of my code [here][2].

The servos I’m using are tiny wing servos, with just under 5kg/cm of torque; probably just enough to move the derailers, but the idea is to have a double pulley on the servos with the second one being a cam the cable comes off, onto a spring pulling on it to mostly equalise the derailer’s pull, so the servos only have to fight the friction and resistance of shifting the chain. I’m about 80% confident it’ll work.

Oh yeah? What’s the deal with that?


Scientists create blackest black yet

It’s not a technically challenging project at all, but I’m building a treehouse at the moment:

It’s loosely based on the traditional Low German “Fachhallenhaus” style and will have two carved horse heads at the top of the gable when it’s finished. The drawbridge does lift, but I haven’t made a way to do it as it’s pretty heavy and wouldn’t be safe. The roof opens out on hinges so you can see into the trees when the weather is good:

Apart from some of the matting on the outside and things like screws, nails and hinges, it’s all made of recycled or found materials (the base was a chopping block, the structure is made of pallets, the reed matting and the net on the inside of the roof were left by the last people who lived in the house before us and the floor was someone’s gate that blew down.

The basic structure:


Dude, that’s freakin’ sweet!


Which is about 2.7 kPa. Which means it won’t go down to the plusminus 100 Pa needed when a diffusion pump is used as the next step for better vacuum.

…I wonder if a vacuum tube could be made even with such lousy vacuum, if there was a chemical gettering employed together with an adequately beefed-up built-in ion pump? (Such assembly, with the pump magnet being attached externally and only the electrodes present inside the envelope, could be fairly compact. It would also allow subsequent pumpings to compensate for minor leaks and outgassing.)

Looks worth trying! I am not much into bikes, but I sometimes use their parts; e.g. I used the freewheels as a coupler for several Savonius wind turbines attached to a shared generator, and they worked well to synchronize the rotation speed of the individual turbines. The project was not entirely mine and since then somewhat stalled, but this part worked pretty well. I learned a lot of stick welding on it.

Some electrochemistry I am involved in is quite misbehaving; an acid electrolyte that should have no current up to about 0.7V potential difference is leaking current from 0V up and it bugs me and I cannot find out why. So a curve tracer, or a simplified potentiostat, based on ATmega chip, is being built. First iteration will have just a PWM output as a crude DAC and internal ADCs for sensing, later version will have 12bit ADCs and DACs, multiple channels, and support for a reference electrode.

For other stuff, I e.g. played with cosmic radiation vs altitude measurement, using a commercial flight as an airborne laboratory and a very ad-hoc improvised setup with a DIY Geiger counter and a netbook with audio recording software. (Todo: rebuild the Geiger with a microcontroller and a proper display, and a datalogger. Add a stealth mode with running datalogger but no visible show of activity.)

Or glass earrings, art that stemmed from an experiment with making a solid metal-glass junction for the purpose of vacuum tubes, sometime later.

Or some methods…

or some other stuff,

And some more but that’s about it for now. Plus about a billion of things that do not have the written walkthrough yet, e.g. a little silly set of welded keychain-sized screwdriver bits for repairs on the go. I have to write the doc, I got the stage-by-stage photos but did not get around to write the blurb yet.

By far not an exhaustive list, things tend to add up over the years even when the years are otherwise lazy.


Sweet thing! Bonus points for usage of old pallets (if I recognize some of the substructures properly)! And it is not so non-challenging.


The main structure is just a square-sided box 1 1/2 pallet widths x 1 pallet length (which is about the same length). I tried to take them apart as little as possible for this, as this way I kept the structural strength of the pallets and didn’t waste too much space inside. We’re renting the house and I didn’t want to damage the trees, so the structure is just buttressed against them and has posts in front and behind to provide stability. The roof was quite fun as the mats are held together by wire. If you twist the wire around a half screwed in screw before screwing it all the way in, it tightens the matting against the roof and makes it more secure. I had thought about actually thatching the roof for extra authenticity, but I’d have had to buy the thatch and it wouldn’t have been as secure.

Did you build the wind turbine from scratch or were you modding an existing system? I find bikes a great way to introduce yourself to the basics of mechanics, as they are so simple (compared to almost any other machine) and can be understood in principle from quite a young age. My dad always had a big box of parts in his shed, so I used to spend quite a bit of time repairing and tuning the bikes at home. I’d really like to learn welding, but so far I haven’t had the opportunity. There’s a makerspace in my city though, so maybe I could get an introduction there. It would greatly increase the amount of projects I could consider.


Beware of corrosion issues. If the wire and the screw (or its plating) are different materials, galvanic corrosion can set up at the junction. The wire itself is rather thin and prone to be eaten fast.

A fun thing to do is using different materials for the same purpose, on the same design, and watch how each of them deteriorates over the years.

From scratch. The turbines were made all anew from fiberglass, the frame as well (that was the weak part), my job was the systems for torque transfer from the turbines to the generator and the grid-tie-inverter connection and monitoring.

Get an inexpensive welding inverter. I got one, and while it goes just to 180 amps top, I don’t use bigger electrodes than 3mm anyway, and I don’t think I ever went over 120 amps. Well-worth the cost! I also use rutile electrodes instead of the basic ones, as the few MPa of strength I’d get aren’t so worth the hassle of keeping the electrodes dry. Youtube videos are also a great help.

…and I covet the TIG rigs other people have!


Also, for aluminium, when you don’t have TIG consider brazing. There are brazing rods and fluxes for the common aluminium alloys that work pretty well. I used a kitchen stove with success.

Photos of the process here. It is a piece of square tube, with a small block of bar brazed in in order to provide a bigger mass of material for cutting a tripod (1/4"-20) thread.


@shaddack It’ll take me a while to digest all your awesome before I can respond. Suffice to say for now that I reckon you’d give the Applied Science guy a run for his money, given the means… perhaps you could start with an entertaining Youtube channel (not a dis if you happen to have a few vids in a YT channel).

I was like, five, when I comprehended the salient principles of ye olde bike boom turkey-winged ten-speed :smiley:

I wanna be a framebuilder, bad.

In the meantime, this is what I wanna pull off with anodising and etching (not to mention paint and decals on the carbon fork) on an old favourite… The second pic is photochop on the frame finish and I pasted the carbon fork in, although it’s on the bike since I took the basis of this pic.


Go for it! :smiley:

What about some exotic materials? Lightweight composites (without carbon fibers and other stuff that is prone to brittle failure and delamination under overload), 3d-printed or woven resin-impregnated web structures, self-evolved structures designed by repeated simulation-modification in a way that mimics bone growth under load? What about tubes made from thin layer of metal on the outside and metal foam inside? I got a piece of aluminium foam at some industry fair and it floats in water.

Etching is fun. In this scale you have the advantage of not requiring the precision that’s needed for circuitboards so the process will be more permissive. You may also consider CNC-milling the patterns into the material’s surface. Or sandblasting.


I think I’ll start with brazing lugged steel; it’s still a great way to build a frame and is considered something of a rite of passage in the biz, I gather…

Those are some pretty cool ideas for composites. I like the idea of a bone-like frame… wouldn’t surprise me if someone figures out how to grow one someday.

Freakin’ sweet. WANT

As for the finish on that frame, the idea is to polish it first (maybe even electropolish - ‘bright dip’ - it) to nix the stress risers in addition to going full porn (ie at least as sexy as the Dura-Ace kit it’s wearing), then mask off the AVANTI text on the downtube somehow before getting it anodised in that light grey to dark grey fade, re-anodising it again with no dye to preserve the polish, then have the other writing etched out of the anodising, and doing it a third time in grey dye.

And then I need the clearcoat and decals stripped off the fork, and have it sprayed to match, with the carbon showing through the fade (the dark-dark grey on the frame is to match the carbon), with some decals under the clearcoat, with the AERO text done in a shiny foil.

It seems right on the edge, if not beyond anything I can pay someone to do for me… if I could just throw money at it and be assured of it turning out as hoped, that’d be my preference by a long shot - I realise the quality and precision I’m after here requires a shitload of specialised knowledge and experience I don’t have.

But I’m not sure anyone in my neck of the woods can cover all the bases here… for instance, I can’t track down a laser etching machine big enough to tackle a bike frame, and I have NFI how to translate my pretty pixels into some kind of precision mask that’ll resist sulfuric acid and will have a nice clean edge with no leeching…

The fork isn’t such a hassle; I’m assured by one of the better bike painters in town that he can match a fade nicely, and I suppose the foil decals must be doable… I want the super-thin water-transfer type decal though; that could be a hurdle…


Go for it. Help yourself with a list of brazing alloys, courtesy mostly of guess who. :wink:

For “growing” frames, there is a way for part shape optimization in some finite-element simulation frameworks, but I don’t remember the exact name. :frowning:

As of Al foam, I should get some more pieces, cut them with something suitable (EDM? maybe even a hacksaw or Dremel?), electropolish, anodize, and make into jewels.

For etching of the patterns/signs, consider using photoetch. You can laser-print the patterns, spray-paint the parts with the resist, attach the patterns and expose with an UV lamp (possibly from several angles sequentially, you’ll have to play with it), wash off the uncured resist with a brush or a sponge. That eliminates the need for a big laser-etch machine.

Another possibility is adhesive foil, laser-cut as flat, then glued onto the tubes. Possibilities include spray painting over the foil, then peel it off, and then either use the paint as-is or as a resist/mask for etching/anodizing. Not sure how well it’ll work but half the fun is in trying (and documenting).

Try the materials on small (thumb-sized or a bit more) coupons of metal; then you can test with just small amount of chemicals. (Then once suitable combinations/methods are found, try bigger to see if the method scales properly. Sometimes things heat up a bit too much or otherwise misbehave when they get bigger and one factor scales linearly and another one exponentially.)

But focus on the structural part, primarily. Anodizing and decals are pretty but ultimately not so important in the “bikiness” of the bike; the quality of the tubes and especially the joints is much more crucial.

Also, a thought, re the political message projectors

Few years ago I came up with an idea of what I call a “photon bazooka” - a gobo projector with grossly simplified optics and a high-power metalhalide or high-pressure sodium (both from a growshop, for example) or electric arc lamp. A modified version of the homemade projectors from LCD displays, but with a metal mask instead of the display (think an inch-diameter circle) and a doublet or even just a single lens (a semidisposable unit has to be cheap, does not have to be high-quality). Think a 3-5 feet long piece of a stovepipe with a lens on one end and a lamp on the other one. But the project stalled because of my lack of experiences with optics. :frowning:


Awesome tips, man - cheers :smiley:


That keyring tho. Mega-jealousy.


…For non-QR QR skewers (the red spanner too). A 4mm allen skewer is a lovely way to attach a wheel.

Used quite often, when I put my bike in the car.


You ever thought of building a bamboo one, @Kimmo? My friends and I were toying with the idea, but haven’t the resources or the space. My ghetto bamboo idea was to just cut out the seatpost & bottom bracket, the front [$thing that makes the forks swivel’s real name cos I dunno], and the rear dropouts, then butting bamboo into the stubs of the frame to replace the lost metal. There was a prototype, and it was recognisably a bicycle, but most definitely not a good bicycle.


My allen key lives in me wallet, cos I can’t weld.


The one on the picture is brazed, aka hard-soldered. An alternative to welding, sitting in the middle between welding and (soft) soldering. If you have a torch that can heat the thing red, to where brass melts, you can make it; all you need is a bit of borax, or other suitable flux (I use some tetrafluoroborate stuff but borax works too), torch, and some brass wire; a silver-bearing brazing alloy is what I prefer but a common brass will do too, I repaired a hairdryer heater element with a piece of brass wire from a beading supplies shop (they also have stainless steel wires in small packages, excellent for repair jobs).

Example of brazing a bigger object (big relative to the small torch used), step by step:

And a smaller object:

Edit: For attaching such a holder to a wrench, even soft soldering could do the job. Use a cable lug, crimp it to the wrench, then using an aggressive flux solder it together. The mechanical strength of the lead-tin alloy sucks, but the eye will not be loaded too heavily and the crimped end of the lug will provide a lot of surface area for the joint.


That’d be the head tube.

Bamboo is pretty awesome stuff, and I think there are one or two framebuilders doing some exceptional work with it IIRC, but it doesn’t really grab me… carbon, ally, steel and ti are all better materials to build a bike with. To my mind there’s not a whole lot of scope for improvement on the material front, unless you could somehow combine ti’s durability and toughness with carbon’s incredible strength to weight and anisotropic tunability…

I reckon the action is in the design, which for the most part can be adapted to any preferred material. A lot more room for improvement there. Back in the 80s I wondered why a road bike couldn’t have a compact frame like a BMX (at the time, the only MTBs I’d seen had level, or close to level top tubes)… had to wait something like fifteen years for one to turn up. And that was staring everybody in the face ever since the safety bicycle turned up in the 19th century… shorten four tubes, lengthen one, and make the frame lighter and stiffer, while improving the ride (free lunch!) and lowering the centre of gravity of the bike. Duuuh.

Thirty years later, and the gap between the market and my imagination is closing, but there’s still a gap for the most part… I can conceive of frames of distinction in steel, ally and ti, and I figure given the resources to learn and practise my craft, I could fork out some pretty damn sweet gear… and as for what I can dream up in carbon, look out if I ever graduate to that league…

Sounds like I’m blowing my horn a bit, so here’s an example; a thing you haven’t seen that you will see, and we could’ve been doing it for a while now: where are the LEDs integrated into carbon forks and seatstays?

They’ve got around to integrating speedo and cadence sensors, and even rim brakes since I’ve had this idea, but I’m still waiting for a carbon frame to come along that considers the bike’s whole electrical system as something more integral than afterthought.