3-D print foot-pedal pot-rotation mechanisms?

[Mark Hammer]

With the thread about the build quality and/or reliability of Asian-produced wah shells under discussion, and especially having visited a Mini Maker Faire two weekends back, and visiting the makerspace in our local library this past weekend (equipped with two resin-type 3-D printers and a laser-cutter), it got me to thinking if anyone had experimented with producing either replicas of existing rack-and-pinion pot-rotation systems, or maybe even designing their own (e.g., using other gear-tooth sizes for a smoother feel or to travel a larger proportion of the pot's rotation).  (Actually, now that I think of it, having the laser-cutter available also means I could cut part, OR print them.)

Joe Gagan had posted a clever means to rotate two pots several months back, but what if a person could 3-D print a rack portion with teeth in front AND back, with additional pinions, such that separate pots could be moved differentially?  Alternatively, are there "better" systems out there - other than rack-and-pinion - for rotating pots that we could design and produce ourselves?

Much of the guitar-related discourse I have seen, regarding what both laser-cutters and 3-D printers now make possible in the way of custom/replacement parts, has revolved around things like cutting flatwork for pickups, or printing unique bobbins.  But foot-control over things is certainly a viable avenue for exploring further with these new technologies.

[R.G.]

I eagerly await the day when I can afford a 3-d printer. My long-suffering spouse would no doubt recoil in horror at the idea that I had one of these. 

I wonder what the mechanical strengths are like for printed objects. I guess there have been 3-d printed firearms, so they're reasonably tough, but footpedals take a lot of abuse.

And how about using 3-d printing techniques with electron-force manipulators to move atoms into specific places? Of course, assembling a few thousand transistors (let alone nearly a billion, in modern high-end processors) might be slow, but for small electronic devices, it opens up some interesting possibilities.

[armdnrdy]

It wouldn't be a bad business venture for a company to provide a 3-D printing service for prototypes....along the same lines as PC board houses.

[R.G.]

Good point. That rapidly leads to the concept of the town/neighborhood "blacksmith", with equipment and tools not everyone had to buy who could handle jobs bigger than most people wanted to buy the setup for nor spend the time learning.

[karbomusic]

Whoever gets on first, please make it a priority to immediately print another 3-D printer. 

A buddy of mine has one for his robotics hobby, he loves it.

[Mark Hammer]

Look in the current issue of MAKE magazine for an article on the various Makerspaces and hackspaces around the country.  Many major cities have such shared spaces that one can join for a nominal fee, or maybe even just for some community responsibility and time.  The one we went to is subsidized by the American embassy in town, and situated at the public library.  The laser-cutter is free, but 3-D printed objects are produced on a cost-recovery basis, based on the weight/volume of the object printed.  I would be VERY surprised if there was no such co-op site in the greater Austin area.

RG, you'd be surprised just how small and affordable 3-D printers are getting.  I took a pic at the local Maker Faire of a printer a guy made from some plans he found on line, with a bunch of assorted gears he had printed on display.  The entire printer wasn't much bigger than a Morley/Tel-Ray oil-drum delay.    As for the legendary 3-D printed firearms, they tend not to hold up over more than a handful of firings, if that.

Whether wah gears or roll-yer-own derringers, the tricky part is the durability of the print media.  In some instances, the print head will only let you print with materials that are visually interesting but not especially mechanically sturdy (one printer on display at the maker Faire had an attachment that would let you use a variety of materials for printing, including Nutella).  On the other hand, some folks will use the printed object as a basis for a mold, and cast in sturdier materials.  Objects produced in the resin printer at our library branch is UV-cured (like some dental work) in a light oven, and from the sample projects they had sitting around, seems to be just as robust as any commercial wah-wah rack and pinion I've seen.

Laser cutters are a whole different matter, costing several orders of magnitude more than a 3-D printer, requiring greater attention to safety, big time power requirements, and other stuff like fume extractors.  Use of the cutter at our local library requires taking a mini-course on safe operation and getting certified before you can flick any switch on the thing.  But they're pretty dang impressive.  My son cut me some baffle boards with rectangular ports from 1/4" MDF for a micro-tower I'm making for a bunch of old 2" Apple Macintosh Classic speakers.  I could never have cut anything that neat with any sort of motor operated device.  I imagine the process of fabricating a gear system for a foot treadle by laser-cutting a suitable piece of suitable plastic would be easier and less time-consuming than trying to print out something.  But I'm guessing here.

EDIT:  Here's the homebrew printer I mentioned above.  The Arduino on the left gives you some idea of its actual size.


Here is the "micro-tower" I laser-cut.

[Beo]

Could the laser cutter go through an aluminum hammond enclosure, and would it take a long time? Would be a nice way to get really clean rectangular holes.

[Mark Hammer]

My sons have the training on the cutter, and I'm just a watcher.  Apparently, one of the issues with laser-cutting reflective materials is the manner in which the laser can "bounce".  Stuff like this - http://www.thermark.com/content/view/64/140/ - is supposed to help with cutting metals precisely.  Maybe it's not really necessary, and simply useful for certain kinds of work.  I'm no judge of it, and others here can probably elaborate more knowledgeably than I can about such matters.

[PRR]

> Could the laser cutter go through an aluminum

In general:

• Metals are reflective, so much of the laser bounces off
• Metals have high thermal conductivity, sucks the heat out of the spot
• Metals (often) have high melting points so you need a lot of energy just to soften them

So laser is usually not a first-choice for cutting metals.

Classic machine tools-- milling machines, punches-- are still a fine way to cut rectangular holes in metal. For Hammond boxes, a coping saw, a file, and craftsmanship can work wonders. Don't diss the old ways.

[Mbas974]

..considering also that some models could be a CNC machine for PCB too !!

[Mark Hammer]

+1 to Paul's comments.  And another +1 to Mbas974 as well.

The DIY/Maker "craze" incorporates not only 3-D printing and laser-cutting, but personal CNC machines as well.  Indeed, one of the things I saw displayed at the Maker Faire I went to was a small cnc machine, about the same size as most 3-D printers that was being used to "personalize" hockey pucks with custom engraving (hey, it was a Canadian Maker Faire!).

But I'm straying from the original topic, which was the prospect of fabricating alternate mechanisms for smooth, reliable foot-controlled movement of pots.

[PRR]

> fabricating alternate mechanisms for smooth, reliable foot-controlled movement of pots.

Linear/rotary and rotary/linear conversion is a common problem. Some of the guts of those DIY cutters/printers could be good guts for a foot pedal.

Going WAY back: find a Seagate ST238 hard drive. The head-arm rotates 25 degrees. The stepper motor rotates about 300 degrees. They are tied together with a steel ribbon on two pulleys (one partial). The ratio is not unlike ankle-angle to 270 degree potentiometer. It was exceptionally robust for its purpose. Under klutz-foot you'd want a stronger ribbon, but the idea holds.

[Mark Hammer]

A Royal Fuzz-wah-hurricane pedal I repaired for a buddy, and the earlier-issue Visual Sound Visual Volume pedal I have, both use a cam action to move pots.  In the case of the Royal, it was a rotary pot.  In the case of the VS pedal, it's a dual slider pot.  The world of foot-controlled pot movement is larger than many of us can imagine, and as you suggest, could even be larger than that.

Some folks here may remember any of a variety of footpedals from the 60's that had two directions of motion: toe-heel, and side-to-side.  DeArmond had one, and Fender had one, among others.  One wonders if there are possibilities for improving upon such two-parameter control using self-designed 3-D printed parts.  For example, what if you had toe-heel, side-to-side, and could also slide your foot forwards or backwards, without disturbing the other 2 parameters?

Alternatively, what if there were mechanisms that allowed one to move a foot treadle to exactly where you liked it, and lock it in place?

[JohnForeman]

ok, so now you guys have me thinking.  since i have a 3d printer and so far have only used it in pedal making to make things like spacers and pcb mounting clips, i'm curios as to how else i can use it.  I printed some pot labels a while back but wasn't impressed with how they came out so never pursued any further than testing.
I'm also starting my next build which is a wah pedal based around the guitarpcb mowah.  Someone on here posted a build of a wah using a standard enclosure so i was going to go that route.  I like the idea of a mini-wah and since i dont gig, figured it would work great on my pedal board.
All of that to say, i'm not sure how the normal rack and pinion setup could be improved.  So if anyone can sketch something up, i could flip it to a cad design, print it out and we could test it.  'crowd engineering'.. 
now i'm gonna try to find that double pot thingy that someone mentioned in an earlier post.

[Seljer]

> Could the laser cutter go through an aluminum

So laser is usually not a first-choice for cutting metals.

Classic machine tools-- milling machines, punches-- are still a fine way to cut rectangular holes in metal. For Hammond boxes, a coping saw, a file, and craftsmanship can work wonders. Don't diss the old ways.

Abrasive waterjets on the other hand.....

[ashcat_lt]

I heard on Science Friday a couple weeks ago that places like Home Despot and Kinkos Staples are starting to offer 3D printing services.  I haven't checked availability or pricing, but it could be an option.  There are also a number of online services popping up.  Some will even print in various metals, which I find interesting.

Edit - Yeah, not Kinkos (which would be logical), but Staples of all places.  I'm not finding any info about Home Depot's services, but you can buy the MakerBots off the shelf at some of their stores.  I also found this site which is apparently for people with 3D printers to connect to people looking to print things.

[derevaun]

EDIT:  Here's the homebrew printer I mentioned above.  The Arduino on the left gives you some idea of its actual size.

Some have built that printer (the Smartrap) with a rack and pinion drive. The design is a $400 - $500 DIY project, and it has a growing user base around it, but it's still fairly new and not fully time-tested.

Having taught a couple 3D printing classes, I'd worry about shearing forces on the teeth, especially if printing with PLA (it tends to be brittle). And tight tolerances are tricky, given shrinking and warping as the part cools and sits. My best guess is that the rapid cooling of each layer of melted plastic sets up some internal tension that resolves in corners warping up in the first few hours after the part is printed.

That said, a rack could be printed on its side with extra "shell" layers and be pretty strong. I wouldn't sell a wah with a mechanism that was 3D printed, but DIY parts of that sort are a great use of the technology.

[mac]

3D printers prices are falling every day, and certainly are a good tool for people like us. Some are about USD 1k.
BUt you should consider the cost of printing a lot of copies vs. making just a mould and mass producing with other techniques.

If you just want to experiment save money and get pinions for tapes or cd mechanisims, or find an aero modelism store.
If you want an specific angle and travel distance use arc = r * angle in radians to choose the pinion radius
You can make the rack with epoxi. Apply it over a stick of metal or plastic. Make the rack's teeth by rolling back and forth the pinion over the epoxi.
The flat rack can be pressed again the pinion with a spring. No need to make it curved.

mac

[Frances Rhodes]

hi everyone

i just found this old thread and wondered if anyone had news about printing wah enclosures...
i saw several things lately, and i guess you don't need to print the entire encosure to build a wah, but only the rocker foot-plate to be attached on a metal enclosure and the gear pieces for pots...
i have no clue how to draw anything in 3D on a computer so for the moment i'm pretty useless about all this, but it would be really interesting for some projects to have a wah system that doesn't cost 50 dollars!
cheers

[Mark Hammer]

A bit of a digression, but I saw this unit at the recent NAMM.  Holds much promise for controlling musical devices: http://smashmouseusa.com/

Since this thread originally started, Hall effect sensors have come a long way, and might be more amenable to what you'd like to do than the nuisance of designing a 2-dimensional rack-and-pinion system.

TC Electronics recently included Hall sensing in their effect pedals equipped with a MASH switch.  The stompswitch has a small rare-earth magnet in it, and can be used as a form of expression pedal, even though the downward switch travel is maybe only 3/8".  Now THAT's sensitive.  A 2-dimensional treadle (forward/backward, left-to-right) could be easily produced if the necessary travel can be made minimal.

https://www.youtube.com/watch?v=9Fg7gpD-iU0