Longboard Footstop in OpenSCAD

My local library, the Hillsboro public library, has 3D printing open labs — every Monday evening for a couple of hours, the library accepts .stl files on thumb drives and prints them for free over the next week. This is such a cool resource, it seems irresponsible not to take advantage of it.

For my first project, I decided to design a longboard footstop.1If imitation is indeed flattery, RipTide and PSD Designs should feel complimented. ;-) Earlier this week, I started researching 3D CAD software and settled on OpenSCAD.2Pronounced open ess cad. OpenSCAD is different from most 3D CAD software in that you program a part instead of manipulating objects on a screen. For example, this is how I defined the tab of the footstop:

union() {
tab_s = tab_length - tab_width/2;
tab_r = tab_width/2 - stop_chamfer;
tab_h = 2*(tab_height - stop_chamfer);
translate([-tab_s/2, 0, 0]) cube([tab_s, 2*tab_r, tab_h], center=true);
translate([-tab_s, 0, 0]) cylinder(r=tab_r, h=tab_h, center=true);

Designing the footstop, some of OpenSCAD’s other limitations became obvious: fillets and chamfers are not easily defined, especially along curved intersections of primitives.3I’m gathering resources that address this issue.

This is my third iteration of the footstop and I think it’s good enough to print next week so Jamison can try it out. I suspect I still have a lot to learn when it comes to getting a design ready to print. For example, how important is it that this footstop be hollow? If it needs to be hollow, what’s a reasonable wall thickness? I experimented with MeshMixer a bit, but expect I’ll need to wait until Monday.

I wonder what I should design next. I think I’d like to try some sort of GoPro mount.

DIY Panniers

I love panniers. I just don’t like spending $100+ for a pair of ’em. When Jamie showed up at Starbucks with a DIY pannier on his bike, I knew I had to do some research. Here’s what I found:

Looks like I’ll be making more than one of these. :-)

HVAC Debug Update: I’m Making Progress

Determined to debug my HVAC problems, I created a list of steps to follow. I planned to verify the presence of power and control signals at the furnace control circuit and the condenser.1Essentially, this is rule #1 of debugging electrical devices: is it plugged in?

Not feeling comfortable about my knowledge of how my HVAC is wired, I searched and found Thermostat Wire Color Codes and a thermostat wiring schematic.2Ya gotta love the Transonics wiki’s disclaimer/warning/license: “The following information may have errors; It is not permissible to be read by anyone who has ever met a lawyer. Use is confined to Engineers with more than 370 course hours of electronic engineering for theoretical studies.” I’m still trying to figure out how this applies to me.

First, I verified the 24V transformer’s primary is getting line voltage.3Yes, this means the breaker was ON and the furnace cover was off. If you’re thinking of using my post as a guide to debugging your HVAC system, you should read the preceding footnote. Then, checking the secondary, I found no voltage. I tried again. I pulled it out of the furnace and tried again. Still no dice. I guess I could have just measured the impedance across the secondary and discovered the transformer was bad4 and needed replaced.

Unfortunately, by the time I discovered this, the local appliance parts and electrical supply stores were closed for the week. Home Depot and Lowe’s were still open but neither has a matching transformer. Looks like it will be next week before our HVAC is working.4It was shorted.

I’m concerned: if I replace the transformer, is something else wrong that will kill the new one? Or did the transformer just die of old age? I guess I’ll find out.

Fortunately, the weather is getting cooler.