Note: I wrote this post a few years back, but I forgot to hit the publish button, I guess.
For a lot of reasons, I've been wishing my trigonometry skills were up to par recently. My lack of knowledge has specifically held me back from solving a few design problems, and there is also the possibility that I can offer my Digital Electronics students a math credit if I could pass the test formerly known as the Praxis, and get my high school math certification. For those of you who don't know, I currently teach high school Computer Aided Drafting, Project Lead the Way engineering classes, and a wood shop class. This year my conference period landed on an hour in which trig was taught, so I asked the teacher if she would mind if I sat in, and now here I am taking high school trigonometry in sixth period.
I wanted to document some of my thoughts here, because it's a weird feeling taking a high school class as an adult, and I'm getting some insights into the life of a high schooler that I'm not getting by merely teaching classes.
It's hard.
OMG it's hard. Maybe my classmates have it easier because they all just came out of Algebra 2, but I'm struggling with just the basic algebra side of things, much less the trigonometry. We're learning the Pythagorean Identities and if we go slowly I can keep up, but I have to keep referencing knowledge that I just learned yesterday, and it becomes confusing quickly. It takes too long to understand everything back to the root knowledge, so I have to just memorize waypoints, but when I use memorized knowledge I forget what it all means. My brain is not used to working this hard.
I'm doing about an hour of homework a day, too. Plus, I'm giving up my conference period, which means I have about an hour of teacher stuff to do at the end of each day, so this class is costing me two hours a day total. None of that is a really big deal at this point in the year, but it may be trouble later. My primary thought on this though is that these students are probably working this hard in most of their classes. Could it be possible that they have 3 hours of homework a night? I'll have to ask a few of them. As an electives teacher I never give homework so students can concentrate on their non-electives class homework, and this experience is reinforcing that decision.
Where are the girls?
My trigonometry class has a perfect 50-50 split of boys and girls, and of the 7 boys in the class, 6 of them are in my CAD 2 or Digital Electronics classes. Exactly zero of the girls are in any of my classes. What's going on here? Most of my students don't take trig, so I'm always excited to get the students who do, and it seems like the easiest way to get more trig students would be to get the girls too. There seems to be a relationship between advanced math boys and mechanical/electronic engineering. Why does this relationship not exist for the girls? What electives are the girls taking? I need to find out.
Do I need to raise my hand to go pee?
The other day I needed to use the bathroom during class, but I didn't know what the protocol for asking permission was. I just held it.
The National Interscholastic Cycling Association, or NICA, is exploding in popularity, and I've seen a lot of parents buying their kids their first mountain bike lately. In almost every case I've seen those parents make the same mistake of not buying a bike that's going meet the needs of their young rider, even in the short term, and I wanted to lay out some guidance as a second-season NICA dad, a former bike shop mechanic, and as a newer mountain biker myself. Before we get started on what you should be thinking about when picking out your first mountain bike, I want to lay out some basic truths:
1) Any bike is better than no bike, and I've seen some student athletes do very well in races on low-end bikes. You can always buy a better bike later. Your bicycle is not a tattoo; bikes are temporary. I'm not here to shame anybody into buying more bike than they can afford, but I do think that too many parents are not buying what they should be buying out of fear that their kids won't be into it long term, or that the more expensive bikes and features aren't worth it, or that they won't be appreciated by a new rider. The very opposite is true in each of those cases, to a point. A new rider will absolutely and instantly feel the difference between those bikes, and that difference will manifest itself as a desire to ride their bike more. It's no fun to ride a no-fun bike.
2) I think there is a perception that the difference between a $600 entry level bike and a $1500 bike is the difference between a Honda and a Ferrari, but in reality it's the difference between a 1984 Chrysler K-Car and a modern Honda Civic. That K-Car will get you to work, and they sold millions of them, but you're not going to drive them for fun, and they're not going to inspire a love of driving. They're not safe or reliable, and they were designed when the national speed limit was 55 mph.
3) The kind of riding that NICA is geared towards is most likely not the kind of riding your kid wants to do. Cross country NICA riding is a wheels-on-the-ground affair, and any opportunities to catch air on the NICA race courses are typically roped off. Let me tell you right now, your kid wants to jump. Luckily for your your kid, amazing flow trails with beautifully sculpted jumps are being built across the country at record pace. Unluckily for you though, the entry-level bikes that are made for those trails are somewhat more expensive than the entry-level cross country bikes. Since all good bikes are expensive anyway, and since you're probably not going to buy a different bike for each of those disciplines, and since there's no cash prizes for winning a NICA race, and since your kid probably isn't going to win even with an expensive cross country bike anyway, I'm going to recommend that you buy a bike that's capable of doing what your kid wants most. You'll get more use out of it, and it will inspire a love of riding that will last forever.
With that being said, here's my list of must-have features on an entry-level mountain bike:
A dropper post. Don't buy a bike without a dropper post. The only situation I can think of in which you might not want to buy a dropper post is if your kid is coming in first place in track and cross country running events, and you think your kid might only be interested in pure speed. Otherwise, that dropper post is going to make all other kinds of riding more fun, and by a significant amount. A dropper post is like an office chair, which will lower when you're sitting and pull the handle, and raise when you pull the handle and take your weight off of it. This allows you to have your seat all the way up for uphills and fast flat riding, and instantly lower it for jumps and technical descents. Do not buy a low-end bike without a dropper post thinking you will add one later, even if the bike has internal cable routing for a dropper post already. You won't, and if your bike came with a front derailleur then it's shifter is going to be in the way of the dropper lever, and the expense of converting a low-end bike to a 1x system so you can add a dropper post isn't usually worth it.
A 1x drivetrain. All the cool kids are riding 1x these days, and for a good reason. 1x drivetrains (pronounced "one-by") don't have a front shifter or derailleur, but instead have 9, 10, 11, or even 12 gears in the back and a single (1x) chainring in the front. They typically shift better, are lighter, allow you to put a dropper post lever where the front shifter would have been, but most importantly they're just easier and more fun to ride. Thinking about when you should use your front shifter and when you should use your rear is just gone.
A clutched rear derailleur. Because of the increase in popularity of 1x drive trains, rear derailleurs must move from tiny rear gears to absolutely dinner-plate sized gears in the rear, so they have a lot of travel. What the gear train manufacturers have done is to make that rear derailleur so that it doesn't flop around when you hit a bump. You might remember that on your old bike you could take the jockey wheels of the derailleur and pull them up and forward, which makes the chain all floppy on the underside. For reasons I don't fully understand, clutched derailleurs don't do that very easily and it keeps that long travel derailleur and chain from smacking against the bottom of your bike frame on jumps and bumps. You won't realize how bad you need a clutched rear derailleur until you've ridden one. I'm pretty sure almost all 1x drivetrains come with clutched rear derailleurs, but check to make sure.
A quality air fork, with adjustable rebound dampening. Do not buy a bike with a spring fork and no rebound dampening. They are jarring, klunky, and loud. Your hands will go numb, they're heavy, and you will not have as much control over your bike in bumpy terrain. You will not be happy after the first month of riding.
Hydraulic disk brakes. Even the worst hydraulic disk brakes of today are so much better than the rim brakes of old, and the cable actuated disk brakes of not-that-long-ago. I'm not sure if you can even buy a new mountain bike without hydraulic disk brakes these days.
Those are my must-haves, even for a brand new mountain biker, and looking over Trek's website their cheapest new bike that meets those requirements is a Trek Roscoe 7, at $1,260. I see so many parents buying their new mountain bikers a Trek Marlin 5 at $550, and that's a mistake. The derailleurs are Shimano Tourney, and that's literally department store bike level stuff. The fork is not made for off road use, but called by its manufacturer (Suntour) a "metropolitan" fork. I made the same choice that so many other people make. That was the first bike I bought my son, and a few years later that was the first bike I bought myself. It was an OK choice for my son because he was still small and was not just his first mountain bike, but his first real bike at all. It would not be appropriate for a high school student. I was instantly disappointed in mine, and within a year I had spent significantly more on my next bike (a Remedy 8 at $4,000). My son now rides a Trek Roscoe 8 at $1,790, which he absolutely loves (and spends about 6 hours a day on), but is not a particularly fast cross country bike for NICA races. I know a lot of people who use their Trek Stache as a playful all-purpose fun bike, and also race them. In fairness, I should say that I saw a student athlete place in the top 5 of the 9th grade race in Bentonville, AR on a Marlin 5, and he looked like he was having a great time, but I'll bet he upgrades soon.
I want to also list a few other considerations that I don't consider must-haves exactly, but I want you to be prepared to know about them when you're out shopping for a new bike.
Tire size: You used to ride a mountain bike that had 26" wheels. ALL mountain bikes had 26" wheels for many, many years. These days you can't buy a 26" wheeled mountain bike. It's all either 27.5" (also called 650b) or 29". Which one is best is hotly debated, but it is generally considered that 29" is faster, and 27.5" is more nimble, but even that is debated. You will be blown away by the improvement these wheel sizes have over 26" wheels.
Tubeless tires: All better mountain bikes will have tires and wheels that are ready to run without tubes, but when you buy them in the store they will be sold with tubes in them. It's easy to take the tubes out, and convert them to tubeless, and you will spend a lot less time on the side of the trail patching tubes, and you will get better traction as well. It does make changing tires a bit more of a process, but it's not that big of a deal. I would almost call this a must-have for NICA racing, since the rules do not allow anyone to help your rider change their tires on the course, and tubeless greatly reduces the chances of a flat.
Thru-axles: On your old mountain bike you used to have quick release skewers. At first glance it will look like modern mountain bikes have quick release skewers, but they don't. They have thru-axles. A thru-axle is much thicker, stiffer, and screws into threads cut into the frame, which keeps everything perfectly aligned so disk breaks don't rub, and adds stiffness to the frame and fork. This means if you have a roof-mounted bike rack that attaches to your forks, you will need an adapter or a different bike mount.
Head tube angle: Geometry of modern mountain bikes is nothing like the geometry of that old bike you used to ride back in the 2000s. One of the most important differences is the head tube angle. Modern mountain bikes have forks that stick out like old motorcycle "chopper" bikes (although not so obviously). This angle is measured between the fork and horizontal (like the ground), so the lower the angle the farther the fork will stick out. A fork with a low angle (like in the mid 60s) is called "slack" and a fork with a high angle (somewhere in the low 70s) is called "steep". Steep bikes are considered more nimble (bordering on twitchy) and slack bikes are slower to turn, but are more stable. Your kid will crash a slack bike less often when jumping.
Rear suspension: If price is any concern at all, I would avoid a bike with rear suspension as a first bike for a NICA racer. Unless you spend significantly more money they will be heavier than a hardtail mountain bike. Furthermore, a hardtail will develop better bike handling skills and will require less maintenance, and you can put that rear suspension money into better components.
Where does this leave you, considering your first real mountain bike purchase for your offspring? Well, if you can, spend as much as possible on your bike. Buying used can be a great choice, and should be considered as an option before buying new. You can get a lot more bike that way, but I still wouldn't buy anything more than 5 years old. Mountain bikes are experiencing a revolution in quality and innovation since about 2016 that is truly useful and valuable. Also, check with your bike shop about NICA discounts, which can be as high as 25% off a new bike.
One last thing: I would consider also buying a cheap "beater" bike for your kid to ride around the neighborhood and leave laying on its side in their friend's front yard while they play Minecraft in the basement during a rainstorm. A $1,500 bike is too valuable for this kind of task.
I have a long-winded way to make working bevel gears with involute tooth shapes for 3D printing here, but it's so long and such a pain in the butt that I thought an easier way is in order, so I streamlined the process. I'm using Inventor 2019, by the way. Here we go:
1) Make a new assembly and save it.
2) In that new assembly click the Design tab, then click Spur Gear.
3) Click the More Options >> button in the bottom right corner to expand the Spur Gears Component Generator window down.
4) Change Size Type to Module (if you're in my CAD 2 class, otherwise feel free to use Diametral Pitch). Change the Input Type to Number of Teeth.
5) Change Design Guide to Center Distance. Make sure the Internal checkbox is not checked. Use a pressure angle of 20°, and a Helix angle of 0°. Change your Module to 1mm, which is the smallest teeth I get a good result with on my 3D printer.
6) Type in the number of teeth you want on your smaller gear in the Gear1 area, then type in the number of teeth you want on your larger gear in the Gear2 area.
7) Hit Calculate. If you hit the little >> bar on the right side of the window it will show you data about the gears it's going to make.
8) Click OK. It will give you an error. I've never had it not give me an error that says my gears won't work, but they always seem to anyway.
9) Inventor will put your gears in the assembly. The teeth are not involute and overlap the teeth on the mating gear, so you can't use these parts in real life.
10) Right click on either of these gears and then choose Export Tooth Shape.
11) Choose the Pinion to export (which is Gear1).
12) If your 3D printer makes parts slightly too large (mine does) you will want to change your Normal Backlash to .006, which is the largest Inventor will allow you to enter with a module of 1mm.
13) Hit ok.
14) Inventor will make an extrusion of a circle with a sketch on the end of it showing the space between the teeth. Delete that extrusion, but leave the sketch.
15) Edit that sketch and delete the construction line circles (but not the solid outside circle).
16) In that sketch make a circular pattern of the space-between-the-teeth-shape, for however many teeth you have.
17) Trim the outside circle between each tooth so that it looks like a gear.
18) Finish that sketch.
19) Click the Manage tab.
20) Click Parameters.
21) Click Add Numeric.
22) Type OtherGearTeeth as the new parameter name. No spaces. Capitalization is important.
23) Click the Unit/Type cell in that row, click the + next to Unitless, then choose Unitless (ul) and click OK.
24) In the Equation cell for that row, type in the number of teeth in the OTHER gear. You will notice that there is already a parameter called NumberOfTeeth with the number of teeth in THIS gear, so make sure you enter the number of teeth in the gear that this gear is going to mate with.
25) Click Done.
26) Make a new sketch on the YZ Plane (which can be found under the Origin folder in the Model bar on the left side of the screen).
27) You should see the side of your gear sketch going through the origin, so it will look like a dotty line running up and down.
28) Now you are going to draw the following lines:
Make sure you don't accidentally make the two green lines perpendicular to each other.
29) Use the following picture to place the next 4 dimensions. You can cut and paste these formulas into your dimension editing boxes.
29a) The angle between the left angled line and the centerline is:
90-(( 90 deg - atan(OtherGearTeeth / NumberOfTeeth) ) / 2 ul)
29b) The angle between the construction line and the centerline is:
90 deg - atan(OtherGearTeeth / NumberOfTeeth)
29c) The diameter between the centerline and the very bottom point of the two solid lines is:
HeadDiameter + .001
29d) The diameter between the centerline and the bottom of the construction line is:
PitchDiameter
30) Everything should be fully constrained now, so finish your sketch.
31) Revolve that triangle around the centerline.
32) Click Start 3D Sketch.
33) Click Project to Surface.
34) The "gear sketch end" of your cone is the Faces, and the sketch of the gear is the Curves. You can just click on the end of the cone, but you have to use a bounding box to select the gear sketch. It seems to work best if you don't include the entirety of the near end of the cone in the bounding box along with the gear sketch. Click OK.
35) Click Finish Sketch.
36) Click Axis and make an axis right through the middle of the cone.
37) Under Point, choose Intersection of a Plane/Surface and a Line, and make the surface the "non-gear-sketch-end" of the cone, and the line will be the axis you just made through the middle of the cone.
38) Click Loft, and as your first sketch choose the projected 3D sketch of the gear, and as your second sketch choose the point we just made at the other end of the cone.
39) Sometimes Cut works for the loft, and sometimes Intersect works, and I can't tell why it's not consistent, but one or the other will work. You may have to try it both ways. I try Intersect first usually.
40) Now you have a bevel gear. You will need to trim it up to get it to fit into your model, but it should have the correct teeth. Don't forget to save your work!
41) The process is exactly the same for the mating gear, but remember when you're adding the OtherGearTeeth parameter for the second gear, you won't type the same number of teeth into it as you did this time (unless both gears have the same number of teeth)
Here's the TL;DR for this post: I bought a 2019 Trek Marlin 5 and realized the fork sucks. I used Suntour's upgrade program to buy a new Radion XC-LO-R fork for $200 and I'm thrilled with it.
I recently got into mountain biking after being out of the bike scene since about 2004, when I was a full-time bike mechanic for a few years. I haven't ridden at all in about 15 years, and even back then I ended up selling my Cannondale F600 because there weren't any good trails to ride around here (Springfield, MO) and the road biking was so good. A few years back I bought my son his first good bike, a 2015 Trek Marlin 5. This last year we visited the Crystal Bridges Museum of American Art in Bentonville, Arkansas, and as we walked from downtown to the museum we saw the All-American mountain bike trail, and were blown away. Have you seen it? Insane. It turns out Bentonville is packed with amazing trails, and more importantly it turns out that there's a really nice new mountain bike park near my town, the Two Rivers Bike Park. I dug out an ancient Trek 800 with solid forks and cantilever brakes from the '90s my neighbor had given me and we went riding the next day.
It was pretty awesome, but my arms were so badly vibrated that I couldn't feel them for an hour afterward. Still, I was worried that I wouldn't be into mountain biking enough that I would do it long-term, so I mostly rode that bike with my son for about a month, before breaking down and buying my own Trek Marlin 5. I had ridden his on the beginner and intermediate downhill trails, and it was so sweet. I could ride so much faster, more comfortably, and with better control on his, even though it was a bit too small. When I took mine out on the trails it was a great improvement over the old Trek 800, but I was distinctly disappointed in its performance compared to my son's bike.
Mostly my experience consisted of my front shock (a Suntour XCE 28, which comes stock on the 2019 Marlin 5) klunking loudly as it topped out (which is like, always), and bouncing around like a pogo stick. The ride was not plush in any way. There is absolutely no dampening, and of course no rebound adjustment. I was kicking myself because I hadn't even test-ridden the bike, as I assumed it would be like my son's. His front forks were nothing to write home about (Suntour M3030, described on the Suntour website as a "metropolitan" fork), but at least they didn't make machine-gun klunking noises like mine did when riding over rough terrain.
I decided I would upgrade, but dang! Good shocks easily cost more than my whole bike. Good shocks seemed to require a tapered head tube, which I didn't have, or even know what that meant. Disappointment. Despair. I desperately considered adding some kind of dampening myself. Then on a forum somebody mentioned the Suntour Upgrade Program. You can upgrade your Suntour forks to a nicer fork, and on the forums it was told that Suntour offers an actually decent air-spring fork with adjustable rebound and a lockout with a 1-1/8" non-tapered steerer tube. The Raidon! I had to prove that I was the original purchaser of the crap fork, but my bike shop printed me a new receipt for that, and for $199.95 and free shipping I was the new owner of a non-crap fork.
When it came in the mail I cut it off at the same length as my old one, transferred over the lower bearing race, and installed it. I turns out you can buy a fork pump to adjust the fork air pressure more easily than what I did, which was to over-inflate the fork and bleed off pressure until it feels good, but whateves.
Before I installed it, I noted how heavy the XCE 28 felt in comparison to the Raidon, so I pulled out the postal scale and weighed them.
6 pounds and 3.4 ounces! Obscene!
Now for the Raidon:
That's more like it! 4 pounds and 6.6 ounces, a nearly two pound weight savings! Sweet!
The whole point of this post is that I took it riding today, and it is like having a whole new bike. I absolutely can not recommend this upgrade enough. I was easily faster, jumped higher, landed softer, and had more control and comfort than ever. I could be wrong, but as far as I can tell, the lowest end bike Trek sells with an actual air fork is the X-Caliber 8, for $1,200. I feel like this makes the Marlin 5 at $540 plus $200 fork upgrade a really good deal. I realize the X-Caliber has a lot else going for it, but still.
When I was a bike mechanic I got to talk to a lot of customers, and I would always focus on how much fun a bike/part/upgrade was. Most of us are buying fun at the bike shop. Can you ride a Wal-Mart bike on the trails? Yep. Will it be a fun enough experience to make you want to go back the next day? That's a lot less likely. This fork easily passes my fun test.
While we're talking about the Trek Marlin 5, I want to offer a few of my other, non-fork related thoughts on the subject. Firstly I wish I hadn't bought a bike with a freewheel cassette. Most modern bikes have the ratcheting mechanism in the rear hub, not in the gear cluster like the Marlin 5 has. I could have upgraded to the Marlin 6 to get the freehub, which has unlimited upgrade potential as far as rear gearing and derailleurs go, but I didn't pay enough attention at the time. The thread-on freewheel gear cluster has no upgrade potential, and now I'm stuck with 7 gears in the rear until I upgrade my whole rear wheel. Secondly, the rear Tourney derailleur is awful. The main problem is that the spring in it is weak, the body of it is heavy, and so it klunks against the gear cluster when I hit bumps. It's almost as annoying as the topping out of the crappy old forks. Additionally, it often changes gears on its own when I come down from a drop or jump. I upgraded to an Alivio rear derailleur, which is two or three steps up from a Tourney, and for just $36 that tells you how cheap the Tourney must have been. The klunking and mis-shifting is gone. It's a noticeable improvement. Thirdly, I'm pretty happy with the wheels, especially for how cheap the bike was, but I really wanted to convert it to tubeless, which I did with the stock wheels and tires. You can see the process here. After that, I upgraded the tires to Maxxis 2.20 DHF and DHR tires, and they fit. Fourthly, the brakes on the Trek Marlin 5 are awesome. My son's 2015 Marlin 5 has disk brakes too, but they are cable-controlled mechanical jobs. Mine are hydraulic and the difference is huge. Back when I was a mechanic in the early 2000's I remember the early adopters of hydraulic disk brakes always bleeding them and endlessly tinkering, so I was hesitant, but apparently times have changed. These aren't even near top of the line brakes, but I love them. Fifthly, I'm seriously considering converting to a 1x10 drive system. I would need a new rear wheel with a freehub, a new 10 speed cassette, a 10 speed shifter, a 10 speed chain, a narrow-wide front chainring, a crankset that would fit a new chainring (current crankset has riveted chainrings), and a bottom bracket that would fit a modern crankset. That sounds like a lot, but I'm pretty sure it could be done for about $350. I guess at that point I really am into the X-Caliber 8 price range, but as a former bike mechanic it's pretty appealing. Edit 3/21/19: I've pretty much given up on converting to a 1x system on this bike, but rather I'm saving up for a different bike. I'm currently deciding between a Roscoe 8, a Stache 7, or a Fuel EX 8. Sixthly: A good upgrade for the front derailleur is the Shimano FD-M313, which is no longer made, but are still available. Don't get a low mount front derailleur, as they will interfere with larger tire choices, but rather the M313, which is a high mount and doesn't take up so much space behind the seat tube. It's cheap and solved most of my chain suck issues.
I started teaching high school wood shop recently, and one of the woodworking projects I found I like most is making skateboard decks. This rekindled my interest in skateboarding as an adult, after not skating for over 25 years. I started again by skating the longboards I built, just cruising around on them, but it felt so good that I started thinking about doing the kind of skating that I'd always dreamed of but had been too afraid to do: pool skating. I've never skated half-pipes, and I can't do an ollie, but I decided to give it a try.
So, in July of 2016, at 45 years old, I went to the park and pushed around the bottoms of the pools, and it was every bit as enjoyable as I envisioned. I only had a longboard, which made it hard to turn tight enough for pool skating, but I had that first taste. I got some guy to show me how to drop in, and after a few tries (no hit-the-ground falls though) I was able to drop into about a four foot bowl. The next day I went to my local skate shop and bought a more traditional board, a popsicle-shaped job that could make the tight turns when carving a pool, and then went right back and dropped in again. Unfortunately, the short wheelbase of the popsicle deck had a completely different feeling, and I fell backwards and dislocated my shoulder on the first run of my second trip to the park.
`
Here I am at the hospital after an x-ray.
It was maybe 9 months until I was able to sleep on my right side again, and after a year I still couldn't throw anything. After a long and frustrating year and a half I had healed enough to think about going back for my third skate session. I read a lot and learned that a longer wheelbase would help with the kind of fall I took, so I bought yet another deck made just for pool skating with a 15.5" wheelbase, and I've been pool skating with that for about four months now.
Eureka Springs skatepark is a chill little pool in the trees.
Feels like flying.
The important and beautiful thing about pool skating is that it feels so good. The feeling of gravity and centrifugal forces, the weightlessness at the top of a carve, the flow and focus, it is all so much like I imagine flying would feel. I still can't get into the tiles or coping, and my frontside carves are weak, but how I look skating doesn't matter to me at all, and I wish I hadn't worried so much about how I looked back when I first wanted to do this in my teens. I healed a lot faster then.
11/4/2018 Edit: I have now built up the courage to drop in, which has enabled me to get into the tiles in my local skatepark's bowl.
I teach high school computer aided drafting, engineering, digital electronics, and wood shop. One of the problems I have is that I often forget what period I'm in, and also what time it ends. I'm not all, "Where are we? Who are you people?" or anything, it just feels like third period sometimes during second period. And no matter what, I can never remember when the classes let out. I made an outer ring to my classroom clock showing where the minute hand will be when the period lets out, and it's pretty helpful if I can remember what period I'm in. We have a different bell schedule on Wednesdays though, with a later start, and fifth period happens before fourth period that day, so that's not helpful when trying to figure out what's going on either.
I've long dreamed about a long, linear clock that slowly travels down my 32 foot classroom wall, with the periods all blocked out, so that I can just glance at it and know what period I'm in, and how much time is left. I wanted it to automatically show the different bell schedule on Wednesdays, reset itself at the end of each day, and not run on the weekends. I wanted it to be highly (even unnecessarily) mechanical with exposed electronics, to reflect the subjects that I teach, and I wanted to build it entirely with materials and methods my students have access to in my classes.
So, finally, after four years of dreaming, one semester of brainstorming and designing, and two months of all my spare time doing actual fabrication and troubleshooting, the clock is working, although in an advanced prototyping stage.
Normally, this is where I would lay out a step by step process for building your own clock, but I'm not going to do that here. It's just too custom fitted to my wall, and if anything needed re-gearing to make it fit into your space, it would basically need a complete redesign. What I want to focus on here are the essential skills that anybody would need in order to design this, or something like it.
First up is:
Conceptual Thinking
No question about it, this is the hardest part of a project like this. It requires the ability to visualize what you want to end up with, and in the context of the tools and skills you have available to you. One of my favorite sayings is, "To a man with a hammer, every problem looks like a nail." Conceptual thinking requires that you have a large enough skill set to solve the problem, and have an understanding of each of those skills deep enough that you can be creative with its implementation. It boils down to a vision of the final project, and a vision of the path to getting there.
For the clock, my major hangup was the motor. I was convinced the only way I was going to be able to achieve the positional accuracy of this clock was with stepper motors. I've never used stepper motors in a project, but I've been wanting to for a long time. I've read books and internet articles about them, and I feel like I have a good understanding of them. I know that they need a dual H-bridge driver and a microcontroller, at least, and that they come in several styles of winding, that one of their strengths is holding torque, and that they are power hungry.
However, I didn't want to change the battery all the time, and I don't need any holding torque at all on this project, so I suspected that they weren't the best solution in this case, but I still really wanted to use them, and I didn't know how else I would get my positional accuracy needed to get the hand to land exactly on a minute mark every time. One day I was reading an article (probably on Hackaday) in which somebody was using a wheel with a hole in it to count light pulses to make a robot go an exact distance with a cheap brushed dc motor. Boom. There it was: the solution, when I wasn't even researching my clock, but just reading for enjoyment.
Every single part of this clock went something like this. How was I going to get exact second or minute pulses? (With a cheap hacked quartz clock movement? With my microcontroller's inaccurate internal clock? From the internet with an ESP8266 wifi module? A DS1307 real time clock?) How would I account for the different schedule on Wednesday? What would I use for power? How would it return at the end of each day? Could I prevent it from running on the weekends? How would I paint my walls? What is the ideal microcontroller for this project?
All these questions and so many others! And every one was a hard-fought battle for the knowledge required to make it happen. Not every single thing must be known during the conceptual phase, however. You just have to know enough to know that you can figure it out when the time comes, or to at least have a couple of backup plans. I won't lie; it's hard. It's why when you post an elegant 3D printed solution to a problem on the internet everybody wants the .stl files. It's why so many books and magazines write complete how-to articles with parts lists and completed downloadable code. If I were starting my journey towards making 3D printed, laser cut, and CNC'd projects with microcontrollers and electronics, I would read, read, and read. Blogs, books, parts supplier's parts descriptions and tutorials. Every day, for years.
This brings us to:
Mechanical Design Skills
For me, this is the easy part. After a college minor in drafting, and 20 years of professional 3D modeling experience, I can usually breeze through the mechanical design portion of a project. I realize that this is not going to be a common experience for the new maker though, so I'm going to break down the design skills into the sub-skills of hand sketching and 3D modeling.
My computer aided drafting students HATE to hand draw their concepts before they jump on the computer and start 3D modeling their parts. They just want to get to the fun part, like they're playing an expensive game of Minecraft. Soon enough though, they realize they can't go any further because they don't have a plan, they can't visualize how their parts go together, and then it is evident that they have no idea what they are doing.
Paper drawings are the solution! I'm not saying you need to break out the T-square and triangles (although that is pretty fun), but some good engineering graph paper, a pencil, and a big eraser will make the design process shorter and faster in the long run. I prefer to draw my projects in full scale when possible. One of the big problems I see when trying to design things in a computer aided drafting program is that parts are often accidentally designed with features so small that they are nearly impossible to fabricate, but it is difficult to get a sense of scale in 3D software. When drawing on paper it is important to draw your objects from more than one side, so that you get a sense of depth and how the parts fit together front-to-back.
I personally think that 3D modeling skills are the number one thing you can learn to improve your maker game. 3D modeling is the Microsoft Word of the 21st century. It enables you to 3D print, or CNC cut, or laser your own designs. It helps you make plans for complicated things you are going to fabricate by hand as well. You should choose a piece of software and learn it well. If you're a student or a teacher, I would suggest Autodesk Inventor, since it's super powerful and it will be free for you. Otherwise it's insanely expensive for the hobbyist. My second choice would be Autodesk's Fusion 360. I've never used it, but it has almost all of the same capabilities as Inventor (with the glaring omission of a gear generator) and it's free. There is a huge hobbyist user base and lots of online tutorials. It can generate .stl files and g-code for CNC fabrication. There are so many other options as well, but try to choose something modern and capable that can grow with you as your skills grow. Resist the temptation to choose a piece of software just because it seems easy to use.
Electrical Design Skills
There has never, ever, ever been a better time to learn electronics. Not only is there so much information on the internet about learning electronics, but newer, cheaper, more powerful, and easier to use components are being released constantly. Companies like Adafruit, Sparkfun, and Pololu are taking tiny, hard-to-solder chips and building easy-to-use breakout boards with them. Microcontrollers and microprocessors programmable in dozens of popular languages, including graphical block-based languages like Scratch and Blockly. The biggest problem quickly becomes choosing a platform to base your designs around.
I would make it a high priority to learn how to solder and etch circuit boards using the toner transfer method. I would choose a chip microcontroller (like an AVR or Picaxe) rather than a board microcontroller (like an Arduino or Micro:bit), preferably in a language you already know (I only know Basic, so I use the Picaxe microcontroller). This suits my style of projects, which are small, fairly simple, mechanical, and inexpensive.
Fabrication Skills
I hesitated to include fabrication skills on my list here, because so much of what we can build today is built digitally, with lasers and 3D printers and CNC equipment. If all goes well, humans shouldn't have to touch the parts too much on small projects like these. I did drill out all of the holes on my gears so that I would have a perfectly round, more precise hole, and that required a small drill press. The gears rotate on axles made of 3mm threaded rod and 4mm OD brass tubing, and those needed to be cut with a small hand saw. On many of my projects I cast urethane rubber parts with silicone molds. At any rate, you should not hesitate to purchase a tool and learn to use it. It's probably going to cost the same amount of money when you buy it later, and you will have all of the time between now and then improving your skills with that tool.
Persistence and Troubleshooting
This is a tough one. Let me assure you that nothing is ever going to go right on the first try if you are pushing yourself to build and design more amazing things all the time. On this clock, it turns out that infrared light shines right through my 3D printed plastic in the Z axis, so the clock never knew it had traveled one rotation of the minute wheel. It took a week to figure out that it was a mechanical problem and not a problem with my IR emitter or detector, or the code that interfaces with them. The motor driver I chose, the SN754410, draws 25mA all the time, even just sitting there overnight, apparently, and that's enough to drain my 1000mAh battery in just one day. Not cool. I had to switch to a DRV8838, which is more efficient, but required rewiring all of the motor driver circuit and making major modifications to the microcontroller program. The acrylic I made the base plate out of is starting to crack from it's laser cut edges, apparently from an incorrect power setting I used on my laser. I still need to figure out what caused that and exactly what I'm going to do to prevent it. It never ends.
The internet is such a great resource in the aid of troubleshooting. I had my questions answered over on the Picaxe forums when I couldn't go any further on my own. Almost any problem you have, somebody has probably faced it before as well. Sometimes it's best to sit a project aside for a few days to roll it around in your subconscious when things seem impossible. It's important to remember when starting a project that it's going to be hard almost all the way through it, and just get mentally ready for it. I find that documenting my projects online (like this) is a great way to keep my motivation up. I think about how cool some person in some place I've never even heard of is going to think it is.
