Monday, January 15, 2018

Kid Coaster

I built a kid-sized roller coaster in the basement! Here's the story.

Pulling Out of the Station

For the 2013 holidays, I had constructed a kid-sized railroad train for my daughter. I adapted the front car from a Radio Flyer Classic Walker Wagon and the rear car from an older model by replacing the wheels with CW4 U-wheels from CamOnWheels. The track consisted of two long PVC pipes, tied periodically by metal clamps affixed to wood beams.
This train was pretty cool. Thanks to ball bearings in the wheels, it moved smoothly and was satisfying to operate. But it could only go in a straight line, and it couldn’t go very fast without risking derailment.

Next Stop: Kid Coaster

I started thinking about the holiday train’s successor. I had been impressed homemade roller coasters I'd seen online. Could I build a small one?
I started researching roller coaster construction. I studied the photographs at and I read books and forum posts.
There were still a lot of gaps to fill in, but I began to think I might be able to pull it off.


I decided to build the roller coaster in the basement, so I could work at night and keep the resulting clutter to a minimum.

Wheels and Wheel Assemblies

Roller coasters have several wheels. Some of those wheels are positioned at right angles to one another, to keep the roller coaster on its tracks as it follows a curved trajectory.
These wheels are typically grouped into assemblies.
Wheel assemblies on pro wooden roller coaster cars are usually metal. I didn't have convenient access to welding equipment, so I chose wood reinforced with steel bolts. I'd attach four of these assemblies to my vehicle.
For the actual wheels, I selected nylon inline skate wheels. Four of these wheels are strong enough to carry an adult. I'd also use four, but design my loaded vehicle to weigh a lot less than an adult.
The wheels would need to accommodate at least the track thickness, which I set at 19 mm, based on available boards.
I fired up SimpleCAD and came up with the simplest design I could. I iterated on it a couple of times until arriving at this.
The guide wheels on the bottom and side never carry the full load of the vehicle. As a result, they can safely hug the track, exposing it to the brunt of their modest force. The top wheels, on the other hand, typically do carry the full weight (or close to the full weight) of the loaded vehicle. Consequently, they would sit on a laminated track support.
The wheels are all bolted-in, and the bolts also serve as their axles. The side wheel's axle has to be in a different plane than the top and bottom wheels' axles. But since there are four wheel assemblies, the forces all balance out.
On the diagram above, light gray is steel and dark gray is nylon. The olive rectangles are bolts and the red rectangles are inline skate spacers, which brace the wheel bearings. Most everything else is wood.
The dash-outlined rectangles in the wood on the left side indicate pocket holes. They permit the wheel assemblies to sit flush against the vehicle, without interference from the bolt heads.
The gray-brown areas on the righthand drawing indicate drill bores.
Bolts would be secured with Nylock nuts at their ends (not depicted.)


The vehicle itself would basically just be a crate long enough for a kid to sit in. I'd assemble it from a series of wood slats mutually braced and held together by screws.


Although some newer pro wooden coasters do have prefab metal tracks, most are still wood.
Some homemade coasters use tracks made out of PVC pipes that have been heated, and then bent. But that produces toxic gas. I was also worried that cyclic strain would lead to mechanical failure over time.
I made the decision pretty early on to go with wood. Wood is strong, forgiving and easy to work with.
As much as I intially wanted to attempt a banked turn, the available space wouldn't really allow it. I eventually settled on a track path that would trace out a valley between two peaks in a single vertical plane.
The vehicle would hang from its four wheel assemblies, threaded around the track. I picked a track support gauge (the distance between the two tracks) of 69 cm, to accommodate a typical crate plus a margin.
I managed to find an industry handout on safety inspections that contained isometric drawings of the “ledgers” that tracks and track supports are built atop. I basically copied that design. It would need multiple reinforcing beams to safely support a 23 kilogram passenger at a factor of four margin of safety.
Wherever possible I spread out loads in this manner, to eliminate single failure points.
The design for the pitched track trajectory would need to be informed by subsequent testing. I ended up revising it many times over the duration of the project.

Sourcing and Testing

I found most of the hardware I needed at the hardware store. An exception was the 10 cm long steel bolts for the top wheels, which also proved expensive. Luckily I only needed four of them.
The lumber for the track and understructure came from my local Home Depot. Its quality proved uneven enough that I resolved to use a wholesaler on my next project. I learned to sift through entire lumber piles and revisit after restockings to find usable timbers.
Originally, I had planned to use published product specs to determine how much load each component could handle. But I rarely was able to find any. Instead, I ended up having to conduct my own tests.
For example, to ensure that the vehicle’s slatted wood bottom was up to 4 times the required load, I built a prototype and proceeded to jump up and down on it. It held.
The track surface and support laminates would need to be bent to assume the shape of the valley. I hoped to accomplish this without the need to resort to steaming or notching.
With essentially no prior woodworking experience, I was worried about bending the track timbers into place with clamps. How far could I safely bend them? If I bent them too far, would they suddenly snap, assaulting me with splinters and chunks of broken wood?
So my original plan was to use thin laminate strips, which I figured would be easy to bend.
They were. In fact, experiments showed I could safely bend them significantly further than I had supposed. Since the required number of strips would have been expensive, I decided instead to go with thicker “2 by” timbers. These did necessitate the purchase of special, monster-sized bending clamps, but cooperated afterward.
Luckily, further, cautious experiments suggested that I couldn’t supply enough force by hand to break “2 by” timbers (but don’t try this at home!)
So the track support ultimately consisted of a stacked laminate of pine nominal 2 by 4 by 10’s. I would secure them with a portable electric drill and staggered deck screws.
Finally, I'd cover the ledger surface with bent peg boards.


I started in on the wheel assemblies. It was hard to get completely straight cuts with my Japanese hand saw. Even after buying an engineer’s square, I ended up rebuilding the wheel assemblies several times to get them right.
My design also involved very long bores that I kept screwing up with a hand drill. So I got a drill press. That helped, but the drill press didn't always have enough vertical clearance when its support tray was installed. So occasionally I had to replace they tray with a makeshift sub-base and/or drill from both ends, trying my best to meet in the middle.
Lengthwise, the track surface consists of two separate boards and I could never manage to get completely smooth, first-order continuity at their contact point. But, to my surprise, testing revealed it not to be a serious problem.
I needed many deck screws to complete the track understructure. I learned the hard way to consistently drill-out adequate holes for them ahead of time.
I'd always been too lazy to build a sawhorse for previous projects. During construction on this project, the incomplete ledger often served as one. Slightly inclined, but extremely secure.
Once the peg boards were installed, I found I could actually lie down on the ledger!
Maintaining wheel clearance along the entire length of the bent track required some contour adjustments and a lot of shaving. But once everything was planed down and the vehicle was reinstalled, it felt correct.


I loaded the vehicle up with weights and did a test run. To my relief, it worked well.
I couldn’t figure out how to attach seat belts to the vehicle without compromising its structural integrity. So instead, I opted for a padded restraint bar. I screwed wooden socket pairs into both sides of the otherwise symmetric vehicle, to accommodate different sized-kids. The dowel bar could be secured in these ports with a clamp.
Inspired by the styling on deluxe Radio Flyer wagons, I made some cushions from textured Denier Nylon Oxford fabricquilt batting, and Muppet foam. For the outside I assembled a sort of fabric tube, which was tricky to feed through the sewing machine. Generous pinning helped.
Then I hot glue gunned the foam and batting together. I inverted the fabric tube and slid it over. I folded the ends up like wrapping paper and sewed them up by hand.
With a full maximum load, the vehicle nearly reached the other opposite peak after release. Nevertheless, it was important that the vehicle not run off the end of the track, even if inadvertently overloaded or pushed.
So I built cradles into the ledger on each end that could accept vertical stop beams. This way, I'd be able to easily remove the vehicle for repairs when needed. I duct-taped a bunch of Muppet foam to the beams, to dissipate the force of any impact.


Kid Coaster has been in regular operation for a month now!
I tend to think the best way to understand how something works is to build one for yourself. I do feel like I understand roller coasters better now, but really I just have more specific questions.
My next woodworking projects will be to build a derby racer (with my daughter) and a boat. But I find I'm having a hard time bringing myself to dismantle the roller coaster track, to make room.

Sunday, November 26, 2017


After learning that the dead graphics card in my 2011 iMac would cost $700 to replace (!), I needed a new Mac desktop system.
The iMac had been a solid computer overall, but its fancy monitor was now effectively useless to me (older iMacs do have a "Target monitor mode" that allows them to be used as an external display for another computer, but only if the old iMac is still bootable.)
I didn't want to end up in that situation again, so iMacs were out.
I considered a "trash can" Mac Pro, but didn't like its cost or power utilization.
Much has recently been written about the Mac Mini's three years without an upgrade. I reluctantly decided to buy one anyway, with 3GHz and an SSD. I'm glad I did! The SSD really makes it feel zippier than any desktop Mac I've previously owned.
(I recently recounted my experience getting Adobe CS3 up and running on it.)
But the computer configuration I had really wanted all along was a tower, like older Mac Pros, and like the zareason Limbo 5880 Linux file server I've migrated most of my files to.
So, I decided to assemble a Meta-Tower for my new Mac Mini, using a Mesh Stainless Steel Stackable Legal Size Letter Paper Tray Desktop Organizer. (You may want to get one from The Container Store as the ones on Amazon seem to have a tendency to arrive a little bent.)
The Meta-Tower co-locates the Mini with its peripherals and preserves some degree of physical access, without seriously obstructing waste heat dissipation.

The same general idea, of course, could be applied to an Intel NUC, a Raspberry Pi, or any other compact, self-contained computer.
The Mac Mini is snuggled on the bottom tier, alongside a router.
The middle tier has an external hard drive ("HDD"), for Time Machine backups.
The top tier has a USB 3.0 hub (which has proved to be largely unnecessary as recent Minis have a generous collection of USB ports.) It also hosts a couple of HDD docks, which I use for archiving astrophotography video. They let me swap HDD's in and out, almost as easily as Flash drives.
I configured the devices so things I'd need to access (buttons & ports) faced forwards, or at least were near the open front. The Meta-Tower sides were partially obstructed, but not so much that it prevented me from threading cords through.
I expected I'd need to physically secure everything in place, but it turned out the cords were rigid enough to do that relatively well. Well-paired devices also braced one another.
Where possible, I plugged power cables into a power strip on the floor beneath the desk. Devices that need to be plugged in and unplugged alot have a separate power strip atop my desk.

I tried to use the shortest cords I could find. Lengths of 3 feet (91 cm) are definitely better than 6 feet (183 cm)!
I built another Meta-Tower for my desktop game consoles.
The bottom tier holds my Nintendo Wii. My Retro Freak needed to be on top, so I could continue plugging game cartridges into it from above and access its front-facing game control ports. The top tier also houses a classic controller adapter, which has additional ports.
I've used a Brother labeler to distinguish some cartridge slots and cables, and an HDMI switcher to tie it all together.
I'm not a laptop fan, but I have to use one for work. I reserved the third port on my HDMI switcher for it. The laptop itself won't fit in a desktop organizer, so instead it lives atop a Rain Design mStand Laptop Stand.
Meta-Towers have some limitations. Unlike a real tower, the satellite devices don't all switch on and off in concert with their associated computer.
As mentioned, it can be difficult or impossible to access devices that aren't on the topmost of a meta-tower.
And of course there still are quite a few visible cords.
But when all is said and done, Meta-Towers have reduced the amount of clutter on my desks. I also find them conceptually helpful, as organizational units.

TARDIS Roundel Combination Bulletin/Peg- board

I'm happy to report that my TARDIS Roundel Combination Bulletin/Peg- board is still going strong!

Thursday, November 23, 2017

Ad Hoc Artwork Scanning Station

If you're a parent, you may also have struggled to keep up with all the artwork your child brings home. At first, I saved everything. But I quickly ran out of filing cabinets!
I tried a scanner for a while. It produced good results, but took more than a minute of processing per document.
Instead, I decided to set up an ad hoc scanning platform. I dusted off an old digital camera and got out my trusty Sony VCT-R100 Lightweight Compact Tripod. Then, I went to the hardware store and bought a 6-inch long 1/4"-20 headless bolt (also sometimes called a threaded rod) and a 1/4"-20 x W3/8" x L7/8" Coarse Thread Coupling Nut.
I put the coupler over the screw on top of the tripod, where a camera would normally go. Once I'd installed the coupler, I screwed the headless bolt into it. Then I screwed the camera onto the bolt, using the camera's threaded mounting port.
I put a large piece of white poster board down on a table, to serve as a neutral background, and set down the tripod and camera adjoining it.
When the room I'm working in is poorly-lit, I supplement with an LED desk light.
I cut down on output storage footprint by using JPEG image encoding, which is the default on most digital cameras.

To save time and trouble, it helps to minimize the amount of necessary post-processing. When I photograph small items or items with lots of detail, I avoid the need to crop by brining them closer to my camera. To accomplish this, I built a raised platform out of wood slats. I swap it in and out as needed.
Sometimes, post-processing is unavoidable. Although JPEG is a lossy image format, there are utilities to perform simple JPEG image transformations without additional information loss. On Windows, there's jpegcrop and JPEGCrops. On macOS, the Photos app performs lossy transformations, but always preserves the original file to apply them against, which reduces loss.

Tuesday, November 7, 2017

You Can Install Adobe CS 3 Applications on a new Mac running High Sierra

Want to install Adobe Photoshop CS 3, Adobe Illustrator CS 3, or Adobe Flash CS 3 on a new Mac running macOS High Sierra? If you own a license, it's possible.
The copies you probably downloaded way back when required activation by a remote server that's no longer online. Luckily, Adobe will give you a new serial number and installation that doesn't require remote activation.
Visit and log in, creating an account if necessary. Then plug in your old product serial number.
Save-down your new serial number somewhere safe. Then, click the appropriate product download link. If you don't already have Akamai web installer installed (and you probably don't), then you'll get that — not your Adobe CS3 software. If necessary, complete the weird installation process for Akamai Web Installer. This should result in a new macOS control panel. If opened, this control panel will pronounce Akamai "started".
Now, go back and click that download link again in your web browser, this time with Akamai running. You should get your CS3 product download!
Open up the .dmg file, double-click the product folder, and run the Setup tool. Pick a volume to install your Adobe software on. Once installed, run the software. You'll be prompted for the new serial number. Afterwards, you may see a blank dialog box. Wait a few minutes and receive a message that your software can't be "registered". That's fine, elect never to register.
After that, you should be good-to-go!
You may want to uninstall the weird Akamai web installer at this point. Open the Akamai folder in your user account's Applications folder. Then run Akamai NetSession Uninstaller.
If you asked me, it's something of a minor miracle that these applications still work. I'm guessing it's somebody's job at Apple to keep macOS upgrades from breaking them.

Thursday, July 18, 2013

Like Saturn's Rings, It's a Galactic Love in Future Time

The conventional wisdom says you can't do much astronomy around bright street lights, that you can't take good pictures through a Dobsonian Reflector telescope, and that you definitely can't photograph outer solar system moons with one.

I'm happy to report it's all wrong! My brother and I used a relatively inexpensive 254mm Dobsonian Reflector telescope, which some amateur astronomers build at home, and a 3x Barlow lens, to get some pretty decent pictures of Saturn and its moons.

Dobs are mechanically simple. The Earth keeps turning and they pretty much sit there. So at any serious magnification, objects pass into and out of the telescope's view quickly. If you tried to take a conventional "long exposure" photograph, you'd get star trails.

Fortunately, there's stacking. "Stacking" is a neat trick where you can use a computer to treat a video like a very long exposure photograph. In fact, better than. You take all the best frames & computationally smoosh them together into a single picture.

DSLR cameras boast "high definition" video, but it really only uses about a ninth of the pixels on the imaging array! Fortunately, many Canon DSLR cameras let you choose to have those pixels be contiguous. That's good, because you can put all of them behind your image. The feature is called "movie crop mode" on the EOS Rebel T2i, and 3x digital zoom on later models. Getting your target in this frame is not easy, but with patience and a well-calibrated finder scope it can be done!

I haven't found an image stacking program that I love yet. I used Lykenos on Mac OS X. Automatic frame alignment is a must-have feature.

The stacked image suffers from two problems: the planet is too bright, and its moons (mostly out of frame, above) are way too dim!

It's pretty amazing that our eyes can see the planet and its moons through the telescope at the same time. To see them in the stacked digital image will require more work.

For this post-processing, I used Photoshop. But you could just use Gimp, Picasa, or iPhoto (free with Mac purchase). You can accomplish a lot with just the brightness and contrast controls, but the moons may be easier to tease out using Levels adjustment or Gamma filtering.

So here's the finished product, 129 frames stacked from July 17 at 10:16 PM local time in Hyattsville, Maryland.

My father-in-law points out that you can see the Cassini Division in the rings, and some banding on the planet.

Here are the moons:

That's almost certainly Titan, up top. The vaguely Saturn-shaped thing is glare off the planet.

If you're curious, here's the video that these images were constructed from.

Thanks to Alan, for moral support!