A line art schematic of a bicycle CVT drive. Two large green circles at the bottom have the text "1. Increases speed" where the crank arm would enter the system. A series of cam arms highlighted in red say "2. Converts from rotary to reciprocating motion." Finally, a blue highlighted bearing says "3. Converts from reciprocating back to rotary motion."

A Look Inside Bicycle Gearboxes

March 2, 2023 by Navarre Bartz 23 Comments

While bicycle gearboxes date back to at least the 1920s, they’re relatively unseen in bike racing. One exception is Honda’s race-winning mid-drive gearboxes, and [Alee Denham] gives us a look at what makes these unique drives tick.

Honda has developed three generations of bicycle gearbox as part of their company’s R&D efforts, but none have ever been released as a commercial product. Designed as a way for their engineers to stretch their mental muscles, the gearboxes were only used in bike races and seen at a few trade shows. In 2004, the third gen “derailleur in a box” led to the first gearbox victory in the Downhill World Cup Circuit.

The third gen gearbox differs significantly from the CVT drivetrains in the first and second generation gearboxes, but it is unclear why Honda abandoned the CVT. [Denham] has a nice animation detailing the inner workings of these CVTs based on information from the original patents for these rarely seen gearboxes.

Derailleurs remain the primary drivetrain in racing due to their lighter weight and higher overall efficiency. While still expensive, the decreased maintenance of gearbox drivetrains make a lot of sense for more mundane cycling tasks like commuting or hauling cargo, but only time will tell if the derailleur can be supplanted on the track and trail.

For more on bicycle drivetrains, check out this chainless digital drivetrain or the pros and cons of e-bike conversions.

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A grey car sits in the background out of focus, its front facing the camera. It sits over an asphalt roadway with a metal rail extending from the foreground to behind the car in the distance. The rail has a two parallel slots and screws surrounding the slots running down the rail.

What Happened To Sweden’s Slot Car EV Road?

March 1, 2023 by Navarre Bartz 60 Comments

Many EVs can charge 80% of their battery in a matter of minutes, but for some applications range anxiety and charge time are still a concern. One possible solution is an embedded electrical rail in the road like the [eRoadArlanda] that Sweden unveiled in 2016.

Overhead electrical wires like those used in trolleys have been around since the 1800s, and there have been some tests with inductive coils in the roadway, but the 2 km [eRoadArlanda] takes the concept of the slot car to the next level. The top of the rail is grounded while the live conductor is kept well underground beneath the two parallel slots. Power is only delivered when a vehicle passes over the rail with a retractable contactor, reducing danger for pedestrians, animals, and other vehicles.

One of the big advantages of this technology being in the road bed is that both passenger and commercial vehicles could use it unlike an overhead wire system that would require some seriously tall pantographs for your family car. Testing over several Swedish winters shows that the system can shed snow and ice as well as rain and other road debris.

Unfortunately, the project’s website has gone dark, and the project manager didn’t respond when we reached out for comment. If there are any readers in Sweden with an update, let us know in the comments!

We’ve covered both overhead wire and embedded inductive coil power systems here before if you’re interested in EV driving with (virtually) unlimited range.

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When One Cylinder Isn’t Enough: The Briggs And Stratton V8

February 28, 2023 by Jenny List 13 Comments

The Briggs & Stratton single cylinder sidevalve engine is one that has been in production in one form or another for over a century, and which remains one of the simplest, most reliable, and easiest to maintain internal combustion engines there is. The little single-cylinder can be found on lawnmowers and other similar machinery everywhere, so it’s rather easy to find yourself in possession of more than one. [Lyckebo Mekaniska] evidently had no shortage of them, because he’s produced a V8 engine for a small lawn tractor using eight of them. A small air-cooled V8 sidevalve is something of a unique engine to be made in the 2020s, and the series of videos is definitely worth a watch from start to finish. We’ve been keeping an eye on this build for a while now, and we’ve embedded it below the break for your entertainment.

A CAD view of the V8 engine — Clearly a lot of CAD work has gone into this build.

For an engine which uses mass-produced engines for its construction, this one still relies heavily on parts machined from first principles. The cylinder blocks, valves, pistons, and crank rods are Briggs & Stratton, the rest is made in the workshop. It’s a design with the valves on the outside — so instead of the single camshaft you might expect from experience with OHV engines nestling in the V above the camshaft it has two camshafts at the bottom of the crankcase.

The crankcase is cast in sections first, followed by the machining of the crankshaft and camshafts, then the preparation of the cylinders.. The engine is assembled with a home made alternator on its flywheel and a conventional distributor from a donor vehicle. The lubrication system is another work of the machinist’s art, and the simple straight-through exhaust system is more at home on a drag racer than a lawnmower. Finally we see it running, and it sounds the business. Most recently he’s had to deal with a seizure and a replacement cylinder, but now it’s back together and he’s working on an improved cooling system.

All in all this is one heck of a build, and we wish we had some of those skills. We’re not sure whether he’ll mow the lawn with this thing, but one thing’s for sure, lawnmower hacking has quite a past.

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Cart Cruises Abandoned California Rail

February 25, 2023 by Bryan Cockfield 20 Comments

Southern California is known for its nearly perfect year-round climate, excellent surf, and extremely high cost of living, but once you get away from the coast things are radically different. Rural California has huge tracts of land run by the Bureau of Land Management (BLM), which is publicly accessible to anyone willing to venture into the deserts. There’s not much in the way of infrastructure out there, but [Ryan] does have a unique way of traveling through it using abandoned railroad lines and this custom rail cart.

The frame of this cart is simple enough, it’s little more than 2×3 framing with a plywood deck. Some extra support is added for the motor mount and for the seating location. It uses slightly longer go-kart axles to accommodate the width of the railroad, and a small six horsepower gas engine with a single gear to power the rear axle. There are no brakes other than the riders’ shoes, and while this all seems straightforward enough the real hack here is [Ryan]’s custom wheels. He found that steel or cast wheels were not particularly comfortable on long journeys so after a few attempts he has come up with a home-built polyurethane wheel which is cast in a mold around a steel go-cart wheel and then trimmed on a lathe.

For pure exploration, there’s almost no better place to go than the American west thanks to all the public BLM land available. In this cart, you can explore long distances using an extremely low-cost method of transportation. We’ve added another video of [Ryan] exploring this area below the break to show the cart being used, too, but if you’d like a more multipurpose vehicle to use on abandoned rail near you, take a look at this bicycle which is converted to operate on the railroad.

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Bridging The Gap Between Dissimilar Road Types With Foam

February 10, 2023 by Ryan Flowers 27 Comments

When you think of driving up or down an embankment, do you ever wonder how much foam you’re currently driving on? Probably not, because it hardly seems like a suitable building material. But as explained by [Practical Engineering] in the video below the break, using an expanded material to backfill an embankment isn’t as dense as it sounds.

In many different disciplines, mating dissimilar materials can be difficult: Stretchy to Firm; Soft to Hard; Light to Heavy. It’s that last one, Light to Heavy, that is a difficult match for roadways. A bridge may be set down in bedrock, but the embankments approaching it won’t be. The result? Over time, embankment settles lower than the bridge does, causing distress for cars and motorists alike. What’s the solution?

To mitigate this, engineers have started to employ less dirty materials to build their otherwise soil based embankments. Lightweight concrete is one solution, but another is Expanded Polystyrene (EPS) foam. Its light weight makes installation simple in anything but a strong breeze, and it’s inexpensive and durable. When used properly, it can last many years and provide a stable embankment that won’t settle as far or as quickly as one made of dirt. Because as it turns out, dirt is heavy. Who knew?

Aside from roadways and bespoke aircraft, EPS foam has also been used for making home insulation. What’s your favorite use for EPS foam? Let us know in the comments below.

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Reverse Engineering British Rail Tickets

February 9, 2023 by Jenny List 21 Comments

There was a time when to take a British rail journey was to receive a ticket barely changed since Victorian times — a small cardboard rectangle printed with the destination through which the inspector on the train would punch a hole. In recent decades these were replaced by credit-card-sized thin card, and now increasingly with scanable 2D codes from an app. These caught the attention of [eta], and she set about reverse engineering their operation.

The codes themselves are Aztec barcodes, similar to a QR code but with a single central fiducial mark. At first glance they resemble the codes used by non-UK ticketing systems, but she soon found out that they don’t follow the same standard. There followed a lengthy but fascinating trail of investigation, involving app decompilation of a dodgy copy of the ticket inspector app to find public keys, and then some work with a more reputably sourced app from another ticketing company.

Along the way it revealed a surprising amount of traveler data that maybe shouldn’t be in the public domain, and raises the question as to why the ticketing standard remains proprietary. It’s well worth a read.

If you’d like more UK rail ticket hacking, it formed the subject of a talk at EMF 2022.

A white longtail cargo bike sits on grass with fenced-in planters behind it. The bike has a basket made of black metal tubes on the front and a passenger compartment behind the rider seat for children made of similar black metal tubes. A white canopy is above the passenger compartment and a solar panel sits atop the canopy.

Solar Powered E-bike Replaces Car Trips

February 7, 2023 by Navarre Bartz 20 Comments

E-bikes can replace car trips for some people, and adding a solar panel can make the fun last longer. [Luke] did some heavy modifications to his RadWagon to make it better, stronger, and faster than it was before.

The first step was replacing the stock 750 W controller with a 1500 W model to give the motor twice the power. [Luke] plans to replace the motor if it gets fried pushing too much juice, but is planning on just being careful for now. To stop this super-powered ride, he swapped the stock mechanical discs out for a hydraulic set which should be more reliable, especially when loading down this cargo bike.

On top of these performance enhancements, he also added a 50 W solar panel and maximum power point tracking (MPPT) charge controller to give the bike a potential 50% charge every day. Along with the OEM kid carrier and roof, this bike can haul kids and groceries while laughing at any hills that might come its way.

Checkout this other solar e-bike or this one making a trip around the world for more fun in the sun.