The first challenge was to find a long wheelbase (LWB) frame that would accommodate the tires I needed to run. The classic long wheelbase 'bent is the Easy Racers Tour Easy or Gold Rush Replica, but that design is decades old and lacked frame clearance for wider tires. Further, the company that made them had gone out of business, which took them off my list. Other LWB bikes from Lightning, Bacchetta, and a couple other makers were considered and abandoned for similar reasons.
Out of this process, a great option emerged. RANS Bikes (ransbikes.com), a recumbent bike maker based in Kansas, has been making a variety of beautifully engineered 'bents for many years. A few years ago, they decided to do a clean sheet of paper design for a new LWB 'bent that would be light, stable at all speeds, reasonably fast, and would accommodate all the recent technical advances in drivetrain and other components. The result of this effort was called the Phoenix. The Phoenix includes a number of design elements from previous RANS bikes, including using two full size 700C road wheels, and takes the classic LWB design to a new level. A few conversations with the fine folks at RANS and the frameset and some other components unique to that bike (seat, handlebars, and a few other things) was ordered.
Next came the wheelset. There's a huge number of options available when it comes to wheels. I wanted to be able to run a 40 to 45mm wide tire for both ride quality and gravel road handling. I considered carbon fiber rims, but abandoned that idea for cost and reliability reasons. Carbon rims are very light and can be built up into truly fast wheels, but good rims are really pricey and have fairly high failure rates. I'm not a light guy and recumbent riders can't "unweight" the bike over bumps, so these wheels need to be able to take a beating. Ultimately, I chose the AllRoad Pro wheelset from Mavic. Designed for cyclocross/gravel racing, they easily accommodate the tires I wanted to run, are tubeless compatible, have excellent bearings, provide for disc brakes, and are reasonably light given their mission. Done.
The decision regarding drivetrain was complex. 'Bents have historically relied on touring and mountain bike drivetrain components as they demand a wide gear range. 'Bents don't typically climb as easily as conventional bikes because the rider can't stand on the pedals and use their weight and upper body to power up hills, so the seated rider instead needs to keep the pedals spinning to get there. Touring bikes have largely been ignored in recent years as the industry has turned its attention mountain bikes and gravel/adventure bikes. Once common, the triple chainring crankset is a vanishing beast and high quality components are difficult to source. Similarly, the front derailleur needed to shift multiple chainrings is also disappearing.
The current standard in mountain bike drivetrains is a single chainring driving a wide range cassette with 10 or more gears, often referred to as a "one by" system. There are a few advantages to this approach- the elimination of the front derailleur, shifter, and chainrings makes things simpler and incrementally lighter, improved chain management, and cleaner aesthetics. One criticism leveled at such systems is that the steps between the gears can be too large, making it harder for the rider to maintain a comfortable cadence and level of effort, particularly on-road. That's valid, but it can be mitigated by having enough gears between the lowest and highest ratios.
Another emerging technical aspect of bike drivetrains is electronic shifting. Both major bike components makers, Shimano and SRAM, have had electronic shifting in their road groups for a few years. The Shimano systems, known as DI2, use small control wires to link the shifters, derailleurs, and battery. The SRAM systems are wireless. This year, SRAM released its mountain bike electronic shifting system, called Eagle AXS XX1. It's currently only available as a groupset, and includes a carbon fiber crank, a massive 10-50 tooth 12 speed cassette, a wireless shifter control, a special chain designed to run on the 12 speed cassette, and the rear derailleur with its internal servo motor and integrated battery. Coupled with a slightly larger chainring for mostly on-road use, this produces a suitably wide range of gears that allows the rider to climb at 2 mph and spin out at a top speed north of 30 mph. So I ordered it.
Brakes were also an interesting consideration. Disc brakes were a forgone conclusion, but what kind? The current standard in high performance brakes are hydraulic disc brake systems. Essentially downsized motorcycle brakes, they are very easy to use, very powerful, and provide excellent modulation. On the downside, they're much more complex, some have proven to be less than wholly reliable, and importantly they're rarely repairable roadside as that typically requires special tools that most folks (including me) wont carry while riding. While the advantages of hydraulic brakes are undeniable, there are mechanical discs that work very well indeed and in the end I went with a combination of a Single Digit lever from SRAM/Avid and Spyke calipers from TRP. The TRP calipers are interesting as they squeeze the rotor from both sides, rather than a traveling/static pad design used by others. This makes them both more powerful and easier to set up and maintain. The brake system was rounded out with some cool SRAM two-piece rotors (more rigid and better heat dissipation, but mostly they just look cool), and some Jagwire compressionless housing to keep everything connected tightly.
That covers the major decisions. Assembly and tuning are next...