Motorcycles

Meet the Birdcage Boxer, featuring a titanium lattice frame and a mystery BMW motor

Like a skeletal ghost bike, Revival's Birdcage is built around a mystery motor that heralds a new long-stroke BMW engine platform
Like a skeletal ghost bike, Revival's Birdcage is built around a mystery motor that heralds a new long-stroke BMW engine platform
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Like a skeletal ghost bike, Revival's Birdcage is built around a mystery motor that heralds a new long-stroke BMW engine platform
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Like a skeletal ghost bike, Revival's Birdcage is built around a mystery motor that heralds a new long-stroke BMW engine platform
The tubular lattice frame comprises no less than 134 9mm titanium rods
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The tubular lattice frame comprises no less than 134 9mm titanium rods
Birdcage is built for this year's Handmade show in Austin, Texas
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Birdcage is built for this year's Handmade show in Austin, Texas
Rear brake and rigidly mounted axle
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Rear brake and rigidly mounted axle
Suicide gearshift
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Suicide gearshift
Aerodynamically shaped engine covers - this thing is built to run on the salt flats
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Aerodynamically shaped engine covers - this thing is built to run on the salt flats
Single front monoshock
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Single front monoshock
Front suspension wishbone and linkages
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Front suspension wishbone and linkages
The best look we can get at the colossal BMW boxer engine at the heart of the Birdcage
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The best look we can get at the colossal BMW boxer engine at the heart of the Birdcage

Two wheels, a seat, a big ol' motor and the absolute bare minimum of other stuff supporting them. The Birdcage uses 134 nine-millimeter titanium rods to create a surreal see-through lattice frame on one of the most spectacular custom BMWs we've seen to date – and the motor presents a bit of a mystery.

Inspired by the Maserati Tipo 61 Birdcage, a 1960s-era race car with an incredibly intricate space frame tube chassis, Alan Stulberg and the team at Revival Cycles has built a total eye-popper for this year's Handbuilt show in Austin, Texas.

Looking like some kind of skeletal ghost bike, it's built around a big boxer engine, hidden behind podracer-style aluminum covers that the team knocked up with a little assistance from expert metalworker Craig Rodsmith on a three-day visit to Revival. That hulking boxer is much, much bigger that anything you'll find in a BMW showroom – indeed this entire custom may best be viewed as a teaser for a new large-capacity BMW boxer engine and streetbike series.

The best look we can get at the colossal BMW boxer engine at the heart of the Birdcage
The best look we can get at the colossal BMW boxer engine at the heart of the Birdcage

All that's obvious at this stage is that it has staggered cylinders, the left leading the front by a couple of inches, with cooling fins, a new type of differential drive, and that those cylinders are enormous and quite long, indicating a torquey, cruisy style of power delivery. Could we be looking at a 2,000cc heritage cruiser motor here? Time will tell.

To call the Birdcage clean and minimal is to undersell it. There's no headlight, dash, front brakes, radiator, mirrors or visible fuel tank. Gearshifting appears to happen via a suicide hand shift on the right hand side of the bike, with a single reversed lever on the droopy left handlebar controlling the clutch and ... we can't see, but possibly a brake pedal on the left foot, which is where you'd stick it if you wanted to keep it as close as possible to the caliper and reduce ugly hydraulic lines. Any electronics are entirely hidden, and the thin throttle and clutch cables are really the only "plumbing" we can see in these photos.

The tubular lattice frame comprises no less than 134 9mm titanium rods
The tubular lattice frame comprises no less than 134 9mm titanium rods

The front suspension is a pair of custom aerodynamically covered forks with a telelever-esque brace going back to the engine mounts and a single monoshock. The rear looks like a hardtail setup, but rear suspension is listed as a custom "pinion" design. Perhaps the axle is free to move up and down on a gear inside that rigidly mounted rear hub, with the drive shaft pivoting to meet it – the brake caliper is mounted in such a way as to potentially allow a little vertical disc travel. Either way, we've pored over a ton of build pictures at the Revival website and found nothing to suggest how the rear wheel might move up and down.

Aerodynamically shaped engine covers - this thing is built to run on the salt flats
Aerodynamically shaped engine covers - this thing is built to run on the salt flats

The seat? Probably not that great for an Ironbutt attempt; it's a small, rigidly mounted metal platform. But that's OK, Revival designed this thing to be more of a land speed style machine anyway ... and actually plans to run it on the salt. Yikes. It might not end up being much of a rider, but it's a heck of a looker - and we just love the structural elegance of that titanium frame. Very cool.

Source: BMW & Revival Cycles via BikeEXIF

7 comments
Expanded Viewpoint
The welds sure do leave a lot to be desired. And that hard tail is going to be murder on any rider, seeing how little cushioning there will be from that thin ribbon or a side wall rear tire. But on a drag strip or salt flat, it should be quite the rocket ride!! Randy
flyerfly
Those handles...it looks like with angle your body would be at if you loosen your grip just for a second you would bang your chin on the top of the forks...Does not look comfy or ergonomic in the least to me.
Bill Bennett
Where is the fuel tank?
BeinThayer
Those are some phenomenally ugly welds. Titanium is not forgiving of poor handling during welding. The end result can easily end up be a joint that fails catastrophically via brittle fracture. Not a good way to have a trip end.
Matt_House
This makes me sad. The design of this bike is such that it's not good for racing, as it lacks the needed safety equipment for any sort of racing, even old school salt flat racing, Most notably the lack of a proper suspension, and a braking system that could only be described as 'vestigial', renders this thing unfit to race. The lack of any lights, fuel tank of any size, gauges, or seat renders this thing unfit for street riding as well. I confess that it would seem that someone spent a great deal of time and money to make a motorcycle that is only fit to look at.
Martin Hone
At least it has provoked some interest, but raises questions as well, such as why titanium rods, why not tubing ? The reason the cylinders are offset is due to the crank having separate and offset throws, unless you have a knife and fork style con-rod and big end bearing ( ie Harley and R-R Merlin V12 ) on the one crank pin...
Gannet
Wonderful! I love the insane creativity of these Revival peeps. But, why is BM bringing in a new petrol engine when the future is electric ?