Homer: enduro metal motorbike with single-turn gearbox with 27.5-inch wheels

Homer: enduro metal motorbike with single-turn gearbox with 27.5-inch wheels
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Particular Irish man Rory Byrne has designed the system you see in entrance of you – a metal, single-turn enduro bike with a stroke of 180 mm, which is pushed by a belt drive. There’s additionally an inverted double crown fork and 27.5-inch wheels on each ends as a result of that’s precisely what he needs. It’s not simply leftovers floating across the storage.

Rory doesn’t squat relating to driving on something with two wheels. He rode and rode a wide range of bicycles, some with motors and a few with small wheels and with out gears. Having spent years on a BMX that requires most precision for driving, Rory needed a severely succesful mountain bike to supply the identical response and sturdiness as his 20-inch motorbike. put your cash the place it’s in your mouth and again off.

With the assistance of their cousin Stephen Byrne, they got down to create the proper motorbike that was nowhere else. Stephen owns and operates a metal body firm in Dublin, Eire, known as The Freedom Machine, the place after regular enterprise hours he sat right down to manufacture and assemble the body.

The creation of “Homer” shouldn’t be one thing as mainstream as Specialised Stumpjumper, a motorcycle beforehand owned by Rory. Each facet of this motorbike, from the elements and geometry to the tubes and the situation of the shock absorbers, has been totally questioned. His calls for have been fast management and response to physique actions, however he additionally wanted stability and traction.

This often means 29-inch wheels, lengthy chain feathers, a lot of sagging and progressive suspension, and delicate tires for traction. What does Rory favor? At the least 30 kilos per sq. foot in each 27.5-inch DH tires and strong suspension. The 29ers acquired uninterested in him and “killed the enjoyable”. He drew an amazing parallel for me: the 29ers are 27.5 inches, which is a soar on a 26-inch motorbike in opposition to the BMX. “Horses for programs,” he added.

With a top of 184 cm and a weight of 72 kg, he selected pretty frequent figures reminiscent of 475 mm attain, 1250 mm wheelbase, 79º seat tube angle, 30 mm drop BB and chain feathers which are evenly spaced in three positions between 420-445 mm rising lower than 420-445 mm9. . This gives him a bicycle that’s planted whereas resting, however has the power to return to life when ordered to go away the land.

It will appear that the slim flanges of the Hope 135×12 mm hub are literally nearly 10 mm wider than the favored 148 Enhance hubs, as well as it makes use of bolts with a lining on the axis the place the washers enter the spherical grooves to forestall slipping wheel within the fall. One small late thought was the sliding drop, however it had a hard and fast brake mount. Compensating the overlap of the brake pads and rotor with an adjustable chain size meant that to beat this they would wish to weld the caliper mounts within the middle slot and use beveled washers that have been used to compensate for the distinction in caliper clock heights.


Transferring on to adjusting the suspension, the smaller particulars change into fascinating. Even with such excessive tire strain, Rory usually rides on a 525-pound spring, which squats solely 25% on a single-hinge body design. The only hinge shouldn’t be fully linear and will increase by 8% because of the angular association of the shock absorber. This is sufficient to soften the curler in the course of the 180 mm stroke, 14 of which strikes the axle again, whereas the hydraulic resistance of the decrease a part of the EXT Storia takes care of essentially the most tough landings.

Ten-year-old Manitou Dorado fell in love and decreased the stroke to 180 mm. The primary and ramp chambers are mounted on a 72/130 PSI that has a rod size of 35mm when it’s put in to carry a excessive bar. The offset is customary at 49 mm, however there are additionally shorter crowns to order.


One concern that does not come to Rory’s thoughts is bending. The decrease tube is a Reynolds 851, straight caliber 1.2 mm thick and 38 mm in diameter, and the lighter higher tube 35 mm produce a strong however vibration-absorbing entrance finish. The rear 19mm feathers and 16mm seat feathers have a thickness of 0.9mm 4130 for this suitable experience. All turning gear is CNC machined with 4140, 316 chrome steel compartments and TIG welded to 4130 hoods. On the transmission, the idle adapter and belt tensioner are fabricated from 6082 T6 aluminum by Steamer Industries.

By lifting and forming the rear triangle right into a wider bridge, he was ready to withstand an excessive amount of twisting, however famous that he might add a jumper for the seat if a smaller match was desired. In truth, he preaches that the chassis of the USD fork and spherical bushings within the shock-absorbing eyelets – that is what permits the suspension to actively observe bends and chattering path. The forgiveness of the body and suspension could also be simply one of many explanation why Rory can work with such excessive tire strain and inflexible suspension. Critical bike driving expertise in all probability gained’t damage both.

The medium-high flip gives 114% anti-squat all through the journey as a result of idle placement, which additionally reduces the quantity of belt progress. It’s believed that the anti-rise on the excessive facet of 100% can really feel sharp when braking, as it will probably compress the suspension. The anti-lift of the Homer motorbike begins at 118% (110% at deflection) and drops to solely 88% at full velocity, which helps preserve the geometry of the motorbike when braking – a principle taken from Moto GP. Rory says he has by no means skilled adverse efficiency from this characteristic, and chooses his braking factors on clean components of the path if he can.


Silence is one other attribute that’s valued after driving a BMX bike. Tight chain and fewer transferring components not solely means fewer bugs but in addition nothing bounces on the bike. One technique to handle all this noise on a mountain bike is to first get rid of the change, in the end reducing the unsprung mass by transferring the load from the pendulum to the primary body. Second is the substitute of the chain on the belt. Rory was so uninterested in continuously adjusting the twelve-speed switches due to the precision wanted for excellent operation that he bent over and was bitten by a high-resistance bullet that comes with the gearbox.

On the coronary heart of the beast is the Pinion C1.9XR, which makes use of a variety of 568% of 9 gears by way of a rotary knob change – one other unconventional half on the Homer. The rear cog is a chrome steel Pinion Gates 39T together with a 19-tooth cog positioned just under the pendulum hinge. When soldering the axle for the fridge on to the body there have been fewer alignment issues to fret about, and Rory had but to see the necessity for a belt information at each ends.

One other bonus of the gearbox is the power to shift with out pedals, and because the free hub is positioned on the mainframe, Rory says it really works equally to the O-chain to facilitate pedal recoil.

Rory mentioned he was amazed at how excessive he might soar on a 180mm bike that’s not gentle weight and has a balanced ratio of entrance and rear unsprung wheels in addition to quick chains. It’s not essentially the most environment friendly bike that pedals with heavy tires holding it again, however it additionally doesn’t chase or hunt for Strava KOM. The main focus is on the descent and full management.

So what’s subsequent for, visually, essentially the most unlikely mountain bike that BMXer will experience, not to mention create from scratch? The usual 49mm fork crowns will probably be changed by a a lot shorter, customized equipment, and the identical goes for connecting rods. These 175 mm lengthy gears will probably be changed by 155 mm to compensate for the low BB top. And if I’ve to make additional assumptions, Rory will proceed to tune Homer and ship large gaps. In some way I believe it should steer clear of 29-inch wheels and switches.

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