Indian Motorcycle’s Thunder Stroke 111: Built for the long run
May 20, 2013
Filed under Indian Motorcycle
Now that we’ve been introduced to the first true Indian engine in close to half a century, a moment’s reflection leads to the conclusion that it has been engineered and styled (yes, styled) almost perfectly for its intended “target” audience. A bulls-eye, if ever there was one! Even the engine’s name verges on brilliant… inspired, perhaps, by its monumental torque and (if the sound clip is any indication) its glorious noise.
This project could be seen as an exercise in one-upmanship, as well. After all, the name on the gas tank (of the eventual motorcycle) dates back to nineteen-ONE, the engine displaces ONE cubic inch more than its primary competitor’s premium offerings, and it has ONE more cam, as well. Sounds clever, but it’s the wisdom of this engine’s design that will matter more in the long run. And, make no mistake: This powerplant is built for the long run in both senses of the term. From the inside out, here are some of the reasons why:
• A massive 2” crank pin carrying side-by-side “fracture” cap-style rods of amazingly slender and strong design, which bodes well for the life of bottom-end bearings
• Modern, thin-ringed 4” bore “ashtray” pistons on tapered pins, also light and stout, preventing high loads on rods and mains
• Up top are heads whose chambers bear a striking resemblance to the successful wedge heads used so convincingly by Chevy on late-model Corvettes
• Pushrods and rocker arms are close to a “straight shot” geometry, so flex, side loads and the resulting wear and tear will be at a minimum
• The finned covers over the “down” exhaust ports, which actually function not only as effective heat sinks for hot gases, but incorporate a radius bend that flows far better than you might think
• Main bearings for the forged crank measure a bit under and a bit over 2.5”, respectively, which is probably bigger than the bearings in your car… so 200,000-mile longevity (or more) sure ain’t out of the question
• The three-lobe shock absorber built into the crank’s primary pinion means smooth drivetrain pulses and little, if any, driveline lash
• A frying pan-sized clutch with fewer, larger-diameter plates and gobs of friction material means a clutch that will easily hold back all the torque this engine can make (and then some), yet offer cooler operation and a two-finger pull
• All dog-ring shifting mechanisms in the helical cut (except first) tranny keeps end thrust under load from pressing against the shift forks (or anything else) so shifting is clean, precise and quick… without undue penalties to the gear sets and bearings
• The gear drive oil pump lives under the lowest part of the oil tank, behind the gearbox, for instant oil flow on startup and virtually no possibility of sumping or cavitation. Just one instance of a very sophisticated lubrication layout!
• If you have to have chains in an engine, this is a good way to do it; a short one driving only the intake cam directly from the crank and employing a “slipper” on the “go” side and a spring tensioner on the “back-off” side
• Maybe most importantly, this million-mile tested motor is a clean-sheet original, which does not owe one iota of its proprietary design to any other big V-twin. It makes the new Indian motorcycles it is destined to power… unique.
If those who refuse to learn from history are condemned to repeat it, those who study a storied past are impelled to re-imagine it… and improve upon it. The Thunder Stroke 111 is fair evidence of that and also shows the intent, ability, experience and insight of the custodian company (Polaris)—not to mention proving there’s no more shoestring budgets, copycat engineering or feeble future for Indian. As of right now Indian and its motorcycles will be as strong and long-lived as this engine, ready and able to assume their rightful place in the market. The Thunder Stroke 111 is the warning shot across the bow of the establishment, who should be prepared to be thunderstruck.