At about 50,000 miles, 6000 of them mine, I sensed a vibration above 4000 rpm that hadn't been there before. I decided it was time for a look-see. Making a short story shorter, the inner main outer (sic) had gone walk-about, and was machining its way through the crankpin nut. I jaloused (look it up, but it's Scots for "half-suspected") that the vibration was initiated by crank deflection. Trevor bored and sleeved the cases for me. I bought a new crank from Simon Linford who makes his flywheels from EN 36.
Some of the problem may be that ally creeps. My muffs had slackened around my liners by about the same mileage - and the same time, 54 years. I won't pose as a "Vincent expert", but my advice to anyone who needs a rebore after 50,000 miles and 50 years, and maybe the latter is more important than the former, is, instead, buy oversize liners, have the muffs bored to restore the interference, and fit standard pistons.) And while you're at it, check that the inner main outer is still tucked up in bed where Vincent put it.
But I might argue that the fundamental cause of the problems described by Timetraveller is that Vincent cranks were NOT made from EN36, but from something closer to EN3, aka mild steel. So when mainshafts and crankpins are pressed in, the material yields, reducing the interference. Vigorous use merely accelerates what the passage of time will achieve eventually anyway. This will strike a chord for many of us. I say no more.
In answer to any protests I tell a Rudge story: George Hack was shown a beautifully restored Rudge Ulster, early 30's, cosmetically perfect, largely original parts, that went as well as it did when it left the factory 50 years before. Asked what his feelings were, he replied "if we'd known when we built them that they would last that long, we'd have used cheaper materials"
Some of the problem may be that ally creeps. My muffs had slackened around my liners by about the same mileage - and the same time, 54 years. I won't pose as a "Vincent expert", but my advice to anyone who needs a rebore after 50,000 miles and 50 years, and maybe the latter is more important than the former, is, instead, buy oversize liners, have the muffs bored to restore the interference, and fit standard pistons.) And while you're at it, check that the inner main outer is still tucked up in bed where Vincent put it.
But I might argue that the fundamental cause of the problems described by Timetraveller is that Vincent cranks were NOT made from EN36, but from something closer to EN3, aka mild steel. So when mainshafts and crankpins are pressed in, the material yields, reducing the interference. Vigorous use merely accelerates what the passage of time will achieve eventually anyway. This will strike a chord for many of us. I say no more.
In answer to any protests I tell a Rudge story: George Hack was shown a beautifully restored Rudge Ulster, early 30's, cosmetically perfect, largely original parts, that went as well as it did when it left the factory 50 years before. Asked what his feelings were, he replied "if we'd known when we built them that they would last that long, we'd have used cheaper materials"
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