New Crankpin Bushes
It is hazardous to produce crankpin bush bearing rings with an inside diameter based on the hope that the crankpin is of standard size. So many Scott cranks have crankpins that have been worn undersize by crankpin bushes that have rotated.
This has usually been caused by inaccurate little end bearings.
If the bore in the little end is inclined (as many are), the rod is forced to work at an angle.
The piston cannot tip sideways, so the rod tries to find a place on the gudgeon pin where it can align.
The big end roller bearings only function correctly if the rod stands exactly upright and squarely on the rollers.
When the rod is forced to work out of square, it tries to lock the rollers and skid round the crankpin bush.
It also causes dished roller plates and blued rollers. So much carnage for want of proper accuracy!
Alfred was totally correct --- they must be “Made to Limit Gauge”!
Back to the bushes -- We produce crankpin bushes from the highest quality through hardening bearing steel. We measure the cranks individually so that we can be sure that we establish the correct fit.
Although we are occasionally asked to provide standard bushes, we do so reluctantly because after this amount of time there are not so many standard rods !
Care must be taken to assess the condition of crankpins also.
We are not hungry to take peoples money, but, at least if we inspect and assess the relevent components, we know that the interferences / clearances we use are correct for the actual sizes and not what they are supposed to be!
Cost of crankpin bushes Hardened ,Surface ground to width, unground externally, but ground internally to leave honing for final fitting.
Price £35 each
For grinding OD and honing ID to individual big end/ crankpin figures
Price £30 each