Quote:
Originally Posted by LEADERS EDGE
So you feel like the Esslingers toyotas and such are of poor quality? They just randomly assemble parts with no research and development? I've got nothing against the Focus HPD series.....just don't tell me they don't have engine problems from time to time. Same with cycle engines
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leader
By no means are they low quality, but the manufactures have the resources to achieve a very precise tolerance. They are on the leading edge of developing equipment and techniques for achieving these very precise tolerances and finish only dreamed about by the engine builders. Most engine builders are now using a profilometer to check surface finish. The manufactures have been using them for decades.
I am pretty familiar with modern day motorcycle engines. Each bearing in one of those little engines is fitted to its particular journal, and bearing bore size. Using main bearing specifications as an example.
The acceptable main bearing clearance is .0004 inches to .0014 inches. A human hair will lock the bearing up.
The tolerance on the main bearing journal is 1.3773 inches to 1.3780 inches
.0007" under and the crank is junk they don't have undersize bearings so to speak. Each journal is measured and size noted on the crankshaft next to that journal.
They also measure each individual main bearing bore. The tolerance is from 1.4961 smallest to 1.4967 largest and mark each main bearing bore accordingly. .0006" and the block is junk.
To put it all together if each part is in specification the manufacture offers 3 sizes of main bearings sized by the bearing's thickness.
Brown the thinnest at>>> (0.05870 to 0.05886)
Black at the middle >>>>(0.05886 to 0.05902)
Blue the thickest>>>>>> (0.05902 to 0.05917)
When I started out we would almost call these numbers interference fits, but because of more precise machine work and the invent of micro-finishing these are running tolerances.
In the old days if you erred you erred in the favor of loose in modern engines you shoot for tight. In the old days you compensated with oil viscosity. Today that is not a good idea. The use of engine heaters is to try to get the operating clearances to open up just a little because of inaccuracy in machining and trying to keep the clearance as tight as possible.
The newer small automotive motors are also going to selective fit on their bearings.
Does Esslinger or anyone else offer main bearings in three specific sizes with a total difference in bore between the largest and smallest of .00064 inches (64/100,000 inch)? Some bearing manufactures do offer a .001" (100/100,000 inch) undersize bearing and then .010" through maybe .040" undersize.
Their are guys out there that can do produce tolerance numbers like these in limited and small numbers (= Very Expensive) but the manufactures produce these numbers thousands of times every day.
Honest Dad himself
