Small End Bushes.txt
I copy my operation sheet for your general interest
Small End
Phosphor Bronze from EMAM is 27 OD x 12 bore as A4358
rough to 21mm od x 67 lg x 19/32 drill bore but watch that rough bore is true.
This blank makes two bushes. Hold in 21mm collet to produce first bush, hold on
first bush to make second bush, then part off, face and chamfer.
check internal bore as this is always marginal on boring
Nom bore in rod 0.8125"
Hone out to give 85% clean up
Turn bronze bush blank +0.0015 / 0.0020" OD
Bronze bush rough bore 0.593" = 19/32" drill
Length = Rod width + 1.4mm
Chamfer ends + bores
Turn lead Rod bore - 0.0005" x 1.5mm
Push in rod
Mill cutout + ( side oil reliefs for racing)
Drill + Tap 2BA for security screw (Racing)
Loctite in 2BA brass cheese head screw flush to inside of bush blank (Racing)
Bore to 0.6245" dia on jig to correct centre distance
Internal oil grooves on racing engines by hand.(Racing)
Hone to loose SF on gudgeon pin 0.6262 / 0.6265" dia
Cut off brass screw (Racing)
I do realise that my methods are perhaps more "particular" than normal, but I
have made many machines for car factories and note the tolerances specified. The
reliability of Japanese products is, to a large extent, a result of accuracy of
manufacture.
I am not looking for work and if you do not have the facilities, perhaps a local
engineering shop or good model engineer can help.
Whatever you do, I do urge you to be sure that you have accuracy within two thou
in parallel and twist. I aim for one thou.
I would strongly recommend that you do not resort to the trick of putting in the
hole and then bending and twisting the rod till it seems to have alignment. The
rod usually "Unwinds" in service and reverts to its unstressed attitude. A rod
that has been running will have settled into its natural attitude and will not
move again in normal use. It therefore follows that the hole should be put in
correctly first time.
An engine with rods in good alignment will give a good service life.
Alfred Scott knew exactly what he was talking about when he chose the logo "Made
to limit gauge" Of all the components in this deceptively simple engine, the rod
little end to big end alignment is by far the most crucial.
Kindest Regards and Happy Christmas
Roger Moss
_________________
Rebuilding and upgrading of Scott and Silk power and transmission units. New
enhanced replica Scott engines. Special manufacture Scott technical info at our
website
Moss Engineering
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