My understanding of wheel taper (And I may be full of B.S., but this is what
I have read) is to allow trains to navigate curves without excessive wheel
slip. As centrifugal force causes the wheel set to move to the outside of the
curve the larger diameter of the tread is contacting the rail on the larger
diameter, while the inner wheel is riding on its smaller diameter. This
lessens wheel slip and I presume that on 1=1 scale (full size) that railroads
set
minimum curve radius to suit on mainline practice. Look at the steep taper on
a Lionel 027 wheel compared to the slight taper on a fine scale wheel.
I have two kinds of wheels on my 3.5 gauge stuff, one set has each wheel
with a brass bushing so the wheels can rotate independent of what his brother
on
the other end of the axle is doing. The other sets of wheels each wheel is
press fitted on the axle so where "Righty" goes, "Lefty" must follow along.
Next time I am out at the shop will check and see if either, both or which
ever
has taper and which don't. I have seen no difference in the wheel sets to
stay on the track over my 20' radius curves.
Of course on a rod driven locomotive the wheels must be secured to each axle
to keep the valve gear working properly.
On my lathe (Sear's Atlas, 12 inch) I have no problem turning the slight 3
degree taper by setting over the compound to three degrees. Or it could be done
by a file on our small wheels with a template to see where we are in the
process. The wheels must be made to the same diameter, coned or flat within as
close a limit as you can manage so both sides work the same. What I have done
and seen recommended is to "rough" turn all your wheels first, then set up to
finish each wheel at the same settings on your cross slide and compound.
When I have done cast iron wheels I use a carbide bit to dig under the cast
iron
"skin" then when all wheels in the set are rough turned leaving a few thous
for finishing change to a HSS tool with the root radius between tread and
flange ground in. Then set up a mandrel to take each wheel running true on its
axis and take off the final few thous and put in the taper and touch the outer
rim with a file to just barely round it over. Also use a file to radius the
top of the flange, but I don't think that is too important, but I presume a
special ground tool or jig would do that more evenly.
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