[modeleng] Someone has to do it . . . . .
- From: Harry Wade <hww@xxxxxxxx>
- To: modeleng@xxxxxxxxxxxxx
- Date: Fri, 25 Mar 2005 19:20:25 -0600
OK I'll break the silence. I am in the midst of turning the
drivers for a redesigned 7.5"ga TICH. The drivers are 5"OD rather than the
4-1/8" called for in the orginal design (one aspect of the redesign) the
ones I'm using are old-stock BRIDGET drivers from Reeves. Aside from
several chilled areas in the skin which have been deeper than expected, the
iron is very good and I've encountered no flaws. I rough turn using cheap
brazed carbide bits but always finish with a razor-sharp HHS spoon bit.
Two comments about the patternmaking, . . . first there was not
enough material left protruding at the face of the rim to produce a
distinct line between the the tire and the spoked center so I'll have to
turn a step or something there and then do a littel filing to fair this
out. Secondly, when laying out the spokes whoever made the pattern drew
their spoke guidlines radially from the center point of the wheel producing
spokes that taper slightly TOWARD the hub rather than tapering away from
the hub. Not good, but not bad looking enough to discard the wheels.
To date the wheels have been rough-turned, finished back, and
bored for axles. Next they'll be bolted to the faceplate and finished
front. After broaching for keys the wheels will be returned to the
faceplate and offset by indicating an offset jig and the crankpin holes bored.
My return cranks (for Walschearts) be broached square and the main
crankpins will be milled with square ends. In order to eliminate the
problem of pressing these home at precisely the correct angle and identical
side to side, I am going to try an idea I saw in ME many years ago. The
main crankpin ends and their bores will be turned with a 6 degr taper
(approximately a Morse #2) and then have an inside-end drawbolt fitted.
The return cranks can then be installed and adjustments in crank angle can
be made by rotating the entire crankpin and when exact crank angle has been
determined lock it with the drawbolt.
Regards,
Harry Wade
Nashville Tennessee
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