anvilfire logo (c) 1998 by Patrick Dempsey
anvilfire! News
Reporting LIVE! from Asheville, NC - June 1998!
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JYH-1  JYH-2  JYH-3  JYH-4  JYH-5  JYH-6
The U-joint flange above is one of those really ugly parts that makes you wonder, "How am I going to attach to that?". Well, I lucked out as the second photo shows. The engine pulley covers the ugly U-joint yoke AND provides two possible pulley diameters! All that will be necessary is to carefully layout and drill four holes. Don't tell the Ford pulley its going to be bolted to a Chevrolet!

Reverse Engineering:

Been working on that for a day or so. The subject of measurements and nominals needs to be discussed. Our "reverse engineering" for the JYH consists mostly of measurements. When measuring existing machinery it helps to know what system of measurements was used to design the equipment and what kind of dimensions the original designer used. On the 1973 American auto rear axle all the dimensions have come out nominal fractional inches. Even things with tight tolerances like the wheel pilot are fractional (3.625") There is nothing unusual about this except it is not unusual to come across equipment designed in decimal inches. Then everything comes out in tenths (0.1") and half tenths (0.05").

If you are dealing with metric system hardware the dimensions should come out nominal metric. That is, even units. However, there are places where you can get tripped if you rely on "eye balling" something and rounding to the nearest unit. The U-joint yoke above was probably designed by Spicer. Spicer has sold U-joints and components all over the world. It is not unusual to find inch dimension parts like this on an otherwise all metric product.

Bearings are another place that can trip you. Inch series bearings are still common. However, the bearing industry was one of the first to go fully metric and provided a wide range of bearings in this country long before it became popular the convert to metric. It is not unusual to find an inch shaft turned down to a metric dimension to provide a shoulder for the bearing while supporting a gear or pulley with an inch bore! Just something to think about while measuring your parts. . . . Drawings! JYH p.3

May 12th, 1998
Copyright ©1998 Jock Dempsey