There are several different set ups for The 2/4 min mechanism. The first is the factory installed, as in the "D" models, These are shifted using your finger nail while the machine is running. The second type is the Conversion package, Which was offered by the factory to up grade the 2 min. machines, These are shifted by means of a change lever (selector), that is used while the machine is running, and there is no center bearing. Of the two types there are specialized parts used only on specific models. The Lead screws are different for Home "B", "C", "D", and Triumph "B", "C", "D". the Pulley and Clutch are also Model specific. There are several mandrel shaft lengths, and these are not marked. The point being, Don't mix parts in the 2/4 Mechanism. The critical Parts are stamped with "T" for Triumph and "H" for Home, as well as the model letter, i.e. "D", except the mandrel shafts, these vary in length.
1) First the parts, the parts listed and shown above are basically all of the mechanism that changes tracking speed. Yes the mandrel and record will travel the same speed on both 2 and 4 minute positions, only the speed of the lead screw changes, i.e. the tracking speed of the carriage. Of the parts shown, only one, the Selector will not be used in both factory 2/4, and conversions.
The following describes factory mechanisms,
But all but the shifting and center bearing are the same.
2) The mandrel shaft passes thru the center bearing, the lead screw is locked into the thrust collar by the stop,( an "L" shaped piece bolted to the Thrust collar) engaging the groove in the end of the lead screw. The mandrel shaft passes into the thrust collar and lead screw, coming to the pins at the end of the lead screw. The pins and the slots on the clutch are engaged (This is what turns the lead screw), the shaft goes into the clutch, and into the pulley and into the geared end bearing.
That is the alignment of the parts, the spacing is set as described next.
3) Most mandrel shafts have a positioning dimple that the thrust collar set screw will set into (its sometimes hard to find). Once set the thrust collar sets the basis for alignment.
Next we need to set the detent for the clutch. The clutch has a small pin that is held down by a small leaf, pin spring, this is what engages the grooves around the mandrel shaft. Loosen the pulley set screw, Position the clutch into the pulley with its slot up where you may see the detent grooves on the mandrel shaft. Position the pulley and clutch where the pins on the Lead screw are just in the the slots, watch the pin spring as you position the clutch, stop when the spring goes down, hold that position and snug up the pulley set screw ( not tight ). using the rim, move the clutch toward the mandrel (4 min position) and feel for the latch into the detent groove.
4) Move the clutch back and forth carefully as you may damage the internal gears if the mandrel is not turning. If you feel the detent on both the 2 min. and the 4 min. positions, and you see the pin spring rise and fall as the pin falls into the groove, tighten the set screws (not overly). Reinstall the belt and give it a go. Sometimes it may take a few times to get the alignment right.
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