RevGrip Spider Legs Backwards?

[doug tenney]

Did Horstman make some RevGrips with the spider legs facing forward??  See 3 pics.

We run mostly RevGrips on our McCullochs (tapered shaft).  Most have inboard sprockets.  In all cases, the four "arms" on the hub (aka "spider") point in the direction opposite the engine rotation.  Makes sense... as RPM increases, and the shoes contact the drum, the back-sloped "arms" acts like ramps, helping the shoes to "dig into" the clutch drum, thereby keeping them from burning up.

(Same idea as the familiar leading shoe in a drum brake setup.)

HOWEVER, I recently picked up a RevGrip that has the arms pointed forward, i.e., in the same direction as the engine rotation.

What the heck am I missing?

The spider also has some peculiar geometry on its outboard edge, which I believe is for starting off of a pulley on the end of the crank.  (I didn't get any pulley or nut with this clutch.)

[Mark Loraine]

Left hand motor application?

[ted johnson]

Mark, I could see that for a West Bend, but not for a Mac. All my West Bend Horstmans have "trailing" arms, but they probably made opposite arms for left side engines. Ted

[doug tenney]

Mystery solved.
Mark Loraine was correct.
Of course, that was always the obvious answer (clutch is for a CCW motor), but I didn't know of any such motor with a tapered PTO.
Oreville's Karting Genius & Curmudgeon in Residence (don't tell him, head already too big ) took one look and said that some foreign motors spin CCW.
(He also showed me that the spider sets too far down a Mc91x crank, not leaving enough room for the clutch drum.  Duh, I missed that.)

Ok, foreign motor.  Problem with that theory: hub wouldn't fit over metric (10mm) threads.  Hole is just big enough for 3/8", like a Mac.

Another one of my karting heros, with initials T.I., completed the puzzle.  Turns out these CCW-spinning foreign motors were sometimes outfitted with extension shafts that had Mac taper and 3/8 threads.  His guys experimented using these opposite-facing spiders on CW motors but, as they expected, the engagement characteristics were erratic.

Now, onto the next mystery... contemplating my navel.

[ted johnson]

Mystery solved.
Mark Loraine was correct.
Of course, that was always the obvious answer (clutch is for a CCW motor), but I didn't know of any such motor with a tapered PTO.
Oreville's Karting Genius & Curmudgeon in Residence (don't tell him, head already too big ) took one look and said that some foreign motors spin CCW.
(He also showed me that the spider sets too far down a Mc91x crank, not leaving enough room for the clutch drum.  Duh, I missed that.)

Ok, foreign motor.  Problem with that theory: hub wouldn't fit over metric (10mm) threads.  Hole is just big enough for 3/8", like a Mac.

Another one of my karting heros, with initials T.I., completed the puzzle.  Turns out these CCW-spinning foreign motors were sometimes outfitted with extension shafts that had Mac taper and 3/8 threads.  His guys experimented using these opposite-facing spiders on CW motors but, as they expected, the engagement characteristics were erratic.

Now, onto the next mystery... contemplating my navel.

Which direction does THAT face? TJ

[doug tenney]

Inward.  A lot.  Between first and second knuckle.