Film-Tech Forum ARCHIVE: Simplex Intermittent Pad Shoe q.

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Posted by Rick Long (Member # 213) on 08-31-2003, 11:58 PM:

It appears like the same item, although with different part numbers. Known as S-1511 on the Standard and Super Simplex, R-316-E on the E-7's, P-3291 on the 1060's, this outer intermittent pad shoe has the same purpose on all machines. It, coupled with an inner pad shoe (one set for each for each side of the sprocket) holds the film onto the intermittent sprocket.

At first the outer shoe appears to be symmetrical, but on closer examination, one notices that one of the ends has a definite "point" to it.

All manuals show this point to be on the "outgoing" side of the sprocket (furthest away from the gate). Obviously, this gives a better purchase at this point on the sprocket.

My question is, why is this not symetrical?

I am not finding all of our machines the same in this respect.

[ 09-01-2003, 12:00 AM: Message edited by: Rick Long ]

Posted by Paul G. Thompson (Member # 655) on 09-01-2003, 12:26 AM:

I think that is because it will allow the film to release itself from the sprocket teeth a little easier. Just a guess....

Posted by Steve Guttag (Member # 268) on 09-01-2003, 09:13 AM:

The dynamics of the film entering and leaving the sprocket are not the same. The pointy side provides a greater wrap, as you noted, it also helps push the film back to form the lower loop and finally, it keeps the film off of the the support tang for the intermittent shoe. I'd be willing to wager it was the last reason that it was orginally formed with a pointy side.

Conversely, you don't want the shoe to have any affect on the film entering the sprocket..just to hold it to the sprocket. Any force to the film between the gate and intermittent sprocket will show up as vertical instability unless it is held rigid (the shoe is held by a spring...not ridgid). Some projectors actually frame by pushing against the film as it leaves the gate!

Steve

Posted by Rick Long (Member # 213) on 09-01-2003, 07:32 PM:

Excellent analysis, thank you Steve and Paul.