How to build a simple breakdown clutch for platters that free-spin during breakdown

Platters that provide backtension during the breakdown process are not too common.  Christie AW3, SPECO LP-270 and LP-280 are examples of the few that do.  If you have a Big Sky, Strong, ORC, Teco, Potts, CFS, or any kind of platter that requires you to pull the motor away from the deck for breakdown, the odds are good that you are causing damage to the films that are entrusted to your care during breakdown and may not even know it.

When films are shipped it is imperative that the roll be not only smooth, but tightly wound as well.  When rolls are shipped that are loose or not wound smoothly, by the time the film gets to it's next theater, the odds are extremely good that it will have cinch mark scratches and sprocket damage.  In fact, just the mere process of breaking down with a free-spinning platter will lay light cinch mark scratches on your films, for when it comes time to slow the platter down at the splice, the extra tension exerted during the slow-down commonly causes the film to rub against itself on the roll, causing light scratches.  This is the same kind of damage that is caused when a loosely wound reel of film is tightened by pulling on the end of the film and film slippage like this is the main cause of the little "dash" scratches that appear at the ends of reels around reel changes once a print has been "enjoyed" by a few theaters.  (Depending on the severity of the damage, after only one breakdown from a tension-less platter you may have to view the film on a well illuminated screen to be noticeable, as the darker the screen is, the more print damage will be covered up.  That doesn't change the fact that the prints are still acquiring small abrasions, and each time the film is allowed to slip due to lack of proper tension, more abrasions will occur.)  Also, when the film is unwound from the shipping reels at the next theater, the backtension during the unwinding process can scratch the film too.  Basically, platters without some form of backtension on breakdown are the cause of a lot of film damage that plagues this industry.

If you have one of these platters that does not provide a constant backtension during the breakdown process, here is a quick and easy $5 solution you can use to ensure that your theater practices "film done right".

All of the necessary supplies may be found at the Home Depot.  You will need a spring approximately 2 1/2 to 3 inches long, the two metal pieces shown (these can be found in the shelving department), a self-adhesive felt pad, a small bolt and nut 1/2" long, a 5/16" bolt (1/2" long) and someone to drill and tap a threaded 5/16" hole for each deck.  This will cost approximately $5 in supplies.

First you will need to assemble the pieces to form the clutch as shown in the first picture above.  Once you have the clutch assembled, drill and tap a threaded hole in the position noted below.  This does not have to be exact, but before the hole is drilled you should place the clutch up against the tree with the spring attached to double check the position.  The spring does not have to be stretched tightly, but it should not be at it's fully relaxed position either.  It doesn't take much tension to do the job properly.   That's all there is to it!

Following are a series of pictures showing the proper place for the tapped hole, general notes and video downloads of the clutch in operation.

This is the ideal place for the tapped hole on a Strong platter.  Approximately 1 inch from the left edge of the tree and approximately 2 1/2 to 3 inches from the top of the "MAKE UP" switch cover.

Once the clutch is mounted to the tree "finger tight" (again, make sure it can still bounce up and down a little bit), attach the bottom loop of the spring to the motor disengage handle, then disengage the motor.

You are now ready to break down.

Different angle of the clutch mounted and ready to breakdown a print.

Close up of the clutch showing the pad which rides against the outer edge of the platter.

Reverse shot of the clutch.


My apologies for not being able to shoot these with a normal video camera and distribute in a conventional QuickTime format.  These were shot as silent AVI files with a digital camera and generally require QuickTime to be played back properly, but if your computer has the proper codecs, Windows Media Player will play them back.  If after downloading it does not play on one, try the other player.

Right click the links below and select "save as" to save the files to your computer for playback.

Video showing clutch in operation (general)

Video showing close-up of clutch in operation (note the clutch bouncing up and down to track the warp in the platter)

Video showing how smooth and perfectly tight-wound the prints are when using the clutch

-Brad Miller