How to repair weak takeup (GAF/Sniper)?

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MrPete
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How to repair weak takeup (GAF/Sniper)?

Post by MrPete » Tue Dec 16, 2014 6:57 pm

Hi all,

I've got one of the almost-last-round of Sniper units that Roger created. Unfortunately, they are 100% focused on Retro units, so there's no support available for us "old timers" :) [My congrats to Roger on his new line of products. They truly look wonderful!]

My projector has always had a somewhat weak takeup reel -- as a 400' reel fills up, it just gets worse and worse. And I'm pretty sure that may explain why I am getting "slips" in the capture, where the saved/lost frames "flip" (ie raw footage changes from odd-frames-good to even-frames-good and back again.)

Below is a closeup of the two rollers involved in the takeup. If I watch it in action, it is clear that this "link" is what is slipping.

My questions:
1) What could be wrong with this "link"? Is something missing, worn, needs cleaning/roughing/???
2) Is such slippage the likely cause of frame-slip?
3) Any other suggestions?

Thanks soooo much for your help! This is such a great forum...
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unsanity
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Re: How to repair weak takeup (GAF/Sniper)?

Post by unsanity » Sat Jan 03, 2015 11:51 am

I know nothing of Gaf/Sniper but from the look of the photo I would certainly start with a good cleaning. I would use iso-propyl alcohol to get rid of any fat or oil traces.
Good luck !

Julian.

supa8
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Re: How to repair weak takeup (GAF/Sniper)?

Post by supa8 » Sat Jan 03, 2015 3:25 pm

Definitely cleaning with some isopronol will help.
Mine was a bit too harsh, so Roger had recommended lightly sanding down the white roller with some fine grit sandpaper.
Maybe you could look at 3d printers and printing that part again, in case it isn't exactly as round anymore.
I'm not even sure whether these parts are from the old gafs. I would say they were custom made by Moviestuff.

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MovieStuff
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Re: How to repair weak takeup (GAF/Sniper)?

Post by MovieStuff » Sat Jan 03, 2015 4:25 pm

The thing to remember about the take up reel is that it's main job is to keep the film from spilling onto the floor. It does not really play a part in advancing the film through the projector other than to clear the film path. The main parts of the take up are

Green Arrow: Slip Clutch Roller
Blue Arrow: Slip Clutch Pulley
Red Arrow: Receive Disc

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The Slip Clutch is mounted on a spring loaded rocker arm that presses the white slip clutch roller against the black receiver disc, which is on the back side of the take up reel spindle. If too much pressure is applied, then the take up reel will pull prematurely and affect registration at the gate. If the pressure is too little, then slack will be created and the film will eventually spill onto the floor.

The original GAF slip clutch had a rubber grommet that wore out rather quickly, even when new 35+ years ago. So used projectors had grommets that were dry rotted and cracked. We replaced them with a machined slip clutch made out of Delron, which is a tough industrial plastic. Over time, the rubbing action against the receiver disc can do two things: 1) Cause a depression or groove in the white roller the width of the receive disc and 2) Cause a wax build up on the outer edge of the receiver disc. The depression means that the back edge of the receiver disc can sometimes catch on the edge of the depression which can cause too much transfer of power because it can no longer "slip" (resulting in an aggressive take up reel) or the receiver disc can ride up on the edge of the depression and cause a lack of contact which reduces the transfer of power (thus creating a weak take up reel).

For proper tension, you need to do a couple of things.

A) Use some fine grain sand paper and wrap it around the roller part of the white slip clutch roller and turn it repeatedly until the surface of the roller part is smooth with no discernible depression. It should be the same diameter from the outer edge of the roller to where it meets the slip clutch pulley.

B) Use an exact-o knife with a new blade and lay it flat on the outer edge of the black receiver disc. There is actually a notch in the chassis above the receiver disc to accommodate this procedure. Turn the disc and slowly skim off any waxy build up. Be sure not to dig into the plastic. Keep the blade flat. Then follow up with sand paper to smooth out the edge of the slip clutch.

C) Use alcohol to clean all the surfaces including the groove of the white slip clutch pulley.

D) Replace the belt that drives the white slip clutch assembly making sure to clean the groove of any debris that has collected over time and make sure that the belt is in the bottom of the groove and has not slipped out.

If you follow these procedures, you should restore proper tension to the slip clutch assembly. If it appears to pull too much, you can put some stretch in the spring that applies the pressure to the slip clutch. If it appears to pull too little still, then you can shorten the spring a bit and reattach.

Hope this helps!

Roger

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MrPete
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Re: How to repair weak takeup (GAF/Sniper)?

Post by MrPete » Sat Jan 03, 2015 11:12 pm

VERY helpful, Roger! Thanks sooo much.

As you move onward, if you are willing it would be incredibly helpful to your thousands of "old" customers to have an online cache somewhere of repair / tuneup / alignment / timing procedures and workflows for your old / no-longer-supported products. You and your team have such an incredible wealth of knowledge about your products... it would be sad for that all to disappear as you refocus on new things.

I would be happy to assist with this in any way I can, from digitizing documents to creating an appropriate archival website.

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