Film-Tech Forum ARCHIVE: Kelmar rewind table/bench???

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Posted by Ben LaCrosse (Member # 4662) on 05-20-2008, 04:30 AM:

Kelmar Rewind Table. Series?? Manual-wise it looks like the 8000, i can't remember though.

What to adjust the clutch to? I think our rewind table needs tweaking. Any speed faster than 40%, the film will jump around towards the end of a reel. It's like the motor is pulling faster than the clutch will allow. The clutch side reel will even vibrate. I think this even caused a scratch on Narnia.

Is this typical, though? Shouldn't you be able to maintain a speed of even 50% with a relatively calm rewind?

p.s. what about the auto shutoff arms... yea/nea.. i ran a search on this but didn't succeed.

Posted by Dave Macaulay (Member # 813) on 05-20-2008, 10:13 PM:

There's no exact specification. How would you measure it?
You want a setting that leaves a properly wound reel.
The only definition of correct tension that I've heard is "not too tight and not too loose". Too loose is easy, the film roll flops around or you can easily slide sections of the roll side to side. Too tight is harder, the roll should be firm but not hard like wood.
Too loose or too tight will cause more cinch mark scratching than "just right" although any rewinding will cause this. Cinch marks show as little vertical scratches throughout the print but worst near head and tail. The roll tightens after being wound, sliding one layer against the next. Any dust or dirt makes those scratches. Too loose and the roll cinches when you play it or rewind it again. Too tight and it cinches during the tight rewinding.
For high speed rewinding (I consider this abuse of the print) you want slightly lower tension than for slower work. Near the end of a reel at high speed the supply reel will be at a very high RPM and the air drag will add quite a bit of drag. Since the fixed clutch torque also applies more tension from the small diameter supply roll you get cinching on the inner turns of the takeup roll.
The autostop arm controls the film and helps lay it down in a smooth puck on your takeup. This avoids raised turns which are prone to edge damage. You should be especially careful to leave a smooth roll on prints for shipping. In a changeover house the best pack for shipping comes from running the last show onto the shipping reels. This pisses off the next platter house guy that gets the print, but the film won't have been edge damaged in shipping.
It also depends on the reel size. There is no way anyone should be going at full speed making up shipping reels onto a 6000' intermediate reel. Platic shipping reel flanges can (and do) fail from the extreme RPM attained, exploding with a lot of dangerous shards flying out.
In my opinion proper practice is to go 1/2 speed maximum on the Kelmar if you're doing "start and forget" rewinding with standard 2000' reels. This will be somewhat slow at first then a bit too fast at the end. If you're in a hurry then stay at the bench, starting out at full speed and slowly reducing it to about 1/3 during the run so the actual film speed is more or less constant.

Posted by Ben LaCrosse (Member # 4662) on 05-21-2008, 12:30 AM:

Thanks Dave, for the detailed reply [Smile]

I am not a fan of rewinding at full speed either.

One thing about the auto shutoff roller on our rewind tables is that it has horizontal play in it. It is free to move side to side on the shaft. Even with the screw-in stopper. Is this something to be concerned with? Or is it engineered that way for tolerance issues? Sorry yall, my OCD has been peaking lately and just the little tiniest things are making me worry to great lengths. And cause INDY 4 is here and there is to be no scratching of any kind, especially during buildup.

and it is a 8900 series table, not 8000.

Posted by Dave Macaulay (Member # 813) on 05-21-2008, 10:06 PM:

The play lets bent reels run without scratching film (not TOO bent) but the film lays flat mostly from having a short distance from the arm roller to the takeup. Going reel-to-reel with the spindles that far away allows the film to flap around - there's a good breeze from the reel flanges - and start sidling around on the takeup. That's just a theory, but I see a big difference in the rewound film roll with vs without the arm/roller. Just remember to turn the speed down before clanking the roller up... the drive keys do shear off and Kelmar doesn't have replacememnts - you have to buy the whole plug-in adapter ($$$).