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Arm brake on rewinder...what for?

PostPosted: Sun Jan 07, 2018 3:59 pm
by Daniel D. Teoli Jr.
What is the arm brake on a rewinder used for? Isn't the friction brake all you need?

Re: Arm brake on rewinder...what for?

PostPosted: Mon Jan 08, 2018 3:55 pm
by pookybear

The friction brake works great on small reels of film however it does not work well on larger reels of film. Here is what happens with the friction brake. You set the tension and start to unwind the film from one reel to the other. The reel
with the friction set has a lot of film on it at the start and the film is given the mechanical advantage over the friction
brake. And of course the empty reel does not have have this advantage. Thus the film will wind kinda loosely onto the
new reel. Okay for sake of point it will be tight cause of the setting of the brake but is still "looser", you will understand
here in a minute.

As the film goes threw the reel you will notice that the friction side start to speed up as film is removed from it. This
is because the wraps are being moved from one side to the other but it also slowly diminishes the mechanical advantage
that once large reel had over the friction brake. Thus the brake now is applying more force upon the film. This acts just
like you have spooled up the friction value, in turn this will make up a tighter winding on the take up side, which now is starting to gain an advantage over the brake. In turn this makes it easier to wind the film up even thou more tension is now being applied to the film! This the outer wraps becomes "cinched" on the "looser" inner warps of film. It is not a
good effect to have on the take up, all kinda of bad things start to happen.

So lets introduce the hand brake. With this you are in control of the friction value at all times. Starting off heavy and
then slowing letting up on the brake as you go threw the reel. It takes a bit of practice to get it working well. But
nothing that can not be learned quickly enough on a junk reel of film.

I hope this helps.


Re: Arm brake on rewinder...what for?

PostPosted: Mon Jan 08, 2018 7:57 pm
by Daniel D. Teoli Jr.
So the brake is used on the empty reel on left as you rewind the full reel on the right? I've had to adjust the friction brake a lot due to the issue you mentioned about it getting harder to rewind. ... s-l225.jpg

When rewinding do you use the palm of the right hand to hold the brake down and rewind with the left hand?

Re: Arm brake on rewinder...what for?

PostPosted: Tue Jan 09, 2018 3:54 pm
by pookybear
The brake goes on the full reel to control the tension of the wrap that you are making on the empty reel as you wind.
Here is a video that has a very short clip of rewinds in action. Right at about 40 seconds in you can see a gentleman
running the brake with his elbow. His hand is guiding and checking the film edges for damage and of course his right hand
is moving the film from the braked rewind to the to the one he is filling.

Re: Arm brake on rewinder...what for?

PostPosted: Tue Jan 09, 2018 6:18 pm
by Daniel D. Teoli Jr.
Thanks for the video. I was at a theater last night. 12 theatres probably all automated. Nice to see someone still knowing how it things worked.

Re: Arm brake on rewinder...what for?

PostPosted: Wed Jan 10, 2018 4:06 pm
by pookybear
You are most welcome.

Things are hard to explain sometimes and pictures are really worth a 1000 words.

Re: Arm brake on rewinder...what for?

PostPosted: Sun Feb 04, 2018 11:09 am
by Daniel D. Teoli Jr.
Recently I ran through about 300+ 8mm and super 8 films on a Moviscop. I used a gloved hand for a brake. Worked great. as a brake on top of the reel. Cotton gloves work best but it wears a hole in big deal.