Film-Tech Forum ARCHIVE: Aligning 70MM trap rollers

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Posted by Richard May (Member # 2627) on 11-12-2009, 07:06 PM:

What is the proper way of aligning these? I changed the bands and also changed the lateral rollers, spring, and pivots. Is there some kind of aligning plate to place in the trap?

Posted by Steve Guttag (Member # 268) on 11-12-2009, 08:01 PM:

and on WHICH projector are you inquiring about?

Steve

Posted by Richard May (Member # 2627) on 11-13-2009, 07:46 AM:

Simplex 35/70

Posted by Richard May (Member # 2627) on 11-16-2009, 06:27 AM:

Anybody?

Posted by Rick Raskin (Member # 1561) on 11-16-2009, 03:43 PM:

I didn't see any spec for the roller tolerance. But assuming the film is not supposed spin the rollers, couldn't you use a piece of 70mm film and a feeler gauge? Say 1 or 2/1000 clearance on each side. Or saying it another way, put in a C***H*** of space (use your imagination).

Posted by Mark Gulbrandsen (Member # 72) on 11-16-2009, 06:05 PM:

If you check with Strong International they should be able to give you the distance from the fixed side of the lateral guide roller to the back of the trap or some other machined refrence point they used. They may also do this for the Intermittent sprocket as well as they definitely do this for the Simplex 35 machines intermittent sprocket. I just don't remember the sprocket setting distance off the top of my head. If worse comes to worse you could get a gal with a crystal ball and contact Howard Straight in the after life, he could tell you this off the top of his head... [Cool]

There is a factory gauge made for setting the lateral guide rollers on the DP-70 and I have one here that I made and had precision ground to be equivelent to the factory jig... apparently there was not as much concern for the Simplex... There is a gauge made by LaVezzi that is available but it still doesn't get the sprocket set to the refrence point. Once the sprocket is set properly then the LaVezzi gauge will bring the lateral guide roller to where it belongs and the whole trap is then properly aligned. Century of course had a spiffy gauge for their peojectors and so did WESTREX.

Posted by John Walsh (Member # 168) on 11-16-2009, 06:43 PM:

I assuming you just want to align the intermittent sprocket with the lateral guide rollers. I have never worked on a Simplex 35/70mm but I'd think it was the same, generally. If so, there is a flat gauge that goes from the trap and down to (and fits inside) of the intermittent sprocket. (I have had OK results with just using a length of film.) The gauge is an AG1 from Lavezzi, or Simplex makes something similar. If the projected 35PA image was checked before any changes were made, you might be able to move the lateral guides until the image is the same left-right position as it was.

Posted by Gordon McLeod (Member # 33) on 11-16-2009, 06:48 PM:

I have never seen a 70mm guage have several of the 35mm ones
I would sujest laminating several layers of of ester 70mm togather to make a stiff guage and assume the spricket is in the right place

Posted by Mark Gulbrandsen (Member # 72) on 11-16-2009, 08:10 PM:

Westrex definately had a 70mm gauge we had one at CLACO. Phillips also sold two for the DP-70 both 35mm and 70mm versions.

Posted by Louis Bornwasser (Member # 3063) on 11-16-2009, 08:48 PM:

With the additional stiffness, 70mm film is its own gauge. Disregard anything EXCEPT the roller to sprocket adjustment initially. When this is set, you should look for equal focus in the four corners. In 35mm, it is necessary to shim the (hard) shoes to obtain then. This will be extremely touchy in 70mm due to the greater diameter distance.

You might conside then checking the squareness of the 70mm film sprocket holes by reversing the film you use to see if you get the same results. Louis

Posted by Mark Gulbrandsen (Member # 72) on 11-18-2009, 08:47 AM:

Louis... don't you have any of that 70mm stainless steel alignment film???? [Wink]

Posted by Louis Bornwasser (Member # 3063) on 11-18-2009, 04:04 PM:

Unfortunately no!

Posted by Steve Guttag (Member # 268) on 11-18-2009, 04:54 PM:

Ah...the Simplex 35/70...

In truth, the lateral guide rollers on the Simplex 35/70 are a little dubious. The problem stems from the fact that the film path is set up for 65mm in every other place BUT the lateral guide rollers and the pad rollers. As such you don't get a clean reference and in the case of the lateral guide rollers, they will actually curl the film around the runners.

If the film is not stiff in the area of the lateral guide rollers, then their absolute lateral position can't be achieved since you have figure out the amount of curl in the film as the film will hit the roller at an angle. I've been known to cut a coil or two off the spring on the LGR to allow the film to not curl.

In general, I've found it best to first mechanically center the film on the intermittent sprocket and then, by feel, tweak the roller position a little to see if it improves lateral stability...on the Simplex 35/70...I haven't seen much difference, if at all...in fact, I've once tried just taking them out! It only seemed to make threading harder.

Lord only knows why the sprockets, gate/trap...etc were not expanded to be true 70mm devices rather than living with a legacy that NOBODY needed for at least 30-years!

Steve

Posted by Sam D. Chavez (Member # 1841) on 11-18-2009, 08:12 PM:

This was not Simplex's best work, Howard Straight notwithstanding.

Upper loop size was critical as too big a loop and those funky lateral guide rollers could not begin to control the film.

My least favorite 70mm projector. Even the Ballantyne was better.

Posted by Richard May (Member # 2627) on 11-19-2009, 06:40 AM:

You're right about the upper loop Sam. We keep it as small as possible. It still flops around a bit, but the picture is rock steady.