Film-Tech Forum ARCHIVE: REALLY tight lens barrel on Simplex 35

This is topic REALLY tight lens barrel on Simplex 35 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=010170

Posted by David E. Nedrow (Member # 4981) on 11-02-2009, 11:59 PM:

Until I get some new -- rebuilt -- projectors in, I'm running an incredibly poorly maintained Simplex 35 (1014). To give you an idea of how poorly maintained, when we first got access to the booth, the film gate was held in by one thumbscrew, and one twist-tie.

In any case, one problem with the projector is that the lens barrel is very tight, even with the lens clamping completely loosened. It takes far too much effort to inert and remove a lens. It also involves a lot of twisting, cajoling, swearing, etc.

I suppose the collars could be the problem, but I don't think so.

Any suggestions for fixing/mitigating this?

Posted by Randy Stankey (Member # 64) on 11-03-2009, 12:20 AM:

Is there a third screw on the lens collar to prop it open so you can insert or remove the lens?

It's a third screw in between the other two, facing the other direction. You loosen the two outer screws then tighten the middle one. It will wedge the collar open just enough to slip the lens in and out. When you have it installed the way you want, loosen the middle screw and tighten the other two.

I know at least one of my collars has it.
I have 4 lenses (Acad. - 1.85 - 1.66 - 2.39) but I only have three collars. I almost never use the Academy lens so it would be a waste to buy another collar. I just swap it with the 1.66 on the movie per year that I need it.
I know the collar I use for those two lenses has three screws.

Posted by Steve Guttag (Member # 268) on 11-03-2009, 06:57 AM:

Depending on when your lens receiver was made and when the lens adapter was made, you will have an incompatibility between the two. Strong, for reasons beyond me, decided to increase the OD of the G-2156 adapter to beyond what is specified (or in some cases, right at the max of the allowable range) in the SMPTE spec for 4" OD lenses. As such, they can be a very tight fit. They don't realize their problem because they also opened up their lens receiver ID so a modern projector with a modern lens adapter will fit together. An old projector with a modern lens adapter will have big problems.

Your solutions are to turn down the modern lens adapter, if you have a lathe. Open up your lens receiver (use a flap wheel and/or hone with a vacuum and a lot of patience) or change out the lens receiver to a modern one (they actually are better than the old ones...the older ones are not really round and have many high-spots.

It is possible that you have an old lens adapter (pre 1985) and the problem Randy speaks of exists though the lens locater ring on those tends to prevent too much over expansion.

Steve

Posted by David E. Nedrow (Member # 4981) on 11-03-2009, 07:33 AM:

Thanks, Randy & Steve,

That's good info.

I'll take a closer look at both the expansion screw on the adaptor and the ID/ODs.

-David