Film-Tech Forum ARCHIVE: Ballantyne Pro 35 VIP Base Take Up Slipping

This is topic Ballantyne Pro 35 VIP Base Take Up Slipping in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Graham Way (Member # 4612) on 01-06-2008, 05:36 AM:

Hi, I'm new to the forum and not in the industry, however, I do love my movies and some months ago got a Ballantyne Pro 35 with a VIP base and Strong Lume-x lamphouse. The projector has come from a theatrette run by Qantas Airlines, and generally seems to be in good condition.

With the help of a friend who uses 35mm portables for outdoor screenings, we re-assembled the pieces and wiring and got it up and running in my home theatre/screening room and it has been working well for several months.

Just recently I have encountered a problem where, when I start the motor the takeup reel now does not spin quickly enough during the first 1 - 2 minutes to take up the film. Also, towards the end of a feature the problem occurs again when there is a lot of weight on the reel. I am using the 30" reels that came with the projector and these can be seen in the manual http://www.film-tech.com/warehouse/manuals/BALVIP.pdf

The manual refers to the belt tension and this seems fine. Also if you look at Fig. 5 on page 5 of the manual, it gives the tension for a 2000' reel, but not for a 12000'/30" reel. Can anyone help me out with the correct tension? Also, how often should the pads between part 27 and 2796 be changed.(2796 is the part with the 'A' on it and the belt from the motor drives this, and 27 is the part immediately behind it, which drives the takeup reel).

I have searched through the forums here and I have seen some older posts on this issue but they seem to relate to issues where smaller reels are be used.

Cheers and thanks in advance if anyone is able to help.
Graham

Posted by Richard Fowler (Member # 893) on 01-06-2008, 08:14 AM:

The Ballentyne lower takeup requires occaisonal disassembly, cleaning and possible replacement of the felt type clutch "dots". You are also probably running more current mylar ( estar ) prints which need tension adjustments.

Posted by Jack Ondracek (Member # 1466) on 01-06-2008, 11:21 AM:

There are two takeup designs on that manual. The one I remember working with is the one with the 'motor' on the takeup spindle. We also had the rewind option. It took something like 15 or 20 minutes to rewind a full reel. I forget if that motor provided some kind of variable rewind tension or if it actually tied into the takeup. In any case, we didn't have trouble with spindle speed.

Are you using some smaller hub diameter? That's not likely, but it would require faster initial speeds. Other than that, I'd check to make sure someone didn't change a pulley size, you don't have serious belt slippage and that the pads are clean and adjusted properly. Shouldn't be much more complicated than that. If everything's to spec, it should work fine.

While you're checking things out down there, make sure the shaft bearings aren't shot. As it fills, the increased weight of the takeup reel might be making it progressively harder to turn. Seems that might be tied to bushing or bearing wear.

Posted by Graham Way (Member # 4612) on 01-07-2008, 06:26 AM:

Thanks Jack, this is not the rewind model so there is no separate motor for the takeup. It is belt driven and as best I can tell the belt doesn't slip. The reels have 5" hubs.

Richard, I have taken your advice and decided to disassemble and clean the lower takeup assembly. Removing the nut, the outer tension plate and the spring was relatively easy. However, the inner tension plate has a locking pin in it to prevent it slipping loose. (Which makes me think the the spring and outer tension plate are redundant, unless the pin were to break.)
My new problem - is there an easy way to get the pin out??
It needs to come out to adjust the pressure on the clutch, and also to get to the pads. At first I thought it was a small hex screw but it is a pin with no obvious way to grip it.

Posted by Dave Macaulay (Member # 813) on 01-07-2008, 09:34 AM:

I don't understand the pin. Normally the only pin is in the spring spacer; it engages the slot in the shaft and keeps the spring from turning on the shaft, tightening or loosening the tension adjustment nut.
From the back side you should have 1 or 2 nuts, the spring, the spacer, then the 2796 pulley and bearing. Then the 2785 friction disk with the felt pads, attached to the shaft with setscrews. If this is pinned on, no big deal as it really doesn't need to come off.
The usual problem is that aluminum is worn off the 2796 inside face and the felt pads get full of aluminum dust, making the surface very hard. The 2796 can get a groove ring worn down where the pads hit it too.
I've never seen replacement felt pads. You should be able to clean them off, but extreme solvents may attack the epoxy that holds the pads on. Brake cleaner, kerosene, or varsol paint thinner should be OK. Lacquer thinner or acetone would be pretty risky.
Once clean and dry soak the pads with silicon or synthetic oil.
If the 2796 has a groove it can be refaced at a machine shop, you should have a smooth surface when done so the pads don't just get ground off.
This tension assembly should have a 3V/3L V-belt drive, roundthane only if you can't get a proper belt. Both pulleys and the belt should be clean and oil-free.
If the belt and tension are OK you can still have slack at the start if the reel hub is too small, I think the minimum is an 8" hub but you can check this easily. Lace up some film on the hub you have and hand advance the projector. If the hub is too small you will get slack, if it's large enough the film will pull tight. If it's too small you can just wrap junk film around it to make up a big enough "hub" to work, taping the end securely and threading onto it. This older style takeup has a high drive ratio and the shaft turns fairly slowly, the newer type (seen in the ballantyne reel arms PDF) turns much faster because of the small driven pulley and will work with standard house reels: I don't think the ones you have are fast enough for a 5" hub.
Adjusting the takeup is usually described as "not too loose and not too tight". With 30" reels you should have an EZ-hub takeup reel - the pictures show one fitted although not super clear in the Film-Tech PDF. If you have a solid flange reel you may have trouble with slack on startup. If you can adjust the takeup tension just slightly tighter than where the film stays tight on startup with a solid flange reel this is the best you can do. This will likely be too tight and you will have the holdback sprocket singing for the first few minutes, but if the film goes slack you will get some damage (estar) or a film break (acetate) when it snaps tight as the reel catches up. An EZ-hub takeup is best.

Posted by Richard Fowler (Member # 893) on 01-07-2008, 09:55 AM:

Dave has noted issues about the "soft" aluminum casting wearing on the tension plate which we noted after a few years of use on a bunch of these systems we installed. Projection reel ratio (hub to outside) is very important and ez-hub slip reels best way to go on take-up.

Posted by Graham Way (Member # 4612) on 01-08-2008, 02:59 AM:

Apologies, I didn't explain myself very well. The pin is engaged where you describe it in the Spring Spacer.

The Spring Spacer has a thread and needs to be unscrewed off the shaft. Because the pin is engaged, I can't unscrew the Spring Spacer to get to the pads to clean them and examine what kind of wear has been occurring.

I can't see how to release the pin ...

Posted by Dave Macaulay (Member # 813) on 01-08-2008, 09:06 AM:

Something is dementedly wrong if the spacer is threaded onto the shaft. The way it works is simple: the pulley turns on the shaft with a ball bearing while the inner disk is attached to the shaft, friction via those felt pucks makes the disk (and shaft) turn. The spacer is pushed against the inner ball bearing race on the pulley and forces the pulley face against the felt pucks. The spacer has a pin that rides in a slot on the shaft to prevent the spacer from rotating on the shaft: this helps keep the inner bearing race from turning and damaging the shaft, and helps keep the nut from self-adjusting.
The spacer can not be threaded onto the shaft - as you note in your first post that makes the tension unit useless. The pin may have been pushed in too far and is hitting the bottom of the slot, or somehow the spacer is rusted or gunged up inside and seized to the shaft. If you put a solid hub reel on the takeup spindle you can grab the large diameter of the spacer with pliers and try to work it a bit - don't reef on it and break the pin off. Once it frees up a bit you should be able to get it off. You could try prying with screwdrivers on opposite sides simultaneously between the two disks to force the spacer to slide but this stresses the pulley bearing rather heavily and must be done carefully... maybe a new bearing is required already anyway?

Posted by Gordon McLeod (Member # 33) on 01-08-2008, 01:39 PM:

It is important that whenever a felt slipclutch design is involved that the felts are saturated in the correct oil

Posted by Graham Way (Member # 4612) on 01-09-2008, 07:10 AM:

Dave I agree that's how it should work. So after further examination, I found that the leading edge of the spacer was damaged and wedged into the thread, making it look threaded. After clearing this and some 'appropriate' coercion the spacer came free, and so did the pulley.

I cleaned the inside face of the 2796 pulley and there is no visible groove. The 2785 friction disk with the pads moved slightly back on the shaft to reveal what appears to be oil slots?? Is oil required here as part of the maintenance?

The pads are black and appear to be very well impregnated with oil, so based on your comments and Gordon's comment this seems to be correct.

I will be able to clean more fully on the weekend, when I have more time. Now that the spacer and spring are working as they should, I have reassembled for a quick test and, the lack of tension appears to be solved. Though, I need to experiment a little to find the "not too loose and not too tight" spot.

Thanks for your help and tips [thumbsup]