This is topic Strange Century Trap Problem in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.


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Posted by Mark Gulbrandsen (Member # 72) on 08-16-2007, 05:44 PM:
 
I recently rebuilt an SA (mid 7500 SN range) in which the intermittent was really hammered. During the rebuild I had the trap dismantled and while re-assembling it could barely get the gate bands back in place. You literally had to go in with the last band screw at a slight angle while pressing down at the top of the band to be able to get it screwed in place. The trap obviously had something wrong with it and this explained why the movement was so hammered. I estimated there was around 2.5 lbs of film tension with the gate closed . In the photo of the suspect trap at the top you'll notice the tension spring is bent down placing undue amounts of tension on the bands!! Bow Howdy! Now there's a wierd problem.



This photo below of another trap under normal circumstances... notice the difference in the tension spring on this trap and on the one above... This trap's tension is also set to 12:00. But why is this. Measurements seem to show that both trap castings are identical.... but they were not in some regard. I suspect the hole drilled through the casting for the pin that holds the two top band fastening points in place was off... thats the only hole I could not easily accurately measure because of its placement. Replacing the casting in this case fixed the problem. Oddly this projector had been in service for over 25 years, I don't know how many techs missed this serious problem over the years nor how many times the intermittent was overhauled because of this. A look back at shiping records and there were three other SA's on that same shipment from Century Projector back when they were still in New York. We found one other machine with this same problem... movement also hammered but the other two are fine.
I don't know if anyone else here has run into this or not and I'm not reccomending to everyone to run and check your SA traps... I merely wanted to show how crappy and inconsistant the Century's that were being made back then really are.

Mark


 

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Posted by Louis Bornwasser (Member # 3063) on 08-16-2007, 08:46 PM:
 
You're right; back then, you had a better chance with Westar, once repaired. Louis
 

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Posted by Steve Guttag (Member # 268) on 08-16-2007, 10:06 PM:
 
Mark,

Now I know this is an obvious one but I have to ask...did you set the eccentric to the minimum position? I know you said the indicator is at 12-O'Clock but I see on the lower picture the set screw for the eccentric is staring at us but in the top picture it is hidden.

Again...just seeing if it was an obvious thing that might not have jumped out and hit you.

I have had Simplex upper band holders where they didn't drill the block level so that one side has more tension than the other.

Steve
 

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Posted by Mark Gulbrandsen (Member # 72) on 08-16-2007, 10:14 PM:
 
Hi Steve,

Yea.. In fact a defective eccentric was the first thing I thought of. I tried a brand new eccentric which is the one shown in the top photo... the hole in new eccentrics are now 180 degrees from where the original was for what ever reason... The shaft has to be modified as well if you're going to use it or better yet also change the shaft since it has flat spots milled in it for locating the set screws. But that was not it and I ended up changing out the casting itself and putting the original eccentric back in. I'm sure the intermittent will be very happy now!

Mark
 

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Posted by Sam D. Chavez (Member # 1841) on 08-16-2007, 11:55 PM:
 
The trap being made of copper bends really easy. I had one where the bands were really loose and finally figured out it had been dropped hard and had folded in so to speak. I was able to bend it back and all was OK.

Anyone else notice this before?
 

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Posted by Pete Naples (Member # 761) on 08-17-2007, 01:57 AM:
 
Yup, dealt with a bent one in the past. Some clot dropped it, it landed on it's top side and bent on of the lugs where the tension adjuster runs through, result was you couldn't move the tension. % minutes with the trap stripped and the offending lug in the vice being gnetly persuaded back into shape sorted it.
 

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Posted by Louis Bornwasser (Member # 3063) on 08-17-2007, 12:18 PM:
 
Many times that part breaks off when dropped (or thrown.) Louis
 

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Posted by Randy Bowden (Member # 587) on 08-20-2007, 07:21 PM:
 
Mark, I had the exact same thing happen. In my case the problem was that the upper portion of the trap that the bands attach to was bent back, thus causing excessive tension. I still have that trap in my century trap parts bin, it's completely parted out but you can compare it to a normal trap and notice it's bent.
 

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Posted by Mark Gulbrandsen (Member # 72) on 08-20-2007, 07:43 PM:
 
I can certainly believe that would cause it. The thing I did was to compare it to a known good trap and neither of these bad traps appeared to be bent in the least. Were it just one trap I would assume it was bent but in this case it was two traps both shipped from Century on the same day about 25 years ago.

Mark
 

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Posted by Scott Norwood (Member # 30) on 08-21-2007, 07:56 AM:
 
What would cause an intermittent to be "really hammered"? Running without oil? Something else?

Also, what is the approximate vintage of a 7500 s/n SA? That must be fairly recent, since most of the ones that I've seen (mostly 1970s and earlier) are under 2000 (ish). (Are there different sequences for SA, MSA, SAW, etc., or are the serial numbers independent of model?)

Finally, are the SA traps specific to a particular machine (as with the JJ), or can they be interchanged (not sure why you would want to do this...just curious)?
 

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Posted by Mark Gulbrandsen (Member # 72) on 08-21-2007, 08:11 AM:
 

quote: Scott Norwood

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What would cause an intermittent to be "really hammered"? Running without oil? Something else?

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quote: Scott Norwood

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Also, what is the approximate vintage of a 7500 s/n SA? That must be fairly recent, since most of the ones that I've seen (mostly 1970s and earlier) are under 2000 (ish). (Are there different sequences for SA, MSA, SAW, etc., or are the serial numbers independent of model?)

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quote: Scott Norwood

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Finally, are the SA traps specific to a particular machine (as with the JJ), or can they be interchanged (not sure why you would want to do this...just curious)?

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