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70A Sweep Question


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  • 70A Sweep Question

    The 70A machine had counterbalance springs, like the table, attatched to the tops of the sweep links where they pivot on the machine under the catwalks. If you look at the top of the main sweep drive link where the large pivot pin is and there are two threaded holes in it then it probably at one time had them. A bracket was bolted to the sweep link with the spring attatching to it and to another bracket that was bolted to two holes on the rear side of the front wireway. (Standing behind the pinspotter, directly behind where the sweep pivots on the machine frame, if you look directly forward at the wireway there are two holes close together.)When the sweep was at zero, the spring was fully extended. From what I remember, the purpose of the springs was to smooth out the 'bounciness' the sweep tends to have when it hits 66 and when it is returning to zero. The center I took my training at had 70A's that still had these and the sweeps would glide to 66 and to zero in a very smooth consistent manner, no bouncing at all.

    Not that the bouncing sweeps are really a problem, although I've always thought they looked kind of odd.

    But I was wondering...

    Why was this discontinued on later machines? It does not seem like a necessary part that is needed but it sure made a difference in the smoothness of the sweep.

    Anybody else remember these?

  • #2
    Re: 70A Sweep Question

    Great question TJ. I dont' know the answer, but I'll be curious to hear the answer.

    I really enjoy the Simpsons. My problem is that I am starting to look like Homer. Doh!!!


    • #3
      Re: 70A Sweep Question

      When my Dad's center had 70s, 4 of the 8 were field converted "A"s. They were installed at dad's place in 74. I assume they were converted before that as I remember all 8 of his 70s looking alike. But I do remember the "A"s having a much smoother sweep. I know they did not have the counterbalance springs on them.

      Now that I think about it, the older machines did have a different shock tube. They looked more like a shock absorber than just a colapsable tube.

      I also remember the newer 70s had a plastic sleeve on the colapsable tube that would get tacky when it got oily or greasy. I never tried cleaning them.

      I wish I would have had BowlTech back when we had 70s, I would probably have a much better opinion of them, LOL.
      Gene Simmons for president!!!


      • #4
        Re: 70A Sweep Question

        Yeah, the machines I went to school on had a shock instead of a telescoping link, forgot about that. Also, instead of the threaded link on the machine where the telescoping link bolts to, which is fully adjustable, the shock style had this wierd half moon type bracket which has no in/out and barely any up/down adjustment. The in/out was adjusted by adjusting the shock length but the holes for it to bolt to the machine were not slotted.


        • #5
          Re: 70A Sweep Question

          Looking at my machines today I noticed I was incorrect about something. The spring bracket holes are on the sweep stabilizer link not the drive link.


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