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  1. #1

    ACUdraw 50 Power Spring Installation

    TenPoint part number HCA-451 (ACUdraw 50 Retraction Power Spring) is required. Do not attempt to use a substitute. Note: Due to the length of the draw cords after their removal, replacement ACUdraw 50 draw cords (HCA-450) may also be required.

    *Additional items needed: a cigarette lighter or matches, a butter knife, a Phillips-head screwdriver, a 5/32” Allen wrench, a 5/64” Allen wrench and a #8 common nail.

    Note: You must remove the ACUdraw 50 unit completely to replace the power spring.

    1. Remove the two Phillips-head machine screws from each ACUdraw 50 cover, and then remove the covers.

    2. Pull both ACUdraw 50 hooks and handles all the way out and attach one of the hooks to the crossbow string.

    3. Cut or untie the draw cord that is not attached to the crossbow string (normally you cannot reuse the draw cord once it has been cut). Remove the hook and handle from the cord and remove the cord and knot that remains inside the axle.

    4. Cut or untie the draw cord on the opposite side. Note: Once you cut and/or removed the cord, the axle will spin and the power spring will unwind. Remove the remaining cord and knot from the axle.

    5. Remove the large white plastic washer and 5/32” Allen screw from the left side of the unit.

    6. Remove screws #1, #2 & #3 & #4 from the right side plate then pull the unit apart, removing it from the stock. Note: Hold the power spring close to the right side plate with your fingers to keep it from unwinding all the way as you remove it from the stock.

    7. Fully unwind the power spring and then remove the 5/64” button-head cap screw holding the opposite end of the power spring.

    8. Line up the flat end of the replacement power spring over the axle (make sure the axle has the recessed, flat area facing up) and insert the button-head Allen screw into the spring and the axle.

    9. Insert screw #4 into the right side plate (looking at the unit sideways, it would be the top left hole) and slide the loop end of the power spring over the screw. Slide the left side plate over the axle, insert screw #4 into the left side plate and finger tighten.

    10. Wind the retraction spring clockwise (forward) until tight, making sure the smaller hole on the right axle is facing forward. Note: Either turn the large white washer on the right side by hand, or use the 5/64” Allen wrench inserted into the screw holding the white washer in place.

    11. Insert a #8 common nail into the smaller hole and let the nail come to rest under the string guide.

    Re-installing the ACUdraw 50 unit:

    12. Remove the left side plate. To avoid the loop at the end of the retraction spring slipping off of screw #4, unscrew it only far enough to free it from the left side-plate. Place your right fore-finger against the head of the Allen screw, and, as you grip both side-plates and begin to pry them apart, wrap the fingers on your right hand around the plate and hold the retraction spring securely in place. Slide the left side-plate off the spool, making sure the retraction spring remains flat against the right side-plate and screw #4 remains in place.

    13. Keeping the 5/32” Allen screw in place with your thumb so that the screw will not dislodge, insert the assembly into the receiving holes molded into the crossbow’s butt stock. As you insert the unit, hold the exposed retraction spring in place with your left hand. Then, push the right side-plate firmly into place against the stock.

    14. Slide the left side-plate onto the spring-loaded spool (axle) and into place against the butt stock. Squeeze the two plates together with your left hand. Tighten screw #4 into the left side-plate until it is finger-tight.

    15. Insert and finger-tighten screws #2, #3, and #1 (in that order), being careful that the head of screw #1 passes by the nail and seats cleanly against the side-plate.

    16. Position the white plastic washer (removed in step 5) on the end of the left spool (axle) and screw it securely in place with the 5/32” Allen screw.

    17. Finish tightening the side-plate screws with your Allen wrench. Do not over-tighten.

    Installing the Draw-Cords:

    18. Tie a knot in one end of the new draw cord (unless you are re-using the draw-cords). Insert the unknotted end into the top of the draw handle and then into the brass pulley on the hook (hook facing up and pointing to the front of the crossbow). Note: Insert the cord into the hook from the left side when working on the left side of the unit and insert the cord from the right side when working on the right side of the unit.

    19. Thread the cord through the large hole (non-countersunk) in the axle and tie a knot at the end. Pull the knotted end into the axle’s counter-sunk hole until the knot is fully seated inside the hole.

    20. Making sure that the draw cord exits under the silver guidepost at the front of the mechanism, extend the cord and attach the hook to the bowstring (underneath the string with the open end of the hook facing up). Roll the spool forward just enough to remove the nail from the right side of the spool. Let the spool roll backward slowly, making sure that the left hook stays attached to the string.

    21. As you did on the left side, thread the remaining draw-cord through the draw-cord hook. This time thread the cord from the right side of the hook, and then tie a knot at the end. Pull the knotted end into the spool’s counter-sunk hole.

    22. Count the number of cord wraps on the left spool and wrap the right spool clockwise with the same number. You will have to thread the cord under the silver guidepost each time you make a wrap (loosening the Phillips-head screw in the silver guidepost will help when adding cord wraps then make sure you tighten the screw again when finished). Attach the right draw-cord hook to the bowstring with the open end of the hook facing up.

    23. Check to make sure the draw-cords are equal in length. If they are not, refer to the ACUdraw 50 Troubleshooting section.

    24. Once you are certain you do not need to modify the length of either of the draw-cords, you can clip the tail off the knots imbedded in the grip handles. Using a lighter or match burn the end of the cord until it forms a molten ball. Press the flat side of a butter knife blade against the ball to compress its surface and seal the knot. Pull the knot back into the recessed hole in the grip handle.

    25. Remove both hooks from the string and work the cords forward and backward several times, making sure the axle is spinning freely. If it binds, refer to the ACUdraw 50 Troubleshooting section.

    26. Replace the hooks on the bowstring.

    27. Attach the covers. Place the right side cover over the plates and line up the screw holes. Insert and hand-tighten the front screw, making sure it stays below the draw-cord. Tighten the screws and then attach the left side cover the same way.

  2. #2

    Join Date
    Dec 2012

    RE: ACUdraw 50 Power Spring Installation

    I think the spring either broke or became unattached on mine and is causing my issues.
    Not sure if this is something I want to try to fix and possibly make worse or have someone with experience fix it.
    Is there a how to video on this?

  3. #3

    Join Date
    Dec 2012

    RE: ACUdraw 50 Power Spring Installation

    Took the ACUdraw apart along with one of the cords, the end of the spring is broken where it screws into the barrel.

  4. #4
    Thanks for. Sharing

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