Questions regarding the placement of cable drums (spools) usually fall into one of two categories.
First – “I bought an 81” wide system but my trailer is only 75” wide. Can I cut it down? Where do I re-position the spools?”
Answer – The drums (spools) are never placed exactly where they will be on the tube after installation. We position them at the factory for ease of shipment. The installer always has to position the drums. They should be positioned as far apart as possible, just inside of the door opening so that the cable cannot rub the door frame when the door opens and closes. Placing them as far apart as possible gives the user maximum clearance to load gear without catching the cables.
Second – “My system is too long. Can I cut the tube without effecting the performance of the system.
Answer – As the springs are wound to create the tension that lifts the door, they grow longer in length. Space must be available for this growth or the springs will “hump up” as the door opens and closes when they run out of space. This will take lift force from the system and it will so cause premature failure of the system and the door will be too heavy. What is the minimum space needed for the springs to function properly? Here is the formula to calculate minimum tube length:
|The end bearing assembly, cones, drum spacer, & M-3 drums take 5” on each end (3” and 6” drums are different).||10.00”|
|The length of the spring is the last number in the description of the unconed spring (i.e. 160# springs are 26.50”)||26.50”|
|The space the spring needs for winding 10 turns is 10 times the spring wire diameter or the first number in the unconed spring description )(160# springs this is .218)||2.18″|
|Tube length needed for the system to work properly*||38.78”|
|*(This is on a single-spring system on a dual the spring length and the winding space need to be doubled to get the minimum tube length.)|