Nylon Shutter Track Installation Tips

After much fiddling around with the plastic tracks, I have finally reached a point where they work as one might expect and can now consider adding the motor system. There were a few important lessons learned in this process that I thought I'd share. Most of this hasn't yet appeared in this forum as far as I can tell.

First thing to note is that while there were some tooling scars here and there, I did not notice anything odd about the the track dimensions and shape when I first received them. However, the predrilled holes were not in useful places so I did fill them with epoxy as discussed in one of Rodney's posts. There are two holes per track. On the bottom end the holes are close to the end of the track. On the top end they are set back from where the two tracks meet. The holes in the dome I use are the pre-drilled holes.

The crucial thing I learned is how the tracks interact with the dome itself. If you look at the area where the tracks want to sit you will see that the dome "mounting" surface is curved. The consequence of this curvature is that when you tighten the provided bolts that mount the track do the dome, the pressure of the tightened bolts pulls the inside of the track in such a way to get the back of the track to bend to match the dome. When bent, the top and bottom of the track pinch together, shrinking the interior dimension of the track for about +/- 2 inches on either side of the bolt. This pinching is enough that the shutter wheels no longer fit in the pinched area and the top and bottom of the wheel are both touching. That means the wheels cannot roll through the track in the pinched area and must be pushed through. This was generating a lot of resistance in my case, much more than could be overcome by the motor.

There were two things I did to fix the problem. The first step was to put a large washer and a 1/4-20 square nut on the bolt on the back side of the track. This addition provides encouragement of the track to stay flat on its back side. Also, the square nut is what gets tightened against the dome. This arrangement makes a nice stand-off mount for the track and makes the track float on the outside of the dome. The track joints on each side don't meet exactly but they are close enough that the wheel pushes them into alignment as it passes from one track to the other. It is, of course, important to make sure the wheels are properly aligned with the track. As I mentioned in another post, I cut a slot in the back side of the track wheels to make adjusting their positions easier. The wheel positions aren't critical. They just need to float in the track as well.

The second step is really a repair and wouldn't be necessary if the first step were done on virgin tracks. In my case, I had the tracks installed with the pinching and this shape was frozen into the plastics. So, even once I figured out the standoff, the tracks were still pinched. To fix this, I pulled the tracks off, one at a time, but with the bolt and square nuts attached. Then, using a heat gun heated up the nylon. With a bench vise I was able to push the back of the track into place and eliminate the bulge created by the bolts. Then, with a block of wood, opened up the track so that it no longer appeared pinched. Once this was done, the shutter now moves easily along the entire length of the track. In fact, the upper shutter now falls down with noticeable force and makes the end wheels reach slightly past the end of the track and it gets a bit jammed there. A project yet to be done is to find a secure and robust way to provide a stop at the end of the track. I've seen the suggestions about using a stop bolt but I'm going to see if I can do something a bit more elegant that doesn't require another hole in the dome.

I do have a new concern after reaching this point. There was a recent wind storm in my area where the winds were forecast to be 90 mph. Thankfully, the worst gust was only 45 mph but just 20 miles to the south there were recorded gusts over 90. I had already added some safety straps to the inside to hold the dome down during high winds (anything over 30 mph) but this wind storm made me realize the shutters are held in place with just 8 countersunk bolt heads. Due to the countersinking, the nylon is getting a bit thin in places so I have nightmares about those bolts getting pulled out during high winds. I do have a way to put an external strap over the dome for this type of weather event but this only protects the upper shutter. I need to figure out something on the inside that protects both the upper and lower shutter.