Belt Tightening

Above is a picture of the original seat belts after receiving some TLC.  They didn’t start out looking this respectable, and they weren’t operating properly.  I considered replacing them, but a new pair of genuine 914 seat belts are currently priced from $270 to $500 per pair.  The next best option is re-manufactured replicas from Professionally Engineered Products, which includes a core charge.  There are also a few specialty aftermarket companies that sell universal 3-point retractable belts, such as SeatBeltsPlus, and RetroBelt USA. But before spending more money, I wanted to at least take a shot at restoration.  Why pass up some obvious fun?  I started by removing the two screws that held the side cover on the winding mechanism.

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To my chagrin, the cover I removed houses the coil spring.  The chaos shown above happened in less than a second. The cover bounced off the ceiling, and sitting across from me at the dining room table, the wife jumped in her chair. For future reference, the spring housing is the thinner of the two covers.  I felt the chances of correctly replacing the spring were slim, but that wasn’t enough to stop me from trying.  You’ll never know unless you take a whack at it first.

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I removed the spring altogether, then unspooled the belt and unseated the end from the center spindle by popping it out of the slot with a small screwdriver. The holding pin slides out from the belt end loop, and the belt can then be pulled back through the slot and completely removed from the winding assembly.  This can also be done with the spring intact, as shown above.  With the belt completely unwound, wedging a screwdriver or allen wrench into the centrifugal clutch wheel will lock it so the belt can be removed.

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With the belt gone from the spindle, it can now turn freely to allow rewinding of the coil spring.  First the spring needs untangling, so that it looked like one single and perfect Goldilocks curl. That took no more than 10 minutes. Examining each end of the metal spring ribbon, it was clear that the tip with two bends attached to the center, and the side with just one bend attaches to the outer edge.  It also became obvious that the slots in the center spindle could only hold the ribbon in one orientation.  If flipped over, the center tip of the spring won’t fit the slots. So I placed the spring into the spindle, and began winding by hand using the clutch wheel.

If the spring ribbon is oriented properly, it will be winding onto the center spindle opposite to its natural curl. In other words, it will look like it is winding onto the spindle wrongside-out. The picture above shows this clearly. The natural counterflex in the ribbon also gets stronger as you wind toward the outer spiral, becoming progressively harder to wind as you proceed. This winding operation also took about 10 minutes max.

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Once the spring is wound tight and the outside end is fit into its slot in the back plate, slipping an allen wrench through the center spindle slot will keep the spring from unwinding.  Keeping the spring tightly coiled will prevent it from exploding from the spring plate, so you can free your hands to clean and replace the spring housing cover.  In restrospect, unless the spring is obviously broken, there is no need to remove the spring cover.

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With the belt liberated from the spindle, the chrome guides can be slipped off to allow washing of the fabric belts and separate cleaning of the metal. The buckle tongue is the only bit of hardware that will not fit over the belt end, and cannot be removed without unstitching the loop. Luckily, mine were in good shape and didn’t need separate attention. However, the belt guides shown on the right above had some rust that had pitted the chrome.

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Some online research led me to an old school method for removing rust from chrome: Oxalic acid, otherwise known as wood bleach.  The big hardware chain stores didn’t carry it, but a local shop stocked it alongside various wood and metal treatment products. Oxalic acid is used to lighten and even out wood discoloration, but it also attacks and breaks down rust molecules without harming chrome.

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I created a solution of about a half quart of hot water and a quarter cup of oxalic acid powder, and soaked the rusty pieces for 24 hours.  The VintageBMX blog I read suggested periodically wiping the residue from the pieces once or twice during the process.  I used a small wire brush to clean them off before returning them to the bath.  The picture above shows the white coating that forms over the entire surface of the objects.  Once the soak was done, I removed the parts and simply rinsed them with water.

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The acid did a pretty good job of breaking down the rust, which dissolved cleanly away from the chrome. Unfortunately, the oxidation had chewed deep enough into the metal to cause pitting, which would just start rusting again if not protected.  That’s why I decided to shoot the pieces with a thin coat of “chrome colored” paint, followed with a coat of heavy duty clear wheel sealant.  Letting it cure and harden for a few days will ensure a durable surface that won’t be eroded by the friction of the seat belt fabric.

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In the meantime, I decided to wash the belts. They were grimy after 37 years of use, and needed freshening up. Since the chrome buckles could not be removed from the belts, I thought maybe I could wrap them tight in a towel so they wouldn’t harm the washing machine.  Better yet, why not let the hardware hang outside the washing machine hatch, as above? That was a great idea until the spin cycle literally tied the belts into a death knot, battering the drum with a horrendous thunking until I hit emergency stop. It sounded worse than it was. But the belts were clean enough at that point, so I fired up the electric clothes iron and pressed them flat and dry between two towels.

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Reassembly of the winders benefited from reference photos, ensuring the refurbished seat belt guides were replaced in the correct order and orientation. Understandably, the factory does not wind the belt spindles as tight as possible, but with time the springs suffer from relaxation. To compensate, the spool can be wound a little tighter before attaching the belts. I wound mine to maximum tightness, backed off a half turn, and then reattached the belts. If you are adventurous, another method is to shorten the spring by clipping several inches from the end closest to the spindle center.  Good luck.

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Finally, here is the seat belt assembly mounted on the firewall behind the passenger seat.  The winder spooled out smoothly, but retracted with a bit of rattling that may disappear with use.  Some silicon spray on the centrifugal clutch wheel might help.  The belt fabric on the driver side was slightly fuzzy from wear, and offered more resistance to being retracted than the other. I misted the entire length of the belt with some ArmorAll, which made it more slippery.  After all that work, I was a little disappointed that the winders didn’t snap perfectly back to life. We’ll see if they become less temperamental after a little breaking-in. There are always options.

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