The Saga of the Repair of the Belay Tower


Rick Casey, BRS Director

The Belay Tower at Mapleton Fields

As anyone who has taken Basic Rock School (BRS) knows, the Belay Tower that is used in the course is a unique device. It’s only purpose in life is to lift a 100 pound weight in the air, and then scare the dickens out of the BRS student who must stop it before it hits the ground. It effectively simulates catching the full force of a leader fall, and tests the mettle of the student using their own gear to stop it with their belay device. It is a wonderful teaching device for this purpose, which allows the student to practice this essential climbing skill without endangering anyone. I have never heard of another climbing club that has such an asset (though I suspect some exist somewhere), and consider the Boulder CMC very lucky to have it. It is located on Mapleton Street, between 28th and 30th, just south of the East Mapleton baseball fields, and just north of Whole Foods. It stands dormant most of the year, except for those few special days in spring and fall, when BRS students are put to the test. It’s a lot of fun, but just a tad bit anxiety-producing the first time you have to do it. Rocky Mountain Rescue also used this for practice when it was first built, but they have their own facility now.

So it was a source of no small concern when Brenda Leach, then director of BRS (and currently the assistant director), informed the Boulder Mountain Schools (BMS) committee that the Belay Tower was acting up on during its final days of use in the Spring BRS. It looked a like some deferred maintenance, and possibly a repair job, better happen before Fall BRS. Since I would become BRS Director that fall, it fell to me to see this got done.

Which meant I needed help! I did not know the first thing about the Belay Tower, other than helping to assist in testing a few times.  The components consist of two 40 foot telephone-pole like wooden towers, with a wooden crossbeam across the top. Suspended underneath its center is a big pulley, with a fixed line going through it, both reaching to ground level and beyond. One end is attached to the weight, and the other end of the line goes into the motor bunker, which basically applies a brake to the climbing rope going through it, which can be turned on or off with an electronic switch. The final end of the rope is held by the BRS student being tested. During the test, an experienced Tester holds the remote button that controls the brake, and a button that can winch the weight back up. To apply the test, the weight is hauled up, then the brake is applied, holding the weight in place. Then the Tester pulls out slack between the belayer and the motor house (like the belayer is giving slack to a lead climber); if the brake is released by the Tester, the 100 pound weight will begin to fall, pulling the slack out of the rope, until it goes taught when stopped by the belayer being tested. (In all my years of helping with this test, I’d never seen a student drop the weight yet — though some have come close!) The strategy of the Tester to simulate being a leader, and then to “fall” unexpectedly, by pressing the brake button, when the student is expected to “catch” the fall with their own belay device. The student is tied into a solid anchor while, so they are not pulled around by the force of the fall.

Fix-It Day #1

As you can see, the Belay Tower is a somewhat complex device. Little maintenance had been done on it for years, perhaps ever since it was custom built back in the 1960’s by Louis Dam and Lee Erb; it has been a sturdy and reliable device. The story of how they actually designed and machined the parts for it are lost to history (unless someone is willing to research the story!) The “motor” I referred to above is actually composed of a three pulley system, a brake, a clutch and a gas compressor. If you open it up, this is what you see:

motor bunker

The belay tower “motor” exposed…

That’s Bob Mathias (Hiking School co-director) helping with the first maintenance attempt on July 29 this year. You can see the rope coming in on the right, and going out on the left; in between, it goes through three pulleys and a brake. The rest of the crew that helped that day were Wayne Densmore, Steve Poulson, Brenda Leach, and myself. This is basically how we set to work: take stuff apart, clean what looks dirty, oil what looks rusty, and keep fiddling with rope, in hopes of duplicating the problem. In engineering, this is known as the precise art of “troubleshooting”…

Well, after about three hours of troubleshooting in the hot sun, we were no closer to determining the cause of the malfunctioning of the belay tower than when the morning started; but the inside of the motor bunker was certainly a lot cleaner! It had been vacuumed, swept, lubricated and generally tidied up, and tested every which way; but the rope would still bind sometimes when pulling up the weight, for some reason we could not determine. At this point we adjourned to nearby Turley’s restaurant for lunch to discuss the next step. Steve had some ideas to try, but was going to contact Louis Dahm, who he knew still lived in Golden. Later, Steve reported back he had an enlightening discussion with Mr. Dahm, and was impressed with his clear recollection of the finer points of the contraption, and had some ideas to try. The next fix-it day was set for September 4.

Fix-It Day #2

September 4, a Tuesday, rolled around, and Steve, Wayne and Bob met at the tower.

Steve and Wayne examining the interior of the motor

As Steve reported later in an email, after trying various things they were still mystified why the binding effect was still happening, when eureka! they started thinking outside the box; or as Steve put it, “above the box…” The problem was not in the motor, it was in the pulley that was forty feet above them! Sure enough, some more focused testing revealed it was the overhead pulley that was binding under load; the motor was fine. This was encouraging news, because the problem had been diagnosed, but it still had to be fixed. Now what?

The answer was to buy the best pulley appropriate for our need. Back at home, Wayne got on the computer, and soon helped to narrow down the search to the fine line of products offered by CMI, a small firm in West Virginia that specializes in rescue pulleys. Steve settled on the most appropriate one, even calling up one of their engineers to discuss it, got it ordered and soon we were ready for another fix-it day — hopefully the last one!

Fix-It Day #3

Steve and Bob with the brand new pulley.

With new pulley in hand, fix-it day #3 happened on Friday, September 21. This time Steve, Bob and Brenda attended (Brenda took these pictures). I was genuinely curious as to how this operation would be accomplished without a hook-and-ladder fire truck or a cherry picker to get someone up to the crossbar; but Steve assured us it was not a problem, as apparently this had been done before. (I think it is routine for RMR folks….)

Steve twirling the weighted cord to toss it above the belay

First a lightweight 6mm cord was tossed waaaay up and over the crossbar, using some nuts attached to the end for momentum — no small feat in itself! Shown here is Steve in action:

Next, a static line was attached to cord, hauled up over the crosssbar, and secured at the base.

Six or so wraps, figure eight on a bight and carabiner for the anchor.

Now the real moment of truth: to ascend the static rope  and replace the old pulley. For this, Steve used mechanical ascenders, and a chest harness, for comfort. It was still a bit of work to get up there!

Steve ascending the static line.

Thanks Steve!

Finally, the new pulley was in place! Once Steve was back down with the old pulley, the decrepid condition of the device was confirmed, and the new pulley should last the CMC for quite some time to come. The Belay Tower was saved! Many thanks to all who helped, but especially Steve!


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