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We spent a whole day on the initial tower raising. It took a lot of time because our site is far from ideal. In fact, it's on the side of a hill! I've never tightened and loosened wire rope clips so many times in my life. After we practiced plumbing the tower, we lowered it. It was easy to use the griphoist to let the tower down. The griphoist has two levers, one for pulling in cable, and one for letting it out. You simply use the forward lever to operate the hoist in reverse to pay out cable.

On the next visit, we mounted the turbine on the tower and repeated the raising sequence. The eighty pound turbine increased the weight of the lift by 60 percent, and I could clearly feel it in the griphoist. It took a lot more muscle than raising the tower alone. Rather than grumbling about the frequent adjustments to the guy cables, I found myself using the adjustments as an opportunity for a short breather. "Ah, I think those cables need adjusting," I found myself saying.

We raised the tower in less than one hour. It took another hour to plumb the tower and tighten the guy cables in a stiff wind. Though it wasn't a stroll in the park, physically operating the griphoist during the early part of the lift wasn't very difficult. It became much easier once the tower reached about 45 degrees. After the tower was upright and the Bergey began whirring, Nancy said, "I thought there was going to be a lot more to it than that. It was a lot simpler than I thought." That was the whole idea.

Adjusting Cable Tension

Unlike traditional towers with anchors at exact positions relative to the tower, the NRG system was designed for quick installation under field conditions. The guy cables are tensioned by hand. As the tower is raised and lowered, the guy cables may need adjusting. This system can't use pre-formed wire grips or

Above: The new American Gothic. The griphoist allowed us to slowly and safely raise our BWC 850 on a difficult hillside site.

turnbuckles unless the anchors and tower are all perfectly aligned. Because of the frequent and sometimes large adjustment necessary in guy cable tension, we used wire rope clips. Pre-formed wire grips require so much unwrapping and rewrapping that they lose their effectiveness in this sort of application.

In our case, the anchor eyes were at different elevations and slightly out of perfect alignment. This was due to the slope of our site and because I screwed some anchors down closer to the ground than others. These misalignments cause tension in the cables to vary during the lift. The thin-walled tubing used on the NRG towers easily buckles. So it's necessary to adjust cable tension as the tower is being raised and lowered. If everything was perfect this wouldn't be necessary. But our site was far from perfect.

Tower Height

Since I've been such a stickler about adequate tower height in my books, I was concerned that the 64 foot tower wouldn't clear nearby obstructions. But I didn't want to work with a taller tower either, at least until I gained some experience with the NRG tower system. Fortunately, the 64 foot tower was sufficiently tall and gives us about twenty to thirty feet of clearance above some nearby willows—our only trees. It also gave us sufficient clearance from the hilltops overlooking the site.

Turbine Thrust

After the installation, we returned to the site to check on the turbine, which is a good idea. One of the wire rope clips had slipped and the tower was no longer vertical. A stiff wind was blowing and the tower was pulling against the top cable that had slackened.

In the NRG system, the guy cables are tightened by hand. Let's just say that I wouldn't want to try this with a BWC 1500 in a strong wind. Nor would you ever want to make the mistake of not using the friction of pulling through the guy anchor eye to help hold the cable after loosening the wire rope clips. While it was never in danger of getting away from me, I was immediately conscious that I had to really lean into tensioning the cable and not make any mistakes. As it was, the thrust on the turbine was too great for me to get the tower top back to vertical. I got it to where I was comfortable with it and we left well enough alone as we were planning to lower the tower a few days later.

Lowering the BWC 850 with the Griphoist

Because we would be traveling for an extended period, we didn't want to leave the turbine unattended and thought it best to lower the tower. Though we've raised and lowered the tower only twice, we are quickly becoming proficient. The lowering went smoothly. As I developed a sense of how the tower behaves, I found it necessary to adjust the guy cables much less often. The down side is that there were fewer breaks from operating the griphoist lever. The cable moves only a few inches with each stroke of the lever. So, to lower the tower you need to operate the lever quite a few strokes. As an office type, I am not accustomed to all that activity and my shoulder muscles were sore for a few days afterward. But lowering the tower was uneventful, which is the way we like it.

Griphoists for the Rest of Us

While little has been written about griphoists, it's surprising the number of people who have used or are now using them. Bergey Windpower, for example, has been using griphoists for remote installations since 1993, when they used one to raise a 10 KW Excel on an offshore platform. Though you won't find any mention of griphoists in Bergey's installation manual for the 850, they recommend griphoists to their overseas clients, says Pieter Huebner, Bergey's field technician. When a heavy-duty drum winch isn't available, Huebner prefers the griphoist to raising a turbine with a vehicle. The griphoist "is much safer and gives much better control," he says. It "eliminates the possibility of miscommunication" between the vehicle driver and the tower crew.

The experience of Scoraig Wind Electric's Hugh Piggott mirrors that of Huebner. A griphoist is "hard to beat for erecting tilt-up towers, because it is slow and fail-safe," says Piggott. "Unlike using a truck or other vehicle to raise a tower, the operator of the winch has full control of the operation, and there's no dependence on hand signals or risk of missed cues." If you have to buy any tool for your off-grid wind system, Piggott recommends buying a griphoist. After using one myself, I agree.

Paul Gipe is the author of Wind Power for Home & Business (Chelsea Green Publishing, 1993), and Wind Energy Comes of Age (John Wiley & Sons, 1995). Gipe introduces griphoists in his new book Wind Energy Basics: A Guide to Small and Micro Wind Systems scheduled for release in early 1999 by Chelsea Green Publishing.

Disclaimer: I paid for all the components mentioned in this article and I have no affiliation with the manufacturers. In the mid 1980s I did some work for NRG. In the early 1980s I was a Bergey dealer. —Paul Gipe

"Griphoist" and "Tirfor" are registered trademarks of Tractel Inc.

Access

Author: Paul Gipe, 208 S. Green St., #5, Tehachapi, CA 93561 • 805-822-9150 • Fax: 805-822-8452 [email protected].

Web: http://rotor.fb12.tu-berlin.de/personen/paul.html

Bergey Windpower Co., 2001 Priestley Ave. Norman, OK 73069 • 405-364-4212 • Fax: 405-364-2078 [email protected] • Web: www.bergey.com

NRG Systems Inc., 110 Commerce St., PO Box 509,

Hinesburg, VT 05461 • 802-482-2255

Fax: 802-482-2272 • [email protected]

Tractel Inc., Griphoist Division (USA), 392 University Ave., PO Box 68, Westwood, MA 02090 781-329-5650 • 800-421-0246 • Fax: 781-329-6530 [email protected]

Tractel S.A. (World), 29, rue du Progres 93107 Montreuil Cedex France • 33-1-48-58-91-32 Fax: 33-1-48-58-19-95

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