Harrison Eiteljorg, II
(See email contacts page for the author's email address.)
Because of the change in the CSA Propylaea Project (see "Data-Gathering Phase of CSA Propylaea Project Ends" in this issue), the final experiment with the scaffolding system could not be carried out in Athens. Therefore, the last work here in the U.S. to perfect the finished sytem is described and illustrated here. This is intended to provide all the information necessary for anyone to evaluate this approach to surveying hard-to-reach walls. (Please consult earlier articles about this to gain a better, fuller understanding:"An Apparatus to Aid in Surveying High Walls," CSA Newsletter, Vol. XX, No. 3; Winter, 2008, by Harrison Eiteljorg, II, at csanet.org/newsletter/winter08/nlw0801.html and "The Next Step for Scaffolding on the Propylaea," Vol. XX, No. 3; Spring, 2008, by Harrison Eiteljorg, II, at csanet.org/newsletter/spring08/nls0801.html.
As readers will recall, the aim of this work has been to enable a member of a survey team to hold a survey target at any point on the face of a wall (in this case, a wall of the Propylaea). The point is to be able to move relatively freely around the wall, side-to-side and up-and-down so that the survey target can be placed anywhere on the face of the wall. The basic device is a standard construction-site form of portable scaffolding from the Alum-A-Pole Company. It consists of two extensible aluminum posts on which so-called pump jacks can support a scaffold plank. When the posts have been raised to a vertical alignment and secured, the pump jacks on them can be pumped up (and cranked back down), permitting the scaffold plank to be raised as high up the wall as the posts permit. On completion of the work, the pump jacks and scaffold plank can be lowered to the ground and the posts taken down. The posts can then be moved to another location with relative ease.
In December of 2007 a successful experiment was carried out, and two people were able to position themselves on the face of the south wall of the Propylaea, as shown here and in the more recent of the previous articles about the work.
Fig. 1 - The scaffolding set up in the NW wing of the Propylaea, with wooden scaffold platform,
galvanized pipe as safety bar, and workmen on ladders to hold the posts against the wall.
There were two missing items in this 2007 experiment. One, the vertical aluminum posts used were 24 feet tall, but taller ones would be needed, perhaps as tall as 36 feet. While workmen could push the 24-feet-tall posts into the vertical orientation, longer posts would require some mechanical aid to get them into the vertical position. Two, the use of ladders leaning on the posts to hold them in position was a temporary expedient; a better safety device was required.
Experiments throughout the spring and fall of 2008 yielded solutions to both problems. To raise the posts a machine was constructed of simple 2 x 4 posts and plywood, with a brake winch as a lifting aid. (Note that a brake winch will not unwind if released, an important advantage here.) The machine was tested repeatedly at my home and can be seen here with the scaffolding post. Using this machine permits a post 36 feet long to be raised by a single person working the winch.
Fig. 2 - The machine for lifting the vertical posts of the scaffold system, with post in vertical position.
(To the extent possible, the background has been suppressed to make the parts of the machine more clear.)
As seen here, the machine is about ten feet long and about 10 feet high. A rope passes from the
winch to the top of the vertical posts and to the top of the aluminum pole to be raised.
There are planks to keep the post from swinging side-to-side, and there is a platform for holding cinder
blocks (or other weights) to serve as a counter-weight.
The second problem is more theoretical than urgent. When the posts are vertical and resting on a wall (against brackets for the purpose, see figure 1), all the weight of the pump jacks, the scaffold plank, and the people standing on the scaffold plank pulls the entire apparatus toward the wall; so it is very stable. Nevertheless, a precautionary safety device of some sort is needed to provide a margin of safety. Such a device was added to the machine and can be seen in the photo in figure 3. It is simply a ratchet strap tightened to hold the post to the machine that has, by the time of this photograph, already hoisted the post to the vertical position.
Fig. 3 - The machine with a post in the vertical position and the author standing on the pump jack
without a scaffold plank; a ratchet strap is holding the post to the upright post on the machine.
Although this apparatus was ready to be used in Athens (after constructing the machines, plans for which had been taken along), it was not used this past winter. Nevertheless, plans for the machine and other details can be supplied to anyone wishing to put this equipment to use. The total cost for the scaffolding equipment, two machines to raise the equipment, and the ancillary ropes, chains, and cables should be under $ 3,000 (not including shipping from the U.S. or import duties for the Alum-A-Pole equipment). The only tools required (not included in the costs) are a drill, a saw, pliers, and a socket wrench.
-- Harrison Eiteljorg, II
An index by subject for all CSA Newsletter issues may be found at csanet.org/newsletter/nlxref.html; included there are listings for articles concerning the use of electronic media in the humanities and The CSA Propylaea Project.