ROOFS

The exhibition "Charles IV - emperor by the grace of God" dedicated to the art of the last generation of the Luxemburg dynasty, i.e. Charles IV, Wenceslas IV and Sigismund (www.hrad.cz; www.karel-IV.cz) has been installed from October 2005 until January 2006 in the Metropolitan Museum of New York, where it was called "Prague, The Crown of Bohemia, 1347-1437" ( www.metmuseum.org). The exhibition contains more than 160 precious medieval masterpieces, provided by collection from Czech Republic, Slovakia, USA, Austria, Germany, Italy, Belgium, Great Britain and other countries.
We have been brought to the idea of using the wooden crane operated by human force according to our recurrent experience with transporting of oversized loads to medieval castles. Their courtyards are often inaccessible for modern heavy transport vehicles and for that reason the transport of necessary objects makes usually the essential part of total construction budget. The historical transport technology is very easy to use and probably very profitable for the roof truss repair works at the Tocnik Castle. The ecological and energetic aspects attract our attention to these machines, which work on the base of fundamental mechanics. We assume that the application of such machines could bring essential benefit even today.
The objectives of this experiment are to verify the verity of historical iconographical sources, to check the technical parameters of the machine, to compare the productivity, production and energy costs, ecological impacts with modern construction mechanization and research of usability of these simple machines, operated by human force, in contemporary construction procedures. The designer has already successful experience with using replicas of historic wooden tools for the construction of a wooden bridge at the Krakovec Castle and for lifting of a new bell into the bell tower in Sázava Monastery (both in Central Bohemia).
We would like to kickoff the common pan-European effort to save the traditional carpenter craft arts; therefore we have invited carpenters and blacksmiths from abroad to this event. Our partners from Massachusetts College of Art in Boston, U.S., Laura and Rick Brown will help us with testing the function and the correct parameters of the tread-wheel. Together with their students they have already constructed a functional replica of the Perronet baroque crane from the year 1750. Teachers and students of Czech technical and art colleges will participate in the event, as well. The event is performed in cooperation with the Academy of Sciences of Czech Republic and the National Heritage Institute.
We have performed background researches of similar activities in Europe and USA and we can certify that there was no such event of this extent in the past. Several tread-wheel cranes have been constructed, but they were assembled by modern technology. These cranes were never used on common construction site and mostly they are only partially functioning models.
http://commons.wikimedia.org/wiki/Image:Roemerkran.jpg
http://commons.wikimedia.org/wiki/Image:Old_crane.jpg
http://www.oberhausmuseum.de/52.html?&L=1

1) Project planning phase - The project documentary of the crane construction, performed in the Točník Castle, is already elaborated. The documentary needed some modifications in case of the crane installation in Prague Castle. These modifications deal with the cage and its fundament, static calculation and possibly a documentation of the machine presentation. The client receives the project documentation including the static calculations and the machine operation manual.
2) Approval procedures and contracts - The crane presentation in the Prague Castle was consulted in Construction section of the Municipal council of the Capital City of Prague. The municipal council has the opinion that the event is no building construction, therefore no permission or notification is necessary. If the client needs a written statement in this matter, it is possible to notify the authority about the planned event. The created documentation is sufficient for this purpose. The event will be performed due to a contract between the client, designer and the contractor. The contract defines the responsibilities of individual contract parties. The client receives the final functional crane, with declaration written by the designer, proving that the product matches valid legal regulations and with a declaration written by the project contractor proving, that the product matches the project documentation. Client's employees will be trained by the contractor to operate the machine. The training activities will be recorded in a written form.
3) Material preparation - Timbers will be crafted manually, planks and boards will be sewed by frame tractive saw, and the form of the wheel will be chopped from round timbers. The material preparation will be consistently carried out by medieval technologies, which were reconstructed on the base of iconographical sources studies, where replicas of historical tools will be used. The main part of the preparation will be carried out in location of Prague Castle, which can be free accessed by public. Location rental of the Synagogue in Libeň has been negotiated. In this location we have already performed the arch construction (object of the ARCHA Theater) and the arbor construction, which was used for presentation of Czech Republic in exhibition FLORIADA 2002 in Amsterdam. In Prague Castle (on the Northern yard) we will perform only some elements of construction procedures to present the utilization of medieval technologies and tools to public. The chopping and sewing presentation will be preformed in the Northern yard on a protection floor, assembled from oriented stand boards of 7×15 m size. Selected timbers of 4,0 m length will be transported by 3.5 t transport vehicle and by manually operated barrows with pneumatic wheels to be able to pass the passage access to the Northern yard.
4) Construction measurement will be performed in public in the working floor located in the Synagogue, in scale 1:1, using the circle method, which has been worked out according to the iconographic sources (sketchbook of Villard de Honnecourt and mural painting "Apparition of St. John" from the apocalyptic cycle in the Church of Our Lady at the Karlstejn Castle).
5) Production - The construction will be connected by classic craft joints, chopped manually, using hand tools. Most of the joint parts are wooden (pegs, dowel pins, chocks). The metal joint parts (wheel fame stirrup, pulley axis, nails in the form) will be forged. We assume that the main part of the production will be performed in the Northern yard. The material transport from the Synagogue to the Northern yard is described in the point no. 3. It includes the longest part of 0.8 m length and 300 kg weight.
6) Assembly - The construction will be completely assembled in the location of Prague Castle. For the assembly we will use wooden contrivances, which has been assembled in similar way (hoist, small ladder crane) and supporting construction (carpenter saw horses, assembly bench). The crane raise up will be a part of an international carpenter workshop with invited audience from many countries. It is essential to close the Northern yard for public during the assembly works. It is possible to keep free the passage to the exhibition "The Story of Prague Castle".
7) Possible presentation:

a) Passive exhibit without operation crew:
The functional skills of the crane will not be used. The crane will remain fixed in stable position. The visitors will be allowed to enter the floor of the cage and possibly the tread-wheel as well.
We suggest the presentation in form of one or more information boards, containing iconographic and project documentation, medieval carpenter technologies and tools, historic machines, future utilization of the crane on the Točník Castle, etc. We expect the information boards to be set up directly near the crane.
b) Active exhibit with plane program and professional operation crew of contractor:
The crane will be fully functional. The horizontal movement of the lever arm will be limited by the angle of 180° in western direction to keep the access to the Northern yard safe, on the stairway and to the entry of the permanent exhibition "The Story of Prague Castle". An object relocation of approx. 300 kg weight (safety coefficient 3.5) or 500 kg (safety coefficient 2.0) from the Northern yard to the Jiřský place and back. Suggested load objects: sandstone block of size 450×450×1000 mm, oak timber of size 400×400×3500 mm, and 5 persons in a hanging basket. Operation crew consists minimally of 3 persons, optimally 5 persons. The exhibition visitors can participate in the presentation by walking in the tread-wheel. The northern part of the yard and the Jiřský place has to be enclosed by fence in radius of 6.0 m with its middle in the pole axis.
c) Active exhibit with challenging program and professional operation crew of contractor:
Option 1 - construction of gothic vault (stonemasons program):
The event objective is construction of a gothic pointed arch in public. The vaulting will be assembled as a copy of a selected medieval door portal located in Prague Castle, in scale 1:1 from hardened polystyrene material, covered by burlap. The weight of single construction blocks will be approx. 25-30 kg. The construction blocks will be connected together by wooden pegs. The door portal will be based on wooden floor with marked anchor points on it. The arch will be constructed by using the crane for moving of single blocks on simple wooden stiffening truss. After setting down the voussoir the stiffening truss will be removed. The portal height will be approx. 2.0 m. The assembly needs an assistance of an adult person; it could be performed without scaffolding or by using simple wooden scaffolding. The safety is the same as in a children's playground. The visitors can actively participate on object construction and the crane operation. The operation crew (of at least three persons) will supervise and control the construction. Information boards containing documentary graphics will be a part of the demonstration or possible a lecture about construction of medieval arches. Target group are parents with children in age of 3 to 17 years, schools and primary schools.
Other subjects feasible with similar technology:
one bay of a cross vault on ground plan of size 2×2 m, a part of barrel vault (climbing frame), construction of a cathedral wall torso (blocks of size 500×500×1000 mm, 6 to 10 pieces), construction of a round tower basement with portal, construction of a well-staircase.
Option 2 - construction of a gothic roof frame (carpenter program):
The event objective is a construction of a part of a medieval roof frame in public. The object will be constructed as a copy of a collar beam truss in a slope of 60°, in scale 1:5 from, using wrought spruce wooden material. Single construction parts will be connected by carpenter joints (dove tail, trim, cross birds-mouth) and secured by wooden pegs. The weight of a single construction part is max. 10 kg. The single connection (2 up to 4 pieces) will be performed manually on flat surface, according to a drawn pattern. The connections will be raised by using the crane, placed into inferior rafter a connected together by Andrew's crosses. A wooden floor will be installed on collar beams, which can be accessed by a ladder (opening in the roof), the truss can be equipped by battening and if necessary also partially covered by roofing material (tarp, overlapped shed, shingle). The ridge height approx. 2.0 m, assemblage can be done by one adult person without scaffolding. The safety is the same as in a children's playground. The visitors can actively participate on object construction and the crane operation. The operation (by three persons) will supervise and control the construction. Information boards containing documentary graphics will be a part of the presentation or possible a lecture about construction of medieval trusses. Target group are supposed to be parents with children 3 to 17 years, schools and primary schools.
Other subjects with similar technology:
construction of a torso or a first floor of a curbed house (one room of size of 2×3 m with window and door openings).