The restoration is a real adventure, it is the amazing story of the SteamTeam, the volunteers that have succeeded in bringing the main engine back to life. Not with steam power because Cruquius' boilers were removed, but the old steam drive was replaced by advanced hydraulic technology. The following report of the restoration works is a fragment of the `Main engine status report February 2000´ by Jan A Verbruggen Ph D (© copyright Jan A Verbruggen 2000). Years ago Jan came under the spell of Cruquius' main engine ánd of making the engine move again. From that moment on he and lots of other volunteers invested all their leisure time to make this happen. This is the story.

March 1982

The Cruquius engine stopped working in November 1932. On 10 June 1933 she was steamed one last time for a closing and preservation ceremony. In March 1982 the Cruquius Trust council agreed to establish a working group to study the feasibility of making the engine move again. First of all, various ways to drive the engine were compared; it was decided to attempt hydraulic drive. Next, a number of aspects of the building and engine were investigated to see if these would permit motion. In a number of cases this entailed quite extensive cleaning or dismantling operations.

It all started with rubbish

1. Inspection tunnels
The 1846 building specification called for the basement to be constructed as a dry tub with watertight masonry bottom and walls. Floor level is about 1 m below polder level. On this 0,5 m thick floor stands the central engine foundation block with inspection access to the bottom ends of various anchor bolts via tunnels.
In 1983 basement sections were found to be largely filled with `rubbish´, which turned out to be mainly a thin black mud drying to dark grey. About 1 m above polder level an overflow hole in the outer wall was found. The `dry tub´ had apparently become a rubbish dump and a water collecting basin, where everything up to the overflow level was immersed in (somewhat corrosive) mud. As a result access to the inspection tunnels was blocked, and even the position of the entrance to these tunnels could no longer be located.
In 1985 volunteers removed, bucket by bucket, about ten m3 of mud and rubbish, and uncovered the inspection tunnels very few objects were found: a small elliptical cast iron weight which used to keep the equilibrium pipe drain cock normally closed, a larger one for a long-disused spindle lever on the hydraulic valve body, a spanner, a glass bottle, fragments of gaskets, shoes...
2. Weight
An indoor weight surplus is essential for the operation of the type of single acting nonrotative engine, and remains so for hydraulic drive. This surplus must be sufficient to overcome friction etc. and - because it was decided to operate two of the outdoor water pumps - to provide the required lift.
The central weight or `great cap´ consists of a hollow cylindrical main section. The central section is divided into six compartments. In four compartments openings are left for the beam connecting rods. The compartments could be loaded with purpose-made cast iron weights. In later times scrap etc. has been added to the weight in all compartments.
The net lifting force needed for one pump is about 120 kN. Because it was decided to restore one pair of pumps to operation, the required force will be 250-300 kN, to be provided entirely by the weight. The total unbalance force of the engine (when still working) is not known accurately, but has been estimated at 600-800 kN. A reduction of 400-500 kN is thus desirable. This could be achieved by removing 40-50 tons of indoors weight, by adding a similar amount outdoors, or by a mixture (e.g. remove 20-25 tons indoors and add the same amount outdoors).
In the course of 1990 8440 kg weight was removed from the weight cap which is now empty. Another 13555 kg was then removed from the pistons. This is a much slower, more arduous and messier job, completed early 1997. In the annular piston (7985 kg) the blocks are embedded in a goo of old, half-decomposed grease and water, from which they can fairly easily be extracted. The blocks in the central piston (5570 kg) are ‘cemented’ in tightly compressed rust, and removing a block appeared only possible if the rust could be removed first. Various methods were tried in the early 1990s, from drilling and grinding to a hot mixture of strong acids (Blekkenhorst), all to no avail. In 1996 Harry Kruk devised a brute-force method using the more powerful tools now at our disposal, which proved effective. If we allow c.200 kg for grease, water etc., the grand total of removed weight is c.22.2 t, leaving c.40-45 t structural indoor overweight.
This is how the story of making the engine move again started. The activities mainly consisted of cleaning, a fight against water, mud and rust, and repairing. Meanwhile the team studied ideas and made preparations for the new power source.

Power source

Cruquius' final set of boilers was removed c.1935; only vestiges of their foundations remain. The boiler house was eventually converted to exhibition space. For making the engine move again a way to drive the engine had to be found. As mentioned above various ways to do this were compared. Four alternatives were considered: steam, compressed air, hydraulic and electric drive. Each of these is discussed below. Eventually modern mineral oil hydraulics was chosen.

1. Steam
This would obviously be historically ideal, technically attractive, and spectacular. Steam supply appears to be technically feasible, but other aspects, such as planning and cost, are much more problematic. It would mean installing a substantial steam supply, restoring all parts of the engine to full working order, and the need for qualified (and probably paid) operating and maintenance staff. The cost (both initial outlay and annual operating expenses) would be very high, and there would be serious space problems as well: how can a steam supply be housed, without sacrificing a substantial part of space, in a way acceptable from both a technical and a planning viewpoint?
As a consequence, steam is considered not to be a realistic short or intermediate term goal. However, an important touchstone for any other solution must be, that it not block the way for possible future steam plans.
2. Air
Air has similar supply and space problems. An advantage would appear to be, that a fully functional condenser is not needed, but - as for non-condensing steam - a substantial exhaust would have to be made. Apart from the condenser, however, all engine parts must be restored to full working order, as for steam.
3. Electric drive
An electromechanical drive to a reasonably central point does not appear to be possible without unacceptably destructive intervention (such as making a big hole in the double cylinder bottom). An advantage would be, that engine components would not have to be fully functional or tight, just movable.
4. Hydraulic drive
Hydraulics with standard components offers the same advantage, and requires less space than an electric drive for the actual drive components (cylinders), and there is considerable freedom in the location of the power pack and associated components. Finding a suitable and not too conspicuous location for the long drive cylinders would be quite a problem, however. Two possibilities have been considered.
a. Use part of the existing passive hydraulic (buffer) system.
This subsystem was installed to prevent shock due to uncontrolled closing of the water pump bucket valves at the end of the steam stroke when the weight has reached its top position (see also the steam cycle page). This position is ‘locked’ for a suitable period (a couple of seconds) to allow the bucket valves to close. During the up (steam) stroke, two 225 mm (9") dia. plungers or rams, attached to the ears of the central weight, draw water from standpipes via check valves. The water column locks the weight in its top position until a bypass valve is opened simultaneously with the engine's equilibrium valve.
If this system could be connected to a (water) hydraulic power source via nozzles to be made on the HP and LP connecting pipes, it might be possible to use the existing plungers to move the engine. The plungers would have to be fully operational and all hydraulic joints and packings would have to be tight. The existing valves would have to be secured in their closed positions and made reasonably tight. Closing shut-off valves on the nozzles, and freeing the check and bypass valves, would restore the original situation and enable the system to be used for its original purpose, e.g. in a future steam scheme.
b. Mount standard hydraulic cylinders `parallel´ to the buffer rams, i.e. between the engine foundation and the weight ears, and use standard mineral oil hydraulics.
Much effort has been put into investigating the water hydraulics scheme. Eventually, and partly due to the problems envisaged, this idea was abandoned in favor of mineral oil hydraulics.

For technicians, students, industrial archeologists, and other persons interested, would you like to read the complete status report then click here.