David Lucas shows how to make his version of this timeless game that will appeal to people of all ages

David Lucas shows how to make his version of this timeless game that will appeal to people of all ages One of the joys of having young grandchildren is that you can again indulge in those pastimes that had to be abandoned as one's own children grew up. So you can decide for yourself whether the game described here is more for them or for me!
The Top Arch

This is one of the key components of the construction. First I tried to make the sides come to a feather edge but these crumpled, so I redesigned it to give a substantial (1/4in - 6.4mm) edge instead. This involved adding the internal side strips to the design to give a smooth inner surface.

The arch is cut from a 14 1/4in (362mm) square of 3/4in (19.1mm) MDF. Now I was planning to make two versions of the game so I needed two arches both of which were cut from the one square; if, however, you only want to make one version, a semi-circular arch could be cut from a piece of MDF 14 1/4in (362 mm) x 8in (203mm) approx., just deep enough to allow for the beam trammel hole. This hole is drilled centrally in the square or central and 7 1/8 (181mm) from one long side of the rectangle and with a diameter which just accepts the pin of the beam trammel. A straight cutter is used in the router and the beam trammel is adjusted until the outer edge of the cutter is 6 7/8in (174.6mm) from the pin. The cutter diameter is not, therefore, significant. The block of MDF is fastened to a scrap board with double-sided adhesive tape, making sure that the tape holds both the centre disc and the outer part of the block. The cut is then made, gradually deepening the setting of the cutter until the block is cut right through. The arch is then completed by gently sawing the outer part of the MDF block into two or trimming to size if only one has been made.

The Base
|  | The base is cut to size from a sheet of 3/8in (9.5mm) MDF and the three grooves are cut to receive the inner strips. These grooves are 3/8in (9.5mm) wide and 1/8in (3.2mm) deep and positioned as shown in fig 1, (remember that the base is 1/4in (6.4mm) smaller than the outer frame on all four sides). To cut them a simple jig is used, being a long strip of 3/8in (9.5mm) MDF with a slot cut to just receive a 17mm guide bush. The position of the grooves is marked on the base and the jig carefully placed symmetrically over them and held with a G-clamp which can itself be held in the bench vice. A 3/8in (9.5mm) straight cutter is used in the router. The groove parallel to the sides should be machined first and then the other two can be cut, parallel to the ends, from the first groove to the appropriate edge.
The Sides

These are cut to size and a rebate 3/8in (9.5mm) high and 1/8in (3.2mm) deep is cut along the bottom to receive the base. I used a 1/8in (3.2mm) slotting cutter with a bearing chosen to give 3/8in (9.5mm) depth of cut, with the router in a table and the MDF strip lying flat on the table, but other cutters, e.g. a rebater or even a straight cutter, could be used. A vertical groove, again 3/8in (9.5mm) wide and 1/8in (3.2mm) deep is cut 1 1/8in (28.6mm) in from the bottom end on the left hand side. For this the same jig as described above is used with the side clamped to a piece of scrap MDF and the jig clamped to the same piece of scrap (plus a 3/8in (9.5mm) thick spacer, again of scrap MDF) and running across the side at right angles. Unfortunately this jig was not wide enough to clamp directly as the clamp prevented full movement of the router - since then I have made a shorter but wider slot jig that can be clamped directly to the side. A similar groove is required in the right hand side but placed 2 7/8in (73mm) from the end. (Note: This position may have to be changed slightly - see discussion under 'firing mechanism').

Both ends of each side are mitred. A 45° bevel cutter is used in the router with the router in the table. Another simple jig, a rectangular piece of scrap MDF 1/2in (12.7mm) thick with a 45° bevel cut to a depth of 3/8in (9.5mm) across one end is used to guide the ends across the cutter. If no guide is used there is nothing for the side to bear on once the end has been reduced to a feather edge. The side and jig are held next to each other by hand pressure and the height of the cutter increased step by step until the bevel is complete. It will save a lot of cutter adjustment if both sides, the top and the bottom are all machined step by step at the same time. Both top edges of each side are rounded over using an 1/8in (3.2mm) radius rounding over cutter.

The Top
|  | This needs both ends mitred, a groove for the base and the top edges rounding over in the same way as for the sides.
The Bottom
|  | This also needs the same machining as for the top. In addition a vertical groove 3/8in (9.5mm) wide and 1/8in (3.2mm) deep is cut 1 1/2in (38.1mm) in from the right hand end. (Note: All the vertical grooves on the bottom and sides should match the horizontal grooves on the base). Then a horizontal groove 1/8in (3.2mm) wide and 1/8in (3.2mm) deep is cut 1/4in (6.4mm) down from the top from the left hand end to the vertical groove, to form a slot for the sliding lid of the 'ball park'.
Inner Strips
|  | The one running parallel to the sides, and so forming one side of the firing shute, needs two vertical grooves, of the standard size, to receive one end of each of the other two strips. It also has to have part of the bottom end cut away just to clear the corner brace of the firing mechanism. Both top edges are rounded over on all three inner strips. A horizontal groove to match that on the bottom is cut along the long inner strip which runs parallel to the bottom.
Inner Sides
|  | These are cut to size but may need slight adjustment to fit between the top arch and the appropriate inner strip. They are cut from 1/4in (6.4mm) MDF rather than 3/4in (19.1mm) so that the smooth face of the MDF is vertical. The join between the arch and the right hand inner strip in particular must be smooth so that the balls are not deflected from their path around the arch.
Inner Lid
|  | This slides in the grooves cut either side of the 'ball park'. The strip of MDF is rebated to a depth of 1/8in (3.2mm) to leave a tongue just under 1/8in (3.2mm) thick so that, even when painted, it will slide in the grooves. The left hand side must be cut down by 3/8in (9.5mm) for the first 1 1/4in (31.8mm) to allow entrance for the lid. You may also wish to trim the left hand mitre on the bottom in the same way for neatness. A small square of MDF is stuck onto the end of the lid to form a simple knob.
The Firing Mechanism

This is the most important part of the project, yet one which I wanted to keep as simple as possible. The very first thing to do is to find an appropriate spring or springs. They must be compression springs of a sensible size, fitting round the 1/4in (6.4mm) steel rod and strong enough to fire the balls to the top of the arch and yet not too strong for children to pull back. I conducted trials by asking my grandchildren if they could squash a spring I judged strong enough.

The 1in (25.4mm) long springs I finally used came from a Screwfix pack of compression springs but this would be a very expensive source if you didn't need a general supply. Maybe the 'bit-box' will provide what you need. The dimensions of the firing mechanism may have to be slightly modified to suit. I also thought that repeated use might well pull the corner woodwork apart despite the strength of modern glues, so, from the start I decided that the corner must be reinforced. It turned out that a Screwfix 50mm corner brace was ideal; if one of the holes nearer to the corner is carefully drilled out to 17/64in (6.7mm) (to allow free movement of the 1/4in (6.4mm) rod) then it came in just the right position. The corner brace was checked (and adjusted) for a true 90° angle and fixed in place with 3 M5 20mm pan head machine screws, washers and nuts. The height of the main hole was correct if the brace rested on the base. Appropriate holes must be drilled in the right hand side, in the bottom and in the short inner strip to match. The rod must be long enough so that when the assembly is pulled right back it does not come out of the hole in the short inner strip. A commercial wooden drawer knob was drilled out and stuck onto the outer end of the rod.

The firing mechanism underwent further development! Mark 1 used a washer on the rod, above the two springs, held in place by superglue, and omitted the loose washer between the springs. This was not successful as the washer eventually came loose and the springs twisted into each other. Mark 2 replaced the washer with an M6 nut drilled out to slide onto the rod and fixed in place with epoxy-resin adhesive. A loose washer was also added between the springs. This worked well but could not be removed if anything went wrong after assembly - without demolition that is! So in Mark 3 a small hole was drilled through the firing rod above the nut position and a small panel pin inserted and bent over. So far both Mark 2 (blue version) and Mark 3 (grey version) have been successful. A small piece of MDF is screwed to the right hand side to cover the spring mechanism.

Painting
|  | Each piece is painted before assembly. This avoids the problems of getting a clear separation between the two colours and of getting paint on the panel pins. Each piece was marked so that areas later to be glued were not painted - quite a fiddly business in itself.
Pinning

I used 25mm brass panel pins, again from Screwfix. The number needed will depend on the pattern used but 250g will give about 600 pins which should be more than sufficient for any one board. In order to get an even spacing and height for the large cups a very simple jig is used consisting of a small piece of 3/4in (19.1mm) MDF with two holes drilled in it. The diameter of the holes must be just enough to clear the head of the panel pins and the holes are set 1/4in (6.4mm) in from the edge of the piece of MDF. The distance apart of the holes is equal to the radius of the cup required. I used 1 1/2in (38.1mm) for the larger cups and 1/2in (12.7mm) for the smaller, top one. Then the positions of the pins at the centre of the semi-circles are carefully marked on the painted base and the pin driven in using the jig to control the height. Then the jig is positioned over the central pin so that the other hole, for the outermost pin, is in position and this second pin is hammered in. The jig is then lifted off, replaced over the central pin and butted against the second pin and the third pin driven in, etc. This gave reasonable semi-circles and reasonably upright pins although one or two might need a tweak with the pliers. The smaller cup is made in the same way although the central pin is removed to allow entry. The bottom of the base is divided into five parts, using another piece of MDF with one hole 1/4in (6.4mm) in from the end to space the pins, butting it against the previous pin each time. A few single pins are added at strategic places to keep the path of the balls in doubt, the most important of these being the one at the left hand end of the top arch. This will be struck by all the faster-moving balls and they will rebound from it on their journeys.

The pattern of pinning is a matter of choice as you can see from the two examples I have made. It is simpler in the blue one and more complex in the grey with semi-circles in semi-circles and divided semi-circles but the same principles apply. Some bagatelle games have small cups, to accept but one ball, drilled out from the base but I did not incorporate this idea.

Finishing

The various parts are now glued together, the firing mechanism being installed at the same time (mark 2) or later (mark 3). A block is placed under the base to tilt it being glued 5in (127mm) from the top (but this should be tested by experiment first as it may be affected by spring strength). Four rubber feet are then screwed in place, two near the bottom corners and two on the block under the base. These should prevent scratching of the surface on which the game is played and give the game a more stable position.

Finally a large number of balls are fired to see which cups are favoured and which are more difficult, so that a suitable numbering system could be devised. My wife then added these numbers with a marker pen. 10 steel balls (or more) 5/8in (15.9mm) in diameter are placed in the ball park. These balls, known as 'small steelies', come from a marble supply shop. The game is now ready for use.

Cutting List

Item | Quantity | Length | Width | Thickness
|  | in | mm | in | mm | in | mm
Top Arch (from | 1 | 14 1/4 | 362 | 14 1/4 | 362 | 3/4 | 19.1
Under Support | 1 | 14 1/4 | 362 | 2 | 50.8 | 3/4 | 19.1
Base | 1 | 23 1/2 | 596.9 | 14 1/2 | 368.3 | 3/8 | 9.5
Sides | 2 | 24 | 609.6 | 1 1/2 | 38.1 | 3/8 | 9.5
Top/Bottom | 2 | 15 | 381 | 1 1/2 | 38.1 | 3/8 | 9.5
Inner Strips | 1 | 15 | 381 | 1 1/4 | 31.8 | 3/8 | 9.5
| 1 | 13 | 330.2 | 1 1/4 | 31.8 | 3/8 | 9.5
| 1 | 1 3/8 | 34.9 | 1 1/4 | 31.8 | 3/8 | 9.5
Spring Covers | 1 | 2 1/2 | 63.5 | 1 1/8 | 28.6 | 3/8 | 9.5
Inner Sides | 1 | 15 | 381 | 3/4 | 19.1 | 1/4 | 6.4
| 1 | 13 1/4 | 336.6 | 3/4 | 19.1 | 1/4 | 6.4
Ball Park Lid | 1 | 13 1/8 | 333.4 | 15/16 | 23.8 | 1/4 | 6.4
Ball Park Lid Knob | 1 | 5/8 | 15.9 | 5/8 | 15.9 | 1/4 | 6.4
Also required (See text for details) - 1/4in (6.4 mm) Steel rod, springs, knob, corner brace, panel pins, nuts, bolts and washers, rubber feet, steel balls.