Peter Rooke builds a cart for the Baker Monitor VJ, part three of four.
This is the third in a four part series on Peter Rooke's restoration of a 1-1/4 HP Baker Monitor VJ. Read part 1 and part 2 for earlier stages of the restoration, and part 4 for the final installment.
A catalog picture showed a Monitor on a metal-framed cart, and photographs of a similar cart were found on Smokstak. With the help of a couple of dimensions, the pictures were scaled to produce a plan.
The axles for this cart would be made from 1.25-inch nominal pipe, in this case a true diameter of 1.66 inches. Some 0.25-inch thick, 2-inch by 2-inch angle iron was recovered from the scrap bin at the local railway society, and after straightening it there was just enough to make the cart. Two long pieces were trimmed to a length of 25 inches before drilling with 0.375-inch holes for the bolts to hold the cross-piece and axle mounting brackets. The front angle iron cross member supports the pivot, with the rear axle supporting the rear of the cart.
The brackets to hold the rear axle to the frame were fabricated using a scale plan to identify the alignment and miter for the support pieces. The first step was to machine the two support rings the axle fits into. These were machined from 3-inch diameter steel, drilling a 1-inch hole through the middle that was then bored out to 1.665 inches to provide clearance.
The main parts of the bracket were formed from 0.625-inch thick steel, 1.25 inches wide. The plate to mount against the frame of the cart was machined first, drilling two 0.375-inch diameter holes for the mounting bolts before milling out the space between the axle ring supports to a thickness of 0.3125-inch. The ends of the axle ring supports were mitered based on the plan before the edges to be welded were chamfered.
The four pieces for one bracket were clamped against the plan, which was used as a template to give accurate alignment, before being tack-welded together. After cleaning up, the welded parts for the second bracket were clamped to the first bracket. A piece of tube the diameter of the axle was fitted in the two axle rings to ensure they were completely square; essential considering the width of the axle support rings and to avoid potential alignment problems when sliding the axles into them.
The original cart was assembled using square-head bolts. The cart and mount required 14 bolts of different length, so these were fabricated. First, a length of steel rod 0.375-inch in diameter was held in the vise and threaded 0.375-inch by 16 UNC using a cutting die and plenty of lubricant.
To make the nuts and the heads for the bolts, 0.625-inch square steel was drilled then threaded the same as the rod. This size of the square steel was not strictly correct, but it would not have been productive to machine it down.
The threaded rod was cut to the lengths needed, plus 0.125-inch and the thickness of the head. One end of the threaded rod was given a short taper so that when welded to the head, weld would flow down the sides of it. After welding, the bolt heads were tidied using a grinder and the sharp edges were also removed from the nuts. The thread was then cut to length, rounded and cleaned with a thread die.
The front axle pivot and support were a complex shape and would have to be fabricated in several sections, starting with the support bracket that would mount against the front cross member of the angle iron frame.
The first stage was to cut a 0.625-inch thick disk of steel from 2.5-inch diameter stock. This was then drilled with two evenly spaced 0.375-inch holes, for the mounting bolts to secure to the cross member piece, followed by marking a center line and then machining two flats at the top and bottom to reduce the height to 1.75 inches.
Following the center line, the disk was cut in half, followed by chamfering the cut edges. A piece of 1.75-inch diameter steel was cut to a length of 1.75 inches before drilling a 0.625-inch hole through its length for the axle pivot pin. The two halves and the drilled 1.75-inch steel were then clamped to a block of steel to hold them in position for welding. The completed mount was ground then filed to its finished shape.
Once the pivot bracket was finished it was centered on the front cross member and two holes were drilled through the cross member, using the bracket as a guide, to fix it to the cart frame. Once the bracket was secured in place, the hole drilled in it for the pivot pin was used as a guide and the top of the angle iron frame was drilled through for the pivot pin.
To make the support or pivot body for the axle itself, the first step was to cut a 2.25-inch length of 2.25-inch diameter steel and drill a 0.625-inch hole through it for the pivot pin. At one end (what would become the bottom), the hole was enlarged to a diameter of 1-inch for the first 0.75-inch. This would allow a bolt to be inserted into the axle support to hold it for machining later.
A taper was then turned to shape this piece, reducing it to 1.75-inch to match the pivot bracket. A ridge was left at the base for final shaping to the clamp section. A 2.25-inch length of 2.5-inch diameter steel was then bored out to 1.665-inch, to be used as the support and fixing point for the front axle.
A 90-degree angle plate was then clamped to the milling machine table so the body of the pivot could be attached to it using a bolt through the pivot hole. After centering and setting the boring bar to cut a diameter of 2.5 inches to match the axle support, the end of the pivot body was shaped to receive the axle support. The axle support was then held in the mill vise so that the support could be milled out along its length, opening it up and creating two ears or flats either side of the axle. This was then drilled across the flats to 0.375-inch for a securing bolt.
A pivot pin was cut from 0.625-inch steel and cross-drilled at one end for a retaining split pin. This was inserted into the pivot then welded from the underside, inside the earlier enlarged hole at the bottom.
The edges to be welded were chamfered before the two pieces were held together for welding using the vise and a clamp. After welding, the pivot was finish-shaped using both a grinder and hand files to give the appearance of an original casting.
A catalog for these engines detailed that the cart wheels were 12 inches in diameter with a 3-inch face. However, photographs of another Monitor cart were found where the four wheels were 8 inches in diameter with a 2.5-inch face; these smaller sizes appeared more in keeping with the illustration seen in the catalogs. The wheels each have four holes in a steel hub plate, employed so a steel tube can fit through a pair of wheels to lock them together to hold the engine in place when it’s running.
To make the wheels, recycled 8-inch diameter steel tube was cut into 2.5-inch sections to create four rims, followed by trimming the rough cut edges on the lathe. The central hub of each wheel was made from 2.5-inch diameter steel bar, drilled through 1-inch, then bored out to 1.665-inch for the axle tube.
The wheel hub plate was made from 0.25-inch thick steel with four 1.75-inch holes, as well as a single, central 2.5-inch hole for the hub itself. The most efficient way to cut the holes on this steel plate was to cut them out as discs, a process known as trepanning. To do this, some scrap high speed steel from a worn out end mill was ground to form a cutter. This was then was fitted to the boring head to work as a trepanning cutter to make the holes.
The steel plate was first drilled with a 0.375-inch diameter hole in its center to fit over a securing stud mounted on the milling table. Doing this allowed the same coordinates to be used to align the holes for all four of the plates. Steel spacers were fitted under the plate to lift it off the milling table, and carefully positioned so the cutter would not touch them when it broke through the plate.
There is a lot of force on the cutter, despite carefully grinding it to shape. The cutting, therefore, took place at a slow speed, and at a very fine feed. Even so, the odd lapse meant that a couple of replacement cutters had to be ground to finish the job.
Once the four hub plates had their four holes cut, a hack saw was used to cut off the corners of the plates and roughly round them. The plates were then mounted together on a mandrel so they could be turned on the lathe to achieve the correct outside diameter to fit inside the wheel rims.
Once the plates were finished, any sharp edges were rounded with a file. Each plate was then centered on its main hub before welding them together. This was done using a combination of spacer blocks to set the plate at the middle of the hub for welding.
To weld the rim to the hub assembly, a short length of tube was held in the vise at 90 degrees to the vertical so the wheel could rotate. The hub assembly was a tight fit in the rim, so it was carefully positioned, tapping with a hammer to get the alignment right. The wheel was then rotated, the eye being a marvelous tool to detect out of true. After adjustments, the rim was tack welded to the hub assembly.
For the full welding, the axle tube was set just off vertical so the wheel could be rotated while welding, making the task relatively straightforward. Once the welding was finished, the weld was tidied up using grinding wheels.
The two axles were cut from nominal 1.25-inch diameter pipe to an overall length of 24 inches. The front axle was clamped in the milling vise so that a 0.375-inch hole for the axle pivot securing bolt could be drilled through the center.
To retain the wheels on the axles, a 0.1875 diameter hole was drilled 0.5-inch in from each end for split pins. To locate the wheels on the tube, four washers were cut to slide on the tube to the desired depth and tack welded to the axle tube. The rear axle was fixed centrally on the rear supports by applying tacks of weld.
The steering handle was formed from three pieces of 0.5-inch steel rod. A small jig was made using the same pipe as the axle, welded to a steel plate with a parallel stop spaced 0.5-inch away from the pipe. After repeatedly heating the end of the rod and working it on the jig, a ring was formed to slide around the axle.
Once the two rings had been formed, the two pieces of rod were trimmed to an overall length of 28 inches, with the handle to add 4 inches. The handle was bent to shape before tapering the ends that were to be welded together. One of the sidepieces was clamped to the handle, with blocks of steel used to maintain alignment. The other side was treated in a similar way. The welds were then ground so the joints were barely visible.
A reproduction crosshead for the pump was acquired to fit the wood pitman arms and lift the pump rod. This arrived pre-drilled for mounting to the pitman arms, but with no second 0.4375-inch hole for the “U” bolt to secure it to the flat pump rod. To drill this, a drill bit longer than standard was needed, with a minimum length of 6.5 inches, plus shank. The first inch of the shank on a spare drill was turned down to 0.3125-inch, before drilling a similar sized hole in the end of an 8-inch length of 0.4375-inch diameter steel. The two were then brazed together to make the long length drill needed.
The drill table on the pillar drill was rotated by 90 degrees so the cross head could be fixed to it using a combination of clamps and bolts. The position of the hole to be drilled had already been marked on the crosshead with a center punch and this was aligned then drilled.
The distance between the centers of these two holes was 1.6875 inches. Allowing for the 0.4375-inch diameter of the steel, a piece of 1.25-inch diameter steel bar was used as a former to bend the bar around. The bent bar was checked for fit and adjusted before trimming the legs to size and cleaning up the ends with a file, tapering the end of the short arm to assist in engagement. A 0.125-inch hole was drilled through the end of the long leg for a split pin. A suitable spring was found that would slide over the rod and was strong enough to keep the U-bolt in the locked position.
The two wood pitman arms were planed from redwood salvaged from an old gate. Each section was 1.125 inches by 1.625 inches and cut to an overall length of 60 inches to match the pump and its high pump rod. A 1-inch hole was drilled 2 inches back from one end to fit the wrist pin on the face plate of the pump gear. A 0.3125-inch cross hole was drilled through the pitman for a clamping bolt before cutting a 0.125-inch slit in the end wood as far as the 1-inch hole. A series of holes, 1-inch apart, were then drilled in the wood to provide a series of mounting points for the crosshead.