Peter Rooke makes a battery box for the Baker Monitor VJ, part 4 of 4.
The completed 1-1/4 HP Baker Monitor VJ.
It is still possible to purchase original battery boxes, but most have no lid and require some degree of restoration. There was no chance of finding one locally and to have one shipped would be expensive, so one would be made to original dimensions.
Inquiries on smokstak.com resulted in details of the measurements of a battery box 10 inches wide, 6.5 inches deep and 8 inches tall. Looking at some photos on the Internet, the thickness of wood used would be 1-inch at the rear for bolting it to the engine; the other sidepieces would be 0.375-inch and the base 1-inch.
The lid would just fit on top of the box so to help keep it in position; a raised section would fit into the opening. The sides and top would be covered in thin galvanized sheet like an original.
Redwood panels from a scrapped door were found in the wood store and these were planed to provide the pieces required to make the box. The original soft wood boxes were nailed together, but as this would not be easy or effective with hardwood small wood screws were used. Before assembly the recessed holes were drilled for the two bolts to secure it to the engine.
Galvanized sheet was salvaged from an old bin liner, with two pieces used with a big overlap. These were cut oversize as experience has shown that if the sides of the box are not completely square problems will arise when fitting a sheet closely cut to size. The sheet could be trimmed when fitted.
Starting with the front, a piece of 0.250-inch steel plate was clamped to hold the sheet in position so the sides could be bent. The sharp edges of the wood had already been rounded to help fitting the steel sheet. Once the sides were bent using a rubber mallet and hand pressure, the sides were clamped to the wood. The steel plate was then removed and small holes drilled through both the galvanized sheet and the wood. Shortened round-head nails were pushed into the undersized holes in the wood using the steady pressure of a clamp than a hammer. The drilled holes proved tight enough to hold the nails. If not, epoxy glue could be used on the shank of the nail and allowed to cure before any further bending of the sheet metal.
With the first piece in place, the second overlap piece was fixed to the rear and then both pieces trimmed top and bottom to match the wood. The lid was then completed. A piece of galvanized sheet was fitted over the main body of the box, without the wood lid in place. The corners were cut and folded then a small hole drilled and rivets used to hold them together as any heat to solder them would burn off the galvanizing.
One the metal part of the lid was finished, the wood core was fitted, with nails used to hold it, and then the metal edges were trimmed.
All that remained was to drill holes and fit the securing latches for the lid. These needed spacing washers to lift them away from the body of the box so they cleared the lids. Round-head screws were used for the latch to lock on.
Holes were then drilled through the rear of the box for the plug lead and contact wires. Original boxes had ceramic insulators, but in this case smaller holes were drilled with tight fitting rubber tube used to ensure water tightness.
The metal for the lid slightly overlapped the main part of the box spacing, so washers were used when mounting the box on the engine so the lid could slide down the back.
A buzz coil was built using a few modern car ignition components. Some quick research on the Internet revealed a number of plans and the enclosed circuit diagram details the layout used. At the heart of the wiring was a 5-blade, 12-volt car relay with both Normally Open (NO) and Normally Closed (NC) tags. A relay is an electromechanical switch with conductive arms that make or break a circuit when a current is applied to the relay.
Normally Closed means that current flows when the relay is in its idle state and this is the connection used for this circuit. When power is connected, power goes to the coil, but the relay is also activated and it moves the internal arm to the NO position, breaking the connection to the coil. When the coil is de-energized the relays internal arm returns to its NC position and power from the battery is connected again. This cycle continues as long as the wiper switch in the circuit is closed.
The spark was generated using an ordinary 12-volt automotive coil. An automotive condenser (capacitor) was fitted across the coil to prevent a voltage spike when the magnetic field created in the coil field collapses and the spark is generated. This spike can cause arching in the circuit. The condenser absorbs this voltage spike and prevents it damaging the circuitry and battery. The condenser must be capable of handling the spike, with a 400-volt DC and 0.25mfd (microfarad) rating generally quoted.
A cutout switch could be provided, but it’s just as easy to remove the connectors to the battery to kill the circuit. When the engine is in the rest position, make sure the circuit is not live through the wiper touching the camshaft lugs as this risks the coil burning out. A good connection to the body of the engine is essential. The ground connection was made by compressing a loop of wire between the head of a battery box mounting bolt and a steel washer.
Cloth covered high tension wire was used for the high voltage output to the spark plug, the original one that come with the engine. The spark plug connection was made by flattening the end of some 0.3125-inch diameter thin-wall brass tube, then drilling a small hole through the spade end for the core wire to pass through. The core wire was tinned before being soldered to the brass connector.
Assembly proved to be fairly straight forward, first fitting the crankshaft by angling and twisting it to fit through the cutout in the wall of the engine casting.
The white metal in the bearing caps was in fair shape and did not need replacing. The shims for the bearings were cardboard and paper and disintegrated when the bearings were removed. New shims were cut from sheet metal, different thicknesses being used in pairs either side of the bearings. These were inserted until, with the bearing nuts fully tightened, the crankshaft turned freely. To save constantly tightening and loosening bolts to check the fit of the shims, a pair of C-clamps were used to hold the bearing caps in place until the final fit was verified using the nuts and bolts.
There are metal washers on the crankshaft, and these sit in a groove in the bearing seat/caps to act as an oil seal. There is a gap at the top of the bearing caps at the crankcase. Some advocate sealing this with mastic or felt, but if the oil is at the recommended level it should not escape.
After fitting the piston to the con-rod the piston rings were compressed and the piston was pushed into the cylinder. The piston was rotated so that when fitted, the bolt in the bearing cap would be reached through the hand hole, allowing the single bolt to be fitted. The cylinder was then bolted in place.
The crankshaft gear was then fitted and held in position by its short key before installing the gear wheel, which was still fixed to its shaft. The shaft was greased before assembly and the two gears carefully meshed to align the punch marks on them.
The inlet valve was slid through the hole for the exhaust valve cage and then the cage itself bolted on. The cam-gear was then put in place before fitting the governor latch, then the cam follower.
The governor latch was adjusted so that at rest it barely touched the governor weight. The clearance between the exhaust valve and the top of the latch plate bolt was adjusted to less than 0.0625-inch. Care was taken to ensure that the latch plate was square to the latch.
After fitting the governor weight and its spring, a wedge was lightly hammered into the gap in the flywheel. After oiling the crankshaft the flywheel was slid into place, the wedge removed and the gib key pushed in. The pinch bolt was then tightened.
The letters “E” and “S” are stamped on the flywheel. On the Baker, the crankshaft drives the cam gear at a 4:1 ratio instead of the standard 2:1. As a result, there are two lobes on the cam as the gearing means the crankshaft makes four revolutions for every revolution of the cam instead of two. Using two lobes opens the exhaust valve on cycle.
The exhaust valve should be starting to open when the E is lined up with the exhaust valve stem. If you open the hand hole on the crankcase, the crankpin should be at about 5 o’clock. At this point, the cam should be just lifting the valve. This adjustment is made with the square headed bolt that also holds the detent catch block to the rocker arm. The exhaust valve should be open until just past top-dead-center (12 o’clock of the crankpin). If it closes too early it will affect the inlet stroke. The adjustment of this one valve is crucial to the engine running smoothly.
The buzz coil should just begin to fire as the “S” mark passes the exhaust valve stem, about 11 o’clock of the crankshaft rotation. The timer blade must be fairly clean and make good contact with the pins in the gear in order to work properly. If necessary, adjust the length of the timer blade to make contact when the “S” on the flywheel is level with the exhaust stem.
The crankcase was filled with medium mineral oil, as used for all my engines. A thinner oil can be used when it’s cold, but avoid using a heavy oil. The crankcase needs around 1-1/4 pints to get the oil to the right level, a depth of 1.125 inches. This needs to be carefully measured as too much results in oil leaks. The piston, con rod and main bearing are all lubricated by a small projection on the base of the con-rod, oil spilling down the side of the crankcase, being captured in a trap above each crankshaft bearing. Any surplus oil in the bearing is caught in a small well at the end of the bearing and returned to the crankcase.
One method for determining whether the splash lubrication is effective is to place a piece of paper over the hand cover hole when the engine is running. When a drop or two of oil per second is thrown onto the paper, the splash is sufficient. When there’s too much oil in the crankcase, excessive splash will work oil up into the combustion chamber, causing the spark plug to foul. Whitish smoke in the exhaust indicates too much oil.
These engines have a threaded hole in the case for a lubricator, but lubricators were only supplied on special request, as Baker thought the splash gave sufficient lubrication. If an engine is to be used in challenging conditions, fitting an engine lubricator might be wise.
Not all engines use the same amount of oil, but a cupful (there’s a cup integrated into the hand hole cover) will generally be the amount used by an engine under load using a tank of gasoline. A new hand hole gasket was made from 0.125-inch thick rubber gasket material.
For a dipstick, one end of a piece of wire was flattened, with a line scribed 1.125 inches from the end, with a loop formed at the other end. This can be kept in the battery box to be used whenever needed.
Some Monitor engines had a gear guard fitted to the pulley side of the engine. The top of the guard was secured by a plate bolted to the engine case, along with a bolt supporting it under the crankshaft bearing.
A 1.125-inch-wide strip was cut from steel sheet. The sheet was 30 inches long and should have been an inch longer to give clearance for the gears, so the gap was increased using a wide support bracket at the engine.
The first step was to make the support bracket, 2 inches wide, 6 inches long with two holes for 0.3125-inch bolts. Once the bracket was drilled, it was bent to shape and bolted to the engine so that the length could be marked by reference to the gear wheel. The bracket was then removed and trimmed to size.
The end of the bracket had to be curved to match the gear wheel. To allow for spring-back, the bend was formed using a 7-inch diameter tube instead of the 9-inch diameter of the gear wheel. One side of the bracket was clamped to the tube before another clamp was used to force down the other side, creating the curve. Once this was done, the bracket was bolted in place.
To start bending the strip, small bending rolls were used, gradually tightening them until the curve was right for the first half of the gear assembly.
Different bends were needed to ensure the guard lay flay on the underside of the bearing for its bolt and that it fit round the smaller gear on the crankshaft. This was done pressing against different diameters of round bar or using blocks of square steel in the vise.
After numerous trial fits and adjustments, the guard was ready for fitting to the bracket. The guard was first clamped to the underside of the bearing casing then the ends were clamped to the bracket, adjusting as necessary. When square, two 0.125-inch diameter holes were drilled through both the ends of the guard and the bracket before they were removed from the engine and two rivets lightly punched in place. The guard and bracket were re-fitted and again clamped to the bearing casing. Again clamps were used to hold the guard in place, and when satisfied with the alignment the final two holes were drilled before again removing it all from the engine to fit the last two rivets and firmly punch the first two.
Once more the guard was bolted in place so that the position of the hole in the bearing shell could be marked on the guard. After drilling, the guard was cleaned up by filing any sharp edges.
The setting for the mixer valve on this engine is approximately 1/4-turn open. If starting from cold, prime the engine by turning it over with the buzz coil disconnected and at the same time holding a finger over the mixer air inlet. Normally, this causes fuel to gush out so this must be done carefully, removing your finger as soon as fuel shows to ensure there is not a flood of fuel over the engine that might ignite when the engine is started.
Connect the buzz coil then engage the governor latch and hold it in this position. This holds the exhaust valve open, also stopping the wiper blade from making contact with the cam lobes. Start to turn the engine rapidly, then release hold of the starting handle immediately followed by the governor latch and the engine should start.
Once the engine had settled down to run steadily the governor was adjusted after checking the engine speed. This was achieved by adjusting the nut at the end of the spring, tightening it to increase the engine speed. The engine tag refers to a speed of 500 RPM, but as this engine will only be used for demonstrations I set it at 450 RPM when not under load.