According to the tag, this engine, serial number 16690, was manufactured by the Royal Engine Co. and given the name of Monarch. It should produce 1-3/4 HP at 500 RPM.
This is a “badged” Nelson Bros. engine, a company that is more widely known for its Jumbo line of gasoline/kerosene engines. Little is known about the Nelson Bros. Co., which was established in the early 1900s and went bankrupt in 1940 when all the company assets were sold. It later transpired that all the company records, blueprints, etc., were destroyed by the purchaser of the business in the late 1940s.
There is no register of engine dates for Nelson engines. This one is of later manufacture, identified not just from the serial number, or the fact grease cups were fitted rather than troughs for oil, but also that it was up-rated from 1-1/2 to 1-3/4 HP, which is believed to have started in 1916.
Nelson Bros. background
The Nelson Bros. Co. was based in Saginaw, Mich., and made identical lines of engines, many being sold through its marketing arm – the Royal Engine Co. In all, Nelson Bros. is believed to have sold some 400,000 engines, having, according to the company, reached the figure of 115,000 in 1921.
Engines were sold under a number of trade names, 50 or more, including Bohan, Maynard, Gray, Krackerjack, Macleod and Sattley. For more details and a comprehensive list of trade names, Mark Baier’s article “Nelson Brothers Company History” in the January 1993 issue of Gas Engine Magazine is most informative.
Marks on the Monarch
One can only guess at the date of this engine but it would be before 1923 as after this date they were sold with WICO high-tension ignition. I would estimate 1916 to 1920.
In some cases it might be possible to date an engine if it is stamped with a casting date on the underside rim at the front of the main casting, but there was nothing visible on this one.
The main casting of the engine is one piece and has the reference “N-12” behind the gear-side flywheel. This is common for contract engines, the “N” being cast only for trade names, the other castings of this size being “P” which was sold as both Jumbo and contract engines. Later 1-3/4 HP castings were “T” (Jumbo only) and “TA.” Castings for the larger engines had different casting codes.
An important feature to check is the engine number on the flywheel, stamped on the face of the pulley-side flywheel. This was always stamped by the Nelson factory and is useful as some vendors put their own number on the tag. It took a lot of careful work with the wire brush and emery cloth to clean up the rust pitting and find the number on the flywheel, which also required a magnifying glass and good light.
As purchased, this engine was painted black, and when I saw the first photographs from the vendor I hoped it was original paint. Unfortunately this was not the case, and all the original paint had been covered with primer and black paint. Inquiries on the Internet gleaned the suggestion that the color was a rusty brown – this might be right as I later found a minute trace of rusty brown after removing the engine tag.
Once ready to start work on this engine it was hoisted up onto a small work bench. All easily movable components were removed first, like the grease cups, and then the cylinder head nuts. It was soon evident that this engine had been restored at some stage because all nuts were in good condition and the majority were small, indicating that they were of more recent manufacture and not original. The black paint was clearly not original as splashes from it and the primer coat were on the edge of the engine tag.
The cylinder head was stuck tight even after removing the nuts and slackening the clamp for the pushrod. The safest way to remove a head in this situation, without risking damage, is to undo the bolts that clamp the connecting rod to the crankshaft and then remove the piston. A block of wood can then be inserted in the bore and hit with a large hammer to free it. It was clear that the gasket had been fitted with plenty of sealant which had firmly glued it in place. Unfortunately, the exhaust valve was not fully closed and it moved when using the wood. The exhaust rocker was a little stiff and the rocker arm broke near an earlier welded repair. I therefore learned a lesson that it is essential to remove the rocker arm before working on the cylinder head!
The crankshaft needed straightening, and while this could have been completed with the flywheels in place, they might have been damaged if anything became wedged under them while applying pressure to the crank. I therefore decided to take them off.
Before removing the flywheels, the governor weights were removed (one of which had already been broken in transit by the hauler) and part of the governor assembly and pushrod. For the first restoration in a long time, the flywheel keys came out using my specially shaped removal chisel and did not need to be drilled out. The crankshaft was cleaned with emery cloth and oiled before bolting on the hydraulic puller and easing off each flywheel. In fitting the puller, care was taken to ensure that the claws fitted against the hub and not the spokes of the flywheel.
Once the flywheels were removed, the side faces of the gears were cleaned and examined to find the punch marks that show the meshing point. There were several marks on the gears, but they appeared to be rust pitting, so an area was cleaned and new marks made with a pin punch, which were then covered in white paint to aid later identification.
In order to clean the flywheels properly it was necessary to remove the starting handle. Indeed – some say it is best to remove it and throw it away to stop getting hit by it.
There appeared to be a tapered pin holding it in place, but it was difficult to drill it out as the flywheel would not fit in my drill press, so it had to be removed another way. Fortunately there was a gap in the slot on either side of the handle that just fit a hacksaw blade. A blade was used to cut through the pin on both sides, so the handle fell out. The remains of the pin in the rim were punched out, which then provided a guide hole to drill out the remains at the bottom with a small electric drill.
The remains of the pin in the handle had to be drilled out before making a new one, the end of which was covered in Loctite before being pressed into position in the flywheel.
Straightening the crankshaft
Before removing the crankshaft from the block, I decided to try and straighten it while it was clamped in the bearings. In this case the crankshaft appeared to be no more than ordinary steel so there appeared little risk to straightening it, but this is an exercise to be undertaken by a professional if the crank is toughened in any way.
It looked as though the crankshaft was bent while in transit, probably at the same time a governor weight was broken. The flywheels ran true, so it’s possible something hit the crank while the flywheels were resting on the floor.
The options for straightening were considered carefully as there was deep pitting at the end of the crankshaft. Either it could be straightened or the offending section cut off, leaving a small spigot onto which a new piece could be fitted and welded in place. The latter course had appeal as it would tidy up things by removing the rusted section.
In the end I decided to see how accurately the crank could be straightened and then, if not satisfied, I could take the alternative course.
First, a straight edge was used to identify the bend and it soon became apparent that there was more than one kink in the shaft.
Not possessing a hydraulic press, which has been on my Christmas list for years, a small bottle car jack was used.
A piece of 3-inch-square box section – the arm from my engine hoist – was put on the workbench and lifted on wooden blocks so that clamps would easily fit under it. The engine casting was rested on top of this, using additional wooden blocks to keep it level.
The crankshaft was then moved so the high spot was at the bottom, the bend being so great that the eye was used at this stage rather than a dial gauge. The crankshaft was then clamped to the box section at the point just before it was to be bent, supported on a platform of steel and a V-block. A clamp was put on the other side of the engine, on the bearing cap, to steady the engine casting.
The jack was then put under the low point and pumped up until the shaft was under tension. Short strokes were taken to gradually straighten the crankshaft, frequently releasing the pressure of the jack to allow the crank to spring back, before repeating again.
As soon as the crank appeared straight to the eye, a dial gauge was used to measure the deflection. As the end of the crankshaft was badly pitted, a piece of scrap steel had earlier been turned then bored out to the diameter of the crankshaft (1.250 inches), which was now fitted on the shaft so the dial gauge could be used.
The crankshaft was rotated and the dial gauge used to identify the exact amount of the distortion. It appeared that not only was the crankshaft bent from the outer edge of the flywheel hub but it also was bent between the bearing and the flywheel. Having straightened one section of the crank it was then necessary to bend it from the point of the bearings as it was still showing movement of 0.120 inch.
The easiest way to straighten this part of the crankshaft was to leave it in the bearings. Even though it might damage them, they could be easily re-cast. The crankshaft was rotated to find the point of widest deflection, again setting this at the bottom to be pushed up by the jack.
The top of each bearing cap was securely clamped to the steel box section and then the dial gauge zeroed. The jack was pumped until the reading was 0.060 inch – half the variation – and another 0.010 inch added for spring back. The pressure on the jack was released and the reading checked. The straightening had not moved the crank enough so the pressure was built up again, increasing the spring-back allowance. The extra amount to be added for spring back depends on the rigidity of the clamping and the movement in the crank before the pressure starts to bend the metal, as well as the make up of the steel. I found that I had to allow over 0.050 inch to get the crank straight.
Once the dial gauge indicated that the required movement had occurred, the clamps were loosened and the crankshaft turned to check the result. I found that while there was an improvement, further bending was required, so the checking and bending continued until the variation shown on the dial gauge when rotating the crankshaft was less than 0.010 inch.
Once this was completed the crankshaft was removed from the bearings taking care to retain the shims in the same place as fitted. All remaining traces of paint and rust were then cleaned off, and any burrs in the keyways or the shaft smoothed off.
Cleaning the castings
The engine had been painted black on top of a new primer. Hopefully this paint and primer could be carefully removed so that traces of the old paint could be found underneath it. However it was soon apparent that there were practically no traces of old paint, which appeared to have been cleaned off before this earlier repainting.
The black paint used was flexible, almost rubber like, and soon clogged up whatever size grit of sandpaper used. The easiest way found to clean off this paint was to use a carbide rotary file in the electric drill.
The engine could not be left in an unpainted condition since the new primer had filled all pits and crevices in the casting. The only trace found of the original paint was when the engine tag was removed, which revealed some old reddish brown paint, although the original color had probably darkened with age.
To remove the engine tag, the middle of each of the two brass rivets was center punched and then drilled with a 0.062-inch drill. The diameter of the rivet was not known so it was drilled with this small diameter drill before a hammer and chisel were used against the side of the rivet. They sheared off having been weakened by the drilled hole. The diameter of the rivets was later identified as 0.094 inch and the holes in the casting were cleaned out using the same size drill. The area under the tag was not going to be painted as it was original and would be left for any future engine restorer.
Once the main casting was cleaned up, the flywheels and other components were given similar treatment.
The threads on all the studs were cleaned, as well as the threaded holes in the casting.
When stripping the engine, a number of the studs unscrewed when trying to undo the nuts. To replace them, two nuts were tightened against each other on the stud using two wrenches to lock the nuts. Thread lock was applied to the end of the stud before the stud was inserted and tightened using the top nut for the wrench. Finally, two wrenches were used again to remove the nuts from the stud.
A number of the nuts on the engine appeared relatively new, being zinc coated and somewhat smaller than the originals. If the engine had been made around the standardization of nut sizes in 1918, they would have followed the larger United States standard. To preserve the appearance of the engine, these small nuts were removed and new nuts made to the larger dimensions.
Bearings and shims
When the engine was stripped the bearing caps were removed to free the crankshaft and connecting rod. The carefully saved shims that had been fitted were made from cardboard and some disintegrated when they were removed, so they all had to be replaced.
The bearings appeared to show little sign of wear and looked as though they had been re-poured since nearly 0.100 inch of shims was required on each side of the bearing. The crankshaft journals appeared in perfect condition.
New shims were cut from shim stock and some 0.062 steel strip. To make the shims, a start was made using the thicker material. It was cut to a rough shape using a metal shear before drilling the hole for the stud. It was shaped using a grinder for the thicker pieces and tin snips for the thinner section. For material over 0.025 inch thick the shim was clamped to the drill table on a piece of scrap timber to support the under side while the stud hole was drilled. This shim must not be held by hand as this is the easiest way to lose fingers if the drill snags and spins the plate. For the thinner shim the hole can be punched using a cutter or drilled – but only if one of the thicker sections is used as both a guide and a supporting plate on top.
Shims were fitted putting an equal number of pieces of the same thickness on each side of the bearing. Different thicknesses of shim were used so that when the bearings need adjustment, the required thickness can be easily removed.
Trial and error was used to identify the thickness required by fitting and tightening the bearing cap. The crankshaft should turn freely without binding but, at the same time, should not have any noticeable movement up or down.
When cutting the shims ensure that the inside edge is well clear of the shaft. When fitting the shims I noticed that the inside edge of the bearing metal was not chamfered after pouring, which was rectified as it prevents grease from being scraped off the bearing.
Once the shims were fitted and clamped tight, the outside edges were given a final tidy up with a file to give them a uniform shape, fairly close to the outline of the bearing cap.