Restoration Of a Stuart 600
By Nigel Mcburney
My wife Heather purchased this Stuart when the late Charles Hudsons collection was sold over twenty years ago, Charles kept it mounted on a block in an old stable, where it was set up to run a dynamo and a compressor. The dynamo was set up to charge batteries and the compressor was used to run his models on air. Whenever Charles had visitors or an open evening for club members the Stuart was always the first engine to be started so that he could demonstrate the steam models, so Heather and I knew it was a good working engine. The set can be seen in the book “Stationary engines for the Enthusiast -fig 151 ” and in Stationary Engine Magazine No 47 Jan 1978 .
It was absolutely covered in oil and grime but it kept on working and the only rust was on the exhaust flange. The bright parts had at some stage been coated with a thick coat of varnishThe engine did not have the correct Stuart cast sub base ,it had been mounted on a stout timber block.
Nearly two years ago I made a start on restoration, I had run it when we bought it, so I gave it another run before restoration ,before I run any long standing engine I always check that all bearing, valves and rockers etc are working, lubricated and working freely.
The petrol tank was partially filled and the engine given a wind, on the second wind away it went, just as it had always doneand I had not cleaned the Amal carb, when I reassembled the engine, about 18 months later it would not start. When I previously started it with petrol free from ethanol rubbish the carb jets did not block up in 20 years, on petrol with ethanol the carb jets were blocked solid in 18 months despite running the engine with the fuel tap shut until it stopped. The exterior parts stripped off easily, even the exhaust stud nuts came off,and Charles must have put some graphite on the threads. The crankshaft can be tricky to remove due to the close fit of the big end oil flinger and the close proximity, it is far better to remove the flywheels first, they weigh 25 lbs each. All the bearings moving parts and piston rings were in good order so not a great deal of work apart from grime and old paint removal. When I got to the bare crank bed ,cylinder and head I could see potential problems, through the cooling water ports, there was lots of chalk deposits in the cooling water passages, this can be a problem, with poor cooling and the risk of flakes of chalk deposit blocking the drain passages, leaving some water in the cylinder/head passages and the subsequent possibility of frost damage
So it was one of those times for decisions do I risk potential damage by leaving alone or just bite the bullet and remove the cylinder from the bed, and the head from the cylinder ?
The cylinder and cylinder liner came away together quite easily but the head was a different
proposition, the head studs are secured into four lugs cast integral with the liner, and these lugs are not easily accessible. The 4 head studs went through holes in the liner lugs and into rectangular threaded nuts, the shape stops them rotating.
The holes in the lugs had been made too tight a fit on the studs and two did come loose but two had rusted solid. getting the studs out was difficult as the lugs must not be damaged, so I set the liner and head up in the mill with an assortment of home made extended drills, some with thinned down shanks I managed to drill down the centre of the studs, until the studs were drilled away and I then had to drill the remains of the studs from the lugs on the liner, the holes in the lugs were made a little larger for better clearance , stainless steel studs were made, with bronze nuts so if someone has restore it again in the distant future the studs will be easier to remove. I never did remove the liner from the head, it was not worth the risk
,though I did manage to remove most of the hard water deposits with pointed bits of steel rod now that the studs were out of the way. Most of the remaining restoration was fairly straight forward, valves needed a light grinding in, the governor balls were not very well finished so these were polished up in the lathe. The magneto was ok just needed a good clean, points filed flat with a diamond hone and a new HT lead fitted. it was amazing how this engine had run for years covered in oil and no one had noticed the the magneto chain connecting link did not have the retaining clip fitted. When setting the engine up with exhaust pipe and water pipes the exhaust flanges and the water inlet flange are set at an angle and its quite difficult to get neat and tidy pipe runs in 3/8 and 1/2 inch steel water pipe, personally I do not like old engines piped up with copper pipe, it does not look right
Perhaps at this point I should mention that the Stuart 600 was not supplied as a finished engine, only as a set of castings, for the enthusiast to machine and assemble, Stuart’s offered to machine certain items ,at some cost, which were too large for the builders lathe, also optional were a second flywheel, a cast sub base, ignition was by wipe contact and trembler coil ,they did offer a magneto kit, with mag, mag bracket, chain and sprockets though the cost was over half the cost of the engine casting set ! The engine would run on gas or petrol and again a Stuart carb was an extra. I do not know when the engine was introduced but I have a page from a catalogue that builders had completed engines before 1923 and its generally thought that it was taken off the market around 1940 . Why build your own engine? well prosperous amateurs at the time usually had to treadle their lathes, building an engine meant youcould stop tredalling, mains electricity was not generally available and electric motors were very cumbersome and expensive ,mains coal gas as a fuel was available, plus if you could obtain a small dynamo it was possible to charge the lead acid glass cased accumulators to power your new radio, other wise it was a trip to the local radio shop to get the accumulator charged. I have seen a set of 600 drawings, so cannot comment if our engine is built exactly to drawing though it does appear to be similar to other Stuarts I have seen, screw threads are BSF with a few BA threaded screws. I spoke to Charles about this engine many years ago, he told me that when running on gas the hit and miss governor did not work that well and was not suited to evenly drive a dynamo, so he had about three experiments with petrol carbs regulated by the fly ball governor and eventually succeeded in getting an even running engine, he said to me that his work was a little Heath Robinson but it works very well, I did try it on propane gas but as Charles found it is not ideal.
So I decided to continue with the reliable late 1930s Amal carb, after all it did run for a very long time with this arrangement. I was also very lucky in finding a fellow enthusiast who had a Stuart sub base and got me a new casting using his base as a pattern, the sub base certainly improves the appearance of the engine by raising the bottom of the flywheels above the base level.