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Harold Hall

Workshop Projects

Initial assembly

Having now completed the machining stage the engine should be given an initial assembly of the major parts to ensure that everything goes together as it should, or perhaps nearly everything. If though you find a screw here or there will not enter fully due to some minor misalignment do not be overly concerned you will be keeping me company. I do tend to start off with minimal clearance in my clearance holes for screws so its not that surprising. If you find yourself also in this situation open up the offending hole by a drill size and try again.

 

The main purpose of this stage is to determine that the mechanisms work  and this is best done a stage at a time. Typically, first assemble the crank shaft into the bearings and these onto the soleplate and check to see that the crankshaft can be turned reasonably freely, making any adjustments found necessary. Do not be over concerned about a little stiffness, probably a good thing as it proves you have not made the parts with a too generous clearance. Add the remaining parts a group at a time, testing the completed assembly as each addition is made.  

 

Even if you do not intend to run the engine, just having it as a display model, you will still want to display to your friends just how smoothly it rotates and may therefore need to run it in by some means to achieve this. If just a very little stiff adding say a large tap wrench to the crankshaft and spending a minute or two turning it by hand may be all that is needed. If though this is proving to be a slow process than driving it from some external source is really the only option.

 

One way of doing this is to add a piece of wood to the cross slide, typically using the top slide fixings, and securing the engine on this using wood screws through the holes in the boxbed.  Place a short length of steel in the three jaw with a piece of rubber tube forced onto it and with that done the cross slide can be used to bring engines fly wheel into contact with the rubber and the lathe started on a low speed, do though turn it a few times by hand to be sure all is OK. After running for a short while it should be found that the engine runs smoothly, Photograph 70 shows the setup.

 

An advantage of the method is that the drive can easily be disconnected by moving the cross slide back for testing the result and then forward again if needing to be run further. A little oil can be placed in the appropriate places to assist in achieving a smooth running engine but do not overdo this as if oil gets onto the castings it may cause a problem at the painting stage.

Stuart 10V steam engine machining

A good method of applying small amounts of oil is to place a very small amount in a bottle cap and use your scriber tip to pick up a droplet then placing it in the required position, a method used by clock makers I believe.

 

The engine should now be dismantled for the finishing stage which is largely divided into two tasks,1. surface finishing for either visual impact or in preparation for painting and 2. painting, just one area going beyond this. The working surface of the slide valve and its mating surface on the cylinder should be lapped on a flat surface using a piece of say 400 grit emery paper, then being finished by progressively using finer grades up to around 1200 grit. The purpose of this is to improve the seal between the two parts when working.

 

Cast iron parts where painted should be tided up removing all irregularities as no mater how much paint you apply they are still likely to show, in fact, with gloss paint, they may even show more. Do not therefore rush over this stage.

 

Areas that are machined but not painted should be surfaced with 400 grit paper, at least sufficient to remove machining marks, the outer rim of the flywheel will though benefit by having an almost a mirror finish using up to 1200 grit and being done whilst it is once more held on the taper stub mandrel and the lathe running. Do take care though you do not want to get your fingers caught in the rotating spokes.

 

One area that needs a little more attention is the valve chest and valve chest cover, having machined them independently it is unlikely that their widths and height will match perfectly. Therefore, assemble them as a pair using the provided studs and lap the sides on a piece of emery paper. The ends will have to be done with needle files and finished with a strip of emery paper.

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