Setting the valve gear ….

Well as the videos below demonstrate we have the valve gear finished, and I managed to time it reasonably. There is some blowby on the HP, and that might need further investigation, but on the whole it’s OK.

I scratched my head a lot on how to set this gear, and while this might not be the “right way” and the setting is certainly not “perfect” – let me tell you how I did this….

Firstly we set the engine up so I could feed each cylinder from compressed air, with “ball-a-fix” valves to allow me to control the amount of flow, and which cylinder is fed. Also fitted a small pressure regulator to allow me to control the pressure fed to the engine.

This set up allowed me to turn the engine over by hand and feel when the air pressure was assisting or hindering this turning, and thereby determine if the gear was feeding the pressure at the right part of the stroke. Then one could simply say “is the gear ahead of the crank position?” (e.g. the air is being fed too soon, or cut off too soon), OR “is the gear behind the crank” (e.g. the air is being fed too late). It was then quite simple to slack off the allen screw locking the eccentric to the crank, use the key to hold the eccentric in place, and manually move the crank ahead or behind (forwards or backwards) to attempt to correct the error. I did this first in full-forward gear and then repeated the same process for the HP  cylinder, and then in full reverse (setting the relevant eccentrics).

Three or four iterations produced the results shown below…

Firstly running in (very) slow forwards

Secondly, a “video tour” providing a more detailed view of the various components?

4 thoughts on “Setting the valve gear ….

  1. John

    You will be doing well if you can go fast enough to skim! Can’t be too far out if it will run that slowly. One good test is to see if it will run notched up with a higher pressure, eg short cutoff.
    I actually set the valves on my one purely by measurement, but did a sanity check with air blowing through and the drain cocks open. Since mine has piston valves at both ends you can’t check the port openings with a cover off as you might on a slide valve job. I must have got it about right since it will run slow and will also run with very short cutoff.
    I have made a locomotive style reverser for mine eg the American style with a lever and quadrant, not the British style screw reverser, since on a small boat it may be desirable at times to reverse at short notice. You don’t want to be fiddling round with locking screws when the wharf is trying to ram you.

    1. sybefur Post author

      time will tell! (on the valve setting)… I agree with you about the reverser, the locking clamp on mine can be flicked off and on, or set to just provide some stiffness – I agree a quadrant would be nice, i was just feeling lazy! Maybe later…


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