TECHNICAL INFORMATION PLEASE.
I have found that the Hornby live steam engine unit is very sensitive to the steam temperature.
It will run on compressed air and super heated steam but not on saturated steam.
I guess the reason for this is the steam ports in the valve block are so small they act as condensers .
Any dry saturated steam is condensed in to water before it can reach the cylinders.
The slightest reduction in the temperature of the super heater results in a rapid loss of power.
Has anyone increased the super heater temperature to see if this improves the performance of the engine ?
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Hi Adrian,
Many thanks for your response and pleased to see that you talk student Engineers.
The performance of the Hornby engine is very good as produced.
However the rotary valve acts as a throttle to the steam due to the minute steam ports in the rotary valve block.
The steam admission to the cylinders is about 80 % of the piston stroke hence needs to be reduced to say 60% of the stroke to allow the expansive power of the steam to produce useful work and not wasted.
The steam temperature as it leaves the boiler is about 135 decrees centigrade.
The super heater runs at about 250 degrees centigrade or less depending on the electrical power pick up . Ie dirty rails and wheels will cause a fall off of the super heater temperature which results in a fall off of the performance of the engine.
The steam temperature as admitted to the cylinders seems to be about 140 degrees centigrade which is good for a tiny engine.
There is no doubt that if the rotary valve was replaced by the age old slide valve and eccentric the Hornby engine would be improved in performance and above all simplify the setting of the valve timing.
It would be interesting if you ask the student engineers how they would improve the tiny Hornby engine.