What is your purpose i designing this valve gear? What do you want to solve?
As David points out, there existed a pleothora of valve gear designs during the developement of steam engines. They all have their merits and compromises.
Perhaps the most obvious example is the Stephenson's valve gear compared to the Allen type, which was designed to specifically give the steam admission cycle a different charracteristic. I'm to tired to recollect the purpose now.
I put the question to ChatGTP "What respective merits and compromises characterises the Stephenson steam engine valve gear compared to the Allen type?"
ChatGTP answered "
The Stephenson valve gear, also known as the "link motion," is a type of valve gear used on steam engines to control the admission of steam into the cylinders. It is characterized by its simplicity and reliability. One of its key advantages is that it can be easily adjusted to compensate for wear on the valve gear and engine components. However, it is not as efficient as other types of valve gear, such as the Walschaerts valve gear, and it can be more difficult to set up and maintain.
The Allen type valve gear is a type of valve gear used on steam engines to control the admission of steam into the cylinders. It is characterized by its efficiency, as it allows the engine to operate at higher speeds and with less steam. One of the main disadvantages of the Allen type is that it is more complex and difficult to set up and maintain compared to the Stephenson type.
In summary, the Stephenson valve gear is simpler and more reliable, but less efficient compared to the Allen type valve gear which is more efficient but also more complex and difficult to maintain."
However, normally I can give you a much shorter and more to the point answer as to the merits of the Allen type valve gear.
Aster has modelled the Preussian small T3 locomotive that was produced in huge numbers beginning in the late 19th century. In spite of the complicated design Allan type valve gear was used. It's fascinating watching the models valve gear work. Photo of Aster model.
A photo of the prototype from Wikipedia.
According to ChatGTP "The Allen valve gear was developed by James Naysmyth Allen in the early 1900s. He first patented the design in 1901, and it was first used on a steam engine in 1903.
The Walschaerts valve gear, also known as the Walschaerts system, was developed by Belgian engineer Egide Walschaerts in 1844. It was first used on a steam engine in 1849, and quickly became popular due to its improved efficiency and ease of adjustment compared to other types of valve gear at the time."
So the first T3 locomotives produced in 1882 (Wikipedia) must have used some other type of valve gear. The advantage of steam economy with the Allen system at greater speeds doesn't make sense as a reason for choosing it for the T3 locomotive design, since I believe maximum allowed operating speed was 30km/h, later raised to 45km/h. (30mph)
Operating the Aster model at some sort of prototypical speed seems to be a true challenge.
Regner made a very simple live steam design of the T3 - later BR89 - with the simplest valve gear I've ever seen. But the valve has no overlap / cut off, and is not reversible. Instead a separate valve is used to reverse the flow of steam to change direction.
I'm not out to put your idea down, but there is an obvious chance your design already exists. Have you checked?
