New to group. Re gaugable shay

[les]

Hi folks I am new to this forum but I have an interesting idea to run by those of you with experience with building these locos.
I am about to embark on building a "New Shay" and I am considering making it a five inch gauge 1 1/2 inch scale, ie: narrow gauge.
In order to accomplish this I am considering placing a spacer disk between the gear and the wheel on the drive side and also one on the non drive side.
I know this will no be prototypical but it would allow the loco to be re gauged to 7 1\2 inch if desired at a later date and would negate the need to change the design of the engine mount and trucks. So any thoughts on this idea would be appreciated especially from people who have built the trucks and can see an obvious difficulty whit this idea.

Regards

Les Andrews

[Ed Hume]

Les,

I'm thinking about the drive shaft. The locomotive looks correct if the drive shaft is straight. If the universal joints have to couple inward or outward for the re-gauged wheels, it starts looking like a kludge. If the joints have to angle too far, the shaft will not turn smoothly. The location of the drive shaft is a big deal design-wise. It is set by the diameter of the boiler, the tilt of the motor, and the mounting of the motor. It is not trivial to move the drive shaft inward or outward to make the loco look correct.

Having said all that, I am thinking you must plan on having the shaft and gears align for the larger gauge of 7.5" and then only the wheels are moved inward for 5". This sounds feasible if the truck appearance is acceptable. You could draw a truck in 3D CAD and look at it and ask yourself if the appearance is acceptable.

With my own work on a gauge 1 model, I have resized the boiler and tilted the motor 5 degrees to have the shaft align for a 3ft NG model. I don't think I would like to see a 1"+ gap between the wheel and the gear on a 5" gauge model. You will have years of work in building the model. Do some detailed drawing up front to make sure you are comfortable with this design change.

Regards,
Ed

[les]

Thanks Ed for you thoughts. I realise it may be a little ugly having the spacer in between the gear and wheel but I think it would be a lot easier than rescaling the entire project to 1" scale ( my garden layout is 5" Gauge). I guess my main concern is if it would be sound engineering wise in terms of strength. Or if it would cause any other problems mechanically or operationally. I Will try to do a cad drawing of the idea although cad is not one of my strong points. I certainly don't want to move the engine or shaft positions. There is a web site here in Aus that shows a 7 1/2" scale 5" gauge scratch built shay and it looks quite good on the track, however the trucks are completely designed to 5" and the shafts and engine mounted accordingly. The web address if you are interested is members.optusnet.com.au/limashay/model.html
Once again many thanks for your interest.

Les