I've spent a number of days now working in the dockstader simulator, trying to improve the joy valve gear on the Clayton.
Are there any helpful hints that anyone could provide on laying out joy valve gear that may prove helpful?
So far I've found that with the straight slides the simulator simply won't process the data, and I get error messages all over. I therefore changed the slides to a radius equal to the radius rod that connects to the valve rod. Also after checking my dimensions a couple times to the drawings the crank rod needed increasing by 1/8" so that the piston would travel the full length of the cylinder. This can be achieved by changing the rear bearing to a slightly larger one and offsetting the bearing hole, therefore increasing the length of the connecting rod. I believe this error has crept into the drawing as the rear cylinder cover width (1/8"
has not been included when the valve gear was schemed out by Dyer.
These dimensions I've checked twice against the drawings, and I'm surprised that any clayton wagon is running. I'd be interested to hear from builders of the Clayton if they found this error or worked around it somehow?
By changing the above dimensions, resulted in the valve having a cut off in forward gear of 54.6% front port and 99% rear port, and in reverse the front steam port not having any access to steam inlet and the rear 97%. Also that the valve would overshoot the valve chest wall by a small margin. Therefore I have reduced the valve stem centre to centre length to 3.825" instead of the 3.975" as shown on the drawings.
This has shown a great improvement in the simulations I've run, even allowing for expansion of the steam which the joy gear is supposed to be so great for. Comparison with the above changes are as follows;
Forward gear;
Front steam port 82% cut off
Rear steam port 87% cut off
Reverse gear
Front steam port 89.1% cut off
Rear steam port 90.5% cut off
Notched up a little to midway between full forward and centre position
Forward gear
Front steam port 48.7%
Rear steam port 59.9%
Reverse Gear
Front steam port 52%
Rear steam port 73%
Still a long way to go but vast improvements.
Any help and input would be appreciated.
Jon