[SEL] Re: Alamo piston pattern update

[jbcast at charter.net]

---- Curt <curt at imc-group.com> wrote: 

. The riser's purpose is to provide molten metal to 
> the casting as it cools and the metal shrinks. On your piston for 
> example, you want to bring metal in at the crown. Once filled the 
> casting should begin to solidify from the skirt moving toward the crown. 
> The riser is attached to the largest section thickness thru a short 
> gate. The gate and riser need to be sized such that they will freeze off 
> last. This ensures molten metal can continue to flow into the crown as 
> the rest of the piston cools and shrinks.
 
Curt, have you had any problems with shrinkage in the pin boss area? I made a pattern and had some pistons cast, we had to add risers to supply the pin boss, the first one sunk in on both sides of the piston at the boss. 
J.B. Castagnos