[SEL] Re: Alamo piston pattern update

[Curt]

Dave,
Your work on both the pattern and corebox looks great! I am looking 
forward to seeing how the paper splits on the pattern. I've spot glued 
mine but have contemplated the paper method.
I believe Rick is busier than a 1 armed wallpaper hanger right now and 
it you want to speed things along, anything you do will help you get 
your part quicker. The design is fairly straight forward from what I've 
been able to research. 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.
Risers are round to minimize surface area. (and also drafted for removal 
when ramming the pattern)  The books tell you the riser's bottom 
diameter should be 125 to 150% of the thickest cross section. However, 
I'm making mine 175% based on the advice of an old timer pattern maker. 
On my pattern the OD is 6" and the crown is 1" in thickness. The gate is 
3/4" long and is 1" x 1" in crosssection, half being in the cope side 
and half being in the drag side. The riser on the cope side is 1 3/4" 
diameter at the parting board. It drafts 1/4"/ft and is 5" tall. The 
cope flask is 5" tall so the riser will be open once rammed. The runner 
from the sprue down button over to the riser is 3/4" x 1".
Looking at the Falk drawings of your piston and core there is .570 
section thickness in the crown. 1.75 x this is .99 so I would make your 
riser an inch or maybe even 1 1/4" at the bottom. You can make the short 
gate 1 x 1 or maybe even 3/4 x 3/4. But bigger is better. For one off 
parts you really don't care about the waste material in the gate/riser 
system. You just want to make sure there is enough mass there to assure 
they freeze off last.
Great photo documentation of your project and thanks for posting.
Curt
P.S. You asked about Alamo pictures....
<http://www.oldengine.org/members/holland/images/Guess/1.jpg>
<http://www.oldengine.org/members/holland/images/Guess/2.jpg>

Dave Otto wrote:

>Hi Curt
>
>Your pattern work is looking great, and as usual I have a question or two.
>Do I need to construct the gate and riser parts on my pattern? Or is this
>something that Rick will do? Were you able to get the proper board size or
>did you just wing it.
>
>I have been getting a little work done on Falk pattern and core box, I'm not
>nearly as quick as you but I will get there eventually.
>
>Pictures at:
>http://community.webshots.com/album/547573772SETaSd
>
>
>Dave
>
>P.S. Still need to see some pics. of the Alamo engine
>
>Dave Otto
>Boise, Id
>USA
>Dotto at velocitus.net
>http://community.webshots.com/user/otto1960
>
>
>
>
>
>  
>
>>-----Original Message-----
>>From: stationary-engine-request at oldengine.org [mailto:stationary-engine-
>>request at oldengine.org] On Behalf Of Curt
>>Sent: Monday, February 13, 2006 11:22 AM
>>To: SEL; SEL (Oldengine.org)
>>Subject: Alamo piston pattern update
>>
>>Guys,
>>Over the weekend I wrapped up the pattern portion of the Alamo piston
>>project. About a week ago I posted pictures of the corebox part of the
>>project and this post covers the pattern portion. About half way down is
>>an update marked 2/13/06. Hope you enjoyed these.
>>Curt Holland
>>Gastonia, NC
>>P.S. Now if Rick can just get the Tod Works Foundry up and going..... :-)
>>
>>http://www.oldengine.org/members/holland/images/AlamoPistonPattern/Thumbna
>>ils.html
>>
>>
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