On line head volume calculator.

[Terry Keeley]

Was making a coupla .21 heads and came across this cool calculator:

http://www.ambrsoft.com/TrigoCalc/Sphere/Cap/SphereCap.htm

Under "Spherical Cap" enter the volume you want in cc's under "Cap volume", then enter 1/2 your end mill diameter in centimeters (inch x 2.54 = centimeters) into "Sphere radius - R", and wala, it tells you how far to plunge the mill (Cap height - h)

In my case I wanted 0.13cc and I used a 3/8" ball end mill. So 0.187 x 2.54 = 0.475 cm. Cap height is 0.34 cm / 2.54 = 0.134" to plunge. I checked and it was right on.

Yup, they're small. With the 0.01cc dish in the piston it puts the trapped C/R right at 15:1.

I'm gonna try it, I got some fast guys to catch in Mt. Vernon this summer.

 

[the german]

Was making a coupla .21 heads and came across this cool calculator:

http://www.ambrsoft.com/TrigoCalc/Sphere/Cap/SphereCap.htm

Under "Spherical Cap" enter the volume you want in cc's under "Cap volume", then enter 1/2 your end mill diameter in centimeters (inch x 2.54 = centimeters) into "Sphere radius - R", and wala, it tells you how far to plunge the mill (Cap height - h)

In my case I wanted 0.13cc and I used a 3/8" ball end mill. So 0.187 x 2.54 = 0.475 cm. Cap height is 0.34 cm / 2.54 = 0.134" to plunge. I checked and it was right on.

Yup, they're small. With the 0.01cc dish in the piston it puts the trapped C/R right at 15:1.

I'm gonna try it, I got some fast guys to catch in Mt. Vernon this summer.

Terry

Thank's for sharing !!!!!!!!!!!!

Alex

 

[Terry Keeley]

You could even use it to calculate squish band percentage.

Using the "Cap base radius - r" figure out the area of the bowl. In my case 0.45 cm or 4.5 mm. 3.14 (pi) x 4.5 squared = 63.59

The area of the entire bore is: 3.14 x 8.2 squared (1/2 the bore) = 211.13

Subtract the area of the bowl from the total area to get the squish area: 211.13 - 63.59 = 147.54

Divide the squish area into the total area for the squish ratio: 147.54 / 211.13 = 0.699

Call it 70%.

 

[warlokboats]

Terry

Do you always make a flat squish with NO angle on your head buttons?

 

[Terry Keeley]

Terry

Do you always make a flat squish with NO angle on your head buttons?

Lately I have, apparently a flat squish band and sharp bowl to squish corner is the best to increase turbulence and squish velocity.

I've also learned from my SAW testing that crazy high (until now) C/R's can work if you feed it lots of fuel. To burn that fuel you need to run a hot plug and cut back on the water. If you tune to it (more prop, shorter pipe) you can go faster even tho the motor sounds like it's 4 cycling occasionally.

I forgot to include the squish area in my 15:1 calculation, with 0.010" head clearance it's actually about 14.7:1. The latest VAC 45's come in around 13.7:1.

 

[warlokboats]

Very interesting. Thanks for the share Terry . Gonna have to try some things.

So what volume are you trying for in a total cc including the plug?

 

[Mike Hughes]

Cool. Bookmark now. Much better than the old cut it, measure, cut it again, measure, cut it one last time, **** IT, too much.

Thanks

Mike

 

[Ray Sametz]

Cool. Bookmark now. Much better than the old cut it, measure, cut it again, measure, cut it one last time, **** IT, too much.

Thanks

Mike

Been there done that.

 

[Terry Keeley]

Very interesting. Thanks for the share Terry . Gonna have to try some things.

So what volume are you trying for in a total cc including the plug?

Looking for 0.13cc plus there's a 0.01cc dish in the piston. Plus the volume in a 0.010" squish band but that will shrink as the piston heats up and grows.

To be absolutely correct you should probably use the "Spherical segment" as the top of the chamber is actually flat with the plug (unless you're using a turbo plug). Then you'd havta add the volume of the plug hole.

I just used the total volume figuring the bit lost for the flat top would be made up by the plug hole and when I measured with a plug in it was right on.