accurately measuring port cross section area

[gmrocket]

i mentioned in another post about using a planimeter to accurately calculate a section area without having to go through a bunch of guessing or pouring a mold of the port and cutting it up after ,,especially if its an odd shape. ithink it was Gary C heads thread? tried to load a vid but no go so pic will have to do

first i use a soft piece of solder to make a copy of the port shape...this is an ex exit but any part of the port is just as easy,,,even if you have an odd shape in the bowl area or just before the shot turn
then i trace it on some paper and mark a starting point

thumbnail_IMG_5922.jpg

crosshairs.jpg

thumbnail_IMG_7199.jpg

then follow the traced line with the cross hairs in the magnifying end piece

follow the outline around until i get to the starting point and then read what the area is on the display

thumbnail_IMG_7192.jpg

the read is 1253.4 sq mm which is 1.90 sq inches

[gmrocket]

well that didnt come out right...the last pic was suppose to be the second one...

[MadBill]

Beats tracing it on 1/4" graph paper and going blind counting the squares..

[GARY C]

Very cool, thanks for sharing.

[gmrocket]

The planimeter was $30 on eBay

[4vpc]

I like that gadget, thanks for posting.
You wouldn't stand much chance of getting a solder ring around the min csa of a 4v port though. Although on that note what i've recently started doing is hacking up old molds which I don't need anymore into small bits and putting them in a new port along with the liquid silicone to bulk them up, I don't use half as much now.

[RevTheory]

Right on. Thanks!

[MadBill]

For odd shapes, I use cardboard on long 10-32 'handles' to make upper and lower (or L-R) half patterns at one or more candidate MCA locations. (The partials are easier to fit and can be joined when complete.) I then compare results to find the actual minimum area.

[GARY C]

Could you use the solder method on an odd shape and then just reshape it to a triangle for normal measurement as long as the solder is formed with ends butted?

I am guessing y'all have probably already seen this free program. viewtopic.php?f=1&t=51198

[MadBill]

Could you use the solder method on an odd shape and then just reshape it to a triangle for normal measurement as long as the solder is formed with ends butted?..

No. The shape affects the area. E.g. a 6" length of solder will enclosed a circle of 1.9" diameter with an area of 2.84"² or a 0.001" x 3.0" 'rectangle' of ~zero "² area.

[GARY C]

Could you use the solder method on an odd shape and then just reshape it to a triangle for normal measurement as long as the solder is formed with ends butted?..

No. The shape affects the area. E.g. a 6" length of solder will enclosed a circle of 1.9" diameter with an area of 2.84"² or a 0.001" x 3.0" 'rectangle' of ~zero "² area.

I figured it couldn't be that simple... What if I use the governments math?

[gmrocket]

Could you use the solder method on an odd shape and then just reshape it to a triangle for normal measurement as long as the solder is formed with ends butted?..

No. The shape affects the area. E.g. a 6" length of solder will enclosed a circle of 1.9" diameter with an area of 2.84"² or a 0.001" x 3.0" 'rectangle' of ~zero "² area.

Correct.

[gmrocket]

Could you use the solder method on an odd shape and then just reshape it to a triangle for normal measurement as long as the solder is formed with ends butted?..

No. The shape affects the area. E.g. a 6" length of solder will enclosed a circle of 1.9" diameter with an area of 2.84"² or a 0.001" x 3.0" 'rectangle' of ~zero "² area.

I figured it couldn't be that simple... What if I use the governments math?

Ya, the new discovery math won't work.

[GARY C]

No. The shape affects the area. E.g. a 6" length of solder will enclosed a circle of 1.9" diameter with an area of 2.84"² or a 0.001" x 3.0" 'rectangle' of ~zero "² area.

I figured it couldn't be that simple... What if I use the governments math?

Ya, the new discovery math won't work.

[af2]

No. The shape affects the area. E.g. a 6" length of solder will enclosed a circle of 1.9" diameter with an area of 2.84"² or a 0.001" x 3.0" 'rectangle' of ~zero "² area.

I figured it couldn't be that simple... What if I use the governments math?

Ya, the new discovery math won't work.

Yep it does eventually.... LOL