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new gas pipes under construction


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#106 Terry Keeley

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Posted 03 August 2018 - 07:30 AM

Whew!  At least you're starting with tube.

 

Jennings says basically what you just said about different baffle cones on that pg. 62., I have found the same.  I look for pipes that have sharp baffle cones, they add mph!  Irwin's pipes all had sharp baffles.  :)





#107 LohringMiller

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Posted 03 August 2018 - 08:14 AM

I've always had a hard time making rolled sheet pipes accurately enough in our small sizes.  A comparison between a billet pipe and a rolled sheet version showed significant power loss.   Below is a test of a billet pipe, a Need for Speed pipe and a fabricated version of the billet pipe on a stock Zenoah.  The billet pipe is pictured.  It has a variable position baffle cone  we used in another series of test to look at changes in header length versus tuned length.

 

Lohring Miller

 

Attached File  Fab vs Billet Pipes.jpg   63.71KB   2 downloads Attached File  B&M pipe.JPG   31.72KB   2 downloads

 

 





#108 Jim Allen

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Posted 05 August 2018 - 04:00 AM

Rolling tapered cones on a roller with straight rollers requires some practice. There are rollers with tapered rollers, but they are very expensive! The accuracy of the finished piece  always depends on how accurate the flat sheet metal piece is. .016"  to .020" material works the best. I spot weld rolled pieces to prevent any movement when silver soldering the linear joint. One thing to consider is the fact that the OD of the rollers determines the smallest ID that can be rolled. A taper attachment for a lathe saves much time when cutting longer tapered pieces.

 

Jim Allen

 

 

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#109 Jim Allen

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Posted 07 August 2018 - 01:34 PM

I use a computer program to accurately determine the exact shape of each section to be rolled. Heavy paper is used before cutting any metal to insure the pieces will fit together. An extra .050" of material is added where necessary to provide a good silver solder joint. Notice how any tapered section needs to be twisted as it is being rolled. This technique takes some practice.

 

Jim Allen

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  • Attached File  001.JPG   77.41KB   3 downloads
  • Attached File  002.JPG   75.6KB   2 downloads
  • Attached File  003.JPG   64.18KB   2 downloads
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#110 Jim Allen

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Posted 15 August 2018 - 02:23 PM

It's interesting to see the performance differences that are possible when small changes are made to similar type tuned pipes, which are being used on the same 26 & 27 cc size rear exhaust engines. The three pipes shown have different power curves, different peak HP amounts, different peak HP band widths & different over-rev characteristics. I believe all shown could be applied to oval type racing.

 

Jim Allen

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Edited by Jim Allen, 15 August 2018 - 02:26 PM.


#111 Rudy Formanek

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Posted Yesterday, 01:23 PM

Did you run these on a dyno?? or on the water??



#112 Jim Allen

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Posted Today, 01:38 PM

Did you run these on a dyno?? or on the water??


Rudy,

I run everything on the dyno & then on the water. Sometimes the effect of small changes on things such as taper angle, section length, inside diameter, tuned pipe volume, stinger ID & length, header ID & angle & major diameter cannot not be seen on the water.

JA