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Offset pistons in Brand "L," "C" or "F"?

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aerobiz1(at)gmail.com
Guest

Posted: Thu May 30, 2013 5:46 pm Post subject: Offset pistons in Brand "L," "C" or "F"?

Hi Frank,



There has been a lot of discussion on the Jabiru engine list on this subject. It started when someone couldn't work out which way the pistons should be fitted. Â Most engines have piston pin offset, mainly to reduce piston slap at TDC hence noise. Â Some racing types reverse it to try and get a little more torque, while others 'desax' the bore by offsetting the barrels/cylinders relative to the centreline of the crank, ie. moving the cylinders forward or backwards a few millimetres in the same plane, not rotating around the crank as in a v-twin or radial. Â In a motorcycle production racing class I was involved in, a guy got caught cheating by doing just this. Â He moved the entire cylinder bank on a Suzuki 1000cc four cylinder engine !

 



Marty



On Fri, May 31, 2013 at 11:31 AM, Frank Roskind <frankroskind(at)hotmail.com (frankroskind(at)hotmail.com)> wrote:

 [quote]   Thanks for your response. Â I have googled offset piston with lycoming, continental and franklin, but found nothing relevant except a reference to the Franklin automobile having offset piston pins. Â After your message I also googled the same three with "desaxed" and found nothing relevant. Â It seems like a great idea, given all the fooling around with exhausts, intakes and ignition, it is kind of odd that I am not reading of anyone who took a shot at offsetting the pistons.

 Â Maybe I just found a great retirement occupation.

Date: Fri, 31 May 2013 06:58:04 +1000

Subject: Re: Offset pistons in Brand "L," "C" or "F"?

From: aerobiz1(at)gmail.com (aerobiz1(at)gmail.com)

 To: frankroskind(at)hotmail.com (frankroskind(at)hotmail.com)



Frank , this has been discussed at length. Â Many engine types use offset piston pins or 'desaxed' bores. Harleys for example. Try Googling either term.....

 Marty

 		 	   		  



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vettin74(at)yahoo.com
Guest

Posted: Thu May 30, 2013 6:13 pm Post subject: Offset pistons in Brand "L," "C" or "F"?

Jabiru uses offset pistons. They way to tell which way they go in the bore is by a mark on the piston face. Either an arrow(new engines) or a very small half moon shaped indent  which denote the end of the engine with the prop on it.

Maybe that was overed didnt see it in his thread.

Thanks

Nick 



Sent from my pocket 

On May 30, 2013, at 8:45 PM, Martin Hone <aerobiz1(at)gmail.com (aerobiz1(at)gmail.com)> wrote:

[quote]Hi Frank,



There has been a lot of discussion on the Jabiru engine list on this subject. It started when someone couldn't work out which way the pistons should be fitted.  Most engines have piston pin offset, mainly to reduce piston slap at TDC hence noise.  Some racing types reverse it to try and get a little more torque, while others 'desax' the bore by offsetting the barrels/cylinders relative to the centreline of the crank, ie. moving the cylinders forward or backwards a few millimetres in the same plane, not rotating around the crank as in a v-twin or radial.  In a motorcycle production racing class I was involved in, a guy got caught cheating by doing just this.  He moved the entire cylinder bank on a Suzuki 1000cc four cylinder engine !

 



Marty



On Fri, May 31, 2013 at 11:31 AM, Frank Roskind <frankroskind(at)hotmail.com (frankroskind(at)hotmail.com)> wrote:

  	  Quote: 	
		     Thanks for your response.  I have googled offset piston with lycoming, continental and franklin, but found nothing relevant except a reference to the Franklin automobile having offset piston pins.  After your message I also googled the same three with "desaxed" and found nothing relevant.  It seems like a great idea, given all the fooling around with exhausts, intakes and ignition, it is kind of odd that I am not reading of anyone who took a shot at offsetting the pistons.

  Maybe I just found a great retirement occupation.

Date: Fri, 31 May 2013 06:58:04 +1000

Subject: Re: Offset pistons in Brand "L," "C" or "F"?

From: aerobiz1(at)gmail.com (aerobiz1(at)gmail.com)

 To: frankroskind(at)hotmail.com (frankroskind(at)hotmail.com)



Frank , this has been discussed at length.  Many engine types use offset piston pins or 'desaxed' bores. Harleys for example. Try Googling either term.....

 Marty

 		 	   		  



 



===================================

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BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Fri May 31, 2013 5:10 am Post subject: Offset pistons in Brand "L," "C" or "F"?

Marty:



I do not know about Suzuki or Harley - But I do know about Lycoming and Continental - They DO NOT HAVE ANY PISTON OFFSET.  

I know of NO reason to have the wrist pin offset - It just does NOT make ANY sense at all.  There are Front & Rear to some pistons but that is because of piston dome designs and valve clearances.  

 Think of it this way:  What CENTERS the piston in the center of the cylinder?

THE RINGS!!!

So, how or why would there be a wrist pin offset?

If there was piston pin offset, then the rings would be offset also - And that would lead to uneven wear and loss of compression.

 Whomever started this Wives Tail should be SHOT with Dumb-Dumbs because it would match their intellect..  Always REMEMBER B.S. is spread at the speed of an electron on the internet.  

 

Barry  

"Do you know why pilots think they are mechanics?  Because they can but tools at Home Depot."



 



On Thu, May 30, 2013 at 9:45 PM, Martin Hone <aerobiz1(at)gmail.com (aerobiz1(at)gmail.com)> wrote:

[quote] Hi Frank,



There has been a lot of discussion on the Jabiru engine list on this subject. It started when someone couldn't work out which way the pistons should be fitted.  Most engines have piston pin offset, mainly to reduce piston slap at TDC hence noise.  Some racing types reverse it to try and get a little more torque, while others 'desax' the bore by offsetting the barrels/cylinders relative to the centreline of the crank, ie. moving the cylinders forward or backwards a few millimetres in the same plane, not rotating around the crank as in a v-twin or radial.  In a motorcycle production racing class I was involved in, a guy got caught cheating by doing just this.  He moved the entire cylinder bank on a Suzuki 1000cc four cylinder engine !

  



Marty



On Fri, May 31, 2013 at 11:31 AM, Frank Roskind <frankroskind(at)hotmail.com (frankroskind(at)hotmail.com)> wrote:

   	  Quote: 	
		     Thanks for your response.  I have googled offset piston with lycoming, continental and franklin, but found nothing relevant except a reference to the Franklin automobile having offset piston pins.  After your message I also googled the same three with "desaxed" and found nothing relevant.  It seems like a great idea, given all the fooling around with exhausts, intakes and ignition, it is kind of odd that I am not reading of anyone who took a shot at offsetting the pistons.

   Maybe I just found a great retirement occupation.

Date: Fri, 31 May 2013 06:58:04 +1000

Subject: Re: Offset pistons in Brand "L," "C" or "F"?

From: aerobiz1(at)gmail.com (aerobiz1(at)gmail.com)

  To: frankroskind(at)hotmail.com (frankroskind(at)hotmail.com)



Frank , this has been discussed at length.  Many engine types use offset piston pins or 'desaxed' bores. Harleys for example.  Try Googling either term.....

 Marty

 		 	   		  



 	
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matronics(at)rtist.nl
Guest

Posted: Fri May 31, 2013 7:17 am Post subject: Offset pistons in Brand "L," "C" or "F"?

Barry, before lashing out like this and having people shot for     sending information, perhaps you should read up on Piston slap.

     

     If it were an old wives tail, then no engine manufacturer would     bother to put an orientation in their manual, don't you think?

     

     

     On 5/31/2013 3:09 PM, FLYaDIVE wrote:

     

     [quote]Marty:       

       

       I do not know about Suzuki or Harley - But I do know about         Lycoming and Continental - They DO NOT HAVE ANY PISTON OFFSET.  

       I know of NO reason to have the wrist pin offset - It just         does NOT make ANY sense at all.  There are Front & Rear to         some pistons but that is because of piston dome designs and         valve clearances.  

       Think of it this way:  What CENTERS the piston in the center         of the cylinder?

       THE RINGS!!!

       So, how or why would there be a wrist pin offset?

       If there was piston pin offset, then the rings would be         offset also - And that would lead to uneven wear and loss of         compression.

       Whomever started this Wives Tail should be SHOT with         Dumb-Dumbs because it would match their intellect..  Always         REMEMBER B.S. is spread at the speed of an electron on the         internet.  

                                        

           

                        

Barry             

"Do you know why pilots think they are mechanics?                  Because they can but tools at Home Depot."           

         

         

         

         On Thu, May 30, 2013 at 9:45 PM, Martin           Hone <aerobiz1(at)gmail.com (aerobiz1(at)gmail.com)>           wrote:

            	  Quote: 	
		               Hi Frank,               

               

               There has been a lot of discussion on the Jabiru                 engine list on this subject. It started when someone                 couldn't work out which way the pistons should be                 fitted.  Most engines have piston pin offset, mainly to                 reduce piston slap at TDC hence noise.  Some racing                 types reverse it to try and get a little more torque,                 while others 'desax' the bore by offsetting the                 barrels/cylinders relative to the centreline of the                 crank, ie. moving the cylinders forward or backwards a                 few millimetres in the same plane, not rotating around                 the crank as in a v-twin or radial.  In a motorcycle                 production racing class I was involved in, a guy got                 caught cheating by doing just this.  He moved the entire                 cylinder bank on a Suzuki 1000cc four cylinder engine !

               

               

               Marty

             

             

               

               On Fri, May 31, 2013 at 11:31 AM,                 Frank Roskind <frankroskind(at)hotmail.com (frankroskind(at)hotmail.com)>                 wrote:

                  	  Quote: 	
		                                          Thanks for your response.  I have                       googled offset piston with lycoming, continental                       and franklin, but found nothing relevant except a                       reference to the Franklin automobile having offset                       piston pins.  After your message I also googled                       the same three with "desaxed" and found nothing                       relevant.  It seems like a great idea, given all                       the fooling around with exhausts, intakes and                       ignition, it is kind of odd that I am not reading                       of anyone who took a shot at offsetting the                       pistons.

                        Maybe I just found a great retirement occupation.

                                                Date: Fri, 31 May 2013 06:58:04 +1000

                         Subject: Re: Offset pistons in Brand "L," "C" or                         "F"?

                         From: aerobiz1(at)gmail.com (aerobiz1(at)gmail.com)

                         To: frankroskind(at)hotmail.com (frankroskind(at)hotmail.com)

                         

                         Frank , this has been discussed                           at length.  Many engine types use offset                           piston pins or 'desaxed' bores. Harleys for                           example.                                                        Try Googling either term.....

                           

                           

                                                        Marty

                         

                       

                     

                   

                 

	
           

	
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zeprep251(at)aol.com
Guest

Posted: Fri May 31, 2013 4:57 pm Post subject: Offset pistons in Brand "L," "C" or "F"?

http://www.motorcycleproject.com/motorcycle/text/cows-offset.html

 

  

     You might try this page for some insight into pin off set before you start calling people names. 

  

     

  

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Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Sat Jun 01, 2013 2:33 am Post subject: Offset pistons in Brand "L," "C" or "F"?

Easy, big boy, easy....



Nobody says that the pistons are off-center....where did you get THAT  

idea??  It is the piston pins that are offset in SOME pistons, used  

in SOME applications, in SOME engines.

The pin offset is done to change the angle that the connecting rod  

makes with the crankshaft during part of the cycle. It is also there  

to change the relationship of the piston within the cylinder bore at  

certain times, to make the engine quieter....this "noise" being the  

so-called "piston slap" that occurs when the piston skirt hits the  

cylinder wall near the top of its stroke. These are simplified  

explanations of why there is piston pin offset. No point in trying to  

explain it any further...I wouldn't know how, and it might not be  

understood if I did.



Lynn Matteson

 	  Quote: 	
		   Kitfox IV Speedster, taildragger

 Jabiru 2200, #2062

 Prince prop 64 x 30, P-tip

 Electroair direct-fire ignition system

 Rotec TBI-40 injection (sleeved to 36mm)

 Status: flying with 1445 hrs... (since 3-27-2006)


	


On May 31, 2013, at 9:09 AM, FLYaDIVE wrote:



 	  Quote: 	
		   Marty:



 I do not know about Suzuki or Harley - But I do know about Lycoming  

 and Continental - They DO NOT HAVE ANY PISTON OFFSET.

 I know of NO reason to have the wrist pin offset - It just does NOT  

 make ANY sense at all.  There are Front & Rear to some pistons but  

 that is because of piston dome designs and valve clearances.

 Think of it this way:  What CENTERS the piston in the center of the  

 cylinder?

 THE RINGS!!!

 So, how or why would there be a wrist pin offset?

 If there was piston pin offset, then the rings would be offset also  

 - And that would lead to uneven wear and loss of compression.

 Whomever started this Wives Tail should be SHOT with Dumb-Dumbs  

 because it would match their intellect..  Always REMEMBER B.S. is  

 spread at the speed of an electron on the internet.

 Barry



 "Do you know why pilots think they are mechanics?  Because they can  

 but tools at Home Depot."



 On Thu, May 30, 2013 at 9:45 PM, Martin Hone <aerobiz1(at)gmail.com>  

 wrote:

 Hi Frank,



 There has been a lot of discussion on the Jabiru engine list on  

 this subject. It started when someone couldn't work out which way  

 the pistons should be fitted.  Most engines have piston pin offset,  

 mainly to reduce piston slap at TDC hence noise.  Some racing types  

 reverse it to try and get a little more torque, while others  

 'desax' the bore by offsetting the barrels/cylinders relative to  

 the centreline of the crank, ie. moving the cylinders forward or  

 backwards a few millimetres in the same plane, not rotating around  

 the crank as in a v-twin or radial.  In a motorcycle production  

 racing class I was involved in, a guy got caught cheating by doing  

 just this.  He moved the entire cylinder bank on a Suzuki 1000cc  

 four cylinder engine !



 Marty

 On Fri, May 31, 2013 at 11:31 AM, Frank Roskind  

 <frankroskind(at)hotmail.com> wrote:

 Thanks for your response.  I have googled offset piston with  

 lycoming, continental and franklin, but found nothing relevant  

 except a reference to the Franklin automobile having offset piston  

 pins.  After your message I also googled the same three with  

 "desaxed" and found nothing relevant.  It seems like a great idea,  

 given all the fooling around with exhausts, intakes and ignition,  

 it is kind of odd that I am not reading of anyone who took a shot  

 at offsetting the pistons.

  Maybe I just found a great retirement occupation.

 Date: Fri, 31 May 2013 06:58:04 +1000

 Subject: Re: Offset pistons in Brand "L," "C" or "F"?

 From: aerobiz1(at)gmail.com

 To: frankroskind(at)hotmail.com



 Frank , this has been discussed at length.  Many engine types use  

 offset piston pins or 'desaxed' bores. Harleys for example.

 Try Googling either term.....



 Marty

 www.matronics.com/contribution _- 

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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

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