Today's Message Index:
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1. 06:46 PM - Re: Offset pistons in Brand "L," "C" or "F"? (Martin Hone)
2. 07:13 PM - Re: Re: Offset pistons in Brand "L," "C" or "F"? (Nick Otterback)
Message 1
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| Subject: | Re: 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. 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@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@gmail.com
> To: frankroskind@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
>
Message 2
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| Subject: | Re: Offset pistons in Brand "L," "C" or "F"? |
Jabiru uses offset pistons. They way to tell which way they go in the bore i
s 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 o
n 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@gmail.com> wrote:
> Hi Frank,
>
> There has been a lot of discussion on the Jabiru engine list on this subje
ct. It started when someone couldn't work out which way the pistons should b
e 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 m
ore torque, while others 'desax' the bore by offsetting the barrels/cylinder
s relative to the centreline of the crank, ie. moving the cylinders forward o
r backwards a few millimetres in the same plane, not rotating around the cra
nk as in a v-twin or radial. In a motorcycle production racing class I was i
nvolved in, a guy got caught cheating by doing just this. He moved the enti
re cylinder bank on a Suzuki 1000cc four cylinder engine !
>
> Marty
>
>
> On Fri, May 31, 2013 at 11:31 AM, Frank Roskind <frankroskind@hotmail.com>
wrote:
>> Thanks for your response. I have googled offset piston with lycoming, co
ntinental and franklin, but found nothing relevant except a reference to the
Franklin automobile having offset piston pins. After your message I also g
oogled the same three with "desaxed" and found nothing relevant. It seems l
ike a great idea, given all the fooling around with exhausts, intakes and ig
nition, 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@gmail.com
>> To: frankroskind@hotmail.com
>>
>> Frank , this has been discussed at length. Many engine types use offset p
iston pins or 'desaxed' bores. Harleys for example.
>> Try Googling either term.....
>>
>> Marty
>
>
>
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