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 Piston travel vs crank rotation

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Jimmie



Number of posts : 133
Registration date : 2011-07-25

PostSubject: Piston travel vs crank rotation   Sun Jun 24, 2012 7:35 am

Came across this 'tool'. I assume it is only one of many. Can anyone say how accurate it is?

http://john.rushworth.com/Pics/Piston/
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johnSbantam

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Number of posts : 254
Localisation : New Zealand
Registration date : 2006-12-01

PostSubject: Re: Piston travel vs crank rotation   Sun Jun 24, 2012 9:17 am

looks spot on to me. Gives exactly the same results as formulae from Bell's book.
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mick abbey



Number of posts : 7
Age : 52
Localisation : Harrogate
Registration date : 2011-08-11

PostSubject: Re: Piston travel vs crank rotation   Thu Jun 28, 2012 9:12 pm

Yes it is spot on I have done a quick test with it and it is right

Mick
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mick abbey



Number of posts : 7
Age : 52
Localisation : Harrogate
Registration date : 2011-08-11

PostSubject: Re: Piston travel vs crank rotation   Thu Jun 28, 2012 9:13 pm

Yes it is spot on I have done a quick test with it and it is right

Mick
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Jimmie



Number of posts : 133
Registration date : 2011-07-25

PostSubject: Re: Piston travel vs crank rotation   Thu Jun 28, 2012 10:55 pm

How do I calculate timings for an exhaust port which ‘opens’ say, 40mm below the top of the barrel (62 bore and 125 rod). According to the chart this gives a timing of 100 degrees. Do I subtract this 100 from 180 and the double it, ie 80 x 2 =160 degrees exhaust timing?
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mscutt

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Registration date : 2011-10-21

PostSubject: Re: Piston travel vs crank rotation   Fri Jun 29, 2012 1:09 am

Hi Jimmie

Yes you are thinking on the right lines to calculate total opening angle for an exhaust port.

I guess you intended to say 62mm stroke rather than 62mm bore?

For a 175 Bantam with 58mm stroke and 125mm rod length then 40mm after tdc is about 105.7 degrees after tdc so the total opening works out at 148.6 deg.

The web page takes no account of any gudeon pin offset but for most pistons its between 0 and 1mm so only makes about 0.1 degrees difference to the opening and closing times and the total opening remains much the same.

Mick
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Jimmie



Number of posts : 133
Registration date : 2011-07-25

PostSubject: Re: Piston travel vs crank rotation   Fri Jun 29, 2012 3:40 am

Thanks Mick. Them hard sums are really hard!

Jim
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