Sep 2012
Panhard bare cylinder isn't tapered
Saturday 15 September 2012 Filed in: Blog Comments
Panhard liners have had tapered bores since the early days. However when it’s time to rebuild them, I never found this out.
It was assumed by others, and I had no reason to question whether the liner was tapered internally, or perhaps the aluminium cylinder itself? The reasoning behind this was, if the aluminium cylinder was slightly narrower at the combustion chamber end, it would squeeze the sleeve and so make it tapered.
Yesterday, I got a Tesa three point bore micrometer in the post, and I was finally able to measure the internal bore of the aluminium cylinder.
I measured the bottom, middle and top of the bore of the bare aluminium cylinder, that’s without a liner or sleeve being fitted.
The divisions of the micrometer are 0.0002” or 2/10ths of a thou. There is no taper on the bare cylinder, so thats’s another bit of folklore or legend out of the way, and the only other way to achieve this would be to make the internal sleeve or cast iron liner taper outwards at the top, so that when it is inserted in the heated cylinder, upon cooling it compresses slightly more at the top than the bottom. Next up is to measure a few sleeves or liners and check whether this was done.
Interestingly the days of tapered bores were numbered with improvements in aluminium piston alloys and better machining, and Panhards have bigger issues with their piston design, so obsessing about having a tapered bore is rather irrelevant and futile.
UPDATE 23 September 2012
I measured the matching sleeve, taken from the aluminium cylinder above, and the external diameters are truly parallel, so I now know I will not have any issues when I bore the cylinder liner or sleeve.
It was assumed by others, and I had no reason to question whether the liner was tapered internally, or perhaps the aluminium cylinder itself? The reasoning behind this was, if the aluminium cylinder was slightly narrower at the combustion chamber end, it would squeeze the sleeve and so make it tapered.
Yesterday, I got a Tesa three point bore micrometer in the post, and I was finally able to measure the internal bore of the aluminium cylinder.
I measured the bottom, middle and top of the bore of the bare aluminium cylinder, that’s without a liner or sleeve being fitted.
The divisions of the micrometer are 0.0002” or 2/10ths of a thou. There is no taper on the bare cylinder, so thats’s another bit of folklore or legend out of the way, and the only other way to achieve this would be to make the internal sleeve or cast iron liner taper outwards at the top, so that when it is inserted in the heated cylinder, upon cooling it compresses slightly more at the top than the bottom. Next up is to measure a few sleeves or liners and check whether this was done.
Interestingly the days of tapered bores were numbered with improvements in aluminium piston alloys and better machining, and Panhards have bigger issues with their piston design, so obsessing about having a tapered bore is rather irrelevant and futile.
UPDATE 23 September 2012
I measured the matching sleeve, taken from the aluminium cylinder above, and the external diameters are truly parallel, so I now know I will not have any issues when I bore the cylinder liner or sleeve.
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