Jim B. asked about substitutes for the O-ring used in the winders and MD's. I
had a look into this some time ago, and here are some notes I made at the time.
Here is a quote from an O-ring website:
>>
There is a bewildering difference between the American inch system for o-rings
and the metric system. The American inch system is tightly organized and has
119 inside diameters (ID) and 5 cross sections (c/s), resulting in 349 o-ring
combinations recognized as standard sizes, and known as "DASH NUMBERS." The
metric system is looselyorganised and has few internationally recognised
standard sizes. It is estimated that there are roughly 15,000 reasonably
available sizes in the metric o-ring range. Each metric country has a range of
sizes that represents an abbreviated version of a standard size range for that
country.
<<
AND:
>>
The principal difference between the two measuring systems for O-rings is that
inch sized O-rings have an actual size that is always larger than the nominal
size. For example, an O-ring with a 1/8" c/s should measure .125", but
actually measures .139". Metric O-rings have an actual size and a nominal size
that are the same. For example, a metric O-ring with a nominal size of 3.5mm
will actually measure 3.5mm.
<<
The reason the US size is larger than specified, is that it assumes the O-ring
is squeezed about ~15% by the channel it is designed to go into. So the spec is
the channel size not the unsquished o-ring size.
I have looked into the Olympus part and it is definitely not a standard
American size part. I measured a new one carefully optically (using my flatbed
scanner) and it does not seem to exactly fit a listed Metric series **that I
could find** either. As the above reference indicates that does not mean all
that much!
Here are measured values:
ID 0.168? (4.26mm) (~ nearest US list 3/16)
OD 0.268? ( 6.81mm ) (~ nearest list 1/4 -9/32?)
So C/S thickness: ~ 0.05? (1.27mm) (= nom 3/64?)
So in metric series this would nominally be: C/S 1.27mm by 4.26mm
Here are some good o-ring information sites :
http://www.frederickseal.com/NewFiles/tips.html
http://www.vedovell.com/metric1.html
If anybody can identify a source other than Olympus for the O-ring, I would be
interested to hear about it.
Although replacing the o-ring is not too difficult it is quite a chore
reassembling the whole thing,while not trapping/breaking the small fragile
wires which are often glued in place. In general just desolder the wires so the
parts are disconnected while repairing or you are guaranteed problems. Some
parts are easily damaged by soldering, like the 250 shot back connector/sw.
Desolder at other end of wire to avoid problems.
Regards,
Tim Hughes
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