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MMD > Archives > May 1997 > 1997.05.01 > 11Prev  Next


Wooden Crank Rods
By Craig Brougher

The conversation involving wooden crank rods and the proper speed
reminded me of a problem with an apparently perfect set of new rods which
still made a noise, even after tightening.  I learned that whenever I see
a set of old rods from now on, that they will just automatically get
remade, from what I have learned.

The hole in the rod probably gets stretched and becomes very slightly
oval-shaped (not to mention swaged), since the wooden hole will actually
wear the crank more than the crank wears it because of its ability to
retrain abrasives like dust and sand.  So if the old rods are allowed to
remain, they will eventually become to large for the crank, anyway.
Tightening them just creates a more oval hole.  (Although its the best fix
temporarily).

The way I do it is to first cut out a new set of rod blanks from
preferably maple or (possibly) beech and set them in the oven at 150 F
to dry overnight, since absorbed moisture in hardwood is easy to remove,
but entrained moisture is very difficult to remove.  You can tell by
weighing the blanks before and after the drying to see how much moisture
is left in the wood if you're curious.

The common method of drying hardwood lumber doesn't remove very much
entrained moisture at all, so depending on the time of year the wood is
cut, will determine largely the trapped moisture in the wood.  Until 100%
of the absorbed moisture has been removed, you will not be able to remove
the inter-pore water for a complete cure.  And you don't want to remove it
all, anyway, so  the wood doesn't start taking it up again.  Too much
moisture will cause your holes to change shape later on and the rods will
thump.

Put a good solid finish on the rods first, and then drill them exactly to
size with the crank and saw their kerfs, add the screw holes, etc.
Lubrication is important, and I have discovered a grease that seems to be
about perfect.  It is called JAX Magna-Plate 5.  This stuff is absolutely
filthy and adhesive like nothing else I've ever seen.  It is almost
impossible to remove from your hands, etc., so wear gloves.  But does it
ever do a number on wooden cranks! I have seen it stop creaking and
thumping, even in old out-of-round tired rods, when nothing else would
work.  It takes several applications, but it soaks in and does a fine,
permanent job.  It comes in a spray can but I like to put it in a pimento
jar so that I can also use it like canned grease.  Works also on Ampico
pumps and Duo-Art Grasshopper pumps with the wooden connecting push rods.

Craig Brougher


(Message sent Thu 1 May 1997, 13:29:47 GMT, from time zone GMT.)

Key Words in Subject:  Crank, Rods, Wooden

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