[TheForge] Flatbelt excitement

[Mike Spencer]

Of interest only if you've used flatbelt drive on something or are
thinking of it:

Live an learn.  Instead of thinking ahead, eh?

I've just learned that flat belt drive can be a problem with a machine
that doesn't maintain a load on the belt.  I hooked a horizontal belt
up to my A&O air hammer with about a 9' gap between pulleys, good
tension, pretty good alignment, good belt, lacing and pulleys and
plenty of power but no tensioner idle pulley.

The hammer has a crankshaft driving a quite heavy vertical piston.  On
the upstroke, the lower run of the belt is under considerable load and
works properly but on the downstroke, the hammer runs ahead, tending
to slack off the lower run of the belt and pull the upper one taught.
That starts an oscillating wave in the belt that gradually becomes
quite um... exciting and spectacular before throwing the belt off the
pulleys.

Jeez, it's obvious, only I never thought of it beforehand.  Didn't
appear to happen with two (much shorter and tighter) V-belts.  (The
engine with the V-belts doesn't have enough power and the
modified-truck flat-belt "power plant" doesn't fit into available
space up close to the hammer.)

I dunno if a tensioner idle pulley would fix it up or not.  A much
shorter belt would probably help a lot.  Time to do gardens so I'll
have a week or two to think about it before I get back to hands-on.

Any advice or accounts of experiences dealing with machines that
overrun the flatbelt drive would be welcome.

- Mike

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^