[TheForge] Re: Flatbelt excitement

[Mike Spencer]

Ralph> ...a tensioner is used in a flat belt when the machine has no
Ralph> clutch.  When dealing with a hammer like a Beaudry...

Yeah.  My first hammer [1] had that.

Ralph> Or am I misunderstanding what you did (which may be the case).
Ralph> The A&O is a self contined correct?......so no clutch required.

Yes, self-contained.  Using an engine to drive it instead of an
electric motor, there has to be a clutch somewhere but the hammer
crankshaft is supposed to run all the time at a constant speed.
Control of the tup is via the control valve, connected to a lever for
a hammer driver and to a treadle for single-handed use.

Ralph> The other thing about short belts with one pulley(drive) being
Ralph> smaller, and the larger machine pulley being larger is it
Ralph> allows the belt to run on 2/3 of the surface of the pulley
Ralph> instead of 1/2 like a long drooping belt would.........so the
Ralph> tensioner will allow a slight increase in the surface the belt
Ralph> rubs on the drive pulley (especially if placed close enough to
Ralph> the drive pulley to affect the wrap angle.

The drive and driven pulleys are the same size as it's now set up.
There soesn't seem to be much slippage after half a can of spray-on
belt dressing. 

Ralph> Synthetic belts are stable - but they grab more than the
Ralph> leather ones.

I'm using ruberized fabric belts.  I have a leather one but it's not
long enough.

Ralph> On a long belt (around said tree) an idler may be needed to
Ralph> take the droop out of the belt in the span it crosses.

That may work if I can figure out a way to mount it.  Maybe, since
several people have responded with advice, I should get a pic of the
setup for all to see.  Maybe tomorrow.

Rick> A v belt runs on the sides of the v, while a flat belt is driven
Rick> by a wide surface of contact rather than a tight surface.  The
Rick> older machines that were made for flat belts were normally made
Rick> with out regular bearings, and with babbit.  This is not
Rick> intended for the force of a side load, such as a tight belt
Rick> would provide.  Rather the width of the belt provides sufficient
Rick> force by friction of a wide surface.  This should be thought of
Rick> when discussing a changeover from a flat belt to a v belt drive,
Rick> as they are very different animals.

That's a good point.  However, this whole thing is more or less from
scratch.  The original configuration had a 15 HP electric motor --
several hundred pounds -- bolted to a cast iron plate 30" square x 1"
thick which was in turn bolted to a flange on the hammer body.  The
plate was to be bolted down to its own foundation pier with
1-1/4" anchor bolts.

I've bolted a rather light plaform of 1x2 HSS to the hammer, striped
the armature core off the motor shaft and mounted it in pillow blocks
on the platform. [2]  The gear that was originally on the motor is now
back on the shaft and engages the 24" gear on the hammer crankshaft
with a tiny bit of gear lash.  So the conversion is from electric
motor->gear->gear drive to
some-power-source->whatever->shaft->gear->gear.  Whatever = V-belts
seemed to work well.  I haven't tried a direct coupling yet.  That is
probably the best final state for this.

The gear shaft is in ball bearing pillow blocks but yes, the modified
truck has a shaft in babbitt bearing.  Happens they were designed for
a diagonal load so a horizontal load is not as bad as it might be.

FWIW, a couple of pics of the flat belt setup in my shop are here:

    http://home.tallships.ca/mspencer/img/lineshaft.jpg
    http://home.tallships.ca/mspencer/img/belt.jpg

The pics show the belt for the 25# Jardine tied out of the way so the
saw belt can use the pulley.  Now the saw has it's own pulley on the
same shaft so I don't have to swap belts to swap machines.  The hammer
belt is a Moebius, just to make it a bit tighter.  The saw belt has a
twist to reverse the direction -- band saws have to saw down, not up. :-)


- Mike


[1] http://home.tallships.ca/mspencer/old-hammer.html

[2] Some pics are here:
          http://home.tallships.ca/mspencer/shop/news/
    if my description is intrigueing but inadequate.  The engine shown
    there worked fine with 2 V-belts in every respect except for
    having too little power to actually raise and hold the tup.

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