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Posted by Malcom \"Mal\" Reynolds on April 18, 2010, 5:07 pm
I couldn't tell you why, but I have a
feeling that if you used tapered
calander rollers you might see an
increase in efficiency
Posted by Curbie on April 18, 2010, 7:46 pm
This video (25 seconds):
... shows the spiral grooves in the rollers, which I believe acts
functionally like a tapered roller (wider gap, reduced pressure), but
most videos show the operators avoiding them opting to fold, twist, or
stack the feedstock in subsequent passes using the smooth part of the
Tapered rollers seem like a good idea, but it concerns me that the
operators that do this daily don't seem to use that option much.
These are the two videos I found that use the single pass three roller
design I'm thinking about on a much smaller scale.
It seems safety was not a heavy consideration.
Posted by Jim Wilkins on April 19, 2010, 2:04 pm
Spring-loaded rollers that don't touch, both rolls the same size and
turn at the same speed (?), rollers could be made from a scrapped
hydraulic cylinder tube on a 10" - 12" lathe. The complete absence of
rust suggests that they are stainless or chrome plated, but you could
use mild steel and oil them when done, you aren't processing food. I
didn't see evidence that dissolved metals poison Kluyveromyces yeast
I think she runs the cane through until she sees only a little more
juice come out, meaning it isn't optimized for one pass and instead
depends on a somewhat attentive operator who is doing a boring but
dangerous task. She may have been nervous in front of the camera and
changed her routine for appearance, gotta watch for that.
I don't understand why the bearing blocks set a minimum spacing that
caused her to run two pieces through together to squeeze out the last
of the juice. Maybe the rollers had been damaged and remachined? The
gap looked too small to avoid crushing a hand, but hard to tell.
Possibly the stalks don't start to feed as well if the rollers touch.
You could sandblast yours to increase grip, or pass coarsed sandpaper
or a file through a few times.
You could stand further back for greater safety if the stalks fell
onto a cart on the far side and you ran a pile through once, then
swapped the full and empty carts. Her way may be faster.
Standard involute spur gears connecting the rollers work fine when the
center to center distance varies a little, pick a coarser diametral
pitch if you have a choice, at least 12 teeth and 20 is better, 14-1/2
degree Pressure Angle should be OK. They are available with any number
of teeth (to match pitch circle to roller diameter) as lathe change
gears, while 20 PA power transmission gears give you fewer choices.
Frame could be made from 1.5" or 2" square tubing or 3" channel and
readily available bearings and threaded rod. My stock of cheap 3"
channel came from salvaged pallet racks. Parallel members will bend
inward from weld contraction when you weld cross pieces between them
at the ends. You can reduce that by not welding the inner corners.
I would add a clutch that engages a tensioning idler when pressed and
possibly a brake when released, with freewheeling in the center,
arranged such that if you are suddenly yanked toward the machine you
can release it without further losing your balance, ie a rocker foot
pedal rather than one you lift your foot off. Something like the
safety grip on a lawnmower or the deadman switch on a locomotive. See
what's used on a commercial brush chipper. On my sawmill it's a lever
that operates an over-center toggle adjusted to stop barely over
center so vibration or a quick flick will release it. The lever and
the engine throttle/cutoff are close together and near the handle I
push the cutting head with. Both are up to run, down to shut off, no
hesitation to remember.
Those are just hints, I don't know what is legally required, just want
you to consider the options early enough in the design process.
Posted by Curbie on April 19, 2010, 9:20 pm
The two roller machines are mostly for street beverage vendors and
always shown as a multiple pass operation that I'm not really
This seems to be a common practice for the operators, folding,
twisting, or stacking the feedstock to press more from later passes,
it seems to me that they're concerned with overloading and jamming the
machine, snuffing the engine. (a mess to undo)
These are screen-shots from the two three roller machine videos that
show a single pass operation that does interest me:
The red machine shows (what I think may be) roller adjustments the
other shows none, neither machine shows springs of any type, and all
rolls and roll gears seem to be the same size and turn at the same
The roll pressure seems to be determined by the roll gap so I'm
thinking I could set both gaps with a combination of shims in the
upper roll (moving it down) and a couple screw stops to adjust the
upper roll horizontally, increasing the gap (decreasing the pressure)
between the front and center rolls while simultaneously decreasing the
gap (increasing the pressure) between the rear and center rolls.
I think sandblasting or sanding the rolls is a good suggestion and
along the same lines it seems the may be a feed relationship between
the diameter of the feedstock and a proper diameter of the rolls I
need to think about.
After reading your thoughts on gearing and safety I'm wondering if a
hydraulic drive may be a safer option with quick stops and reverse
capabilities, I know it would increase costs, but the safety and
operational benefits may be worth it?
I was looking for some options for a DIY machine to juice a JA
feedstock and I think I got them, I don't think I can determine which
is best at this point without first growing and testing the feedstock,
but at least now I feel I can deal with juicing with one option or
You still need gears connecting the rollers to make them turn at the
same speed in opposite directions. Hydraulics are fine if you get
everything right the first time but considerably more expensive to
modify than belts and gears if you don't. Be sure you get pumps and
motors with straight keyed or Woodruff shafts, SAE splines or tapers
are a nightmare to adapt to:
That SAE spline broach wasn't hardened and dulled slightly making one
hole in an aluminum pulley. It bent on the second larger pulley, but
still worked OK, I needed more torque because the drive belt slipped
on the first small pulley. However I paid only $0 for the $00 pump
and the broach is part of my job interview sample bag and helped me
get into Segway.
The control valve for a logsplitter requires constant pressure on the
lever to run in one direction, the other direction latches but pops
out when the pressure rises. On a log splitter the non-latching
position is to split, the latched one to retract while you grab
another log. You could swap them so it latches to squeeze stalks and
pops out on a jam, the non-latching position would reverse the rollers
to clear the jam.