UNIQUE RPC-150 APPLICATION:
I’m using every application on the
-Gordon Scale, P.Eng.
Mississippi Blacksheep Gallery Inc.
The following story was submitted by Gordon Scale, Mississippi Blacksheep.
At first glance, Mississippi Blacksheep might be thought of as a relic of centuries past – in any case, a long way from a new millennium exploding with embedded digital technology.
We operate from a century old stone home on the main street of a small rural town, right on the banks of the Canadian Mississippi River. We sell natural fibers and yarns, spinning wheels and hand-weaving looms. My wife, Sue, is a talented hand-weaver and spinner, specializing in both historical textile recreations and one of a kind, original fabrics.
In weaving cloth, the number of “shafts” available on the loom largely determines both the number of possible patterns, and the complexity of the woven structure. Most hand looms are restricted to two to eight shafts. Sturdy foot-powered looms capable of weaving rugs are commercially available up to about 16 shafts providing the potential for thousands of pattern combinations – but have major short-comings. Physical treadles severely limit the practical number of treadling combinations available. Changing patterns normally involves tying, adjusting and re-tying dozens of cords – several hours on your hands and knees crawling around under the loom. The physical effort of lifting multiple shafts thousands of times is very tiresome – quickly dissipating the joys of designing something new.
Having woven daily, on a fairly heavy 16 shaft loom for over twenty years, Sue wanted to both challenge new textile design opportunities and give her broken down knees a well earned rest. She had a wish list for a new electronic multi-shaft loom that even Santa Claus couldn’t fill!
- 32 fully independent shafts, countermarch operation for best possible “shed”,
- effortless compressed air powered,
- compatible with the latest commercial fabric design software,
- dead easy to use for her “technically challenged” students,
- no adjustments (ie. the elimination of mechanical levers, pulleys, cables and gears),
- near silent operation,
- the ability to change to a new pattern in seconds (as opposed to hours or days), and
- attractive aesthetics, fully compatible with traditional, fine crafted, centuries old loom technology;
- being, front and centre in our shop, it had to be perfectly safe (yet robust) for prying three year old fingers, and perhaps the most severe constraint;
- during delivery, it had to fit within the constraints of our narrow stone doorways or windows!
No commercially available product could ever come close to that wish list!
So what does a DH (webese for “dear husband”) do? Why of course, to preserve peace in the household, one says, “Yes Dear”.
Having done a little hardware and software hacking in the early days of micros –
(yes, I was one of those poor slobs that tried to make an Altair 8800 do more than blink lights, and some kid by name of Gates, feeling sorry for us duped slobs, wrote a teeny 1/2k monitor program, calling it “Package Number 1”, ensuring that we got our millions of hours of frustration! ….It’s still in the attic, a constant reminder of the thousands of dollars I’ve flushed …. )
I figured that I would try my hand at building the loom – this time using time tested technology and old fashioned “BASIC” for ease of programming (this may not be elegant, but I used to plan roads for a career – not code programs)!
We sell Swedish made “Glimakra”, Dutch “Louet” and Canadian made “Leclerc” loom products. Not wishing to reinvent the wheel, we purchased a four shaft “Glimakra Standard” loom and lengthened it for the basic loom frame. As Sue prefers rigid shafts and steel heddles, we then purchased 32 shaft harnesses from “Leclerc Looms” and commenced a major redesign of the loom. While these manufacturers make high quality foot-powered, handloom products; because of the high forces of pneumatic actuation, quite understandably, significant strengthening and redesign of these products was required.
I scanned the periodicals and searched the net, and lo and behold, Remote Processing had exactly the product I needed – better still, it was less than half the price of my original Altair with it’s whopping 256 bytes of RAM!
The RPC-150 had it all!
I needed two serial ports, one for communicating with fabric design software running on a PC clone, and a second one, hidden from the typical weaver, for programming, setup and development. CAMBASIC’s interrupt routines for string input significantly simplified program coding of the communication protocol.
The 32 shafts were to be individually actuated by double-acting air-cylinders. The air-cylinders are actuated by 12 volt solenoid pneumatic valves. Thus 32 latched TTL outputs were assigned to buffered opto-isolators driving MPS960 MOS switches. CAMBASIC makes bit toggling a cinch!
A Remote Processing KP-1 keypad was mounted on the front of the loom for a user console. This required 4 TTL input lines and 4 TTL outputs. CAMBASIC’s built-in keypad input routine simplified console software development considerably.
Three latched TTL output bits were assigned to drive a seven segment LED display on the operator console. Four more were configured as inputs, sensing the four treadle switches. That sums to all 47 digital I/O bits available on the RPC-150!
However, on the RPC-150 there exists a 48th I/O bit (no longer used for a chip enable), so it was used to control a relay for a master 12 volt power control. Thus, by implementing a watchdog timer in software, if not attended, the loom powers itself down – additional safety for those prying three year old fingers!
While the design of the three dimensional geometry of the shedding mechanism was non-trivial, the basic design of the loom is sheer simplicity. The traditional shafts slide in end supports, and are suspended from double-acting air-cylinders. A box located below the cloth rollers houses the RPC-150, the solenoid driver card, 32 solenoid air valves and a surplus PC power supply. As much as possible, the air lines and various hardware components are hidden behind removable pine and maple cover plates. Like the loom frame, the entire assembly can be relatively easily disassembled should shipment be required.
The loom is truly a turn-key system. The program is stored in the 32k flash EPROM and self-loads into RAM on power up. The weaver can work in two modes, shuttle pick by shuttle pick in direct communication with the PC (the usual method for somewhat similar commercially available electronic looms) or, the pattern can be downloaded into circular buffers in the memory of the RPC-150. The spare memory is sufficient for a pattern repeat of nearly 2000 threads – that’s a treadling sequence about 50 to 100 times longer than most weavers dare remember on a traditional hand loom! Truly wonderful new original fabric designs are not only possible – but merely several mouse clicks to create!
The loom has been in almost constant use since March ’98. All kinds of yarns have been used, and all kinds of fabrics woven – and best of all – effortlessly, and with great delight! Over the last few months, several dozen very talented weavers, who own and are very familiar with numerous commercial looms (including more expensive electronic Dobby looms), have woven table linens or fashions for themselves. Stealing a quote from Tina Turner – all have agreed:
“it’s simply the best!”
As designer and builder, that’s a great complement, but as designer and builder, I know I owe most of the credit to the technical assistance I received along the way, and to the superb products I had available to me to work with – especially my Remote Processing’s RPC-150, a product I highly recommend!
From initial concept to completion, the loom took seven months to design and construct – working at it about half the time. This includes welding and wood-working in sub-zero F. temperatures in an unheated workshop, coping with Ice Storm ’98, and then the flooding of the Mississippi (yeah, that was our place on National television clips of the flooding). My workshop is extremely limited, production manufacturing of this loom is out of the question. However, if there are any other DHs around so foolish as to say “yes” before they have engaged their brain, please feel free to pass on my name and email address etc.
Sue and Gord Scale