Monday, 29 February 2016

Inside Nellie


I don't know how much terminology is common between knitting machines, and I don't know how much terminology is familiar to machine knitters.  However, I hope this post might be useful to you if you are sitting with a Toyota Elena Auto 7 (Toyota K747) knitting machine and you're thinking of taking it apart.  Sorry if the terminology is odd or unfamiliar, I only know what words are in the service manual.  I have never machine knitted in my life yet (I had to fix my machine before I could begin), so sorry if I am aiming the technical talk too high or low.

Getting to the mechanisms

Main body of machine lifted out of casing

The first thing we did was take the sponge bar out, ready to later strip and replace the sponge with two layers of 9mm draft excluder (thanks ebay) and a layer of fusible interfacing (better sponge/interfacing combo yet to be purchased).

Then we removed the screws in the blue casing (as indicated in service manual) and eased the main machine out of the casing.  You can see this stage in the above picture - the casing is sitting behind the bottle of Meths and has become a dumping ground for space screws and notes.  The refurbished sponge bar is sitting in front of the machine.

The next stage was to remove the rest of the blue/cream plastic casing from the top of the machine.  The service manual gives screw locations for this, some of which are hidden underneath the knobs if I remember correctly.

Needle selection mechanism

The needle selection mechanism is revealed.  The blue "S" levers can be actuated by hand or by punch-card, and the red "J" lever can be used to choose between these options or reset the S levers.  More of this later.  There are some white cogs visible around where the knobs were - the leftmost winds the punch-card in, and the right "zig-zag" knob sets the position of the 12-stitch pattern relative to the central needle.  Rotating this moves the entire top mechanism (pattern board?) along relative to the needle bed.

It turns out there is a little bell underneath the zig-zag knob that rings when you've moved the needle selector (by applying wrench under front left of machine).  Obviously this charming "feature" wasn't working for us until after the overhaul because the whole machine was seized.  It's not working any more either, because I shoved some sponge inside the bell so that I can stealth-knit when the children are asleep.

Underneath the machine

Flipping the machine over, you need to be careful not to damage the needles, so best have them hanging over the edge of the table, or removed (as we did).

On the bottom, you can see a variety of plates which I'm going to do my best to describe.  The biggest pair of plates are named "J installing boards" or somesuch (the manual refers to them by more than one name), while the next biggest pair are the "S installing boards".  I think the names may derive from the shape of the linkages attached to them, if that helps you to remember while reading the manual.

Anyways, all the plates are bolted to the underside of the needle bed joint plate at the front of the machine, and have linkages with cams that work into slots on the "working board" - a metal bar that runs the length of the needle bed and moves back/forth and side to side as the needle selector is actuated.  The working board has a big spring that attaches it to one side of the machine (bottom right corner of picture below).

The J installing boards have their back end bolted to one of the two long metal plates that support all the pattern selector levers and gubbins ("J feed plate" and "J pedestal plate").  The S installing boards have their back end bolted to the "S rest plate", which on the other side has a bunch of black notched plates, named "S pattern plates" or "S boards" or something (the names get a bit confusing).  There are a bunch of other smaller plates to set working distances and keep it all square.

How it works

Here is (approximately) how it works.  The needles are selected by your fingers on the blue S-levers, or by the punchcard which also flicks those blue levers.  The levers have little legs underneath which sit astride some rods (the "S rods" or something).  The clever stuff happens when you actuate the big "needle selection mechanism" lever with a wrench on the bottom left of the machine.  When selected, the lever engages with the rod below it and flicks it to the side, which flicks up the corresponding S board (with the notches on top).  The S boards are then moved toward the needles, and the ones that have been selected (moved up in their mount by the rod) push on the needles, moving them to the appropriate position.  Ta-dah!

The S/J lever mechanism has been removed here, and you can see the S-rods poking through the S boards.
There are 23 S-rods, to account for the full range of pattern positioning (only 12 of these are aligned with the 12 S-levers at any time, dependent on the zig-zag dial setting.  There are a bunch of tiny springs on half of them.

S pattern plates / S boards or whatever they're called
Here follows a little sequence of images as the needle selection lever is progressively moved.

1.  Not yet moved

2.  J feed plate moves forward (left hand side) and engages S levers with S rods, selecting the S boards

3.  S rest plate and all S boards move forward and select needles


We took apart every single thing except the black stack of S-boards and the armature pivots that had been riveted.  Everything was cleaned with auto degreaser and re-lubricated with lithium grease.  There are a LOT of contact surfaces, so thoroughness is key because little bits of friction can add up.  If you look carefully at the photos you can see my scribblings where I used permanent marker to label the pieces with their names and mark positions.  I also scribed important location marks into the metal with a knife as auto degreaser removes the pen and basically everything including all the moisture in my palms.  (Dammit.)

If you use blu-tak to secure each screw you remove near the hole it came out of, then you can even get the whole thing back together again without losing a screw.  Except the one that gets blu-taked to your sleeve accidentally, but don't worry, that one gets found safely on your arm when you go the computer to look for a replacement on eBay, so you never have to press "buy" ;-)

As you can imagine, most of the yarn-related fluff is under the needle bed.  You can get all the needle springs out to clean in here.  There are a reasonable number of screws, but it's not that tricky once you're in there.  Also, the needle bed joint plate has a bunch of fluff inside, and you have to carefully peel off the needle numbers from the other side to get to the bolt-heads so you can steady them while you undo the nuts on the underside.  You'll need double-sided tape when you reassemble this bit (the sinker comb is 100 individual 2-prong pieces), plus some spray-adhesive for putting the numbers back on again (for heavens sake, spray the adhesive on the number strip underside NOT onto the machine needle bed!!!)

The trickiest parts were:
1.  Guiding the S rods back through the S boards (start at one end, with the rods angled slightly, and align each one in turn as you bring the parts parallel again).  It's a two-man job, unless you build yourself a jig like the one they have in the manual.
2.  Getting the little springs back on underneath the S lever mechanism.  I used button-thread to pull them through and ease them on.

If you are reading this because you have your Toyota K747 in bits all over your table: good luck!  I wonder if this post will prove to be as dull as I anticipate, or unexpectedly popular?  After all, my most visited page on my last blog concerns repairing washing machine tachometers, and it's proved a hard post to beat in terms of viewing numbers :-S