Presentation on theme: "1 The coils are formed from 16 AWG (1.3 mm diameter) tinned copper wire. Each coil has 2 bridge-overs... Bumps away from the surface of the cylinder to."— Presentation transcript:
1 The coils are formed from 16 AWG (1.3 mm diameter) tinned copper wire. Each coil has 2 bridge-overs... Bumps away from the surface of the cylinder to cross the neighboring coil with a minimum of capacitance. Each coil has an associated board for tuning/matching components, a 32 MHz preamp (C13 at 3 T), Q-spoiling circuitry, a proton trap, and connectors for RF-out and for 12 V & gnd. A separate board folds around the circumference at the cylinder base and holds mating power connectors for distributing power to each board.
3 We’ll use 3 jigs, in consecutive steps, to form the necessary wire bends for each coil: Jig 1 Jig 3 Jig 2
5 After Jig 1 step:
6 After Jig 2 step:
7 After Jig 3 step:
8 Starting with Jig 1, cut about 24” of 16 AWG wire. This will be plenty more than you need. You’ll cut to length in the last step: The idea is to use Jig 1, along with locking vise grips and clamps, to make two planar bends (the bridgeovers) in the plane of the jig which is parallel to the floor. You don’t want to bend the wire up in the 3 rd dimension... it will work harden if you fiddle with it too much: There’s a feature in the shape of a pointer here. Put the middle of your wire about there.
9 Use locking vise grips to pull on the left end of the wire, while the far end of the jig has another vise grip clamping the wire: Make your first bend in the plane (no other jig fixtures should be on yet, so you’ll have room to bend the wire in the plane):
10 Use a former (some piece of scrap material) to act as a pusher, so you can really bend around that corner tightly: Tip: your partner can pull on the wire to keep the far left end of the wire in tension.
11 Now add the 1 st jig fixture (L- shaped with the toe of the L pointed towards the center of Jig 1). Tighten it with a screwdriver, making sure the bottom lip is flush against the body of the main jig. Then use a clamp to hold the 1 st jig fixture on tight (as you’re going to apply a force against it, next). Apply the clamp so that you have room to keep the wire in the flat plane throughout the next bend.
12 This next bend is to pull the wire all the way around the 1 st jig fixtue in the opposite direction from the previous bend. Keep the wire in tension and use your former to make the bend tight around the 1 st jig fixture.
13 Now put in the 2 nd jig fixure (it’s the longer of the two rectangles), tighen with a screwdriver such that the 2 nd jig fixture’s lip abuts flush against the body of the main jig. Add another clamp. Again, mount the clamp so that you have room to make the next bend also in the flat plane:
14 Also apply tension to the wire before you start your bend. This next bend will be back up and to the left. Like this:
15 Use your former while your partner holds the wire taut. You’ve now made one bridge-over.
16 Now start working on the 2 nd bridge-over. First, do the bend up around the main jig’s top extrusion, just like you did before on the left. Use your former and keep the wire in tension:
17 Screw in the 3 rd jig fixture (it’s an L- shaped fixture with the toe of the L pointed towards the center of the jig):
18...and clamp that 3 rd jig fixture tight:
19 Bend the wire down around that 3 rd jig fixture. Keep the wire in tension and use your former to make the bend tight.
20 Now screw in the 4 th jig fixture (it’s the shorter of the two rectangles):
21 Clamp the 4 th jig fixture tight.
22 Now your ready to bend around the 4 th jig fixture:
23 Bend around the 4 th jig fixture, with tension, and using your former.
24 Almost done. But there’s one important thing to do before removing all the clamps...
25 This little plastic piece is pointing to the spot on the wire, where you need to use a magic marker to make a mark on the wire.
26 Mark the wire. Remove the clamps. Now you’ve got 2 bridge-overs in the plane parallel to the floor.
27 Take the wire out and mark all the way around the wire at that spot.
28 This should be your result:
29 We’re going to form a real 3D curve here, by the end of this 3-jig process. This Jig 2 is for bending the wire in the perpendicular plane to the plane of the bent wire. Place the wire so that the mark is at the apex of this oblong Jig 2. Important: orient the wire with the bridge-over in the vertical plane.
30 Adjust the locking vise grips and clamp the wire onto this Jig 2. Note that because of the bridge-overs, you can’t pull on the wire to put it in tension (you’ll pull out your bridge- overs). Just use your former to make the bends you need.
31 Make your bends using the former, making sure not to pull the bridge-over out: Put in the 2 nd vise grip clamp Now you can’t pull out that bridge-over, so put a vise grip on the end of the wire and pull it taut in this direction. Use your fomer as you bend the wire around the neck portion of the oblong Jig 2.
32 Use a magic marker to put a marker where you’ll eventually make the neck cut for this portion of the wire. The spot is the outer edge of this first, closest indentation (I forgot to do it here, and so I kludge it a few slides from now).
33 Make a cut about here (doesn’t matter), and remove the last two clamps. The bottom sproings back, but we’ll fix that later.
34 Repeat for the righthand side of the coil, making sure not to pull this bridge-over out either:
35 Use the former all the way around, bending the wire, taking care not to pull out the bridge-over.
36 Put in the 3 nd vise grip clamp: Now you can add a vise grip clamp to the far end of this wire and pull it taut in this direction.
37 Cut the wire at roughly this location and remove it from the Jig 2:
38 Now for some precision touch... In order to get the legs parallel to each other, we’re going to make a first squeeze about ¼ of the way down from the apex. You don’t want to overly fiddle with this wire, or it will work harden and get all wrinkly. Just one squeeze at this point...
39...will result in this:
40 Now one precision squeeze ¼ of the way up from the neck for this end of the wire:
41...will result in this:
42 Now the 3 rd precision squeeze for the other end of the wire:
43...will result in this: Except for the 2 bridge-overs, we have a planar oblong coill.
44 Since I forgot to mark the neck cuts earlier, I put the coil back on Jig 2. You want to mark each wire at the outer edge of these indentations.
45 The end of the wire coming down the left side of Jig 2 from the apex needs to get cut here: The end of the wire coming down the right side of Jig 2 from the apex needs to get cut here:
46 This should be your result after Jig 2. Next, we’d like a bend about the long axis of this oblong coil...
47 That is, right now, our coil is (except for the 2 bridge-overs), essentially flat. We want it to wrap around a cylinder:
48 Simply doing something like this, doesn’t work very well. We need Jig 3.
49 Jig 3 is a half-cylinder that has a diameter of 75% of the diameter of the rat cylinder. Put Jig 3 in a drill-press vise like this one. In this photo, we haven’t pushed down on the coil yet... it’s still basically flat here, in a plane parallel to the floor:
50 By forming this bend on a cylinder of smaller diameter, the oblong coil will sproing back and still be close to what we desire. Use your fingers to press the coil into the cylindrical shape:
51 Use your former to push down on both sides of the cyinder (without squishing your bridge-overs) to get the wrap-around-the-cylinder shape:
52 Then cut at the first mark for the neck.
53 And then make the second cut at the other neck mark:
54 Keep pressing. This is the shape you want:
55 This should be your result after Jig 3. The sides are lower than the apex and neck because they’ll be wrapping around the cylinder’s girth now.
56 To hold the coils in uniform positions around the rat cylinder, we need some way to hang onto each coil. In this case, we 3D-printed a cylinder with integral clips and holes for stitching the coils into their proper locations. Each coil has an associated board for tuning/matching components, a 32 MHz preamp (C13 at 3 T), Q-spoiling circuitry, a proton trap, and connectors for RF-out and for 12 V & gnd. A separate board folds around the circumference at the cylinder base for mounting the mating power connectors for distributing power to each board.
57 Strategically-placed holes for Stretch Magic string (an elastomer jewelry cord) allows us to sew each coil into place. We use 0.7 mm diameter cord, with two consecutive square knots, followed by a drop of E6000 glue.
58 The string is this Stretch Magic, an elastomer jewelry cord, from Michael’s Crafts, manufactured by There’s a YouTube video here on how to tie off the ends (they suggest 2 to 3 consecutive square knots, followed by a drop of glue): For glue, don’t use superglue (makes plastics brittle). Use a general purpose adhesive such as E6000 (made by Eclectic Products), which makes a flexible bond (it’s designed to work on items subject to vibration, across a wide range of materials). E6000 is available in hardware stores, at craft stores such as Michael’s, and also at Tap Plastics.
59 Once the preamp boards are stuffed with components, two /16” long screws would be used to attach them to the cylinder. Then the coil ends would be soldered to these two pads: The board at the bottom was fabricated on the same panel as the preamp boards, which is thin enough (6 mils thick Pyralux AP adhesive-less kapton with 2 oz copper on each side) so that it can wrap around the cylinder:
60 Neighboring coils interleave under the bridge-overs: