Holy Smoking Toroid Winder
Well, since we sorta hi-jacked Wrenchone's "Killer" screen drive thread, I'll start this new one for discussing DIY toroid winders for making OTs.
The Potthoff patent being the starting point, but any new ideas are welcome too.
Hopefully the moderators can move our previous toroid related posts over to this thread? Thankyou.
I'll mention some other issues related to the toroid winder for cogitating on. Some of these are probably dealt with in the Potthoff patent write-up, I need to go back and read it again. Been a while since I looked at it.
1) Turns counting on the toroid. The winding of turns on the toroid is not quite synchronous with the hand crank rotation since the wire spill off point moves around the edge of the C during operation. Some kind of optical interrupter is likely called for.
2) Rotation of the toroid core. The Potthoff design shows a magnetic chuck holding the toroid core, which is in turn mounted on a rotary table with a screw drive. This can only move the core thru some limited rotation angle before the core has to be re-positioned in the chuck. Not very convenient if you want to automate this whole thing.
Other winders use multiple concave rubber rollers, spring loaded against the outside of the core/winding assembly. These are driven to rotate the core then. This solves the limited rotation angle problem, but introduces some inaccuracy in the rotation angle control due to winding thickness on the core. Perhaps some combination of the two schemes, with an electromagnetically controlled chuck for turning control and spring loaded passive rollers for temporary holding during chuck repositionings. Still, there may be a centering problem during repositioning. Accuracy of core rotation is desirable for accurate progressive winding with its fine core dithering.
3) The hand crank operation shown in the patent does have a certain iconic appearance for the result of trillions of our tax dollars in development cost (apple peeler?). But for automating this, I would use a smaller cogwheel sprocket in the center of the C assembly for the belt drive and a hefty stepper motor to drive it.
4) Automation control. It would seem almost de-rigour to propose a programmed PC control of a bunch of stepper motors for operating this. But for DIY purposes, I think this level of automation and development is un-necessary. I think a foot pedal or "throttle-lever" operated pulse rate generator pot, routed thru a bunch of TTL counter chips with binary present control switch banks (setting counter divide ratios) would be sufficient to control the steppers. Then one can derive tables for typical counter settings for progressive wind rates, and dither angle etc. which can be interpolated for new designs. But if some PC expert out there would like to write up a Basic software control module with fancy visual screen interface, that's fine too.
5) During the pre-wind of wire onto the shuttle or "shuttleless C", it might be helpful it the wire guide between master spool and the shuttle or C could dither back and forth some to evenly distribute the wire build up. Either some flex/spring in the support for manual control or some stepper controlled contrivance for automated operation.
You might like this:
Toroid coil winding
Here's a whopper - a 3-4 foot toroid wind on a Jovil winder. http://video.google.com/videoplay?do...62384802328397
But these videos are not shuttleless as per Don's scheme!
Another thread on a DIY approach but again with shuttle: http://www.physicsforums.com/showthr...=130135&page=3
Perhaps there is some nuggets in these?
Here' another DIY effort but again not shutterless: http://waterfuelcell.org/phpBB2/viewtopic.php?t=1034
Unfortunately I can't see any of the videos on my computer. Reading thru the threads was interesting. But again, no pictures here.
The physics thread seems to discover the wire going slack each turn just before it quits with a vague approach of re-winding the wire back on the shuttle. The upside down shuttle slot approach is interesting though, and used by several commercial designs. The other discussion using the bicycle rim comes up with some guide plates to constrain the slack wire. Sort of precursor thinking to a slack accumulator.
Looks like using rubber drive wheels for rotating the toroid disturbs the windings, and wouldn't be very accurate once windings are on the core. I like the magnetic chuck approach used in the Potthoff design. I would improve it to use guide wheels during repositioning of the toroid on it. (the wheels would statically hold the toroid while the de-activated magnetic chuck rotates incrementally to a new angle then re-energizes)
If anyone noticed any technique used in the videos for handling the slack wire each turn, please mention it.
I have come to the conclusion that it is actually a plus to have slack wire available off the "shuttle" prewinding when handled correctly. In the Potthoff design, most of the actual winding onto the toroid comes from wire accumulated in the loop accumulator slot. This makes for smooth control of wire tension when winding around toroids with a square cross section. I would use a velvet covered, metal backed sheet pressed against the side of the Teflon C to control the tension in the slack loop accumulator.
Then I would construct the slotted C from three round Teflon sheets. This way, the accumulator edge sheet can be mounted slightly off center from the cog belt track/slot. This would allow the height of the rounded edge rim, that the wire spills over, to be varied versus rotation angle around the C. Where wire is already accumulated in the slack loop, the barrier could be higher to resist feeding from the prewound "shuttle".
From where the slack loop has pulled down tight on the core (meaning the position of the spillover point then), out until the spillover point reaches the furthest point from the core, the edge rim could be lower to allow easy spillover from the pre-wind to form the next slack loop.
Could it be that only the Potthoff design has the accurate control of wire position needed for progressive winds? Seems that the shuttle type designs loose tension on the wire every rotation and suffer from a slack uncontrolled wire loop. This might explain why most commercial toroids are wound "randomly".
You may have addressed this already & I missed it but how do you envisage the spill-off point moving across the gap in the C?
With the shuttle versions, the spill-off point is continuously controlled by a guide on the outside of the rim but this is not feasible in the Pothoff design as the rim no longer passes through the toroid but bypasses the toroid. This would mean the spill-off guide would have to drop the wire as it enters the C gap & pick it back up after coming out of the C gap.
Does this make sense?
Here's some other shuttleless toroid winder patent application from 1957 re US3050266 & from 1955 US2978193 & 1962 US3191878. I haven't had a chance to examine them but there may be something of interest in them.
"how do you envisage the spill-off point moving across the gap in the C?"
Yes, I mentioned this issue earlier (in the earlier thread section). The spill-off has to be captured again after crossing the C's gap. I would imagine that the leading edge of the Teflon C needs some judicious filing to get a long tapered knife like edge that expands back out and upward to the rounded spillover edge. It needs to radially expand upward from the belt's outer radius (bottom of the wire pile) up to the normal edge radius in order to capture the wire as it moves by.
It needs to first capture the wire, then bring it up to the normal rounded C edge level. There should be some V shape to the wire gap (relative to the belt) as the spill-off comes up thru the gap since the slack wire loop slot is feeding in the wire from maybe a 1/4 inch outward from the belt. So it needs to get the leading edge of the C inserted into that gap as it passes by. I need to read the patent details to see if that is mentioned. It could be one of those critical details intentionally left out though. One might be able to clip some kind of guide piece in place after inserting the toroid in the C's gap too.
Here is a picture of a Jovil head. Its using a shuttle still. But notice the toothbrush like appendage on the side (spring loaded) for holding back slack wire. Also, it is curiously using a cog belt to drive the shuttle. From their write up, this is necessary for heavy wire winding. Apparently the usual rubber drive wheels can't handle the torque for heavy stuff.
this one has got a much bigger slack wire dragger more similar to the Potthoff friction slot:
This is apparently a Jovil head for putting mylar insulating tape on the toroid core. Makes no sense to me how it could work. Any ideas? Appears to have a shuttle with rollers imbedded in it. Then a leather belt wrapped around it that turns the rollers as the shuttle rotates by. The belt appears to be tied down at the ends.
Maybe something like this: The mylar is wound up on the shuttle in a single stack and fed to the toroid from the bottom (inside) side as the shuttle rotates around the toroid. The leather strap is just a friction device to keep the mylar tight. As the mylar stacked winding is used up from the inside it rotates with respect to the shuttle on the rollers embedded in the shuttle.
This is clearly a new technique. I can't help but wonder if it could be adapted to winding wire as well.
On further analysis, this only works for very flexible stuff like thin mylar film, since it makes a 180 degree turn around the roller feeding the tape from the bottom. This would be too hard on wire without making the shuttle rather thick.
"some other shuttleless toroid winder patent application from 1957....."
The two early patents mentioned use two external shuttles with the wire bundle rounted around both of them like a belt on two pulleys (with the toroid core over one of the straight sections). Wire spills over the edges there too. The 1st one using double spherical surfaces to route the spilled wire loop, like I had earlier suggested. The second one reverts to just flat friction loop accumulators. Both of these double shuttle designs would severely wear the wire/insulation with all that dynaminc bending of the wire bundle.
The third one is in the Rube-Goldberg category in my opinion. Might as well program a robot to hand wind it.
Back to the spill-off in the C gap issue (Potthoff design). I read thru the Potthoff patent and there's no mention of this issue. But on thinking about this, I think it is easy to solve. The leading edge of the Teflon gap needs to be knife edge like and immediately adjacent to the belt, and a little lower than the belt's top surface (ie, just below the bottom of the wire bundle).
That way the wire can spill over the belt edge onto the lower Teflon edge (likely at the position of the leading C edge roller bearing below the belt, which will be curving it) just like normal spill-over throughout the remaining Teflon C track. Once the wire has dropped onto the Teflon knife edge it is captured, and the Teflon can now rise and widen as the rotation angle proceeds.
Eventually (smoothly) it rises back up and widens to the normal Teflon rounded spill edge. So judicious filing of the Teflon outer C leading edge is called for. This could be a mechanical wear point however (for the Teflon), unless the wire naturally wears the same contour, which it might. (a self sharpening knife?)
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