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Does anyone know if it is possible to recreate a 5 1/4 Twiggy Floppy Disk and/or Floppy Drive for use in an Apple Lisa 1 or a prototype Macintosh?  [?]  I have read somewhere that you could modify a high Density IBM disk physically to fit the specs, but I want to hear your opinions on this topic. :lisa: 

 

Edit: Why doesn’t this forum have a prototype Twiggy Macintosh emoji!!??

Edited by 10001001sos
Emojis and Comments about Emojis (no real purpose)
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A high-density 5 1/4" floppy can be modified to work in a Twiggy drive, that is true, because the actual magnetic media donut inside the envelope is essentially the same as that used by the Twiggy. (IE, it coating is of similar magnetic coercivity, higher than that used by the media in standard-of-the-time double density disks.) Because the envelope dimensions are also the same the conversion process in principle involves not a lot more than cutting a second set of access windows mirror-imaged to the stock one (after removing the donut through an open seam, obviously). Compared to a normal floppy disk the holes in a twiggy disk are rotated 90 degrees compared to a normal floppy; IE normal:

 

image.png.52730b7a679debc4d595b47d26ecb76d.png

 

 

Twiggy:

vdfl.gif

 

Notice that the Twiggy disk has an index hole in it which I don't think they actually used. It kind of implies to me that the disk manufacturers actually turned out the twiggy disks using the same plastic blanks used for normal disks, they just punched some extra holes in them after they'd already gone through the die that cut the standard holes.

As to recreating the actual drive, good luck with that. As the holes demonstrate the Twiggy used a completely nonstandard arrangement for writing to both sides of the disk, IE, instead of having the two heads oppose each other like a normal double-sided drive they had each head opposed by a fiber "shoe" like you'll find in a single-sided drive and had the back side read by a complete duplicate mechanism. The two head-read mechanisms rode a single positioning screw, so as the head on one side moved inward from the edge to the hub the opposite head moved from hub to edge. Because the Twiggy *also* used a variable speed motor to pack more sectors into the outer rim than closer to the hub this means the "proper" way to read/format a twiggy is to advance all the way through one side of the disk, edge to hub, with the motor speeding up along the way so to maintain the near constant linear velocity required, and then slow down the motor and go back the other way with the opposite side's head. This is exactly the opposite of what you want to do with the 3 1/2" variable speed drive in the Mac/later Lisa, where it's more efficient to read-write both sides on a given cylinder before stepping the head. Therefore there's no way to take a normal 5 1/4" mechanism with opposed heads and make it "emulate" the Lisa drive, you'd *have* to change the software driver.

 

If you're talking going all out and making new Lisa mechanisms, well, sure, you can do that. Start by disassembling two standard floppy drives for parts, then get yourself a lathe and CNC router to build a new frame, positioning mechanism, etc. Might be an interesting hobby. Just keep in mind that the Twiggy failed because it was actually a terribly flawed device both in principle and in execution: Apple wasted millions of dollars trying to make it work and ended up writing it all off in the end. I kind of doubt a DIY one will work a lot better.

 

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Very cool, thanks for the reply.8-)  I just wish that someone out there makes replicas of these old machines (especially the rare ones).  If an Apple-1 replica exists, then I think that a replica Lisa 1/2/XL should exist (even though it is more complex and harder to recreate).  Having these machines and prototypes (Macintosh Twiggy) not only available to serious collectors, but also average ones would make me so happy to see. :)

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  • 11 months later...

@10001001sos The hand-cut edges are fine and it does hold up as a working replica.  I am restoring a Lisa 1 and you can see it working here with one of these hand-made disks even though the particular disk I am using for testing has a bad track somewhere in the middle of the disk (because of the amount of times I have formatted and tried different things on it).  My other Twiggy drive needs an IC (on order) so the Lisa 1 should be fully working soon.   http://vintagecomputer.ca/goodtwiggysounds/

 

Edited by snuci
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It was recommended by James MacPhail to use DS/HD 3M diskettes and the particular brand/product noted below.  In addition to this "bad" floppy, I also have "Lisa Office System 1" and "Lisa Office System 2" diskettes recreated by using BLU on my good Twiggy drive.  I used those diskettes to install Lisa Office System on my X/Profile. 

 

James wrote via this LisaList post, "The one that had the highest success rate for me is 3M brand with UPC 51111 12883. It is a grey box with gold stripes labelled "DS,HD" "Formatted IBM"; 10 in a box. (There are other 3M DS,HD floppies in a very similar box with a different UPC that didn't work as well.)"

 

I found and am using these ones.  My Lisa OS 1 and 2 diskettes took several retries, doing a little more each time until it could format the diskette fully in one pass.  After that, you could format the disk in one pass with no issues (usually).  I am not sure if it is the pre-formatted 96 TPI that causes this because Twiggy uses 62.5 TPI) but I have not tried any other diskettes.  My very first diskette attempt was bad but the three afterwards were fine.  I  am not sure if the first disk was bad because I did a terrible job the first time, because there was a slight kink in the cookie because of my "butter fingers" or because I started with two non-functioning Twiggy drives that damaged the diskette.

 

Long story short, DS/HD work well for me.

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yeah, I vaguely remember that HD disks will not work fine because of the coercivity or whatever it's called in low density drives back from the commodore days. I used to order floppies from a bulk maker and for a while the DS/HD were cheaper than DS/DD, but they didn't work well at all in C1541s for example.

 

Perhaps other brands of DS/HD will also work if the disk is degaussed first.

 

This is kinda like punching the R/W hole on the other side of the disk so it can be used as a flippy, but taken to the next level of complexity. :)

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The reputation of Twiggy drives wasn't good to begin with.  I figured I'd just go with whatever someone had already tried and thought was okay.  He noted that even other 3m DS/HD diskettes with different product numbers didn't work well.  It's a picky drive given it's non-standard requirements. :)

 

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2 hours ago, sunder said:

yeah, I vaguely remember that HD disks will not work fine because of the coercivity or whatever it's called in low density drives back from the commodore days. I used to order floppies from a bulk maker and for a while the DS/HD were cheaper than DS/DD, but they didn't work well at all in C1541s for example.

HD disks are utterly hopeless in drives like the C1541 (and Disk II/TRS-80 Whatever/IBM 5150/etc), the magnetic coating on them is far too stubborn for the pipsqueaky powers of a double-density head. On the other hand, my recollection is that according to "those who know" the magnetic coercivity of the Twiggy was either identical to 1.2MB floppies or at least closer to it than double-density media, so of what's available it's the better choice.

 

Honestly I kind of wonder about the recommendation because, frankly, the capacity of the Twiggy isn't that great. They sold "Quad Density" drives that formatted conventional DD disks with 80 tracks of 96 TPI track spacing instead of 40@48 TPI and the resulting capacity was similar to that of the Twiggy and it was achieved without playing games like varying the disk speed. (Commodore sold a disk drive called the 8250 for the PET series of machines that actually got *more* on a disk than Twiggy using conventional DD media formatted in a GCR format that similarly packed more sectors on the outer tracks, but did it by varying the data rate.) It might be an interesting experiment to mod some DD media and see if the HD media actually does work better.

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I've only ever used DS/HD disks in my Twiggies. My first hacked up disk (which once held a portion of Microsoft BASIC Professional Development System 7.1) has been holding good bits since 1998. Other brands have done okay; I think usually 3M has been the best, but I've never been too picky---I've been slowly working through floppies I've found at junk stores and assuming around a 50% success rate. Other than the slight 3M preference, I haven't made enough disks to notice consistent patterns among brands. I think most of the success is down to how much I bend the disk jacket while I'm cutting it up.

 

I tend to trust James MacPhail a lot, but the good news is that we don't have to take his word for it :lisa:. The Twiggy specifications document on Bitsavers, PDF page 78 (at top), specifies a coercivity of 600 oersteds. This is identical to DS/HD media per Wikipedia or this old Byte article. DS/DD media is 300 oersteds.

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1 minute ago, stepleton said:

I tend to trust James MacPhail a lot, but the good news is that we don't have to take his word for it :lisa:. The Twiggy specifications document on Bitsavers, PDF page 78 (at top), specifies a coercivity of 600 oersteds. This is identical to DS/HD media per Wikipedia or this old Byte article. DS/DD media is 300 oersteds.

So, yeah, there you go, HD media is the correct choice. The Twiggy just sort of sucks at using it. ;)

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If only there was an affordable Apple Lisa 2 replica, the sapient boards are way too expensive and would probably cost as much as a complete original system on eBay.  If not an actual one, I would probably be satisfied with emulation, if a better Lisa emulator existed (LisaEm is not 100% compatible, thus it is not a true "emulator").

 

Edit: Imagine creating a wooden case for the Lisa instead of a plastic one :O

Edited by 10001001sos
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  • 1 year later...
On 5/19/2020 at 4:04 PM, snuci said:

Old topic but I did make a 3d printed template to make Fileware/Twiggy disks.  Works great.

IMG_0757.jpg

 

Is there a place we could download that cutting template? 
 

Thanks!

 

-J

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