The reason given for not replacing the hardware is that the disk driver is no longer made, and a second-hand driver goes for upwards of $250.
I was fairly certain that you gave a reason to that effect, but looking back on the posts so that I could inform truenorth of that reason resulted in nothing, because you never explicitly stated it. The first mention of price came from TrueNorth's post, and then a slightly cheaper one from Computer_Commando. At no point do you mention that the price is prohibitive, in fact you make no comment about the idea of replacing the hardware, which was probably the cause of Truenorth's confusion in that regard. That, and your posting about a hardware problem in the software section (because you are looking for a software solution, which is a good idea, but no such solution appears to exist, since reading the disks requires more then mere software compatibility)
This may seem a trivial amount to you, it does not to me.
It's not. I never stated it was. I was stating facts. Yes. It is expensive. But it's likely the only way to get the files off it.
Your use of the term "easy out" is insulting.
It shouldn't be. An easy out is what everybody wants for any problem, really; It's just unfortunate that there doesn't seem to be one here (a way to read Tandy-formatted disks in a standard floppy drive). If it is possible, it may be possible to emulate a system that normally uses said disk drive, and, if if is compatible with a standard 1.44MB drive it should allow you to read/write them. Of course I imagine the issue in this case is that you will be restricted to the environment of the likely less-capable machine, but from within said VM there will probably be a way to get files and data onto the Host operating system.
Apparently you have no concept of the value of money.
That is an unneeded assertion. Stating how expensive something is and that it looks like the only way your task will be completed hardly expresses anything about either how much money I make nor does it say anything about how spendthrift I am with that money.
Your failure to find information through Google speaks more to your ineptitude than it does to a lack of information Tandy TRS-80 was never mentioned, nor does it have anything to do with the subject in question.
every single query I entered had TRS-80 related material on the front page of results; even searching for "Tandy-100 disk drive" has the first three links going to sites related to the TRS-80; since even the most obscure items of this nature have some sort of following and hobbyist sites dedicated to it, I thus assumed that the Tandy-100 disk drive was designed to be used with the Tandy-100, which was in fact a TRS-80 Model 100 portable computer; since it is designed originally to work with that machine it seems reasonable that other people looking to get data from the disks would in fact refer to them as disks designed for that machine, rather then the drive within which it was used; additionally, I figured that the data most people would be trying to recover was probably made on such machines, and not for things like sewing/knitting machines, which are more a niche use of the product. And, since such utilities would work for reading the data from the disks used in said niche items, it would have worked in your case. My searches in said case didn't really turn up anything but the utilities on the TRS-80 page, but the TRS-80 and the TRS-80 model 100 had different drives, even though they were really the same machine in different cases (for the most part).
The disks which fit the Tandy TDD 100 are standard 3.5 inch diskettes. They are formatted differently from disks which are used on PCs, but are physically the same (see previous posts on the specs).
Yes, you said that. Some images I found made me think otherwise, but chances are they were something else. Also, some of the more recent searches turned up what appeared to be pretty much "normal" floppy disks (in that they would, as you noted, fit in a standard 3.5" drive).
There are several programs available which will transfer the patterns from the knitting machine to an IBM PC (DesignaKnit 7 is one of them).
If this can be done there is no technical reason why there could not be a program which would read the disks directly when they are inserted in an appropriate 3.5 inch PC disk drive.
Transferring patterns to and from the machine directly via a serial port is completely different then trying to read a disk format that wasn't designed for the drive you want to read it in. So far it appears nobody has devised a way to read Tandy-100 disks using native PC hardware (that is, the standard 3.5" floppy). Clearly it's not a simple task, since there are many devotees to the various systems that use the drive that have looked into it exhaustively, and such a tool would be very useful.
Therefore, it would seem that unless you plan to develop said software, or know somebody who is- or, if you follow CC's suggestion above and are lucky enough to have the drive only fail mechanically, you may have to either find a way to get a hold of another drive, or use a recovery service, which can get the data off the disks onto a PC-compatible medium for you, for a fee (which may very well exceed the cost of another drive anyway).