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[ried]

Managed to dislodge the rear head pad from the alien (spring clip thing). Has anyone made this repair before? It looks like the alien is glued down to the lead screw assembly, so I probably shouldn't try to remove that.

It looks like I should be able to very carefully use tweezers to lay down a new head pad with adhesive pre-applied to the bottom side. But the margin of error would be small.

Advice would be welcome and appreciated

[sigma7]

Advice would be welcome

On my drives, the spring thing Alien is not glued to the carriage (but the lead screw is, so you may see excess glue in that area).

So the Alien can be 'unclipped' from the carriage, by gently levering (by 1 mm or so) the center of the bottom of the spring, where it wraps around the horizontal bar of the carriage.

This is helpful to gain good access the the rear head for thorough cleaning, and I suspect would make attaching new felt easier.

I think tweaking the bottom is less likely to result in lasting distortion than unclipping the two sides on top, but I've done that too without any obvious harm.

I could send a pic tomorrow if the description isn't clear.

[ried]

Perfectly clear! Thank you for the detailed description, sigma7. For the felt material, I'd like to use new material rather than reattach the original pad. The original pads measure approximately 1/16" thick and 3/16" round, and feature an adhesive backing.

I understand that F-1 (F1) industrial felt is generally used for floppy disk drive head pressure pad applications, and it looks like this material could be a match: https://www.fixsupply.com/bulk-fs-f1-143-grade-f1-felt-strip-with-acrylic-adhesive-1-16-thick-x-1-2-wide-x-10-ft-long

I will use a 3/16" leather punch to create new head pads. Wish me luck 

[Kelly king]

     I just bought one on eBay .It shows white but it is black only 10.00 bucks.
     Works perfect.     

[ried]

Thanks Kelly. That includes a plastic stem with a pretty thick mounting structure. Have you used that in a Twiggy drive?

[Kelly king]

   Yes…
   It includes pad and stem with lips on end. I used this only on a 400k drive.
   Fits and works perfectly . Sorry didn’t know you were posting about a Twiggy
   drive.

[ried]

After removing the digital (lower) board, the alien becomes easily accessible from underneath. Mine did have some adhesive underneath it, which may indicate a previous repair? In any case, wasn't too difficult to remove. Should be fairly straightforward when it comes time to clean the remnant from the old head pad and install the replacement material.

I'm hoping that the adhesive already on the back of that 1/16" felt proves suitable. We shall see.

[ried]

Photos for posterity. You don't see this view every day...

[sigma7]

You don't see this view every day...

Many days I do

It may be the lighting, but the front head looks pretty dirty (presumably only due to your recent archiving efforts... thanks for those!) ... I find the rear one is often worse.

"Before and after cleaning" pictures may be helpful to someone someday.

Very nice condition otherwise!

[ried]

Many days I do

Of all people, yeah 

This is one of two drives I've been using to test and image old disks, and it's definitely encountered some crusty examples. If all goes well with the felt pad replacement, I'll probably change them all out and give each drive a thorough cleaning. I still have several old Twiggies to go through (Smalltalk 80, Monitor II, etc) but examples of most have already been archived.

[stepleton]

I'm not certain whether it was possible to save a workspace in Lisa Smalltalk, but if it was, the workspace on your Smalltalk twiggy could differ from the one on Bitsavers.

[ried]

Felt arrived today. I am pleased to report that I did not break anything (as far as I can tell). It's F1 industrial felt with adhesive backing. Using the leather punch it became clear that 4.5mm diameter is the correct size. James' tip about un-clipping the alien from the underside makes it very easy to do.

A few pictures of the dirty old head pressure pads and the newly-made replacements below. The original head pads are not quite as tall, a bit more compressed in their appearance. But I'm certain that the replacement pads will settle down to an almost indistinguishable height after they've had some pressure applied for a while.

Re-installed the drive and it works! Thoroughly cleaned the heads "while I was in there." 

[sigma7]

Re-installed the drive and it works!

Nice work; you're quickly becoming a Twiggy expert!