Previously: Manual for Documation TM200 punched card reader Restoration of the mechanics of my TM200 punch card reader progresses. There's a writeup here: http://everist.org/NobLog/20180922_data_in_holes.htm#tm200
Currently I'm machining a mold to cast new pinch rollers - and there's the rub (ok kill me.) The old rubber rollers were decayed to gunk, so there's no chance of measuring their original dimensions. >From the mechanics, if they were just touching the steel capstan rollers >they'd have been 27.1 mm Dia. The mechanics has no adjustment or spring tension on the pinch roller positions. Their shafts are in fixed position, so all the spring is in the rubber of the rollers. Someone who recalls seeing one of these working, says the rubber rollers turned while the capstans turned, so they must have been actually pressing on them. But how much squish? Experimenting with a similar diameter silicone roller (from a photocopier) it semes like 0.2mm of 'squish' without a card, seems to give a good grip on a card. The cards are 0.1mm thick. That gives a resting roller diameter of 27.5 mm. Obviously too much 'squish' is undesirable since the roller would get permanently deformed when left idle in one position. The 2-part silicone I'll be using for first try at casting rollers has a cured Shore A durometer rating of 60. I'm hoping someone might have some knowledge of how much punch card reader pinch rollers should press against capstans. Does 0.2mm squish seem right, or am I way off? I can try multiple iterations, boring the mold out a little more to make the rollers bigger. But it would be nice to get it right first time. I don't yet have a TM200 manual, but the M200 manuals seem to cover pretty much identical mechanics. They give no dimensions for the rubber rollers, no mention of the contact pressure, or even diagnosing if the rollers are worn. There are significant differences in the electronics between the M200 and the TM200. I'm really going to need a manual with schematics once I get to debugging and interfacing the electronics. Bitsavers only has M200 manuals, and Al Kossow doesn't seem to have had any luck with > I'm pretty sure I just saw a paper copy of the TM200 manual > which is different from the M200. I'll have to dig around to > try to find it again. If anyone can suggest a source. I'd like to buy a paper copy. Which I'll scan and post at bitsavers etc. Guy
