However, Aurora Tucker carried The Box from the Shustek center in Fremont to the Guest Desk in CHM and hence to The 1401 Team :-))
Let the Adventure Begin :-))

	Iggy Menendez opens the box which has had so many adventures.		Included is the drawing we sent, to help remind us what we ordered ;-))
About Dave Bennet, who did the drawing -	Dave works on the IBM RAMAC team, and the RAMAC has two electromagnetic clutches just like ours to operate the RAMAC arm.		And the Packing List :-))
	And the mandatory warning - Iggy and I agreed we should have died horrible deaths many years ago.		All the above for 100 of these little guys

A quick review of the IBM 729 electromagnetic clutches. Basically, there is a magnetic powder between the clutch plates, and if the electro magnet is energized (electric current driven through the copper windings) the loose powder becomes solid, coupling the two plates of the clutch. When the "German" 1401 came from Germany, there were many discussions of how to bring the tape drives up to reliable operating condition. It was decided to "rebuild" the electromagnetic clutches, in part because the working parts are hidden and of unknown condition and wear. Some of this "rebuild" is described here

To get the electric current into the rotating clutch, carbon brushes are used. This is quite similar to the use of carbon brushes in generators and motors. The brushes slowly wear (get shorter) with usage, and they are usually easy to check visually for sufficient length until the next periodic inspection.
Fortunately, for the "rest of us" these brushes are usually out in plain sight, so we can check for sufficient reserve length.

Unfortunately !! This easy visual inspection feature was not included in the design and manufacture of the IBM 729 Tape Drives :-((

	The entire brush, spring, and flexible copper wire are hidden in a block of opaque plastic material (seems to be "Bakelite"). And to compound the problem, two of the three of the Bakelite brush blocks are rather inaccessible between two of the clutches :-((
	The previous is best case, this is a worse case. Two clutches are 13/16 inches apart. Two brush blocks are in that limited width, with needed clearance and some length for the brushes to protrude to make contact with the slip rings. Iggy says "[This is] the new style brush block, which is very easy to install from the outside of the tape drive...."
	This is a pair of brush blocks with bracket that fits into the 13/16 inch gap between the two clutches closest to the reel of tape. Iggy says "[This is] the 'old' style, where both brush blocks are mounted in a non-adjustable bracket, which is installed from the bottom, then rotated to a point away from the side where you took the picture in #1 pic. above, making it very difficult to secure, attach wires and cap, etc.
	A worn brush with spring and conductive bracket. Brushes that are worn too short arc with its copper slip ring. Arcing causes electrical noise, and pitting of the copper slip ring, making faster wear on these and also faster wear on replacement brushes :-(( The new brush has a long wire pig tail makes for easier handling and soldering. The excess is cut off after soldering. Note the flanges that control the brush in the brush block.
	Iggy is holding a ?Bakelite? brush holder or "block". Note the flange in each brush hole to control the extension of the brush. If this was not there, a worn brush could pop out the hole and get into mischief :-((
	Here Iggy is working with a new brush. Any slip and the brush and spring pop out and onto the floor :-((
	Here an almost restored brush block. The last step is to solder the copper "pig tail" to the brass holder_conductor. Our nice little electronic soldering "iron" had a nice small heated tip for fine soldering, much to wimpy for heating that brass bracket for proper solder flow. Someone will bring their robust soldering "iron" on Wednesday.
	"The proof is in the pudding". Can we get the bracket, brush blocks, with springy brushes into the 13/16 inch gap and get them all lined up on the slip rings ?? Here is my attempt to get the brushes into the gap without snagging on anything and not slipping into the center opening of the clutch assembly. This is difficult under ideal conditions on a work bench. And with the IBM cards as shown, you cannot see to align the brushes with the slip rings. We will need transparent material of about 0.007 inch thickness so we can see and constrain the brushes. Who ever succeeds in doing this with out removing the clutches and shaft from the 729 unit will deserve a "Hero Medal".

Also Dave Bennet came by to ensure that we had received the brushes that he obtained from a vendor (to our specs), and were working OK. We assured Dave that these were fine, and thanked him for his effort in procuring these brushes in such timely fashion.

If you wish, please take a read at my status report attached below, and you can see what it took to get the brush bracket into its position in the 729, and the pain in the neck difficult connection to the wires that Marc labeled "a piece of cake"
(I say a ROTUND NO, NOT A PIECE OF CAKE AT ALL !)

Status Report
Sent: Wednesday, April 13, 2016 6:14 PM
Subject: CHM Tape LONG status

German 1401 System

Marc completed soldering the remaining 2 carbon brushes to the holder in the dual holder (pain in the neck) bracket..... Went to install the bracket on tape #1, and did as follow, with the total of 6 'CE' hands, simultaneously: Loosened the clutches' drive motors and moved the 4 "V" belts out of the way to make room for the next step With the aid of two IBM Cards, carefully formed and positioned, the brush bracket with holders and brushes, was inserted between the front and middle clutches, on the left shaft. This was necessary due to the interference of protruding brush tips and clutch contact rings, so the cards compressed the carbons on its tensioning springs. With much difficulty the bracket was secured on the frame casting, aligned, and tightened. Now came the difficult task of connecting the two wires and arc suppression caps on both brush holders, with very short wires from an unmovable cable harness. Marc continued to excel himself and had this done in less time that it would take someone to tie his shoe laces.... Then Marc exclaimed "a piece of cake!" (as my jaw hit the floor in astonishment!). We repositioned the tape unit to its normal resting place, and after struggling with the "small cables," Glen finally got them all connected. Powered up and tested load/unload/high-speed-rewind, all OK, and NO SPARKS now. (Marc even made a video of this successful process) Stan tested the drive with the program that was registering thousands of errors, now running 'error free!'.... We presume that the previous sparking problem with the old, too short brushes was causing the myriad of read errors. High-fives, kudos, accolades, and applause for all involved in this 3 hour surgical procedure!!

Connecticut 1401 System

In the process of our normal checkout of the tape drives, we noticed that the infamous tape #3 was not loading the tape correctly, it would stop with the tape just beginning to go into the left vac. column, and loaded good on the right col. AND HUNG ! After some analysis and (empirical processes (read: trial of this, that and the other 'usual suspects,') we finally noticed that the left shaft front 'stop' clutch carbons were barely making contact (a repeat of what we had just finished fixing on tape#1 in German Sys.) Adjusted the brush holder in this new style bracket to make better contact tension ('new bracket allows individual brush block adjustment). Tried loading the tape again, and now it would load OK on the left col., but would not load on the right col. After adjustment of both stop capstans. Load/unload works OK. At time of demo, all SEVEN drives working OK (#3 drive in Conn.Sys ok only for demo as Docents know). (BTW, visual inspection gave us the count of FIVE new style brush (adjustable) brackets, and two 'old style pain in the neck' ones.

Glen, Marc, Stan, and Iggy.

Apparently he did, and if you agree, he should order at least 200, or ‘a lifetime supply’, and perhaps some for our friends in Binghamton.

Marc made originally the first replacements, at a great cost of his time, of manual machining, and if Marc agrees, I think that this source that made the previous batch is the way to go.

Iggy

Dave

I would be glad to do the same thing again, or I'll pass on the details to whoever wants them.

These are very pleasant folks and working with them is easy.

Dave

Just a few notes, on our experiences in regards to the carbon brushes on the 729 tapes. Please forward to your guys

Failure symptoms:
    1-sparks flying around the clutches
    2-jerky moving reels on load/unload
    3-tape coming out of columns or dumping at bottom during movement

Things to consider when replacing the carbon brushes:

Power down 729 completely

three different mount brackets :
    1-simple on rear clutches
    2- more elaborate single mount for the two forward clutches
    3- complex mount holding 2 mounts for the two forward clutches (each shaft)
    4-mark with felt pen the position of the brackets to facilitate alignment when re-installing.
    5-place rag under the area to catch falling screws

Note position and direction of carbon brushes’ holding the assembly.
Note the spring’s routing with the wires from the carbon brushes.

When re-installing, make sure to use a piece of punch card to ramp up the brushes past the ridges of the contact rings of the clutch.
The carbon may chip or break if forced past these ridges.

When doing final alignment, make sure that the 2 brushes are totally making contact on the copper rings, and adjusted to the gap spec. between the rings and carbon holders. (Spec in the 729 manual)

You will notice that one or more individual, has the manual dexterity and patience to do this right and in less time… perhaps have that individual do most of these replacements. ( in our case, Carl and Marc were the ones blessed with these qualities)

One more tip, on some 729s, there is a metal box on the top right side, bolted to the frame; this box can be temporarily disconnected and removed from the frame, for easy access to the clutch brushes.

It is a difficult task, but well worth the effort in the long run.

Iggy