[GreenKeys] TD gears for the dual head 28 ASR

[jack hart]

If you put a three-speed shift in the ASR, it will run the dual-head TD at the shift's speeds. Normally, you need to gear the TD for 100 wpm when you have a shift. I have the dual-head TD and know it works that way. Somewhere I have the 67 wpm gears, woo.
 
Jack K0TTY


--- On Mon, 2/4/13, gfmurphy at earthlink.net <gfmurphy at earthlink.net> wrote:


From: gfmurphy at earthlink.net <gfmurphy at earthlink.net>
Subject: [GreenKeys] TD gears for the dual head 28 ASR
To: "Greenkeys" <greenkeys at mailman.qth.net>
Date: Monday, February 4, 2013, 4:15 PM



#yiv1009496446 body{font-size:10pt;font-family:arial, sans-serif;background-color:#ffffff;color:black;}#yiv1009496446 p{margin:0px;}



#yiv1009496446 body{font-size:10pt;font-family:arial, sans-serif;background-color:#ffffff;color:black;}#yiv1009496446 p{margin:0px;}


#yiv1009496446 body{font-size:10pt;font-family:arial, sans-serif;background-color:#ffffff;color:black;}#yiv1009496446 p{margin:0px;}


#yiv1009496446 body{font-size:10pt;font-family:arial, sans-serif;background-color:#ffffff;color:black;}#yiv1009496446 p{}


#yiv1009496446 body{font-size:10pt;font-family:arial, sans-serif;background-color:#ffffff;color:black;}#yiv1009496446 p{}
Greenkeyers:
There's been some discussion about gearing for the 28 ASR that is equipped 
with the dual tape reader heads. Presumably, the next owner might like 
to run the machine at 60 WPM. The standard 161293 gear set will run the
keyboard and page printer at 60 WPM.  The tape reader gear set is another
matter.  The problem is that Teletype Corp. never made 60 WPM gears for the 
dual TD base that is in this machine. They made 4 sets of gears: 107 WPM 
for 7.00 pattern, 67 WPM and 100 WPM for 7.42 pattern and 88 WPM for 8.5 
pattern. If there had been a requirement for 60 WPM gears, they would have 
made them. There was no physical or interference issue with making 60 WPM 
gears for dual head tape readers.

The gear problem stems from the need to drive the 2 tape readers from a
jackshaft. The jackshaft was required because of clearance issues. In
order for the jackshaft to be turning in the proper direction, the shaft
that drives the jackshaft has to be turning in the opposite direction.
That shaft - let's call it the front-rear shaft - is the same shaft that is on
every Model 28 ASR TD base.  The front-rear shaft transmits rotary
motion from the TD base speed change gears to the tape reader. In a
standard single head tape reader, the front-rear shaft rotates in a
counter clock-wise direction as viewed from the front of the machine.
In a dual head tape reader, the front-rear shaft rotates in a clock-wise
direction. The opposite rotation is accomplished by changing the
'hand' of the gears. Let's look at standard 100 WPM ASR TD base gears:
There is a 158002 steel pinion with 11 teeth and a 158001 fiber gear with
33 teeth. They are both right-hand gears. The 100 WPM gears for dual 
tape reader operation are the 170293 steel pinion with 11 teeth and the
170297 fiber gear with 33 teeth. They are both left-hand gears. So, even 
though the single head and dual head gears have the same number of teeth, 
the rotation of the front-rear shaft is different in each case. Check with 
Google or Wikipedia for further clarification of the 'hand' of gears.

You cannot take a set of 60 WPM gears (158005 pinion and 158006 gear) and
install them on a dual head tape reader base and expect it to work properly. 
The gears will fit but the front-rear shaft will turn in the wrong direction.

Jerry Murphy


-----Inline Attachment Follows-----


______________________________________________________________
GreenKeys mailing list
Home: http://mailman.qth.net/mailman/listinfo/greenkeys
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:GreenKeys at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20130204/3852dfc0/attachment-0001.html>