[GreenKeys] Main shaft fiber gear

[John, W9DDD]

I think ya'll have answered my real question that I forgot to put in my 
original post.

I could use a fiber gear to replace a damaged Nylon gear.  I haven't 
checked, but I suspect the same steel gear is used on the intermediate 
shaft that drives the main shaft for either a Nylon or fiber gear on the 
main shaft.  I need to check when I get to putting things back together, 
but I think I have a chipped tooth on the Nylon gear.

I probably also forgot to mention that these fiber gears I found appear 
to be NOS.  So I assumed they had been spares.

Oh, another question, why would I have about 20 lbs of clutches.  These 
appear to be pulls although a few are in bags with a card with the 
federal stock number.  I'm thinking to save a couple of each type and 
donating the remainders to the recycler.

John, W9DDD

On 10/16/2020 2:52 PM, Jerry Murphy wrote:
> 
> 
> 
> Fiber gears (more accurately called phenolic gears) are very durable.  Check
> your Model 14 and 15 machines to see how fiber gears hold up. The problem
> with any gear that has its tooth form cut or ground into it is the expense
> involved.  Lots of operations involved to get a finished product.  Teletype
> replaced many of the fiber gears in the M28 line with molded nylon gears.
> A very expensive mold could turn out lots of inexpensive gears. No need to
> cut gear teeth since the teeth are molded in.  The original M28 KSR/RO speed
> change and intermediate gearing sets consisted of a metal pinion and a fiber
> gear.  When all four gears were replaced with molded nylon gears the result
> was a quieter and cheaper gear train.  Nylon gears would eventually shows
> signs of wear while the corresponding metal and fiber gears would rarely show
> signs of wear.  (Nylon gear wear was most obvious on the smaller gear of the
> pair.)  Teletype recommended that nylon gears only mate with other nylon
> gears.  Combining metal or fiber gears with nylon gears was not recommended
> even though the combination would work.
> 
> In the interests of systemwide compatibility, I would expect that a shop
> doing TTY repair and overhaul would replace perfectly good fiber gears (and
> their steel pinions) with late style nylon replacement gears.
> 
> In the end, the cheaper and quieter nylon gears won out over the more durable
> but more expensive fiber and metal gear sets.
> 
> Jerry Murphy
> 
> 
> -----Original Message-----
>> From: "John, W9DDD" <w9ddd at tapr.org>
>> Sent: Oct 16, 2020 8:55 AM
>> To: Green Keys <greenkeys at mailman.qth.net>
>> Subject: [GreenKeys] Main shaft fiber gear
>>
>> A question for the folks that serviced 28s back in the day.
>>
>> As I'm still sorting through the haul from a year ago, I find I have 7
>> of 150439 60 tooth main shaft gears.  You don't find that in the
>> documents unless you have an early issue (1149B original).
>>
>> So the question is ... did these fail a lot and therefore was changed to
>> Nylon early on?  Why else would a person doing service have this many
>> when most of the other items in the batch were at quantity 2 (common
>> screws, nute and washers being an exception)
>>
>>
>> -- 
>> John, W9DDD