[GreenKeys] 404 OPM Speed for TT-4/TG

[Brenda Gentry]

Decades ago, I had a ready source of Kleinschmidt motors that were worn 
out or no longer met specifications and used them for experimenting and 
learning . Increasing the speed was easy to do with the adjustments 
provided, a notable increase was possible. If the increase is not 
enough, try using a piece of thin stainless steel wire to bind and 
collapse one turn of the governor spring. That will increase the spring 
tension and the speed setting. Don't use too much wire to bind the 
spring, it will cause unacceptable unbalance.


B. Gentry, KA2IVY




On 3/8/26 1:13 PM, Duncan Brown wrote:
> Pete,
>
> I will check our stock at the AWA (Antique Wireless Association - not 
> to  be confused with Amalgamated Wireless Australia) Museum when I am 
> there on Tuesday.  I know I have extra gears, but don't know offhand 
> if there are any 404 opm gears.
>
> All mechanical TTY machines can receive over a +/- 10% speed 
> variation, using the Range Control to adjust when the selector magnet 
> reads the data.  So your TT-4 can copy 66wpm with the 368 opm gears 
> (just turn the Range control down to about 20), but of course you will 
> need the 404 opm gears to transmit 66 wpm.
>
> You could also try increasing the motor speed by about 10% while still 
> using the 368 opm gears.  I don't know how increased speed would 
> affect the life of the motor or brushes.  But since the unit was 
> designed to work 24/7, and as long as you only use it a few hours a 
> day, I wouldn't think it would affect its life significantly.
>
> Good luck & have fun,
>
> Duncan Brown, K2OEQ
> USASA    31J30
>
> Antique Wireless Association
>  Communication Technologies Museum
>    Asst. Curator, Commercial Equipment
> (also chief TTY op & repairman)
>
> i-Telex: 212503
>
> www.antiquewireless.org
>
> AWA Youtube channel: 
> https://www.youtube.com/channel/UCX55peBhzeX1qps_VYXdLBA
>
> Virtual AWA Museum TTY Tour: https://www.youtube.com/watch?v=TpB6jM90VV8
>
>
>
> On 3/8/2026 6:17 AM, Peter Leonard wrote:
>> Hello all,
>>
>> I need a gearset for a TT-4/TG to operate at 404 OPM / 66WPM / 50 
>> baud. I am happy to exchange a 368.1 OPM / 60 WPM / 45.45 baud set 
>> and a 600 OPM / 100 WPM set. The TT-4 manual states that the 368.1 
>> OPM set is normally fitted and the 404 OPM set is held inside the 
>> machine. My machine is fitted with a 368.1 OPM set holds a 600 OPM set.
>> I am located in Adelaide Australia and am happy to pay parcel post 
>> both ways.
>>
>> Kind regards,
>>
>> 73 Pete   VK5XP
>>
>>
>> Peter Leonard
>>
>>
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