[R-390] Gear train rebuild help needed......

[Joe Foley]

Just for fun, check the ten-turn counter on the MC Change shaft.  The leaves may not be coordinated properly.

Joe





On Thursday, December 26, 2013 3:24 PM, rbethman <rbethman at comcast.net> wrote:
 
Charles,

I appreciate your input and correction.  My intent was to take the 
"Green Gear" out of the conversation.  It was that simple.

Yes, there ARE equivalent gears in the R-390A.

Bob - N0DGN

On 12/26/2013 3:00 PM, Charles Steinmetz wrote:
> Bob wrote:
>
>> Phil wrote R-390A.  IF that is the case, there is NO green, Geneva Gear.
>
> More misinformation.  The Geneva Drive used in both the R390 and the 
> R390A is not the same as the Green Gear in an R390.  The Green Gear is 
> not called a "Geneva Gear."
>
> The Geneva Drive is what has been suggested as a possible problem in 
> Phil's radio.  It is shown and discussed on pp. 1-2 of Scott Seickel's 
> R390A gear train rebuild tutorial.
>
> The Geneva Drive is a mechanical mechanism that moves a shaft (in this 
> case, the bandswitch shaft) in small steps for each rotation of the 
> driving shaft (in this case, the MC Change shaft).  The 390 manual 
> calls it a Geneva mechanism, while the 390A manual calls it an 
> "intermittent gear."  Geneva mechanisms typically have a pin that 
> engages a slot in the driven wheel. As the drive wheel rotates, the 
> pin enters the slot and turns the driven wheel some fraction of its 
> rotation.  See <http://en.wikipedia.org/wiki/Geneva_drive>, especially 
> the "internal Geneva drive."
>
> The Green Gear in an R390 is a convenience tool that keeps the KC 
> Change gear train in alignment with the Veeder-Root counter while you 
> have the radio disassembled.
>
> Best regards,
>
> Charles
>

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