[R-390] Legible Question R390(A) Gear Chemistry

[Bob Camp]

Hi

Brass = copper (50 to 70% + zinc
Bronze = copper (88%) + tin 
Nickel Silver = copper (60%) + zinc + nickel 
Gunmetal = copper (~85%) + zinc + tin

Both brass and bronze *may* have other stuff in them. Bronze is often a mix of several materials in addition to the basic copper and tin.
The above is hardly an exhaustive list of all copper alloys. Since alloys that have both zinc and tin in them are possible, you can have 
stuff that could be either a brass or a bronze depending on your point of view. 

Best bet - they are some sort of brass. Bronze is a mess to machine and brass is very easy to work with. Gears are made on gear cutting 
machines. It’s a process not unlike other metal machining. Gear cutting machines are much happier working with brass. 

Bob

> On Dec 10, 2016, at 3:48 PM, Glenn Scott via R-390 <r-390 at mailman.qth.net> wrote:
> 
> Sorry for the last post disaster..
> 
> 
> 
> Questions for the group,
> 
> 
> 
> 
> There are a number of gears in the mech assembly of the R390 series receivers that are brass colored.  I've heard these called bronze and/or brass for decades. Does anyone really know the actual chemistry involved in the manufacturing of the alloys used in those gears. 
> Passing a strong Neodymium magnet across the surface, you can feel a slight attraction as you'd expect from a high grade of near pure silver, however, the attraction does not pull the magnet to the gear. 
> Is this due to a small iron content in the alloy or does brass and bronze exhibit the same characteristics as near pure Ag?
> In my experience brass would be too soft for use in those gears without there being other metals in the alloy;  I am NOT sure about the characteristics of Bronze.
> These are very hard gears and have held up very well in most of the R390 series receives I have restored during the last 20 years.  I'm just curious if anyone can confirm the provenance of these gears?
> 
> 
> 
> 
> Regards,
> 
> 
> 
> 
> Glenn Scott WA4AOS 
> DSM Labs
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