I'm not sure why you would use silver to plug the fork end. Seems like a waste of material. Leave the ends open and after painting put a plug in with epoxy. I've done that with frames and haven't had a failure yet in 24 years. (Of course "yet" may be the operative word.)
Steve Leitgen La Crosse, WI
On Dec 3, 2005, at 8:05 PM, John Thompson wrote:
> Harvey M Sachs wrote:
>
>> The reason I ask is that the metallurgy of the silver brazing
>> materials
>> I'm used to doesn't favor this application. They are extremely strong
>> and appropriate for filling very small gaps (<0.035", if I recall
>> correctly), where the loads "look like" shear. This would describe
>> bonding lug to tube, for example. On the other hand, as the gap
>> widened, strength decreased rapidly. In addition, the silver I've
>> worked
>> with gets very liquid just above the start of melting, so it is hard
>> to
>> build up a fillet.
>>
>> Brass complements this well: strong gap-filler (fork ends to tubes,
>> for
>> example), has a good viscous range for building fillet radii, etc. I
>> always thought that the rational custom frame makers typically boasted
>> of using silver for the lugged joints, and never claimed to use silver
>> for fork ends, seat stay eyes, etc.
>
> All you say is true, and most builders do only use silver for lugs and
> braze-ons, but at Trek at least our 753 frames used silver everywhere,
> including dropouts and fork ends. The results are more than strong
> enough (never had one of them fail at the dropout/fork end, IIRC), but
> you use almost as much silver filling those gaps as you do in the rest
> of the frame all together. That gets expensive, and I suspect that is a
> significant reason not to use silver there unless required to by the
> tubing properties.
>
> FWIW, only the early Trek 753 frames used inordinate amounts of silver;
> the later production used cast, socketed dropouts/fork ends that only
> required a tiny amount of silver.
>
> --
> John (john@os2.dhs.org)
> Appleton WI USA