Soldering aluminum to brass

A buddy brought me a motor from his golf cart that wouldn't run. Opening it up revealed that one end of the field winding had come unsoldered from the
bolt head that served as a terminal. The bolt was brass, and the field winding (not really wire, but insulated bar material about 3/16" square) appeared to be copper, with the end nicely tinned. After a few unsuccessful tries at soldering it with 60/40, I realized that the winding was not tinned copper, but aluminum! What solder and flux (if any) should I use to solder these two dissimilar metals together. I'm using a Henrob O/A torch with its smallest tip.
John
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The process you want to do uses a technique called "friction tinning" with 90/10 followed by pad wiped solder 63/37. This is the procedure we use for soldering aluminum sheath high voltage oil filled cables to the plumb bell joint.The real trick is clean , and clean. Did I mention clean? Additionally you must really watch your heat or you will re-oxide the aluminum and separate the solder alloys. The technique works because the 90/10 is worked into the aluminum with a stainless steel brush and the top coated with the 63/37, the final connection is made with 40/60 without disturbing the previously deposited alloys. I have personnel used this on 60kV to 230 kV cables. We also use thermite welding for copper connectors to aluminum flat buss bars and IPS round substation buswork.
Good luck Pete

it
unsuccessful
tinned
solder
its
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
TIN is the best solder for Al. You can find some at a common hardware store - often there is flux their on the self.
Had to use that in making grounds on Al chassis :-)
Martin
--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer snipped-for-privacy@pacbell.net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.