If you use a really hot iron that heats quickly and high in wattage, you can solder without moving the sleepers away.
Also, I have had many people have issues with soldering the joiners, reporting that that the solder fractures over time due to the stresses of expansion and contraction.
An alternative method is leave the joiners there for mechanical alignment, but solder a copper jumper between the sections with some loop in it so motion will not flex the soldered joints.
Greg
The temperatures I get my rail to, the sleepers would melt no matter how fast I was.
I'm not soldering for electrical conductivity I am using it for a mechanical joint, the "joiners" are really only there to align the track pieces and provide lateral mechanical strength, what I am doing is similar to what plumbers do when joining copper water pipe using silver solder.
Not having ready access to rail clamps I have resorted to this method and it is working for me, I only use it on lengths of rail that form a curve with a join in the middle.
I have used the method for nearly 15 years in both a climate where the winters were cold (4C) and summers hot (42C) and in my present climate, winter (10C) and summer (35C), without any fracturing issues.
Fracturing may be an issue in colder climes that I have no experience with low temps except in my freezer.
I anchor the sleepers either side of the joint for added mechanical support and use non soldered joiners, with a 1mm gap between rail ends, at either end of the total length as expansion/contraction joints (if I was looking for conductivity I would use flexible jumper across the joint).
