Update 3, 7 September 2015 (Wipe and Melt)
I am still using the 'refurbished' old soldering tip of my Goot soldering gun and have been successful. Soldering is no longer as difficult as it used to be and I am keeping my new soldering tip as a spare.
(The old soldering tip was refurbished by Adrian. He did it by repeatedly inmersing it in a solder bath at KC Tan's office. One half is shiny, the other side is speckled even after scraping, especially at the point. Its condition is not perfect but is good enough.)
Now I solder only small joints for small models but I think it would work equally well on larger joints. This worked well for me even when using the 'refurbished' tip:
wipe and melt new solder to the gun 1) immediately when the gun is heated, 2) every now and then when the gun is switched on, and 3) immediately when the gun is switched off.
A successful 'wipe and melt' operation is to observe a small blob/film of solder on the soldering gun and it should be performed frequently during soldering jobs. A wipe and melt operation is performed immediately before :
- tinning.
- soldering the tinned parts together.
- de-soldering.
The reason for a small fresh blob/film of solder on the soldering gun is two folds. Firstly, that solder conducts heat more efficiently because its surface area is larger then a bare tip is, irrefutable. Secondly, I think that fresh solder has some flux that is still active for a few seconds after melting and this helps greatly.
My soldering jobs were stiff and heavy. I was afraid that my soldering jobs would come apart so I fed solder repeatedly until I get a sizeable solder blob without even thinking. Not only that, when I soldered wires, the solder would seep into the wire that is beyond the joint, making the wire stiff near the joint and this is no good if I wanted flexibility at the root of the wires. When I have a sizeable blob of solder, it caused problems with heat shrinking. The heat shrink sleeves could have already shrunken because I had allowed the tip to be in contact with the job for a long time. Another problem is I may have to trim the solder blob because the sleeves could not fit through. The solution to ward off these problems is to resist the urge to add solder by tinning all jobs before soldering.
- So long as the jobs are shiny after tinning, I accept that tinning process as successful completed and do not add more solder.
- After the jobs are soldered, I do a tug test. If the job didn't come apart during the tug test, it is successful. (Do not add more solder, I tell myself, "like any good glue joint, a joint is best with the least glue.")
- If the job came apart during tug test, inspect if the jobs are tinned properly and perform 'wipe and melt' operation before soldering again. So far I noticed my failures to be due to the fact that I didn't bring the jobs together properly resulting in spot soldering.
Update 2, Mar 2014
I bought new soldering tips for my Goot soldering gun from Sim Lim Tower, at $14 a piece.
Before use, I prepared the shiny tip as I learned by using up almost a whole foot of soldering lead.
I soldered a T connector, wiping the tip with sponge along the way. I coated the tip and switch off the iron.
Next time round, I noticed that while the tip is of the dull silver (like the solder), there are some specks of rust.
I heat up the iron, coat the tip with more solder, soldered another T connector and stuff, switch off the iron, but coat the tip with solder, using the residual heat.
Update 1, 20 Jan 2014
I saw a couple of videos on soldering. Two part video by Al Johnstons (put up by Hobbylobby) and the other by a slightly younger old man ("basic soldering for RC model" from Youtube. I picked up some tips (or even if it was already picked up, I think I have a better understanding of them) and had a go at soldering the small Turnigy motor.
- Pre-tin the components. Well, pre-tinning the wire part is obvious, but how do I pre-tin the shiny bullet connector? I couldn't think this through, so I didn't.
- Soldering jig. I clamped the 3 wires on the store-bought soldering jig, with wooden ice cream sticks in the steel jaw (Al used a wooden block and wooden clothes peg).
- Scrape the tip. I used NT cutter to scrape the tip of my soldering gun (Al said soldering gun is overkill)
- Introduce additional flux on the 3 wires.
- Wriggle/swirl the bullet connectors over the flux coated wires.
- Introduce flux on soldering tip and heat up.
- As soon as flux starts smoking, introduce the solder all over the tip (both video uses either 1/32" or 0.7mm rosin cored solder, mine is around there, maybe 1.2-1.5mm? Running out of solder soon, time to buy thinner solder and this time, an entire coil).
- The fumes were very quick. From the old man (younger, RCmodelreview), he said quick fumes were a sign of too hot a tip (high temperature). Wipe tip on wet sponge.
- Introduce solder again to the tip (what got me thinking this time is when Al said he made a blob on the solder tip. This makes sense as the liquified solder will flow easily) and touch one of the wires. On contact, introduce solder again. Once solder liquifies, remove solder and tip and it is done.
- Then it is wiping on wet sponge, solder to tip, touch wire, add solder, liquifies solder, remove solder and tip and repeat for the last wire.
- I have made it so that the ends of each wire has a bit of blob of solder, perhaps it is not necessary.
- Then a bullet connector is gripped on the other metal jaw of the jig. This was brought to one wire.
- Wet sponge, solder tip, tip on pre-tinned wire, solder introduced, solder liquifies, remove solder, remove tip and repeat for the other two bullet connector.
- Switch off, wet sponge, solder tip. Store when soldering gun is cool.
Perhaps I will clean the tip of the soldering pencil and see how it works.
Original (November 2013)
I often failed in soldering connectors and wires for the motor and esc. The soldering gun or iron would not transfer heat sufficiently and quickly, I had to trigger up the soldering gun, and would press the joints in the hope that the solder will melt. It definitely does not look like I was doing it right from what I read about soldering.
The first to blame was the tools and equipment.
I found that I had better success rate when the soldering gun/iron was brand new, but it gets longer and longer to solder something together. So I figured it was the soldering tip, it wasn't 'shiny' anymore and took to use emery cloth to sand the tips. It took me very long to sand the tip. I would use a piece of emery cloth (and later, sandpaper), loop it onto the conical tip and with the sandpaper held in my thumb and forefinger, twisting the sandpaper against the conical tip. It took too long, it was messy and I don't like tearing small pieces of sandpaper out of a single sheet (and I often misplace the used bits of sandpaper).
I went to a hobby shop's website and read that they are selling a soldering jig, so I bought one. It is one of those twin chrome clamps on a base, the idea being to hold the two pieces you wish to join, then with the soldering tool on the masterhand and a piece of soldering lead on the other hand, proceed to solder. When reading reviews of certain products, I tend to get swayed by them, thinking this is exactly what I need. Well, it helps to hold the pieces in place and I didn't have to get a third or fourth hand or to cut a piece of solder, place it right against the joint and push it ever so gently with the soldering tool against the lead, holding breath or breathe shallowly less the force applied is unstable. Did I do a good job after I got the jib? No.
The solder core that I use has a flux core, in the interest of good soldering, I bought a small tub of soldering flux, to clean the joints while soldering. I feel better using it because I believe anything I read, and visually there's smoke and that seems to indicate progress.
Then I read from the internet about sponge! Ah! This must be it! Or so I thought. The tip remained dull and soldering was still a mundane task and goal unachieved.
I read a bit more, talked to Mr. Tan, went to his office and tried soldering with his tool, equipment, solder and flux (successfully), seen a few video on soldering and decided that the reasons for my failure were:
- Did not tin the soldering tip when new. (well, too late now is it?)
- Did not constantly swipe against the moist sponge while soldering. (but no amount of swiping seems to help now)
- Did not tin the parts to be soldered. (but if I do that with the bullet connector, the solder will fill the cavity and then I can't insert the wire)
I figured that the biggest reason was my tip was dirty. My solution last night (took me more than an hour from setting up my gear and packing up, to solder 18 bullets on 2 motors and 4 ESC):
- Ditch the sandpaper, scrap the tip with a blade. Repeat when the soldering time gets too long (even when it is hot). Only the tip of the conical tip is necessary, no point cleaning the whole conical tip. At the beginning I thought head transfer quickest if I rested the conical side against the joint, so I cleaned the whole cone. I observed the cone gets blacken easily, the solder beaded up and I might as well just introduce the solder to the tip of the cone.
- Throughout the session, tin the tip of the cone over and over again.
- Keep rubbing the tip on the moist sponge.
- Apply small amount of flux (toothpick) on surfaces to be soldered.
- Position them using the jig. To prevent heat loss through the metallic jaw and causing a long time to heat up, clamp the bullet connector between two popsicle sticks. The wire was simply gripped directly with the metal jaw, to dissipate heat. The bullet is positioned below while the wire at the top, so that the solder can flow down into the bullet's cavity.
- Rest the tip of the soldering gun on the bullet where it meets the wire, introduce solder, run up the molten solder so it will fill the bullet's cavity.
- At end of session, try to load the tip with solder because maybe this will 'protect' the tip and be ready the next round.
The solder joints are 'shiny' enough, not professional, maybe a B grade, which isn't too bad. While soldering, I was afraid that the molten solder might not be sufficient to fill the cavity, and sometimes I spotted small pinholes in the solder joints, so I re-introduce more solder but that became excessive when solder ran off the outside of the bullet connector.
More practice would be needed but at least I am solder capable now.
What to build? I chose to build the Cootie. 19gm including 5gm battery. It flew successfully on 22 Aug 2015. Very little power is needed, any excess results in climbs. I adjusted the thrust angle by sliding the stand-off within the fin. My battery has to be placed far behind then the position indicated on plan. It was basically done on 21 Aug 2015. I deviated from the instructions by having the keel on top of the wing. But the joint was too weak so I added flying thread by looping around the landing gear wire and tying it to the spreader boom. 
