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Soldering & bits dropping off!

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Bill Dawes23/01/2011 19:16:48
605 forum posts
I am coming to the end of my first ME project, a Jan Ridders simple 2 stroke engine.
It has taken 2 years to get to this stage, not all working on the project of course, fitting in between work, DIY, holidays, visiting relatives etc etc, a familiar story no doubt to many others. My question is concerning soldering. My soldering skills are of the DIY plumbing variety so have a few new techniques to learn. When I came to solder up the petrol tank I struggled with avoiding bits dropping off that I had previously soldered.
My torch is my trusty butane 'Camping Gaz' type which was ok as far as heat required for this job. In preparation for greater things I have bough a Sievert PMPX torch for use with a propane bottle. Greater things I have in mind is a boiler and bearing in mind my 'bits dropping off' problem with my petrol tank how on earth do you avoid this with boiler tubes etc. (These would be silver soldered of course whereas my Ridders engine is soft soldering) Is it a case of larger higher heat input items first?
Bill Dawes
JasonB23/01/2011 19:46:19
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25215 forum posts
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With soft soldering you may need to add the odd rivit or screw to hold items in place so they don't move even if the solder gets softened buy subsequent heating. You can also wrap a damp cloth around parts you don't want getting hot as it acts as a heatsink.
 
With silversoldering you can again use the od rivit or bronze screw to hold boiler parts in place. It is also to step solder by using solders with different melting temps, highest would be used first then the lower melting alloys.
 
Jason
Terryd23/01/2011 21:40:19
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1946 forum posts
179 photos
Hi Bill,
 
you can also get different melting point soft solders apart from the silver solders that Jason mentions. From my model locomotive work in 00 gauge building brass kits I have a number of solders covering a temperature range from 44 degrees C up to around 230/240 degrees C with several in between. I would solder the larger items with the high temp solder then work down to the very small parts using the lower temperature solders as much less heat (different to, but linked to lower temperature) is required.
 
Also it is not a case of one gas torch fits all sizes. I have and use several, including a large Sievert propane (with several nozzles), a normal size butane torch, a small type of butane similar to the ones sold for kitchen use and a pencil torch as well as a range of soldering irons. it also depends on timing and practice. Don't give up just keep trying.
 
You can also use 'bands' of black, soft iron wire to strap parts together while soldering (both soft and silver). I use the stuff that florists sell on reels. When using this, make a small loop in the middle of the wire (twist once or twice) then wrap the parts, twisting the ends of the wire (very malleable - use fingers only) the loops made first can then be twisted to tension the wire around the parts after wrapping. Several wires can be used around different parts. Be creative when planning your soldering.
 
Best regards
 
Terry

Edited By Terryd on 23/01/2011 21:45:28

KWIL24/01/2011 09:00:41
3681 forum posts
70 photos
Once you have tried the step soldering route, you may discover that with care and your now increased skill, you can raise the general temperature (but not to the solder melting point) of the article and then very locally extra heat to raise to soldering temperature that area where you now want to solder the next stage. You can certainly work your way along a line of tubes for instance, however all must be properly fluxed and with sufficient clearance around the tubes for the solder to flow through the joint.
Ian S C24/01/2011 10:42:40
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7468 forum posts
230 photos
an interesting exersise in soldering was given to us as Boy Enrrants in the RNZAF, we were given 36 one inch long x 3/16" dia peices of copper wire, the thing was to first solder 12 bits into a cube, then solder a cone of 4 more bits on each face of the cube, all using a copper bit, not an electric iron, an a stick of 50/50 solder. Ian S C
Peter Gain24/01/2011 16:35:29
103 forum posts
Ian, that is certainly an interesting excercise! Did you pass?
PG.
mike os24/01/2011 21:06:33
3 forum posts
many methods you could try
 
as already mentioned different heat sources can make a big difference esescialt those with very small hot flames to produce localised heating.
 
also try heat sinks on teh parts.. small bolt or block of metal to take heat away..
 
also try welders heat shield gel
 
for small parts a large soltering iron can be usefull too ( copper head, heat in flame/oven, not electric)
Bill Dawes29/01/2011 19:57:30
605 forum posts
Thanks to all for the replies. Another question re silver solder. Is my understanding correct that cadmium is (or was) added to reduce melting point and once melted and the cadmium released into your lungs, the re-melting point is higher. If this is the case what, if anything, replaces these properties in non cadmium solder?
 
Bill Dawes
JasonB29/01/2011 20:19:48
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25215 forum posts
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Teh cadmium helps the solder flow, the cad free does not flow quite as well. The silver content has more effect on melting temp.
 
J
KWIL30/01/2011 09:54:43
3681 forum posts
70 photos
Do your silver solder work in a ventilated area and the cadmium problems can be dealt with by the free air.

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