http://www.candlepowerforums.com/vb/showthread.php?t=217381
similar but different see the last few posts at least
you can use "power resisters" which come in many flavors, i found some that had FINS on them online , because of the fins, they could handle more power in a smaller size, and they would screw/rivet mount to another surface too, to sync out some of the heat off of them.
http://cgi.ebay.com/Dale-250-Ohm-10-Watt-1-Fixed-resistor-RH-10-Used_W0QQitemZ280310927094QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item280310927094&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A2%7C294%3A50
stuff that looks like this, (not the right values) i think its used in power amps, for audiofiles and stuff, these will handle a lot and still stay cooler.
then there is the big ceramic type Wire Wound 5w and 10w resister you see in the other thread, that you can still get at local parts stores.
combining resistance made easy (sorta):
the other way is to get the 1/2 watt, or the metal oxide 1 watt, and make a Parrelel bundle, depending on the application and location, a bundle of many lower wattage resisters, can be synced to the case easier, or fit in a place, and or get more air across them.
when choosing, prefer to NOT use the carbon type , and prefer to use the wire wound, as they are the most reliable when overheated, the other kinds can LOWER in resistance when overheated or burnt out, making things go badly faster and faster as the resistance goes down.
If they are getting really hot or are really close to the wattages needed through the resister, instead of highly overrated, make sure you leave a bit of leg out of the resister before the next connection, so it doesnt melt the solder at the connection, if it should get that hot. Do wire twists or wire wrap, so if solder comes loose the connection is still held.
Potting to get the heat of the resistance out of the light:
you can do stuff like JBweld (my version of potting) them around the barrel of a light to get the heat OUT.
:grouphug: the heat going out the flashlight case.
Combining resisters Math:
to parellel, many smaller resisters, you just do some math, like this
|---------{~4~}----------|
|---------{~4~}----------|
|---------{~4~}----------|
|---------{~4~}----------|
the four 4 ohms there tied together parellel will make up 1ohm.
|---------{~4~}---------|----------{~4~}----------|
these two 4 ohms in series will make up 8 ohms
and you can still
|---------{~1~}---------|----------{~1~}----------|
|---------{~1~}---------|----------{~1~}----------|
series parellel them too, this makes up 1ohm still, 2 in series 2 in parellel.
and basically each one of any of these combos will spread the wattage of resistance or heat through all of the pieces, so the above digram, in a 1/2watt type would handle ~2watts of total power.
then there are some minor factors, one resister can take more of the heat than the other when they are off from eachother a bit in resistance , the % of accuracy, but basically it works out just as well to use fat high powered, as it does to use metal oxide multiples , depending on the space you have available.
and overrating the wattage handling a LOT when space is avalalble to do so, is always a good idea. so if you really only need 2 watts power handling, and can get a 10Watt in the space, then certannly do so, it wont change the resistance factors just the heat handling.
another way could be to just drop some voltage itself, which in this situation is not as good, but will work ok. get one of them 25AMP bridge rectifyers, and run through at least one Diode in the thing, they are big , its overrated well, and they are potted and sincable so they will handle the heat of dropping about .6-.7volts too, or through the whole thing it will drop twice that voltage , that will lower the total current flow, but not specifically control the current, its different, and will work, but not better in this case.
and dont forget lots of the connections switches , and wiring in a light will already be adding in some resistance, and the BATTERY that you use will be limited in total output too, depending completly on the battery type and age, and condition etc, so you might get away with less resistance than you think., especially with alkalines.
