Experts help needed on RM2 coil builds

[pdib]

just in case . . . . NO on the .8Ω coil. That would draw 5.25 Amps from a battery rated at 4 Amps

 

[oplholik]

So, at 1.2Ω, I'm about as low as I should go on the Ω's.

 

[johni]

1 ohm would be pushing the battery pretty hard. 1.1 or 1.2 would be safer.

 

[NicoHolic]

Voltage / Current = Resistance
4.0V (under load) / 4.0A rating = 1.0Ω at the lowest

Odds are you won't see as high as 4.0V under load,
but it's a reasonable number to use for calculations.

 

[pdib]

So, at 1.2Ω, I'm about as low as I should go on the Ω's.

I think you might have some good results going up a gauge (or even two) in wire. You could try a 6 or 7 wrap of 29g. Or you could try a 6 of 30g. Also, you could drop your "what you wrap it on" (ID) to 1.5 mm.

NicoHog makes a valid point, when you factor in voltage drop and such; there's room there. I've always used larger batteries, so I don't need to consider "grey areas". I wouldn't give any advice that splits hairs. [walks away with hands in pockets, whistling a tune, admiring the sky]

 

[oplholik]

I think it was the 14500 whose max. continuous discharge rating wanted a coil @ or over 1.1Ω.

Just checked; yep, its a 4 Amp rating. This would go a long way to explaining why your wire isn't glowing very quickly. I had thought that (I looked at your pic &) an 8/9 wrap was a bit much anyway. Its probably a combination of things. The battery (ESPECIALLY if not fully charged), a little too much wire (or too thick a gauge), and a little loose on the micro wraps contacting.

yeah, I was trying to get the coil tightly compressed, and this was the best I could get it, by heating the wire and compressing
the wire in a needle nose pliers.

 

[Stringer63]

10 wraps of 28g k around a 1/16 drill bit gets me 1.2 ohms. The drill bit also helps with creating a tight uniform coil.

 

[pdib]

Yep. When wrapping on a drill bit, each wrap should almost want to land on the spine of the previous, and sort of slide into place next to it. Also, torch/fire your wire before you wrap it. It will hold it's shape better.

 

[supertrunker]

so just use what i do! 32g kanthal and 4 wraps on 3mm silica! HA!

btw - torching it all is a good idea and i have tried both ways, when it is all torched, the silica cuts really cleanly and the coils need the minimum of prodding (good old safety pin) until they all glow evenly.

T