Number of wraps for resistance

[Danny55]

Hi guys.

Something I don't understand. I use SS 317L wire in 24, 26 and 28 gauge. Whenever I build coils, the resistance is always different from the resistance that the Steam coil calculator tells me it should be for a given number of full wraps.

For instance, I just built dual coils with 26 gauge SS 317L, 3mm internal diameter. I was aiming for under .3 ohms and the calculator says 7 full wraps for a 0.27 ohm build. So I did 7 wraps per coil and it's come out as 0.45 ohms.

On the calculator, 12 wraps would give 0.45 ohms.
Interestingly, if I change to Kanthal on the calculator, it says 6/7 wraps.

I've had this wire for years and it's SS 317L I ordered from a reputable British place called the Crazy Wire Company.
So I'm assuming it is actually stainless steel I have. So why is the calculator so wildly different with the wraps? I get the same reading on two different mods.

 

[Beamslider]

I put 317L SS 26 gauge in steam engine. 0.3 ohm, 3mm core and it says rounded to 4 wraps.

 

[Beamslider]

Sorry ignore that I just noticed you are using dual coils. Which would be 8 wraps shown by steam engine.

Maybe the wire you have isn't ss317l

 

[Punk In Drublic]

Hi guys.

Something I don't understand. I use SS 317L wire in 24, 26 and 28 gauge. Whenever I build coils, the resistance is always different from the resistance that the Steam coil calculator tells me it should be for a given number of full wraps.

For instance, I just built dual coils with 26 gauge SS 317L, 3mm internal diameter. I was aiming for under .3 ohms and the calculator says 7 full wraps for a 0.27 ohm build. So I did 7 wraps per coil and it's come out as 0.45 ohms.

On the calculator, 12 wraps would give 0.45 ohms.
Interestingly, if I change to Kanthal on the calculator, it says 6/7 wraps.

I've had this wire for years and it's SS 317L I ordered from a reputable British place called the Crazy Wire Company.
So I'm assuming it is actually stainless steel I have. So why is the calculator so wildly different with the wraps? I get the same reading on two different mods.

Is 0.45ohms the resistance per coil? Do you have a Vernier Caliper to measure the gauge/diameter of your wire? 25 awg, or 0.455mm wire is only 0.05mm larger than 26 awg/0.405mm. Using 25awg SS317 with your coil properties yields a 0.454 ohm coil.

 

[sonicbomb]

Are you positive the size of the mandrel you are wrapping on is what you think it is?

 

[Danny55]

Is 0.45ohms the resistance per coil? Do you have a Vernier Caliper to measure the gauge/diameter of your wire? 25 awg, or 0.455mm wire is only 0.05mm larger than 26 awg/0.405mm. Using 25awg SS317 with your coil properties yields a 0.454 ohm coil.

I don't have a caliper to measure but I'm pretty sure they wouldn't have sent me 25 gauge. I think each coil must be 0.90 as the total coil resistance has come out at 0.45 ohms. Dual coil for 0.45 ohms at 26 gauge says 12 wraps per coil and 25 gauge says 15 wraps per coil. So whichever gauge wire I have it, the calculator is saying way more wraps than the 7 wraps per coil on mine. I'll check each coil tomorrow. I suppose it's possible I could have accidentally given an extra wrap to one of the coils which might be the issue?

Are you positive the size of the mandrel you are wrapping on is what you think it is?

Yeah, I use the coil master to wrap and I selected the pin with 3.0 printed on it.

 

[uthinkofsomething]

NM

 

[louiesquared]

Does the resistance fluctuate when you heat the coils?

 

[ScottP]

The question no one has asked yet...do the legs come off of the same side of the coil or opposite sides?

If they come off of the same side and you count the wraps at the top you will have 7 if you count the wraps at the bottom you will have 6 (a 7/6 wrap). If they come off the opposite sides the top and bottom counts will be the same (a 7 wrap). Because the full 7 wrap has a 1/2 wrap more than the 7/6 wrap, it will have a slight bit more resistance.

 

[Danny55]

I think you're onto something Scott. Clearly I'm doing my wraps inaccurately. Here are two photos, one of each coil after I removed the wicks


It seems I have 8 wraps, I don't know if they're counted as full or half? I went for 7 per coil though. I've tested each coil separately and one is showing 0.88 ohms and the other 0.85 ohms. I guess they need to be precisely the same?

 

[Danny55]

Does the resistance fluctuate when you heat the coils?

Doesn't fluctuate in wattage mode, a solid 0.45 ohms. However in temp control, it goes to 0.51 ohms.

 

[untar]

For a full wrap the legs will face in opposite directions, you can easily understand by doing only one wrap, ie the wire goes around the mandrel exactly one time, not more not less.
Half a wrap leaves the legs facing in the same direction (again if you do only half a wrap on the mandrel so that exactly half of it is in contact with wire then the legs face the same way).

 

[ShamrockPat]

 

[Danny55]

Thanks for the explanation and photo guys. So I guess mine is 7 and a half wraps right?
And I guess there'll always be a half wrap on a Velocity deck like my OBS since the legs have to face the same direction?

 

[untar]

I guess there'll always be a half wrap on a Velocity deck like my OBS since the legs have to face the same direction?

Yep. Unless you have some extra dimensional technology allowing the leg to go in the opposite direction but still somehow go into the post.

Maybe get that new M.C. Escher atomizer for that

 

[Punk In Drublic]

Unless I am completely missing something here that still doesn’t equate. According to Steam, a 3mm ID, 7.5 wraps of 26awg SS317 comes out to 0.596 ohms per coil or 0.298 ohms for dual coils in parallel. There is usually a small variance between actual readings and what Steam calculated but I have never seen anything as great as a 0.4 ohm per coil. Even taking into account the long leads on the build still does not make up for the difference. Something else must be at play here.

 

[Punk In Drublic]

Wire Wizard for a single coil.

 

[zoiDman]

Hi guys.

Something I don't understand. I use SS 317L wire in 24, 26 and 28 gauge. Whenever I build coils, the resistance is always different from the resistance that the Steam coil calculator tells me it should be for a given number of full wraps.

For instance, I just built dual coils with 26 gauge SS 317L, 3mm internal diameter. I was aiming for under .3 ohms and the calculator says 7 full wraps for a 0.27 ohm build. So I did 7 wraps per coil and it's come out as 0.45 ohms.

On the calculator, 12 wraps would give 0.45 ohms.
Interestingly, if I change to Kanthal on the calculator, it says 6/7 wraps.

I've had this wire for years and it's SS 317L I ordered from a reputable British place called the Crazy Wire Company.
So I'm assuming it is actually stainless steel I have. So why is the calculator so wildly different with the wraps? I get the same reading on two different mods.

When you make a Coil from a piece of Wire and then Compare it to what Steam Engine say should happen, there is a Lot or Parameters to consider. And Each Parameter has some degree of Tolerance.

Consider your Wire of a second.

Is it Exactly .405mm in Diameter?
And what Exactly is the Wire Alloy?

People Talk about something like "317L" like it is Exact Alloy. And that All 317L is the same. It Isn't. And they are Not.

AISI 317L is a Recognized Standard for a specific type of Alloy. Which has a specific Elemental make up. But there are Tolerances as to how much of Each Element can/should be present.

Check out what is in AISI 317L ...

MatWeb - The Online Materials Information Resource

Notice mainly the range of Chromium, Iron and Nickel that can present and still be considered AISI 317L.

So what Alloy do you have in your hand? And How Closely does it Conform to say AISI 317L?

MatWeb - The Online Materials Information Resource

There is no Alloy Police who go around Testing Alloys to see if they Conform to a Uniform Standard. And a Seller can call just about Anything 317L. Either Knowingly or Unknowingly.

The Long and the Short of it is there can be Meaningful Variations in an Alloy's make-up that can effect it's Electrical Properties. And that is Assuming that what you have in your hand even conforms to a Unified Standard of what a 317L is supposed to be.

So Steam Engine is more of a Reference as to what you will Get if you do what is inputted into the Steam Engine page.

BTW - How Accurate is your Ohm Measurement to the True Value?

 

[zoiDman]

When you make a Coil from a piece of Wire and then Compare it to what Steam Engine say should happen, there is a Lot or Parameters to consider. And Each Parameter has some degree of Tolerance.

Consider your Wire of a second.

Is it Exactly .405mm in Diameter?
And what Exactly is the Wire Alloy?

People Talk about something like "317L" like it is Exact Alloy. And that All 317L is the same. It Isn't. And they are Not.

AISI 317L is a Recognized Standard for a specific type of Alloy. Which has a specific Elemental make up. But there are Tolerances as to how much of Each Element can/should be present.

Check out what is in AISI 317L ...

MatWeb - The Online Materials Information Resource

Notice mainly the range of Chromium, Iron and Nickel that can present and still be considered AISI 317L.

So what Alloy do you have in your hand? And How Closely does it Conform to say AISI 317L?

MatWeb - The Online Materials Information Resource

There is no Alloy Police who go around Testing Alloys to see if they Conform to a Uniform Standard. And a Seller can call just about Anything 317L. Either Knowingly or Unknowingly.

The Long and the Short of it is there can be Meaningful Variations in an Alloy's make-up that can effect it's Electrical Properties. And that is Assuming that what you have in your hand even conforms to a Unified Standard of what a 317L is supposed to be.

So Steam Engine is more of a Reference as to what you will Get if you do what is inputted into the Steam Engine page.

BTW - How Accurate is your Ohm Measurement to the True Value?

BTW - If you are Really into this. Or just have some Free Time on a Rainy Day with nothing to do.

You could build a Couple of Different Wrapped/Sized Coils and then write down what Ohms they are using whatever you use to Measure Ohms. Then Unwrap the Coils and measure How Long they are.

Then do some Math to Calculate what the Average Ohms per mm is for those Coils.

Then instead of using the Present Value of 317L Haywire that Steam Engine Provides, you could use the Custom setting at the bottom of the Drop-Down List.

I did that one time for some unknown 430 SS wire someone gave me. As I recall, it came out pretty Damn Close to what Steam Engine says I should get.

 

[Skunk!]

I think you're onto something Scott. Clearly I'm doing my wraps inaccurately. Here are two photos, one of each coil after I removed the wicks

View attachment 774829 View attachment 774831
It seems I have 8 wraps, I don't know if they're counted as full or half? I went for 7 per coil though. I've tested each coil separately and one is showing 0.88 ohms and the other 0.85 ohms. I guess they need to be precisely the same?

Try putting the legs into the holes they naturally would go straight into, with left on top right on bottom. You will have to do a lot less adjustment to get them into position and glowing nicely.