4 replies to this topic

[havlicek]

I got asked to wind up a pair of 65/30 arms for the nifty Hawk motor, and I mostly prefer to use wider crown lams for these.  Well, I had to use two different lams, since I ran out of one type.  For the first, I did a conventional 6-layer coil.  For the second type, there's a little less room, so I had to go with a 7 layer coil, and I "reverse wound" the arm to avoid having that last turn go back to the com across the tops of the poles.  Here's the weird thing...the 6 layer conventional wind and the 7 layer reverse wind have almost exactly the same resistance numbers.  Logic and experience tell me this shouldn't be the case, but it is what it is!?  

The arm on the left is reverse wound, and the arm on the right is conventionally wound.  The coms haven't been cut on either, and they are almost precisely the same resistance.  Cutting the coms will change both of them a bit, so they still won't  be different-er.

[swodem]

hmmm these are nice arms

PM me how much

[Samiam]

Steve,

I believe these are already called for.

 

John,

Can you explain what a reverse wind is.

[havlicek]

Hi Steve and thanks.  I guess it's not cool (?) to say what my arms cost on the forums?  Anyway, all my arms cost the same unless there's something special going on...multiple winds (doubles and triples), extra grinding etc are a bit more.  I've been told the 65/30 Hawk arms run well, so that's pretty neat.

[havlicek]

Steve,

I believe these are already called for.

 

John,

Can you explain what a reverse wind is.

 

 

Hi Sam,

 

     A "normal" wind will have an even number of layers in the coils, and you start winding near the inside (where the com and shaft are).  That way, the last layer will end with the last turn near the com, where it can simply run up to the com tab.  When there are an odd number of layers, the last turn winds up away from the com towards the outside of the arm, making it necessary to run the wire across the top of the coil to get back to the com.  

    I've come up with a way to start winding at the outside of the arm, working towards the com/shaft when I'll need an odd number of layers in a coil to get the wind I want.  That way, the last layer still winds up nearest the com/shaft.  Over time, I refined it a little to make the finished coil neater, but it makes for a neat/tight coil that's also physically stable.  Less of an issue with the coil collapsing at the last layer.

***The surprise here is that the two winds are reading the same on my meter, even though one has a 6 layer coil and the other is a 7 layer coil and on blanks pressed from two significantly different laminations.