Giving a gear in Tikz absolute position

Question

I've the following MWE of a gear :

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows,shadows,decorations.markings}

% #1 number of teeths
% #2 radius intern
% #3 radius extern
% #4 angle from start to end of the first arc
% #5 angle to decale the second arc from the first
% #6 internal key of the gear node
% #7 text to put inside the gear
\newcommand{\gear}[7]{
  node (#6) {#7}
  (0:#2)
  \foreach \i [evaluate=\i as \n using {\i-1)*360/#1}] in {1,...,#1}{
    arc (\n:\n+#4:#2) {[rounded corners=1.5pt] -- (\n+#4+#5:#3)
    arc (\n+#4+#5:\n+360/#1-#5:#3)} --  (\n+360/#1:#2)
  }
}

\begin{document}

% Define the layers to draw the diagram
\pgfdeclarelayer{background}
\pgfdeclarelayer{foreground}
\pgfsetlayers{background,main,foreground}

% Define block styles used later
\tikzstyle{engine} = [fill=red!20, text centered,drop shadow]

\begin{tikzpicture}

\draw[engine] \gear{8}{2}{2.4}{10}{2}{a}{Gear A};
%\draw[engine] (a.east)+(8,0) \gear{8}{2}{2.4}{10}{2}{b}{Gear B};
\begin{pgfonlayer}{background}
  \path (a.north west)+(-4,4) node (x) {};
  \path (a.south east)+(10,-4) node (y) {};
  \path[fill=yellow!10, rounded corners, draw=black!70, dashed] (x) rectangle (y);                       
\end{pgfonlayer}

\end{tikzpicture}
\end{document}

It produces the following output as expected.

Now, I want one more gear, say Gear B, to the right of Gear A. For which I've tried uncommenting the following line in the above example:

\draw[engine] (a.east)+(8,0) \gear{8}{2}{2.4}{10}{2}{b}{Gear B};

But unfortunately It's producing something like this:

I've tried with several other ways to get it done, but nothing worked. The gear items are superimposed over each other. Is there any way to position them absolutely ?

Here is an online version of the above example which you can edit and play with.

Answer 1

Instead of:

\draw[engine] (a.east)+(8,0) \gear{8}{2}{2.4}{10}{2}{b}{Gear B};

see if this modification of above code is acceptable to you:

\draw[engine,xshift=60mm] \gear{8}{2}{2.4}{10}{2}{b}{Gear B};

Edit: Alternative for above is use of scope (as suggested Peter Grill):

\begin{scope}[shift={($(a.east)+(5,0)$)}]
\draw[engine]  \gear{8}{2}{2.4}{10}{2}{b}{Gear B};
\end{scope}

In this case you need to add library calc for calculation of shift macro

I think that instead of \newcommand for drawing gear the small picture pic would be better choice.

Answer 2

Another solution (if you do not have pics because you are still with tikzpgf 2.10) you can change the definition of \gear to use relative coordinates (still need calc added to tikz packages):

\newcommand{\gear}[7]{
  node (#6) {#7} 
  ($(#6)+(0:#2)$)
  \foreach \i [evaluate=\i as \n using {\i-1)*360/#1}] in {1,...,#1}{
    arc (\n:\n+#4:#2) {[rounded corners=1.5pt] -- ($(#6)+ (\n+#4+#5:#3)$)
    arc (\n+#4+#5:\n+360/#1-#5:#3)} --  ($(#6)+(\n+360/#1:#2)$)
  }
}

(the code in overleaf looks funny because it assumes that ($...$) is math mode...)