diff --git a/src/fvOptions/sources/derived/rotorDiskSource/rotorDiskSource.C b/src/fvOptions/sources/derived/rotorDiskSource/rotorDiskSource.C
index 851cc93315..106d52aaf4 100644
--- a/src/fvOptions/sources/derived/rotorDiskSource/rotorDiskSource.C
+++ b/src/fvOptions/sources/derived/rotorDiskSource/rotorDiskSource.C
@@ -381,7 +381,7 @@ void Foam::fv::rotorDiskSource::createCoordinateSystem()
         }
     }
 
-    coordSys_ = cylindricalCS("rotorCoordSys", origin, axis, refDir, false);
+    coordSys_ = cylindricalCS("rotorCS", origin, axis, refDir);
 
     const scalar sumArea = gSum(area_);
     const scalar diameter = Foam::sqrt(4.0*sumArea/mathematical::pi);
@@ -483,7 +483,7 @@ Foam::fv::rotorDiskSource::rotorDiskSource
     R_(cells_.size(), I),
     invR_(cells_.size(), I),
     area_(cells_.size(), 0.0),
-    coordSys_(false),
+    coordSys_(),
     cylindrical_(),
     rMax_(0.0),
     trim_(trimModel::New(*this, coeffs_)),
diff --git a/src/fvOptions/sources/derived/rotorDiskSource/rotorDiskSource.H b/src/fvOptions/sources/derived/rotorDiskSource/rotorDiskSource.H
index 611a26b775..f63916bf22 100644
--- a/src/fvOptions/sources/derived/rotorDiskSource/rotorDiskSource.H
+++ b/src/fvOptions/sources/derived/rotorDiskSource/rotorDiskSource.H
@@ -196,7 +196,7 @@ protected:
         //- Area [m2]
         List<scalar> area_;
 
-        //- Rotor local cylindrical coordinate system (r, theta, z)
+        //- Rotor local cylindrical coordinate system (r-theta-z)
         cylindricalCS coordSys_;
 
         //- Rotor transformation coordinate system
@@ -279,7 +279,7 @@ public:
             // (Cylindrical r, theta, z)
             inline const List<point>& x() const;
 
-            //- Return the rotor coordinate system (r, theta, z)
+            //- Return the rotor coordinate system (r-theta-z)
             inline const cylindricalCS& coordSys() const;
 
 
diff --git a/src/lagrangian/intermediate/submodels/CloudFunctionObjects/ParticleCollector/ParticleCollector.C b/src/lagrangian/intermediate/submodels/CloudFunctionObjects/ParticleCollector/ParticleCollector.C
index 988eca02c4..42613d5e8b 100644
--- a/src/lagrangian/intermediate/submodels/CloudFunctionObjects/ParticleCollector/ParticleCollector.C
+++ b/src/lagrangian/intermediate/submodels/CloudFunctionObjects/ParticleCollector/ParticleCollector.C
@@ -207,7 +207,7 @@ void Foam::ParticleCollector<CloudType>::initConcentricCircles()
     faces_.setSize(nFace);
     area_.setSize(nFace);
 
-    coordSys_ = cylindricalCS("coordSys", origin, normal_[0], refDir, false);
+    coordSys_ = cylindricalCS("collector", origin, normal_[0], refDir);
 
     List<label> ptIDs(identity(nPointPerRadius));
 
@@ -539,7 +539,7 @@ Foam::ParticleCollector<CloudType>::ParticleCollector
     faceTris_(),
     nSector_(0),
     radius_(),
-    coordSys_(false),
+    coordSys_(),
     normal_(),
     negateParcelsOppositeNormal_
     (
diff --git a/src/mesh/blockMesh/blockEdges/arcEdge/arcEdge.C b/src/mesh/blockMesh/blockEdges/arcEdge/arcEdge.C
index 0de1a2f906..190f3938a4 100644
--- a/src/mesh/blockMesh/blockEdges/arcEdge/arcEdge.C
+++ b/src/mesh/blockMesh/blockEdges/arcEdge/arcEdge.C
@@ -98,8 +98,8 @@ Foam::cylindricalCS Foam::blockEdges::arcEdge::calcAngle()
 
     radius_ = mag(r3);
 
-    // The corresponding local cylindrical coordinate system (degrees)
-    return cylindricalCS("arcEdgeCS", centre, arcAxis, r1, true);
+    // The corresponding local cylindrical coordinate system (radians)
+    return cylindricalCS("arc", centre, arcAxis, r1);
 }
 
 
@@ -158,13 +158,14 @@ Foam::point Foam::blockEdges::arcEdge::position(const scalar lambda) const
         return p3_;
     }
 
-    return cs_.globalPosition(vector(radius_, lambda*angle_, 0.0));
+    // The angle is degrees, the coordinate system in radians
+    return cs_.globalPosition(vector(radius_, degToRad(lambda*angle_), 0));
 }
 
 
 Foam::scalar Foam::blockEdges::arcEdge::length() const
 {
-    return degToRad(angle_*radius_);
+    return degToRad(radius_*angle_);
 }
 
 
diff --git a/src/mesh/blockMesh/blockEdges/arcEdge/arcEdge.H b/src/mesh/blockMesh/blockEdges/arcEdge/arcEdge.H
index 3b1062ea96..52a122226e 100644
--- a/src/mesh/blockMesh/blockEdges/arcEdge/arcEdge.H
+++ b/src/mesh/blockMesh/blockEdges/arcEdge/arcEdge.H
@@ -64,7 +64,7 @@ class arcEdge
         //- The arc radius
         scalar radius_;
 
-        //- The local cylindrical coordinate system (degrees)
+        //- The local cylindrical coordinate system
         cylindricalCS cs_;
 
 
diff --git a/src/meshTools/coordinate/systems/cylindricalCS.C b/src/meshTools/coordinate/systems/cylindricalCS.C
index fda455545a..dac22e62d3 100644
--- a/src/meshTools/coordinate/systems/cylindricalCS.C
+++ b/src/meshTools/coordinate/systems/cylindricalCS.C
@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2018 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -24,41 +24,69 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "cylindricalCS.H"
-
-#include "one.H"
-#include "mathematicalConstants.H"
 #include "addToRunTimeSelectionTable.H"
 
+// * * * * * * * * * * * * * * * Local Functions * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+
+// Issue warning if 'degrees' keyword was specified and true.
+// Compatibility change after 1806.
+
+static inline void warnCompatDegrees(const Foam::dictionary& dict)
+{
+    if (Pstream::parRun() ? Pstream::master() : true)
+    {
+        std::cerr
+            << "--> FOAM IOWarning :" << nl
+            << "    Found [v1806] 'degrees' keyword in dictionary \""
+            << dict.name().c_str() << "\"    Ignored, now radians only." << nl
+            << std::endl;
+    }
+}
+
+
+//- Convert from Cartesian (to Cylindrical)
+static inline vector fromCartesian(const vector& v)
+{
+    return vector(hypot(v.x(), v.y()), atan2(v.y(), v.x()), v.z());
+}
+
+
+//- Convert to Cartesian (from Cylindrical)
+static inline vector toCartesian(const vector& v)
+{
+    return vector(v.x()*cos(v.y()), v.x()*sin(v.y()), v.z());
+}
+
+} // End namespace Foam
+
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
-Foam::cylindricalCS::cylindricalCS(const bool inDegrees)
+Foam::cylindricalCS::cylindricalCS()
 :
-    coordinateSystem(),
-    inDegrees_(inDegrees)
+    coordinateSystem()
 {}
 
 
 Foam::cylindricalCS::cylindricalCS
 (
-    const coordinateSystem& cs,
-    const bool inDegrees
+    const coordinateSystem& cs
 )
 :
-    coordinateSystem(cs),
-    inDegrees_(inDegrees)
+    coordinateSystem(cs)
 {}
 
 
 Foam::cylindricalCS::cylindricalCS
 (
     const word& name,
-    const coordinateSystem& cs,
-    const bool inDegrees
+    const coordinateSystem& cs
 )
 :
-    coordinateSystem(name, cs),
-    inDegrees_(inDegrees)
+    coordinateSystem(name, cs)
 {}
 
 
@@ -66,12 +94,10 @@ Foam::cylindricalCS::cylindricalCS
 (
     const word& name,
     const point& origin,
-    const coordinateRotation& cr,
-    const bool inDegrees
+    const coordinateRotation& cr
 )
 :
-    coordinateSystem(name, origin, cr),
-    inDegrees_(inDegrees)
+    coordinateSystem(name, origin, cr)
 {}
 
 
@@ -80,12 +106,10 @@ Foam::cylindricalCS::cylindricalCS
     const word& name,
     const point& origin,
     const vector& axis,
-    const vector& dirn,
-    const bool inDegrees
+    const vector& dirn
 )
 :
-    coordinateSystem(name, origin, axis, dirn),
-    inDegrees_(inDegrees)
+    coordinateSystem(name, origin, axis, dirn)
 {}
 
 
@@ -95,9 +119,13 @@ Foam::cylindricalCS::cylindricalCS
     const dictionary& dict
 )
 :
-    coordinateSystem(name, dict),
-    inDegrees_(dict.lookupOrDefault("degrees", true))
-{}
+    coordinateSystem(name, dict)
+{
+    if (dict.lookupOrDefault("degrees", false))
+    {
+        warnCompatDegrees(dict);
+    }
+}
 
 
 Foam::cylindricalCS::cylindricalCS
@@ -106,45 +134,26 @@ Foam::cylindricalCS::cylindricalCS
     const dictionary& dict
 )
 :
-    coordinateSystem(obr, dict),
-    inDegrees_(dict.lookupOrDefault("degrees", true))
-{}
-
-
-// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
-
-Foam::cylindricalCS::~cylindricalCS()
-{}
+    coordinateSystem(obr, dict)
+{
+    if (dict.lookupOrDefault("degrees", false))
+    {
+        warnCompatDegrees(dict);
+    }
+}
 
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-bool Foam::cylindricalCS::inDegrees() const
-{
-    return inDegrees_;
-}
-
-
-bool& Foam::cylindricalCS::inDegrees()
-{
-    return inDegrees_;
-}
-
-
 Foam::vector Foam::cylindricalCS::localToGlobal
 (
     const vector& local,
     bool translate
 ) const
 {
-    scalar theta
-    (
-        local.y()*(inDegrees_ ? constant::mathematical::pi/180.0 : 1.0)
-    );
-
     return coordinateSystem::localToGlobal
     (
-        vector(local.x()*cos(theta), local.x()*sin(theta), local.z()),
+        toCartesian(local),
         translate
     );
 }
@@ -156,19 +165,22 @@ Foam::tmp<Foam::vectorField> Foam::cylindricalCS::localToGlobal
     bool translate
 ) const
 {
-    scalarField theta
-    (
-        local.component(vector::Y)
-       *(inDegrees_ ? constant::mathematical::pi/180.0 : 1.0)
-    );
+    const label len = local.size();
 
+    auto tresult = tmp<vectorField>::New(len);
+    auto& result = tresult.ref();
 
-    vectorField lc(local.size());
-    lc.replace(vector::X, local.component(vector::X)*cos(theta));
-    lc.replace(vector::Y, local.component(vector::X)*sin(theta));
-    lc.replace(vector::Z, local.component(vector::Z));
+    for (label i=0; i<len; ++i)
+    {
+        result[i] =
+            coordinateSystem::localToGlobal
+            (
+                toCartesian(local[i]),
+                translate
+            );
+    }
 
-    return coordinateSystem::localToGlobal(lc, translate);
+    return tresult;
 }
 
 
@@ -178,21 +190,10 @@ Foam::vector Foam::cylindricalCS::globalToLocal
     bool translate
 ) const
 {
-    const vector lc
+    return fromCartesian
     (
         coordinateSystem::globalToLocal(global, translate)
     );
-
-    return vector
-    (
-        sqrt(sqr(lc.x()) + sqr(lc.y())),
-        atan2
-        (
-            lc.y(),
-            lc.x()
-        )*(inDegrees_ ? 180.0/constant::mathematical::pi : 1.0),
-        lc.z()
-    );
 }
 
 
@@ -202,31 +203,18 @@ Foam::tmp<Foam::vectorField> Foam::cylindricalCS::globalToLocal
     bool translate
 ) const
 {
-    const vectorField lc
+    const label len = global.size();
+
+    tmp<vectorField> tresult
     (
         coordinateSystem::globalToLocal(global, translate)
     );
+    auto& result = tresult.ref();
 
-    tmp<vectorField> tresult(new vectorField(lc.size()));
-    vectorField& result = tresult.ref();
-
-    result.replace
-    (
-        vector::X,
-        sqrt(sqr(lc.component(vector::X)) + sqr(lc.component(vector::Y)))
-    );
-
-    result.replace
-    (
-        vector::Y,
-        atan2
-        (
-            lc.component(vector::Y),
-            lc.component(vector::X)
-        )*(inDegrees_ ? 180.0/constant::mathematical::pi : 1.0)
-    );
-
-    result.replace(vector::Z, lc.component(vector::Z));
+    for (label i=0; i<len; ++i)
+    {
+        result[i] = fromCartesian(result[i]);
+    }
 
     return tresult;
 }
diff --git a/src/meshTools/coordinate/systems/cylindricalCS.H b/src/meshTools/coordinate/systems/cylindricalCS.H
index 4504231cae..ef34b9e15b 100644
--- a/src/meshTools/coordinate/systems/cylindricalCS.H
+++ b/src/meshTools/coordinate/systems/cylindricalCS.H
@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2014 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2018 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -25,7 +25,7 @@ Class
     Foam::cylindricalCS
 
 Description
-    Cylindrical coordinate system
+    Cylindrical coordinate system, always in radians.
 
 SourceFiles
     cylindricalCS.C
@@ -50,12 +50,6 @@ class cylindricalCS
 :
     public coordinateSystem
 {
-    // Private data members
-
-        //- Are angles in degrees? (default = true)
-        bool inDegrees_;
-
-
 protected:
 
     // Protected Member Functions
@@ -92,21 +86,19 @@ public:
     // Constructors
 
         //- Construct null
-        cylindricalCS(const bool inDegrees=true);
+        cylindricalCS();
 
         //- Construct copy
         cylindricalCS
         (
-            const coordinateSystem&,
-            const bool inDegrees=true
+            const coordinateSystem&
         );
 
         //- Construct copy with a different name
         cylindricalCS
         (
             const word& name,
-            const coordinateSystem&,
-            const bool inDegrees=true
+            const coordinateSystem&
         );
 
         //- Construct from origin and rotation
@@ -114,8 +106,7 @@ public:
         (
             const word& name,
             const point& origin,
-            const coordinateRotation&,
-            const bool inDegrees=true
+            const coordinateRotation&
         );
 
         //- Construct from origin and 2 axes
@@ -124,8 +115,7 @@ public:
             const word& name,
             const point& origin,
             const vector& axis,
-            const vector& dirn,
-            const bool inDegrees=true
+            const vector& dirn
         );
 
         //- Construct from dictionary and name
@@ -136,16 +126,7 @@ public:
 
 
     //- Destructor
-    virtual ~cylindricalCS();
-
-
-    // Member Functions
-
-        //- Are angles in degrees?
-        bool inDegrees() const;
-
-        //- Non-const access to inDegrees
-        bool& inDegrees();
+    virtual ~cylindricalCS() = default;
 };
 
 
diff --git a/src/topoChangerFvMesh/mixerFvMesh/mixerFvMesh.C b/src/topoChangerFvMesh/mixerFvMesh/mixerFvMesh.C
index d613e33906..1c8de7f563 100644
--- a/src/topoChangerFvMesh/mixerFvMesh/mixerFvMesh.C
+++ b/src/topoChangerFvMesh/mixerFvMesh/mixerFvMesh.C
@@ -269,13 +269,10 @@ Foam::mixerFvMesh::mixerFvMesh
     ),
     csPtr_
     (
-        coordinateSystem::New
-        (
-            "coordinateSystem",
-            motionDict_.subDict("coordinateSystem")
-        )
+        // Caution: must be a cylindricalCS
+        coordinateSystem::New(*this, motionDict_, "coordinateSystem")
     ),
-    rpm_(readScalar(motionDict_.lookup("rpm"))),
+    rpm_(motionDict_.get<scalar>("rpm")),
     movingPointsMaskPtr_(nullptr)
 {
     addZonesAndModifiers();
@@ -294,6 +291,7 @@ Foam::mixerFvMesh::~mixerFvMesh()
     deleteDemandDrivenData(movingPointsMaskPtr_);
 }
 
+
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 // Return moving points mask.  Moving points marked with 1
@@ -310,13 +308,15 @@ const Foam::scalarField& Foam::mixerFvMesh::movingPointsMask() const
 
 bool Foam::mixerFvMesh::update()
 {
-    // Rotational speed needs to be converted from rpm
+    // The tangential sweep (radians)
+    const vector theta(0, rpmToRads(rpm_)*time().deltaTValue(), 0);
+
     movePoints
     (
         csPtr_->globalPosition
         (
             csPtr_->localPosition(points())
-          + vector(0, rpm_*360.0*time().deltaTValue()/60.0, 0)
+          + theta
             *movingPointsMask()
         )
     );
@@ -339,7 +339,7 @@ bool Foam::mixerFvMesh::update()
         csPtr_->globalPosition
         (
             csPtr_->localPosition(oldPoints())
-          + vector(0, rpm_*360.0*time().deltaTValue()/60.0, 0)
+          + theta
             *movingPointsMask()
         )
     );