timestep

In the name of god

Hi Every one. when i need to rotate a group of facet by rotation engine i set rotation angle to desired one and O.dt=1 and run just one step
to follow this all the time the default engine called 'globaltimestepper' change the dt and hence cases problems.
I delete this engine and now i can easily rotate the group of facets by one step to desired rotation angle. this is the code:

###
from yade import ymport
fctIds= O.bodies.append(ymport.gmsh('conveyor3.mesh',scale=0.001,color=(1,0,0), mask=5))
O.engines=O.engines[0:3]+O.engines[4:5]
O.engines+=[RotationEngine(angularVelocity=-.16+radians(ba),ids=fctIds,rotateAroundZero=True, rotationAxis=(1,0,0),zeroPoint=(.5,1.5,.5))]
O.dt=1

O.run(2)

###
(from this MWE i have a question. if i run the simulation just one step nothing happens. why?!)

when i add some sphere to my simulation and then engines, everything goes wrong and there is no rotation as expected. and there is no rotation. this is the code;

##
from numpy.linalg import norm
import numpy as np

#mat=O.materials.append(ViscElMat(density=Density,frictionAngle=frictionAngle,tc=tc,en=en,et=es))
id_Mat=O.materials.append(FrictMat(young=1e6,poisson=0.2,density=7800,frictionAngle=1))
walls=O.materials[id_Mat]

## Import wall's geometry
from yade import ymport
fctIds= O.bodies.append(ymport.gmsh('conveyor3.mesh',scale=0.001,color=(1,0,0), mask=5,material=walls))
O.engines=O.engines[0:3]+O.engines[4:5]
O.engines+=[RotationEngine(angularVelocity=-.16+radians(50),ids=fctIds,rotateAroundZero=True, rotationAxis=(1,0,0),zeroPoint=(.5,1.5,.5))]
O.dt=1
O.run(2)

sp=pack.SpherePack()
sp.makeCloud((-0.2,-0.88,0.65),(0.2,1.0,1.55),rMean=0.075, rRelFuzz=0.3,num=100)
particles=O.bodies.append([sphere(c,r,mask=3,material=walls) for c,r in sp])

### Timestep
O.dt=.0002

O.engines=[
 ForceResetter(),
 InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb()]),
 InteractionLoop(
  [Ig2_Sphere_Sphere_ScGeom(), Ig2_Facet_Sphere_ScGeom()],
  [Ip2_FrictMat_FrictMat_FrictPhys()],
  [Law2_ScGeom_FrictPhys_CundallStrack()]
 ),
 NewtonIntegrator(damping=0.2,gravity=[0,0,-10], mask=2),
 DomainLimiter(lo=(-0.6,-1.0,-10.00),hi=(0.6,3.0,3.0),iterPeriod=200)
]

##
Any Help?