contrast with the wheels 60 at the outer end of the leaf springs 62 in other words the leaf springs 62 and wheels 60 are designed for continuous service as the tool moves through a pipeline however the legs 64 and small wheels 66 are designed to serve as security for protection of the grip shoes in unusual situations leaf springs 62 are illustrated and described as one means of maintaining grip module 14 centered within a pipeline but the invention herein is not limited to the use of leaf springs for this purpose other systems exist well known in the industry for centering a tool such as grip module 14 within a pipeline and such previously known systems may in some applications be preferable to the use of leaf springs as seen in fig1 grip module 14 is connected at its rearward end to ball joint 18 that is positioned between the grip module and control module 12 fig3 and 6 each show a female half 68 of ball joint 18 and at the forward end thereof the female half 70 of ball joint 20 as a part of ball joint 18 is seen in fig3 and 6 a coil spring 72 is employed for the purposes of preventing relative rotation between the components making up the isolation tool train in the embodiment of gripper module 14 shown in fig3 and 5 separate opposed cylinders 56 a and 56 b are illustrated to separately.