The last image is a Ringfield motor. The left hand brush strip makes connection to the metal of the motors body and then to the wheels on one side. This connection is either via the small screw securing the left hand strip in place or there is a small 'pip' of metal behind the left hand strips tab that again makes contact to the metal of the motor and then one sides wheel set.
Ease up the brush strips one at a time and behind them are a spring and then a carbon brush. Be careful you dont lose them! The spring presses the carbon brush onto the motors Comm. Once removed access the Commutator and clean it with a fibre pencil and IPA (or Meths if IPA not available) via on a cotton bud thereby restoring the Comms segments to a brighter copper colour. Also take a wooden cocktail stick and carefully draw the sticks point along the slots between the Comm's copper segments removing all carbon deposits. Now to the carbon brushes, if necessary replacements are available, try Peters Spares or ebay etc and also new brush springs too if needed. Once carefully refitted test by applying 9 or 12volt directly to the two brush strips and the motor and wheels should all turn.
Hi
In Brian's Post he mentions using a fibre pencil for cleaning the commutator id just say clean with ipa,meths or lighter fluid first before using a burnishing brush. If there is any heavy tarnishing after that gentle use of a burnishing brush is OK but if done wrong it will put crosshatching in the copper surface which can lead to problems later on. The bloke who taught me said if using an abrasive on a commutator always do it with it spinning and the abrasive held steady. Now that was on rather larger machines than in a model but I think it holds true. You want the smoothest contact between surfaces so arcing doesn't take place. Then as Brian said clean the gap between plates to remove any material that might conduct.
The advice offered by Gareth 73 is very good and sound. However in all the years of using a Fibre (Glass) pencil I have never encountered any scratching of the copper Comm segments. The pencils glass fibre strands are far too soft to cause scratching, they just remove all the old carbon deposits. In fact, when I was at work we were issued with 1" inch (25mm) diameter Fibre pencils to clean all motor Comms, followed up with a Chamois leather strip to buff the copper segments. Later we used IPA applied via a soft lint free cloth to remove all final traces of carbon from the motor brushes on the Comm.
Never use anything that can scratch the copper segments, such as the Brass fibre stands that some cleaning brushes are sold as Pencils or Emery cloth or anything abrasive! .
