imported post
With thanks to Tim Wentzell and his pictures at
http://goldwingdocs.com/forum/viewtopic.php?f=11&t=259 ,
I would ask members to view these pictures as I discuss quality starter motors and compare them to the cheap knock offs as to the OEM. Even a rebuilt OEM is a better motor than the knock off.
Starter motors are robust at about ¾ HP to 1 HP. They must be because as a starter motor they are built and designed to be overloaded. To turn over a cold engine with cold oil and all that friction takes a great deal more than ½ to 1 HP.
These starter motors like most are series wound DC motors. At 12 V, a low voltage these motors are over loaded to as much as 600% and usually at 300% of their nominal rating. A ½ HP motor draws .5 x 746 W or 373 W and at 1 HP, 746 watts; in amps that is 31 and 62 amps respectively at full load. But an 1100 for example draws 100-120 amps to start that engine, if that electric motor is ½ a HP then that is 4x, and if a 1 HP about 2x the normal power.
With that much energy you can see why the starter motor cannot be used all the time and that it should rest or be off to cool. When 2x or 3x the normal power is applied to do the work things get very hot very fast. All things within the motor because of current, voltage drop and magnetism not only cause rotation but heat. Heat is a by-product of a motor.
Motors because of friction, a stopped condition a running condition create lots or torque. An electric motor produces most torque during its stop to start run process and this torque creates a lot of heat and more heat is produced when the load of the engine is placed on the starting motor.
So much heat is produced that if you do not allow the motor to cool by not using it or by using it longer than 3 seconds at a time the solder within will melt. If the solder melts while the motor is spinning centrifugal force will throw out the liquid solder from its joints weakening the joint.
Magnetism is used to create attraction or repulsion, like poles repel, unlike poles attract, N to N repels, S to S repels but N to S attract. The motor spins because of this basic law, and the field is attached in series with the armature so that the field either attracts or repels the armature to cause spinning. Why does it spin, because of bearings holding the armature in position.
All that power to the field and armature goes through the carbon brushes and the mechanical rectifier, the commutator that keeps the relationship of + and – together. Through the field and armature out to and through the body to the frame the current travels. The DC current helps in building a magnetic field, which is used to create a spinning armature. Magnetic things are ferrous or iron and steel is a part of iron and the armature is wound on an iron core as is the field. These iron or steel cores become magnetized. In the making of a motor the steel parts cannot be constantly magnetized but they must get magnetized in one direction and then magnetized in another direction. The directions are either North or South or variations of N or S. Variations become more or less N or more or less S.
To do the magnetic variation the iron or steel cores are laminated by layers of sheet steel to create the shapes either of the armature and the field coils so a dominant coil face of north and south are created. The coil core, face has strong magnetic lines of unseen force as does the core of the armature and these cores create attraction and repulsion which is used as a twisting action in a motor.
These steel or iron cores that are laminated take on magnetism very easily, but the motor action requires these same cores to get rid of their magnetism just as easily and to help do that the individual lamination sheets are insulated with a varnish. Now the iron, steel cores can be easily magnetized and demagnetized as the design of the motor permits.
A strong frame is a must to hold all this together and it can be rolled steel or best is cast iron with machined surfaces for fitting. The bearings either ball or roller never a bushing; spacers to accommodate slight differences and a contact area of metal to ground to offer great electrical continuity are great qualities of a starter motor.
Internally, various insulations are needed because without these insulation the 12 V would be shorted and the motor would not work. Insulation as good quality varnish poured onto conductors that make up the coil faces in both the armature and field. Mica a mined material placed between the copper segments of the commutator. Carbon which is a semi conductor of the right consistency to carry current, not prematurely wearing out or cause the commutator to wear out as it carries the 12 V and many amperes through the brushes to the internal parts of the motor.
Also the carriers of the brushes, springs, holders and bolts holding down parts of the motor that is not spinning but must withstand the torque and twisting of the motor; to all of this a mass of engineered parts it must be assembled correctly and tested with a print out to prove that this assembly is built to a standard that works as it should and signed by a person responsible for the result, because you demand it.
So look at the pictures and you can see that a starter motor is a work of art; are these quality starters too costly in comparison to a poor product? A good starter built well and tested has a lifespan of 15 years when used daily each and every day, 30 years when used at 6 months intervals.
A cheaper knock off can be made to look good but in the test of daily use it will fail for any reason from bad soldering, poor machining, lousy bearings to carbon brushes that crack and steel full of pits and copper that is soft. Insulation breakdown with poor dielectric strength, all in all a real piece of junk passing itself off as a good product makes for a product not to be bought.
It is very difficult to buy over the net when you are not given the truth about where the starter was made. A rebuilt unit with OEM parts and new refurbished parts is a very good trade off to buying a brand new starter. Buying a knock off leaves you high and dry when and where is unknown.
You may want to read this while viewing the technical pictures of rebuilding a starter and between the two articles get a feel for all the wondrous work that goes into a simple series wound DC motor that uses electricity, mechanical, magnetic and bearing technologies. There are so many places to cut corners when manufacturing a motor and these areas can be seen with a rebuild. Hopefully this blurb will offer an understanding without being too technical, enjoy.
