I wish to attach a small electric motor to my 4-year old grandchild?s
existing pedal-push, single-seat, child?s car, which will turn the
back axle at not more than 5-7 miles per hour. What electrical and
mechanical components do I need to motorise the car via the axles or
wheels and what might be the approximate cost of the components ?
Ignore cost of fitting

You could probably use a kit for bicycles ,some here
://www.google.ca/search?hl=en&q=install+electric+motor+bicycle&btnG=Google+Search&meta=
Thet aren't cheap electric bicycles retail at around $1000

Your best bet might be to purchase a child's electric vehicle at
Wal-Mart (or equivalent), and rip out the battery, motor, etc.  That
might be cheaper than trying to buy the parts separately, and would
give you some ideas on how to do it.  If you do try it from scratch,
www.smallparts.com and wmberg.com should have all the parts you need.

My sincere thanks to both mister4u-ga (30 Aug 2005 09:16 )and
formica34-ga  (30 Aug 2005 15:06 )for their suggestions which are very
much appreciated, and also for the web links provided. As I am
non-technical, I had hoped for more detailed responses. However, I am
happy to pay $5.00 to each for taking the trouble to respond and for
helping me to move a step forward to a solution.

Euripides-21-ga

These are free comments.

Here are a few more links that may help.The last two have are groups
which may be of assistance to you
http://home.thegrid.net/~lllove/bikes.htm
http://www.bikemotor.com/
http://groups.yahoo.com/group/power-assist/
http://groups.google.ca/groups?hl=en&q=bicycle%20%2B%20lawnmower%20engine&sa=N&tab=wg