Kiwegapawa,That is all I was refering to with the link,but please tell Me how would rollers "mesh"?....The 420cc was just a comment as to the size of area thats in that frame and in no way an order to abandon Your plans for motorizing Your trike and was ment fully in jest....also the worm gear set up will work if you have a freewheeling sprocket on the drive output,and also I played with slotcars then and still run 1/24 scale cars at the local slot car raceway now at 55 yrs old and the same thing would happen, power spinning the worm turns the spur gear the spur gear does not spin the worm... And Wayne,That is the most brilliant idea i think You've ever had!...and shared with the world!....Kiwegapawa i wish You all the luck in Your build....Tigmaster...