A motor cycle frame is a just a piece of metal which hold all the parts of
Often steel tubes are used they are made hollow to reduce their weight while providing class performance.Cast aluminum ,and carbon fibres are used to reduce their weight.
The stiffness of a frame is reinforced by diagonal members .Stiffness of a frame depends on Proper triangulation.
Triangulation means all the members of the frame must form common node point.If proper triangulation is not formed any load one the frame will cause a bending load one the adjacent frame.
If properly triangulated ,there will be either tensile are compressive loads acting at the node . (metals have better tensile strength than bending strength)
Before going to the types a simple topic is called as Stressed member.
A stressed member is frame or component which directly recieves force and transmit that force to other members of a frame.
Types of frames
– Backbone frame – This is one of the simplest frame ,used in older vehicles,they mostly used engine as a stressed member.The rigidity of the bike is not the best as there is not reinforcment for the neck (which may result in bending ).Below image showing frame of CD 100 series honda bikes.The engine is supported by a sub frame.
The pipe with larger diameter is called the back bone.From which ,there are many sub frames.
– Diamond tube:A diamond tube is just similar to a Backbone frame ,except that a Dwon tube extends from the neck to support the engine.This type also uses engine as a stressed member.They are light is weight and simple in construction to other frames.
Used in :
Bajaj: Pulsar 135LS
Hero: CBZ Xtreme, Hunk, Achiever & Karizma R/ZMR
Honda: CB Twister, CB Shine, CBF Stunner, CB Unicorn, CB Unicorn Dazzler, CBR150R, CBR250R
Royal Enfield: Bullet 350, Bullet Electra, Classic 350/500, Thunderbird 350/500
Suzuki: Slingshot, GS150R
TVS: Flame, Jive, Max 4R, Sport, Star City
Yamaha: YBR125, SS125, SZ, FZ, Fazer
These frames can also be of cradling type, ie the down tube from neck will join the the frame below the engine (either of single down tube or double down tube)
– Cradling type:These type are extension of a diamond tube except that the down tube from the neck extends to the frame below the engine.Here engine is not a stressed member .These frames are build to last long and are more stiffer than previous types.
Here the above image is Single cradling type as only one Dwon tube is used,it can also be a Double down tube.
Single down tube
Double down tube
List of bikes with cradling type:
Bajaj: Platina 100, Discover 100/125/150, Pulsar 150/180/220, Avenger 220
Hero: CD Dawn/Deluxe, Splendor, Splendor NXG, Passion, Super Splendor, Glamour
TVS: Apache RTR 160/180
Yamaha: Crux, YBR110
– Trellis frame: This frame is formed by welding series of tubes together forming a cage like structure.They dont have a back bone or diamond or a cradle.The engine is well secured between the cage.Its commonly used in sports bikes.Construction is complex.Handling is sharper with sportier appearance
These frames are used in KTM Duke 200 and 390 models.
– Perimeter frame: Perimeter frames also known as Twin spar/beam frames.The main frame usually connects the rear swing arm frame,while the engine is suspended from the frame.The engine can be said to be held around the “perimeter” of the frame.(something like a helmet fro the engine) .Manufaturing such frames is costly and used in sports bikes.Used for sharp and stable handling and brakings.
Used in Pulsar 200 NS and RS and R15
Red circled part is the swing arm ,for the rear wheel.
– Under bone frame (used only on scooters):This frame just consists of simple construction ,with a large tube acting as bone ,which runs as a single tube from neck and runs down the bike as twin tube.
The rear wing arm will be fixed to the supports as shown by red circle .