# torque calculation...

Question asked by vvishwaskumar in #Coffee Room on Nov 19, 2009

vvishwaskumar 路 Nov 19, 2009

Rank D2 - MASTER

hi

i have a bicycle having a load of 100 kg acting on it. I have to calculate the starting torque, to propell the bicycle, either on the wheel or on to the pedal(crank) considering the rolling friction....please give some numerical explaination...please Posted in: #Coffee Room

i have a bicycle having a load of 100 kg acting on it. I have to calculate the starting torque, to propell the bicycle, either on the wheel or on to the pedal(crank) considering the rolling friction....please give some numerical explaination...please Posted in: #Coffee Room

gohm 路 Nov 19, 2009

Rank A3 - PRO

You are missing information. gear ratio? wheel diameter? length of crank arm? With your info you can only deduce the load is 50kg per wheel if two wheeled. You will take this 50kg weight at the drive wheel and multiply by the ratio of drive wheel size vrs. crank arm. Then multiply by the ratio of the front vrs. rear sprockets.

vvishwaskumar 路 Nov 20, 2009

Rank D2 - MASTER

hello gohm..gohmYou are missing information. gear ratio? wheel diameter? length of crank arm? With your info you can only deduce the load is 50kg per wheel if two wheeled. You will take this 50kg weight at the drive wheel and multiply by the ratio of drive wheel size vrs. crank arm. Then multiply by the ratio of the front vrs. rear sprockets.

gear ratio = front sprocket/rear sprocket =2

length of crank arm= 0.17 metres

wheel radius= 0.33 metres

so effort required = 50*2*(0.33\0.17) =

**194.14 kg**

torque on pedal = 194.14*0.17*9.81 =

**323.76 N-m**

**is it possible to have this much of torque..?**

also

**a 150 cc bike is normally have 14 to 16 N-m torque, can it compare with bicycle calculation..? give me detailed explaination please**

BigOhm 路 Nov 20, 2009

Rank D3 - MASTER

100 kg? Gohm, tell your little brother to quit riding on the handlebars?:roll:馃榿

vvishwaskumar,

There are a bunch of ways of looking at this, but one you might consider is just in terms of work. Think of the 100 kg bike. It's weight is 980 N and you might guess the rolling friction to be 0.05 with good tires and a good level surface. So, every meter the bike goes, you have 49 Nm of work. So work backwards and see how many radians your pedal crank has to go through to move the bike one meter. Throw in a 0.70 efficiency factor for the chain, bearings, etc etc. Then just set (Torque)(radians)(0.70) = 49 Nm.

Sorry for not using math symbols. I'm a newbie and can't find them.

vvishwaskumar,

There are a bunch of ways of looking at this, but one you might consider is just in terms of work. Think of the 100 kg bike. It's weight is 980 N and you might guess the rolling friction to be 0.05 with good tires and a good level surface. So, every meter the bike goes, you have 49 Nm of work. So work backwards and see how many radians your pedal crank has to go through to move the bike one meter. Throw in a 0.70 efficiency factor for the chain, bearings, etc etc. Then just set (Torque)(radians)(0.70) = 49 Nm.

Sorry for not using math symbols. I'm a newbie and can't find them.

Rohan_sK 路 Nov 20, 2009

Rank C2 - EXPERT

Gohm, dont you think that the Total Weight of the bike ie 100 kg must be considered while calcualting the Work done or hte Effort needed.

The bike weighs 100 kg, so each wheel takes up 50 kg. But the force required to drive will be the total Inertia force ie 100 kg plus the frictional resistance ( here 0.05).

So, Total Effort ( without the sporcket ratios, etc) = (W+f)9.81 = (100 + 0.05(100))(9.81). You can then multiply the sprocket wheels, crank arm ratios and get the Final Effort and Torque required.

Correct me if I am wrong.

The bike weighs 100 kg, so each wheel takes up 50 kg. But the force required to drive will be the total Inertia force ie 100 kg plus the frictional resistance ( here 0.05).

So, Total Effort ( without the sporcket ratios, etc) = (W+f)9.81 = (100 + 0.05(100))(9.81). You can then multiply the sprocket wheels, crank arm ratios and get the Final Effort and Torque required.

Correct me if I am wrong.

vvishwaskumar 路 Nov 21, 2009

Rank D2 - MASTER

thanks rohan, but how this much torque is possible..think andRohan_sKGohm, dont you think that the Total Weight of the bike ie 100 kg must be considered while calcualting the Work done or hte Effort needed.

The bike weighs 100 kg, so each wheel takes up 50 kg. But the force required to drive will be the total Inertia force ie 100 kg plus the frictional resistance ( here 0.05).

So, Total Effort ( without the sporcket ratios, etc) = (W+f)9.81 = (100 + 0.05(100))(9.81). You can then multiply the sprocket wheels, crank arm ratios and get the Final Effort and Torque required.

Correct me if I am wrong.

also a 150 cc bike is normally have 14 to 16 N-m torque, can it compare with bicycle calculation..? 100kg=bicycle weight(15kg) + rider weight(85kg)

vvishwaskumar 路 Nov 21, 2009

Rank D2 - MASTER

hey guys help me for calculation......please

rpower 路 Nov 22, 2009

Rank E1 - BEGINNER

give the coefficient of friction.

You want to calculate starting torque that means the torque to overcome static friction bw wheel and ground.

static friction(forcew) = u(coeff of friction) x N (weight normal reaction)

torque at wheels=forcew x radius of wheel.

divide this by 2(gear ratio)

u'll get the torque applied by rider to accelerate the bike from 0.

You want to calculate starting torque that means the torque to overcome static friction bw wheel and ground.

static friction(forcew) = u(coeff of friction) x N (weight normal reaction)

torque at wheels=forcew x radius of wheel.

divide this by 2(gear ratio)

u'll get the torque applied by rider to accelerate the bike from 0.

vvishwaskumar 路 Nov 22, 2009

Rank D2 - MASTER

馃榿

i am getting from this .torque on pedal = 8 Nm and effort applied on pedal=5 kg..and it looks feasible because 150cc bike normally have 15 Nm of torque.

also can we compare the bicycle torque with that of bike..in terms of their mechanics....? reply please

thanx rpower...rpowergive the coefficient of friction.

You want to calculate starting torque that means the torque to overcome static friction bw wheel and ground.

static friction(forcew) = u(coeff of friction) x N (weight normal reaction)

torque at wheels=forcew x radius of wheel.

divide this by 2(gear ratio)

u'll get the torque applied by rider to accelerate the bike from 0.

i am getting from this .torque on pedal = 8 Nm and effort applied on pedal=5 kg..and it looks feasible because 150cc bike normally have 15 Nm of torque.

also can we compare the bicycle torque with that of bike..in terms of their mechanics....? reply please

rpower 路 Nov 22, 2009

Rank E1 - BEGINNER

I do not understand your question compare torque of bicycle with motorbike "in terms of mechanics" !!馃槖vvishwaskumar馃榿

thanx rpower...

i am getting from this .torque on pedal = 8 Nm and effort applied on pedal=5 kg..and it looks feasible because 150cc bike normally have 15 Nm of torque.

also can we compare the bicycle torque with that of bike..in terms of their mechanics....? reply please

vvishwaskumar 路 Nov 23, 2009

Rank D2 - MASTER

a 150 cc bike is normally have 14 to 16 N-mrpowerI do not understand your question compare torque of bicycle with motorbike "in terms of mechanics" !!馃槖

**torque**, can it compare with bicycycle torque...?

also we are using a chain drive for transmitting torque from wheel to pedal...so is there no any consideration for tension on sides and moment of inertia....?

rpower 路 Nov 23, 2009

Rank E1 - BEGINNER

in a bike or car there are several inertial loses. innertial loses in transmission , then in differential (in cars), in running engine components.

e.g Torque(clutch)=torque(engine)- Ia

where I is moment of inertia of engine cmponents and a angular acceleration

e.g Torque(clutch)=torque(engine)- Ia

where I is moment of inertia of engine cmponents and a angular acceleration

vvishwaskumar 路 Nov 23, 2009

Rank D2 - MASTER

rpowerI do not understand your question compare torque of bicycle with motorbike "in terms of mechanics" !!馃槖

sorry

but in calculating torque do u not think that, as the power is transmitted by chain drive from front to rear sprocket, there is also a consideration of tension in the chain...?

rpower 路 Nov 24, 2009

Rank E1 - BEGINNER

Ofcourse, tensions on tight side (upper) and slack side (down) of the chain drive are to be taken into account.

[T(tight) - T(slack)] velocity = Power

[T(tight) - T(slack)] velocity = Power

gohm 路 Nov 24, 2009

Rank A3 - PRO

As far as the weight issue, it totally depends on if you are only condsidering torque at the drive wheel. Energy loss would be used in the calculation to equate a procise calculation however this problem does not appear to need to factor that based on the info provided by the OP. Sounds like a class theory problem.

sachin121 路 Sep 6, 2010

Rank E2 - BEGINNER

hi have vehical of four wheels having 150mm dimeter. i need to transport load of 50kg with velocity 3m/s then which motor should i select .please send me motor specification

sophia9rev 路 Sep 9, 2010

Rank E2 - BEGINNER

some great tip guys..馃榾 ....my dads a mechanical engineering but heslearning to use the forums

beyonbala 路 Jun 9, 2011

Rank E1 - BEGINNER

I don't understand how did u arrive at 15Nm ..vvishwaskumar馃榿

thanx rpower...

i am getting from this .torque on pedal = 8 Nm and effort applied on pedal=5 kg..and it looks feasible because 150cc bike normally have 15 Nm of torque.

also can we compare the bicycle torque with that of bike..in terms of their mechanics....? reply please

Also when searched for static friction co efficient between wheel and tyre, it is found to be 0.7-0.8.

what is that 0.05?

techfresh 路 Jun 14, 2011

Rank D3 - MASTER

with out specifying the force you are applying at the pedal/crank how can you calculate the torque ??? the weight is acting over the bicycle not on the pedal ,please be specific about your question

techfresh

techfresh

Dev92 路 Mar 29, 2015

Rank E2 - BEGINNER

Hey fellas, i am working on a project where in which i have brought a few changes to pulsar 150 bike, my end result is increase in rpm which we have achived, now help me out about how to calculate the torque for the same??? plz reply

wanderer2711 路 Sep 16, 2015

Rank E2 - BEGINNER

will the torque applied be reduced/increased when we use a shaft drive instead of a chain drive ?

wanderer2711 路 Sep 16, 2015

Rank E2 - BEGINNER

will the torque applied be reduced/increased when we use a shaft drive instead of a chain drive ?

Deepak Durgasrinivas 路 Sep 25, 2015

Rank E1 - BEGINNER

Generally what is cycle weight which was commonly using in India and how much force is applying on pedal

ImSj17 路 Mar 11, 2016

Rank E2 - BEGINNER

I am designing a electric bicycle... Load applied is 120 Kg so how can I calculate torque if I use 600 watt motor