Who's Got A Quick(Not Fast) Bike?

[5-7HEAVEN]

A fast bike has a big number top speed. It is measured by a speedometer.

A quick bike accelerates at low speed, wanting to buck you off the saddle. Quickness is measured by a stopwatch.

Depending on gear ratio, a fast bike can also be quick or not.

A quick bike can also be fast or not.

Brute torque in a vehicle produces fast times for the first 60 feet in a quarter miles. On a bicycle it's probably wayy less than 60 feet.

Does anyone know of a way for all of us to measure and compare our motored bike's quickness?

 

[Member 5549]

Are we talking about the Mid range power band ???

 

[5-7HEAVEN]

Quickness

Low AND midrange power from a standing start.

 

[QuadManiac]

You want to measure acceleration (a). All you need is a speedometer and a stopwatch.

Start your stopwatch and note your current velocity (if it's not zero) or your starting velocity if you were already moving, at the same time crank hard on your throttle. Then, some short time later, stop the stopwatch and note your new or final velocity.

acceleration or a = v/t (where v is final velocity and t is time) for starting from a standstill

OR

a = (Vf - Vs)/t (where Vf is final velocity and Vs is starting velocity) when measuring acceleration between one speed and another.

a's units are commonly in feet / (second * second) (or feet per second per second or feet per second squared)

Example:

you go from 10 miles/hour to 20 miles/hour in 5 seconds

a = {[20 (miles / hour) - 10 (miles / hour)] X (5280 feet / 1 mile) X (1 hour / 3600 seconds)} / 5 seconds

= (20 - 10) X (5280/3600) / 5

= 2.93 feet / (second*second)

[ the (5280 feet / 1 mile) and (1 hour / 3600 seconds) just converts miles/hour into feet/second, a much better unit to use for the acceleration calculation ]

This measures your average acceleration over a period of time, so the shorter the time you take for your measurement, the more accurate it will be for the acceleration available near that particular velocity, but the greater the error induced by poor stopwatch handling, etc... just experiment to see what kind of time works best for you and generates repeatable answers.

This certainly gives you the ability to determine your bike's acceleration performance and compare to other's if they wish to join in.

Hope this didn't put u to sleep.

Good Luck and Good Riding

 

[misteright1_99]

My MB was very quick with a 50t sprocket, but topped out at 20. I like to cruise around at between 15 and 20 so I put the 44t back on.

 

[5-7HEAVEN]

[.

This certainly gives you the ability to determine your bike's acceleration performance and compare to other's if they wish to join in.

Hope this didn't put u to sleep.

Good Luck and Good Riding[/QUOTE]

VERY good info, which I need to absorb.

Not sleep-inducing at all, Quad.

 

[DIYMark]

Ah yes but I can cheat all this lol!

Get a huge rear sprocket. Good acceleration but low top speed and that low speed means less drag. So to compare our bikes "mathematically" we would probally need to set guide lines or "classes". Say have a "10 - 20 MPH Class" and then a "20 - 30 MPH Class" and even a 30+ MPH class?

So far my bike with a 44T could do wheel stands/mono/wheelies, with a 22T I could do 80+ Km/h (Ive raised my compression to ~8:1) and then now Ive dropped it back to a 36T which I took for a test run today - with this sprocket It allows me to climb hills (on the very steep ones some assitance is needed to keep the engine In the "sweet spot") and I reach a top speed of 65Km/h.

HOWEVER, I still want gears (the 36T is just a quick fix because I could hook it up to the bike in a flash just for kicks). One day Ill get a shifter kit and then I'll have a motor bike lol!

In the near future Ill try to meausre my acceleration and post it up!

 

[beachcruiser]

I know DIMark defined quick and fast motorized bicycle correctly. If it can do a wheel stand/ wheelie on take off, you definitely know your bike is quick.

 

[QuadManiac]

Absolutely! So if we were to start comparing acceleration rates over several different speed ranges, as Mark said, we'd have to compare apples to apples by including top speed.

I cheat also, with a SBP shifter kit. I can wheelie in 1st with just a tiny bit of pedal, yet top at about 35 mph in 7th and, due to the 'gearbox', I can reach that top speed rather quickly. This is why drag races are always done over a fixed distance. It's not how fast you're going at the end that matters, it's how long it took you got there.

So, perhaps a simpler comparison of bikes would be to use elapsed time from a standstill to 0.1 mile, and to 0.2 mile, etc. (Of course, now we have to define the flatness of the course, etc., for a fair comparison) This may be an easier way to compare apples to oranges.

However, if you want to 'tweak' your bike, acceleration is usually the best way to quantify the performance gained/lost due to any changes you've made.

 

[5-7HEAVEN]

Ah yes but I can cheat all this lol!

DIYMark, that's not cheating. That's testing and tuning, exactly what many of us here would like to see!

Classes would be interesting if you also list your bike's top speed.

Cheating is "adjusting" stopwatch times or understating what engine or modifications you have.

BTW, which engine do you have that allows you to do wheelies and travel 80km/hr(50mph)?