Is there a difference?

[Dylan Van Tienen]

Go and ride a ten speed bike, or more speed for that matter, and try using the different front drive sprockets while you are pedalling. Surely you'll see and feel the difference and if there is a difference on a bicycle why not on a go kart too? I'm sure the guys riding the Tour de France don't go out on course with just a five speed bike with a single drive sprocket. You bet your last buck they have 30 gears with 3 different drive sprockets to suit the terrain they are on. We have been testing this on the track for 2 years now and with definite differences in the lap times. I suppose the only sure way to end the argument would be to dyno the kart at the wheels.
_________________
The Silver Bullet

[Brent Harper]

The reason you feel a difference on a 10-speed bike is because you are pedaling "different" ratios, not the same. A motor does'nt know anything about the gear it is spinning. No matter how you get the same ratio it is the same ratio. When dealing with simple things like this(NUMBERS) you can only achieve so much speed with so much gear.

Answer is....
NO!

[Dylan Van Tienen]

And the results of our testing? Should we ignore that too?
_________________
The Silver Bullet

[Rick Blood]

Scott, you drag up a topic from 5 years ago and may not have read the whole thread.
Different ratios deliver different amounts of power to the rear wheels.
The same ratio with different gears delivers the same power + or - miniscule, unmeasureable power.
_________________
Rick Blood
www.flowdata.net

[Andrew Kidd]

11:88 means that for every 1/11th of a rotation, there is 1/88th of rotation in the rear gear. Multiply by 11, and for every rotation of the front gear, there is 1/8th of a rotation of the rear gear.

10:80 means that for every 1/10th of a rotation, there is 1/80th of a rotation in the rear gear. Multiply by 10, and for every rotation of the front gear, there is 1/8th of a rotation of the rear gear.

The ratio is the same, no matter whether you used a 5/40, a 10/80, or an 11/88. The only differences would be in chain bind from the smaller 10-tooth gear, chain flap from the smaller gear, and greater driveline losses from the chain being forced to engage 16 more teeth for every revolution of the rear axle, resulting in more chain speed and greater chain heat, and thus less chain life. These differences, however, are nearly immeasurable unless the testing was 100% controlled. (And no, nobody's track testing is 100% controlled.)

Scott, on a mountain bike, switching up in the front is like going from a 10-80 to an 11-80. The same effect can be reached by dropping approximately 7 teeth in the rear while staying with the 10-tooth front gear. We are talking about switching both gears to obtain the same ratio with both sets.
_________________
Cameron Karting - 707.938.9986 - www.cameronkarting.com
My opinions are not shared by any of the businesses I may represent.

[Dylan Van Tienen]

Too much for me to get my head around. I'll take my 4 tenths we gained by using the right front driver and go back to the couch for another movie. I otta know better than to try and understand the threads you guys write.
_________________
The Silver Bullet

[Rick Blood]

It's just math. 1+1=2. What are they teaching in school these days.
What you are talking about is changing the ratio. 1 gear only.
_________________
Rick Blood
www.flowdata.net

[Ken Olson]

Really?


Simple answer: Leverage and inertia.

Long answer:

It has nothing to do with the RPM's of the engine and how many times the wheels turn -- It has everything to do with how QUICKLY you get there. The smaller the driver, the less energy it takes to get it up to speed and therefore it gets up to speed quicker.

Maybe I can try to simplify this a little:

Think of a rock on the end of string. Wave the string in a circle like a lasso above your head -- if you have a rock at the end of a 12" string it shouldn't take much to get it going...the flick of your wrist...so it gets to your arm's max speed quickly.

Now think of the same rock on the end of a string that is 5 feet long. It requires a lot more energy and time to get it swinging at your arm's max speed. On the flip side, it takes a hell of a lot more energy to slow that string back to a stop than it does the 12" string. That's why that larger driver is faster down at the end of the straight -- it took longer to get it rolling, but once it's rolling it wants to keep rolling much more than that little 12" string did.

Note - your arm's max speed isn't turning in either scenario any faster or slower - your arm's max speed is your arm's max speed....it's the same in either case. But, pending on which string you have certainly changed how much energy and how fast it took you to get to that max speed.

Same with the motor -- max R's don't change with a smaller driver up top, just how fast the engine can accelerate that mass changes.

Smaller driver = more torque and more speed off the corner, because it gets up to speed quicker

Larger driver = less torque but once it's rolling, it wants to keep rolling and pulls harder on the top end.

Best I can explain it....maybe someone else wants to give it a shot...at the end of the day, it has to do with inertia and leverage...

[Kevin Willmorth]

This is the silliest topic in the sport, and goes on and on and on - so I just can't resist dumping fuel on it.

The size of the driver would oofer an advantage IF it were the ONLY factor involved in the entire formula. Unfortunately, the ratio of the driver would be a disadvantage as a lever, since the tire diameter remains the same. The smaller driver diameter should act like a shorter lever arm at the force end, against the radius arm of the rear tires. But none of this matters, since the reality is, the gear ratio IS THE LEVER ARM the motor uses against the tire's OD, regardless of the size of the two sprockets in the system. This is a simple principle.

The small driver/sprocket concept in karting (since it is the only sport still yacking about all this) is realized only in the form of a lighter power-train (less mass in the chain, sprocket and driver) and nothing more. Lighter mass, means less energy required to move the drivertrain, thus more energy can be applied to moving the kart forward. This is most apparant in the lowest horsepower classes, like the Briggs 5hp stuff, where the mythology of the small driver advantage is strongest. Makes sense, the drivertrain on those karts is heavy with the 35 chain, and its big sprocket diameters, etc.. Seems to me if the small driver were indeed the demon tweak everyone believes it to be, that the Briggs dirt folks would be running 219 chains exclusively, which would allow them to reduce the driver diameter without changing ratios at all. Considering the 219 chain can hold a 33hp ICA motor at full direct drive blat - I would think it would hold for an 8hp alchy Briggs rig putting around a dirt oval (another topic of heated debate - that the monster Briggs is too powerful for the 219... I run a Biland 29hp 4 stroke through a 219 - it is plenty strong for the Birggs bregade ) But... the 35 chain lives on, with its big clunky driver, big heavy chain, and big old sprocket and all!

Bottom line - cutting weight out of any rotating part on the kart, be it tires, wheels, hubs, axle, sprocket, driver, chain, carriers, disc brake, etc.... the better. If you have mag hubs, with Titanium bolts, wrapped around a 50mm axle, running cast mag wheels, also with titanium fasteners, etc... the percent of rotating mass in the drivetrain becomes greater. If you can reach the same ratio with a smaller driver, and want every incremental, microscopic gain in performance you can get - then go for it, and accept the small reduction in chain and driver life. However, if you are still running aluminum hubs with steel bolts, and cast aluminum rims, etc.... the drivetrain is a smaller percentage of total rotating mass, so trimming drivetrain weight alone is not going to produce any realizable gain worth noting.


That said, lets sit back and see if we can put this topic in the record books as the largest number of pages with an unresolved subject!

[Jerry Clayton]

I wanted to see if some of these things made a differance--since we had run FA pretty decent years ago and then pretty good with the shifters,and having a background in top-fuel racing and aviation--I decided to do some a-b-a testing

So---I installed a 90t gear on the rear axle of the shifter(we used to run around that area on the FA), lengthed the chain to fit, cranked up the engine and lowered it to the ground --the tire liked about 3 inches of sitting on the ground-- so obviously that wouldn't do

Jerry

PS for those still having difficulty, the rear tire size was the same--7.10x 5.00

JC

[Kenny Francis]

wow, 4 1/2 years and 6 pages on basic algebra.

If you really want to boil it down to basics, all that matters is how many revolutions does the crank make for a given distance the kart travels down the track.

[Pete Muller]

5 years ago I said this:

The truth of the matter is... it doesn't matter: a ratio is a ratio.

One could argue that smaller sprockets have less mass (along with correpondingly less chain required). Of course the flip side of is that the chain load is higher and the chain has to "wrap" tighter (potentially causing more friction).

The truth is...

In the range that is possible [for a given ratio] on a kart:
large enough sprockets that the engine sprocket has enough teeth to carry the load, and small enough sprockets that the axle sprocket does not drag on the ground...

It's meaningless.

A ratio is a ratio. Period.



And it still holds true... and will continue to hold true as long as there are mechanically driven vehicles.

PM

[al nunley]

Can I try.

You are accelerating a 300lb plus kart, what difference do you think there could be between one sprocket and another pretty close to the same size. And another thing, the power it takes to accelerate something would increase, the faster you accelerate it. In a kart drive train, that acceleration is so slow, I doubt anything, or anyone, could measure the extra HP needed, if any at all.

Gear size making a difference, (same ratio) is a myth, just like pop-off.
_________________
If the data does not support the theory, get a new theory. (Al Nunley)
All else being equal; Compression is the Holy Grail.
45 years, in and around karting

[Andrew Kidd]

You guys are giving Pete a coronary. There is no difference between two different front drivers GIVEN EQUAL RATIOS. It takes more power to bend the chain around a smaller gear in the front, but at the same time it takes more power to rotate larger gears and a longer chain if the front gear is longer.

No matter which way you cut it, 1.47 is 1.47. The gearbox output shaft spins once, and the rear axle spins 1.47 times, and that's it.
_________________
Cameron Karting - 707.938.9986 - www.cameronkarting.com
My opinions are not shared by any of the businesses I may represent.

[Pete Muller]

This has been hashed to death.

It's a 5+ year old topic!

Locked.....