Sprocket Size vs. Performance

[paulkish]

LO206 rules do not allow jet changing. Do not take me for a lazy guy!

Wow, a new idea to chew. If the air turns bad all will experience a reduction in hp. What's involved with changes in setup, tires, gearing and driving to deal with it when hp at the track is reduced. Less hp, less on track forces to work your chassis. I read on here very often about how you need more bite to go faster and sometimes to fix problems. But if all is good and hp is reduced, what do you need to do so you loose less out on the track then others?

I don't remember hearing about the LO296 mandatory jet rule before. I think it's a bad rule and another reason to keep them out of dirt racing. But what do you do to compensate for such a rule demanding your hp get reduced if the air goes bad?

 

[Kart43]

It is a variable venturi carb, with a needle that compensates by varying the size of the fuel pick up. The needle height can be changed to adjust the fuel pick up. So essentially you have a very adjustable carb. No reason to keep this engine package out of any type of racing.

 

[ABR #69]

It runs as good as most any blue printed animals and clones, there is no reason it can't run on dirt. It does so very well.

And the 206 has been on a fixed jet rule.

 

[manyfunnies]

Some people are book smart, some are track smart... I got an idea who wins more races

It takes people challenging things and figuring out why things are the way they are to advance technology. Your insult towards "book smart" people is really sad and if anything you are insulting yourself. One thing I have learned in life is if you can answer why then the problem is so much easier and you can apply what you learned to many other things. Too bad you are missing out on that.

 

[alvin l nunley]

Some people are book smart, some are track smart... I got an idea who wins more races

I'll tell you who wins the most races, that person who is both book smart and track smart.

 

[S&MRacing]

I feel sorry for the OP. It was a simple question that didn't need theroys

 

[PrimeTime]

It takes people challenging things and figuring out why things are the way they are to advance technology. Your insult towards "book smart" people is really sad and if anything you are insulting yourself. One thing I have learned in life is if you can answer why then the problem is so much easier and you can apply what you learned to many other things. Too bad you are missing out on that.

No insult intended... (As Donald Trump would say, I love book smart people, I hire 100's of them...)

My point was I'll take the advice of Carl Spackler that has spent countless hours at a race track hanging on the safety fence with a stop watch in his hand
vs the book smart engineer that says a ratio is a ratio when selecting what driver I'm going to run.

4.67 Ratio - Would you run a 15/70 or a 12/56?

 

[CarlsonMotorsports]

4.67 Ratio - Would you run a 15/70 or a 12/56?

Depends on the race track configuration / line. How much rpm drop are you seeing in the corners and do you ever lift?
On a momentum oval with low rpm drop, I am certain which I would choose of those two.

 

[Bob Evans]

Chain tension.

Apply 10 ft/lbs of torque to the clutch driver and replace a chain link with something that measures weight, then tell me that a 12 tooth driver will give you the same reading as a 16 tooth driver.

 

[PD Engines]

. it does not change the fact THEY ARE different.

I see a lot of numbers and calculations showing how the two, which in fact are different, are considered the same; show me numbers based on how they are different, which in fact they are, instead of how they are the same. If you present numbers and calculations on their differences, won't your numbers show they are different?

I accept your numbers on how two different gear sets are the same. But there not physically the same (This should be "they are" not etc......)

_______________________-

"But there not physically the same and ..." I have a question of the grammar pro's on here. I used 'there' instead of 'their' because I always thought only to use 'their' if what your talking about is human and own's it. Even if it was an animals something or another, it'd use 'there' because an animal is not human and just a dumb animal not any different in the real world and compares to humans the same as a rock. Animals cannot own anything, only humans can own things and that makes the word 'their' only used when referring to human ownership or a human association.

edit: sorry, the last just came to mind, if it messes with this thread i'd appreciate it if a moderator delete's it. thanks

They are, is the correct usage. You got it right the first time.

 

[alvin l nunley]

their [er]
adj
1. belonging to them: belonging to or relating to a specific group of people or things
They have sold their house and moved to Arizona.

2. △belonging to him or her: belonging to him or her (informal)
Everyone should make their own way home.



[12th century. < Old Norse þeirra "theirs"]

their, there, or they're?

Do not confuse these three words, as they have different meanings and spellings, and they function differently. Their is a pronominal adjective: Their [not They're or There] decisions have been made.There can be an adverb or a pronoun, e.g., Look over there [not their or they're] quickly.There [not They're or Their] are several unanswered questions.They're is a contraction of "they are," as in They're [not There or Their] sitting in the front row.

See they.

 

[W5R]

Al, the engine these guys are talking about running is a spec engine, with spec carb and the jets cannot be changed, that is why he is telling you its the same for everyone, meaning nobody can change it anyways so if he is off on jetting because of air density and at a disadvantage, so is the rest of the field he is racing against. Nobody can change the jets in this engine, it is not allowed.

 

[Kart43]

Chain tension.

Apply 10 ft/lbs of torque to the clutch driver and replace a chain link with something that measures weight, then tell me that a 12 tooth driver will give you the same reading as a 16 tooth driver.

That is correct you will measure a difference, at that point, but the point where the measurement has to be taken is after the second gear or sprocket. The combination of the two is the ratio.

 

[Bob Evans]

Since the axle is stationary for this test, the rear sprocket size is immaterial for this test, since it's immobile.
However, if the ratio is the same, it stands to reason that if the primary gear is larger, the secondary gear will be larger also, and vice versa.

I'm only pointing out that the tension between links is less with larger combinations, also, each pin rotates fewer degrees around the larger diameter sprockets.
While a chain drive system is efficient, it is by no means lossless. And, if there are friction differences between the gear combinations, then they are not the same.

In the case of drag racing down a straight and slamming on the brakes to slow down for the corner, then doing it all over again, I'll grant that it won't make as much difference as it will if you're driving the track wide open and trying to keep your steering input to a minimum and trying to mentally will another 4 or 5 rpm out of the motor.
If there are friction differences, and I believe there are, then (by definition) there are differences.

 

[ny31racing]

I'm only pointing out that the tension between links is less with larger combinations, also, each pin rotates fewer degrees around the larger diameter sprockets.
While a chain drive system is efficient, it is by no means lossless. And, if there are friction differences between the gear combinations, then they are not the same.

When you consider both sprockets, there is not less tension in the chain. Sure the weight test on the front sprocket shows less tension for a small sprocket but as soon as you connect it to a smaller rear sprocket, the system requires "more tension" to move the kart. To move a 425# kart 10 feet takes "x" amount of work no matter how you move it.

If the chain links rotate fewer degrees with larger sprockets, yes there is less friction PER LINK, but unfortunately you now have to add more links to the system, which then adds back in more friction.

You can't cheat physics. There is no such thing as a free lunch. The only thing that I see applying here is conservation of momentum. A heavier system takes more work to accelerate it and more work to decelerate it.

Put me solidly in the camp of a ratio is a ratio...

 

[Bob Evans]

So there you go.
What if you didn't have to change chain length, same number of links?

No one is trying to cheat physics, when it is physics.

 

[ny31racing]

So there you go.
What if you didn't have to change chain length?

You have to change the chain length. If you don't change the chain length and only push the motor back, then you changed the control system. Put on bigger sprockets, push the motor back so the chain is the same length. Oh wait now we can put the smaller sprockets back on and shorten the chain. Less links less friction.

Physics doesn't lie......

 

[Bob Evans]

..
I just posted what I thought it was. In momentum oval racing, there is a difference. Guess it's a horse and water thing.

 

[Elmer Patterson]

True JETS are fixed per the rules But a change in float height or a diffrent carb can be close to a jet change . Present both in tech .

 

[alvin l nunley]

I have personal experience with jets, even though the same size, they can flow differently. In a previous job, we had 200 Jets made on a precision CNC lathe for a rocket engine we were building. In testing we found about 14 different flow rates. A majority of them were the same, or very close to the same, but there were variations.