Gear selection
- Thread starter Smr#17
- Start date
intimidator7x
Member
Lol best point yet!
Pete_Muller
Moderator
Once again Al... you are missing the point:
The sprocket moves the chain a "whole number" of links (chain pitches) per turn. The chain can fit the sprocket perfectly (the *measured* pitch diameter being correct), OR... the chain can fit very poorly (a beat-to-hell, completely worn out sprocket that no longer *measures* anywhere near the correct pitch diameter). In both cases, if it's a 70 tooth sprocket, the chain will move exactly 70 "chain pitches" for one turn of the sprocket. Sprocket #2 in the system does not know or care that sprocket #1 is new.... or totally butchered. It only reacts to how many links of the chain come by.
Your "theory" is akin to you saying that if you have 2 parallel shafts, with 2 sprockets on each shaft (a 10t driving a 70t, and right next to it, an 11t driving a 77t) ----- you are trying to argue that those two parallel shafts would bind up and come to a stop within a turn because the ratios are different?
Or... if your "theory" was correct, I should be able to change the gear ratio by running a tighter or looser chain (since centrifugal force will always cause the chain to float outward away from the "theoretical" pitch diameter).
PM
The sprocket moves the chain a "whole number" of links (chain pitches) per turn. The chain can fit the sprocket perfectly (the *measured* pitch diameter being correct), OR... the chain can fit very poorly (a beat-to-hell, completely worn out sprocket that no longer *measures* anywhere near the correct pitch diameter). In both cases, if it's a 70 tooth sprocket, the chain will move exactly 70 "chain pitches" for one turn of the sprocket. Sprocket #2 in the system does not know or care that sprocket #1 is new.... or totally butchered. It only reacts to how many links of the chain come by.
Your "theory" is akin to you saying that if you have 2 parallel shafts, with 2 sprockets on each shaft (a 10t driving a 70t, and right next to it, an 11t driving a 77t) ----- you are trying to argue that those two parallel shafts would bind up and come to a stop within a turn because the ratios are different?
Or... if your "theory" was correct, I should be able to change the gear ratio by running a tighter or looser chain (since centrifugal force will always cause the chain to float outward away from the "theoretical" pitch diameter).
PM
alvin l nunley
Site Supporter
Absolutely! Me too. Just be aware that there is a difference between 10/70 and 11/77. Not much, but it's there. This whole conversation was started years ago by someone trying to find a justification for going from 15/60 to 16/64, as if that was going to have some significant impact on lap times. As if somebody, standing in the pits, with their superior observational skills, could possibly know when that change would be justified.so 6.908 to 1 vs 7.00 to 1
I'm sticking with 11/77 is 7-1 .
flattop1
Dawg 89
Original poster Sorry your simple question has went off the rails, don't let this gotta be smartest guy's in the room debate that has high jacked your post overwhelm you about gearing to race, and stop your from asking more questions or posting other threads, I assure you it's not this complicated and you do not have to know or understand any of it .
Lol best point yet!
Ohhh no : he did ask about the weight of the gear set having any effect .
Although miniscule , is yes .
Not that im not guilty .
ITS THE LAST WORD SYNDROME
Lol best point yet!
Ohhh no : he did ask about the weight of the gear set having any effect .
Although miniscule , is yes .
Not that im not guilty .
ITS THE LAST WORD SYNDROME
alvin l nunley
Site Supporter
Very true, but, wouldn't that hold true for both sprockets, percentagewise, giving us the same ratio? I don't know the answer to that. Read my sig. lol
alvin l nunley
Site Supporter
All I can show is the numbers, I can't make anybody believe me. Or the numbers!
paulkish
old fart
Your wrong Al.
There is no such mechanical engineering thing as "pitch diameter ratio", you made it up the same as you made up and added useless info to kart weight outs. ...
I downloaded and did a pdf search on the document you referenced and there is NO reference in the document to your made up "pitch diameter ratio".
I also searched on the web and out on the world wide web there is also NO reference to your made up "pitch diameter ratio".
It appears you picked something which relates to what Pete explained is not a valid reference and chose to waste your time making a spread sheet on it.
It's no different then if you placed a value of 2.8475 on an orange, placed a value of 6.4900 on a grapefruit and then created a spread sheet "orange grapefruit ratio" based on dividing an orange into a grapefruit. ...
An "orange grapefruit ratio" spreadsheet would be valid if the numerical value for the color orange and the color yellow were used. Which would lead to a book being written called "Shades of Orange and Yellow".
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Ive read the original post. The man asked a simple and straight forward question. Then he gets some replies that seem like your getting college physic's lecture. Alvin just to let you know if you race dirt on a four stroke the chain pitch is 35, unless you run open 2 cycle class. I know that air pressure will effect the roll speed of the kart along with the dia. of the right rear tire. My brother proved this at ashway a couple of year's ago when he had his daughter's RR tire at 36 inches. It gave her more top end without going outside the gear rule. Then the track put in a rule no RR tire over 34 1/4 inches.
I think I have and old TS racing catalog and in the back it has an article about 35 pitch chain vs. 219 chain and it also covers how tire size effect's the kart's roll speed both though the corner's and down the straightaway.
I guess my point is lately on here someone can ask a simple question and it will get totally derailed by people who over explain their answer. They dont know if the person in new to the sport or is just asking what if. So please some of you please keep your answer's simple and to the point.
If I've rubbed anyone the wrong way sorry.
just my honest observation
I think I have and old TS racing catalog and in the back it has an article about 35 pitch chain vs. 219 chain and it also covers how tire size effect's the kart's roll speed both though the corner's and down the straightaway.
I guess my point is lately on here someone can ask a simple question and it will get totally derailed by people who over explain their answer. They dont know if the person in new to the sport or is just asking what if. So please some of you please keep your answer's simple and to the point.
If I've rubbed anyone the wrong way sorry.
just my honest observation
Original poster here, Iām pretty mechanically inclined and have been around dirt oval racing most of my life but Iām new to karts. So I can decipher what to pay attention to and what not to. I enjoy reading everyoneās opinions on subjects that Iām interested in so carry on and donāt worry about me
paulkish
old fart
alvin l nunley
Site Supporter
This is the source of my information, sorry if it's wrong. I thought these guys were experts? lol
paulkish
old fart
It's pretty ignert for you to cut down and belittle posters on here. Your statement is totally RUDE AND ignorant Al, especially you laughing at everyone with your "lol". I think you think the rest of everyone on here is good only for a laugh and your manipulation.
Furthermore the picture you posted is > DEFINING < and putting names on measurements.
Are you totally on here to piss people off for your own fun and games?
There is NO reference to your made up ratio in the picture.
You RUDELY write with a sly cut down of everyone who posted in this thread when you wrote, "I thought these guys were experts?" It shows your true colors Alvin.
Lastly Alvin: YOUR WRONG !
And Alvin I did not call you any name. My words only referenced your actions and asked questions about your actions.
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paulkish
old fart
ya know Alvin, if you would have posted the picture with "This is the source of my information", it would in my mind been ok and promoted civil conversation.
BUTT NOOOOOO! You had to throw in your smug, sly, condescending, " sorry if it's wrong. I thought these guys were experts? lol", as usual being smug and uppity in you normal INSECURE ways on the end.
Pete_Muller
Moderator
Al,
Despite yourā¦ āI thought these guys were experts?āā¦ concession, you are still not getting how your āspreadsheetā is misleading you (and possibly others).
I hope I can put this to bed once and for all, so that a year from now this doesn't come up again and confuse other/new people on this Forum.
One point I believe you are missing is that while a drawing may be labeled āpitch diameterā, the only circle that exists is an imaginary one that defines where the centers of the rollers should sit.
The second, more important point I believe you may be missing is that the chain does NOT wrap around the sprocket in a circle. The chain follows the path of a polygon. A chain is not a string, rather: itās made up of straight sections that are .375ā long (on #35 chain). If you draw a line from the center of one chain pin to the center of the next chain pin, you should see that itās a STRAIGHT line ā it is NOT an arc on a projected āpitch diameterā. Connect all the chain pin center points, and you now have a polygon, NOT a circle.
Soā¦ if you have a 77t sprocket, it does NOT have a real pitch ācircleā. It is a polygon ā in this case: a 77 sided polygon made from 77 straight lines, each of which has the length of one chain pitch (.375ā on #35 chain). If you add up those 77 straight sections, the total will be: 77 x .375ā, which is 28.875ā, which is precisely 77 links of chain. It literally can not be anything else.
The key point here is: the circumference of your āpitch diameterā on a 77t sprocket will be DIFFERENT than the distance around a 77-sided polygon (which is how a chain actually āwrapsā around a sprocket).
Using an imaginary ācircleā to describe the path the chain takes is wrong, and using it in your spreadsheet as a basis for implying that a 10/70 could be anything OTHER than a 7:1 ratio is also wrong. The real ratio is number of teeth in the larger sprocket divided by the number of teeth in the smaller sprocket, PERIOD.
PM
Despite yourā¦ āI thought these guys were experts?āā¦ concession, you are still not getting how your āspreadsheetā is misleading you (and possibly others).
I hope I can put this to bed once and for all, so that a year from now this doesn't come up again and confuse other/new people on this Forum.
One point I believe you are missing is that while a drawing may be labeled āpitch diameterā, the only circle that exists is an imaginary one that defines where the centers of the rollers should sit.
The second, more important point I believe you may be missing is that the chain does NOT wrap around the sprocket in a circle. The chain follows the path of a polygon. A chain is not a string, rather: itās made up of straight sections that are .375ā long (on #35 chain). If you draw a line from the center of one chain pin to the center of the next chain pin, you should see that itās a STRAIGHT line ā it is NOT an arc on a projected āpitch diameterā. Connect all the chain pin center points, and you now have a polygon, NOT a circle.
Soā¦ if you have a 77t sprocket, it does NOT have a real pitch ācircleā. It is a polygon ā in this case: a 77 sided polygon made from 77 straight lines, each of which has the length of one chain pitch (.375ā on #35 chain). If you add up those 77 straight sections, the total will be: 77 x .375ā, which is 28.875ā, which is precisely 77 links of chain. It literally can not be anything else.
The key point here is: the circumference of your āpitch diameterā on a 77t sprocket will be DIFFERENT than the distance around a 77-sided polygon (which is how a chain actually āwrapsā around a sprocket).
Using an imaginary ācircleā to describe the path the chain takes is wrong, and using it in your spreadsheet as a basis for implying that a 10/70 could be anything OTHER than a 7:1 ratio is also wrong. The real ratio is number of teeth in the larger sprocket divided by the number of teeth in the smaller sprocket, PERIOD.
PM