Ok I'll be getting back into karting again next year and have a theory about gearing that I need people to weigh in on. For some reason I keep thinking that you'd want to run the smallest front gear you can because it's lighter (same effect as a flywheel) But then you also want the mechanical advantage and tq advantage of a bigger front gear and also the bigger rear gear you need to run with a bigger front gear. What do people think of gearing in general?
Always go as big as you can on the front. I generally stay between 64-68 on the rear and anything other than that I change the driver to get me back there. But a stopwatch don't lie!
Always go as big as you can on the front. I generally stay between 64-68 on the rear and anything other than that I change the driver to get me back there. But a stopwatch don't lie!
I prefer a larger gear on the front, seems like it would be less drag to me, larger diameter smoother curve. dunno just what i feel.... easier to make a wide turn then a sharp one...
I prefer a larger gear on the front, seems like it would be less drag to me, larger diameter smoother curve. dunno just what i feel.... easier to make a wide turn then a sharp one...
I have to deal with arena gearing so a 9T primary is all I can use and that sucks...That makes my rear at 70T ...Any bigger and I leave teeth on the track... Too much wear , friction and chain abuse that tight ...Centrifical effect with larger primary ain't always bad ...The clutch itself would offset a few teeth difference...I'm at the point where I'm considering a jack shaft arrangement...Anyway I agree with JD...I go thru 3 -9T sprockets per season...
Sneaks, you are absolutly right about the jackshaft setup.. only way to go, besides switching to 219 chain/gears IMO..
How much power do you think I would lose ? Some have tried the Honda 2 to 1 gear box which puts gearing at 15T primary and 64T rear...But they don't seem to be competitive ...Unless you can change the springs in the clutch ? , they come in too quick...2000-2500r's...Need more stall speed...
You won't lose hardly nothing.. and will gain a bunch as far as being dependable, not having to worry about the 9th driver going away, chains lasting all year, an less strain on the crankshaft.. belt drive primary will control engagement speed of the clutch with different ratios..
Clutch on jackshaft will get the weight off the PTO, belt has more "softening" effect to absorb shock loads to the crank.. not to mention you can really get low on the ratios.. the smallest bullring will not be a problem to turn the engine 9,000rpm if you are so inclined..
A standard disc clutch with a 2.7 primary ratio is 2 stroke territory as far a engagement.. about 10,600 motor/3950 clutch.. so you would need closer to a 1.2:1 ratio.. like a 21/23 or 24th 30mm primary belt setup with more weight/stiffer springs.
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Wouldn't the final ratio be just that. Does it matter how you get there? Is there really an advantage to running bigger drivers? Numerically speaking, of course.
I'm going to be running sprint type racing. I am starting to understand the issues with a small driver causing more stress on the chain. 2 stroke guys probably know more about this because they always run like 8-9 tooth and big rear gears just because they turn so many rev's. I'm still trying to wrap my head around the mechanical advantage part vs centrifugle (sp?) force of smaller gear. I guess there still no subsitute for testing but surely there must be some way to calculate the best combo based on power type of track etc.
I prefer a larger gear on the front, seems like it would be less drag to me, larger diameter smoother curve. dunno just what i feel.... easier to make a wide turn then a sharp one...
Its called leverage.... what rolls easier a large diameter tire or a small one?
I'm going to be running sprint type racing. I am starting to understand the issues with a small driver causing more stress on the chain. 2 stroke guys probably know more about this because they always run like 8-9 tooth and big rear gears just because they turn so many rev's. I'm still trying to wrap my head around the mechanical advantage part vs centrifugle (sp?) force of smaller gear. I guess there still no subsitute for testing but surely there must be some way to calculate the best combo based on power type of track etc.
Another disadvantage of an 8T - 10T sprocket is the space is only big enough for a brass bushing while the 12T- whatever have roller bearings....
Excuse me !!! I'm the best.... Besides , when did a driver ever know anything about his race car ??????
well i can only look at results and see who i think is maybe the best or should i say one of the best. no matter how you look at it the name has to come up in any conversation about sprint racing.
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well i can only look at results and see who i think is maybe the best or should i say one of the best. no matter how you look at it the name has to come up in any conversation about sprint racing.
Just messen witya...We would honor his cyberwisdom here ...
As I think about it wouldn't a bigger front sprocket be harder on the engine to turn. Yes a bigger turn is smoother but it's also a greater distance for the chain to travel. Like if you start your car in 2nd gear it needs for throttle to get it going because there is more gear to turn. Maybe a ratio is a ratio but somehow I think theres more to it.
As I think about it wouldn't a bigger front sprocket be harder on the engine to turn. Yes a bigger turn is smoother but it's also a greater distance for the chain to travel. Like if you start your car in 2nd gear it needs for throttle to get it going because there is more gear to turn. Maybe a ratio is a ratio but somehow I think theres more to it.
I agree...there has got to be more to it. I just can't wrap my feeble mind around it.
if i remember right from my courses in votech school (i had to take half year of science of technology) that a larger gear has more leverage (like putting a 2 foot piece of pipe on a ratchet) therefore over coming the size of the gear or sprocket. plus the wear is less because the chain has a easier path....
i know at our track everyone tries to run the biggest they can on the front.... i tried running a 15t but always was at least a tooth or less than that (13 or 14) because of my size and weight. i know one guy was running a 16t. who knows..... you would think a ratio is a ratio but i dunno
I understand your question. Gears with more teeth have more mass than gears with less teeth.
This problem needs to be taken back to the fundamentals of mechanics.
A setup with a 20 front/100 rear would have the same gear ratio as a 10 front/50 rear. The 10/50 would have less mass due to smaller sprockets and less chain.
Our friend Newton's 2nd law says Force= mass x acceleration. This equation shows that with a constant force (the motor's torque at a given rpm), less mass would have more acceleration.
With that said, it is not only the mass of the sprockets & chain that the motor is accelerating, but the rotational mass of the entire rear axle & front wheels, and the mass of the entire rolling chassis & driver in a strait line. This mass (~500 lbs?....250kg?) compared to the difference in mass between the two sprocket sets (~1/2 lb?... 1/4kg?) would be something like .1%. The change in acceleration would also be roughly .1%. Stated another way, you will get ~.1% more acceleration out of the smaller set of gears than the bigger set of gears.
From my point of view, I will stick with our 219 pitch 17f/72r tooth setup for the reliability, and spend the money saved by not replacing front gears & chains 3 times a season on a method that produces a larger acceleration gain. Or maybe just spend it on cold beer.
Lets not get confused....Mass is not weight...Centrifical or otherwise....2 flywheels can have the same mass but weigh much different...Just like a race car going around a large corner verses a short tight corner...One would reguire more energy to change direction from the body in motion and reduce the vehicles speed accordingly...Also Newton got a couple things wrong....I like Albert..
What that means is I wear out 3-9T sprockets with a #35 chain while JPHarris runs better with a 219 chain and a 17T primary...Boy his track is bigger than mine...
Is your gear ratio that different to ours? I am curious as to why!
I am just the crew chief.....My son races the kart on an 800 meter (~1/2 mile) long track just outside of Sydney. he hits about 90 kph (56 mph) at the end of the long staight doing about 7600 rpm.
Is your gear ratio that different to ours? I am curious as to why!
I am just the crew chief.....My son races the kart on an 800 meter (~1/2 mile) long track just outside of Sydney. he hits about 90 kph (56 mph) at the end of the long staight doing about 7600 rpm.
I reach close to 28 mph on a 1/12th mile arena circle(about 400 feet) Thats about 122 meters...At 6400rpms..With a 36" right rear tire ....Sydney's on my travel plans for 2011...I will have to look you guys up...What's the best time of year to visit Australia or are you in Sydney , New York ?
Might have to lock up all the ladies if your heading to town!!
East coast----- South of Sydney to Melbourne.. it's best to be here between october to march. North of Sydney to Brisbane..pretty well all year around.
Might have to lock up all the ladies if your heading to town!!
East coast----- South of Sydney to Melbourne.. it's best to be here between october to march. North of Sydney to Brisbane..pretty well all year around.
Drop us a line when your coming.
Hey Maurice...
Thanks for the climate update...I heard you're getting some rain and flooding now ? Making the plans for sometime in 2011 or the end of 2010...Will definately look you up ... "Have Clone , Will Travel"
Too much wear , friction and chain abuse that tight ...Centrifical effect with larger primary ain't always bad ...The clutch itself would offset a few teeth difference...I'm at the point where I'm considering a jack shaft arrangement...Anyway I agree with JD...I go thru 3 -9T sprockets per season...
But what we're really talking about is ...F(force) = w(weight) X a(acceleration) / g (gravity)... 
