jackshaft gearing

IMHO, none, once I put a drive pulley on an engine I think that it's a good idea to not take it off and on, but you can buy a Haegar driver that has changeable belt drive pulley sleeves, that I might consider.
 
the only difference is that of friction and rotational weight which is probably too small to measure. a ratio is a ratio.
 
Changing the driver on the engine makes for a smaller ratio difference than changing the driver on the Jack shaft.
P. 20/40 = 2.0-1
S.15/60 = 4.0-1
Total = 8.0-1

P.21/40 = 1.90-1
S.15/60 =4.0-1
Total = 7.60-1

P. 20/40 = 2.0-1
S. 16/60 = 3.75-1
Total = 7.50-1
All
I have an Excel 2010 spreadsheet with 3 pages of different ways to calculate gear ratios. With and without a Jack shaft

comments compliments criticisms and suggestions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
I find that using the std. 57-21 x 30 mm. w. on my Sudams with a 2.71 primary ratio, lets me use maybe 3 different clutch drivers for the tracks we race on, but I use a 57 -19 on my Yammis , and it gives a 3.0:1 primary ratio, that way I use the 57 J/S pulley on everything and only 1 belt size fits everything, Also makes figuring final ratios a little easier.
 
Ok thanks I guess i will just change the clutch driver only reason I asked where we running theres a guy witha 100cc with a 17 on motor and he been running up front and thats running against 250s 450s 125s 116s open animals and clones so I was wonder if that driver was helping get off the corner and would the clutch driver do the samething
 
This primary j/s ratio topic can get very technical, but to keep it very short IMHO- keep ur primary j/s ratio to 2.38:1 or as close as possible. Forget making the math easy. They have j/s calculators for that. Just keep ur primary j/s ratio to 2.38:1 or as close as possible. Run a Pfiefer steel driver or other custom STEEL driver. And Azusa has a wide variety of 3/4" j/s secondary gears in #35 and #219 - and don't rule out running a j/s with a axle clutch bc it's a good thing - JMHO
 
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I think what 2fast4u is asking is about what is called the "torque multiplication factor" (think that is what it's called?).

For simplicities sake well say there is no jackshaft

setup #1 = 10 tooth clutch driver and 60 tooth axle sprocket = 6.0
setup #2 = 13 tooth clutch driver and 78 tooth axle sprocket = 6.0

which is "better"?
 
Yeti Racing said:
This primary j/s ratio topic can get very technical, but to keep it very short IMHO- keep ur primary j/s ratio to 2.38:1 or as close as possible. Forget making the math easy. They have j/s calculators for that. Just keep ur primary j/s ratio to 2.38:1 or as close as possible.
Click to expand...
do you have a reason for being so adamant about that 2.38 primary ratio? Is there an advantage to the 2.38 versus say a, 2.50?


Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
Wow, maybe he's trying to say that if we used something like that we might have been able to win 3 consecutive FAS Championships and Daytona main for opens by larger margins? I been doing this for long enough to know that there are few absolutes, just things that work for you.
 
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What im asking is there any advantage y he is running a primary of 17-57 and secondary 21-52 on the jackshaft vs a 21-57 and secondary of 17-52 its the same final ratio but is the first one putting more torque out where the small driver is on the motor
 
The smaller driver enables the engine to work easier and spin faster which will help with bottom end, but that's probably not why he's winning I'd say it's more tires and setup.
 
I dnt think its tires he using old hard hg4 tires that are almost 10 years old and the run a small 1/8 flat track
 
Our small tracks like 1/10 or 1/8, we ALWAYS run better with the smaller motors. We've got stock 100cc to radically ported 250cc.
 
2fast4u said:
What im asking is there any advantage y he is running a primary of 17-57 and secondary 21-52 on the jackshaft vs a 21-57 and secondary of 17-52 its the same final ratio but is the first one putting more torque out where the small driver is on the motor
Click to expand...
Because of the lower ratio, the first primary is spinning the clutch slower, and the lower ratio would mean there’s quite a bit more torque multiplication. Between the two ratios you would have to make substantial changes in the clutch to maintain the same stall speed. Overall, from the engine to the axle, there is no change in ratio.
I have no experience when it comes to Jack shaft clutches versus engine clutches. If a clutch is holding an engine at peak torque, while slipping, I can’t see how there would be any difference in power to the axle. One exception being; if either clutch is generating more or less heat, depending on the ratio, (and I have no proof of that) then the most power would be going to the axle with the clutch generating the least amount of heat. Other than that, I can’t see how there could be any difference.

Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
What all does that little 100cc engine have done to it? If its a full maxed out ported engine with all the right mods a kt can produce 28-30hp and a parilla reed full max can make 34-36hp. With a great setup and decent tires and real good driver it will be able to hold its own on a small 1/8 track. The bigger engines shine on the 1/4 miles where they can stretch thier legs and put all that torque and hp to the ground.
 
Its a stock 100 cc reedjet on gas hr 191 carb and s4 pipe and track is 1/8 mile was just figure that driver was helping him off the corners bc thats where he pulls the hardest he gets me ff corner I catch him as we enter the next corner but he pulls riggt back off
 
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