bcoltsmith1
New Member
what is the best ratio for a bike that has a sprocket on the back tire and a sprocket on the drive shaft? thanks for your help
Sprockets what is the best ratio for a 2 sprocket bike
- Thread starter bcoltsmith1
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sparky
Active Member
Depends on things like RPM and tire diameter.
I'm not 100% positive, but I think I have 10 teeth on the drive shaft and 44 teeth on my 20" wheel. I think. Very nice acceleration and top speed for me.
I'm not 100% positive, but I think I have 10 teeth on the drive shaft and 44 teeth on my 20" wheel. I think. Very nice acceleration and top speed for me.
bcoltsmith1
New Member
thanks my bike has 20" tires, and the rpm of the old partner chainsaw motor 50cc is i think 9000-10000, i heard 6:1 ratio is a good ratio to go by is this true because i want to be able to climb decent sized hills but still have a good speed
TREEWK
Member
As A General Rule Most Of These Small Engines Need Around 18:1 Ratio. If You Used The Golden Eagle Setup You Could Go Without Reduction. The China Kits Have A 4.2:1 Gearing Built Into Them. Hope This Helps. Ron
sparky
Active Member
I'm not 100% positive on the RPM, but my 33cc engine prolly gets 5500-6000 rpm. It's got a gearbox with a 5:1 ratio. Then I think the driveshaft has 10 teeth, while the wheel has a 44t sprocket on a 20" wheel... for an additional 4.4:1 reduction, making it an overall 22:1 reduction I think.
I'm 160 lbs, and I accelerate very quickly. Top speed is always 25mph, tho when it warms up... 28 becomes easy, and 30 becomes possible, tho it largely depends on the wind. If I were heavier, I'd prolly keep the gears the same but just pedal assist to accelerate.
I'm 160 lbs, and I accelerate very quickly. Top speed is always 25mph, tho when it warms up... 28 becomes easy, and 30 becomes possible, tho it largely depends on the wind. If I were heavier, I'd prolly keep the gears the same but just pedal assist to accelerate.
bcoltsmith1
New Member
what do you mean by the gearbox ratio? and to TREEWK im trying to do this build without a bike kit
srdavo
Well-Known Member
I agree with the 18:1 reduction.
srdavo
Well-Known Member
have a look over here at some 'scratch' builds..... http://www.motoredbikes.com/showthread.php?t=4770
also look around on the site, there are better examples of home-brewed bikes.
also look around on the site, there are better examples of home-brewed bikes.
sparky
Active Member
Ya gotta have a gearbox... something the clutch grips onto to spin the driveshaft sprocket. That gearbox will have its own reduction.
So if you got the gearbox I have (5:1) and then wanted 18:1 overall, you'd divide 18/5 = 3.6:1 reduction between driveshaft sprocket and wheel sprocket.... so 10t to 36t would be more appropriate.
Somewhere in the equation, you've got to account for the tire diameter... but I can't really do math problems right now.
So if you got the gearbox I have (5:1) and then wanted 18:1 overall, you'd divide 18/5 = 3.6:1 reduction between driveshaft sprocket and wheel sprocket.... so 10t to 36t would be more appropriate.
Somewhere in the equation, you've got to account for the tire diameter... but I can't really do math problems right now.
TREEWK
Member
Bcolt. Yes, I Understand That. One Thought, To Keep Cost As Low As Possible. Weld Another Rim Without A Tire To Your Rim (maybe Pop Rivet) And Use As The Driven Belt Pulley. Then Weld A Steel Pulley To The Saw Clutch Drum. Have The Center Of The Motor Pulley Enlarged For Installing And Removal. You Can Not Do This With All Saws. Many Different Clutch Setups. Most Good Saw Motors Will Run A Long Time. A Good Saw Is Worth More Than The Price Of A China Girl Kit. Been In The Tree Service For Many Yrs. Have About 30 Saws. Tell Me What You Have And Will Look At Mine. Or Post Pic Of Clutch Side Of Yours. Ron
