| | | Motorized Bicycle General Discussion Topics on bicycle engine kits, help articles, repair and modifications for your motorized bicycles | rear sprocket size? Discussion at Motorized Bicycle Engine Kit Forum in the Motorized Bicycle General Discussion forum. im building a trike, it is a 3 speed to the rear stock. the cross shaft that has the 3 ... |
View Poll Results: sprocket size makes difference in speed or torque? | |
smaller sprocket = higher speed
|   | 3 | 75.00% | |
bigger sprocket = lower speed
|   | 0 | 0% | |
smaller sprocket = more torque
|   | 0 | 0% | |
bigger sprocket = less torque
|   | 1 | 25.00% |  | | 
07-09-2009, 08:49 PM
|  | Motorized Bicycle Newbie | | Join Date: Jul 2009 Location: florida
Posts: 1
| | rear sprocket size? im building a trike, it is a 3 speed to the rear stock. the cross shaft that has the 3 speed sprocket will only let me clear a 6 inch max sprocket which will be mounted to directly to the shaft and not the bike spokes... does anyone have any ideas as to what will happen with such a small sprocket mounted to the back, will i be traveling faster but slow to get there or slower but a **** of a lot of torque?  | 
07-09-2009, 09:01 PM
|  | Motorized Bicycle Elite Member | | Join Date: Mar 2009 Location: upstate NY
Posts: 1,440
| | Re: rear sprocket size? you have your poll wrong. you have the torque backwards.
the correct answer is this:
smaller sprocket= less torque/slower acceleration/faster top speed
larger sprocket= more torque/faster acceleration/slower top speed
6" is around the size of a 36t sprocket i think
you will be traveling faster but slow when starting out , with less torque.
Last edited by Cabinfever1977 : 07-09-2009 at 09:08 PM.
| 
07-09-2009, 09:55 PM
| | Motorized Bicycle Elite Member | | Join Date: May 2009 Location: usa
Posts: 332
| | Re: rear sprocket size? a pic to show your issue would be very helpful.. the bigger the sprocket, the more torque you will have, but a reduced top speed.. smaller will be opposite.. | 
07-09-2009, 10:02 PM
|  | Motorized Bicycle Elite Member | | Join Date: Mar 2009 Location: upstate NY
Posts: 1,440
| | Re: rear sprocket size? also it would help if we knew what engine you are using.
if the engine is atleast 1.6hp+ and you can fit a 36t sprocket on there,you should be fine. you might not go up steep hills or take off fast but once you get going, you should be able to fly down the road at some good speeds. | 
07-09-2009, 10:40 PM
| | Motorized Bicycle Elite Member | | Join Date: May 2009 Location: usa
Posts: 332
| | Re: rear sprocket size? Quote:
Originally Posted by Cabinfever1977 also it would help if we knew what engine you are using.
if the engine is atleast 1.6hp+ and you can fit a 36t sprocket on there,you should be fine. you might not go up steep hills or take off fast but once you get going, you should be able to fly down the road at some good speeds. | got to remember, he has double the rolling force.. 2 rear wheels, full axle and a bit heavier than a bike | 
07-09-2009, 11:09 PM
| | Motorized Bicycle Newbie | | Join Date: Jun 2009 Location: oregon
Posts: 11
| | Re: rear sprocket size? question
I have a 3 hp 4stroke engine with a 10 tooth drive sprocket driving a 52 tooth wheel sprocket is that about right???
thanks | 
07-10-2009, 12:38 AM
|  | MANIC Mechanic | | Join Date: Sep 2008 Location: Clearwater, FL
Posts: 1,099
| | Re: rear sprocket size? Good grief!!!
Jim | 
07-10-2009, 08:06 AM
| | Motorized Bicycle Elite Member | | Join Date: May 2009 Location: usa
Posts: 332
| | Re: rear sprocket size? just reread my post... geared tall unless it's got 30" tires.... on a China, it would be a hill climber with a top speed of about 20, but a 3hp 4 stroke has enough torque for the hills, and really 40 tooth would be more than sufficent | 
07-10-2009, 08:59 AM
|  | Godfather of Motorized Bicycles | | Join Date: Jan 2008 Location: Ashtabula county, Ohio
Posts: 6,851
| | Re: rear sprocket size? Quote:
Originally Posted by Creative Engineering Good grief!!!
Jim | FO'SHO'!!!
__________________ If it ain't broke, and you mess with it long enough, it will be. | 
07-10-2009, 09:00 AM
|  | Godfather of Motorized Bicycles | | Join Date: Jan 2008 Location: Ashtabula county, Ohio
Posts: 6,851
| | Re: rear sprocket size? Quote:
Originally Posted by matt167 just reread my post... geared tall unless it's got 30" tires.... on a China, it would be a hill climber with a top speed of about 20, but a 3hp 4 stroke has enough torque for the hills, and really 40 tooth would be more than sufficent | Don't forget the china engine has an internal reduction.
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