Gear Calculator for Multi ratios

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damonjackson_spl

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Dec 2, 2008
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Hoebart Australia
I am trying to use the gear calculator from the other forum but I dont think it is working out for what I need it to do..

I am wanted to do a 3 way jackshaft..

Honda gx50 (11t) drives a fixed sprocket on one side (22t)

then the other side of the jackshaft a chainring (40T)

and a freewheel as well on this side for the cranks to drive..

might take a photo, anyway I want to have the motor drive the rear wheel at the good old ratio 44/16

and still have the cranks working at a good ratio as well similar to 44/16

I have seen a few guys do it already and need to find out how to calculate!!!
 

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Creative Engineering

Creative Engineering

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Sep 20, 2008
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Clearwater, FL
web.tampabay.rr.com
damonjackson_spl said:
its 3:1

just found the ebay listing
Click to expand...
OK...At a 3:1 raitio, when the engine is turning 6,500 RPM, the output shaft is turning 2,166 RPM.

You have a 2:1 reduction in the first chain arrangement of 11T and 22T. 2,166RPM at the engine output shaft /2 = 1,083RPM to the chain ring side.

If you were to then use a 44T chainring and a 16T sprocket at the rear wheel, you will be stepping up!

44T/16T=2.75 1,083RPM at the chainring X 2.75 = 2,978RPM at the wheel!

A 26" Dia. wheel will layout a straight line of 81.68" for each revolution.

There are 5,280 ft. in a mile.

Assuming you wanted to set-up your bike for a top speed of 30 MPH. You will need to travel 158,400 ft in one hour. 158,400/60=2640 ft. per minute. 2640X12=inches per minute=31,680.

31,680/81.68"for each rev of the wheel=ideal wheel RPM=387

At 30MPH a 26" rear wheel needs to spin at about 387RPM.

At the current configuration, given enough horsepower you would go (2,978/387) X 30MPH = 230MPH.

Jim
 
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damonjackson_spl

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Dec 2, 2008
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Hoebart Australia
ok I that is crazy..

I will try and work out what I need to do to reduce the crazy ratio... should it be done at the chainring to the rear wheel or at the sprocket on the jackshaft from the engine?

I am an architechtural draftsman and operate in metric os very hard this miles/feet/inches concept :(
 
Creative Engineering

Creative Engineering

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Sep 20, 2008
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Clearwater, FL
web.tampabay.rr.com
You will need to set up your ratios so the wheel spins at about 387RPM for 30MPH, 514RPM for 40MPH, 642RPM for 50MPH.

I would first try to create the largest reduction at the engine side, or first chain-set. You have an 11T at the engine. Get the largest sprocket that will fit to go on the shaft in the lower bracket.

11T to 44T will cut your Wheel RPM in half. You will have 541 RPM at the chain ring...You will then need to gear it down again to slow down the rear wheel You will need a smaller chainring than the sprocket to the rear wheel.

Jim
 
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damonjackson_spl

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Dec 2, 2008
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Hoebart Australia
ok..

I have to understand the logic here as I need to able to work it out myself to problem solve this ratio dilema..

is there a simple equation to work with?

so i can plug away different configurations to try get it around 30mp/h
 
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