jackshaft gearing help

Hi Tom,

It's fun to experiment with gearing!

My bike was barely climbing short, steep ramps and short, steep hills. When I installed larger, taller tires, the bike wouldn't climb them at all. Changing a single sprocket not only fixed the problem; the bike performed even better!

Let's see what you have.

It'd be simpler and less expensive if all sprockets used the same size chain. Please keep that in mind.

You could keep the 35t rear sprocket and easily adjust your gear ratios at the jackshaft. Smaller jackshaft gear cost less than large wheel sprockets and greatly reduce or enlarge ratios with less effort.

8.68:1 would work well.

Use 11t engine sprocket chained to a 30t jackshaft sprocket.
Use 11t jackshaft sprocket connected to rear wheel 35t sprocket.

30/11 = 2.7272:1
35t/11 = 3.1818:1

2.7272 x 3.1818 = 8.68:1

At 3600rpm, top speed of 32.1mph.

Index of /ratiocalc

depending on weight and steepness of hills you may have to go to steeper gears

fett said:

ooh, nice. Thanks for the numbers and the link. Now I can move on to the next issue I'll be back

Tom

Click to expand...

What size is your crankshaft where your sprocket attaches? 5/8"? 3/4"?

I'm looking to gear down to be able to go at less than 5mph with some where a little above idle so that I have enogh torque. This is for an adaption of a motor bike I will use in like a art 2 wheeled vehicle for events.

The thing is that I have about 8.3 to 1 and need further gearing down. That is done with a pulley small to big at jackshaft to rear wheel drive pulley.

Further I have a chain clutch on the crankshaft that goes to the live jackshaft and the gear is only 1 an 1/2 to maybe 2 inches in diameter. Not counting the teeth but you get the idea.

What I saw was one as large as maybe 6 inches in diameter that fits the jackshaft 5/8 diameter, but costs like $200 and I'm thinking if you are looking for hill climber gears, small or big you have maybe contact of best prices?

I thought of using another engine that fits a belt clutch (or a shaft reducer on the engine I have) then I would just use another washing machine pulley adapted to fit the 5/8 inch jackshaft diameter. This would be about 1" and 10" diameter twice with two belts running. I'd hope to cruise at 4 mph

Measure Twice

Hey MT, McMaster Carr has a 6" 36t 41 chain 5/8" bore sprocket for 26 bux.
This is the largest 5/8 bore sprocket they offer but you can buy larger ones with unfinished bore.
A 60t is $36.50 but comes no smaller than 3/4" bore.

Since you're experimenting, try to keep costs down but in the correct ratio.

JMO, for safety purposes it's better to keep sprockets on the small side, the ones near the rider.

11t sprockets are 1.5" outside diameter(OD); 17t sprocket is 2.23" OD. 36t sprocket is 4.51" OD, 60t is 7.38" OD.

It should not be a problem to switch all sprockets to #35.

Keep engine sprocket.
Connect to jackshaft sprocket-17t ($10.61).
Install 10t jackshaft sprocket ($8.86).
Change rear wheel sprocket to 56t ($12.99).

17/11 = 1.5455:1
56/10 = 5.6:1
1.5455 x 5.6 = 8.65:1

The 11t, 17t and 60t prices are reasonable.

http://thatsdax.com/ENGINE_KIT_PARTS_PAGE_2.html


http://www.mcmaster.com/#roller-chain-sprockets/=fho592

--------------------------------------------------------------------------------






motor motorized engine bike kit 56 T 9 hole sprocket | eBay

Please speak to that vendor about the right sprockets combination.