Crank Leverage/Gearing

[wheelhorseman]

Last week I picked up an old tryke with the coaster brake hub mounted mid frame like most trykes and uses 2 drive chains. Primary gearing was 44/18 with a short arm crank. You nearly had to stand on it to make it move. I swapped the crank to a long arm then regeared it 36/20 but it seems still hard to pedal. I had a Miami Sun that was geared 36/22 but was direct driven to an axle mounted freewheel that pedalled nicely. What would I get by dropping the front sprocket down to something like 32 and the rear back to 18 or even 16? Will the long arm/small up front sprocket make for easy pedalling without losing the speed you would get by lowering the gearing.?

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[Bicycle808]

long crank/small front sprocket/large rear sprocket/small wheels=low gear.

short crank/large front sprocket/small rear sprocket/big wheels= high gear.

Going from a 36/20 to 32/18 wouldn't lower the gearing much at all. Going from 36/20 to 32/16 would actual make for higher gearing. Fwiw, if 36/20 is hard to pedal, you have mechanical problems beyond gear ratios. Or, you just need to ride more.

Play around here for guidance/fun w/ math:
http://sheldonbrown.com/gears/

 

[mikeeebikey]

Or just put air in the tires!

 

[wheelhorseman]

Tire prussure is fine. Unless your on flat ground you better have leg muscles like an elephant. The tryke is heavier than my Sun tryke but shouldnt be this hard to pedal. No mechanical issues at all. Has to be in the gearing. Maybe the final gearing? Gonna try 3622 gearing and see.

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[Bicycle808]

Well...the final drive, between the hub NDS axle and the axle-mounted sprocket, should be a 1:1, which would have no effect on the overall ratio. And, even with 26" wheels (I suspect yours are probably smaller), 36/20 is pretty danged low. So, I'm thinking you have a gunked hub or something's rubbing or whatever.

 

[mikeeebikey]

Yeah, something is wrong! With a 36/20ish, you should be able to ride it up a slack rope!
I wasn't being a S.A. about tire pressure, over years I learned, "pedals hard," usually was tire psi.
Can you post a picture of the drivetrain?

 

[wheelhorseman]

I see that the coaster hub has what looks like an oil plug. Is there a way to check or service that? That rear end may need a good lubing. I picked up the tryke and spun each back tire by hand. The dead wheel spins like a top. The drive side seems to have some drag and stops after about 2 revs.

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[wheelhorseman]

I see that the coaster hub has what looks like an oil plug. Is there a way to check or service that? That rear end may need a good lubing. I picked up the tryke and spun each back tire by hand. The dead wheel spins like a top. The drive side seems to have some drag and stops after about 2 revs.

Sent from my GT-P5113 using Tapatalk

Tire prussure is fine. Unless your on flat ground you better have leg muscles like an elephant. The tryke is heavier than my Sun tryke but shouldnt be this hard to pedal. No mechanical issues at all. Has to be in the gearing. Maybe the final gearing? Gonna try 3622 gearing and see.

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Sent from my GT-P5113 using Tapatalk

 

[Bob Gray]

Something is dragging. Spin each wheel. If they do not rotate freely there's at least one of your problems. Remove your chain and spin the cranks. They should spin freely too. Next spin the rear wheels using the chain to spin them with. Finally I'd check the chains themselves and the jackshaft if it has one.

 

[Bicycle808]

I'd do as Bob Gray suggests plus I'd overhaul that hub. Prolly gummed up something fierce in there.

 

[wheelhorseman]

I think that hub needs a cleaning and greasing. I put the long crank in and greased it good. I assume that hub is basically like a bike.

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