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John in CR
100 TW
Those 2 must have different lengths for each link in the chain, because the 73t ring sure looks a lot more than 7% larger than the 68t ring. FWIW I have a 72t industrial sprocket that I plan to machine down enough to be able to use bicycle chain. My goal is a 30mph speed while leisurely pedaling along, so I can really freak out the local lycras.
John
John
Zoot Katz
100 kW
I'd not be surprised if the bike in the historical photo was running inch-pitch chain.John in CR said:
With that many teeth you can reduce the friction by knocking out half of them.
For $190.00 USD, you can get a 73 T, 130BCD, (five bolt) chainring where they specialise in recumbent parts and bikes.
They also carry 60 and 65 tooth rings for the Schlumpf drive. (also 130 BCD)
The 62 T ring is the least expensive @ fifty-two bux.
John in CR
100 TW
Zoot,
Call me cheap, but my $190 is more than I spent on my motor+controller+tire, so I find that kind of $ on a sprocket to be a hideous ripoff. I'll stick with my $20 sprocket, put in some sweat equity to make shed most of the weight and make it bike chain ready. Thanks for reminding me to grind off every other tooth while I'm at it.
John
Call me cheap, but my $190 is more than I spent on my motor+controller+tire, so I find that kind of $ on a sprocket to be a hideous ripoff. I'll stick with my $20 sprocket, put in some sweat equity to make shed most of the weight and make it bike chain ready. Thanks for reminding me to grind off every other tooth while I'm at it.
John
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Zoot Katz
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spinningmagnets
100 TW
Here's a pic of that chainring from a cycling museum. In the foreground is a dual-chain bike with a normal chain/sprocket as a jackshaft (which would have more friction than a single stage with the giant chainring.
It "looks like" its a skip-tooth, meaning if it has 73T, there's room for 146T. I dont know if its a special chain, but it sorta looks the same as the chain in the bottom left bike.
It "looks like" its a skip-tooth, meaning if it has 73T, there's room for 146T. I dont know if its a special chain, but it sorta looks the same as the chain in the bottom left bike.
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Zoot Katz
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nutsandvolts said:Zoot Katz said:
You've found the things I have been looking for way too long, thank you!
Imagine this, the Schlumpf high speed drive has a version with just 130 BCD no chainring. Put a 73T chainring on a schlumpf high speed drive, 13T on the rear, and maybe even doc bass could pedal.
NOTE: "Metric Threads"
Your freewheel is probably 1.37/1.375" x 24 tpi.
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Zoot Katz
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I/8" chain is used mostly on single speeds or old internally geared hubs.nutsandvolts said:
That 13T freewheel will not fit you hub. Nor will the Dicta 14T freewheel that runs 3/32" chain.
The threads are different.
Most chainrings I've encountered will handle 1/8" chain.
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Zoot Katz
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My lusted after meat powered bike would be Nuvinci rear and SON front hubs with disc brakes, Schulmpf drive on a 650 B wheel size Pedersen.nutsandvolts said:Imagine this, the Schlumpf high speed drive has a version with just 130 BCD no chainring. Put a 73T chainring on a schlumpf high speed drive, 13T on the rear, and maybe even doc bass could pedal.
Elegant, clean, ultra comfortable, classic yet unusual and cutting edge.
dogman dan
1 PW
Now I feel all inadquate, with my tiny 58 tooth front chainring. 
Size envy is a horrible thing. My bike says it's fine for her though. :?
Fwiw, my ratio of 58-14 is very comfy at about 25-30 mph. It can be pedaled to 35, but by then you are cartoon pedaling.
Size envy is a horrible thing. My bike says it's fine for her though. :? Fwiw, my ratio of 58-14 is very comfy at about 25-30 mph. It can be pedaled to 35, but by then you are cartoon pedaling.
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TPA
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careful with those freewheels. There are 2 thread sizes that are common, one is the 1.37 inch iso that Zoot mentioned, and there is the smaller one that he linked to which is metric. The metric one can be converted to inch.....From Sheldon Browns glossary:
If I'm not mistaken, most of the left drive freewheels are BMX metric threaded.
If I'm not mistaken, most of the left drive freewheels are BMX metric threaded.
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nutsandvolts said:
Freewheels are usually fixed size (integral). The reason that 16t is usually the smallest is that below that you run out of room for the mechanism
The AC Racing 15t freewheel gets around this by using outboard pawl & ratchet. The smaller BMX (30mm x 1mm) thread allows down to 13t (even 12t), but this is rapidly becoming an obsolete standard....
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