Bumps between old gear teeth?

Quoted message said:

A question for machinists and for chain and sprocket experts . . .

Are the bumps between these old teeth just irrelevant material left
over from machining small inch-pitch gears? The long-lost secret to
longer skip-chain life? Impacted half-inch pitch wisdom teeth?

Big bumps, 9-tooth, 1900 through 1914:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1900%27s+wood+rims+with+hub+3%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1901+Wyoma+hub+2%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1902+Eadie+1%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1903+Morrow+hub+1%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1906+Durkop+hub+3%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1909%5FEclipse1%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1914%5FEclipse%5F1%2Ejpg
(nice tool)

Big bumps, 10-tooth:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1906%5FCinch2%2Ejpg

Faint bumps, 8-tooth:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1890%27s+straight+pull+hubs+1%2Ejpg

Faint bumps, 9-tooth:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1901+EZ+hub+2%2Ejpg

No bumps, 9-tooth, 1904 through 1910:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1904+Eadie+hub+1%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1908+Corbin+Duplex+hub+2%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1910%27s+Thor+straightpull+rear+hu%2Ejpg

No bumps, 10-tooth:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1913+Corbin+Duplex+hub+1%2Ejpg

No bumps, 7-tooth:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280153069111

The bumps _seem_ to be absent from much larger front sprockets:

http://i2.ebayimg.com/04/i/000/b6/3f/7abd_1.JPG

http://i9.tinypic.com/4taqys4.jpg

http://www.nostalgic.net/pictures/1649.htm

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=160157336995#ebayphotohosting

http://www.nostalgic.net/pictures/1474.htm

http://www.nostalgic.net/pictures/871.htm

Cheers,

Carl Fogel

Aha! Bumps between teeth on inch-pitch _front_ sprocket:

http://www.nostalgic.net/pictures/894.htm

It's a 1920's Rollfast.

CF

Quoted message said:

A question for machinists and for chain and sprocket experts . . .

Are the bumps between these old teeth just irrelevant material left
over from machining small inch-pitch gears? The long-lost secret to
longer skip-chain life? Impacted half-inch pitch wisdom teeth?

Big bumps, 9-tooth, 1900 through 1914:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1900%27s+wood+rims+with+hub+3%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1901+Wyoma+hub+2%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1902+Eadie+1%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1903+Morrow+hub+1%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1906+Durkop+hub+3%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1909%5FEclipse1%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1914%5FEclipse%5F1%2Ejpg
(nice tool)

Big bumps, 10-tooth:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1906%5FCinch2%2Ejpg

Faint bumps, 8-tooth:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1890%27s+straight+pull+hubs+1%2Ejpg

Faint bumps, 9-tooth:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1901+EZ+hub+2%2Ejpg

No bumps, 9-tooth, 1904 through 1910:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1904+Eadie+hub+1%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1908+Corbin+Duplex+hub+2%2Ejpg

http://www.nostalgic.net/index.asp?S=arc/pre1920/1910%27s+Thor+straightpull+rear+hu%2Ejpg

No bumps, 10-tooth:

http://www.nostalgic.net/index.asp?S=arc/pre1920/1913+Corbin+Duplex+hub+1%2Ejpg

No bumps, 7-tooth:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280153069111

The bumps _seem_ to be absent from much larger front sprockets:

http://i2.ebayimg.com/04/i/000/b6/3f/7abd_1.JPG

http://i9.tinypic.com/4taqys4.jpg

http://www.nostalgic.net/pictures/1649.htm

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=160157336995#ebayphotohosting

http://www.nostalgic.net/pictures/1474.htm

http://www.nostalgic.net/pictures/871.htm

Cheers,

Carl Fogel

And more inch-pitch front sprockets, most without bumps between the
teeth, but some with:

http://www.bikecult.com/works/chainwheel.html

Two with bumps between the teeth are the Triplets in the upper right.

***

Here's a horrifying sight:

http://www.bikecult.com/works/chainring/DSC00027.JPG

"Overman inch pitch (USA) exhibiting severe acute elongation of the
block chain."

This other Overman isn't much better:

http://www.bikecult.com/works/chainring/overmancrank.jpg

Nor is this 1910 Rudge:

http://www.bikecult.com/works/chainring/rudge1910th.jpg

***

The only double inch-pitch that I've seen so far:

http://www.bikecult.com/works/chainring/spauldingIP.jpg

"Spaulding tandem with offset crank arms and inch-pitch 24-tooth outer
ring and 17-tooth inner ring (USA)."

Cheers,

Carl Fogel

Carl Fogel said:

And more inch-pitch front sprockets, most without bumps between the
teeth, but some with:

http://www.bikecult.com/works/chainwheel.html

Quoted message said:

Two with bumps between the teeth are the Triplets in the upper right.

Quoted message said:

Here's a horrifying sight:

http://www.bikecult.com/works/chainring/DSC00027.JPG

Quoted message said:

"Overman inch pitch (USA) exhibiting severe acute elongation of the
block chain."

Quoted message said:

This other Overman isn't much better:

http://www.bikecult.com/works/chainring/overmancrank.jpg

Quoted message said:

Nor is this 1910 Rudge:

Quoted message said:

http://www.bikecult.com/works/chainring/rudge1910th.jpg

Quoted message said:

The only double inch-pitch that I've seen so far:

http://www.bikecult.com/works/chainring/spauldingIP.jpg

Quoted message said:

"Spaulding tandem with offset crank arms and inch-pitch 24-tooth outer
ring and 17-tooth inner ring (USA)."

I suspect the bumps between teeth were originally put there to favor a
brand of block chain that had a necked down blocks. Subsequent roller
chains could all run on sprockets with these bumps. My first bicycles
all had inch pitch (roller) chains and I wondered why, not knowing
that the pair of closely spaced rollers had replaced the solid block
that was still used religiously on track bicycles.

When asked, track riders claimed they were so strong that they would
break a roller chain in a sprint or standing start Kilo. These same
guys also had no idea why track tires were glued on with shellac. It
was this sort of information that raised my curiosity about mechanical
matters, there being so much contradiction about them.

Jobst Brandt

"Ille sinistrorsum hic dexrorsum abit, unus utrique error, sed variis
illudit partibus." - Horace

Quoted message said:

Are the bumps between these old teeth just irrelevant material left
over from machining small inch-pitch gears? The long-lost secret to
longer skip-chain life? Impacted half-inch pitch wisdom teeth?

<photo links snipped>

I reckon that absent those raised sections between teeth on the
referenced skip-tooth sprockets,some chains might be pulled in a
straighter line between the roots of adjacent teeth, creating pitch
inconsistencies. That straight line distance would be shorter than the
nominal pitch of the chain. The raised bits support the chain in the
middle of each link, keeping the chain arced between teeth in a way
that the effective and nominal pitch of both chain and sprocket match.
-------------------------------
John Dacey
Business Cycles, Miami, Florida
Since 1983
Our catalog of track equipment: online since 1996
Phone: 305-273-4440
http://www.businesscycles.com
-------------------------------