SKIPTOOTH QUESTION

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Rat Rod

Rat Rod

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I've always wondered what is what that made the bicycle manufacturers switch from using a skiptooth chains to the conventional chains we use today.

Does anyone know the real reason?
 
If I had to guess, I would say regular pitch running gear was just cheaper to make. If you look at prewar skiptooth running gear, everything is thick and heavy duty. 1/2" pitch stuff is usually thinner and lighter (cheaper) I really have no idea though.
 
It's interesting...on this 42 Westfield....it's not a skiptooth chain, but it's seriously heavy duty and the teeth on the cog and chainring are very thick.

It almost looks like it's the metamorphosis from a skiptooth to a regular pitch chain.

A regular chain won't fit on the bike.
 
Hey at least it's standardized. Imagine if each bike maker followed their own standards and we'd have to find Schwinn specific chains like you have to find Schwinn specific tires?

edit: just saw the last post, maybe you will in fact need a westfield specific chain?
 
Here are some thoughts on the origin of 1” pitch chain, why it was so prevalent on American bicycles in the pre-war and early post war period and the reasons that it was eventually replaced by ½” pitch chain.

The Ordinary (late 1870’s-1890) developed out of optimizing the size of the driven wheel for a 1:1 rotational relationship with the pedal cranks.

During the same time period, the earliest bicycles designed to increase this ratio to permit the use of smaller wheels did so though the use of gears either enmeshed or connected by chain.

The earliest chains were often proprietary and differed greatly in construction and dimension. Early chains were often heavier than modern chain because the metallurgy and designs of the day required the use of more material to achieve satisfactory strength.

The earliest standardized bicycle chain was 1” pitch block chain which became the norm by the mid 1890’s.

A block chain is comprised of metal blocks with a hole drilled through each end for a pin. The blocks are linked by two side plates pivoting off the same pins. Sprockets are cut so that the teeth will align with the cavities created between the blocks and link plates. The skip in skip tooth sprockets is equal to the size of the blocks.

The next major advancement in chain was the inclusion of a friction reducing rollers located around the connecting pin. The rollers allowed the chain to roll over the sprockets during engagement rather than be drug over them. Because the standard design of sprockets for 1” pitch block chain included a gap between the teeth, the earliest roller chain was designed to fit the existing 1” pitch sprockets. This is the reason that 1” pitch chain is constructed with a long link to mesh with the sprocket tooth and a short link sized to replace the block.

It was a short design leap to redesign the chain with equal ½’ pitch links and tool new sprockets to use with the chain. Metallurgy had also improved to allow for thinner sprockets by this time and the new improved ½” pitch design basically superseded 1” pitch in most application by the early teens.....except in America. While many American adult bicycles began to use ½” pitch chain in the teens, the bicycle in America was increasingly becoming a child’s transportation device and the 1” pitch sprockets were less expensive to manufacture (note that most 1” pitch sprockets are a simple flat cut stamping whereas most older ½” sprockets have more forming to maintain lateral strength and often have cut rather than stamped teeth) and stronger (I have never seen a bent 1” pitch balloon sprocket.)

By the thirties the 1” pitch sprocket had become the American standard to the point that there was little reason to change it.

It is probably due to a small growth in the Adult bicycle market in the mid to late thirties that some manufacturers started to offer ½” inch pitch chain and sprockets on their adult models and a few high end balloon bicycles.

After WW2 many American manufacturers were almost starting from scratch to tool up for the anticipated post-war boom. Most manufacturers reentering the bicycle market had made money and upgraded their factories and equipment during the war so retooling was necessary and easier than it would have been during regular production. At this point the shift to ½” pitch chain was probably partially in answer to competition from “higher performance” imports and also due to the fact that American manufacturers found that one avenue to increasing profit was by purchasing components abroad. (We know where this practice led.)
 
Incredible response!

That's exactly the kind of info I was trying to find out.

That's really interesting how the skiptooth chain design got started. Would love to see an image of the original block chain.

What would the chain on my 42 Westfield be considered?
 
RMS37 I'm betting you dont watch too much tv huh? :roll: :lol: I wonder what you do for a living. scientist??? author??? Man even if I knew that much about something I couldn't start to write it down.
 
Here in the northern Europe we had 5/8" pitch chains after 1" pitch and before 1/2" pitch, it was also 3/8" wide. Early 1/2" pitch was also little bit wider than modern one.
 
I wonder if that Westfield chain is an early 1/2 X 3/16 like some of the BMX guys use. Those BMX chains like a KMC 415H are much beefier and larger than the normal 1/2 X 1/8 or 1/2 X 3/32 used on most bikes which don't appear much different from each other except for width. Some of the BMX chainrings and freewheel sprockets made for 3/16 will not fit a standard 1/2 chain.

edit: remembered I had one out in the garage took a pic, the 3/16 chain will fit over a skiptooth sprocket tooth, but the pitch of the teeth is wrong so you can only cover maybe 2 teeth before the spacing of the teeth gets too far off.

IMG_0932.jpg
 
Here's an interesting bit of info from Sheldon Brown's website:

Block Chain

An obsolete type of chain, formerly popular with track racers.
Block chain had solid blocks as inner links, without rollers. It had a 1" pitch with 3/16" wide blocks, the same as the "skip link" roller chain that appeared on the market about 1930 to replace it.

The remaining stock of block chain was coveted by track riders who believed it was the only chain strong enough to withstand their imagined strength. When the stock of block chains finally ran out in the late 1970's, it was replaced by 1/2" pitch 3/32" wide chain, as used with derailers, although track riders still prefer an 1/8" wide chain, believing they are stronger than other riders. MTB's with 22 tooth granny chainwheels produce several times the chain tension any track rider can muster.
Click to expand...

Original text can be found here: http://www.sheldonbrown.com/gloss_ba-n.html#blockchain

firstflightbikes.com has a pic of a block chain here: http://www.firstflightbikes.com/_border ... rcrank.JPG


-Mp
 
Wow. My head hurts. That's so much info...
 
That chainring and sprocket/cog look as thick as a skippy, I bet that chain is a 1/2 X 3/16. If it breaks at least you can get a new one for $10 instead of $50-60 for a new skippy. As a comparison here's how the 1/2 X 3/16 looks on a skippy hub

IMG_0939.jpg


IMG_0940.jpg
 
Didn't Westfield make bikes for the military during WW2? Maybe that is a military contract chain. You know the gov't would have bought something odd and not standard. :? B607
 
Again, thanks for the compliments on my post, I enjoy bicycle history and writing and this forum gives me the opportunity to engage in both. Against speculation to the contrary I watch entirely too much TV, a large percentage of which is chosen for me by my four year old daughter. Professionally I work for a Civil Engineering firm and spend those hours drafting in AutoCAD and doing renderings of proposed projects in Photoshop.

Back to the subject of chain:

The thick chain ring on the Westfield is designed to use 3/16” x 1/2” pitch chain.

The most common chain width dimensions for chain used on single speed bicycles are 3/16” for 1” pitch block and roller chain, and 1/8” for 1/2” pitch chain. One half inch pitch chain for derailleur applications is narrower at 3/32”.

3/16” x 1/2” pitch chain apparently was an available but uncommon half-way house between standard inch pitch and standard half inch pitch. I looked at a copy of a 1940 Westfield catalog that I have and most models are depicted as using inch pitch drive systems. The Catalog also includes a couple of balloon models showing half inch pitch chain rings which are listed in the specifications as using 3/16” x 1/2” chain. Interestingly the lightweight adult models in the same catalog that are equipped with 1/2” pitch chain list the chain as 1/4” x 1/2”.

I wasn’t aware the BMX market had revived the wide 1/2” pitch chain but this is nice to know as it would likely be very difficult to find if that wasn’t the case.

I’ll try to get around to scanning and posting a couple of pictures from the catalog next week

I am doing some further digging to see if I can find other companies besides Westfield offering 3/16” wide 1/2” chain during the early balloon period.

Relating to other posts on this subject, I wasn’t aware of 5/8” pitch chain. I’m curious how narrow the window of use was for that chain dimension. Another interesting chain dimension is the 10mm pitch “micro drive” chain and drive system developed by Shimano in the late 1970’s for track use. A whole system was designed around it including a crankset but it never gained wide acceptance and was dropped. Chain and other pieces from the system are highly valued today.

Lastly, if you haven’t stumbled across pictures and descriptions of the Simpson Lever Chain from 1895, Google it for another look at how to get the job done.

Phil
 

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