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ICT, why "1.46 inches" from chainline?

941 views 2 replies 2 participants last post by  derby 
#1 ·
I was looking at the latest Ellsworth "ICT" patent applied for in 2003 and it claims design ownership when the IC traces the middle gear set chainline with in 1.46 inches during usable travel. I think the first "ICT" patent also mentioned the IC had to trace the chainline during usable travel within this 1.46 inch dimension also.

Why is 1.46 inches so special?

Seems like a closer to chainline limitation would be more appropriate to getting closer to actual "ICT".

There is mention in the latest patent that IC's tracing in front of the bike within the 1.46 range are more ideal for less variation in torque reactivity.

Looking at other pre-existing and some newer designs over the weekend it looks like all the more classic Horst links (even the NRS), and Busby design GT LTS, DW-Link, and VPP have IC's that trace the chainline within this measurement of the middle gear set chainline. If they vary outside this dimension it is by very little and most of the travel is within the "ICT" parameter and intersects the chainline during travel.

Maybe the claim for a wide parameter range for the geometry dimension in the patent is a shrewd business method to capture the majority of 4-bar full suspension designs?

- ray
 
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#2 · (Edited)
My findings:

On the NRS in a 32/20 gear the chainline starts out something like a foot below the IC. At 60mm of travel the chainline just about passes through the IC.

On a Blur, the chainline starts out about two inches above the IC at topout (IC is in the rear). At 60mm travel the chainline passes about 2.5" below the IC (now in front).

The Hollowpoint does seem to fall within the 1.46 range.

One part of the patent you are ignoring is that the lower pivots are supposed to be substantially in line with the rear axle. That leaves all of the above bikes out.

Another part you are ignoring is the ratio between the distance of chainline from IC over the distance of rear link from IC. That has to less than .08. This would also exclude short linked designs like the DW.

In general the ICT patent seems to be aimed quite specifically at protecting the actual Ellsworth configuration. In contrast Horst Leitner's patent seems to be vague.
 
#3 ·
Steve from JH said:
My findings:

On the NRS in a 32/20 gear the chainline starts out something like a foot below the IC. At 60mm of travel the chainline just about passes through the IC.

On a Blur, the chainline starts out about two inches above the IC at topout (IC is in the rear). At 60mm travel the chainline passes about 2.5" below the IC (now in front).

The Hollowpoint does seem to fall within the 1.46 range.

One part of the patent you are ignoring is that the lower pivots are supposed to be substantially in line with the rear axle. That leaves all of the above bikes out.

Another part you are ignoring is the ratio between the distance of chainline from IC over the distance of rear link from IC. That has to less than .08. This would also exclude short linked designs like the DW.

In general the ICT patent seems to be aimed quite specifically at protecting the actual Ellsworth configuration. In contrast Horst Leitner's patent seems to be vague.
Thanks,
I didn't see the parts about: "the lower pivots are supposed to be substantially in line with the rear axle." and "ratio between the distance of chainline from IC over the distance of rear link from IC. That has to less than .08."

I've done another patent search that has found more Ellsworth ramblings, which may add those limitations to the configuration.

I imagine you've figured by now than Ellsworth "ICT" design is not really IC tracing the chainline, just somewhat close. The only actual ICT would be the parallelogram linkage also parallel with chainline using equal sized cog and ring, where IC traces with the chainline at infinity. All other configurations vary the IC from the chainline. That true ICT is the mechanical geometry equivalent (for pedaling) as a BB concentric monopivot, and any anti-squat would be derived from BB height.

The .08 ratio would limit the configurations from 100% ICT (parallelogram parallel w/ chainline) to less than ICT configurations Ellsworth and possibly Busby and perhaps Specialized and Turner have produced.

Thanks again,

- ray
 
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