Paulc

What do you guys think of this telescoping cassette concept I came up with?


It would eliminate cross chaining, and thereby:


1. Improve efficiency

2. Allow for more gears on the cassette then is possible with a derailleur

3. And theoretically offer smoother shifting


Is this worth pursuing or just too out there?


Thanks for checking this out

Paul

HTupolev

The Gradient derailleur from the 1890s, the first derailleur system known to have been commercialized, used a sliding gear cluster. The approach continued to be sparsely used for decades, but was basically dead by the middle of the last century.

The problem is that it dramatically increases mechanical complexity.

A big part of why derailleurs are so popular is that considerations like chain angle turn out to not actually matter that much. Especially with modern laterally-flexy chains.

Darth Lefty 

There’s a patent for a sliding chain ring too

Paulc

I understand your opinion.

But when you factor in that the rear derailleur is eliminated as well as the entire front shift gear, it comes out at least wash in parts count and weight, could be better in favor on the telescoping approach

shelbyfv

Sell your idea to highest bidder! Shimano, Campy, SRAM. Retire and ride lots more

Bandera

Call when the functional prototype has 10,000 flawless miles on it and all of your patents have been approved.
Otherwise: It's a combination of Hot Air and yet another answer to a question that no one asked.

-Bandera

Gresp15C

The idea requires much wider dropout spacing.

Ogsarg

no rear derailleur? Don't quite see how that would work from the video. I see the smaller cogs fitting into the larger ones but you still need something to move the chain unless the chain is stationary and in that case, you need bits to keep the chain from moving and that would be more parts and plenty of friction.

Troul 

I like to be a xchain rebel. Sometimes little little determines if the terrain is ridden on or walked on.

HTupolev

The idea is that instead of shifting by moving the jockey wheel left and right, you shift by moving the cogs left and right.

Obviously this doesn't eliminate the rear derailleur, though. It makes it far more complex! You still need the pivoting cage to tension the chain and keep it flowing onto the cogs, and the simple parallelogram joint has been replaced by a complex sliding/telescoping mechanism within the cassette.

TiHabanero

Good idea, and as already pointed out, one that has seen prime-time and drifted into history. Working out the details will be the key to success. There are a lot of new comers to the shifting market with hydraulic der. and knock-off shifters, but changing the way the whole thing operates is an interesting idea. If used with already available shifting mechs will be a bonus, because it will simply involve a hub design and not a shifter design. If all it takes is a couple of fixed jockey wheels and a hub with gear cluster, it could be a viable alternative. With that said, develop a working prototype and concept model, put a bunch of miles on it, accurately estimate tooling costs, and manufacturing costs, then sell it to one of the big 3.

No way would I take it to market myself.

subgrade

The way I see it, the most problematic aspect with this concept is that the cogs would slide along where the actual torque transfer happens, which would make it quite tricky to make it work well and last long. It would most probably need some clutch mechanism of sorts, making it quite sophisticated and costly.

Kapusta

The complexity is going to be immense. The part about telescoping the cassette is only half of the equation. The other part is going to be adjusting the position of the upper jockey wheel as you change gears ( though this may become easier with electric shifting)

Also in the form shown, the cassette is going to take up just as much room on the hub as it does now. So I don’t see how this is going to allow more gears.

And why would this lead to smoother shifting?

Kapusta

I think what we are seeing here is all of the weight and complexity of an IGH, but without any of the benefits.

How is this an improvement over an IGH?

livedarklions

That seems a lot of engineering complexity to get rid of the very minor problem of cross chaining.

I think you would have to change the name of the non-cog part from derailleur to railleur, or maybe just rail.

Paulc

It Requires 2 more sprocket widths over the total on the cassette

Paulc

Gears can't match the efficiency of a roller chain

tyrion

That video illustration is physically impossible with current or near future engineering.

If the small cassette is small enough to slide into the big cassette, there will be a massive jump between the biggest cog on the small cassette and the smallest cog on the big cassette.

Paulc

You are mistaken. The cassette shown has a typical mountain bike sprocket stack. There is not a larger jump when the chain transitions to the other cassette half

Darth Lefty 

I had an idea a while back for a 1x front ring that would somehow yaw to stay in line with each cog... like with maybe a CV joint. I could see how to control the yaw with a swashplate controlled by a second cable from the rear shifter, but was trying to figure out how to make it automatic. That's how I found and know about the patent for the sliding front chain ring.

This was before I had much time on a 1x system. Now that I do... it's fine, really. Not something that needs to be fixed. Especially if using a steel ring, like NX. The real problem with cross chaining has to do with rubbing on the FD, and ghost front shifting due to skate in small/small gears with short chain stays, and both are better on 11 than 10 speed because they moved the rings further apart and the chain is narrower.

Paulc

The jockey would swing on a lever arm. It doesn't get much simpler than that.

It allows for more gears because there is only so much of a cross chain angle possible before the chain will chatter at the exit point of the cassette sprocket of fall off the crank sprocket. Also removing the derailleur gains about an inch of side clearance

It could have smoother shifting because without cross chaining cogs could be ground down much more to create easy transition shift points

tyrion

Typical mountain bike cassette, let's say 11-42: 11-13-15-17-19-21-24-28-32-37-42.

Suppose the big cog on the small cassette is the 21t and the small cog on the big cassette is 24t. Look at a 21 tooth cog and look at a 24 tooth cog. Can the 21t cog even fit within the outline of the 24t cog?

Paulc

Yes it can

The image attached is a 21t with internal clearance for an 18t

Paulc

tyrion

Ok. I'm not an engineer but that seems like a very tough engineering problem.