Another DIY rear derailleur cage.

[greencat]

Looks great. I'm wondering how much of a difference changing the position of the pulley wheel makes. I can understand it obviously does vertically, but horizontally? What did you notice?

 

[jordic1968]

That's really quite ingenious as a means for determining a workable design. Me like. Are you an engineer by profession?

Thanks. Electrical engineer, but engineer after all

 

[jordic1968]

https://bikerecyclery.com/frank-spi...ys-123mm-c-c-cupertino-spence-wolf-near-mint/

Right, Spencer Wofl mods (there are several ones) was a source of inspiration, like the campagnolo rally cage, the Suntour GT and the XC with 3 pulleys. Also the old Shimano MTB XT rd's. But at the end , I want to create something that looks similar to the original, and the constrain I have is not to make it too long because then it looks ugly in my opinion.... I still have room for another hole and lower the upper pulley a little bit. We'll see the end.

 

[Woz]

Would be good to know your complete set-up; what is up front? A still of each extreme gear combo I think will help zone in.

When Shimano moved to a higher sprocket count (MTB), what they actually did was to increase the length of the parallelogram side plates and slightly tweak the cage and top jockey placement - in fact prior 10T jockey wheels were used. If I recall, Suntour changed the angle of the parallelogram.

Just saying, and appreciate you don't have this luxury, but loving how you are experimenting.

The length of the cage and where the bottom jockey wheel is will need to be a suitable balance of how much chain to take up and just how strong the cage return spring is.

 

[jordic1968]

Looks great. I'm wondering how much of a difference changing the position of the pulley wheel makes. I can understand it obviously does vertically, but horizontally? What did you notice?

That is a good question. I still need to investigate and learn further but what I've observed is that both magnitudes are related, as the cage really pivots over the frame bolt. And the amount of rotation depends on the size of the cage and the size of the cogg. What in a 13 cogg you see a hole from the right in a lower positon for example, when the chain is on the 34, that hole is really up, because the rd has pivoted. At the end, the most favourable position for the upper wheel I see is as as lower as possible, back to the main bold. Like modern RD in fact. I'll give another try to my prototye with another hole even lower at the left of the main bolt but then probably I have to lower as well the bottom pulley making a larger RD that is what I don't like asthetically.....

 

[jordic1968]

Looks like it works very well indeed.

With aluminium of the same thickness as the original cage and copy the profiling, of the old cage, and your cage will look oem.

That is the goal! thanks

 

[Woz]

The top jockey I think needs to be closer to the cage pivot point (making it lower) to help with large sprocket clearance, and to the right (front of the bicycle) to help with chain wrap for the small sprocket when the entire cage swings back to take chain slack.

 

[jordic1968]

The top jockey I think needs to be closer to the cage pivot point (making it lower) to help with large sprocket clearance, and to the right (front of the bicycle) to help with chain wrap for the small sprocket when the entire cage swings back to take chain slack.

Agreed! that's my next step, thanks for the hint.

 

[fastpedaller]

BITD I bought a Campag Nuove Record rear mech and was disappointed with its performance compared to a Sun Tour Cyclone. It became clear on examination that the Sun Tour Slant Parallelogram (patented) was a better design for changing across sprockets which increased in size (as they do of course). I have to comment though that the Campag gave many. many years of trouble-free service because it was superbly made from top-quality materials and engineering which meant all pivots remained play-free. I never tried a later Campag which I presume benefit from a slant parallelogram, because I 'switched' to Shimano

 

[Dicky71]

Hack or bodge

He has explained that it's a prototype and it he's pimped it with some Drillium so it ought to tick your boxes. I judge it as a hack. It does the job without costing a sh**load of dosh.. Chapeau i'd say.