31 Oct 2012

Shimergo 10 or 11 speed on Trykit 2WD body.

Trykit's unique 2WD body (independent double ratchet freehub) is wider than any normal Shimano freehub. So there is the potential to build some very interesting, non-standard cassettes without having to worry about rear mechs hitting the spokes, rear drop-out spacing, running out of freehub width, lack of locking ring threads or chains rubbing the frame. (At all!)

Here is my 9 speed Shimano cassette with Shimano's standard 9 speed spacing. There is no reason why I can't just add another larger sprocket and standard 9 speed spacer in place of my DIY brass spacer ring. 

I'd immediately get 10 speeds at 9 speed prices. The Campag Ergo levers would still change gear flawlessly. I won't have offended the pull per click ratio of the levers. Plus, the sprocket spacing would remain correct to match the linear lateral movement of the Shimano rear changer.   
9 speed cassettes, spacers and individual sprockets are readily available at relatively low cost! The spacers come free when you scrap any 9 speed cassette through natural wear. Or just buy two different  Shim /Sram 9 speed cassettes and mix and match them to taste. You can have all 10 speeds at 9 speed Shimano sprocket spacing with 9 speed Shimano changers and 11 speed Campag Ergo levers. It will happily run on cheaper, longer lasting, 9 speed chains as well! :-)  

You'd have to keep an eye on overall (system) tooth capacity of the Shimano rear changer. Probably a medium cage would still manage it if you weren't greedy in largest sprocket choice. But, the potential is there to get a wider range of 20 gears from a compact double instead of a wide range triple. All at remarkably low cost. Or you could have 30 closer gears with your existing triple! Most Shimano 9 speed rear changers probably have enough lateral movement capacity to reach an extra sprocket by adjusting the stop screws further out. 

More to the point, one is not limited by manufacturer's conservatism in choice of sprockets. The Shimano rear changer must still cope with the largest sprocket choice as well overall tooth capacity. Chainring difference + cassette difference. eg. Compact chainwheels 50-34 = 16 teeth  difference. Cassette of 11-28 = 17 teeth difference. Add the two together 16 + 17 and you have a system capacity requirement of 33 teeth for your rear changer.

In theory, one could start from scratch. By buying a new, relatively cheap, 9 speed Shim/Sram cassette.  Say 11/12-24? Then just add a larger sprocket to act as a "crawler" or "granny" gear. 28t, 30t or 32t? Clamp it all together on the 2WD Trykit body with a Shimano sprocket spacer in between and you have a full 10 speeds at silly 9 speed prices! (including cheaper chains) Surely it must be illegal to have so much fun from throwing something together like this?
What a shame I can't fit anything larger than 26t to my Higgins! Grrr? Though I could still experiment with an ultra-close ratio 10 speed "cassette" provided I limited myself to 26T. Not quite as much fun as having lower gears on the cassette. Because I still have to keep my inner chainwheel on my triple for vertiginous emergencies. (This just means very steep hills for the hard of reading) 

Here, I have drawn red arrows to show the bottom gear clearance problem of my 58 year-old Higgins. (click to enlarge) The same clearance issue exists on the rear reinforcing loop. 

The further to the left I try to place a very large sprocket the worse the clearance  gets! Most other trikes would have much more clearance for really big sprockets. Trykit, Longstaff, etc. It is not the tooth clearance which limits how big a sprocket I can have. It is the added height of the chain as it lifts over the tips of the teeth of the largest sprocket. This occurs just before it settles down and fully engages the sprocket teeth. The chain height on top of the teeth makes quite a serious difference. 

Potential limitations on my Higgins: 

Instead of a wider ratio: 
11/12, 13, 14, 15, 17, 19, 22, 25, 28, 32

I could still have:         
11/12, 13, 14, 15, 16, 17, 19, 21, 23, 26

I might have to buy another rear Shimano changer. I won't know until I try. Mine is the older, Tiagra 9 speed, rather than the latest 10 speed. It is not the changer which decides how many gears are indexed. It is the lever. 

Older rear changers for smaller numbers of gears may not have enough lateral movement for many more gears. Nor have the quality to cope with narrower (precision) spacing required by 10 speed indexing. Nor, in some cases,  match the movement per cable pull decided by the index levers. 

If I could talk Geoff Booker @ Trykit into making a slightly wider body I/we could all have all 11 speeds Shimergo at 9 speed chain and cassette prices! (with 11 speed Ergo levers) There is not enough room at the moment for two more sprockets and 2 spacers for all 11 speeds at Shimano 9 speed spacing. That said, it may be impossible to get a rear changer to stretch over the extra distance.

Later that day:

Well, it works! I removed the axles and fitted a packing ring behind the fixed axle bearing cup on the left. By sheer luck I had a 28T 8 speed sprocket on the back of a cassette to experiment with. This went onto the Trykit body with a 9 speed spacer in between it and the 9th sprocket from the existing cassette. I didn't bother to disturb the existing cassette. The axles went back in. Half a turn out on the rear changer stop screw and I had instant 10 speeds! Faultless and positive changing onto the new "granny" gear!

A 27t largest sprocket would have been safer and require less axle offset. Any other trike axle with Trykit 2WD would probably be fine. It was dark as I tidied up so no pictures tonight.

Going by this example, anybody with Trykit 2WD should be able to run 10 gears with 11 speed Ergo levers using lower cost, all 9 speed components:

I have used a 9 speed Shimano Tiagra changer, 9 sp chain, 9 sp cassette plus an extra bottom gear sprocket and 9 speed spacer.

Logic suggests that one chooses the 9 speed cassette with care. One which will benefit from an additional granny gear with a reasonable step between tooth numbers. However, given enough spare sprockets one could build any 10 sp cassette (using 9 sp sprockets and spacers) entirely to suit one's own taste. Even an ultra-close ratio time trial 10 speed cassette of 11,12,13,14,15,16,17,18,19,20t.  All without getting involved in the greater expense of 10 speed components.

Sadly even the most exotic bike owners won't have room on a normal freehub for building such a 9 speed + 1 cassette. Similarly, the Trykit 2WD body does not have room for a 9+2 extra sprockets and spacers. With 9+1 the cassette lock ring fits perfectly to the far end of the thread on the 2WD body.

Any extra length on the 2WD body ought to be at the top gear end to ensure adequate frame clearance from the bigger sprockets. On my Higgins/Trykit 2WD there is a lot of a spare room at the top gear end of the cassette. I can't use that empty space because the axle bearing cups must still be screwed into the axle housings. It would require a different axle shoulder layout to move everything laterally over to the right. Then there is always the matter of chainline.

It is already known that the 10 speed Ergo levers will operate 10 speed Shimano changers, chains and cassettes. An original 10 speed Shimano cassette will be slightly narrower than the 10 speeds using my 9 speed +1 method: But will require 10 speed Ergo levers. The 10 speed Shimano sprocket spacing is not correct for 11 speed Ergo levers pull per click ratios. Though it is possible to modify the rear changer cable clamping. (Hubbub) Or just add a suitable Shiftmate.

Without all the data to hand I cannot say whether the Trykit 2WD body will accept a Shimano 10sp +1 extra sprocket to work with Ergo 11 speed levers and Hubbub or Shiftmate.


Much of this may only relate to the 46mm wide Trykit 2WD trike freehub! Which are only available in Shimano spline. Normal bike free hubs simply aren't wide enough to play the sprocket adding games covered below.

Pitch of 9 speed Shimano rear changer = 4.35mm. (Changer pitch)

So Shimano 9 speed cassette Sprockets must be 4.35mm apart. (Sprocket pitch)

A 10 Speed Shimano cassette (with 9 speed Shimano spacing!) should be (N-1) = 9 x 4.35 = 39.15mm wide.

An 11 Speed Shimano cassette (with 9 speed Shimano spacing!) should be (N-1) = 10 x 4.35 = 43.5mn wide.

Campagnolo Ergo 11 speed levers have a 2.6mm cable pull per click. So 11 x 2.6mm = 28.6mm total cable pull.

Shimano rear changers have a 1.7 shift ratio. This is the ratio between the cable pull and lateral changer cage movement per lever click. The Shimano changer moves 1.7 times more sideways per click than the cable actually pulls on the changer. (Note: This ratio is different for each manufacturer's rear changers which makes life complicated for those of us wanting to swap levers, changers, and cassettes)

1.7 changer shift ratio x 2.6mm (Ergo 11 levers) = 4.42mm Shimano lateral changer movement per Ergo lever click.

10 Sprockets = (N-1) = 9 x 4.42mm = 39.78mm changer movement instead of 39.25 required by an all Shimano gear system. The difference of 0.63mm over the whole cassette width is probably harmless.

11 sprockets = (N-1) = 10 x 4.42mm = 44.2mm changer movement instead of 43.5mm. The 0.7mm difference is probably harmless over the full width of a cassette.

"HUBBUB" cable clamp modification provides a slightly smaller 1.6 changer shift ratio. (See the link below for a full Hubbub cable wrap explanation)

1.6 shift ratio x 2.6mm (Ergo) = 4.16mm cable pull per Ergo lever click instead of desired 4.35mm for 9 speed Shimano changer movement. Unsuitable for 9 speed Shimano sprocket spacing.

But guess what? 4.16mm is almost exactly 10 speed Campag sprocket spacing. So an Ambrosio conversion cassette (Shimano spline with Campag sprocket spacing) would work with Hubbub cable clamping on a Shimano changer using 11 speed Ergo levers. So, adding an extra sprocket to a Campag spacing 10 speed cassette would allow 11 gears using a Shimano rear changer. Provided there is room for the extra sprocket on the Trykit 2WD freehub. A Campag 10 speed cassette is 40mm wide. (N-1 + 1 sprocket thickness.) As is the 11 speed. High end Campag 11 speed rear changers are more expensive than 10 speed Shimano. Though Campag changers are much more affordable down through the lower ranges.

The 10 speed Shimano cassette is narrower than the Campag. Which should allow more room on the Trykit 2WD freehub for an 11th sprocket. (N-1 + 1 sprocket thickness.) Now all I have to do is work out how to index 10sp Shimano accurately with Campag 11 speed levers. Hubbub.

Highpath Engineering : Cycle information : Rear derailleurs and Indexing

Click on any image for an enlargement.


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