khatfull

Actually no, it came stock with a 6 speed freewheel if you look at the catalog page:

https://classicfuji.com/TouringSeriesIII_1984_Page.htm

I did run what you suggested and sure, I see those nice even jumps. The 13T is easy...might take some grimy searching at the co-ops to find a 34T.

Interesting, thanks a lot!

khatfull

I did, and this is what I get:



Better?

Sierra

Much better!

Note the nice, relatively even jumps between the ratios on the middle and large chainring(excepting the 13t & 14t).

The other charts you showed did not have even ratio jumps and some were near duplicate ratios.

This one is a pretty nice half step setup for touring.

I'll be interested in reading the Gearmeister's(John E) opinion of it. I like it though.

khatfull

Well, I got and disassembled a total of 4 Suntour freewheels and tried putting together what I ideally wanted. I couldn't make a 13T sprocket work with what else I had so I put this together and installed it on the bike tonight:



The only twitchy shift is around the 20-23 sprockets. Otherwise I think it works pretty good. Drop the useless top three in the 28 ring and I have a pretty even 15 gears from 22 to 96 gear inches. I would have liked to get over 100 gear inches on the top end but I'll have to live without unless I come up with some odd sprockets.

Here's the stock gearing for comparison:



I think it's much better now:

1) More even shifts (except for that one).
2) Almost no duplication.
3) Got lower gearing without sacrificing the stock top end.
4) With the 28-34 combo I'll be able to spin up danged near anything.

I rode it just briefly tonight and it was obvious out of the gate that it was different. Once I get used to shifting the barcons I'm sure I'll get more in tune with the half step and hopefully it will work well for me.

Comments?

onetwentyeight 

Freewheel: IRD 14-32 6 speed
Crankset: TA Pro 5 50-46-30

on my 1970 jack taylor tour of britain rebuild. all gears are usable except the chain sags if in the granny and using the two smallest cogs on the freewheel. using a nuovo record rear derailleur with a gran sport cage and a regular nuovo record front. shifting up front occasionally is rough grinding out of the granny but when I drop to the granny its a commitment anyway... I've been using this system for the last year or so and its great, i find myself using the half step regularly (i am using friction bar end shifters up front). Occasionally I wish I had more top end speed, but then I remind myself to slow down.

I should take some new photos of the bike, I've made some tweaks to it that have moved it from a bike I liked to a bike I love, notably new seat, bars, raised the cock pit, rear wheels, and new pedals. its less period correct now, but way more fun.

Grim

Ok you got me back interested in tinkering on this. Had a couple more clusters show up including a 7 speed sun tour with a 13 that I can use as the start.

LeicaLad 

The Avocet triple on my '77 PX10: 50-47-26.



Freewheel : 13-15-17-20-23-26



I made this little chart to tape on my bars:

... 50 47 26
13 04 98 54
15 90 85 47
17 79 75 41
20 68 63 35
23 59 55 31
26 52 49 27

John E

That is one fine set of gears! Nice gear phreaking, as Frank Berto would say.

LeicaLad 

That was my first real "project" bike. I spent the winter of 80-81 doing the math and building the drive train. (As my sister said, it was cheaper than therapy!)

I haven't seen another Avocet crank set, triple or otherwise, in years. Wonder why...?

muccapazza

Yes, you really should! (take and post some new photos). How long to get that mirror polish on the crank, and how? It's a beauty.

old's'cool

I believe I posted about my half step setup a while back in this thread, but without photos. Here are the photos. Bike is a 1989 Peugeout Versailles, fairly unmolested except for the gearing. I use it for daily commuting ~25 mile round trip. Gearing is 52-48/13-15-17-20-24-28

onetwentyeight 

It came like that. I got lucky on a NOS set that had been misspelled on ebay. I ordered the chainrings from Bicycles Specialities in Canada. I'm more of a beausage and paint chip guy than polish and restore, so on my old bikes shiny is usually an accident. My apartment is too small for me to own show bikes. I'll try to take some new pictures tomorrow or monday, as I will be off work. *ahhhhh*

-a

The Golden Boy 

1984- Trek 420 with the mighty 50-45-28 in the front:

Sixty Fiver

1957 Peugeot PLX8

Has a 4 speed block in the rear with a 15/18/21/24 and a 44/48 up front and works really nicely once you get used to using the suicide shifter to shift the front.

Range is 50-86 gear inches... makes her pretty quick on the road if you are the type who can spin fairly fast and put down some power on the climbs.

gear freak

i keep half step gearing on three of my bikes because it is so nice. as a gear freak i know how to use half step gearing.i have been using handlebar end derailleur controls since i installed a triple crankset on what had been a 8-speed bike. not a schwinn varsity, it had one those front derailleurs you had reach down to the seat tube to shift. that would not work with half-step gearing. i installed the triple crankset in 1970. many cyclists said my 15-speed they had seen. no one knew what they were doing back then & frank berto had not yet written his gearing articles. i looked what other cyclists had on their bikes. while i had sloanes book with gear charts to this day i still prefer to use to use a 4 function calculator with memory. i calculated so many gear trains that i wore out the multiplication button on a sr-50 calculator. i blundered on to half step gearing. i is so much easier to double shift with indexed bar cons. so my user name on the computer is gear freak because in started gear freaking before frank berto. the bikes that i own that do not have half step gearing is 21 speed klein team super which i equipped with crossover gearing as an experiment, it certainly is easier to shift & a 54 speed greenspeed gto trike. half step won't work with 20" dia. wheels. on the trike i have a gear range of 10.4" t0 121.8". 22 usable gears, 3 duplications. i am male, i have not been able to teach most o my female cycling companions how to use half step gearing, however i have had some sucsesses, & i did not have to teach emily at all. i am not collector who wants to keep vintage bikes in their original state. i believe that it is worth while to upgrade bikes, 3 of my custom assembled bikes did not origanally have indexing. all of them have it now. when indexing came out was not since i did not want to spend more money on three nice bikes. so i decided to take a wait & see attitude & it took shimano a while to bring out their bar con, for which they will not supply spare parts. once i bought with indexing a & so how nice it was, changed my mind.

JohnDThompson 

My wife's TS Isaac with TA Cyclotouriste:


Avocet on my innominate Italian commuter:


Sugino AT on my Trek 720:

Captain Blight

Hey, it works for 3-speeds, too!

No photos (yet) but I have a Sachs Torpedo 3-speed coaster brake hub I laced into a Velocity rim for my winter ride (Specialized Crossroads frankenhybrid). I'm setting it up with a triple ring up front (tensioner used, natch) in 40-45-50 for a total of 9 evenly spaced gears, which see on the right here:

sailorbenjamin

So I picked up this sweet old Trek 613 (or is it a 614) a couple of years ago before I understood half step. I started looking at half step gears a few months ago while setting up one of my old Ralieghs and realized that the 50-45-28 on the Trek was a really nice start on a half step system....
Then I looked at the freewheel, and then I double checked the brochures and sure enough it came this way. It's got a 6 speed, 14 16 19 23 27 30. Seems so completely wrong. Why did Trek do this? The rest of the bike seems so well though out.
Well I put a 5 speed 14 17 21 26 32 on it and that seems so much better right? That was just last week and the front derailler isn't working right and I haven't had time to adjust it so i haven't yet tried this half step business o yet but the math is fun.

old's'cool

Captain Blight, nicely done!

JohnDThompson nice pics!

gear freak " one those front derailleurs you had reach down to the seat tube to shift. that would not work with half-step gearing", can you define "would not work"?

gear freak

so i may have made a mistake. so can get the chain to the correct cogs with a derailleur that you have to reach down between your legs to shift. but you have to use your right to shift two seperate systems. you can not simitaneously double shift like you can with handlebar end derailleur controld,to do this. the shifting will be slow & that why i said half step will not work with this. in 1970 i had a campagnolo record front with a 36-47-52 teeth rings. there was no derailleur that would shift well over a crossover triple until the simplex slj 523 front derailleur can out in 1979. in boston that cost $20-$30, which was a fair price. i recently saw it on a internet site for $115, which is pricey. i have 2 or 3 of these derailleurs because when these came no one was really sure what were for & i am glad that i picked a few. a road front derailleur is what you want to use for half step plus granny. i may have to reshape the cage on my simplexes, i plan to use them on my 44-57-67 crankset on my tricycle.people stated they big chainrings i bought these from highpath engineerimg in wales. the 67 was about $165. a 68 tooth ring to 110 ( the maximum) is $500 (egad!). they do nice work.

Ruffinit

Actually I prefer doubleshifting (one hand two shifters) with down tube shifters to any other method of halfstep shifting. I'll guarantee that you would be hard pressed to shift faster or more precisely than I. It all comes with practice and experience. Though I've had barcons on one of my bikes for 15-16 years, I find that I am much better shifting a DT shifter than with the barcons. (friction of course)

old's'cool

I routinely upshift my setup (i.e. both levers forward) with one hand simulaneously. This works well as I can use the palm of my right hand on the RD shifter, while operating the FD shifter with my thumb.. I can also do the opposite, one lever at a time in quick succession, so that the interval hardly matters. The skill of simultaneous pulling with different digits for a one-hand 1/2 step downshift, that Ruffinit has apparently mastered, is something to aspire to.
I should point out, my setup is indexed RD, friction FD (but only two positions).

Road Fan

Designing a half-step is kind of a systems engineering problem. There are two systems to design. First is an ideal half-step system which ignores the facts that you can only count gear teeth in whole numbers, and that you can only buy certain rear and front sprockets in today's market, and other practical goals and limitations. Second is to design a real-world half step system, or more likely a bunch of real-world systems. These are based on cassettes/freewheels and chainrings that are either on hand at your workbench, or can be bought on today's market. The real world half-step systems are evaluated against the ideal one to determine which real half step system is the closest to the ideal one, and which still meets practical constraints.

It's the requirements of the ideal half step system that define what's unique about them. The goal of a half-step system is to use a zig-zag shifting pattern, in which each the gear inch ( or gain ratio) increment between adjacent gears is the same percentage over the whole gear range. For example, suppose you want a 14-speed system (2 chainwheels, 7-speed rear end) with a top gear of 100 inches and a bottom gear of 35 inches. The total ratio is 100/35 = 2.857.

The ideal incremental ratio is (2.857)^(1/(1-14)) = 1.084, or 8.4%. This step ratio is the half-step. A whole step for this system will be twice the percentage, 16.8% or 1.168. The chainwheels are selected to be separated by the half-step ratio, and the freewheel cogs are to be separated by the whole step.

If we want the smallest rear sprocket to be 13 teeth, the ideal line-up of rear sprockets is as follows:

13, 15.18, 17.73, 20.71, 24.19, 28.26, 33.01

If we round these off, we should look for a freewheel or cassette with 13, 15, 18, 21, 24, 28, 33. I have not seen anything quite like this.

The chainwheel ideal ratio is 1.084, or 8.4%. For 100 gear inches, a 27 inch wheel diameter, and the 13 tooth small rear sprocket, we need a 48.15 idea chainring, or 48 teeth in real-world parts. This we can buy. The inner chainring must be 8.4% smaller, or ideally 44.42 teeth. We can round this down to 44 teeth. So we have designed one real-world system using a 48/44 chainset with the 13/15/18/21/24/33 freewheel.

How good is this? Well first notice that the real chainset ratio is 48/44, or 1.091. This is not the same as 1.084. It's as close as you can get, but not the same. We should also look at how good the freewheel is. Here we need to calculate (I use Excel for all of this) the ratios of adjacent pairs:

13
15 1.154
18 1.200
21 1.167
24 1.143
28 1.167
33 1.179

Again using Excel I calculate the standard deviation of this right hand column, and in this case get a value of 0.0198. This indicates that the freewheel cogs are pretty good approximations to the ideal case.

Problem is, I haven't seen any odd numbered cogs in the 30's for decades. I know I can get 32s, if I shop Ebay long enough - both SunTour and Sachs made them. So, what should a 13/32 look like, noting we are trading away some gearing range to target cogs we might be able to get: ideal ratio 13/32 is 2.462, and the ideal increment is 1.162. If we just substitute a 32 for the 33 above we get a standard deviation of 0.0239 - still really good!

The ideal chainring ratio is now 1.081, which requires a 48/44.4. Again we round to 48/44.

Khatfull, if you would like to put these just for example on the Sheldon Calculator, you could see how they work.

As far as your two designs, their problems are related to chainwheel ratios. For the 14/34, you need an ideal chainwheel ratio of 1.097 (50/46 closest), and you have 1.111. For the 14/28, you need 1.074 (50/47 closest) and you have 1.111 again. In both cases the middle rings need to be larger than the 45 you have chosen.

thook

I'd run into this same issue with my '82 Trek and the Sugino AT it was equipped with from factory. The chainwheels were geared at 50/45/28. Road Fan, SailorBenjamin, and few others might remember this as I'd started another thread to ask my own questions about it:

https://www.bikeforums.net/showthread...=half+stepping

The closest I could come to meeting the 1.111% ratio between the 50T and 45T rings was 1.106% with a rear cogset geared at 13/16/19/23/28/34. I tried it and it worked well enough. But, in order to have the granny gear set up and eliminate the redundant gears (you'll see if you were to draw it up on Sheldon's chart), I was going to have to drop the granny down to 24 or lower even. However, the Sugino won't allow for anything lower than 24T with the BCD. This presented another issue with my rear derailleur, though; the Suntour Cyclone couldn't handle the chainwrap. IOW's, on the 24T chainring and any of the smaller cogs below 19, the derailleur couldn't take up the chain slack. That was annoying because I wanted to be able to use those gears if I needed to. Since I didn't want to forgo using the Cyclone derailleur, I had to regear while still keeping a decent range of gears. So, I used the 45T ring, stuck an SR 42T next to it, and threw on an SR 24T granny.. Then, I built a Suntour freewheel of 13/15/17/20/23/26/30. This worked out really well in a number of ways besides being able to keep the Cyclone; finer and more even steps, more gears, and an even more usable high gear (not a lot of flatland around here) while still having enough low for my purposes. I atleast had to try with 50/45, though.

Oh, I tried 50/46 with a 7spd in the rear, also. Upon Road Fan's suggestion, I bought a cassette of 13/15/17/20/24/29/34. Again.....I ran into granny/redundant gear/chainwrap prob's with the Cyclone. Meh......so, I'm using the cassette with 50/46/24 on my Dawe's. I bought a Huret Duopar for that set up. Another gleening of Road Fan's knowledge.

brockd15 

Here's mine on an '83 Voyageur SP.