Squeazel

So if everybody is sick of R20's, I can sympathize. But I'm still gonna post my pics:

Before:


After:




Dual Drive:
Suntour Honor Der
Huret stem-mount shifters
Ground-down Shimano-compatible 7-speed cogs 15/17
(just the right thickness with a 7-speed spacer between!)

Front End:
Suntour suspension fork (cut the headtube to accept 180mm steerer)
Tange 1" headset
Some old cyclocross brake levers
Tektro canti's
Nashbar 1" MTB stem
1" stem extender from Niagara bike
Chopped drop handlebars, upside-down

Wheels:
Alex DM-24 36 spoke eyeletted rims
No-name front hub/ S-A AW rear hub
Stainless 14 gauge spokes

Here are a couple of pics of the dual-drive:



It rides really smoothly with the suspension fork, and since the offset is smaller than the stock fork, I can ride no-hands quite easily. The 15/17 gearing in the back splits the difference in the S-A hub, so I have six evenly-spaced gears from about 40 inches to nearly 80 inches. I originally had a 18-tooth Shimano 3-speed cog paired with the ground-down 15-tooth 7-speed cog, but for some reason the 18 tooth cog skipped badly under load- some incompatibility with the chain probably. So I ground the splines on a 17-tooth, and the skipping problem went away. Weird.

nekohime

Ooo, green, silver, and black--sexy! It's like the Slytherin colors...

LittlePixel

Love it! Homebrew dual drive is really innovative - nice one.

phatatude

Flippin Sick Twenty... Love the Dualie too... And thanks for keepin things interesting by posting an R-20 thread

R-20's: A lil' somethin' differnt to talk about...

CaptainSpalding

Yeah. So sick of them I bought one last week. I feel a severe wallet drain coming on . . .

badmother

I`we been thinking not enough R20 pix lately. This is what I wanted!

Got a similar bike (not R20) and thinking about what to do with it. Reason for not riding it now is front fork too narrow for the BMX tires I put on.

Since I need info plse tell me:

Why did you go for those brakes instead of V- brakes? I read they are just as good if properly adjusted, but I struggel to do just that and tend to throw them oyt and put V-brakes.

Tell me more about the ground down cogs, pix plse! I am thinking of doing just this on a "big bike". Not sure if you use the same type of cogs as Sixty Fiver do on his project since you say it is from a 7 speed bike. Where is the grinding going on? Making them slimmer or grinding the theet to be lower?

I like your bike

Thanks!

Squeazel

Badmomma- Glad you like my bike. It's still a work in progress, but it rides really nicely now. I'm planning on getting a brooks flyer saddle for it, and maybe some fenders.

I used canti brakes since I already had them and the levers that pull the right amount of cable- I would have needed to buy new levers and a new back brake to go with V-brakes; they pull about twice the cable for a given amount of lever travel.

Here's a picture of what I did with the cassette. I got an old 7-speed shimano-compatible cassette and drove the pins out that held the big cogs together. Then I had a pile of cogs and spacers. You can't use the high-quality cassettes to do this- the big cogs are on a carrier that won't allow separation in high-quality cassettes. Then I used a flex-shaft tool with a tiny grinding wheel to grind off 6 of the 9 tabs in the sprocket, and round off the corners on the other 3. I ground off the tabs that were bigger and the tabs that had a hole from the mounting pins- there were three tabs that were the same size and didn't have the strength compromised by the hole. A Dremel tool would work just as well. I rounded the tabs on the spacer too- it only had 3 tabs. The stack of 2 cogs and 1 spacer fits exactly onto the hub with no play.

Sixty Fiver

Beautiful job !

I like the Suntour derailer... I have found then to be perfect for dual drives since they are so very robust and work so well. I use Shimano 3 speed cogs for dual drives since they have the same spline pattern and can be swapped into the place where the SA cog and spacers sit.

My dual drive Twenty went to live with a nice lady who was all set to buy a new hybrid and now cannot imagine not having such a cool little bike that does everything so well... she tells me that the performance has been pretty much flawless.

I'll probably be building more.

Squeazel

Thanks!

I thought it would be easier with the Shimano 3-speed cogs, too. I tried 2 different ones, and 18 and a 21 tooth, and they both skipped under load. I decided that my chain was incompatible somehow- I only had a 7-speed chain, so I broke apart a 7-speed cassette and modded those cogs. The beauty is that the original shifting ramps on the cogs are lined up since they used to be adjacent on the original cassette, so the shifting is absolutely flawless.

Sammyboy

Great stuff! I might actually make progress on mine after I pick up Mulleady's crippled Downtube this week - expect an intermediate model with 8 speed SA hub, til I get my Nexus 7 wheels built.....

Sixty Fiver

3/32 chain is what a Shimano cog needs...the chain rings on a Twenty is also 3/32 (if Raleigh versions are the same as the Phillip's model).

veloceleste

Nice bike! Never too many R20 threads or pics.

badmother

Thank you, I get it now. Asked about doing this in the utility forum (in a Big Dummy tread) but the response was not great. The thing is I`we got some chainline problems on my "longtail", so I was thinking of going to "go hubgear" on it. Since I am not buying a Rolhof and they say the Nexus 7 is not strong enough for utility bikes (heavy load) I got the bright idea to use a 3 speed hub (stronger than a 7 speed) plus 2 cogs. Maybe two crank wheels also?

This is my longtail. Love it since I do not go far without "the animal" but often go to far for the same animal..

stevegor

Squeazel and/or Sixty Fiver,

I was fiddling around with my hub and installed 18t and 16t SA cogs back to back, then tried a Shimano 9 speed chain and it fits without scrubbing the other cog, do you guys think that it's going to work when actually on the bike?

Squeazel

I dunno... You might have the same problem with chain skipping that I did. It seemed to work on the bike stand, but as soon as I put some force into the pedalling, it would skip. I was using a 7-speed chain on shimano 3-speed cogs. The 7-speed chain wouldn't even seat on my SA cogs; the teeth were too thick for the chain.

Sixty-fiver? You've been doing this a lot longer than me...

griftereck

Hi folks. Im not new. Im Alecw35. But cant log on as I cant use a password. GRRR

Standard SA cogs need the 1/8" chain.

I have a Shimano 18 tooth cog on Lil blue bike. Thats a pressed steel cog that can use a 3/32" chain.

I was going to get a cog from SJS cycles shop. They have a range of cogs for hub gears.
In either 1/8" or 3/32".
They are about £10 with the P + P

social suicide

Beautiful!
https://www.feckinwhiskey.com/index.html

MyrtleBeachGolf

Squeeze---Great looking bike. I just bought an old "20" on Ebay and it will arrive next Wednesday. It is going to look much like you original ( green too) , but some day, after see so many cool pics of mods, I want it to look something like yours. I love this forum and know I will be able to get the advice I need to do my project but one thing really interest me and I have no clue as to the answer. What kind of investment would you have in alll the modfications you have made. I'm brand new to the forum, so if $$%$ qyestions are inapropriate I will understand....thanks.....J.T.

Squeazel

MBGolf,

IIRC, it wasn't cheap, but mine came without forks, so that was an investment you probably won't have to replicate. Here are some costs for stuff I actually bought:

Bike bones from Craigslist: $20.
Wheels: rims $20 ea, spokes $30 for all, used front hub $5, tires $6 each, tubes $3 each, rims strips $.5 each
Cables: figure about 2 bux each for 4.
Front end: Fork $35, headset $6, stem riser $12 (?), brakes $10, bar tape $5
Dual-drive: used derailleur $5, used shifter $5
seat post $20

The rest of the stuff from my parts box: handlebars, stem, brake levers, old cassette, pedals, seat, brake pads, I dunno what else.

Eeek- I just totaled it up- 215 bucks! I should take up golf!

Really, it's like "cooking the frog". The expense comes out in dribbles as you find you need parts. Most of it came from Niagara bike, notable exceptions rims and spokes from aebike.

Have fun! And Welcome!

scale

Digging up this old thread.....

I am thinking about making a 6sp like this.

What chain did you end up using?


I have sourced my rear mech, hanger and i have taken the pins out of an old 7sp cassette. I have my 15/17t and spacer all set to go.

did you have to grind your drive side axle nut to be skinnier to allow for the hanger and the indicator chain nut? I am thinking there is no way the indicator chain nut woudl go on due to lack of threads showing after the hanger was mounted. You really cant recenter or change the axle position with the cones.

Finally......how did it ride and shift from 15/17t? was it quite smooth? It looks like a fun project.