ScrawnyKayaker

Sorry if there is another forum for retro-directs, but my search attempts didn't find it. Please aim me there if it exists.

Anyway, since a RD uses two single-speed freewheels stacked on the hub, this seemed like the place to start. I'm planning a setup like this
https://kentsbike.blogspot.com/2009/0...ro-direct.html
but WITHOUT the front derailleur.

I've got most of the parts, but still need a chain. I'd like to have a chain with several different red, white and blue colored segments, so the progress of the pieces through the driveline will emphasize the weird set-up (and encourage me to keep my chain clean for the first time in my life!) So far, the only 3/32nd chain I've found that comes in these colors is the KMC Z610. There's no shifting of the chain in a RD, but the chainlines will be far from straight. Will a single-speed chain have more problems with this than a 7 speed chain?

Thanks,
SK

FlatTop

A single speed chain would be 1/8", and wouldn't work as easily as 3/32" chain, which is made to flex more than SS chain in order to work with less-than-perfect chainlines. The antique retrodirects probably used 1/8" chain, but the chain for 5/6/7/8 speeds would have to be an improvement. Chain for 9 and 10 speed clusters is not sized right for your application, I think.

zzyzx_xyzzy

that's me!

Actually I suspect a 1/8" chain will work fine. Maybe even better. Less flexible makes for less chance of derailment (witness old 'ghost chain' setups that were ridable with no chain tensioners at all) and with the chain always rolling with no tension over one freewheel or the other, any sideways flex over a bump makes it quite easy to drop the chain.

FlatTop

I'm pleased to be corrected by an actual retrodirect builder/rider!

I would have guessed that the use of a 1/8" chain on a chainring or cog that is smaller in width would tend to introduce sideplay, making the chain more likely to come out of line and jump. But the greater lateral stiffness of 1/8" chain vs. 3/32" chain might be of more benefit.

How foolproof would a completely 1/8" retrodirect setup be? Food for thought.

ScrawnyKayaker

Not all single speed chains are 1/8". The KMC I referred to is a 3/32" single-speed chain. The sideplates are different than a shifter chain, I believe. Unfortunately, the moderators instantly moved my post out of the single-speed group where this would be common knowledge and I might get better info.

https://bestsinglespeedbike.com/index...05e8294ae1ed33

TejanoTrackie 

Your post is still visible in the SSFG forum (I left a redirect icon there), and will be for another week. So, you are actually getting exposure both here and there as well. The fact that that no one on the SSFG forum has contributed indicates that you are better served in this forum. The chain you are referencing is actually a BMX chain, and rarely used on single speeds, although I have seen track bikes with 3/32 drivetrains that use it.

ScrawnyKayaker

OK, true. I should be less *****y about that (and pretty much everything else). Sometimes I'm MORE likely to read moved threads in forums, to see what the transgression was. I assumed I'm weird that way and that serious people ignore them unless they're interested in the destination forum, but I'm probably a lot less unusual than I like to think.

A retro-direct just seems to involve a lot less welding and a lot more SS freewheels than most of the bikes here. OTOH, I guess pedaling backwards half the time is pretty "alt," so I have to give you that point.

Thanks to all who replied,
SK

ScrawnyKayaker

What the...? They just let the chain dangle loose?!? Whoa, that's just too scary.

Hmm. The Z410 1/8" also comes in my target colors, and it's a lot cheaper. (Why??) Pretty tempting idea.

ScrawnyKayaker

Hey, Peter, how come you never ride your RD to work any more?

I just realized that by using a BMX LHD hub, it would be possible to turn it around and make an RD with the chains leading under the freewheels and up to an idler on the seatstay, which would seem to have better clearance WRT the chainstays and would look even crazier. Unfortunately, A. the range of available cog sizes seems limited, B. they are not threaded all the way through, and C. the chain would probably fall off on every bump. Also, riding backwards would be dangerous!

TwoShort

On my Retro-Direct I use 3/32 chain, out of the belief that it twists more easily. But I don't guarantee I know what I'm talking about The idler pulley seems to work best if it is at an angle so the top and bottom are in line with the freewheels the chain is running to. This causes the chain to twist rather than displace sideways.

Here's my bike, by the way: https://twoshort.net/bikes/retrodirect/

You will certainly need some way to adjust/ensure chain tension or otherwise prevent derailments, which have been my bane. The spring & swivel scheme depicted on that page is definitely the smoothest running on I came up with, and ran great right up until I managed to kick the whole deal into the spokes. I've rebuilt with a rigid-bracket scheme.

Anyway, good luck with the bike, and keep us posted on how it goes!

ScrawnyKayaker

TwoShort, that's a handsome bike! I like that idler pulley. It looks really clean with the spring parallel to the bight of chain. Did you abandon that system due to the mentioned failure mode, or lack of replacement parts? Did the wheel survive??

TwoShort

That idler looked really nice, ran smooth and was easy to get set up right. In addition to the spring, there is a swivel so the pulley can twist. If you get the attachment point in the right plane, everything just floats to where it should be. But...

The pulley always moved around quite a bit; it would ding off the chain stay every time I dropped off a curb. Finally, in the midst of a hard sprint it swung (or maybe I kicked it) into the rear wheel. The spring got completely ripped apart; the wheel lost a couple spokes, and locked up completely with the chain wrapped around the hub. Maybe because I was so far out of the saddle, this produced a very long, easily controllable skid; I didn't even fall over.

I couldn't figure out how to build a spring system with this ones advantages that wouldn't run this risk (or not within the confines of my engineering ability). Moreover, my internal vision of the perfect retro-direct has no spring, or something like that. Note that this was the 4th repetition of the cycle: get this bike working, use it for 2-8 months until it breaks, and hang it on the wall for 1-4 months until I feel like taking another wack.

For repetition number 5 I returned to the rigid bracket I had learned a lot about in cycles 1-3, filled in the holes in the frame from previous experiments, gave the whole thing a nice paint job, solved the pedal-unthreading problem once and for all (epoxy), and generally spiffed up the bike a lot. This edition was great for 6 months; no problems except once that the chain derailed from the big freewheel with no great consequences. Then it derailed again, fell off the rest of the drive chain until it was dragging from the bottom bracket, and got under the rear wheel for a skid that tossed me hard into the pavement.

So now I'm actually in the hang-on-the-wall phase awaiting cycle number 6... which probably just means putting a plastic disk alongside the big freewheel to prevent it's derailing. Which will be ugly in both a visual and mechanical-purity sense; but road-rash is good motivation to compromise.

Have I convinced you you need a retro-direct yet?

zzyzx_xyzzy

Sometime early this year I had a bit of an epiphany about what a proper bike fit for me feels like. I don't have any more enthusiasm for cramming myself onto a bike with a seat tube shorter than 66cm or a top tube shorter than 62cm, so there are bikes I'm not riding until I find suitable frames, which is a problem.

There really are about 4 times as many ways to drop the chain on a retrodirect. At the moment I'm wondering if an internal gear hub could be modified or built to operate in reverse...

frameteam2003

In building a RD you will need an ideler wheel of some sort to run your chain "back" .I modified a derailer for this ideler so I'd have a spring that would take up slack and make taking the wheel off easer.

frameteam2003

And while we're talking about weird freewheels---FYI---you can get on Ebay a blank --no tooth--freewheel made for those cheep electric scooters---same freewheel as used on bicycles only they have a flang with bolt holes not a toothed cog.

zzyzx_xyzzy

OK, i just had an idea for setting up a retrodirect that looks good on paper. i'll say three words. "double ghost chainring"

TwoShort

As far as the big freewheel, I use a 4-arm mountain-bike granny chain ring, bolted to the side of a 16T bmx freewheel, so the bolts just come out between the teeth. You can get a 24T 68mm BCD one (used in one short-lived generation of Shimano), and use standard chainring bolts. Or with some creative use of spacers you can use 64 BCD rings and get any size you want.

VT tallbike

How are you guys fitting the two freewheels next to eachother? I've never seen a hub with enough threads for that.

lverhagen

VT tallbike,
One freewheel is threaded halfway onto the hub, an adjustable bottom bracket cup is threaded into the remaining threads on the freewheel (they have the same thread), and a second freewheel is added with a spacer between them. A pseudo-decent system for an obscure drivetrain.
Currently, I am looking into the viability of machining a hub with enough thread on the actual body to allow better thread engagement for both freewheels, narrower chainline, and more even wheel dish.

tatfiend 

The new Sturmey Archer S3X is a FG 3 speed hub that can drive forward or reverse. No built in freewheel at all.

ScrawnyKayaker

You've convinced me I need a plastic frisbee over my spokes on this bike, but I already knew that. Maybe I'll also go back to shaving my arms like in the good old days, to make removing the bandages less painful

What happens when you need to pull the freewheels off? I'm worried this is going to be a semi-permanent assembly. I got the rest of my parts yesterday, and happily, the freewheels fit (barely, there's not quite a millimeter between the outer freewheel dogs and the dropout). The ACS BMX freewheel tool I have can access the outer freewheel easily, but the hole in it won't pass the axle nuts and spacers, so it can't reach the inner freewheel or the BB cup. Is there a BMX tool that has a big enough hole to slip over the axle and reach the inner freewheel? Or does the whole freewheel sandwich tend to come off together (which would seem to pose it's own challenge, to put it mildly, but at least it would be off the hub...)

Unfortunately, the BB cup I have needs to be put on so the bearing race faces outward, 'cause due to the way it's threaded, the threads barely engage the inner freewheel if the cup faces in. That means the notches on the back of it are inaccessable to any tool, and while it's in place, getting a tool on the inner freewheel dogs isn't possible even if the axle fits through the tool (or is removed). I'll probably try to machine some grooves in the cup that a tool could engage, but it's pretty hard steel! I enlarged the hole in it so it would fit over the axle nuts with a dremel tool and a carbide cutter, then a diamond-coated grinder, and it was a chore, and came out FAR from round. I think I damaged the rat-tail file I tried also. Cutting decent square notches in it with hand-held tools and my hands seems pretty dicey. What do you guys find is needed to get these apart?

ScrawnyKayaker

So far, so good! Got it on the road today for a couple of miles without any parts breaking or falling off. There is an intermittent clicking I haven't figured out, although it may be the chain slipping over the idler pulley (actually two pulleys sandwiched together). It sounds kinda like the crank creaking, but I don't recall that being a problem in the fixie incarnation. I'm REALLY good at forgetting things, however!

Thanks for the advice, especially Peter for the example of using the chain tensioner to carry the idler and placing the smaller gear inboard, which makes this project surprisingly easy.

Here's a video on the workstand. Can you see the ACS freewheel wobbling? I think the body was bored askew!
https://img529.imageshack.us/img529/2416/48423533.mp4

The gearing is a little on the high side with the 52 tooth ring. I should get something like a 48 or 49, but it's a 144 mm BCD crank, so odd sized rings don't exactly litter the ground.

ScrawnyKayaker

Nice find. Any idea if the bolt holes match any granny gear chainrings, or if the flange is wide enough to bore holes to match?

zzyzx_xyzzy

I love the chain!

I actually went back to the toothless roller that came with the tensioner, seemed to drop chain less.

Expect to be loctiting down your pedals, your BB cups, AND your chainring bolts (the last one was a surprise for me.)

Undoing the freewheels -- haven't crossed that bridge yet.

I have one of the 4 bolt electric scooter freewheels in a box somewhere. The holes are close to 4x64 mountain bike BCD, but the holes are smaller, and the body of the freewheel is a bit too large to allow a chainring to slip on. Might be easier to braze a steel chainring on to a smaller freewheel.

ScrawnyKayaker

Thanks! I pretty much wore out my chain tool; going to have to file the pin flat as it's now pretty gnarled. My daughter told me I need to paint white stars on the frame. Maybe I'll look for some stickers.

Crud, I thought the Kore pulley looked too small, so I spent way too much time cleaning crap off the old pulley wheels. I spun a piece of polyethylene lab tubing in a drill to sand it down to fit through the bushings and around the bolt, so at least that was cheap and painless.

I was able to carve BMX tool notches in the edge of the adapter cup successfully. I must be getting the hang of the Dremel. May have been another waste of time. I didn't bother trying to remove the freewhell after cranking up the hill, but after test spins on the workstand, the freewheels tended to come off as a lump, so the challenge will probably be getting the two freewheels apart. I may need a big chainwhip.

That's another good idea you have for the flanged freewheel. A friend of a friend likes to weld, so if you decide you don't want that freewheel, I'd buy it from you and see if he can stick a 26t steel ring to it.