HTupolev

Most modern derailleurs don't need to be "fed" with very much chain, and some can move to get completely out of the chain's way.

The Stumpy I posted above, with 475mm chainstays, uses exactly one 116-link chain and has a 32-tooth big cog and a 48-tooth big chainring. Your 50-17 is 13 wrap lower than my 48-32, which means physically that about 6.5 fewer links need to be on the cogs. That 6.5 fewer links are 3.25 fewer links on each of the top and bottom runs of the chain, which is 1.625 inches or about 41mm. If you add 41mm to my chainstay length, you get 516mm, a bit longer than your 20" (508mm). So according to your chain and chainstay length claims, your drivetrain actually seems to require more chain than the math predicts when compared with my derailleur drivetrain. (Perhaps this is because of how you're adjusting the eccentric.)

base2 

We'll, just holding a long cage Alivio in my hand, I counted 9 inches or about 17-18 link pins. According to your own math that would be about 4 to 4.5 inches of chainstay length now allowed. Considering the average chainstay is about 16-ish inches long, that tracks close enough. The eccentric is a Bushnell & the adjustment range is about 1 inch as well.

How much is skewed on account of the Absolute Black chainring, I can not say.

You are welcome to come see the bike & my shop if you so desire. You in the PNW? Here is me on said bike.

Fredo76

The Rivendell Clem Smith Jr. that I built up for my brother has 22" chainstays - I just measured them.



Rivendell Clem Smith Jr.

It took several links from a second chain to work, and a tandem derailleur cable. I really like the bike, but it is really long, with a 52" wheelbase, which makes tight turns and storage a little less practical. It's fun to ride, and about as forgiving as a bike can be.

HTupolev

No. Rear derailleur wrap does not eat up the max chainstay length that can be used with a given chain length on a given set of sprockets. When pushing chainstay length to the limit for a given chain and sprocket set, the cage releases as much chain as possible, which for some rear derailleurs is all of it (i.e. the cage and pulleys completely gets out of the way of the chain).

base2 

Are we really going to argue about Circumference = π Ũ (a + b)[1 + (3 Ũ h/(10 + √(4 - 3h)))] and whether or not the derailleur cage has any relevance to necessary chain length?

Here is a hint: Even if the derailleur cage is pulled perfectly straight, the derailleur stand off necessary to guide the chain onto the cogs effects height b in the circumference of an oval formula. Google it. It's not simply counting cog teeth as gear teeth (cog circumference, chain ring circumference) are only components of the formula.

It's not hard. Chain that would normally be inside the derailleur is not in the non-existent derailleur, so extra stay length is allowed. I already told you that I don't remember if it was 112 or 116 links and whether or not I had to add/remove links from the original chain length to meet a particular gear configuration.

It's like you are lookin' for some sort of a "Gotcha" or somethin'

Nevermind.

HTupolev

Unless I'm misinterpreting what you mean by "standoff necessary", a lot of derailleurs don't really have this. Notably, models that have sprung b-pivots will often approach the black drawing below if pushed to their limits:



Strictly speaking, a derailleur drivetrain does need a tiny bit more chain length than single-speed because a bit of slack is required to allow a chain to move on and off of the most-tense gear combination, and this will mean that the bottom run of chain isn't going to be totally straight in normal operation when you're not shifting. But this is a small difference, and it can get pretty close.

Obviously there's more to the math than just adding and subtracting fraction links based on adding and subtracting sprocket teeth. But it's a good-enough approximation for ballparking modest differences, and I didn't see any need to get into those particular geometric weeds. If a high degree of accuracy and precision are warranted, the situation quickly gets messier than an oval.


That formula is for approximating the circumference of an ellipse. Bicycle chain drives are basically a set of line segments and and circular segments.

I'm just trying to work through a problem. You wrote something that appears to be incorrect, unless I misread what you were saying.

63rickert

Roadsters use chainstays around 20". The only roadster most Americans might know is the old Raleigh DL-1. Hundreds of millions of these bikes were made so there are roadsters with 19-1/2" stays and roadsters with 22" stays. For many years roadsters were simply the most common bicycle anywhere on Earth except for US. Twenty inch stays are completely normal.

Near the end of his life Pino Morroni was experimenting with race bikes and 49cm chain stays. Pino would tell you why they were superior for twenty minutes without taking a breath if you let him. Mostly it came down to the bike tracked straight and rider effort was not wasted keeping the bike on course. Front end of the bikes was normal and they steered normal. I had a short test ride on one and was surprised by how it felt like any other good bike. Pino did not succeed in finding high level racers willing to race the things.

SkinGriz

Beach Cruiser.

Velo Mule

Then there is the good ol' 1974 Schwinn Varsity with 18 inch chainstays. I extended them another 2, among other changes:
20190218_050706 by Richard Mozzarella, on Flickr

Who has the longest stays? Check your local frame builder. It might be hard to go beyond 20 inches. But, 20 inches (508mm) is certainly doable. I'd recommend to anyone, if you haven't experienced a longer than average rear-center, at least give it a try. You might like it.

I tend to think of a long rear center like the tail feathers on an arrow. It knocks down the twitchy, "racy" feel at a given trail, & replaces it with a feeling of surgical precision. The bike effortlessly tracks a straight line.[/QUOTE]

Awesome Varsity! Without the kickstand, the Ashtabula fork and one piece Ashtabula crank, well it still heavy but, going in the right direction. And weight isn't everything. I enjoy the ride on my Continental. Perhaps there were two reasons, ok three reasons for going this way. My thought are: 1, relaxed geometry 2, easy to add 2 inches of rear drop out since you could weld it with a mig or even stick welder without endangering the frame 3. Varsinentals are inexpensive and especially when their paint is poor.

Frank Berto had a Schwinn Varsity. If I remember correctly. Of course, it didn't look like this. But if he were still tinkering with bikes, it might.

base2 

There was some discussion of 26 inch wheels & what-not about 5 years ago. A 700c Powertap wheelset & 50mm rake cantilever braked WoundUp fork (for lighter handling) & polished Ultegra 6800 is what it wears now.

https://www.bikeforums.net/framebuil...ification.html

polished crankset by Richard Mozzarella, on Flickr

20200407_160806 by Richard Mozzarella, on Flickr

There are rumors that the future holds the possibility of a hybrid drive train in the form of a Nexus SG-8R36 & Microshift Nexus Alfine 8 speed right drop bar shifter and a matching left double shifter from https://www.microshift.com/models/sb-r482/

We shall see.

base2 

What's different is my bike is not your bike. I've already given enough disclaimers concerning what I remember from decisions made years ago. A single chain of "X" length, or "Y" length & maybe another link, maybe, depending.

I can't begin to presume your methodology, execution or means for arriving at your particular installation. Thus I have not spoke on it. Though I will say pulling the derailleur as tight as would be found in a SS/IGH installation & not leaving enough overage in the system for the chain to simultaneously climb over the tops of the teeth of front/rear in big/big (as in the picture above) is well...not what I would call best practice...Not that I claim that is what you are advocating,

I just don't understand the "My bike was A, yours is B & that doesn't jive with what I think is right for A & a bunch of variables no one can really account for remotely, on the internet...So you are incorrect." Why even waste time with that?

Suffice to say we both feel that the chain installation as it pertains to our respective bikes is of the correct length. Time seems to bear this out. Let's leave it at that.

SurferRosa

That's the damnedest thing I've ever seen. Wow.

HTupolev

Actually, I think we're both sizing our chains correctly.

I think you misread my original post. I was saying that your bike largely does jive with extrapolating chain length from A and the other variables. In particular, a 116-link chain would actually be expected to have a bit more slack on your 50-17 drivetrain (if the eccentric is ignored) than it has on my Stumpy's big-big.

I was using this as evidence contrary to your suggestion that the lack of a derailleur is the reason that you were able to get away with a single (i.e. 116-link) chain.

prairiepedaler

Here is what I ride. In my situation, there is too much load behind the rear axle. Trailers aren't my cup of tea if I can help it. It's very convenient having it all on one bike. I'd like to try and get the middle of the milk crate over the rear axle and thus the purpose of this thread; a frame with long chainstays. Currently, this Kuwahara Sage has 18 inchers. Yes, the brake cable is a touch knarly and it'll get replaced soon. Lasted all winter that way though! I think also I'm going to carry along a dummy p-clamp on that seat stay so that when the other braze-on fails out on the road I'll have it ready to install. The snapped one looks like it was barely tacked on. I'm keeping an eye out for something like a Kona Minute. It's sort of a happy medium between a cargo bike and normal one. They were only 800 bucks new or so and should be very economical on the used market.

Sluggo

Your current load configuration is pretty bad for riding stability and for security of the the load. I would recommend going with panniers or wire baskets to get the load lower and farther forward. Wire baskets have the advantage of providing a large platform on top for strapping big things on. I can say from expeience that you can haul a lot of groceries (or whatever) in and on top of a set of large Wald baskets. Your current chainstay length should be fine with better loading, though I agree with those who say that longer is better for touring or other rear loads.

Ironfish653

prairiepedaler It's been my experience, that, at least in the North American market, that cargo bikes (which is what you really need) are pretty rare outside of bike-popular metro areas like Toronto/Boston/NYC and the PNW. They also tend to be pretty expensive, and used prices don't scale down like 'regular' bikes, due to demand/rarity on the market.

The MinUte was a pretty rare bird, and my guess is, a near-unicorn in the XXL size you'll need. Mid-tails in general are a pretty unusual configuration.

TBH, your best bet might be to find a welding shop and have them splice a couple inches into the rear end of a 4130 MTB frame, then build around that.

prairiepedaler

Fish, yes indeed the load is imbalanced and I had thought of strapping the crate sideways once upon a time. I like the fact that lengthwise behind the rider it is more aerodynamic, and, most importantly, you can nav tight traffic without worrying about a wide load. I would certainly like to get the load centre of gravity lower for sure. It's what I've got right now so I have to work with it. I had thought about running a strut from the back of the milk crate underneath arcing down to the dropout or even the seatstay to distribute the load a little more evenly. The strut wouldn't be straight, but in an arc so it is more springy.

The MinUTE is a rarer attempt by Kona for sure. Maybe one will come around, who knows. They only made a couple of sizes in it too. A custom modded bike frame would be fun and if I had the time I'd learn to properly weld (I know how to solder well). There is no one around here I know of who could do the job. I thought it'd be kind of cool to make a 26" / 24" rear frame, getting that load level right down there. With a longer wheelbase maybe the bumpier ride from the smaller wheel wouldn't be noticed.

63rickert

For starters try moving that crate four inches forward on the rack. Not clear what it is you are carrying that requires such a big crate. The usual milk crate on a bike rack is nothing like that big.

No one paid any attention to my #32. Oh well, this place seems dominated by the bike industry and what they want to sell today. I mentioned roadsters because they are notoriously good as load carriers. Basically all the third world photos you see of enormous preposterous loads being carried on bikes there is a roadster underneath. Maybe it has to be called a Dutchbike to be understood around here.

Time to stretch your horizon. Take a look at this. https://www.ebay.fr/itm/234358456021...gAAOSweqVhzwOp
You won't be buying that because they won't ship to US. But it exists and could be done. Try looking at workcycles.com and at jclindbikes.com
There is a whole world full of bikes out there. Ad agencies that re-invented the wheel yesterday and want to make a buck on it are not your friend.

base2 

Make your case.
I thought numerous valid options, suggestions & rich discussion followed in this thread.

So, in post 32, a guy was experimenting a long time ago & his experience was similar to the experiences of us long wheel base advocates that posted here & he like to talk a lot about it... What do we do with that? Yea for our team?

Or is it that new current options exist (LHT, Rivendell, custom, etc...) & those too were suggested? But they don't count because: "industry?"

prairiepedaler

Hi there, I did see your message along with all the others. I didn't readily absorb chasing after a roadster because even though the chainstays are long, the seattube angle doesn't leave any more room that I need for the milkcrate than what I already have. I'd like to get the crate a little more forward to the front but sometimes I have a tall load in the cargo bay that sticks upwards and I have to have some clearance for the 'ol buttocks (as Gump would say). If the seatstays were curved downward, then ahhh, now we have something and the milkcrate could be inched forward. I have seen those cargo bikes before, as per your link. They kind of remind of those mail delivery bikes. I'd entertain riding one of those if they were local, common and cheap like the hardtail mountain bikes are.

63rickert

I don't know what you are attempting to carry. Large loads on a bike are plain difficult. Figuring out how to carry weight is a whole lot easier than carrying bulk. What I see immediately looking at the current setup is load carried high and far to the rear. Center of gravity is not even safe. Adding two inches or four inches to chain stays is not going to help much. Weight needs to come down and to the side.

Local common and cheap is not happening if you also want specialized and niche. United States is a place where bicycles have always been children toys. Roadsters are used all around the world. Everywhere except here. Your Kuwahara is a really good bike. You found something that is darn near best of what is readily available. Suggestion above to use XL wire baskets is as good as it gets for easy cheap available. If you want even better it is going to be purpose built cargo bike or cycle truck.

Start looking. Frame mods are at best a kludge. The base frame is not designed to take the loads generated by the extra lever. Carrying weight all the way out to the end of yet another lever is a recipe for failure. You can find the bike you want. As long as it is built with normal parts that can be serviced it won't matter if is locally unusual.

I ride a roadster daily. Carries a hundred pounds of load without noticing. Carrying anything bulky is much harder and often just doesn't get organized. Forty and fifty years ago when young and crazy I worked off my bicycle, carried a hundred pounds of paint and tools routinely. The ladder went over my shoulder. This was long before it was even possible to find tires that were up to such tasks. Lots of things are possible if you work at it hard enough. My life back then would have been vastly easier and more productive if it were possible to obtain all the things that exist today.

The original longtail was a Dutch twielingsfiets. Designed to carry two children on the rack behind mom. And do it safely with that precious cargo. Bikes have now been refined for 130 years. Use that base of knowledge. New things are still invented all the time. It does not make sense to re-invent things that have been done well and successfully and been through generations of improvement.

prairiepedaler

The Dutch certainly love their bikes! Here in Canada, bikes aren't used nearly as much as there. Probably a few more snowmobiles though are used here than there. Weather and infrastructure play a role, culture too.

Even though the load distribution is less than optimal on the current Kuwahara, I've never wiped out on a bike configured this way in 12 years and I've hauled plenty. I just don't want the frames to fail. If the rack goes, then oh well. Interestingly, the rack is rated for 25lbs and I've put way, way more than that on there and it is still holding up. Maybe a different rack with more struts would help out. The twiningfeets you mentioned there looks interesting. Many kids were surely carried that way over the years. Maybe parents should have stuffed them in side baskets for stability instead of in seats up high but at least the load is centered over the axle. We'll see what happens. Thank you for your vigorous opinion!

63rickert

Very nice to meet someone who can accept that other people have opinions and strong opinions.

Any chance you get to ride different bikes, go for it. Even short test rides are informative. Bikes are not all the same.

Tandems. Long strong frames. Made to carry a load. Lots of real estate to load and clamp to if there is no stoker.

base2 

Hey! As a follow up I happened to be lubing my chain this morning prior to a ride: 114 link pins. So, yeah, a single 116 link or a 112 plus a bit.

I guess I know what I'll be buying next time. It won't be 2, 112's that's for sure.

prairiepedaler

https://electricbikereview.com/forum...y-to-me.48412/

Similar milkcrate positioning.

https://electrek.co/2018/08/27/elect...ycle-part-suv/

Load high and to the back. The load in the front could be lower still.