New (non-vintage) tandem into stretch

[Raoul Dude]

I don't really know WHERE to post this but wanted to share:

"Craigslist Nightmares and Dreams" because of the nightmarish comedy of errors involved with getting this bike?

"Show Me Your: Tandem into Singles" because that's what I'm planning on doing with it?

"Build Threads" as I take this thing apart and put it back together differently?

Another forum entirely because I'm new to rat roddin' and so far have only done three "bolt together" builds? (I don't have a welder, haven't used a hacksaw or angle grinder on either previous bike, and I'm hoping to do THIS project so I can completely reverse any changes and make it back to "stock" if I meet someone who wants or needs a tandem.) Obviously, this bike isn't "vintage" except in the sense that it had a previous owner for a year or three -- I've got concert t-shirts older than some RRB members, but I suspect I have some canned goods in the back of my cupboard that may be older than this bike!



I've been wanting to try something like this since I saw my first stretch cruiser, but how often do we run across used tandems on craiglist? More importantly, how often do we run across barely-ridden multi-speed tandems on craigslist for SEVENTY-FIVE BUCKS, including delivery? (Your city might be different, but this is the first one like this that I've seen in Columbus.)





This may be the shiniest bike in "Fresh Finds" in 2014, huh? The only things wrong with this bike when I got it were miniscule: it needed one new inner tube, the front derailleur needs adjustment since it won't drop into the low chainring, the stoker seat wobbles horribly because the "nose bolt" underneath fell off somewhere, the front chain was derailed and both chains need lubed. There are a few paint nicks in the "bottom tube" that connect the bottom brackets, but they're not even through the primer. I feel like I got a great deal on it, even though it's a department store bike, probably built in the same Chinese factory where they build the Micargi and Walmart Schwinn tandems. The hubs were well greased, the bottom brackets felt smooth on my one short ride around the block, and the rims were almost perfectly straight when I got the bike. (The derailleurs and other components are pretty low-end, but I can always upgrade them with [I think] standard mountain bike parts.)

I've been joking with slowriderz via PM about the trials and tribulations involved with trying to measure this thing for one of his solid seatposts. I'm planning on moving the rear seat forward about 5" so I rode up and down my block on a balmy 50 degree December in Ohio day, sitting on a series of half-baked "seats" cobbled together from cardboard, towels, Saran Wrap and duct tape, secured to the rear twin top tubes. I can reach the front pedals okay, and it feels a LOT like my five minute test ride on a Micargi stretch tandem a few months ago.

I'm planning on some sort of apehanger handlebar angled somewhat to the rear, but I'm going to try to wait for warmer weather (and my new seatpost) before I try to decide just how much handlebar to buy. The usual 15" rise ones might be a bit too short, but the 25" ones I experimented with on another bike might be too long, and there aren't that many affordable bicycle bars in between. The good news is that I don't THINK I'll need to buy new tandem brake cables to make them fit, though I may have to route them a little differently.

Shifter cables might have been a problem, but I think I've figured that out, too. What to do about that front seatpost tube sticking up in the air? If I didn't want to preserve this as a potential tandem again, just cutting it off would make sense. Since I want to leave it there, why don't I make it useful and put the shifters back there? I can leave the stock seatpost in the seat tube, with the "stoker stem" pointing forward and away from me, and move the Grip Shifts back to a short length of handlebar mounted in the stem! (Bonus style points if I decide to build two new stick shifts and install them over the Grip Shift guts?)

A badly-Photoshopped picture, minus the new handlebars and stem:



I'm not wild about all of the stickers -- there are three "Peerless" stickers on each side, and what in the world is "Extreme" about a tandem cruiser?! I'm a little worried about the shiny metallic silver-and-gold stickers covering what could be a horrible silver-to-red fade on the top and down tubes, but I'll find out when I peel the stickers back.

Then it will just be a matter of pulling the rear pedals (or the cranks) and putting some more efficient tires on there, and I'll have a totally sweet, customized stretch cruiser for less than $200, right?

Yeah, I didn't really think so either, which is why I made this thread. I know nothing about "timing chains" or "idler pulleys," at least when it comes to bicycles. I know some of you purists and/or flatlanders are thinking "who needs a multi-speed bike anyhow?" but I like having gears to climb the hills around here. What else am I missing or do I need to know? Are the rear cranks going to come off normally, or will there be some weird reverse-threaded nuts and bolts in there, like left-side pedals? When I reseated the "timing chain" did I leave too much slack in the top part? It looks like it's sagging a little but I don't know if I can get it any more taut without taking the chain apart. Are there any secrets to adjusting that timing chain's idler pulley? It seems simple enough with only three adjustment angles -- I'm guessing it should just be there to keep the chain in line with the two chainrings.

Any information or obvious ideas I've overlooked would be welcomed!

 

[slowriderz]

ill be keeping my eye on this build. It will be very cool I am sure!

 

[Georgeediii]

Just me but if it were mine I would cut the top half of the rear triangle off and lower the seat down to just above the cantilever. Long and low. Also there is nothing saying that you can't pull the entire rear sprocket set up and flip the front one to the other side. Cool project.

 

[RustySprockets]

Just a guess, but I suspect you'll discover the chainrings are permanently attached to the cranks. You won't be able to easily remove one without the other. Did you have a plan to address that? As far as I know, the BBs are standard square-taper items, so parts are plentiful.

 

[Raoul Dude]

Just me but if it were mine I would cut the top half of the rear triangle off and lower the seat down to just above the cantilever. Long and low.

The more I look at this thing, the more I AM tempted to say "forget about keeping it original -- I'm never going back to 'stock!'" -- and it WOULD look a lot better without those extra seatstays/triangle thing behind the rear seatpost! On the other hand, when playing around with my cardboard & towels seat, my original plan of a banana-type seat on top of the rear tube was almost too low for me to pedal correctly. Because of the angles involved, each inch "up" was at least an extra inch "back" and I think (hope?) that my 108 degree slowriderz post will put me at the right spot...if not, that frame might get chopped a bit after all!

Also there is nothing saying that you can't pull the entire rear sprocket set up and flip the front one to the other side. Cool project.

I thought about that -- making it a six speed with an extra extra-long chain? I'm guessing side-to-side "chain line" wouldn't be an issue over that distance. Would I need an idler pulley on the drive side at that point, or would the derailleur spring be enough to take up any slack? It's kind of cool yet weird that there are currently TWO chains, but they thought an idler would be a good idea for the front one...which I think is a nice normal coaster-brake bike length of chain.

Just a guess, but I suspect you'll discover the chainrings are permanently attached to the cranks. You won't be able to easily remove one without the other. Did you have a plan to address that? As far as I know, the BBs are standard square-taper items, so parts are plentiful.

I really wish that a) I didn't live in Ohio, b) it wasn't December, and/or c) that I had a heated garage! Right now it's about 30 degrees (or -1C) and the gray skies are trying to snow, which means my already-questionable bike mechanic skills become even more diminished:

"Wow, it's colder out here than I thought it was. Aren't these three piece cranks? I thought they were when I glanced at them the first time but I was busy messing with seat ideas, so I didn't really look at the cranks very closely...SNOW?! Oh, for cryin' out loud. Well, they LOOK like three-piece cranks...or maybe they're just cleverly forged to LOOK like...oh great, now wind? I should have brought a coat -- this is not 'sweatshirt weather.' At least I thought to bring a magnifying glass out here, right? Well, each side has a tiny little crack or airspace all the way around between the crank and the 'spider'...and those questionable-looking hex bolts attaching the chainring to the spider really do seem to be bolts! They don't look like steel, though, more like alloy -- that's kind of weird."

"Where's my socket set? Maybe I can just pop off one of those cranks fast and oh there's the wind again. I should go inside and get a real coat...and some gloves...maybe a hat...it's supposed to get up to 52 F (11 C) next week, right? Yeah, let's wait until then to take this apart...or maybe until April. I won't be RIDING until then, so...."

And yes, I realize that by February, when it's REALLY cold, this weather will feel like sweatshirt weather!

Anyhow, if all else fails, I could theoretically just go with a different, similarly sized double or triple chainring (minus cranks) from another bike, right?

Still, the question about the cranks has me thinking again about "never going back to stock" -- what would happen if I just pulled the entire rear crank/chainring assembly and moved it to the front bottom bracket, along with the front derailleur? The good news is that with all that extra chain, the angles of the "chain line" would be reduced. If I DID need an idler pulley with that setup, though, would it handle the chain's side-to-side motion?

This is what I love about rat roddin' and this website -- there's a lot of "on-the-fly engineering" and projects are almost guaranteed to change between conception and completion!

 

[RustySprockets]

I'm not sure you follow what I was saying, but you will...once you remove the crank assemblies and examine them. The crank arm & spider are typically not separate items, they're fused...and the chainrings are attached at the spider, not the BB spindle. When you remove those offending crank arms, everything else comes along for the ride.

 

[Raoul Dude]

I'm not sure you follow what I was saying, but you will...once you remove the crank assemblies and examine them. The crank arm & spider are typically not separate items, they're fused...and the chainrings are attached at the spider, not the BB spindle. When you remove those offending crank arms, everything else comes along for the ride.

Well, darn. Now I know what you mean by "fused."

I thought I was following you before. I think I was secretly HOPING -- based upon what my eyes were telling me -- that you might have been wrong! (I probably shouldn't have even hoped for that -- I've never worked on a bike like this before.)

Based on the seam/gap/crack between the crank and the spider, I was hoping that the crank wasn't connected. "How could it be? It doesn't look like it's forged as one piece!"

<cue evil laugh and ominous music>



I found my coat, a flashlight, my socket set, a hat, and not long after, the whole assembly came off as one piece -- and once I took it off the chain, I immediately saw what you were talking about!

"What do they do at the factory? Put the crank through the spider and then press it or hit it with a die to make a...a flange so it doesn't pull back through?" (Is there a more correct term than "flange?")



Now that I have a more accurate idea of what's going on here (and what's NOT easily coming off in the pictures above!) what should be the next most logical step? Try to find a double or triple chainring that's not connected to a crank and slap it on there, and find a single chainring for the left side? View this as an opportunity to re-reroute the chain(s) and possibly the front derailleur, which would probably be the coolest-looking and most-factory-looking solution? The laziest and most easily reversible solution seems to be "just take the pedals off the back cranks and call it a day."

Thanks for all the help and advice so far, and sorry that I didn't quite "get" what was going on here 'till I started taking it apart!

 

[deorman]

The crank arm is what mounts the sprocket to the crank shaft. You could cut most of it off and just leave the center. You could move the synch chain to the same side as the drive chain. Since no one else will be pedaling, it doesn't have to be the same size, but that would affect your gear ratios.

 

[Raoul Dude]

The crank arm is what mounts the sprocket to the crank shaft.

That's what I'm seeing, now that I'm Googling and (re-)learning what I'm talking about! I knew I'd seen some older (apparently BMX) three-piece cranks in the past that didn't include a chainring, so that led me down a path of increasingly incorrect logical leaps that I won't even try to explain here.

You could cut most of it off and just leave the center.

That's an idea I was wondering about -- I've got two donor mountain bikes with decent drivetrains. "Maybe I could Dremel off the crank from each chainring, and grind it down the cut until it's smooth and doesn't look like I took a hacksaw to it?" Then if I took off the inner chainrings from the left side I'd be in business, and from what I can tell the number of teeth on the new chainrings won't be that critical to the bike's operation, only its final gear ratio. (At a quick glance, both seem to have large rings the size of the current "middle", a middle the size of the current "small", and then a really small inner ring. The top speed will go down, but with only one person pedalling I probably wasn't going to use the big chainring that much anyhow, right?)

 

[RustySprockets]

Sorry if I was being a stick-in-the-mud, but I wanted you to understand the task you were facing. Crank elimination won't be quite as simple as blotting it out using Photoshop. Insurmountable? Hardly...but it's a chore best attacked with a plan in mind.

 

[RustySprockets]

Perhaps the easiest and most elegant solution is just to remove the tandem parts for safe keeping and replace them with a standard donor crank at the forward bottom bracket. Yes, that does make for one incredibly long (and floppy) chain, but if it works...great! If it doesn't, at least you can return things to the way they were without any permanent damage.

 

[Raoul Dude]

Nah, you weren't being a stick-in-the-mud at all! I figured that I was in for a bit of a project, which is exactly why I was asking "what else am I missing?" in the first post up there.

Right now I THINK my new plan of attack will be based on your last suggestion:

1) As you suggested, I can take the tandem parts of the drivetrain off the bike and put them in a box. If I put some sort of donor crank on the front bottom bracket I can see how it rides and shifts at the rear with a really, really long chain.

1) a) Depending on what I use for a crank, I'll leave the front derailleur where it is until I see how it rides and shifts. If I wind up with a multispeed donor crank, I can always move the chain between rings manually while testing, and if it still works well, I can move the front derailleur forward at that point -- if I even need one!

2) If the above plans don't work, I MIGHT want to experiment with an aftermarket idler pulley, since the stock one is attached to a tab welded to the frame on the left side....

3) ...and if aftermarket idlers are expensive and/or hard to find, at that point I might want to experiment with a setup similar to what I've got now with two chains and two modified donor cranks.

Do those sound like workable ideas? Do I perhaps have #2 and #3 in the wrong order?

Ten minutes with Google suggests that TANDEM idler pulleys aren't common and aren't very cheap, but MOTORIZED bicycle idler pulleys are more common and not nearly as expensive. Maybe those would be an option, or perhaps I could make one myself from an old rear derailleur jockey wheel? (I realize that those last two ideas SOUND a lot easier than they might be in reality -- and have NO idea what I might be getting into there, either.)

I have to say, it's kind of nice being able to do my "information gathering" now, kind of in advance of when I'll actually be doing the work, rather than when I'm covered in grease and pulling my hair out!

 

[RustySprockets]

I certainly agree with the cautious approach in step one--steps two and three are predicated on the outcome, so stay positive. I expect it will be functional, with only the rear tensioner and no pulleys, but the chain slop may prove irritating.

 

[deorman]

Pulleys can be sourced from trashed MTB derailleurs, the trick is the mounting point.

 

[Raoul Dude]

I expect it will be functional, with only the rear tensioner and no pulleys, but the chain slop may prove irritating.

There's only one way to find out, and that's going to be with extensive testing, probably when the weather gets warmer! I'm not a big fan of cold-weather riding, but this project might just drag me into it. "It's not THAT cold...and I won't be going as fast as on a road bike, after all...."

Pulleys can be sourced from trashed MTB derailleurs, the trick is the mounting point.

That's kind of what I was thinking, too. The pulley wheel and the axle screw should be fairly easy -- the homemade mounting bracket(s) and figuring out the perfect "sweet spot" for the mounting location would be the hard parts.

I'll keep asking questions and gathering information here, and when I actually get to the wrenching and testing phases I'll post a link to an actual "build thread."

Thanks for all the advice and suggestions so far!

 

[aka_locojoe]

If you don't go the direction you are planning it might make a great cargo bike with some sort of long rack in the rear section.

 

[RustySprockets]

If nothing else, that cargo bike answers the question about using a very, very long chain.

 

[Raoul Dude]

If you don't go the direction you are planning it might make a great cargo bike with some sort of long rack in the rear section.

Indeed it might, and I think that's going to be my first "backup plan" if the first plan doesn't work out! I first thought of that when I saw this thread and some of the cool results: http://ratrodbikes.com/forum/index.php?threads/tandem-to-single-rider-conversions.85823/

If nothing else, that cargo bike answers the question about using a very, very long chain.

I think it answers one but might lead to a few more, like "how is that extra length going to affect the rear derailleur shifting?"

The current half-baked plan is to take a Dremel to my new old stock eBay triple cranks and just grind the crankarms off. (You've got to love eBay -- where else can you find someone selling four identical right-side Sakae mountain triple chainring cranks, without the left-side crank to match?) They fit the spindles correctly, and IF I'm remembering right, they're only two teeth per ring smaller than the stock (rear) right-side crank. At a quick glance on a cold day, the middle (rear) chainring on the left looked like it was in line with the left front chainring, but I'll need to mess around with the idler pulley some more or adjust the length of the chain.

 

[Raoul Dude]

...and when I actually get to the wrenching and testing phases I'll post a link to an actual "build thread."

Now all in one place over in the "Builds" section: http://ratrodbikes.com/forum/index.php?threads/non-vintage-tandem-into-stretch-cruiser.91010/

I need to post a few more pictures when I finally get all the pieces painted, but I'd say the work on that thread -- AND the bike itself -- are both about 90% finished. Thanks to everybody for all the help and information!