smoothie_biker

I am interested in using half-link as well. It is about 1mm short when replacing a full-link with half-link. I will wait till the chain stretches out a little more and add half-link.

Bezalel

There's always the Trickstuff Exzentriker or the Phil Wood Philcentric. You can eliminate the need for a half link by changing timing rings.

zonatandem

Any bicycle swap meets in your area?
Here in Tucson we have 2 big bike swap meets a year and there always 2 to 6 usable tandem for sale.
And yes, swap meet prices are negotiable.
Have sold several tandem there through the years from older Co-Motion, custom Colin Laing, Burley, Velo Schauff and Santana . . . priced from 300 to 1,200 dollars.

smoothie_biker

Changing to different ring size? This Giordano comes with 40-tooth timing chainrings.

Bezalel

For each tooth you add or remove from the timing rings, your chain is adjusted by a half link. That means that if you need a half link with 40 teeth, any setup with an even number of teeth will require a half link and any setup with an odd number of teeth will not. This is important to note when using eccentrics that mount in a 1.375" shell because they don't have enough capacity to take up a full link.

smoothie_biker

Thanks, Bezalel. It all makes sense to me now. So, there is still a possibility that I can run the timing chain without the tensioner on this cheapo tandem frame. I tried 42T front/40T Rear combination without using a half link and I was able to put the captain crank back on even though the chain is a little tight. I am thinking a 39T/39T combo and removing a full link from the chain should also work (Or 40T/40T combo with a full link removed and add a half link back). The trick is to connect the chain first, put chain over chainring and insert crank arm onto the spindle. The chain tension will be really tight at first but should loosen up as it starts to stretch.

Bezalel

No, the timing chain shouldn't be under tension. It should be at almost no slack.

bkgeig

If you haven't seen Sheldon Brown's article on chainring centering, I suggest you look at the updated version here: https://velowoodcyclery.wordpress.co...g-a-chainring/ I'm pretty sure the concept applies to tandems just as ss and fixies. Your chain might be overly tight during one part of its rotation and looser at others. Evening out tension might help you run without a tensioner. I don't think you want too much tension on that chain as that puts stress on the bearings. I would actually run as loose as I could without having the chain jump the rings.

smoothie_biker

I've been running the timing chain without a tensioner. It just feels sloppy with so much slack between coasting and pedaling but it works.

smoothie_biker

Just want to update: half-link works like a charm. No tensioner needed and chain tension is about right.


half-link and master link

qspencer

Now you can save some more weight by taking a hacksaw to the tensioner mount!

smoothie_biker

Good idea!! I wonder if hacking it away and filing to smooth out the joint could weaken the area.

twocicle

That's great you got it running without an eccentric or tensioner. At one point a couple years ago, I also used a half link to get the crank phase set just right. Those do come in handy with timing chains.

Did you guys ever try using a single speed tensioner?

I've seen $10k 1x11 (single chainring) mtn bikes have some form of tensioner, so one would presume that implementation is not all that bad. Google "bike chain tensioner single speed" to see all kinds, from rear derailleur types, to more custom swing arms and mounts up front by the chainring. Adapting one for your mid point hanger should be simple.

Some examples:


In fact, seeing these on single speed and single chainring bikes out there on really high end setups, it does make me curious about doing away with eccentrics entirely on tandems. Who knows, maybe some of these implementations could also be used with Gates Belts to adjust for slight length differences in bottom tube/BB spacings.

twocicle

Hey Leland,

Can you share more specifics of what qualifies the "tandem" forks Santana uses vs. what you are calling "single bike" forks?

Also, what certifications (and in which usage categories) do those Santana forks have?

Leisesturm

Timing rings must always be the same size. Just wanted to get that out the way. And the half link is only going to work for so long. Then what? IMO buying a cheapo tandem isn't the issue. Buying a cheapo tandem as the foundation of an entry level build is an issue. It doesn't work. You get the feel good endorphins from all that sweat equity but really... for the cash outlay there is definitely a much better bike that could be purchased stock from a dealer. What does a Fuji Absolute retail for? Our Raleigh Coupe would have been ideal but it is no longer made. Ours came stock with mechanical Avid BB7's with 160mm rotors btw and in 8 years of riding we haven't found them deficient. Truth be told the o.p. does not even need disks.

When we wanted a commute tandem and grocery getter we got the Kent DualDrive (Pacific Crest) and made minimal upgrades. Over several years we have made additional upgrades but we avoid making those upgrades that would put us in the next higher price point without a performance increase. If the Giordano had existed when we were looking we would have bought it and changed nothing!! Maybe the saddles. Possibly the pedals. Forte (Performance Bike) cage pedals $14/pr. FowerGrips cinching toe straps $16/pr. If you really need to get your hands dirty buy a frame from Nashbar or Chuck's Bikes and wrench to your hearts content. JMO.

H

Team Fab

You could use a floating ring to tighten the chain as well.

There have been other threads on this.

bkgeig

Glad to see the half-link worked. I wouldn't remove the bracket; it doesn't add that much weight and might be useful down the road. Another ss tensioner option might be the Blackspire Stinger, if you're running an external bb front crankset. I've seen folks run it in reverse, i.e. pushing down instead of pulling up.

I've been traveling for work and waiting for parts to arrive. Looks like the wheels and headset should arrive today. Yippee! This build changed directions when I discovered a 185mm BB5 mtb brake and an old Avid v-brake in a garage cabinet. Looks like I'll be running mechanical disc in the back and v in the front. This will allow me to install some cyclocross levers I have lying around. On my commuter I find I use the cross brakes almost as much as the road levers.

I picked up on Ebay a Bontrager road crankset and Bontrager tandem arm, both $35 each shipped. I bought an ISIS bb from Nashbar for $30. $100 total seemed reasonable to me. They'll go in the rear. Haven't decided on the front yet. I have an old square taper crankset I might run in reverse. On the other hand I see front cranksets on Ebay for about $100. Might use the funds I had dedicated to brakes for a new front crankset. I'll update the expenses sheet later this week.

bkgeig

Twocicle, as you probably know Gates belts require both quite a bit of tension and a specific amount, measured by an app they provide. I doubt most ss tensioners could do both, and hold that tension reliably over many miles. All the Gates systems I've seen have been tensioned by an eccentric bb or sliding dropout.

If I were to run a Gates in this application I would probably use the existing bracket tensioner and set it up like you would a tensioner on an automotive AC compressor. If fact you might grab a tensioner wheel from a scrap yard car to replace the existing jockey wheel. Then, like an AC compressor, you could use a bolt to press the tensioner wheel down on the belt until the app indicated the correct tension and finally tighten the top and side bolts to keep it in place.

I think I'll stick with a chain.

Smoothie_biker, if you're going to replace a chainring anyway, you might take a look at the narrow-wide rings now available for 1x drivetrains. They won't help with tension of course, but they would probably help to secure a slightly loose chain. My understanding is that all derailleur chains are 3/32" inner width, but the external width varies by speed, with 11 being the narrowest. So I think the stock Giordano chain should work with a narrow-wide ring, or replacing it with a 3/32" shouldn't be too expensive.

LelandJT

Our forks are made only for us to our specifications. We use a 1 1/4" steerer tube and thicker walls throughout than single bike forks. Our engineer has calculated the loads he expects a tandem fork to see and designed around those. He supplies his calculations to an independent laboratory to test our forks and others. Their testing has shown that no single bike forks are safe enough for us to sell on our bikes. We don't want to be sued by an injured customer so our standards are higher than others'. These standards and tests are all designed by us so there are no official certifications. Other tandem companies don't seem interested in the results so there's no demand for an industry wide standard for tandem forks. They've even ignored our warnings about specific forks they spec that have failed our tests.

Basically, when exposed to the higher loads we expect a tandem to exert our forks last many more cycles than single bike forks we've tested and at least one fork I'm aware of that is used by a different tandem company.

twocicle

The idea of using a tensioner pulley system was directed at either chain or belt usage possibilities.

BTW, the Gates CenterTrack belt is not so particular to needing high tension or a specific amount. I've experimented with much lower tension than spec and have not had any negative issues. On the contrary, lower belt tension seems to provide less crank rotation resistance, plus it puts less load on BB bearings so we are saving there too. Using lower tension might require a stiffer tandem frame which can provide a more consistent tension, so higher tension (to spec) might be necessary otherwise.

twocicle

If a fork is overbuilt as a means to encapsulate the highest anticipated tandem load (eg: 450lb team + 100lb touring gear), then yes you may indeed have a stronger fork to market. Intended usage targeting may have valid limitations and should not be misrepresented as deficiencies. For example, my single road race bike fork would not last long at all on CX course even with the same rider load. That is a simplified example, but just to demonstrate a point. In most cases, one-size-fits-all products are not optimal for all usages.

I would definitely be interested to see testing results Santana may have for a ENVE 1.5" tapered road fork. That ENVE fork is quite beefy when I compare it to a 1.5" tapered 3T Rigida road fork (3T product manager assured me they know of tandems using this fork and no issues). Regardless, due to it's lightweight build I might still hesitate to recommend the 3T fork to many tandem teams, as I would not be comfortable using it with higher team loads or over very rough (cobble) surfaces. On the other hand, the ENVE fork seems very solid.

Recalling when Bill McC. touted the vast increase in capacity between a 1 1/8" fork crown/tube vs. the Santana spec'd the 1 1/4" steerer. That was a 1/8" diameter upgrade. Even many single road bikes are using 1 3/8" tapered steer tubes. What of comparing 1.5" tapered forks to the smaller 1 1/4" Santana forks? Is there an explanation of why a 1.5" is not preferable for tandems?

bkgeig

Bunch of parts arrived at the end of the week and I had time this weekend to install them. It's starting to look like a bike again. I got the Inverno wheels from NiagraCycles. I didn't notice when I ordered them that they are schraeder drilled. Fortunately I had a couple of presta adapters already.



I had to put a couple of nylon spacers on the calipers to get them out far enough from the rotors. I still have some tweaking to do on the disk setup.





Bought some new pads for the front brakes. Will probably buy a new noodle too.



Following a suggestion I saw online, I ran standard brake cable from the levers to the cross levers. I'll run compressionless from the cross to the brakes. I modified the levers with a dremel to ease the curve of the housing out of lever.





The pricing sheet is updated. I'm just under $900, including the $40 I got from selling the Giordano wheels. I still have more parts to sell. I haven't included small parts like cable and brake pads, which will probably total around $50 by the time I'm done. Looks like the new fork and rear crankset have saved over 2lbs from the originals. The wheels were about the same weight, though the Inverno feel heftier.

The rear derailleur is an old XT I had already. The captain's saddle is also something I had; it's light but also hard. Might replace it eventually if it's too hard. The Giordano saddle went on the 26er mtb I building up as a spare.

The handlebars are 44cm ergo, what I use on both my commuter and road bikes. I couldn't stand the 40cm that came with the bike. I had a 26.0 stem already. Fortunately JensonUSA had some 26.0 handlebars. I've included them in the cost list, though I probably would have upgraded any bike to 44cm ergo.

WheelsNT

Tandems can generate more heat in braking than single bikes. People sometimes melt the plastic pad adjusters on disk brakes on steeper downhills. The failure mode for that isn't too bad since the adjuster usually doesn't move once it melts. But if you melt your nylon spacers, the caliper will move out of proper orientation with the rotor, and the brake probably won't work like it is supposed to. A steep downhill would be a bad time to find out. My $0.02, I'd find some metal spacers.

bkgeig

Great suggestion. Thanks. I'll replace the nylon spacers with metal when I get back to work on the brakes. Gonna have to take a couple of weeks off from working on the tandem to finish up some house and car projects.

twocicle

FYI: besides the melting nylon/plastic issue, you would want a 100% solid, flat metal washer that will retain the alignment angles.

Also, assume you used the Road BB7 disc caliper and not Mtn, and not sure what the cable pull required for your front canti brakes will be. If either are mtn versions, you need a travel agent to increase cable pull?