Advertise on Bikeforums.net



User Tag List

Results 1 to 16 of 16
  1. #1
    Tinkerer since 1980 TheBrick's Avatar
    Join Date
    Sep 2006
    Location
    London
    My Bikes
    Coppi racer, Old school BMX, some random a fixed wheel convertion
    Posts
    922
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Mechanical quetions. Long sorry

    Hello all, I have been considering getting a tandem for my other half and I, but you have guessed it, I have some questions that I would like some help with. I have been looking at different options am thinking of buying secondhand, but don't know enough so my first set of questions are mainly mechanical. I have reasonable level of mechanical knowledge (I have been building up bikes since I was a teenager, I can build wheels, paint frames, but of course I only have knowledge about bike I have worked on) but I do not keep up with the trends of the latest group sets e.t.c

    I shall start at the front.

    1. Front I guess is standard, just well built.

    2. Headset. I notice on Sheldon's site that 1 1/4” headset are used on tandems. Is this standard or just some manufactures like it.

    3. Chain rings. The left hand side with the pacers chain is straight, so do these chain rings tend to be single speed rings. If not why not. What size chain do they tend to run 1/8” or 3/32”? These chain rings seem to be the same size from what I can tell. If the two people have different optimum cadence do people some times gear the chain rings to allow from this. I realize this will mean that the pedals will go in and out of sync as you go along, does this matter? Would that make it harder to ride?
    At the back do people tend to run road triples to get good high gears even on mbt tandems

    4. Bottom brackets. Eccentric bottom brackets seemed to be used to adjust the tension on the sync chain. Is this always the case. Should tandems without and eccentric bottom bracket be avoided? Do normal bottom brackets fit with in a special removable eccentric shell, with in an over sized bottom bracket shell or is the bottom bracket a complete unit with in an over sized b.b. shell, or are they special b.b which fit in a standard iso sized b.b shell? I presume the rear b.b is standard iso.

    5. Rear hub. I have herd that tandems have extra wide spaced hubs to reduce dishing, again is this true of all tandems, or are many on a 135 mm mbt spacing.

    6. Brakes. Clearly you need good ones, I read a bit about drag brakes, are these common? Are they expensive?

    7. Material. Should alu frames be avoided at the lower end of the market? Or is it all fine.

    8. Any other mechanical things I should look out for when buying a second hand tandem, things to avoid in terms of design e.t.c?

    Lastly any useful tandem storage tips? They are big after all.

    Sorry for the long list.

    Many Thanks

    T
    Travelling without inertia

    London's single speed and fixed gear forum

    http://www.londonfgss.com/

    Lets make this happen.

  2. #2
    hors category TandemGeek's Avatar
    Join Date
    Jan 2002
    Posts
    7,151
    Mentioned
    0 Post(s)
    Tagged
    1 Thread(s)
    1. Front I guess is standard, just well built: If “front” means frame or fork, both are tandem-specific items. A single-bike fork is usually inadequate for most average size / weight tandem teams.

    2. Headset: This is unique to Santana who jumped on the Evolution-Size headset well back in the early 90’s. Most all other builders use 1.125”(1 1/8”). Longbikes may have used it on a few of their tandems as well during their early, short production run.

    3. Chain rings: Any pair of chainrings will work, regardless of size or tooth count so long as they both have the same number of teeth. Any width chain can be used as long as it is compatible with the chainrings, there’s even a couple in Florida who have been experimenting with a belt-driven sync drive. Using different size timing rings is not recommended as the captain would be unable to anticipate the crank positions when entering a corner. Triples are common on all but full-on racing tandems and “cruisers”.

    4. Bottom brackets: Eccentrics are the most common, although cheap department store bikes will sometimes use an idler-wheel as a tension adjuster as was done on the first tandems back in the late 1800s. With the exception of Burley’s pressed-in bottom brackets, most all other tandems use standard bottom brackets for both the captain and stoker position(s). Eccentrics come in a variety of different designs as specified by their builders and, as such, are in essence part of the frame and not usually interchangeable between brands or builders unless the builders happen to use a Bushnell eccentric bottom bracket, e.g., Ventana, daVinci, Boulder, AriZona, Bushnell, Erickson, Rodriquez, and several other builders use the Bushnell eccentric.

    5. Rear hub: Tandems come with 135mm, 140mm, 145mm, 150mm and 160mm rear spacing, with 145mm being the most common design standard. Several off-road tandem builders use 135mm spacing to mitigate wheel and disc compatibility issues without much of a durability problem. 160mm is a standard that is fairly unique to Santana. All of them work fairly well so long as the wheels components are suitable for the size and weight of the tandem team that will use them and the wheel builder knows how to build wheels for tandems.

    6. Brakes: Arai drag brakes are fairly common, although quite a few teams that own one don't install it unless they expect it will be needed for a trip or challenging terrain. Cost can range from $90 - $160 (USD) for a “kit” or as a factory-added option. Arai drums require a left-hand threaded rear-hub which for many years was the “default” on most tandems.

    7. Material: Aluminum is fine. It’s cheaply-made aluminum and steel tandems (tandem-shaped objects, if you will) that should be avoided for all but “family-fun rides” and other light-duty use.

    8. Any other mechanical things I should look out for when buying a second hand tandem, things to avoid in terms of design e.t.c: Stick with recognizable brand names with components that are still supported and you should be fine. More info on buying used tandems is here.. http://www.thetandemlink.com/usedhome.html
    Last edited by TandemGeek; 02-21-07 at 10:32 AM.

  3. #3
    Tinkerer since 1980 TheBrick's Avatar
    Join Date
    Sep 2006
    Location
    London
    My Bikes
    Coppi racer, Old school BMX, some random a fixed wheel convertion
    Posts
    922
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thanks top notch comprehenive answers. Good to know the specific tandem technology.
    Travelling without inertia

    London's single speed and fixed gear forum

    http://www.londonfgss.com/

    Lets make this happen.

  4. #4
    Cyclist- Bike 'n a half
    Join Date
    Feb 2006
    Location
    Orlando, FL
    My Bikes
    Custom S & S Bushnell Tandem, Eddy Merckx Ti
    Posts
    257
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by TandemGeek
    there’s even a couple in Florida who have been experimenting with a belt-driven sync drive.
    They are old friends from my single bike start in Fort Lauderdale area and a positive influence / mentors on our taking up tandem riding.

    The last I heard was that the experiment was conclusively positive. The minor increase in friction is overcome by efficiencies in lower spinning weight / mass. Maintainence is reduced / eliminated due to the no-stretch characteristic of the Kevlar reinforced belt, no more eccentic adjustments.

    No word yet on how, what, where, when, they might bring this to market, but I would definitely give it a try if they get it going.

  5. #5
    hors category TandemGeek's Avatar
    Join Date
    Jan 2002
    Posts
    7,151
    Mentioned
    0 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by regomatic
    They are old friends from my single bike start in Fort Lauderdale area and a positive influence / mentors on our taking up tandem riding.
    We'll be seeing Bob & Jan again before too long. They are truly delightful folks to be with.

  6. #6
    Senior Member zonatandem's Avatar
    Join Date
    Dec 2003
    Location
    Tucson, AZ
    My Bikes
    ariZona carbon fiber tandem & single
    Posts
    9,968
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Know of other folks who are/have experimented with belt drive sync on tandems.

  7. #7
    Senior Member Jinker's Avatar
    Join Date
    Nov 2005
    Location
    Ottawa,ON
    My Bikes
    Univega Via Montega, Nashbar Aluminum frame/105 roadbike
    Posts
    642
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Noone has any pics of the belt systems, do they? Are these fairly narrow belts? Toothed belt?

    I'm just having trouble picturing a sturdy enough belt not resulting in a really large q-factor, but I'm not up on my kevlar reinforced belt technology, so maybe I'm overestimating how wide the system would need to be.

  8. #8
    hors category TandemGeek's Avatar
    Join Date
    Jan 2002
    Posts
    7,151
    Mentioned
    0 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by Jinker
    Noone has any pics of the belt systems, do they? Are these fairly narrow belts? Toothed belt?
    Not a good one. I've attached a small, cropped section of a photo where you can see the belt drive and front pulley on Bob & Jan's tandem taken at GTR last year. I had thought there was a better photo somewhere but I couldn't find it.

    Here's a link to a thread where we discussed the belt last year about this time: Timing belt in stead of chain

    As best as I can recall, the HTD (high torque drive) belt Bob spec'd for his design is about 5/8" wide and the custom-made pulleys are relatively small in diameter; equivalent to perhaps a 28T chain ring. It was a slick looking set-up and in discussing its use with Bob they've had excellent results with it which is to say no belt slips or deraillings in a wide range of temperature, weather, and terrain conditions.

    From a maintenance standpoint, hands-down it is far-superior to a chain for a road tandem. Long-lasting and no lubricants so no grime and the HTD belt design doesn't require large amounts of pre-load tension so the existing bottom bracket design is more than adequate. Off-road would be a bit different as you tend to collect sticks and other debris that the chain & sprockets cut through which might pose a problem to a wider belt and it's pulleys.

    As for efficiency, I still don't believe the HTD belt is as efficient as a chain, but the difference can be pretty small, i.e., an HTD belt drive can be about 95% efficient whereas well-maintained chain drives are closer to 98%. That seemed to be about right based on my inspection of Bob's system as there was demonstrably more drag than a properly adjusted sync chain, but it was about equal to a tandem where the sync chain was too tight.

    As to weight, I would have liked to have compared the weight of his pulleys and belt to our daVinci's 1.2lb 34t timing rings & 80" / 160 link sync chain. The sync chain itself accounts for 97% of the weight (438g) with each of the 34t chain rings coming in at 73g. I think they would be comparable vs. a conventional cross-over crankset's timing cranks with the added mass of the spiders, larger chain rings, and stackbolts.
    Attached Images Attached Images
    Last edited by TandemGeek; 02-23-07 at 06:21 AM.

  9. #9
    Senior Member zonatandem's Avatar
    Join Date
    Dec 2003
    Location
    Tucson, AZ
    My Bikes
    ariZona carbon fiber tandem & single
    Posts
    9,968
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    The experimental sync belt drive system we saw was toothed. The Italians also have experimented with belt drive on single bikes.

  10. #10
    Senior Member zonatandem's Avatar
    Join Date
    Dec 2003
    Location
    Tucson, AZ
    My Bikes
    ariZona carbon fiber tandem & single
    Posts
    9,968
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Belt drive on the Ixi single folding bicycle.
    Attached Images Attached Images

  11. #11
    Tinkerer since 1980 TheBrick's Avatar
    Join Date
    Sep 2006
    Location
    London
    My Bikes
    Coppi racer, Old school BMX, some random a fixed wheel convertion
    Posts
    922
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Tandemgeek
    ...Using different size timing rings is not recommended as the captain would be unable to anticipate the crank positions when entering a corner...
    I have been thinking about this. What you say is true but this is the same problem if you ride fixed gear. You just have to make sure that you are going slow enough around tight bends so that you do not have pedel strike. I know Sheldon has a fixed gear tandem and from his web site loves it. So with this in mind if / when I find a tandem I may try diffrent size timming chainrings. Has anyone else experimented?
    Travelling without inertia

    London's single speed and fixed gear forum

    http://www.londonfgss.com/

    Lets make this happen.

  12. #12
    hors category TandemGeek's Avatar
    Join Date
    Jan 2002
    Posts
    7,151
    Mentioned
    0 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by TheBrick
    What you say is true but this is the same problem if you ride fixed gear. You just have to make sure that you are going slow enough around tight bends so that you do not have pedel strike. I know Sheldon has a fixed gear tandem and from his web site loves it.
    It so happens that I do ride a fixed gear in the winter so, yes, I understand how to negotiate turns with a set of fixed cranks, e.g., you slow the hell up before entering a tight corner.

    The same would apply for fixed gear tandem and what makes the fixed gear tandem safer is the fact that you as the captain are immediately reminded that you must carefully negotiate tight turns when you realize you can't coast.

    With a geared tandem & freewheeling hub, my concern would be that unless you routinely ride a fixed gear personal bike and have this cornering technique burned into your mind, you are apt to enter corners as you would on your geared bike (coasting with your inside pedal up) with a 1 out of 4 chance of bashing your stoker's pedal/foot/cranks into the ground. While it's possible that you and your stoker could "negotiate" pedal position as you approach the corner to find a neutral position, unless the majority of your rides were on long straight segments of road devoid of tighter radius turns, you could find yourselves doing a lot of negotiating.

    Don't let me stop you or anyone from experimenting... just be mindful that clipping a pedal on a tandem ain't like clipping a pedal on a single bike: you're driving a lot more weight and force into the point of impact with the expected results of a harder strike, e.g., damaged equipment, possible loss of rear wheel grip, and a really upset stoker.

  13. #13
    Tinkerer since 1980 TheBrick's Avatar
    Join Date
    Sep 2006
    Location
    London
    My Bikes
    Coppi racer, Old school BMX, some random a fixed wheel convertion
    Posts
    922
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Sorry I did not mean it in a rude manor.

    That is a very good point tandemgeek. Your name serves you well . We being human and iherantly lazzy are less likly to think about pedal strike because it is not fixed. I am not planning on running before I can walk but I like to play with these ideas in my mind even if they go no further. I will be sticking with a standard setup I think. Back to searching ebay .

    edit: Yep got to keep the stoker happy as it will be my grilfriend, too much at stake to be doing anything crazy. I'll keep the risk taking to putting my own ass on the line and no one elses
    Last edited by TheBrick; 03-05-07 at 10:28 AM.
    Travelling without inertia

    London's single speed and fixed gear forum

    http://www.londonfgss.com/

    Lets make this happen.

  14. #14
    hors category TandemGeek's Avatar
    Join Date
    Jan 2002
    Posts
    7,151
    Mentioned
    0 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by TheBrick
    Sorry I did not mean it in a rude manor.
    No worries as it wasn't taken that way. I just thought I'd offer some additional context to frame my comments.

  15. #15
    Tinkerer since 1980 TheBrick's Avatar
    Join Date
    Sep 2006
    Location
    London
    My Bikes
    Coppi racer, Old school BMX, some random a fixed wheel convertion
    Posts
    922
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Cool.

    I have another question which I though I would add here to save starting a new thread.

    Has anyone tried a suspension seat post for the stoker? I have never tried one on any bike but wondered if they where any good and if it was a good idea. I understand that as a captin if you see a bump you should comunicate it to allow the stoker to brace but some bumps are unexpected. I know when riding solo bumps in the road are one of the things that my girlfriend gets caught out on and finds uncomfy.
    Travelling without inertia

    London's single speed and fixed gear forum

    http://www.londonfgss.com/

    Lets make this happen.

  16. #16
    Senior Member
    Join Date
    Oct 2005
    Posts
    1,735
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by TheBrick
    Has anyone tried a suspension seat post for the stoker? I have never tried one on any bike but wondered if they where any good and if it was a good idea. I understand that as a captin if you see a bump you should comunicate it to allow the stoker to brace but some bumps are unexpected. I know when riding solo bumps in the road are one of the things that my girlfriend gets caught out on and finds uncomfy.
    Try these threads:
    Suspension Seat Posts
    Short Stoker Susp Seat Post
    New Susp Seat Post
    Thudbuster
    Tweak Setup

    There are more. Type whatever terms you want into the search function. It is not the best search engine but it will get you close.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •