Tandem from the ground up.
#1
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Tandem from the ground up.
Hi, My wife and I enjoy riding together and after riding an old Schwinn around a bit we have decided to build up a tandem for road riding.
I make bicycle frames for a living and have some of what I need to make build a tandem frame from 7005 aluminum. I don't care for the EBB solution for chain tension so I will make some type of tension or guide system. Mostly because of the time it takes me to position my saddle.
The strongest/largest head tube platform I have available in 7005 is a large 2" diameter tube to fit the 44mm cups (1-1/8 flush). I have cutters for onepointfive but no tube is available to accommodate those cups. A very large 65mm tube will be used for the down and boom tubes. I am not sure how much shaping I want to do on the boom tube (perhaps just shape the ends rectangular to fit BB shells) but the down tube will be bi-round and 75X50.
I am going to use paul brakes at the rims and a BB7 mounted to a triangulated seat stay (actually an MTB chainstay used as seat stays).
I have the front drawn to match my current road bike and stoker Lanie is short and likes an upright position so the back is 28"
The parts
Middleburn cranks
Paul brakes
29'r wheels (135)
BB7 dragger
Thomson stem/custom
3T bars
9 speed 105/XT
(proposed gears) 53/38/28
11/26 rear
proposed frame
tandem by frankthewelder, on Flickr
More pics as some progress is made. Thanks for lookin'
I make bicycle frames for a living and have some of what I need to make build a tandem frame from 7005 aluminum. I don't care for the EBB solution for chain tension so I will make some type of tension or guide system. Mostly because of the time it takes me to position my saddle.
The strongest/largest head tube platform I have available in 7005 is a large 2" diameter tube to fit the 44mm cups (1-1/8 flush). I have cutters for onepointfive but no tube is available to accommodate those cups. A very large 65mm tube will be used for the down and boom tubes. I am not sure how much shaping I want to do on the boom tube (perhaps just shape the ends rectangular to fit BB shells) but the down tube will be bi-round and 75X50.
I am going to use paul brakes at the rims and a BB7 mounted to a triangulated seat stay (actually an MTB chainstay used as seat stays).
I have the front drawn to match my current road bike and stoker Lanie is short and likes an upright position so the back is 28"
The parts
Middleburn cranks
Paul brakes
29'r wheels (135)
BB7 dragger
Thomson stem/custom
3T bars
9 speed 105/XT
(proposed gears) 53/38/28
11/26 rear
proposed frame
tandem by frankthewelder, on Flickr
More pics as some progress is made. Thanks for lookin'
#2
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I would reconsider the way your are planning to adjust the front chain, I have the Bushnell ECC on our new Calfee and it works great. I have had Santana's in the past and their system works fine also. Years ago I built some homemade tandems and tried a guide on the first one but on the second one I set it up so that the front BB slid back and forth for adjustment, it worked much better than the guide. Just my thoughts.
Wayne
Wayne
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Hi Frank;
A couple of suggestions:
* go 145mm at the rear - the hub is more expensive, but will last a lot longer.
* I think that you'll find that you want something lower than 28/26 if you do any major hills; make sure that you have the ability to do 28/34.
* which Paul brakes? https://www.paulcomp.com/brakes.html
* with respect to the boob/boom/bottom tube - make it as wide as you can; it is subject to lots of side to side bending loads, while the up-down loads are shared with other tubes in the frame. This should be the focus of your structure.
* the down tube does not need to be as stiff or as strong as the boob tube.
A couple of suggestions:
* go 145mm at the rear - the hub is more expensive, but will last a lot longer.
* I think that you'll find that you want something lower than 28/26 if you do any major hills; make sure that you have the ability to do 28/34.
* which Paul brakes? https://www.paulcomp.com/brakes.html
* with respect to the boob/boom/bottom tube - make it as wide as you can; it is subject to lots of side to side bending loads, while the up-down loads are shared with other tubes in the frame. This should be the focus of your structure.
* the down tube does not need to be as stiff or as strong as the boob tube.
#4
Likes to Ride Far
By saying "BB7 dragger" it sounds like you're planning to use it as a drag brake. That brake is not designed for that kind of use - you can use it in a normal way as a third brake, or otherwise get a proper drag brake.
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I would reconsider the way your are planning to adjust the front chain, I have the Bushnell ECC on our new Calfee and it works great. I have had Santana's in the past and their system works fine also. Years ago I built some homemade tandems and tried a guide on the first one but on the second one I set it up so that the front BB slid back and forth for adjustment, it worked much better than the guide. Just my thoughts.
Wayne
Wayne
H
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#7
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That sounds like a cool project. I wish I could weld.
Most tandem bikes look relatively similar. But they're always conversation pieces and fun to talk about in group event rides, etc. Since it doesn't sound like you and your wife plan to race it or anything, I think you should make it a little wilder than your drawing. Maybe some curved tubes to make some aesthetic flow or something. Have fun with it and have a conversation piece!
Most tandem bikes look relatively similar. But they're always conversation pieces and fun to talk about in group event rides, etc. Since it doesn't sound like you and your wife plan to race it or anything, I think you should make it a little wilder than your drawing. Maybe some curved tubes to make some aesthetic flow or something. Have fun with it and have a conversation piece!
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Make sure the stoker geometry will handle a suspension seat post just in case. Some teams are fine without, others swear by their Thudbuster.
#9
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Looks like a neat project. I would enjoy pictures as the project develops.
#10
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Another possible option . . .
No idler or eccentric is really required.
Chain stretch on crossover chainrings can be manipulated.
When chain loops more than necessary, replace 1/3 section of cross over chain with new chain, thereby eliminating the stretch part. May only need to be done once or less per year depending on annual mileage.
Or . . . when stretch occurs 'float' a chainring slightly larger than the crossover rings . . . makes for a great/interesting conversation piece.
Also concur with the 145mm spacing suggestion.
Suggest an adjustable stoker stem . . . amazingly my stoker after 30,000 miles on our present tandem wanted the bars brought in a tad closer.
Pedal on TWOgether!
Rudy nd Kay/zonatandem
No idler or eccentric is really required.
Chain stretch on crossover chainrings can be manipulated.
When chain loops more than necessary, replace 1/3 section of cross over chain with new chain, thereby eliminating the stretch part. May only need to be done once or less per year depending on annual mileage.
Or . . . when stretch occurs 'float' a chainring slightly larger than the crossover rings . . . makes for a great/interesting conversation piece.
Also concur with the 145mm spacing suggestion.
Suggest an adjustable stoker stem . . . amazingly my stoker after 30,000 miles on our present tandem wanted the bars brought in a tad closer.
Pedal on TWOgether!
Rudy nd Kay/zonatandem
#11
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Wow, tons of good information! I don't disagree with and of the proposed improvements and I appreciate your feedback. I have a lot of bikes and a lot of "some" parts to make frames with. here is sort of a run-down of other things with time and money mixed in. I personally get stoked on something and build it. I don't really have a "theme" or long term plan other than riding a road tandem soon. I have been building custom frames for 30 years, my system is DO IT NOW. Thinking about it is causing a lack of efficiency right now due to daydreaming. If I just do I will be fine and other things can get done.
EBB: 7005 tube is difficult to get and only available is some sizes. I don't really want to do all the tooling/set-up and programming required to make one frame component for a bike I may not even like and need to change.
drop spacing: can't get 7005 bar stock for a decent price and forged 7005 drops have sloppy tolerances and rounded corners that won't support high torque for a really long time. I also can't really budget a dedicated set of awesome tandem wheels to be able to ride this summer.
I love smooshing tubes so there will be a bit of that going on. I don't want to risk wasting tubes so courage may be a bit weak.. This had small diameter tubes so I could get very radical on this. This was all straight tubes to start. a 16" for a baby girl.
27 082 by frankthewelder, on Flickr
EBB: 7005 tube is difficult to get and only available is some sizes. I don't really want to do all the tooling/set-up and programming required to make one frame component for a bike I may not even like and need to change.
drop spacing: can't get 7005 bar stock for a decent price and forged 7005 drops have sloppy tolerances and rounded corners that won't support high torque for a really long time. I also can't really budget a dedicated set of awesome tandem wheels to be able to ride this summer.
I love smooshing tubes so there will be a bit of that going on. I don't want to risk wasting tubes so courage may be a bit weak.. This had small diameter tubes so I could get very radical on this. This was all straight tubes to start. a 16" for a baby girl.
27 082 by frankthewelder, on Flickr
Last edited by ftwelder; 06-30-11 at 05:38 AM.
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Hi, I made some progress and completed the frame today (unless I forgot something) I ended up sourcing a piece of extrusion that was perfect for the eccentric BB device so that was a plus. The first couple of pics are during the build process and then a couple with it "posing" across the street from my shop.
The down tube and boom tube are both 2-1/2" diameter. I flattened the boom tube to 2X3 and squared the ends to fit the BB shells. The down tube is bi-axial flattened with the ends squished to match the head tube and BB shell. The chainstays were made for tandem use but the sea stays are very thin butted chainstays.
Since the front seat tube has nothing bolted to it, I made it 1-1/2" in diameter (very oversized) with a 30.9 or 31.6 post (depending on what I ream it too) The headtube is 44mm. I think I kept the angles the same as the pic above but I made the head tube longer and the stoker seat tube shorter.
Enjoy the pics
28 002 by frankthewelder, on Flickr
28 004 by frankthewelder, on Flickr
28 003 by frankthewelder, on Flickr
28 001 by frankthewelder, on Flickr
28 014 by frankthewelder, on Flickr
28 011 by frankthewelder, on Flickr
The down tube and boom tube are both 2-1/2" diameter. I flattened the boom tube to 2X3 and squared the ends to fit the BB shells. The down tube is bi-axial flattened with the ends squished to match the head tube and BB shell. The chainstays were made for tandem use but the sea stays are very thin butted chainstays.
Since the front seat tube has nothing bolted to it, I made it 1-1/2" in diameter (very oversized) with a 30.9 or 31.6 post (depending on what I ream it too) The headtube is 44mm. I think I kept the angles the same as the pic above but I made the head tube longer and the stoker seat tube shorter.
Enjoy the pics
28 002 by frankthewelder, on Flickr
28 004 by frankthewelder, on Flickr
28 003 by frankthewelder, on Flickr
28 001 by frankthewelder, on Flickr
28 014 by frankthewelder, on Flickr
28 011 by frankthewelder, on Flickr
#13
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Lookin' good!
#14
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My main feeling here echoes a little the poster who mentioned curves and suchlike - but have a blast - this will be one tandem that will be seriously unique (they all are, but this is super special!).
Last edited by Mainframeguy; 08-13-11 at 08:36 PM.
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I'll second that - my stoker would never go back now she has a thudbuster - and the long travel one needs some serious space back there! Also I take it that 28" measure is the seat post to seat post along top tube - I just measured our 'dake, which is quite an old one and I believ reviewed as having a "cramped" stoker compartment maybe - and it is 28"... just thought I should mention that, but it all depends on stoker physique and preference I guess and I suspect you guys have trialed a few tandems so have a feel for that....
My main feeling here echoes a little the poster who mentioned curves and suchlike - but have a blast - this will be one tandem that will be seriously unique (they all are, but this is super special!).
My main feeling here echoes a little the poster who mentioned curves and suchlike - but have a blast - this will be one tandem that will be seriously unique (they all are, but this is super special!).
We didn't sample any tandems before building this one but I can tell you she wanted the bike to be small enough so she could "ring my neck" without getting off the bike (J/K) . Lanie is 5'3" tall. She also likes an upright riding position and prefers Northroad style handlebars on her bike. I am sure if this one is fun we will build a more serious machine in the future with several refinements. I purchased enough material for two frames. is 10.5 lbs in the ball park?
Thanks for the kind words!
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It looks like you have good clearance for fairly wide tires in back. With wide tires at lower pressures you can most likely use a regular seatpost rather than a thudbuster. Many hear run 25mm tires at 120+ psi and then require a seatpost.
Also consider a sprung Brooks saddle. It is a great option rather than a thudbuster seatpost. A Finesse womens single rail leather saddle with springs will save money and weight over a plastic saddle and thudbuster seatpost.
What are you using for a fork?
Wayne
Also consider a sprung Brooks saddle. It is a great option rather than a thudbuster seatpost. A Finesse womens single rail leather saddle with springs will save money and weight over a plastic saddle and thudbuster seatpost.
What are you using for a fork?
Wayne
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2000 Santana Arriva steel frame 8/5/8 tubing no headset or bottom brackets weighed 11 pounds. Lateral tube weighed 2 of that 11.
Wayne
Wayne
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I didn't have a target weight or any pre-conceptions at all except to build a fun bike! My best method is to do a minimum amount of research and discard or recycle the first few examples after I learn what could be made better. I made many assumptions regarding the amount of flexing that will take place and I am sure it would be very challenging to make a bike any stiffer than this one. Too stiff may be good while we struggle to learn to ride tandem.
I ended up with a lot of tire room for sure. The roads around here are in really bad shape and I am sure much of our time will be on the amazing remote dirt roads we have in the area.
I am leaning toward John Deere colors, green with yellow stickers.
I was thinking about just banging out a steel fork but someone in "framebuilders" suggested dual crown aluminum which would be really fun to make! (though it would take a long time)
Last edited by ftwelder; 08-15-11 at 04:39 AM.
#23
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That is a pretty impressive weight. There aren't many choices for aluminum materials these days but I am sure I could drop 500 grams or so with little effort.
I didn't have a target weight or any pre-conceptions at all except to build a fun bike! My best method is to do a minimum amount of research and discard or recycle the first few examples after I learn what could be made better. I made many assumptions regarding the amount of flexing that will take place and I am sure it would be very challenging to make a bike any stiffer than this one. Too stiff may be good while we struggle to learn to ride tandem.
I ended up with a lot of tire room for sure. The roads around here are in really bad shape and I am sure much of our time will be on the amazing remote dirt roads we have in the area.
I didn't have a target weight or any pre-conceptions at all except to build a fun bike! My best method is to do a minimum amount of research and discard or recycle the first few examples after I learn what could be made better. I made many assumptions regarding the amount of flexing that will take place and I am sure it would be very challenging to make a bike any stiffer than this one. Too stiff may be good while we struggle to learn to ride tandem.
I ended up with a lot of tire room for sure. The roads around here are in really bad shape and I am sure much of our time will be on the amazing remote dirt roads we have in the area.
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Thusbuster can be purchased with shims to make it fit almost any size seatpost.