Tandems and the fabrication thereof

[Michael Catano]

Hello list,

I'm looking at building a tandem frame in the next few months, and i'd appreciate the input of any list members who have experience with designing and building this style of frame.

My experience as a tandem rider is very limited (i've raced a flexy old gitane on a cx course a few times, but that's about it...), so i'm specifically curious about front end geometry to account for the extended wheelbase as well as tubing selection to account for the heavy load.

My thought would be to use a mix of ox p in mtb weights (8/5/8) for the st and tt, and supertherm (1/7/1) for the dt.  The boom tube would be 4130 (.035"? .058"?), but i'm not sure about blades and stays.

Any input would be greatly appreciated.

Thanks,
Michael
chi, il

[M-gineering]

get a - second hand, it's out of print- copy of Tony Oliver's Touring
bikes.

Make sure your workshop is big enough with a tall ceiling


--
mvg

Marten Gerritsen
Kiel Windeweer
Netherlands

[Mark Bulgier]

You may have noticed how tandems in the old days had a too-short rear top tube.  The stoker couldn’t stretch out.  Made for good aerodynamics (closer “drafting”) and lighter weight, but stokers tend to hate those bad old designs.  How much you get to ride the thing depends mostly on how much the stoker likes it. (Rule #1 of tandeming)

 

Most modern tandems have rear top tubes long enough to at least get close the stoker’s single bike position, despite the rear stem facing back instead of forward.  Typically in the 68-75 cm range though some go longer still.

 

That generally requires larger diameter tubing.  I like using a TT that’s larger diameter than the ST, one long tube from HT to stoker ST, piercing it in the middle for the captain’s ST.  Whether it’s one tube or two isn’t as important as the large diameter though.  1-3/8” would not be overkill in steel.

 

Same with the keel tube – big as you can fit.  My fave tube was 1-7/8” x .028.  Dillsburg had a mill-run of that size but we (me and a couple other FBs, notably Dennis Bushnell) used it up.  I think I heard Bushnell commissioned another mill run of the stuff, but he may be keeping it for his own frames. Tubing that large usually isn’t made that thin.

 

2” x .035 would be a bit heavier but possibly worth it if you can find it.  I used it on a couple triplets so I know it has existed at some point but I’m not sure if it is made anymore.  1-3/4” may be the best you can get.  1-1/2” was used in the old days when rear top tubes were short.  It can be adequate but it will be on the flexible side.  (You can get stiffness with thicker wall, but that is an inefficient way to do it, weight-wise, as I’m sure you know.)

 

Front end geometry is usually lower trail than singles, to reduce the lean-steer effect.  I like the head angle a bit steeper if you have room for it (toe-clip overlap) which of course depends primarily on STA, TT length and how much room you need (crank length, tire diameter, presence of fenders etc)

 

Consider 650b (ISO 584)  or MTB 26” (ISO 559) wheels, they help in some of the tandem-specific design trade-offs, and fatter tires help in keeping the stoker’s butt happy (See Rule #1).

 

Mark Bulgier

Seattle

 

 

[jon norstog]

Thanks, Mark.

I'm hearing rumblings from my family WRT how nice a tandem would be.

jn


"Thursday"

On 5/31/12, Mark Bulgier <Ma...@bulgier.net> wrote:
> You may have noticed how tandems in the old days had a too-short rear top
> tube. The stoker couldn't stretch out. Made for good aerodynamics (closer
> "drafting") and lighter weight, but stokers tend to hate those bad old
> designs. How much you get to ride the thing depends mostly on how much the
> stoker likes it. (Rule #1 of tandeming)
>
> Most modern tandems have rear top tubes long enough to at least get close
> the stoker's single bike position, despite the rear stem facing back instead
> of forward. Typically in the 68-75 cm range though some go longer still.
>
> That generally requires larger diameter tubing. I like using a TT that's
> larger diameter than the ST, one long tube from HT to stoker ST, piercing it
> in the middle for the captain's ST. Whether it's one tube or two isn't as
> important as the large diameter though. 1-3/8" would not be overkill in
> steel.
>

> Same with the keel tube - big as you can fit. My fave tube was 1-7/8" x

> .028. Dillsburg had a mill-run of that size but we (me and a couple other
> FBs, notably Dennis Bushnell) used it up. I think I heard Bushnell
> commissioned another mill run of the stuff, but he may be keeping it for his
> own frames. Tubing that large usually isn't made that thin.
>
> 2" x .035 would be a bit heavier but possibly worth it if you can find it.
> I used it on a couple triplets so I know it has existed at some point but
> I'm not sure if it is made anymore. 1-3/4" may be the best you can get.
> 1-1/2" was used in the old days when rear top tubes were short. It can be
> adequate but it will be on the flexible side. (You can get stiffness with
> thicker wall, but that is an inefficient way to do it, weight-wise, as I'm
> sure you know.)
>
> Front end geometry is usually lower trail than singles, to reduce the
> lean-steer effect. I like the head angle a bit steeper if you have room for
> it (toe-clip overlap) which of course depends primarily on STA, TT length
> and how much room you need (crank length, tire diameter, presence of fenders
> etc)
>
> Consider 650b (ISO 584) or MTB 26" (ISO 559) wheels, they help in some of
> the tandem-specific design trade-offs, and fatter tires help in keeping the
> stoker's butt happy (See Rule #1).
>
> Mark Bulgier
> Seattle
>
>

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[Wissahickon Cyclery]

There is a 42mm steel 29R length down tube that is a great boom tube.  It is butted and long enough for upwards of a 30" c to c boom which is a great option.

--
Drew Guldalian
Wissahickon Cyclery
7837 Germantown Ave Phila,PA 19118
www.wiss-cycles.com
www.engincycles.com

[Alex Wetmore]

I haven't built a tandem (it is on the "someday this would be a fun and challenging project" list), but I can talk about what my 2006 Burley uses.  The later Burley tandems are a lot nicer than the early ones, so don't make assumptions if you've only seen the early models.

The top tube is 1-3/8", seat tubes are 1-1/4", downtube is 1-3/8" (I think, I can double check if you like), boom tube is ovalized which makes it hard for me to measure.  The tubing is custom drawn True Temper and was supposedly butted, the top tube is one long tube that was pierced.  Front end geometry is 73 degree HTA, 55mm of fork offset, which is also what Santana uses.  The wheels are 559/26", which gives a trail figure right around 40mm with normal MTB slick tires.  You can see the full geometry of their bikes here:

http://web.archive.org/web/20050519010108/http://burley.com/images/PDF/RocknRollSpec.pdf

We have it built up with drop bars, I think of it as kind of a tandem equivalent of a Surly Long Haul Trucker.  Comfortable, load carrying ability, sporty enough but not fast.

If I were building a custom tandem tomorrow I'd copy the geometry of my Rock'n'Roll but increase the top tube height to get ride of my high rise stem.  I'm borderline too tall for the medium and borderline too short for the large, and my wife could stand over the medium but not the large, so we have a medium.

I have plans to build a higher offset fork to see how it handles, just because I'm curious.  With the 40mm trail it feels sort of like a normal road bike (trail in the mid-50s), and I'm curious to see if building a 30mm trail fork would have it handling more like my single bikes (which all have trail figures in the mid-40s).

Bicycle Quarterly has also listed the geometry of old Rene Herse and other tandems in a few issues.  I think they used a higher HTA (like 74 degrees) to get lower trail, but my memory is likely wrong here.

Dillsburg lists 1-3/4" x 0.035":

http://www.phred.org/~alex/bikes/dillsburg2010.pdf

I haven't found them to be too excited about selling tubing shorter than one length (17-24', usually 18').  Aircraft Spruce, Wicks Aircraft, McMaster Carr and Online Metals don't list it as an option.

alex

---

From: frameb...@googlegroups.com [frameb...@googlegroups.com] on behalf of Mark Bulgier [Ma...@bulgier.net]
Sent: Thursday, May 31, 2012 12:05 PM
To: Michael Catano; framebuilders
Subject: RE: [Frame] Tandems and the fabrication thereof

--

[David Porter]

I made the last two from Spirit down tubes and a couple seat tubes.. Rodriquez has 700mm oval boom tubes..  all filet of course but very light and strong too…..

Dave

Read back in my blog below (bicycle category) for both builds if you’re looking for cheap help…

fro...@porterscustom.com

Porter Customs   2909 Arno NE
Albuquerque, NM USA 87107
505-352-1378
1954 BN2  1959 AN5
Porter Custom Bicycles

cars:
 www.britishcarforum.com/portercustoms.html
gallery: http://picasaweb.google.com/porterscustombicycles/PorterCustomBicyclesStuff

GO HERE: http://porterbikes.com/  nice pictures-fun facts-my world

---

[wade barocsi]

Hi Michael,

The top tube is quite important. Go as large as reasonable, it makes
climbing much easier while standing, and greatly improves cornering
The lateral tube stiffens up the rear bb and triangulates things, but
it's really the top tube stabilizing the stoker. Be sure to support
the rear with larger diameter stays.
I would use 1.25 tapered chainstays and 7/8 seat stays.

We've got a good selection of frame and fork tubes for tandems in a
both 4130 and a high strength air hardening HSLA steel.
Tandem stuff isn't on the website yet, but we can send cad drawings.

Wade Barocsi
www.Aceltube.com
www.cycledesignusa.com

[Andrew R Stewart]

Michael- I haven't built a tandem frame, yet, but have a lot of thought and customer experience to draw from.

 

Steering geometry seems to fall into a couple of categories. The early teams prefer Santana/Burley like numbers. Low trail to minimize stoker steer. The experienced, and sporting, teams trend to CoMotion/Calfee numbers. More single like numbers. The more experienced teams have gotten past the learning curve of stoker steer and communication challenges and often can handle a livelier ride.

 

It's hard to make a tandem too stiff lengthwise. It's hard to make a tandem too long in the rear compartment. The chain stay lengths have little reference to single bike numbers. You'll be using a broader range of gears and should allow for more cross chaining.

 

Make the service aspects real easy. By this I mean the braze ons/cable routing as well as any accessory additions. Simple cable routing, minimal housing. NO INTERNAL ROUTING. Include adjusters on all runs. AGAIN, NO INTERNAL CABLES. Do your homework about the Ft BB shell. This is where I am not fully decided. I have used set screw, split shell with binders and expanding wedge eccentrics and am not convinced of which I would build with. (And am willing to listen to advice here).

 

Generally a tandem is meant to be a long term affair (bad pun). So conservative and time proved methods are best, IMO. Andy.   

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Andrew R Stewart
Rochester, NY

[Michael Catano]

Andrew, Mark, and everyone else, thanks greatly for the input.
Definitely a lot to think about.

I'm interested in checking out Tony Oliver's book. Hopefully I can
track down a copy through inter-library loan and take a peek; it looks
like used copies are in the $70 range, which seems a bit steep.

W/R/T Andrew's question on front BB - I was thinking of using a BB30
shell and the Team Beer eccentric adapter (seen here:
http://beercomponents.com/?page_id=24). A client used one to convert
a CX frame to SS and had no issues racing on it. It seems like a
clean and easy way to adjust chain tension on the front crank.

Best
Michael
chi il

[Alex Wetmore]

How are you going to mill your BB shell to the BB30 standards? I assume that BB30 requires this to be done after brazing or welding to fix distortion issues. I haven't looked to see if Park or other companies have started to make facing and reaming tools for these newer standards.

For my one eccentric BB bike so far I used the Easton insert that Nova sells and split the edges with binders. This gives the advantage of not requiring any facing or reaming afterwords (as long as you use something to prevent the BB shell from distorting too much during brazing) and it is very inexpensive. It is a bit heavy though.

http://alexandchristine.smugmug.com/Bicycles/Framebuilding/Wetmorian11/8404803_fVqhjh#!i=721990893&k=xWuZh
and
http://alexandchristine.smugmug.com/Bicycles/Framebuilding/Wetmorian-1/7709240_xP2pj2#!i=521824958&k=bBdox

I copied the idea for splitting the shell this way from Alistair Spence, he copied it from Rene Herse, and I don't know who he copied it from. I like it. It is fast to make on a milling machine with a slitting saw, I recently made a demonstration shell for a friend in 15-20 minutes.

I also have a Seven MTB with the Bushnell eccentric that seems to work reasonably well. However that design seems to benefit from being able to ream the shell back to round afterwords, and 2" reamers aren't cheap.

For either BB30 or reaming a 2" shell you could use a milling machine, I just don't like doing more advanced milling operations (I'm a newbie and likely to make a mistake) 10+ hours into a project that could force me to start over.

alex

________________________________________
From: frameb...@googlegroups.com [frameb...@googlegroups.com] on behalf of Michael Catano [shuffl...@gmail.com]
Sent: Thursday, May 31, 2012 9:06 PM
To: Andrew R Stewart
Cc: framebuilders
Subject: Re: [Frame] Tandems and the fabrication thereof

[Michael Catano]

Alex asks: "How are you going to mill your BB shell to the BB30

standards?  I assume that BB30 requires this to be done after brazing
or welding to fix distortion issues."

FSA sells a BB30 reamer that fits on the park HT reamer tool - it
works well and isn't particularly expensive. I've made at least a
dozen BB30 frames at this point and haven't had any problems as of yet
as far as premature bearing wear, etc (touch wood).

[Andrew R Stewart]

Michael- I have no experience with BB30 shells as a builder. the few I've
dealt with as a shop wrench have been frustrating, as any new standard can
be. See my remark about traditional standards and tandems. The eccentric
movement suggests enough to cover chain half link issues. Still I would be
more conservative. I'm still not sure how this solution is fixed in
position, outside of a couple of through bolts that run off center of the
axle. Not sure if this is the best design... Additionally the machining of a
BB30 shell has had some talk before. Source a reamer first.

Again I'll repeat a mantra of mine. The ease of maintaining a bike is in
direct relationship to the reliability of it. Andy.

[Harold Bielstein]

Now this is a Tandem!! http://www.hetchins.org/504tan2.htm
Hal Bielstein
hkbie...@rap.midco.net

[Mark Bulgier]

Harold Bielstein wrote:
> Now this is a Tandem!!
> http://www.hetchins.org/504tan2.htm

Yes it's a tandem, but I sure wouldn't want to ride it.

That stoker cockpit is so short that sitting will be uncomfortable, and standing will be impossible.

The severely undersized tubing tells me it's either alarmingly whippy, or heavy, or both.

The 1" steerer and single-bike size fork blades are simply moronic. Oversized tandem grade stuff has been easily available since the '30s at least and still is available today -- no excuse for that.

I predict this bike will get more cobwebs than road dust on it.

Mark Bulgier
Seattle

[Mathias Scherer]

I too would think this is maybe nicer to look at than to ride.

--
Mathias Scherer
Ludwig & Scherer GmbH
Wintringerstrasse 19
66271 Kleinblittersdorf

Geschäftsführer Mathias Scherer

[Peter White]

On Fri, Jun 1, 2012 at 12:00 AM, Andrew R Stewart <onet...@earthlink.net> wrote:

Do your homework about the Ft BB shell. This is where I am not fully decided. I have used set screw, split shell with binders and expanding wedge eccentrics and am not convinced of which I would build with. (And am willing to listen to advice here).

For the eccentric, do what Co-Motion does, pinch bolts.

The set screws that Santana uses are horrible. They make little divots in the eccentric, so when the user needs to make fine adjustments as the chain stretches a bit, he's screwed since the set screw wants to settle back into the divot, rather than where it needs to be.

The expanding wedges (Cannondale?) allow for fine tuning, but they're also prone to seizing up. So after a few years the user can have a very hard time loosening it.

The pinch bolts that Co-Motion uses are trouble free and allow for easy fine tuning. If you like your customer, use pinch bolts. ;-)

--
Peter Jon White

Peter White Cycles

[Harold Bielstein]

Yes, I'm sure you're right but it sure is a work of art. I've always wondered about the double marathon design in regards to stability/handling qualities and overall weight. Is there a reason that the double marathon design has fallen out of favor? Can it not be intelligently designed with current technology tubing?

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Hal Bielstein
hkbie...@rap.midco.net

[David Porter]

The Hetchins legacy and history is long and storied. Though this would
probably be more aptly be called a replica, it is true to it's heritage (new
components notwithstanding) and I find it disappointing to hear experts call
it wrong or with issues.. tisk tisk
Dave

fro...@porterscustom.com

Porter Customs 2909 Arno NE
Albuquerque, NM USA 87107
505-352-1378
1954 BN2 1959 AN5
Porter Custom Bicycles

cars:
www.britishcarforum.com/portercustoms.html
gallery:
http://picasaweb.google.com/porterscustombicycles/PorterCustomBicyclesStuff

GO HERE: http://porterbikes.com/ nice pictures-fun facts-my world

-----Original Message-----
From: frameb...@googlegroups.com [mailto:frameb...@googlegroups.com]

[Michael Catano]

Mark mentions the limitations of single-rider/1" fork blades on the
Hetchins. Is there a currently available 28/20 oval fork blade that's
more suited to the job? The Pacenti mtb crown seems like it'd offer
plenty of clearance and support (and also comes in 28.6) - but is a
1.0mm wall blade not stout enough?

While we're on the topic, here's another lovely tandem from A. Singer:

http://4.bp.blogspot.com/-dfPCLv3oMp4/T38su_oM4FI/AAAAAAAAGmQ/CrzUVnQw4JA/s1600/DSC_5587.jpg

The crown and blades look beefier than on traditional frames - I'm
pretty sure Singer (or maybe herse?) supplied the Taylor brothers with
their tandem parts.


Thanks again for all the great contributions,
Michael

[dave bohm]

 

Dillsburg lists 1-3/4" x 0.035":

http://www.phred.org/~alex/bikes/dillsburg2010.pdf

 

I haven't found them to be too excited about selling tubing shorter than one length (17-24', usually 18').  Aircraft Spruce, Wicks Aircraft, McMaster Carr and Online Metals don't list it as an option.

 

alex

 

 

Acel tubing.  i.e. http://www.aceltube.com

We have all sorts of American produced  4130 seemed and seemless.   We currently have 1.75 x .035.    I am trying to work on the shopping cart to include tiers for shipping various amounts of straight gauge shipping but if you look under store/cro-moly  you will see what we have available and the pricing.   Just call or write in for a shipping quote.

We are less expensive than any other option BTW and carry only the sizing typically used in bicycles and bicycle related vehicles.

Dave Bohm

 

 

 

 

 

[Mathias Scherer]

I've used the Bushnell excenter in a couple of solo bikes I built. I'd recommend it highly over the other designs mentioned here (all of which I tried in bikes I either built or owned, and I can only subscribe to what Peter says).

--

[Alex Wetmore]

I don't know of a 28x20 blade that is up for the job. I plan on making the new fork for my tandem using the Nova heavy duty crown and blades:
http://www.cycle-frames.com/bicycle-frame-tubing/EVEREST-CYCLE-X-FORK-CROWN-old-school-70mm-width-for-28.6mm-steerer.html
http://www.cycle-frames.com/bicycle-frame-tubing/CRMO-25.4mm-OVAL-TANDEM-CHAINSTAY.html

It fits the same size tires as a Pacenti MTB crown.

I'm going to make little plates to fill in the open voids between the "twin plates" and turn it into a box section crown. That should greatly increase the torsional rigidity of the fork crown, and I think that it can be done in an elegant manner if the inserted plates are slightly recessed, leaving the lines of horizontal plates visible. I also plan on reshaping the sides a bit, I'm not a big fan of the 3 windows plus the little florish on the bottom.

I can't say if this is sufficient or not, but it seems like the beefiest easily available option for a crowned fork.

I've had the parts sitting around for months waiting for me to finish this project, maybe it'll happen soon. One downside is that those blades (which are very beefy) don't take the most elegant bend if you use a tight radius fork blade bender. It would be easier to explain in photos, which I can take if there is interest. Nova also makes a lighter weight fork blade for this crown, but I personally feel more comfortable with the beefy one on a tandem.

alex
________________________________________
From: frameb...@googlegroups.com [frameb...@googlegroups.com] on behalf of Michael Catano [shuffl...@gmail.com]

Sent: Friday, June 01, 2012 6:44 AM
To: Harold Bielstein
Cc: Mark Bulgier; framebuilders
Subject: Re: [Frame] Tandems and the fabrication thereof

[Wade Patton Velo]

iirc there was a section in my long lost paterek manual wrt the various
ways of assembling the pipes--a primer you know.

Bill McCready lit up my tandem interests with his seminar at
Sacramento. He said they were good for picking up womerns who already
own sidis and such...hmmmmm. I'm making notes of our current discussion.


back to my peanuts...

wp

Harold Bielstein wrote:
> Yes, I've always wondered about the double marathon design

[Harold Bielstein]

A quote from Tony Oliver's book (Touring Bikes A Practical Guide) on the merits of the double marathon design: "The design is so efficient that super light weight tubes can be used, such as Reynolds 753R and I often mix tubes from Reynolds and Columbus in the creation of double-marathon racing and randonnee frames."

Not sure what diameters 753R tubes came in and are also no longer commercially available. I'm sure there are other lightweight tubing selections available that can be substituted.

Hal Bielstein
hkbie...@rap.midco.net

[Michael Catano]

I'm pretty sure 753 was roughly equivalent to modern-day columbus
Zona; a mix of 8/5/8 and 7/5/7 tubes.

m

[Doug Fattic]

I wouldn't be too quick to dismiss the ride of the Hetchins tandem.
Sometime in the 70's Columbus came out with a tandem set of tubing and
lugs that was based on 1" top tubes and a 1 1/8" down tube. All of the
tubes were SP type 1/7/1 except the down tube which was 1.2 at the butted
ends. The round boom tube was 1.5" and .058" wall thickness (which may
have been 1.5mm). The lateral reinforcements were 9/16" (14mm) stays.
The seat stays were standard issue SP 16mm and the chain stays were what I
think was their track sprint type that were round 22.2 diameter into the
bb shell but expanded to about 1" right afterward that then eventually
tapered again to the dropouts. The fork blades were oversized and they
provided a machined twin plate crown to accommodate them. The steerer was
1".

At the time I wondered if the tubes were way too skinny to be used in a
tandem application. Remember this was in a time before MTBs when double
butted standard oversize tubing wasn't generally available. Conveniently
for me Ben Serotta was showing a tandem he built out of this combination
at the New York show and I asked him about the ride. He said it worked
just fine no issues. So I built one too out of this Columbus tube and lug
collection except I swapped out Henry James lugs where I could. For the
laterals I went from the middle of the head tube to the outside edges of
the rear bb shell. I didn't put in a 2nd set from the rear seat lug to
just above the rear dropouts like the Hetchins has. I figured I'd try it
out and see if they needed to be added. Mostly it was for me to ride with
my young daughter so it wouldn't be stressed. All 5'8" and 130 lbs of me
loved the way it rode. Neither was anything an issue when I rode it with
my wife (whose weight is now and forever a secret). Even when I took it
on training rides and put a cat 2 or 3 on the back (the only time I could
force the pace at the front) it didn't sway around or was noticeably
whippy. There was one bigger guy who had a choppy stroke and it was all I
could do to handle it on rides but I'm sure it would have been the same
problem on a Santana. And I could have made it stiffer with the addition
of another set of laterals from the rear seat lug to the dropouts.


Over the years I've made several tandems with oversized tubes with an oval
boom tube and all that but I didn't like the ride of them better than my
Columbus tandem. Of course I'm not a big guy. Another reference point
was the old tandem Gitanes that were simply standard size main tubes
without any lateral supports. They were pretty flexy. For a customer I
put in twin seat stay type laterals and he said it made a vast improvement
and rode fine after that.

My experience with this Columbus standard size tube set up (which I still
have and can ride) leads me to believe that if riders aren't big strong
men it is possible to design a marathon frame (2 sets of twin laterals on
each side like the Hetchins) that will ride nicely. Of course now I would
use lighter OS tubes. In the same way a 1" 7/4/7 top tube works perfect
for me and would be way wrong for a bigger person, the same applies to
tandem design as well. Keep in mind that our opinions of what tubing and
designs we should use are based on high end semi production frames that
the company doesn't know for sure if the riders are not big and heavy and
will always error on the side of bigger tubes to compensate. I'm sure
some 6'2" 200+ pound guy would write a really negative review of my
Columbus tandem too but that doesn't mean it isn't just right for me.

Doug Fattic
Niles, Michigan

Harold Bielstein wrote:
>> Now this is a Tandem!!

>> http://www.hetchins.rg/504tan2.htm <http://www.hetchins.org/504tan2.htm>

On 6/1/12 2:54 AM, "Mark Bulgier" <Ma...@bulgier.net> wrote:
>>
>
>Yes it's a tandem, but I sure wouldn't want to ride it.
>
>That stoker cockpit is so short that sitting will be uncomfortable, and
>standing will be impossible.
>
>The severely undersized tubing tells me it's either alarmingly whippy, or
>heavy, or both.
>
>The 1" steerer and single-bike size fork blades are simply moronic.
>Oversized tandem grade stuff has been easily available since the '30s at
>least and still is available today -- no excuse for that.
>
>I predict this bike will get more cobwebs than road dust on it.
>
>Mark Bulgier
>Seattle

[TIM.N...@comcast.net]

I agree with Peter...pinch bolts! http://www.flickr.com/photos/lighthouse_cycles/sets/72157629999764438/
Tim
www.lighthousecycles.com

Tim Neenan %7C tim.neenan%40comcast.net

---

From: "Peter White" <peter...@gmail.com>
To: frameb...@googlegroups.com
Sent: Friday, June 1, 2012 5:03:29 AM

Subject: Re: [Frame] Tandems and the fabrication thereof

--

[Eric Keller]

Sometime in the late '70s it became possible to buy an oversize set of tandem tubes in Reynolds 531.  My tandem was the first bike I ever built with oversize tubes.  I made it as  long as the boom tube supplied by Reynolds would allow, so it's a little short.  The Reynolds set had no reinforcing tubes, so I added lateral tubes from the head tube to stoker bb, and from the captain's seat cluster down to the rear dropouts.  It was noticeably stiffer than the standard tubing Paramount that I had ridden on, but in the end the ride was substantially similar. 

The Reynolds set had a 1" steerer, but I think the thing that worries me most about the bike is the crown.  It was an early investment cast crown made for single bikes.  I've never had any issues with the bike, but I'm not riding it much anymore.  It's an awesome utility bike if you can ignore the shouts of "you forgot somebody"
Eric Keller
Boalsburg, PA

[Mark Bulgier]

Eric Keller wrote:

It's an awesome utility bike if you can ignore the shouts of "you forgot somebody"

Whenever someone says that to me I reply “Oh thank you, I thought I’d gone deaf!”

 

Mark Bulgier

Seattle

[Mark Bulgier]

Harold Bielstein

>
> I've always wondered about the double marathon design in regards to
> stability/handling qualities and overall weight. Is there a reason
> that the double marathon design has fallen out of favor? Can it not
> be intelligently designed with current technology tubing?

I believe, without any proof, that the best internal bracing scheme is NONE, i.e. the "open frame", but with the weight you would have put into extra bracing tubes put instead into making the top tube and bottom tube larger diameter.

Mark Bulgier
Seattle

[Mark Bulgier]

David Porter wrote

>
> The Hetchins legacy and history is long and storied. Though this would
> probably be more aptly be called a replica, it is true to it's heritage
> (new components notwithstanding) and I find it disappointing to hear
> experts call it wrong or with issues.. tisk tisk

A Hetchins tandem made by the real Hetchins shop probably would have had oversized tubes, especially the steerer and forks. Those were commonplace in the 1890s through the 1950s, everyone back then knew to use OS parts on a tandem. Some had these huge Timken roller bearings for the lower headset, with the lower headlug bulged out to accommodate them. Then most (not all) modern builders forgot the lessons of their predecessors.

Mark Bulgier
Seattle

[Alistair Spence]

On Fri, Jun 1, 2012 at 11:33 AM, Mark Bulgier <Ma...@bulgier.net> wrote:

> I believe, without any proof, that the best internal bracing scheme is NONE, i.e. the "open frame", but with the weight you would have put into extra bracing tubes put instead into making the top tube and bottom tube larger diameter.
>

This is how I've always seen it too although I must admit, this is
coming mostly from an engineering perspective, not a riding one.

I've only got appreciable riding time on one tandem, the one I
currently own, so I'd be interested in hearing others perspective on
this (ie. Twin laterals Vs. over sized tubing).

Alistair.

[David Porter]

..and I'd wager they did not use oversize tubes.. the available lugs were
for all standard size tubes, though often, especially the fork blades were a
thicker wall. Remember the chromemoly and earlier sewer pipe bikes were God
awful strong and heavy. I would only concern myself with the choice of
crowns in the pictured tandem and short of running into a bridge abutment
even that is, well, adequate IMO. Steel is still a remarkable product and
though it has some shortcomings it at least does not fail catastrophically.
Tandems are inherently heavy and anything to lighten them is good, once
again IMO. Typically the only OS tube was the boom tube.
dave

fro...@porterscustom.com

Porter Customs 2909 Arno NE
Albuquerque, NM USA 87107
505-352-1378
1954 BN2 1959 AN5
Porter Custom Bicycles

cars:
www.britishcarforum.com/portercustoms.html
gallery:
http://picasaweb.google.com/porterscustombicycles/PorterCustomBicyclesStuff

GO HERE: http://porterbikes.com/ nice pictures-fun facts-my world


-----Original Message-----
From: frameb...@googlegroups.com [mailto:frameb...@googlegroups.com]
On Behalf Of Mark Bulgier
Sent: Friday, June 01, 2012 12:41 PM
To: David Porter; 'framebuilders'
Subject: RE: [Frame] Tandems and the fabrication thereof

[Mark Bulgier]

Michael Catano wrote:
>
> While we're on the topic, here's another lovely tandem from A.
> Singer:
>
> http://4.bp.blogspot.com/-dfPCLv3oMp4/T38su_oM4FI/AAAAAAAAGmQ/CrzUVnQw4JA/s1600/DSC_5587.jpg
>
> The crown and blades look beefier than on traditional frames - I'm
> pretty sure Singer (or maybe herse?) supplied the Taylor brothers
> with their tandem parts.

I don't think so, they were just Reynolds tandem blades, supplied by Reynolds to both Singer and the Taylors. When I used them in the 70s-90s we always called them Jack Taylor blades, in fact I seem to remember that's what Reynolds themselves called them.

Pretty sure the blades were made from 1" round stock, compared to 24 mm for normal road bike blades.

Haden made a sand-cast crown for the Taylor blades that was a bit ugly but could be made to look pretty nice.

Rodriquez made their own cast tandem crowns for Taylor blades, and they were fairly awesome, with huge integral reinforcing tangs down the inside of the blades that were not decorative, they were thick and strong, but tapered down to fine points. Kinda heavy, but I used to machine 'em down in key areas, making the best tandem crown ever IMO. They could be bored for inch or 28 mm steerers. (28 mm was the only OS steerer back then before 1-1/8" steerers were developed).

Columbus tandem blades (early 80s I think) were also made from 1" round, but they were less ovalized than Taylor blades, much like the oval of their single bike blades, and a bit thinner wall (lighter). Columbus supplied a machined two-plate crown with those.

My own road race tandem (circa 1990) has modified Columbus blades and a heavily modified Haden crown.

Mark Bulgier
Seattle

[Mark Bulgier]

David Porter wrote

>
> ..and I'd wager they did not use oversize tubes.. the available lugs
> were for all standard size tubes, though often, especially the fork
> blades were a thicker wall.

Well you can't say the available lugs were ALL for standard size tubes. Most lugged pre-WWII tandems I can remember (I've seen maybe a couple dozen over the years) had at least some OS tubes, like 1-1/8" top tubes. I think standard sized lugs for tandems is what was unusual.

I think over the years tandems became less common, more of a novelty, so the choices in available parts was reduced.

I've seen numerous '50s lugged tandems with OS tubes, but I believe on those, the builders had to fabricate the lugs one at a time because there was no longer the plethora of mass-produced choices.

Mark Bulgier
Seattle

[Ken Cline]

Eliminating all the internal bracing means breaking the triangular truss structure of the frame, leaving an open parallelogram between stoker and captain. The design can work, but I don't see how you can maintain in-plane stiffness without adding weight (unless, of course, the weight is needed for torsional stiffness).

[Jeff...@aol.com]

 

 

In a message dated 6/1/2012 7:16:44 A.M. Pacific Daylight Time, al...@phred.org writes:

I don't know of a 28x20 blade that is up for the job.

Reynolds did make a thick blade of that size that worked and a number of builders used them.  I never used them as the "Taylor Pattern"  blades  seemed like a better choice with the Haden crown which was a lot of fun to file.....Jeff

[Mark Bulgier]

Ken Cline wrote

>
> Eliminating all the internal bracing means breaking the triangular
> truss structure of the frame, leaving an open parallelogram between
> stoker and captain. The design can work, but I don't see how you
> can maintain in-plane stiffness without adding weight (unless, of
> course, the weight is needed for torsional stiffness).

True in theory, but the many open frame tandems that have been on the road for decades never seemed to suffer any ill-effects from their relative lack of in-plane stiffness. Both Singer and Herse made many tandems this way, and no one complained of them being too vertically compliant, that I know of. Calfee too!

Are you sure you want more in-plane stiffness anyway? Seems like in-plane flex just makes the bumps less painful, without affecting the cornering stability or power transmission, as long as out-of plane bending and twist are adequately resisted.

Mark Bulgier
Seattle

[Colin Bryant]

My experience with pinch bolt eccentric BBs is that they creak under load, vs set screws, which don't move.  I've never tried the Bushnell variety.

 

--

Colin Bryant
Vancouver, Canada

---

From: Peter White <peter...@gmail.com>
To: frameb...@googlegroups.com
Sent: Friday, June 1, 2012 5:03:29 AM

Subject: Re: [Frame] Tandems and the fabrication thereof

[Alex Wetmore]

The semi split style that I posted never creaks for me, and Alistair Spence has also had good luck with it.  Keeping the center of the shell intact seems like it would add some lateral strength. 

My Burley tandem has set screws with the issue that Peter White mentioned, you can't make fine adjustments because the screws always find the old divots. Maybe a brass tipped set screw would do the job better.  I made a couple of those for a friends French bike (either an Alan or Time) that used a set screw to hold the seat post in place.  It seems to hold about as well and doesnt mess up his seat post. 

alex

[Mark Bulgier]

Colin Bryant wrote:

 

My experience with pinch bolt eccentric BBs is that they creak under load, vs set screws, which don't move.  I've never tried the Bushnell variety.

 

Really?  That’s the first time I’ve heard that.  The hundreds of custom tandems I made all had split shells with pinch bolts, and I never heard a creak, or even heard of one second-hand.

 

The Bushnell device really is clever and cool though, I might be tempted to use one on my next tandem, if there ever is a next one. They came out about at the end of my tandem building career.  We used them on the titanium tandems we built at Ti Cycles in the 90s.  I was not the primary designer or Ti tandem builder there; that was owner Dave Levy, so I don’t claim those as “tandems I built”.  They were perfectly reliable though as far as I know.  I’m also friends with some current (or more recently retired from building than I am) tandem builders who use and like them.

 

I used to go to all the tandem rallies and have ridden with or spoken to probably thousands of tandemists over the last 3-4 decades, and I heard many people dissatisfied with their Cannondale wedge types and their set-screw types.  Almost no complaints about pinch bolts or Bushnells.

 

Mark Bulgier

Seattle

 

[TIM.N...@comcast.net]

I always used split style BBs on my tandems and noise was never a problem.
Tim
www.lighthousecycles.com

Tim Neenan  tim.n...@comcast.net

---

From: "Alex Wetmore" <al...@phred.org>
To: "Colin Bryant" <sk8sk...@yahoo.ca>
Cc: frameb...@googlegroups.com
Sent: Saturday, June 2, 2012 11:25:21 AM

[Peter White]

That's odd. Had you greased the shells? I've never had a problem, not with any of the Co-Motions I've ridden and sold, nor with any of the Tout Terrain singles we sell now. The TTs use eccentrics on the internal gear bikes, using Rohloffs and Shimano Alfine, so as to eliminate the chain tensioner. Not a single problem with creaking.

PJW

[Colin Bryant]

I should add that my experience was with an aluminum production frame.  It may be different with a steel or titanium shell.  On another aluminum production frame, I never had difficulty with set screws going into the old holes, but that bike didn't have a front derailer, so a slight change in chain line wasn't an issue.

 

--

Colin Bryant
Vancouver, Canada

---

From: Mark Bulgier <Ma...@bulgier.net>
To: Colin Bryant <sk8sk...@yahoo.ca>; "frameb...@googlegroups.com" <frameb...@googlegroups.com>
Sent: Saturday, June 2, 2012 11:49:50 AM
Subject: RE: [Frame] Tandems and the fabrication thereof

[Colin Bryant]

The shell was dry, from the factory, so that's how I kept it.

 

--

Colin Bryant
Vancouver, Canada

---

From: Peter White <peter...@gmail.com>

To: "frameb...@googlegroups.com" <frameb...@googlegroups.com>
Sent: Saturday, June 2, 2012 3:28:46 PM

Subject: Re: [Frame] Tandems and the fabrication thereof

--