Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 04-02-07, 05:44 PM   #1
Allen
Senior Member
Thread Starter
 
Join Date: Sep 2005
Bikes:
Posts: 4,751
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Curved top tube

What are the ramifications of a curved top tube, like those found on cruisers? Are they significantly weaker than a straight tube? Same questions about curved seat stays.

Thanks,

--A
Allen is offline   Reply With Quote
Old 04-02-07, 08:36 PM   #2
thatcher
Senior Member
 
thatcher's Avatar
 
Join Date: Jan 2005
Bikes:
Posts: 285
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
beach cruiser tubing is much thicker than a road bikes.
thatcher is offline   Reply With Quote
Old 04-03-07, 03:52 AM   #3
cs1
Senior Member
 
cs1's Avatar
 
Join Date: Feb 2004
Location: Clev Oh
Bikes: Specialized, Schwinn
Posts: 6,652
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Quote:
Originally Posted by AllenG
What are the ramifications of a curved top tube, like those found on cruisers? Are they significantly weaker than a straight tube? Same questions about curved seat stays.

Thanks,

--A
Check out these: http://ingliscycles.com/bikes/retrotec_home.php He's been doing them for a while with no complaints. I'm thinking it might be my next bike.

Tim
cs1 is offline   Reply With Quote
Old 04-03-07, 06:30 AM   #4
snowy
Beauty Everywhere
 
snowy's Avatar
 
Join Date: Jan 2005
Location: Colorado
Bikes: 2006 Giant Anthem, Specialized Dolce Elite 05
Posts: 2,596
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by AllenG
What are the ramifications of a curved top tube, like those found on cruisers? Are they significantly weaker than a straight tube? Same questions about curved seat stays.

Thanks,

--A
AllenG my boyfriend had two custom cruisers that he rides. Both are mountain bikes. He has never had any issues with the top tube. He also races on them.

Here are some pics for your viewing, http://gallery.mtbr.com/showgallery....&ppuser=263629
__________________
"RIDE FAST TAKE CHANCES!"

Interested in the Women's Forum? Send me a PM for more information.
snowy is offline   Reply With Quote
Old 04-03-07, 08:16 AM   #5
Scooper
Decrepit Member
 
Scooper's Avatar
 
Join Date: Aug 2005
Location: San Francisco California
Bikes: Waterford 953 RS-22
Posts: 10,126
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Quote:
Originally Posted by AllenG
What are the ramifications of a curved top tube, like those found on cruisers? Are they significantly weaker than a straight tube? Same questions about curved seat stays.

Thanks,

--A
When Frank Schwinn patented the frame design popularly known as the "cantilever frame" in the late thirties, the claims made in the patent were that the two small diameter curved tubes welded to each side of the down tube, then carried back to the seat tube where they are welded to each side the seat tube near the seat post clamp, and then finally transitioned to become the seat stays, "...resist certain strains, resultant from accidental or other overloads, which frequently destroy other bicycle frames, - i.e. those strains which tend to twist the axis of the steering head (now called the head tube - Stan) out of the plane which includes the axis of the saddle post mast (now called the seat tube - Stan), and those strains which tend to disrupt the union between the steering head and the reach tube (now called the down tube - Stan) which, in the normal use of the bicycle, constitutes a tension member acting between the steering head and the crank hanger."

It is no accident that the first home made "mountain bikes" were built using these extremely rugged frames.



__________________
- Stan
I'm with her.

Last edited by Scooper; 04-03-07 at 12:34 PM.
Scooper is offline   Reply With Quote
Old 04-03-07, 12:00 PM   #6
Allen
Senior Member
Thread Starter
 
Join Date: Sep 2005
Bikes:
Posts: 4,751
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thank you all.
I laid the contents of my parts bin out on the floor the other day and it just screams cruiser.
I've also ordered the Paterek manual and a dozen or so other books recently, got my hands on an Henrob torch and a set of tanks, and today I'm heading down to the police station to pick up a few frames that did not sell in the last stolen bike auction. By the end of the summer I hope to have my first frame on the road.

My parts bin


and my {current** inspiration
Allen is offline   Reply With Quote
Old 04-03-07, 12:20 PM   #7
SamHall
Senior Member
 
Join Date: Jan 2005
Bikes:
Posts: 131
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
As was said before, you won't have any strength concerns as most curved tubes are made from straight gauge stock. And considering you're planning a double TT cruiser, no worries. For some good info on bending your own TT's, check out Steve Garro's posts on the subject on frameforum- good luck!
SamHall is offline   Reply With Quote
Old 04-03-07, 10:06 PM   #8
NoReg
Banned
 
Join Date: Aug 2005
Bikes:
Posts: 5,117
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
If you take that rust frame, the beauty of the triangle is that whether under tension or compression the straight tubes are loaded in collumn. for instance the top tube there is loaded mostly in compresion so the curved tube is much less strong when it is extremely bent like that, and the welds are put under uneven loads if the tube flexes. Same thing with the rear triangle, the SS is going to work a little bit like a pole vaulters pole there. It's a sign of serious misalignment when the ends are out of line with themiddle of the tube, not even overlapping.

Hey it all works as long as the matrials are stout enough. I like curved tubes. On real working bikes, they do seem to be a little lazy, but on lazy bikes they fit right in. I don't really like the double top tube design though, kinda looks like the designer just wasn't sure...
NoReg is offline   Reply With Quote
Old 04-04-07, 08:46 AM   #9
Allen
Senior Member
Thread Starter
 
Join Date: Sep 2005
Bikes:
Posts: 4,751
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Peterpan1
If you take that rust frame, the beauty of the triangle is that whether under tension or compression the straight tubes are loaded in collumn. for instance the top tube there is loaded mostly in compresion so the curved tube is much less strong when it is extremely bent like that, and the welds are put under uneven loads if the tube flexes. Same thing with the rear triangle, the SS is going to work a little bit like a pole vaulters pole there. It's a sign of serious misalignment when the ends are out of line with themiddle of the tube, not even overlapping.

Hey it all works as long as the matrials are stout enough. I like curved tubes. On real working bikes, they do seem to be a little lazy, but on lazy bikes they fit right in. I don't really like the double top tube design though, kinda looks like the designer just wasn't sure...
The Rust bike is one of Mike Flanigan's (A.N.T.) 29er designs.
Allen is offline   Reply With Quote
Old 04-08-07, 06:01 PM   #10
jacobs
Senior Member
 
jacobs's Avatar
 
Join Date: Apr 2005
Location: Boston, MA
Bikes: http://www.jacobsbicycles.com
Posts: 787
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
your parts bin has a ROHLOFF in it??
jacobs is offline   Reply With Quote
Old 04-08-07, 09:01 PM   #11
silversmith
Yet another vegan biker
 
Join Date: Dec 2005
Location: Trapped behind the corn curtain
Bikes: Sakae Prism, Vintage Fuji bike(S), too many bikes, one from scratch bike.
Posts: 965
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
And he could strap an elks haunch on that rear rack...
silversmith is offline   Reply With Quote
Old 04-09-07, 01:09 AM   #12
NoReg
Banned
 
Join Date: Aug 2005
Bikes:
Posts: 5,117
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
"The Rust bike is one of Mike Flanigan's (A.N.T.) 29er designs."

I've seen a number of respected guys do that double top tube thing. When you figure you could do just fine with one straight tube... It's one thing back in the day when fun was a cardboard clacker in the spokes...
NoReg is offline   Reply With Quote
Old 04-09-07, 10:22 AM   #13
Allen
Senior Member
Thread Starter
 
Join Date: Sep 2005
Bikes:
Posts: 4,751
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by jacobs
your parts bin has a ROHLOFF in it??
I have a work bike that I gave to my brother. I stripped the Rohloff off of it before hand. My brother has since given me the frame back, but I think the hub would serve me better on a frame other than the work bike's.

The rear rack is a Tubus Cargo rack, basically the same as a Tubus Logo rack. The front rack is the huge one. It came off an Azor work bike. Heavy and rated for 50lbs of cargo, it however has a quick mount bracket, and can be removed/mounted in seconds.
Allen is offline   Reply With Quote
Old 05-01-07, 08:39 AM   #14
rivethead147
Junior Member
 
Join Date: May 2007
Bikes:
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
the thing with this build is that you have to consider the geometry of the entire frame before assuming what will be strong. considering the points that are conjoined, the physics of it works out where it really doesn't matter as long as the geometry is proportionate to the rake
rivethead147 is offline   Reply With Quote
Old 05-01-07, 10:37 AM   #15
frameteam2003
Senior Member
 
Join Date: Feb 2005
Location: Pleasanton Tx
Bikes: old,older.and very old
Posts: 1,119
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Curved top tubes begain as a way to lower the seat on bikes built for 28" wheels.This design goes back to 1900 or earler.if you look clost at a cruzer frame the tube does not curve up but drops to lower the seat by an inch or two---makes it easer for kids to ride. Curved seat tubes were used in the 1890s.Paramount,claud butler and others used a curved seat tube to get a very short wheelbase frame
frameteam2003 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 08:17 PM.