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


Go Back   > >

Folding Bikes Discuss the unique features and issues of folding bikes. Also a great place to learn what folding bike will work best for your needs.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 10-27-09, 08:22 PM   #1
ShuSin
Count Cycula
Thread Starter
 
Join Date: Sep 2009
Location: Brooklyn, New York
Bikes: Raleigh 20
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Raleigh Twenty folding bike bent frame - Truing

I found a Raleigh Twenty folding bike on the street one day. I thought it was abandoned because of all the rusty parts, but when i got on it and started pedaling, I noticed i was lopsided on the saddle and steering–well, there was practically no steering. I decided to ride the bike home anyways and, not knowing anything about Twenties, I searched on the net. To make a long story short, I have gotten rid of all the components and basically have two halves of the folder and am determined to fix the seat tube that is bent. I want to bring this ol' fella back to life. So here's the trouble:
The seat tube is bent exactly where the down tube joins it. There's no cosmetic damage to the frame, which leads me to believe that the 'accident' probably impacted the seat post and bent the frame here. If you are not familiar with Twenties, see this pic of an almost-stock Twenty:
http://4.bp.blogspot.com/_CGYQGxEMol...h/PIC-0038.jpg
My frame is bent where you see the cable of this yellow Twenty meet the seat tube, just at the top of the down tube. It is bent away from the chain drive.
Here's the other trouble: in order to bring this bike back to life, I will have to spend quite some cash as this bike appears to be very quirky in its details–quite a challenge for someone inexperienced like me! What that means is I can't take the frame to a frame builder and dish out $$ to true the seat tube, I need to save the $$ for the extinct Shimano BB and Phill Wood rings.

Question: How can I true this tube myself without damaging it? I tried putting it on shims and jumping on it... didn't even make a sound! I am thinking of propping it against a heavy concrete ceiling, shimming both ends, and putting a 2x4 on a car jack and pinning the center of the tube on the other end of the 2x4 and jacking up.
I'd be delighted to hear anything you have to say. This tube is quite stiff and the diameter is about 1.5 in. (the force that bent it must have been tremendous!)
ShuSin is offline   Reply With Quote
Old 10-27-09, 09:05 PM   #2
echotraveler
Senior Member
 
echotraveler's Avatar
 
Join Date: Aug 2009
Bikes:
Posts: 1,799
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
i would suggest that you take some good pics, and post them on the frame builders forum... they will surely help fast.
echotraveler is offline   Reply With Quote
Old 10-28-09, 05:24 AM   #3
griftereck
Senior Member
 
Join Date: Jun 2008
Location: angus scotland
Bikes: Grifter BSA 20
Posts: 600
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Ive not tried to straighten a frame damaged there.

but could try clamping the seat tube in a vice above the down tube. then getting a heavy steel tube thats a tight fit in the bb shell. then heating the area thats bent. Then pushing back on the bb mounted tube.

Youve got to watch as the downtube is brazed on. so dont use to much heat that would melt the brass. The blow torch would wreck the paint job.

Also it would be good if you could check the alignment. Some use bits of string. Others rulers. Ive got a laser line, it shines a red line out of it. Came from the Pound shop, er dollar store.

You can also set out an alignment table. Measure out all the widths of tubing on your bike. Then make wood or metal blocks to the thickness that so that the frame, if straight would lie parralel to the table top. then you can see where and how much the frame needs straightened.

you can see them measuring this mountain bike frame on this video.
http://www.youtube.com/watch?v=jrQqTVV1aBk
griftereck is offline   Reply With Quote
Old 10-28-09, 08:42 AM   #4
rhm
multimodal commuter
 
rhm's Avatar
 
Join Date: Nov 2006
Location: NJ, NYC, LI
Bikes: 1940s Fothergill, 1959 Allegro Special, 1963? Claud Butler Olympic Sprint, Lambert 'Clubman', 1974 Fuji "the Ace", 1976 Holdsworth 650b conversion rando bike, 1983 Trek 720 tourer, 1984 Counterpoint Opus II, 1993 Basso Gap, 2010 Downtube 8h, and...
Posts: 15,563
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I'm not sure I followed your description of the damage, but no matter.

I rather like your car jack idea. I don't like Griftereck's suggestion that you use heat; if you can't do this cold, don't do it. Obviously you have to be careful not to crush any of the tubes. When you are done bending it, expect it to spring back part of the way; the trick will be to correctly guess how much it will spring back. I'd suggest you measure carefully before you start, figure out exactly how much it has to bend, then try bending it. Take careful notes. Measure again while the frame is in the bending press; then let the pressure off and measure again. With care and luck you should be able to figure how much over-bend you need to apply.

By the way, unless the original crank is totally trashed, I'd keep it. Getting a cotterless crank on a Twenty is possible, but it is complicated and (bottom line) not going to save you that much weight.

Oh, one more thing. ShuSin, as in the fourth king of the third dynasty of Ur? WTF?
rhm is offline   Reply With Quote
Old 10-28-09, 09:10 AM   #5
Bacciagalupe
Professional Fuss-Budget
 
Bacciagalupe's Avatar
 
Join Date: Aug 2005
Bikes:
Posts: 6,438
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I don't see the point.

You've got a compromised frame and need to replace a ton of parts. You'd be better off finding another R20 that's in better shape.
Bacciagalupe is offline   Reply With Quote
Old 10-28-09, 10:21 AM   #6
phatatude
Senior Member
 
Join Date: Sep 2007
Location: Put your finger on the middle of a map of the USA... Thats me standing next to the COW:) (the cow is my sister)
Bikes: Schwinn Stingray 5sp, Phillips 20, 24"Dyno GT, Raleigh 20, Scott MTB, and a lot more that I dont want the wife to know about!
Posts: 160
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
It's the thrill of the chase... The story behind the stitches... The one that ALMOST got away ...

What color is your R20?

R20's - If you dont know, you better ask somebody...

Come check the lack of progress
http://web.mac.com/phatatude/Green_S...enty_Blog.html
phatatude is offline   Reply With Quote
Old 10-28-09, 12:04 PM   #7
ShuSin
Count Cycula
Thread Starter
 
Join Date: Sep 2009
Location: Brooklyn, New York
Bikes: Raleigh 20
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by echotraveler View Post
i would suggest that you take some good pics, and post them on the frame builders forum... they will surely help fast.
In fact, they suggested I post here too.
ShuSin is offline   Reply With Quote
Old 10-28-09, 12:06 PM   #8
ShuSin
Count Cycula
Thread Starter
 
Join Date: Sep 2009
Location: Brooklyn, New York
Bikes: Raleigh 20
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by griftereck View Post
Ive not tried to straighten a frame damaged there.

but could try clamping the seat tube in a vice above the down tube. then getting a heavy steel tube thats a tight fit in the bb shell. then heating the area thats bent. Then pushing back on the bb mounted tube.

Youve got to watch as the downtube is brazed on. so dont use to much heat that would melt the brass. The blow torch would wreck the paint job.

Also it would be good if you could check the alignment. Some use bits of string. Others rulers. Ive got a laser line, it shines a red line out of it. Came from the Pound shop, er dollar store.

You can also set out an alignment table. Measure out all the widths of tubing on your bike. Then make wood or metal blocks to the thickness that so that the frame, if straight would lie parralel to the table top. then you can see where and how much the frame needs straightened.

you can see them measuring this mountain bike frame on this video.
http://www.youtube.com/watch?v=jrQqTVV1aBk
I don't trust myself with a torch as I've never used one (perhaps once a long long ago to make crème brûlée)... and most the reason is because of the bend's proximity to the downtube brazing.
ShuSin is offline   Reply With Quote
Old 10-28-09, 12:15 PM   #9
ShuSin
Count Cycula
Thread Starter
 
Join Date: Sep 2009
Location: Brooklyn, New York
Bikes: Raleigh 20
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by rhm View Post
I'm not sure I followed your description of the damage, but no matter.

I rather like your car jack idea. I don't like Griftereck's suggestion that you use heat; if you can't do this cold, don't do it. Obviously you have to be careful not to crush any of the tubes. When you are done bending it, expect it to spring back part of the way; the trick will be to correctly guess how much it will spring back. I'd suggest you measure carefully before you start, figure out exactly how much it has to bend, then try bending it. Take careful notes. Measure again while the frame is in the bending press; then let the pressure off and measure again. With care and luck you should be able to figure how much over-bend you need to apply.

By the way, unless the original crank is totally trashed, I'd keep it. Getting a cotterless crank on a Twenty is possible, but it is complicated and (bottom line) not going to save you that much weight.

Oh, one more thing. ShuSin, as in the fourth king of the third dynasty of Ur? WTF?

rhm, thanks... I think that's what I'll end up doing. Though I'm still not sure what's the best method. I know I can rely on the bottom bracket shell for supporting one end, the other end is the tricky part. The original crank was wrecked as well, I've already ditched it.

hahaha, I didn't make that connection with the king of Sumer and Akkad... but that's a happy coincidence since I'm from the fertile crescent. Actually Shu and Sin are the first three letters of my first and last names.
ShuSin is offline   Reply With Quote
Old 10-28-09, 01:04 PM   #10
ShuSin
Count Cycula
Thread Starter
 
Join Date: Sep 2009
Location: Brooklyn, New York
Bikes: Raleigh 20
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by phatatude View Post
It's the thrill of the chase... The story behind the stitches... The one that ALMOST got away ...

What color is your R20?

R20's - If you dont know, you better ask somebody...

Come check the lack of progress
http://web.mac.com/phatatude/Green_S...enty_Blog.html
That's exactly it, phatatude... and btw, i'm still waiting for your new posts!
ShuSin is offline   Reply With Quote
Old 10-28-09, 01:09 PM   #11
ShuSin
Count Cycula
Thread Starter
 
Join Date: Sep 2009
Location: Brooklyn, New York
Bikes: Raleigh 20
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Bacciagalupe View Post
I don't see the point.

You've got a compromised frame and need to replace a ton of parts. You'd be better off finding another R20 that's in better shape.
How can you explain obsessions? this bent frame stares at me challenging me to fix it... and i'm determined not to go broke in the process. (well, perhaps if i acquire another obsession along the way, say... of getting a campy track hub and building a rear wheel for it.)
ShuSin is offline   Reply With Quote
Old 10-29-09, 12:21 AM   #12
Sirrus Rider
Velocommuter Commando
 
Sirrus Rider's Avatar
 
Join Date: Nov 2007
Location: Houston, Texas
Bikes: '88 Specialized Sirrus, '89 Alpine Monitor Pass, two '70 Raligh Twenties, '07 Schwinn Town & Country Trike, '07 Specialized Sirrus Hybrid
Posts: 2,637
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by ShuSin View Post
How can you explain obsessions? this bent frame stares at me challenging me to fix it... and i'm determined not to go broke in the process. (well, perhaps if i acquire another obsession along the way, say... of getting a campy track hub and building a rear wheel for it.)
If you pull it off it would be one more back from the brink.. Sometimes it's not about the money, but the challenge.
Sirrus Rider is offline   Reply With Quote
Old 11-03-09, 10:04 AM   #13
kraftwerk
my nice bike is at home
 
kraftwerk's Avatar
 
Join Date: Feb 2006
Location: Brooklyn, NY
Bikes: 2011 BMC Race Machine / Colnago ct 1 / 80's Rossin / 90's Merlin/ 70's Raleigh 20/ Swift folder, etc.
Posts: 718
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Steel can be repaired, unlike aluminum which is dodgy to repair and carbon fiber well forget about that...
the R 20 is a frame worth saving.
If you want to build a jig table I have an unbent frame for reference in Brooklyn.
kraftwerk is offline   Reply With Quote
Old 11-07-09, 02:27 PM   #14
ShuSin
Count Cycula
Thread Starter
 
Join Date: Sep 2009
Location: Brooklyn, New York
Bikes: Raleigh 20
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by kraftwerk View Post
Steel can be repaired, unlike aluminum which is dodgy to repair and carbon fiber well forget about that...
the R 20 is a frame worth saving.
If you want to build a jig table I have an unbent frame for reference in Brooklyn.
Thanks. I will keep that in mind. Next weekend I'm going to go around the hood to find a car body shop... they might be willing to take on un-bending this frame for much cheaper than a frame builder might ask for. If nothing comes of that, i've already found a car jack!
ShuSin is offline   Reply With Quote
Old 11-07-09, 03:35 PM   #15
randya
Senior Member
 
randya's Avatar
 
Join Date: Jul 2003
Location: in bed with your mom
Bikes: who cares?
Posts: 13,689
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I once unbent a Columbia 20" mild or hi-ten steel frame that looked like it had been driven over by a car by propping it up on 2x4 blocks and jumping up and down on it, when I was done you couldn't even tell the bike had been damaged. I still have the bike and used it for this year's Mt. Hood bomb.

http://www.youtube.com/watch?v=X7V-q8UX108
randya is offline   Reply With Quote
Old 11-15-09, 11:20 PM   #16
Ya Tu Sabes
Rebel Thousandaire
 
Ya Tu Sabes's Avatar
 
Join Date: Sep 2004
Location: Hartford, CT
Bikes: Public D8, Yuba Mundo (cargo), Novara Buzz (1-speed, soon to be 2-speed w/ a kickback hub), Xootr 1-speed folder
Posts: 733
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
It would be cool if you left the frame then bent a seatpost in such a way as to accommodate for the bent seat tube. I mean, if we're talking about quixotic bike-fixing missions and all . . .
Ya Tu Sabes is offline   Reply With Quote
Old 11-16-09, 09:19 AM   #17
griftereck
Senior Member
 
Join Date: Jun 2008
Location: angus scotland
Bikes: Grifter BSA 20
Posts: 600
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Im thinking of getting rid of all my stuff. Ive got 3 normal R20s. Solid frame, not folding.
But geuss thats no use to you. As I live in Scotland
griftereck is offline   Reply With Quote
Old 11-16-09, 01:39 PM   #18
ShuSin
Count Cycula
Thread Starter
 
Join Date: Sep 2009
Location: Brooklyn, New York
Bikes: Raleigh 20
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by randya View Post
I once unbent a Columbia 20" mild or hi-ten steel frame that looked like it had been driven over by a car by propping it up on 2x4 blocks and jumping up and down on it, when I was done you couldn't even tell the bike had been damaged. I still have the bike and used it for this year's Mt. Hood bomb.

http://www.youtube.com/watch?v=X7V-q8UX108
I successfully did that with my fork steerer for the Twenty, but I'm not going to use it anyways. The frame, however, would not even budge a little. Last night I did unbend it! i will post later with photos to describe. It's pretty satisfying, as you probably know. Cheers.
ShuSin is offline   Reply With Quote
Old 11-16-09, 01:40 PM   #19
ShuSin
Count Cycula
Thread Starter
 
Join Date: Sep 2009
Location: Brooklyn, New York
Bikes: Raleigh 20
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by griftereck View Post
Im thinking of getting rid of all my stuff. Ive got 3 normal R20s. Solid frame, not folding.
But geuss thats no use to you. As I live in Scotland
That would be great to have in the States as they are hard to come by (the non-folding type). But as I mentioned, my obsession is to get this frame trued on my own. I can happily report that I did it last night. I'll write later when I have time with explanations. Cheers.
ShuSin is offline   Reply With Quote
Old 11-16-09, 08:03 PM   #20
stevegor
Senior Member
 
stevegor's Avatar
 
Join Date: Dec 2006
Location: Oz
Bikes: lots... even a Raleigh twenty !!!
Posts: 2,117
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by griftereck View Post
Im thinking of getting rid of all my stuff.
Ive got 3 normal R20s. Solid frame, not folding.
But geuss thats no use to you. As I live in Scotland
That's scary Griftereck, so have I......you wanna be my friend?
stevegor is offline   Reply With Quote
Old 11-17-09, 02:46 PM   #21
griftereck
Senior Member
 
Join Date: Jun 2008
Location: angus scotland
Bikes: Grifter BSA 20
Posts: 600
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Hi Stevegor, you can be my freind.

theres my BSA 20 that I put suspension forks on.
A brown 20. Think its a Raleigh. Its a frameset just now. Got an experimental cartridge BB in it
And a light blue 20 thats a complete standard bike. but rough

I dont want anything for the bikes/ frames. I live in a village near Dundee. So probably too far from anyone that wants them.
Well apart from the kids that stole saddles from my Brittish eagle shopper, an Apollo mtb and my gold bike, last week. Thats sickened me alltogether that I cant leave stuff in my back yard with out it getting stolen.
griftereck is offline   Reply With Quote
Old 11-17-09, 10:19 PM   #22
ShuSin
Count Cycula
Thread Starter
 
Join Date: Sep 2009
Location: Brooklyn, New York
Bikes: Raleigh 20
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
At long last, I did it and I am proud of me. hopefully the images will explain enough. Here's the link:
http://www.flickr.com/photos/1578255...7622827107290/

I just want to add that it was simpler than I thought, but did require plenty of patience. When torquing the jack, i reached a point after which the wood stopped compressing and it became difficult to torque with a screw driver. i proceeded with real caution after that (the first try the 2x3 slipped and hit my left ear and many unpleasant words left my mouth, after which point i put on my bike helmet). After a couple of turns, i began to HEAR the steel bending. It had a crackling sound almost like stepping on broken glass. I didn't have sophisticated measuring tools so I just did it by instinct. I took off the rig and checked after the first go and i was within half a degree of a straight tube. I rigged again and this time I measured. I went 1/8" down and when i lifted the jack, the tube returned about half that amount. And that was it!
ShuSin is offline   Reply With Quote
Old 11-18-09, 07:21 AM   #23
rhm
multimodal commuter
 
rhm's Avatar
 
Join Date: Nov 2006
Location: NJ, NYC, LI
Bikes: 1940s Fothergill, 1959 Allegro Special, 1963? Claud Butler Olympic Sprint, Lambert 'Clubman', 1974 Fuji "the Ace", 1976 Holdsworth 650b conversion rando bike, 1983 Trek 720 tourer, 1984 Counterpoint Opus II, 1993 Basso Gap, 2010 Downtube 8h, and...
Posts: 15,563
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Cool!

I look forward to hearing how the bike rides.
rhm is offline   Reply With Quote
Old 11-18-09, 12:15 PM   #24
Schwinnsta
Schwinnasaur
 
Schwinnsta's Avatar
 
Join Date: Dec 2006
Location: New Orleans, LA
Bikes:
Posts: 562
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Well thought out and executed.
Schwinnsta is offline   Reply With Quote
Old 11-18-09, 03:03 PM   #25
Foldable Two
Senior Member
 
Foldable Two's Avatar
 
Join Date: Aug 2005
Location: Vancouver, Washington and Ocean Shores, Washington, USA
Bikes: 2 - 2007 Custom Bike Fridays, 2 - 2009 Bike Friday Pocket 8's, Gravity 29'er SS, 2 - 8-spd Windsor City Bikes, 1973 Raleigh 20 & a 1964 Schwinn Tiger
Posts: 1,319
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by ShuSin View Post
At long last, I did it and I am proud of me. hopefully the images will explain enough. Here's the link:
http://www.flickr.com/photos/1578255...7622827107290/
Is the rear triangle a little "off" to the right side of the bike? (which would be to the left in your picture with the white line)

Just curious.

You came up with a very simple way to do the needed bending. Like it.

Lou
Foldable Two 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 10:57 PM.