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


Go Back   > >

Alt Bike Culture Chopped, dropped, stretched, lifted, and otherwise cut up and put back together. The art and science of choppers, cruisers, lowriders and the vast world of mutant bicycles.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 10-20-10, 08:15 AM   #1
d87
Junior Member
Thread Starter
 
Join Date: Sep 2010
Bikes:
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Would this work?..

I have this idea where I take a large piece of balsa wood or dense foam and carve it into the shape of a monocoque frame, like the lotus bike or Graeme Obrees whip.

Then when I have the carved shape I wrap it in carbon in the traditional way using decent epoxy and cloth.

Would this work as a way to build a bike? would the balsa or foam make the ride softer and help take some of the load on the frame. Would the wood change shape inside the frame over time?

Would the added weight of the balsa or foam be a real hindrance?

Any thoughts are more then welcome.

Cheers
d87 is offline   Reply With Quote
Old 10-22-10, 04:38 AM   #2
gavtatu
Senior Member
 
gavtatu's Avatar
 
Join Date: Oct 2008
Location: the original jersey
Bikes: lowracer, highracer, moving bottom bracket, 2 tall bikesl
Posts: 286
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
try the recumbent forum, or bentrideronline, homebuilders, lots of CF frames going on there !
gavtatu is offline   Reply With Quote
Old 10-23-10, 12:18 PM   #3
StephenH
Uber Goober
 
StephenH's Avatar
 
Join Date: Sep 2007
Location: Dallas area, Texas
Bikes:
Posts: 11,286
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 22 Post(s)
I'm sure it would work. Compared to more traditional ways, I see two issues: 1) A slight bit of extra weight, which wouldn't be an issue except that the main purpose of using carbon fiber is to avoid extra weight. 2) At various places, you need cavities in the frame for seatposts, cranks, fork, and stuff like that, and if the cavity is filled with balsa wood, you have a problem.

It seems to me, though, that carbon fiber would be a poor material to experiment with like that. You'd have an awful lot of time and trouble in building the frame, but would pretty much be guessing on the design. Get a bit too stout, and it's also too heavy. Have a minor defiicency, and you have a cracked frame.
__________________
"be careful this rando stuff is addictive and dan's the 'pusher'."
StephenH is offline   Reply With Quote
Old 10-23-10, 08:53 PM   #4
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)
There are instructions on the web for this type of build.Foam is best as it can be desolived and the frame left hollow.
frameteam2003 is offline   Reply With Quote
Old 10-24-10, 01:06 PM   #5
Doug5150
Senior Member
 
Join Date: May 2005
Location: IL-USA
Bikes:
Posts: 1,661
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Using foam or lightweight wood will work for composite molding. Many DIY-ers use balsa wood since (if you are doing long/spindly pieces) it is more rigid than foam would be, it is pretty easy to buy and it still doesn't weigh much.

The wood inside isn't for strength though, it's just for winding the composite layers over. There's no reason to use thick enough wood to separately support the load, since the wood breaks about as easily as the composite will. If you bent the frame far enough to crack the composite, the wood will already be cracked too.

-------

The "real" way to add catastrophic-safety reinforcement to composites is you alternate in layers of kevlar, such as,,, for a three-layer covering, use two layers of carbon (or graphite) with one layer of kevlar in the middle. The carbon/graphite will snap off clean if bent too far, but the kevlar stays "stringy" and tough, and will hold the pieces together if the epoxy and carbon cracks.

Also--do not use chopped-strand mat, use ONLY woven mat or unidirectional tape.
The chopped-strand mat is cheaper, but is not nearly as strong and doesn't saturate well.
~
Doug5150 is offline   Reply With Quote
Old 07-12-13, 10:17 AM   #6
zappdog
Newbie
 
zappdog's Avatar
 
Join Date: Jul 2013
Location: Calgary Ab.
Bikes:
Posts: 2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
For those that are thinking of this type of frame build, it will work. I built a balsa and fiberglass mountain bike frame http://unclezapaudiozap.freeforums.o...t875.html#p875
It is the stiffest frame I have ridden and worked out quite nice. The post has full details on the whole build including a couple of mistakes I made. Worth a read.
The balsa wood was more than strong enough to ride before the single layer of fiberglass. Weight is a bit less than the aluminum frame it replaced.


Quote:
Originally Posted by d87 View Post
I have this idea where I take a large piece of balsa wood or dense foam and carve it into the shape of a monocoque frame, like the lotus bike or Graeme Obrees whip.

Then when I have the carved shape I wrap it in carbon in the traditional way using decent epoxy and cloth.

Would this work as a way to build a bike? would the balsa or foam make the ride softer and help take some of the load on the frame. Would the wood change shape inside the frame over time?

Would the added weight of the balsa or foam be a real hindrance?

Any thoughts are more then welcome.

Cheers
Attached Images
File Type: jpg IMG_0120.jpg (89.2 KB, 22 views)

Last edited by zappdog; 06-28-15 at 02:32 PM.
zappdog 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 03:53 AM.