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


Go Back   > >

Recumbent What IS that thing?! Recumbents may be odd looking, but they have many advantages over a "wedgie" bicycle. Discuss the in's and out's recumbent lifestyle in the recumbent forum.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 07-12-11, 01:21 PM   #1
PaPa
Senior Member
Thread Starter
 
PaPa's Avatar
 
Join Date: May 2003
Location: Idaho
Bikes:
Posts: 493
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Sub 18 Pound SWB... in Steel?

Maybe.

One glance, and the observant 'bent homebuider will immediately recognize the potential here. It is a Haro Comp Extreme, The frame is TIG welded, Tange, double butted tubing with a bare frame weight of 2659g.



After a litle selective surgery, I was able to trim-off 1593g. As shown below, (with chunky, 57-406 rubber, wide rims and a 950g fork), it weights 5366g (approx. 11.8 pounds)

PaPa is offline   Reply With Quote
Old 07-12-11, 03:41 PM   #2
AlexZ
Senior Member
 
Join Date: Jun 2009
Location: Huntington Beach
Bikes:
Posts: 492
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
You have cut away a triangulated truss structure and left a tube that will have to work in bending, as it was never intended to work!
Potential?! Oh Yeah! Potential for disaster.....and much pain!

The next step should be the trash bin! Recycled please......

Last edited by AlexZ; 07-12-11 at 03:45 PM.
AlexZ is offline   Reply With Quote
Old 07-12-11, 05:36 PM   #3
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)
I'd also have to say that it's gonna be way too flexy. -At least, for most typical-sized adults.

And did you cut off the top half of the head tube? You need to have the head tube ends cut perfectly squared to get the head tube bearings to work well....
Doug5150 is offline   Reply With Quote
Old 07-12-11, 05:44 PM   #4
PaPa
Senior Member
Thread Starter
 
PaPa's Avatar
 
Join Date: May 2003
Location: Idaho
Bikes:
Posts: 493
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by AlexZ View Post
You have cut away a triangulated truss structure and left a tube that will have to work in bending, as it was never intended to work!
Potential?! Oh Yeah! Potential for disaster.....and much pain!

The next step should be the trash bin! Recycled please......
Interesting observation. Are you
a builder?

Since you failed to ask necessary specifics to make that assumption - i.e. tubing diameter, wall thickness, span length, rider weight and static and dynamic loading location, predicted torsional moments along its span, and CoM location, I'll assume the answer is NO.
PaPa is offline   Reply With Quote
Old 07-12-11, 05:54 PM   #5
Steamer
Senior Member
 
Steamer's Avatar
 
Join Date: Nov 2008
Location: high ground
Bikes:
Posts: 781
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
It will be great! Please continue.... and let us know how it turns out!
Steamer is offline   Reply With Quote
Old 07-12-11, 06:17 PM   #6
PaPa
Senior Member
Thread Starter
 
PaPa's Avatar
 
Join Date: May 2003
Location: Idaho
Bikes:
Posts: 493
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Doug5150 View Post
And did you cut off the top half of the head tube? You need to have the head tube ends cut perfectly squared to get the head tube bearings to work well....
I rough-cut the HT length, then made a few finish passes on a Bridgeport Series I vertical mill. The ends are within .001" of parallel. Will that do?
PaPa is offline   Reply With Quote
Old 07-12-11, 07:16 PM   #7
BlazingPedals
Senior Member
 
BlazingPedals's Avatar
 
Join Date: Dec 2004
Location: Middle of da Mitten
Bikes: Trek 7500, RANS V-Rex, Optima Baron, Velokraft NoCom, M-5 Carbon Highracer, homebuilt recumbent
Posts: 8,944
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 103 Post(s)
I would not want to ride a monotube with such a small diameter main tube. What is it - 1 1/8"? At my weight, I would probably have the frame bent within a week, assuming I could even keep it on the road while powering it up to cruising speed. But, maybe it will work for you. I hope it turns out; your bikes always look so nice.
BlazingPedals is offline   Reply With Quote
Old 07-12-11, 09:15 PM   #8
AlexZ
Senior Member
 
Join Date: Jun 2009
Location: Huntington Beach
Bikes:
Posts: 492
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by PaPa View Post
Interesting observation. Are you
a builder?

Since you failed to ask necessary specifics to make that assumption - i.e. tubing diameter, wall thickness, span length, rider weight and static and dynamic loading location, predicted torsional moments along its span, and CoM location, I'll assume the answer is NO.
Your assumption is correct...I am however a structural engineer . Not to confuse you further, but double butted tubes work great in tension and even compression but are next to worthless in bending! Avoid disappointment and injury......visit the dumpster....
AlexZ is offline   Reply With Quote
Old 07-12-11, 11:59 PM   #9
PaPa
Senior Member
Thread Starter
 
PaPa's Avatar
 
Join Date: May 2003
Location: Idaho
Bikes:
Posts: 493
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by AlexZ View Post
Your assumption is correct...I am however a structural engineer . Not to confuse you further, but double butted tubes work great in tension and even compression but are next to worthless in bending! Avoid disappointment and injury......visit the dumpster....
I'm really not interested in your haphazard supposition. So... either provide me with accurate FMEA data to substantiate your claims, or find another thread.
PaPa is offline   Reply With Quote
Old 07-13-11, 03:17 PM   #10
Mr Gnome
Senior Member
 
Join Date: Mar 2010
Location: Cape Coral, FL
Bikes: Sun X3-SX recumbent trike
Posts: 102
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
It Looks Good "FROM WHERE I'M SITTING!!!"

Quote:
will immediately recognize the potential here.
Mr Gnome is offline   Reply With Quote
Old 07-13-11, 06:00 PM   #11
rodar y rodar
weirdo
 
Join Date: Jan 2008
Location: Reno, NV
Bikes:
Posts: 1,962
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
From what I`ve read from you before, I`m surprised to see you working on a short bike. It does look like an interresting project though- sure hope you keep the build thread updated. I don`t see how you`re going to manage the steerer. Will you make a new fork, or do you have a way to extend the threads?
rodar y rodar is offline   Reply With Quote
Old 07-13-11, 07:34 PM   #12
gcottay
Senior Member
 
gcottay's Avatar
 
Join Date: Jul 2007
Location: Green Valley AZ
Bikes: Trice Q; Volae Century; TT 3.4
Posts: 3,772
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Are you planning on a MBB?
gcottay is offline   Reply With Quote
Old 07-14-11, 03:14 AM   #13
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)
screw it...build it, and let us know how it gets on !
gavtatu is offline   Reply With Quote
Old 07-14-11, 09:36 AM   #14
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)
Quote:
Originally Posted by PaPa View Post
I rough-cut the HT length, then made a few finish passes on a Bridgeport Series I vertical mill. The ends are within .001" of parallel. Will that do?
Well, I'd have cut them to .00001", but that's probably good enough.

It's still too thin though. The seatstays I'm not sure, but the main tube, almost certainly.
And you have cut the head tube shorter than any commercial bicycle manufacturer is willing to.

Good luck.
Doug5150 is offline   Reply With Quote
Old 07-14-11, 02:47 PM   #15
PaPa
Senior Member
Thread Starter
 
PaPa's Avatar
 
Join Date: May 2003
Location: Idaho
Bikes:
Posts: 493
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by rodar y rodar View Post
From what I`ve read from you before, I`m surprised to see you working on a short bike.
Yes, me too. The build is for someone else, and I decided to experiment.

Quote:
Originally Posted by rodar y rodar View Post
I don`t see how you`re going to manage the steerer. Will you make a new fork, or do you have a way to extend the threads?
I'll probably use a threadless and the steerer will be telescoped and clamped - my common fix.

Quote:
Originally Posted by gcottay View Post
Are you planning on a MBB?
Nope.

Quote:
Originally Posted by Doug5150 View Post
It's still too thin though. The seatstays I'm not sure, but the main tube, almost certainly.
Seems nearly everyone is 'assuming' I'll built the frame as shown above. There'll be structural changes alright, but most won't be visible.

Quote:
Originally Posted by Doug5150 View Post
And you have cut the head tube shorter than any commercial bicycle manufacturer is willing to.
That won't be a problem - the steer tube is 1.25" OD and if you look closely at the image, you'll see a factory gusset at the lower HT/main tube joint - much like a BMX.

Last edited by PaPa; 07-14-11 at 03:00 PM.
PaPa is offline   Reply With Quote
Old 07-15-11, 06:03 AM   #16
charly17201
Senior Member
 
charly17201's Avatar
 
Join Date: Jan 2008
Location: Tulsa
Bikes: RANS Formula LE, Giant Escape 1
Posts: 583
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Heck, I'm just interested in the final product and your pics. Sub-18 lbs in CrMo could be revolutionary if successful for the 'bent riders.

After cost, weight and perceived 'slowness' due to weight is probably the biggest detractor to the non-bent rider.
charly17201 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 07:42 PM.