Kai-ming's kitchen

Discuss light weight issues concerning road bikes & parts.
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kai-ming
Posts: 97
Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

To avoid the unnecessary flaming/provocation laugh that I have received at the recent thread of Shaving material off heavy rim, I list herewith statements to disclaim my responsibility of flaming that might arouse:-
1. I could be new to all of you and I understand my User name is not presentable under European's eyes, however, I am proud of being a Hong Kong Chinese.
2. I am a qualified engineer with B Sc Second Class Honours (1st Division) in Mechanical Engineering from UK, Chartered Engineer for decades. So please equip yourself with the necessary basic engineering knowledge before you open-fire/start the flaming.
3. I will try to be humble and polite to answer any question. However, if I sense provocation of a fight, there is no guarantee that I do not fight back similar to my responses at the above thread.
:mrgreen:
This is my original design of a tuned seat post, how it works is quite similar to recent pencil thin seat stay design aiming to make the seat post/seat tube under controllable flex. Feel free to copy the design and implement into your products if you think it is a good idea, all I am asking is to name the design ''Kai-ming's seatpost''.
:lol:

Image
Image
That is a 27.2mm carbon seatpost with 27.2/31.6mm sleeves fixed to the post permanently (but can be removed easily). The lower sleeve is screwed to the post end while the upper sleeve is AA glued/Epoxy to the post which can be easily debonded by placing a big flat screw driver at the cut slot and turn. I have had problem of slippage of seatpost in carbon frame set, turning the collar too tight might damage the expensive frame set. There is no slippage any more + lower torque at the collar, i.e. a lighter/weaker collar will do the job. Grease can be put at the sleeve/frame interface, so no worry on the fused seatpost/frame problem.
These holes on the seatpost are mainly for making the section flexible which will bend inside the seat tube of the frame under the load of a rider, reduced weight is just icing on the cake.
The post is lighter than any post that I have ever own. :P

HillRPete
Posts: 2292
Joined: Tue Apr 12, 2011 8:08 am
Location: Pedal Square

by HillRPete

Nice work.
Not sure if your request to for naming is serious, but people have done this before.

http://www.flickr.com/photos/phorsus/6257388080/
http://sfgfc.wordpress.com/2008/05/02/c ... -seatpost/
... many more ...
Last edited by HillRPete on Fri Aug 10, 2012 1:21 pm, edited 1 time in total.

by Weenie


crohnsy
Posts: 439
Joined: Mon Aug 16, 2010 6:43 pm
Location: Canada

by crohnsy

You need to post scale pics. Please quantify how much weight you saved in this configuration....

:thumbup: :smartass:

kai-ming
Posts: 97
Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

wassertreter wrote:Nice work.
Not sure if your request to for naming is serious, but people have done this before.

http://www.flickr.com/photos/phorsus/6257388080/" onclick="window.open(this.href);return false;
http://sfgfc.wordpress.com/2008/05/02/c ... -seatpost/" onclick="window.open(this.href);return false;
... many more ...


It appears that you misunderstand the basic design concept.

kai-ming
Posts: 97
Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

crohnsy wrote:You need to post scale pics. Please quantify how much weight you saved in this configuration....

:thumbup: :smartass:


I forgot :noidea: , reduced weight is of secondary importance. :smartass:

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ergott
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Joined: Tue Apr 18, 2006 3:03 am
Location: Islip, NY
Contact:

by ergott

Wouldn't you have saved more weight if you just cut 2" below the top collar? You have a lot of extra seatpost in the frame.


edit. Nevermind, I see what you are trying to do.

Do you have any way of evaluating just how much "flex" you gained with this?

kai-ming
Posts: 97
Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

ergott wrote:....
Do you have any way of evaluating just how much "flex" you gained with this?


By riding it with high pressure tires on poor road surface. The flex can be further tuned by increase/decrease the length of the upper collar and/or making the flex section more flexible by drilling with engineering sense.

kai-ming
Posts: 97
Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

kai-ming wrote:
ergott wrote:....
Do you have any way of evaluating just how much "flex" you gained with this?


By riding it with high pressure tires on poor road surface. The flex can be further tuned by increase/decrease the length of the upper collar and/or making the flex section more flexible by drilling with engineering sense.


p.s. Do I deserve the naming of the design? :oops: I honestly wish to get comments, good or bad, from your (all of you) heart. :hello:
Last edited by kai-ming on Fri Aug 10, 2012 2:44 pm, edited 4 times in total.

crohnsy
Posts: 439
Joined: Mon Aug 16, 2010 6:43 pm
Location: Canada

by crohnsy

kai-ming wrote:
crohnsy wrote:You need to post scale pics. Please quantify how much weight you saved in this configuration....

:thumbup: :smartass:


I forgot :noidea: , reduced weight is of secondary importance. :smartass:



Then quantify the amount of flex you are getting please. You are an engineer please provide data to validate your claims

kai-ming
Posts: 97
Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

crohnsy wrote:
kai-ming wrote:
crohnsy wrote:You need to post scale pics. Please quantify how much weight you saved in this configuration....

:thumbup: :smartass:


I forgot :noidea: , reduced weight is of secondary importance. :smartass:



Then quantify the amount of flex you are getting please. You are an engineer please provide data to validate your claims

I didn't bother to do tests to get the flex data. By tuning with the above methods the ride on rough road with high tire pressure is so..so much smoother when seated.

motorthings
Posts: 336
Joined: Mon Nov 17, 2008 9:56 pm

by motorthings

The SOTP method of testing, excellent!

kai-ming
Posts: 97
Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

motorthings wrote:The SOTP method of testing, excellent!

Please explain SOTP. :noidea:

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prendrefeu
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Location: Los Feliz, Los Angeles, California
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by prendrefeu

Seat Of The Pants.
Exp001 || Other projects in the works.

kai-ming
Posts: 97
Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

Yes,and NO (if you mean to do something difficult without the necessary experience or ability). With educated/trained engineering sense, mind you, this is a concept design.
Last edited by kai-ming on Fri Aug 10, 2012 3:39 pm, edited 1 time in total.

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Craigagogo
Posts: 379
Joined: Sun Jul 18, 2004 1:10 pm
Location: Ontario, Canada

by Craigagogo

To take your idea another step further...

Support the post at the clamp as you have done but have no support at the end of the seat post.

Now you would have a cantilevered beam @ the seat which resist the bending moment that is supported rigidly at the clamp and intermittently at the end of the post in the frame.

This allows for large deflection of seat for the first 2.0 +/- mm of movement at the lower end of the seat post. Then as the first 2.0 mm of lower post deflection is observed, secondary flexing due to the further deflection of the seat post that is supported between contact with the frame and at the clamp. You could tune this effect with an elastomer at the base of the seat post.
More than 10 years a Weenie!

by Weenie


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