Danger of this frame modification?
03-06-05, 08:10 AM
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my friend has a cheapo wallmart bike thing that he wants to mess around with. he's thinking about removing the seat tube and just having the thinner white tubes support the weight. he's also thinking about modifying the fender to support the rear of the bike. but all in all, is this a bad idea for him to be removing that seat tube?? im thinking its a bad idea, but thoughts from people in the know would be appreciated.
03-06-05, 08:51 AM
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I'm no engineer, but I suspect the frame will collapse under his weight if he cuts out most of the seat tube (i.e., between the bottom bracket and the top tube). The seat stays just aren't designed to carry that much load.
03-06-05, 06:51 PM
#8
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The frame is made of not so resilient low carbon steel. It will be weak at best, since the frame is designed to have the seat tube be the load bearing member. With it not there, the trussing of the remaining tubes will kink most likely and at the very least the seat will have no lateral stability. Not a wise idea.
03-06-05, 08:08 PM
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03-06-05, 09:29 PM
#10
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That is in my opinion not an acurate comparison. The bike in your example uses a smaller frame and an axle-supported banana seat. On the beach cruiser sized frame there are much longer runs of tubing for flex to affect.
03-06-05, 11:39 PM
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Originally Posted by modmon
im thinking its a bad idea, but thoughts from people in the know would be appreciated.
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03-06-05, 11:42 PM
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Put pivot points at the top tubes, then remove the seat tube and replace it with a shock...
What is that guy smoking?
What is that guy smoking?
03-06-05, 11:44 PM
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Originally Posted by slvoid
Put pivot points at the top tubes, then remove the seat tube and replace it with a shock...
What is that guy smoking?
What is that guy smoking?
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03-07-05, 12:04 AM
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GAARRR! My eyes...
Ignoring the ride quality, why do people even buy bikes that look like that? They're so darn ugly. What's with the curved tubes and loopy white thingies?
I guess I'm a stickler for form-follows-function. I like a pretty bike, but I like to see that every physical feature is there for a purpose too.
Ignoring the ride quality, why do people even buy bikes that look like that? They're so darn ugly. What's with the curved tubes and loopy white thingies?
I guess I'm a stickler for form-follows-function. I like a pretty bike, but I like to see that every physical feature is there for a purpose too.
03-07-05, 08:46 AM
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Do it anyway, it will be funny when it breaks. Then post pictures.
03-07-05, 10:43 AM
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And you people think I'M crazy? 
03-07-05, 11:15 AM
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Originally Posted by CdCf
And you people think I'M crazy?
I'm gonna downgrade you to eccentric. This guy is trying to remove major structural elements of his bike. Freakin' nuts.
03-07-05, 08:27 PM
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Give it a try. Kestrel has been doing it for years and their bikes are hot sellers:https://www.kestrel-usa.com/bikes/airfoil.php
03-07-05, 08:59 PM
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Originally Posted by Sprocket Man
Give it a try. Kestrel has been doing it for years and their bikes are hot sellers:https://www.kestrel-usa.com/bikes/airfoil.php
I'm not sure that Walmart has designed their bikes for de-seattubification.
03-07-05, 09:31 PM
#21
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The lefty fork is almost exactly like what aircraft have been using for decades, so that has the least of the worries in my book. The real designs have a set target and they engineered all elements to reach it with a margin. The walmart bikes are made to be just strong enough to not break under normal loads. Name of thier game is low cost. There are few mods I would consider to a walmart, most of the time are bracing, not deleting...
03-08-05, 12:16 AM
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Originally Posted by CdCf
And you people think I'M crazy?
CdCf I will say this much at least you have a somewhat understandable reason for some of your ideas. You don't just do things because you think they "look cool"
Originally Posted by mtbikerinpa
The lefty fork is almost exactly like what aircraft have been using for decades, so that has the least of the worries in my book.
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03-08-05, 12:58 AM
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Originally Posted by Raiyn
I trust Aircraft engineers a lot further than I do the folk at "Crack-n-Fail" but that's me
03-08-05, 02:00 AM
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He should start making mods on his new wheelchair too!
Originally Posted by modmon
my friend has a cheapo wallmart bike thing that he wants to mess around with. he's thinking about removing the seat tube and just having the thinner white tubes support the weight. he's also thinking about modifying the fender to support the rear of the bike. but all in all, is this a bad idea for him to be removing that seat tube?? im thinking its a bad idea, but thoughts from people in the know would be appreciated.
03-08-05, 02:11 AM
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Originally Posted by ultra-g
He should start making mods on his new wheelchair too!
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