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PostPosted: Mon Nov 05, 2012 9:42 pm 
retrobike rider / Gold Trader
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The kona in your pic is a 2007, the tubes are straight on those. That must have been a massive front crash to bend both top and down tubes like that. Ouch.


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PostPosted: Wed Nov 07, 2012 1:52 pm 
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coomber wrote:
The hydro forming on the full sussers is ...pointless...

Best tell Kona that and they can change it then - thank goodness you realised something a multi-million dollar company with experienced and professional CAD designers didn't! :roll:

The double-S bend on the down tube of the Entourage, for example, gives clearance for the fork crowns on single-crown forks, and clearance for the remote reservoir of the rear shock under full compression, amongst other things.


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PostPosted: Wed Nov 07, 2012 1:54 pm 
retrobike rider / Gold Trader
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gradeAfailure wrote:
coomber wrote:
The hydro forming on the full sussers is ...pointless...

Best tell Kona that and they can change it then - thank goodness you realised something a multi-million dollar company with experienced and professional CAD designers didn't! :roll:

The double-S bend on the down tube of the Entourage, for example, gives clearance for the fork crowns on single-crown forks, and clearance for the remote reservoir of the rear shock under full compression, amongst other things.


:roll:

And what point does the curved top tube add, as rider clearance clearly isnt an issue on them?

If you are going to be pedantic about it, the bend on the down tube is to maximise the contact area in the top and down tube for strength, nothing to do with fork clearance


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PostPosted: Wed Nov 07, 2012 2:38 pm 
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coomber wrote:
gradeAfailure wrote:
coomber wrote:
The hydro forming on the full sussers is ...pointless...

Best tell Kona that and they can change it then - thank goodness you realised something a multi-million dollar company with experienced and professional CAD designers didn't! :roll:

The double-S bend on the down tube of the Entourage, for example, gives clearance for the fork crowns on single-crown forks, and clearance for the remote reservoir of the rear shock under full compression, amongst other things.


:roll:

And what point does the curved top tube add, as rider clearance clearly isnt an issue on them?

If you are going to be pedantic about it, the bend on the down tube is to maximise the contact area in the top and down tube for strength, nothing to do with fork clearance



and if you want to be really pedantic.... the reason it broke is explained in the original post you linked to... :roll: not specifically the tubing itself, more the impact, bend, then continued riding




finnbjorn96 wrote:

the bike in the picture belonged to a friend of mine. the reason it broke like that is because he hit a tree face first with it and it dented inward.
Image
After two weeks of riding it finally broke.


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PostPosted: Wed Nov 07, 2012 3:03 pm 
retrobike rider / Gold Trader
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I give up


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PostPosted: Wed Nov 07, 2012 3:10 pm 
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:lol:
Handbags down you two.... :)


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PostPosted: Wed Nov 07, 2012 3:47 pm 
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Crikey, thought I was on bikeradar with the handbags going on there. :lol:

All about personal opinions guys!

For what its worth, I agree that Kona's engineers must see some merit, but it would be naive to think it is purely about function or a perceived advantage - at the end of the say it is largely about what sells, and bendy frames like those are selling. Whether they are necessary or not is another matter.

Would be interesting to see how the impact that wrote that frame off would have manifested itself in a more traditional shaped/tubed frame.


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PostPosted: Wed Nov 07, 2012 3:50 pm 
retrobike rider / Gold Trader
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No handbags here, im not bothered as I would never buy one :D

I hate the look of them and would be interested to see what an independent engineer would say the merit is of the hydroforming. I guess it would be more style over function.


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PostPosted: Wed Nov 07, 2012 3:53 pm 
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coomber wrote:
No handbags here, ....



Nor here... just being thorough :lol:


G


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PostPosted: Wed Nov 07, 2012 4:00 pm 
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According to Wiki wrote:
Hydroforming is a cost-effective way of shaping ductile metals such as aluminum, brass, low alloy steels, stainless steel into lightweight, structurally stiff and strong pieces. One of the largest applications of hydroforming is the automotive industry, which makes use of the complex shapes possible by hydroforming to produce stronger, lighter, and more rigid unibody structures for vehicles. This technique is particularly popular with the high-end sports car industry and is also frequently employed in the shaping of aluminium tubes for bicycle frames. Hydroforming is a specialized type of die forming that uses a high pressure hydraulic fluid to press room temperature working material into a die. To hydroform aluminum into a vehicle's frame rail, a hollow tube of aluminum is placed inside a negative mold that has the shape of the desired result. High pressure hydraulic pumps then inject fluid at very high pressure inside the aluminum which causes it to expand until it matches the mold. The hydroformed aluminum is then removed from the mold. Hydroforming allows complex shapes with concavities to be formed, which would be difficult or impossible with standard solid die stamping. Hydroformed parts can often be made with a higher stiffness-to-weight ratio and at a lower per unit cost than traditional stamped or stamped and welded parts. Virtually all metals capable of cold forming can be hydroformed, including aluminum, brass, carbon and stainless steel, copper, and high strength alloys


Reading this, the advantages, and therefore reasons why it would be used is clear.... Cheap, strong, light, complex shapes, high stiff/weight ratio (steady.... :wink: ), although not necessarily prioritised in that order



G


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