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Old 05-09-2010, 06:53 PM   #16
Lornce
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That's a brilliant effort.

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Old 05-09-2010, 09:14 PM   #17
TX Ryder
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I wish along with the last name, that I also shared Paul's skills. That's some incredible craftmanship he's done, topnotch stuff! Thanks for posting the pics.
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Old 05-10-2010, 01:16 AM   #18
igormortis
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Wow. And it still looks like an Airhead.

How do you guys in Oz register something like that for road use? i.e. an entirely new frame?
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Old 05-10-2010, 06:08 PM   #19
Beemerboff
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He doest seem to see any benifit it triangulation, so I imagine there wont be many other frame designers who see much merit in the design.

It also looks like it is intended that the engine /gearbox is a stressed member, but a quick look at BMWs method of attaching the box to the engine will tell you that it was never intended for that purpose.

Fork angle looks a bit steeper than normal for a offroad bike too.

Leaves me cold, but there is no accounting for taste , I suppose.
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Old 05-10-2010, 07:15 PM   #20
Lornce
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Quote:
Originally Posted by Beemerboff
He doest seem to see any benifit it triangulation, so I imagine there wont be many other frame designers who see much merit in the design.

It also looks like it is intended that the engine /gearbox is a stressed member, but a quick look at BMWs method of attaching the box to the engine will tell you that it was never intended for that purpose.

Fork angle looks a bit steeper than normal for a offroad bike too.

Leaves me cold, but there is no accounting for taste , I suppose.


Box sections are all about cross sectional area. Make no mistake, that frame's hell for strong. The triangulated box section near the swingarm pivot points will be far stiffer than it'd ever need to be to resist any flexing that could ever be produced by those two tire contact patches.

Stressed member transmission? Wrong again. The engine's held in place, and becomes a bit of a stressed member by virtue of it's shape, though it bears no chassis load. The trans is bolted to the motor, just like a stock airhead.

Steering geometry appears to be a bit steeper than maybe BMW standards, but well within acceptable norms from manufacturers that build offroad bikes that actually handle well.

That's three for three.

You have any opinions founded in substantive reason?

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Old 05-10-2010, 08:05 PM   #21
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'boff, you may not have bumped into Pauls work before but he's a very well respected bike builder over this side of the pond, easily in the same league as companies like HPN, only he's small time and a lot easier to approach. He's got a very long racing background as well, so he knows his stuff. As you can see by Pezz's response, he's placed an order for one of these frames sight unseen, thats how much faith people place in this guy. I personally have had a fair few dealings with him when i built up my Ducati Dirt bike, he rebuilt the suspension and advised on the new geometry that i added to the bike, some of what he told me to do didn't seem to make sense at the time but i just did as i was told (grudgingly) and i'm glad i did, It rides like cadillac on the dirt, a testament to how much this guy knows.
Okay enough pissing in Pauls pocket, back to the show........
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Old 05-11-2010, 08:16 AM   #22
Beemerboff
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It isnt instantly clear were the shock is mounted , but what triangulation there is seems to be seems to be holding up the seat.

Sure a big heavy box section can be made stiff, but a well designed triangulated frame can be made lighter and stiffer. And there is a large unbraced length over the top of the engine - remember that deflection is a hyperbolic function of of the length, that is, a long tube will deflect a lot more than one half the length. So for the same stiffness needs it to be a lot stronger.

The steering head looks strangely unsupported too.

But as a qualified structural engineer I am probably looking at it from a different viewpoint to you.

If the engine is not used as a stressed member that is as it should be, but then the top tube simply doest look up to the job.

But handsome is as handsome does, and there have been some weird looking frames which defied all sense and logic and performed quite well - perhaps this will be one of them.
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Old 05-11-2010, 08:31 AM   #23
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Quote:
Originally Posted by Beemerboff
It isnt instantly clear were the shock is mounted ,
Check prev page.
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Old 05-11-2010, 09:31 AM   #24
Lornce
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Quote:
Originally Posted by Beemerboff
It isnt instantly clear were the shock is mounted , but what triangulation there is seems to be seems to be holding up the seat.

Sure a big heavy box section can be made stiff, but a well designed triangulated frame can be made lighter and stiffer. And there is a large unbraced length over the top of the engine - remember that deflection is a hyperbolic function of of the length, that is, a long tube will deflect a lot more than one half the length. So for the same stiffness needs it to be a lot stronger.

The steering head looks strangely unsupported too.

But as a qualified structural engineer I am probably looking at it from a different viewpoint to you.

If the engine is not used as a stressed member that is as it should be, but then the top tube simply doest look up to the job.

But handsome is as handsome does, and there have been some weird looking frames which defied all sense and logic and performed quite well - perhaps this will be one of them.
The top shock mount's clearly visible in the view I posted above.

Apparently this bike's lighter than a stocker. ie. he appears to have met the design goals of increased strength and reduced weight.

That box section backbone isn't going to flex. I'm just a guy with a bit of practical experience in fabrication and design. I'm not worried about that structure giving up much in the way of distortion and deflection. You're the structural engineer: Run the numbers.

As regards your other comments, you're either a troll or a pompous fool.

As we say in the trades "If it wasn't for engineers, we'd all be out of work."

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Old 05-11-2010, 09:36 AM   #25
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Old 05-11-2010, 05:40 PM   #26
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Quote:
Originally Posted by Lornce

As regards your other comments, you're either a troll or a pompous fool.



Beemerboffs niether of these.

Grumpy old man with some ideas that are refreshingly outside the square yes.
Not impressed by fashion or popular opinion, yes.
Able to be pursuaded to consider alternate viewpoints, sometimes.
Pursuaded to change his opinion, only if presented with evidence.

I've seen some good looking pics of a frame that looks like it would be stiffer than the standard rubber item but a stiff G/S under 183kg wet is achievable with a conventional reinforced frame so I can't say I've seen any "evidence" but I sure am impressed by and interested in Pauls work.

I'll be watching to see what MkII, III & IV versions evolove into.
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Rucksta screwed with this post 05-11-2010 at 05:45 PM
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Old 05-11-2010, 07:38 PM   #27
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Quote:
Originally Posted by Beemerboff
And there is a large unbraced length over the top of the engine - remember that deflection is a hyperbolic function of of the length, that is, a long tube will deflect a lot more than one half the length. So for the same stiffness needs it to be a lot stronger.

The steering head looks strangely unsupported too.
I think you have to listen to peoples opinnions , you never know you just may learn something, so in that spirit 'boff i'd like to understand this a bit better.
I'm assuming that the part you're talking about is the area forward of the front mount as the frame to the rear of that is braced using the engine as part of the frame structure, tieing into it at the top, then lower down the frame where i assume the gearbox bolts to the engine, as well as underneath it, so by rights the frame should be very strong from this area back? So on the "front" section, it is relatively short so it should fall into what you say about a short box section being stronger/stiffer than a long length? Plus the triangular piece under the headstem, isn't that strong enough to support the deflection etc caused here by the front wheel hitting a large bump or whatever? Do you think that the headstem would be better with an extra support gusset on top between the headstem and the frame?
Cheers
Bill
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Old 05-12-2010, 01:05 AM   #28
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Just rang Chris, to ask him how it rides. "Bloody awesome mate!"
I guess that's what matters in the end, huh?
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Old 05-12-2010, 03:11 AM   #29
Phreaky Phil
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Wonder how much $ for a frame ?
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Old 05-12-2010, 03:54 AM   #30
Steve in NZ
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Kiwi style

Quote:
Originally Posted by Phreaky Phil
Wonder how much $ for a frame ?
I certain ya could cobble somehing up Phil. Just to be carbon neutral how about doing it out of "Pine".

I think the woodgrain frame would look super
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