Rooney Special Airhead GS Race Frame

'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........

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.

Check prev page.

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."

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.

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

Just rang Chris, to ask him how it rides. "Bloody awesome mate!"
I guess that's what matters in the end, huh?

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

Good call Bill...I'd be interested as well.

I certainly understand Boff's call and I understand the engineers perspective (don't very often agree though!).

Looking at the frame, it seems to be 50mm square tube that'd be around 1.5 to 2mm wall thickness, so it's got reasonable strength in itself.

To me it looks like about 75mm of unsupported main frame from the engine supports to the underside gussets for the steering head. The steering head looks something like steam pipe, so will have enormous strength in its own right.

To me...it looks incredibly strong. Funny thing is, most bikes handle best when there's more flexibility in the frame!!

It's also worth noting that what science says should be the best bike, very rarely is. Look at the time and R&D that goes into MotoGP...especially Honda, who have tried using the technical engineers to design bikes and they've mostly all been total disasters.

The telling is in the riding / handling - not so much in weather it's built to engineering science

Obviously just my opinion.

Cheers...Mark

Thanks Rucksta - I usually drop straight on as soon as a topic degenerates into personal abuse , but I may as well stay in this one.

I was looking at the last few pics of the latest version of the frame - and I should have back tracked to the pics of the earlier version of the frame in a complete bike which shows the shock mount.

Olddog , we have already been informed by the exceptionally well informed Lornce that the engine takes no part of the chassis load, and if we accept that then the entire length of the top tube can be considered unsupported, and if frame terms that is a long unsupported length.
But more importantly one with a major concentration of stress the last few centimeters at either end.
And IMHO , a structure is better designed where every member carries a equal load , with no concentration of stress.
And that simple obseervation was as much as I said in my first post.

I did say that iI have an engineering qualification, but that was gained 50 years ago when it was the only qualification availible to you in the fabrication and construction industry.
I have always worked in the construction industry, these days as a' Design Manager" redesigning and re quoting the rubbish that has been coming out out of so called professional engineers offices since CAD replaced knowledge , skill and hands on experience. And thinking outside of the square and not buckling to the conventional wisdom are a essential part of the job.
And make no mistake , I get the same sort of abuse from irate engineers I get for my views on some aspects of motorcycling.

So jibes at the engineering profession are misdirected - no one abusing the ability of the current crop of design engineers will get any argument from me.

My background in bikes goes back to my fathers business, 60 years ago. He was blacksmith/welder and avid motorcyclist and with his brother who was a fitter and turner specialized in repair and custom fabrication for what we now know as petrolheads. In those days there was still good business to be had converting rigid and plunger framed bikes to swingng arm, and in modifying strengthening and repairing road based frames for clubman competition, so I do actually have hands on experience of frame design and modification And what breaks and how to prevent it happening again.

At the modest outputs that our aiheads put out, it isnt hard to get a decent handling dirt bike - it is more about weight distribution and spring and damping rates than chassis rigidity.

My knowledge of current high power race bike technology is limited to what the bloke over the back fence is prepared to let slip, but as he is Jerry B he probably knows as much about that subject as anyone.

Thanks for the update

and I'll bet JB also agrees not to let the engineers take control of entire chassis design - he's had a lot of experience decoupling what Honda engineers had stuffed up...especially in his early days with them

Not as much now that he has left Honda !.

It appears that it is now a now a electronics race, horsepower and the physical parameters of the suspension are now secondary to the electronic control systems for both.
Exactly how much of that is predetermined by the factory and how much is able to be set on the fly is something that Jerry is tight lipped about so I suspect Yamaha has an advantage over the others here - Val was able to win recently even although his straight line speed was well down on the others.

Agreed but you've clarified your point somewhat, at least to me. I can see your point of view, but i'm not sure i'd think of it as an unsupported length. My thoughts are that the sides of the box section provide the support as they are probably 1.5 - 2mm wall thickness. Wouldn't that side section support it well enough and counteract the concentration of stress at the (almost) ends?
I'm no frame builder or engineer, just an interested novice.
Cheers
Bill

absolutely agree with those comments - the last GP I went to you could clearly see and hear the Yamaha was the bike best sorted in the electronics department - must be heart breaking for the other lesser teams :huh

I have just arrived home from a business road trip and I am more than a little dissapointed with the earlier comments, Beemerboff.

I suppose its easy to knock someones work (personally) rather than ask questions for clarification.

I called in to see Paul yesterday on my way home from Queensland and we chatted some more about the frame among many things for about 4 hours, including a nifty CDI ignition system for the airheads.

The Box section is actually 70mm and it isnt simple box as such but an amazingly strong section that was made by bending from flat sheet, and tig welding two c channel peices together. It is way over engineered.

I also spoke to 2 people who have ridden the bike and their reports were glowing, one a BMW specialist in Queensland, who is thinking seriously about ordering one as well.

I have seen Pauls work over the years and he would forgotten more than I will ever know. How many people would enter an Airhead R65GS in the Australian Safari, Condo 750. I am looking forward to following it this year as well. Paul is out there doing it!!!

I RESPECT him, his work and designs.

Yes you can say that its been done before, everything has. Look at Tony Foale and John Bradley's books and you will see lots of similar designs, There is a Husaberg influence in there as well.

I havent seen anyone build an Airhead frame like this and I thought I would share it with like minded individuals here in Old School. Didnt expect a friends work and design supposedly lacking in merit to be criticised by using 'Frame designers' (whom are the frame designers you referring to Beemerboff???) Maybe an apology might be in order, but I dont expect it.

Beemerboff your response above, and I will quote you, 'leaves me cold'

I would like to see your engineered frame desgns and constructions, if you have some, and would like to offer for this thread for review as well.

Thanks Pezz, well said! I think that addresses the question i had about the strength of that box section. Any idea what $$ Pauls asking for one of these frames?

Read my post - I didnt say there was no merit in the design - I said that Paul didnt seem to see any merit in triangulation.

You quote Tony Foales name - if you have read any of his work you will know that he is is a great advocate of triangulation as a way of producing a light and rigid structure . Not that I am a great fan of Tony------------!.

There will always be differing opinions on frame design - Bert Hopwood was offered the featherbed frame by the McAndless? brothers before it was taken up by Norton but rejected the design as it seemed to contradict sound engineering principles. It might well have , but it still worked OK

I have never felt the need to reinvent the wheel, or motorcycle frame.
At the sort of power outputs we are talking about here the configuration is relatively unimportant - as long as it holds the wheels apart and relatively in line and flexes a little in a controlled and predictable fashion it will do the job.
I have never said that Pauls frame would not do that, I have simply said that concentrating all the frame stresses into one massive unsupported member is not the way I would go about it.

And whether you think that opinion is right or wrong, I consider that am entitled to state it, as long as I don't use the forum as a vehicle to personally abuse the designer.

So if anyone considers my critique of the his frame amounts to personal abuse of Mr Rooney , my sincerest apologies.

And I look forward to somebody getting back to the topic and telling me exactly what problem the frame is trying to solve and what it does better than a stock or gusseted / braced stock frame, which after all was good enough to win the PD three times.

Wow, I really like the actual level of debate and discourse... you guys must be from overseas what with the use of multi-cylinder words and you can tell youre not shouting behind the screen

I think that the fact he made a frame that's different from a known quantity is a good thing. That frame solves three things off the bat that I can think of: lightness, rigidity and fricking easier oil changes.


In my eye, I immediately saw it as resembling a modern perimeter frame:



I see not only successful thought process regarding many elements of what it takes to hang a bike off of a frame like that, but also quality fabrication skills to bring such a thing to life. So what if BMW already figured all this out.

Its cool as hell.