Rooney Special Airhead GS Race Frame

[carmima]

Originally Posted by OldDog

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

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

[Beemerboff]

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.

[carmima]

Originally Posted by Beemerboff

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

[Beemerboff]

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.

[OldDog]

Originally Posted by Beemerboff

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.

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

[carmima]

Originally Posted by Beemerboff

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.

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

[Pezz_gs]

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.

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.

[OldDog]

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?

[Beemerboff]

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.

[Stagehand]

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.

[drhach]

Originally Posted by Beemerboff

.....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.

That is a good question. I don't know the answer. I do know that often times there is a "solution looking for a problem". Not to say that that is the case here. Many people modify stock frames. I suppose this is one more approach. Probably in the end it's just as much work and at least differentiates your work. After all, if anyone ever sees one of those frames, they'll say "Rooney". Any other frame and they'll just say "BMW".

[Lornce]

Originally Posted by Beemerboff

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.

Appologies accepted and efforts to keep this civil much appreciated.

As I see it, Paul's addressed at least three important issues with his design:

1. Reduced Weight: Always beneficial in a sporting motorcycle as it enhances control.

2. Frame Rigidity: Always beneficial in a sporting motorcycle as it enhances control.

3. Steering Geometry: Rake appears to be more aggressive than BMW standard. BMW's are comfy and stable, but perhaps a bit too conservative in the geometry department for truly aggressive riding. (we could start a whole other thread on the attributes of various steering geometries and their effects/benefits with lots of references to Sir Foale et al ) A frame with more structural integrity would encourage a more spirited pace and it'd be nice to have steering geometry to go with it. Paul appears to deliver on that.

BMW's PD wins were impressive and still remarkable achievments. But they were an awfully long time ago. Time and bike design marches on.

I'd be curious to know how much Paul needs for one of his efforts. If the price were right, I could see one of his designs sitting proudly in my own garage.

[Magnon]

I'm sure Mr. Rooneys' farme design is very sound but I fail to see any real advantage over the reinforced standard frame as supplied by HPN. Firstly, 183 kg is no lighter than many of the modified airhead featured on this forum. The frame may be more rigid than the HPN modified frame but is rigidity an issue? A lot of the reinforcing carried out by HPN was to prevent the frame cracking in stressed areas when longer suspension was fitted and aggressive use was anticipated. This reinforcing may have also improved the torsional rigidity - the frames ability to to keep the steering head at right angles to the swinging arm pivot but does it need to be any more rigid? Lastly, whether HPN actually change the steering head angle when they modify a frame has been debated many times but as far as I can see the head angle remains the same as standard. I am sure that over the years, HPN and others have experimented with steeper steering angle and it would have become part of their modifications had it shown any advantage.

As someone said, time moves on and the days when HPN bikes were winning the Dakar are long past. There have been many improvements in suspension technology and whilst shaft drive is always going to be a limitation onBMW off road racers there are, undoubtably, much better set ups than the old monolever even with an Ohlins.

[Steve in NZ]

who gives a shite about all the blah blah blah bullshit. I take me hat off to "Mr Rooney" for taking the time and effort in doing something different that stands out.

i think it looks good

[igormortis]

Originally Posted by Magnon

...whether HPN actually change the steering head angle when they modify a frame has been debated many times but as far as I can see the head angle remains the same as standard.

Yeah, I've always understood it as the relative angle changing due to the different suspension geometry - despite many heated arguments to the contrary.