Taken from the vtr1000.org site in a post by Roger Ditchfield himself:

"Hi Guys, In this thread there has been several references to the "ears" in the Spondon frame. This the story. The development of the VTR was originally given to Russell Savoury by Honda UK who employed the services of Mick Grant as a consultant. After more than a year the project had failed to achieve too much progress and while I was at the Suzuka 8 hour I was asked by HRC if I would be interested in taking over the project. I agree provided that Russel was happy to do that - which he was. When I took over and uplifted all the bikes and equipment from Harlow I had five modified frames. Enquiries revealed that Spondon were asked to do this by Mick to cure high speed straight line weaving. I then examined the dampers that had arrived only to find that they had been extended between 15mm and 25mm centre eye to centre eye longer than standard of 345mm! IMHO the "ears" were fitted in an attempt to cure a self inflicted problem. As already mentioned in previous posts no ST3 race bikes producing far more power than Russels best of 118bhp ever ran with this modification including mine. The standard frame was modified and I have done this modification on two customer bikes in the UK. I left the Spondon ears on my ST2 Production race bikes purely because they did no harm to the new Revolution suspension set up and the then ACU Minimum Race Weight Regulation for that class allowed then to stay there. If you have a VTR bike exceeding 135bhp I recommend the Standard frame modifications as used on all ST3s"

here is the link: www.vtr1000.org • View topic - New bike - Moriwaki race vtr

And here is the cherry for that sundae, a pic of the Moriwaki Stage 3 bike that ran at Suzuka in 1999:

 

And here for reference is Marty's road going Spondon with 'ears'

 

Now THAT is interesting. For clarification, we're talking about the two tabs that extend from the rear frame engine mounts to the swing arm engine mount on the bike, yeah?

So according to this, these aren't really to support the swingarm in the frame, they're just to correct a spacing mistake made at Spondon? Instead, the bracing inside the frame is all that's really needed....

From an eyeball engineering standpoint, I could see this happening... it's a pretty big chunk of aluminum that the swing arm attaches to... and the ears aren't fully braced... they probably add some stiffness but they are kind of flex tabs sticking out.

 

Essentially, what Roger is saying is that the ears were added to correct a straight-line stability issue. In other words, early on in the development process, the lack of stability was (in retrospect, erroneously) attributed to flex in the swingarm pivot area. The proposed remedy was thus to reinforce this area by adding extra support via the "ears". However, as Roger points out, closer inspection revealed that the instability was misdiagnosed and was, in fact, caused by excessive rear ride height (adding 15 to 25mm to the rear shock length would, due to linkage multiplication, generate a rise in rear ride height of about 50 - 90mm). Once this (excessive) shock length was removed, it would appear that the instability problem went away. That, in a nutshell, is it.

 

From engineering standpoint, Structurally tying the frame to the "Flex point of the suspension " Would make easier setting up the suspension, and help control "Flex and twist " when exiting curves....

"attributed to flex in the swingarm pivot area. The proposed remedy was thus to reinforce this area by adding extra support via the "ears".



How beautiful that site is... just wow......

 

Not sure I follow...... ok, I am sure I don't, lol Care to re-phrase please?

cheers

 

mikstr,
Thanks so much for posting this. I wish Roger would do a series of youtube videos on the VTR.

 

I never understood how exactly the ears adding stability, it seemed a bit wrong to me, so what is Roger saying is that the instability is due to the linkage. I'm a little confused now, how is the linkage effecting on instability at the pivot area? And so the only remedy you really need is to drop the height ride??? Is this got to do with the flexing at all? Or more like the geometry of the bike?

 

The instability came from an an overly long shock (which raised the rear excessively, in so doing reducing the rake and trail, and adding a bunch of weight over the front end). The ONLY function of the linkage in the discussion is that the shock acts on the swingarm through a linkage. This linkage operates with leverage to multiply the shock's limited travel to produce the 120mm or so of travel for the rear suspension. The shock stroke is nowhere near 120mm so the linkage (together with its position on the swingarm) works to "leverage" the limited stroke to give acceptable travel to the rear suspension.

 

I could have sworn Roger's explanation was simple and straightforward...... perhaps I was wrong......

 

That makes allot more sense, thanks for clarifying.

 

Not when you read it wrong like I did!

 

corrected #5
Agreeing with the article

 

The swingarm pivot area of the VTR's chassis is for sure one it's weak points. Anyone who has put their VTR on the track can attest to this. The flex in that area causes the chassis to "wind up" during hard cornering. This effectively simulates a bent frame. The excessive flex makes the VTR a terrific street bike but hurts it when pushed hard.

I've been working on my own version of something like this off and on for the past couple of years. I think it is a valuable upgrade.

 

There is no doubt a reason Honda put such a robust frame (and ran the swingarm pivot through it) on the RC51 (a quasi-offspring of the VTR if you will), and that reason has to be the extra rigidity needed when dicing it out for champioships on tracks around the world. However, to say that your engine cases will instantly disintegrate if you get over 120 hp as some would have us believe is obviously urban legend.....

 

Not sure that I've ever heard that before, but I agree that it's not grounded in fact. Suspension loads are much greater than engine drive force.

 

The instant disintegration bit was an (obvious) exaggeration, but you get the idea

 

But none of the ST3 bikes had the extra frame ears?

 

Not according to Roger, and he would know......

 

I think you are confuing two such urban myths a little mikstr... One being that the 130+ bhp engines would self destruct due to a weak bearing/wrist pin seating... And that as far as I know is still unproven either way... The "urban myth" you are talking about is that 130+ bikes and others would need the ears to strengthen the casings...

And I still say that regardless of Rogers lesson on history, I still think it's valid... One, he's talking about racebikes... They have a measured lifespan in x race starts... Not years... Two, even if the ears was originally for stability, to fix a problem, they are infact strengthening the weakest point of the frame in terms of flex, which has a benefit for chassie setup... And more importantly, three... The swingarm bolts directly to the casings, in a way that's not exactly high strength in terms of how crash durable it is... I have seen more than one crashed VTR where the swingarm ripped from the engine casing, or the casing was cracked, as it hit a curb or similar in the wrong place...

So, while it isn't necessary, on 130+ hp, or lower... I still say that it's a good idea if you are going to use the bike on track, since you reduce flex, and add crash durability and potentially lifespan to your engine casings...

With Rogers lesson, I see them more like the crashprotectors, and to be honest, I never thought there was a magic bhp figure... But yeah, higher hp, higher load and stress on parts...

 

I guess my attempt at sarcasm was perhaps over the top and led a few astray. I realise that the crank snapping and case snapping issues are two separate items.

I am also not in any ways saying that the "ears" are not a worthy addition. I have never been a fan of "frameless" swingarm pivot points such as on the VTR (and 929/954). Handling and crash durability aside, I fail to see how adding unnecessary stress to this area can have any potential benefits (stress can and will inevitably result in flex, and have undesirable effects on the numerous shafts and gears which are designed to run in fixed position). In other words, I question the entire premise of this design but, alas, my bike uses this design......

Would I like to have "ears" on my frame? Yessir!!!! However, the underlying message as I understand it is that they are not 100% necessary, not on a streetbike anyhow. Massaging your engine to develop over 120 hp will not inevitably result in failure of the case area uner normal use and this goes against certain urban legends which claim that crossing the 120 hp threshold is an instant recipe for disaster (ie. cracked cases).

 

Since there is a an ongoing discussion on this site about which color VTR is the fastest, I'd like to point out that this extremely fast looking VTR is BLUE.

Seriously though, while all the engineering reasoning behind the "ears" is over my head, I have seen those on my mechanic's VTR, (Bart / Faster Motorsports / Denver). I thought a large part of the purpose of them was to adapt standard aftermarket rearsets to the VTR. I believe Bart also told me his VTR put out about 130 hp.

 

What I find odd is the Dunlop sticker on the fork tube.....

 

Not enough room to spell Bridgestone? lol

 

I can´t attest, don´t have problem on track with stability. I had on highways when testing high speed, but after putting your rear shock, I can go to the max speed without problem.
Of course depends on rider - weight, riding style, and skills.

 

No forgot they weren't USD forks and fork seals sliding over writing usually isn't a good thing.....

Just old and forgetful......lol