Author Topic: Just because it's the purest form a motorcycle ever took  (Read 200 times)

mellorp

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Steveog

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Re: Just because it's the purest form a motorcycle ever took
« Reply #1 on: December 03, 2019, 11:14:07 PM »
Beautiful, Phil.

Serious question: How does the rear brake stay-arm work. In the drawing it runs behind the wheel, which would seem to be impossible. I've often thought a stay-arm from a rear, lower caliper hanger, running to a pivot point on the chassis would be a small, but theoretical improvement for the 3xv and TZ versions of the V-Configuration. The 3ma has such an arm, but its pipes aren't in the way.

As if I could tell a difference when I ride. Just curious.

Steve
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SeaR1ck

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Re: Just because it's the purest form a motorcycle ever took
« Reply #2 on: December 03, 2019, 11:21:57 PM »
That's the chain there's no brake stay arm on that bike. I read a post about brake stay arms and why they are no longer in use. It said that the arm would cause feedback and under hard braking caused the rear wheel to want to hop more vs not using one or it was increased brake chatter one or the other it negatively affected handling.

It's been awhile since I saw this post but basically said brake stay arms are bad.
« Last Edit: December 03, 2019, 11:27:37 PM by SeaR1ck »

Steveog

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Re: Just because it's the purest form a motorcycle ever took
« Reply #3 on: December 03, 2019, 11:44:28 PM »
Thanks, Rick. No, I am sober. I just couldn't see how the caliper was braced by the swing-arm. My mistake.

I'll take your word for the physics of a brake stay-arm. I've trolled this idea before and ybk sent a pic showing that Ducati was using such device in recent years (not sure how long they experimented with it though). I suppose electronics are controlling brake hop in MotoGP.

Steve
Brief, fleeting Glory. Which of itself cannot last, but while it does is the greatest game of all.

mellorp

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Re: Just because it's the purest form a motorcycle ever took
« Reply #4 on: December 04, 2019, 12:31:05 AM »
The caliper mounting bracket is so simple. A hole for the spindle, extends to mount the caliper and a slot that holds it in position against the inside of the swing arm. It's basically a square (if you fill in all the bits machined off) with the spindle and locating lug on the top 2 corners and the 2 bolts for the caliper on the lower 2 corners
Mellion say If it ain't broke thrash it until it breaks

Martin77

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Re: Just because it's the purest form a motorcycle ever took
« Reply #5 on: December 04, 2019, 12:22:51 PM »
Brake torque arms were generally designed to lift the rear end when the back brake is used. They seemed to be more common when bikes had a lower centre of gravity (by design) in the late 80's, in order to shift more weight onto the front tyre under braking, which became a moot idea when wheelbases shrunk, and tyres improved meaning the back wheel lifted off the ground easier anyway.

And like Steve said, Ducati tried one last year, probably as their chassis is relatively long with a lower centre of gravity.

Steveog

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Re: Just because it's the purest form a motorcycle ever took
« Reply #6 on: December 04, 2019, 09:21:08 PM »
Thanks, boys.

Phil - Yeah. I get it now. Super-simple design. Elegant. I prefer the look of the "under-arm" caliper. But, there might be some theoretical advantage to that design. Considering it for my track 3xv. Again...its not as if I'm talented enough to feel it, but much of the fun is feeling like race engineer.

Martin - My direct experience with the stay-arm and its mounting point was from dirt bikes. I believe in that application, the idea was connecting the brake torque arm to a fixed part of the chassis allows the brake to not affect the suspension as the wheel moves up and down and for the braking force to be isolated from chassis movement.
 
That's a pretty old memory, though. I've attached a pic of a 1976 Husky, but don't have any real engineering attribution as to "why" they used it. My old TM 250 Suzuki had the stay-arm attached to the swinger. My 2004 R-1 looks like my 3xv. (???)

Based on many modern designs, your explanation makes the most sense for a track-based 3xv.

Steve 
« Last Edit: December 04, 2019, 10:11:22 PM by Steveog »
Brief, fleeting Glory. Which of itself cannot last, but while it does is the greatest game of all.

mellorp

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Re: Just because it's the purest form a motorcycle ever took
« Reply #7 on: December 04, 2019, 10:49:34 PM »
Beautiful, Phil.

Serious question: How does the rear brake stay-arm work. In the drawing it runs behind the wheel

Steve

Is that the chain ?
Mellion say If it ain't broke thrash it until it breaks

Steveog

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Re: Just because it's the purest form a motorcycle ever took
« Reply #8 on: December 04, 2019, 11:35:34 PM »
Very funny, Phil.
Brief, fleeting Glory. Which of itself cannot last, but while it does is the greatest game of all.