Author Topic: Not sure what to say?  (Read 1175 times)

Offline wymple

  • Guzzi Hero
  • *****
  • Posts: 700
  • Location: SE Iowa
Not sure what to say?
« on: August 29, 2018, 08:38:46 PM »
https://youtu.be/rDJZjdKai24

Read the comments section, too.
No trees were harmed by the conveyance of this message, but a lot of electrons were seriously disturbed.

Offline oldbike54

  • Moderator
  • Guzzi Hero
  • *
  • *****
  • *
  • *
  • *
  • *
  • *
  • Posts: 24701
Re: Not sure what to say?
« Reply #1 on: August 29, 2018, 08:45:56 PM »
 Japanese Speedway , mostly for gambling purposes . There is a a short piece about it in On Any Sunday II .

 Dusty
Transmit the message , to the receiver
Hope for an answer someday


Offline Lannis

  • Guzzi Hero
  • *****
  • *
  • *
  • *
  • *
  • Posts: 24873
  • Location: Central Virginia
Re: Not sure what to say?
« Reply #2 on: August 29, 2018, 09:44:12 PM »
https://youtu.be/rDJZjdKai24

Read the comments section, too.

They do strange things in other countries ...

https://www.youtube.com/watch?v=_94viw75ulc

Lannis
When you're taking flak, it means you're over your target.

Offline Ncdan

  • Guzzi Hero
  • *****
  • *
  • *
  • *
  • Posts: 2398
Re: Not sure what to say?
« Reply #3 on: August 30, 2018, 09:20:22 AM »
Well one thing for sure, it's hard to argue the point that he's not a superior rider on a superior bike, over the others on the track.

Offline oldbike54

  • Moderator
  • Guzzi Hero
  • *
  • *****
  • *
  • *
  • *
  • *
  • *
  • Posts: 24701
Re: Not sure what to say?
« Reply #4 on: August 30, 2018, 09:32:36 AM »
Well one thing for sure, it's hard to argue the point that he's not a superior rider on a superior bike, over the others on the track.

 The guy you're referring to is riding a bike built specifically for that type of racing . It weighs about 220 LBS , and the rider is probably a seasoned Japanese Speedway racer . Not so different than putting a dedicated dirt track race bike on a mile oval against a bunch of much more powerful street legal bikes . The dirt tracker is going to be faster .

 Dusty
Transmit the message , to the receiver
Hope for an answer someday

Online Moto

  • Guzzi Hero
  • *****
  • *
  • *
  • *
  • Posts: 3098
  • Pazzi per la Moto Guzzi!
  • Location: Madison, WI
Re: Not sure what to say?
« Reply #5 on: August 30, 2018, 09:50:52 AM »
I say that this a good demonstration of the physics point that the traction available from a skinny tire is as good as from a fat one.

The reasons why he won instead of just held even with the others are different, of course!

Moto

1976 850-T3
2007 GRiSO 1100
2017 Italjet/SSR Buccaneer 250i

Offline Kev m

  • Not your normal Hombre
  • Guzzi Hero
  • *****
  • Posts: 28309
  • Yo from Medford, NJ
Re: Not sure what to say?
« Reply #6 on: August 30, 2018, 09:54:50 AM »
I say that this a good demonstration of the physics point that the traction available from a skinny tire is as good as from a fat one.

The reasons why he won instead of just held even with the others are different, of course!

Moto

Is it? (Honestly asking).

I mean, there are weight and power differences, so the loads were likely very different right?

That same tire type/size probably wouldn't have worked as well on those sportbikes I assume?

(sorry if I just opened a big bag of "I'm not gonna understand the physics of the answer")  :embarrassed:
Current Fleet

18 Guzzi V7III Carbon Dark
16 HD FLHP
13 Guzzi V7 Stone
11 Duc M696

Offline Kiwi_Roy

  • Guzzi Hero
  • *****
  • *
  • Posts: 7145
Re: Not sure what to say?
« Reply #7 on: August 30, 2018, 10:03:41 AM »
I wonder what would happen if they ran a few laps in the other direction.
72 Eldorado
07 Griso 1100
17 V7iii Special

Moto Guzzi - making electricians out of riders since 1921

Offline Sheepdog

  • Guzzi Hero
  • *****
  • *
  • *
  • *
  • Posts: 5443
  • 2007 Moto Guzzi California Vintage
  • Location: Waldheim, Louisiana. USA
Re: Not sure what to say?
« Reply #8 on: August 30, 2018, 10:15:58 AM »
They bet on bicycle racing in Japan, also. Keirin is a popular spectator sport that involves competitors pacing behind a motorcycle until the final sprint to the finish. It was invented in 1948 for the expressed purpose of gambling. It is now an Olympic event...


"Change is inevitable. Growth is optional." John C. Maxwell

Offline Shorty

  • Guzzi Hero
  • *****
  • *
  • *
  • *
  • *
  • *
  • Posts: 2814
  • Be a simple kind of man.
  • Location: Oklahoma
Re: Not sure what to say?
« Reply #9 on: August 30, 2018, 11:36:47 AM »
If I were to hazard a guess, I'd say the yellow bike was supposed to win.... :cheesy: 

Online Moto

  • Guzzi Hero
  • *****
  • *
  • *
  • *
  • Posts: 3098
  • Pazzi per la Moto Guzzi!
  • Location: Madison, WI
Re: Not sure what to say?
« Reply #10 on: August 30, 2018, 12:38:30 PM »
Is it? (Honestly asking).

I mean, there are weight and power differences, so the loads were likely very different right?

That same tire type/size probably wouldn't have worked as well on those sportbikes I assume?

(sorry if I just opened a big bag of "I'm not gonna understand the physics of the answer")  :embarrassed:

I'd better tread carefully here.  :grin:

I'm no expert, but I did buy, partly read, and then misplace a book, Motorcycle Dynamics by Vittore Cossalter, that I vaguely recall treating this topic.

The principles as I recall them seem simple enough. The area of the contact patch is proportional to the load at any particular inflation pressure. In essence the area times the psi must equal the load. This means skinny tires and fat tires, surprisingly, have the same contact patch at the same inflation pressure. So far, so good.

Fat tires, however, can be run at lower pressures without the risks to carcasses and rims that would be entailed with skinny tires. So they have larger contact patches in practice.

But here comes the real surprise. As the pressure of the tire on the pavement (the psi) increases, so does the coefficient of friction of the tire, in linear (as I recall) proportion to the pressure. So the higher psi that a skinny tire in practice runs results in a smaller contact patch with an exactly offsetting increased coefficient of friction. Hence, it doesn't matter for friction whether you run a fat or skinny tire.

That is why the flat track bike can corner as well as the sport bikes (and the others). And also why the sport bikes could corner as well on the skinny tires provided they could achieve the same lean angles we see on the flat bike while running those tires (which they couldn't).

There are a couple of reasons to run fat tires on a sport bike. One is less tire wear due to a greater amount of rubber on the road, and lower pressures. Another is handling, since the bike rides up on the sidewalls in cornering, making greater lean angles available for relatively wide bikes. (This is not an issue for the very thin flat track bike, as we can see.)

As for power, it makes no difference for cornering speed. Traction is traction, and what doesn't go to cornering is available for acceleration, and vice versa. In the race video it is surprising and maybe suspicious that the sport bikes don't take more advantage of the straights, where they do have more power available since their traction is not going to cornering. But the straights are extremely short, and the riders don't seem as aggressive as they should be. The sport bike riders probably have to be extra careful with their throttles compared to the flat tracker.

In a longer race I would expect the higher loading per square inch on the flat track bike's tires to cause them to wear out quickly. But in the 4100 meter race this doesn't seem to have been an issue. EDIT: And the lower weight of the flat track bike also reduces the loading per square inch, compared to a heavier bike.

That's all I've got. I can only hope to find that book if need be!

Moto

P.S. One other thing I see I forgot to mention: the different weights of the bikes. This factor also cancels out because the centripetal force required for cornering is proportional to the mass of the bike. All these factors are why physicists and engineers resort to equations, which the book is full of.




« Last Edit: August 30, 2018, 12:46:43 PM by Moto »
1976 850-T3
2007 GRiSO 1100
2017 Italjet/SSR Buccaneer 250i

Offline Kev m

  • Not your normal Hombre
  • Guzzi Hero
  • *****
  • Posts: 28309
  • Yo from Medford, NJ
Re: Not sure what to say?
« Reply #11 on: August 30, 2018, 12:43:35 PM »
I'd better tread carefully here.  :grin:

I'm no expert, but I did buy, partly read, and then misplace a book, Motorcycle Dynamics by Vittore Cossalter, that I vaguely recall treating this topic.

The principles as I recall them seem simple enough. The area of the contact patch is proportional to the load at any particular inflation pressure. In essence the area times the psi must equal the load. This means skinny tires and fat tires, surprisingly, have the same contact patch at the same inflation pressure. So far, so good.

Fat tires, however, can be run at lower pressures without the risks to carcasses and rims that would be entailed with skinny tires. So they have larger contact patches in practice.

But here comes the real surprise. As the pressure of the tire on the pavement (the psi) increases, so does the coefficient of friction of the tire, in linear (as I recall) proportion to the pressure. So the higher psi that a skinny tire in practice runs results in a smaller contact patch with an exactly offsetting increased coefficient of friction. Hence, it doesn't matter for friction whether you run a fat or skinny tire.

That is why the flat track bike can corner as well as the sport bikes (and the others). And also why the sport bikes could corner as well on the skinny tires provided they could achieve the same lean angles we see on the flat bike while running those tires (which they couldn't).

There are a couple of reasons to run fat tires on a sport bike. One is less tire wear due to a greater amount of rubber on the road, and lower pressures. Another is handling, since the bike rides up on the sidewalls in cornering, making greater lean angles available for relatively wide bikes. (This is not an issue for the very thin flat track bike, as we can see.)

As for power, it makes no difference for cornering speed. Traction is traction, and what doesn't go to cornering is available for acceleration, and vice versa. In the race video it is surprising and maybe suspicious that the sport bikes don't take more advantage of the straights, where they do have more power available since their traction is not going to cornering. But the straights are extremely short, and the riders don't seem as aggressive as they should be. The sport bike riders probably have to be extra careful with their throttles compared to the flat tracker.

In a longer race I would expect the higher loading per square inch on the flat track bike's tires to cause them to wear out quickly. But in the 4100 meter race this doesn't seem to have been an issue. EDIT: And the lower weight of the flat track bike also reduces the loading per square inch, compared to a heavier bike.

That's all I've got. I can only hope to find that book if need be!

Moto


Excellent - thank you. I'll have to read that a few more times and will still probably struggle a little with it, but it seems very well described.
Current Fleet

18 Guzzi V7III Carbon Dark
16 HD FLHP
13 Guzzi V7 Stone
11 Duc M696

Offline oldbike54

  • Moderator
  • Guzzi Hero
  • *
  • *****
  • *
  • *
  • *
  • *
  • *
  • Posts: 24701
Re: Not sure what to say?
« Reply #12 on: August 30, 2018, 01:34:20 PM »
 We've only been over the *contact patch size VS traction* thing about every other month over the last 5 years  :laugh:



 And no , traction isn't dependent on the size of the contact patch . Didn't read the treatise , but one thing to remember , at any given pressure , if you make the contact patch wider it also becomes shorter , and the opposite is also true .

 Dusty

Transmit the message , to the receiver
Hope for an answer someday

Offline Ncdan

  • Guzzi Hero
  • *****
  • *
  • *
  • *
  • Posts: 2398
Re: Not sure what to say?
« Reply #13 on: August 30, 2018, 01:52:20 PM »
I wonder what would happen if they ran a few laps in the other direction.
Now that's an interesting though and question, that I would pay good money to witness.

Offline TimmyTheHog

  • Guzzi Hero
  • *****
  • *
  • *
  • Posts: 889
Re: Not sure what to say?
« Reply #14 on: August 30, 2018, 02:45:17 PM »
so....

It is not the bikes but the riders?  :evil:
Life isn't WHAT IS at the end.
It is HOW and WHAT you are doing to get there.

03 Honda Shadow Spirit - The Purple Beast (SOLD)
15 Guzz V7 Stone - The Red Chick (SOLD)
18 BMW R1200GS Rallye - The Blue Streak (SOLD)

Currently Bikeless...*cry*

***Wildguzzi Official Logo High Quality 5 Color Window Decals Back In Stock***
Shipping in USA Only. Awesome quality. Back by popular demand. All proceeds go back into the forum.
http://www.wildguzzi.com/Products/products.htm
Advertise Here
 


Advertise your products today. All proceeds go back into this website.
Your ad will show up over 10,000 times daily!
Advertise Here