Math me please

[Claviger]

I understand what you are asking, but what is the real world application? If you are trying to improve the overall performance of the handling I get it. The only other application is if you are looking at doing track time on a laid out coarse that makes sense too.

In real world applications there are too many variables and unknowns to take into account. One of my favorite features of my R3T is how well it performs for such a big bike, but it makes you work for it for sure. It takes steady nerves to throw these bikes low into the corners and then power out. It is one of the things that separates those of us that ride these bikes.

I get around my cruiser friends and most of them have no understanding of how well their bikes perform. Until they head someplace like the Dragon for the first time and get the bejesus scared out of them.

PS I hope you are wear full leathers doing this stuff.

I do wear leathers when playing.

That said I’d really just like to get corner speeds up a little bit more but I don’t think any of the major factors lend themselves to modification very easily.

That’s fine just wanted some info from people who know their ****, because there’s a lot of crap on the inter webs that’s contradictory about what makes a given bike need a given lean angle in a corner.

 

[1olbull]

Steve comes in a blows my mind in 10 lines lol. Wish I'd payed attention in geo/trig!! The calculator I linked provided a return of the below:

Meaning, I kept around 7 mph as a theoretical reserve before washing out. Just trying to wrap my head around margins before washing the front or low siding from the back.

I have communicated with Jim Davis. He is one sharp cookie, but not a collision recon expert. His approach is with theoretical physics calculations and sometimes the methodology is different than in the real world of legal, court qualified, crash reconstruction. Without seeing the formulae he used I believe, based upon his requisite input values, this Exel spreadsheet to be more theoretical than real-world practical.
1) Determining the actual CG location for your motor can be done, but tis NOT an easy task. Determining your rider and motor CG would be exponentially more difficult.
Besides the combined rider/motor CG is a rather large variable and changes rapidly in a dynamic situation.
2) Why is and what tire width is used? The area of tire contact with the road surface is what is critical and that is already dependent on unknown lean angle???
MC tire profiles are not in a true radius and technically the contact patch location is not the same throughout a lean.
3) I am very curious why and how the wheelbase is used and affects his lean angle calcs???
4) Your real world max cornering speed is easily and simply determined with the critical speed formula. S = SQRT 15rµ
Example: S = SQRT 15 X 300' radius X .75 coefficient of friction - S = 58 mph. Note that this is a max value. Also note that if the pavement is lees than clean and dry or there is any super elevation the coefficient of friction must be adjusted accordingly.
Edit: the formula V = SQRT grf can aslo be used for this. g=gravity at 32.2'/sec/sec, r=radius in feet, f=coefficient of friction. The answer is Velocity in feet per second.

 

[1olbull]

@Speedy
Amigo,
I reckon you have just touched on why the wheel base comes into play. Gratitude.
Disappointed I'll not meet you in Stearns and shall look forward to doing so here in WA in July!

 

[1olbull]

I do wear leathers when playing.
That said I’d really just like to get corner speeds up a little bit more but I don’t think any of the major factors lend themselves to modification very easily.
That’s fine just wanted some info from people who know their ****, because there’s a lot of crap on the inter webs that’s contradictory about what makes a given bike need a given lean angle in a corner.

Rob,
A couple additional formula you may find useful is to determine the friction necessary to take a curve of known radius at a particular speed and for determining the necessary lean angle.
f = v^2 / rg = S^2 / 15r
or the lean angle necessary:
Lean angle = tan^-1(v^2/rg) = tan^-1(S^2/15r)

 

[TheKid]

Quite educational. I know the right tire helps. We don't need long mileage tires. Darkside would be ok for a long road trip, but they don't handle worth a crap. On that touring I used Dunlop 251's I think. You could run around on the floor boards if you had the nerve. I hit them often, but not enough to not be surprised.
I would love to see a video of your travels. Sounds seat gripping

 

[Speedy]

Link Removed

Great depiction of contact patches from Claviger. Now everyone should understand why front tires cup over time (They all do, just a matter of time) and why rear tires generally don't.

These graphics show contact patches that are developed without any fore or aft acceleration. The apparent asymmetry grows even stranger when those forces are applied.

Also wanted to note that the rider doesn't lean a motorcycle from the contact patch towards the center of the curve. What happens is that the motorcycle rotates around its center of gravity with the contact patch moving away from the curve center point and the part of the motorcycle above the CG moves toward the center of the curve. If this does not occur, the motorcycle will not turn. Ever ridden with a brisk side wind? Did you lean? How did you go straight?

 

[mr hunt]

I tend to follow a denying the consequent pattern for cornering velocity:

I lean over and fall off (a) then i go slower next time (b) ... not (a) therefore not (b)

 

[Claviger]

Ok so I went out and had a day full of playing on the twistiest road in the area with some SERIOUSLY fast riders. By SERIOUSLY fast, I mean holy oh my god jesus take the wheel fast, on track bikes riding on the street... that fast. I did slowly work up harder and harder until the rear end stepped out about 1 foot at 1/2 throttle leant fully over during a roll on. That's what I'd consider "my" limit and basically the bikes as well. I also found technique to back in the rocket repeatedly and consistently.

It is just plain humbling watching truly fast dudes on track bikes and the incredible pace they can set around tight turns. On the wider turns, I can pace them fine on the Rocket, but as soon as the radii get under 200 feet or so.... goooood byyyyye, not possible to keep up no matter what you do, its just not possible.

I can now firmly say, no need for rebuilt forks or aftermarket cartridges on the Roadster. I reckon there's maybe 5-10 guys who will ride their R3 the way I was riding today, and the AV-71 + 10w fork oil + .93kg spring + 100mm air gap worked perfectly, not a negative wiggle, chop, bump, squirm, nothing from the front, just tracked and stuck exactly as you'd want it to. Riding ranged from 150+ in 60 mph corners to 40+ in 20 mph corners, and the only undesirable thing was that slight rear end slide.

So, looking at that calculator I found, since now I know what the max attainable practical speed in a certain turn was here is the comparison to his calculator and reality:

What actually happened: stepped out rolling on from 40 mph in a 90ft radius curve (measured in google maps), his calculator it seems is a little conservative or my CoF was great than 1 (tires were boogering, so greater than 1 is quite possible):

After actually finding the R3R limits, I'll confidently say, there is NO cruiser out there that will out run an R3R ridden in anger through the twisties (provided you've done suspension work).

 

[1olbull]

Quite educational. I know the right tire helps. We don't need long mileage tires. Darkside would be ok for a long road trip, but they don't handle worth a crap. On that touring I used Dunlop 251's I think. You could run around on the floor boards if you had the nerve. I hit them often, but not enough to not be surprised.
I would love to see a video of your travels. Sounds seat gripping

That D251 is an excellent tire!
If there was one that fit my Roadster, it'd be on it!