Woody Posted January 20, 2006 Report Share Posted January 20, 2006 Yeah I'm still kind of here. The truth is I hate it when explanations start involving complicated physics. I am a man of very little brain and get easily confused. I actually convinced myself with the wall theory. Much of this was pretty much a moot point anyway, as we all appreciate that by far the best way to exit a corner is 'on the gas'. It's just nice to understand some of the detail. As for the trike, here's me exiting Siberia at PI... http://au.pg.photos.yahoo.com/ph/mysterybu...2&.dnm=6936.jpg So, what's to do on vaca in Tasmania? Ride :-) Quote Link to comment Share on other sites More sharing options...
tzrider Posted January 20, 2006 Report Share Posted January 20, 2006 As far as how many folks have done the constant throttle scenario, it's sort of hard to tell from the way Cobie asks his question just what he means by constant throttle and there are several conditions which are unclear... Let me ask Cobie's question a different way. If I get it wrong, he can jump in: You're riding on a road in Kansas -- not a hill or camber change for 100 miles in any direction. You're on a straight section of road, holding a steady 60 mph with the throttle partway open. You turn your bike into a constant radius corner while maintaining the exact same throttle opening. What happens to the bike's speed? ab Quote Link to comment Share on other sites More sharing options...
racer Posted January 20, 2006 Report Share Posted January 20, 2006 Yeah, like I said, figuring I knew what he was after, those were about the conditions I would assume. Though, being that Cobie's question didn't specify any specific type of answer, he might jump on you for specifying speed....as that sort of gives an inherent hint. And now the mea culpa... I had decided the appropriate thing to do was to go directly to Cobie by sending him an email or pm with my query, and then, as I was responding to someone else, thotlessly stuck it in there in what I thot at that moment would be sort of, je ne sais quoi, oblique without being sideways or something, perhaps, but in hindsight it feels icky. I think it was a real breach of manners if not protocol. Whether he has an issue with it or not, I do. So... Sorry Cobie. That was real backhanded of me and I apologize. Anyway... Hey Woody. Nice pic. See, I KNEW you were yankin on me. I might as well apologize to you too while I'm here. Perfect timing. I get to be the jerk of the hour. Speight's on me all around boys. Just call me a piss head Kiwi at heart. Yeah, like I said before, I still be a workin' on them thar people skills thangs. sometimes it seems like no matter how hard I try, I can't help being a bull in a china shop. But I do try. Bloody hell but i try. My face is red and I am laughing at me. Yeah, how bout the infinite radius of that virtual wall...I think I just walked into it and spilled my beverage. DOH! I'm outta here. I have to go home and rethink my life. g'nite my friends. Quote Link to comment Share on other sites More sharing options...
tzrider Posted January 20, 2006 Report Share Posted January 20, 2006 Though, being that Cobie's question didn't specify any specific type of answer, he might jump on you for specifying speed....as that sort of gives an inherent hint. Knowing what your speed is before you enter the turn doesn't compromise the question, which is: What will happen to your speed if you turn the bike and maintain constant throttle? ab Quote Link to comment Share on other sites More sharing options...
racer Posted January 20, 2006 Report Share Posted January 20, 2006 But I've never even been to Kansas. OK. That's a lie. I have been to Kansas. But I'm certainly not there anymore. Um, I haven't finished that online physics class yet. Can I get back to you? I need another cup of coffee. Blah, blah, blah... OK. Bike slows down. Period. Closed system, more resistance. End of story. But, but, but... Radius of the wheel decreases. RPM's rise. Wheel speed increases. But that's a smaller wheel. The speedo is no longer accurate. Frictional resistance increases. Total energy input remains consistent. Total output decreases. But, effectively, the gyroscopic effect of the wheels will induce anti-gravity so the mass of the bike is actually reduced..... Just kidding...gotcha. Quote Link to comment Share on other sites More sharing options...
tzrider Posted January 20, 2006 Report Share Posted January 20, 2006 OK. Bike slows down. Period. Closed system, more resistance. End of story. We have a winner! ab Quote Link to comment Share on other sites More sharing options...
racer Posted January 20, 2006 Report Share Posted January 20, 2006 GO STEELERS! Quote Link to comment Share on other sites More sharing options...
Woody Posted January 20, 2006 Report Share Posted January 20, 2006 Racer. You're alright, don't change mate. (bloody piss head Kiwi...) Quote Link to comment Share on other sites More sharing options...
racer Posted January 20, 2006 Report Share Posted January 20, 2006 ta Quote Link to comment Share on other sites More sharing options...
racer Posted January 20, 2006 Report Share Posted January 20, 2006 I can't figur out how to use the quote function since the software upgrade...I need to ask stuman for a primer. anyway, i mad a remark a couple posts back re: brkes vs coasting decel and it wasn't reallt correct. What I meant to say was...Coasting decel IS acting on the front wheel as are the brakes. the difference is the friction is only at the contact patch (rubber and tarmac ) as is the brakes (disc and pads). the friction is acting on the wheel and slowing it just like the brakes. and dont ask if rolloing out of the gas at 100kph is the same as rolling out at 50 kph with a 50 kph headwind. imoutta here, its friday. I have an interview for a new job and i have to go get my head into the right frame of attitude. excited, enthusastic, devoted..all that good stuff. cheers Quote Link to comment Share on other sites More sharing options...
Cobie Fair Posted January 20, 2006 Report Share Posted January 20, 2006 Was I supposed to be mad at somebody---if so, I missed it! CF Quote Link to comment Share on other sites More sharing options...
tzrider Posted January 21, 2006 Report Share Posted January 21, 2006 Was I supposed to be mad at somebody---if so, I missed it! Yeah, you're supposed to be mad at racer. Don't worry about why, just be mad at him. ab Quote Link to comment Share on other sites More sharing options...
Cobie Fair Posted January 21, 2006 Report Share Posted January 21, 2006 OK Racer, I'm really mad! (not quite sure why though). CF Quote Link to comment Share on other sites More sharing options...
racer Posted January 23, 2006 Report Share Posted January 23, 2006 A true testament to YOUR character, my friend. Quote Link to comment Share on other sites More sharing options...
Robsalvv Posted February 1, 2007 Report Share Posted February 1, 2007 Interesting thread. Hope no one minds me dredging up the past... new to the forum and surfing the board. Let's see if I have a grasp on the main points... Cobie asked a question about the weight distribution at constant speed on a straight line... if you discount drag, the f/r distribution would be about the same as if standing still, i.e. about what's neutral for that bike and rider combination. There's no intertial forces when the velocity is constant. If you hold a constant throttle and tip into a turn, a bike will slow down due to the smaller diameter of the tyre and also the cornering friction forces. The weight distribution will be biased toward the front by some amount proportional to the decelleration. If the lean angle and throttle are kept the same, the bike will eventually reach a steady state situation and settles down to a constant veloctiy, so the weight bias balances back to a more nuetral footing. The initial cracking of the throttle (once the turn is done) is to cancel out the slowing down bit. It goes without saying, that the gradual rolling on is to set the ideal traction picture and stablise the bike. As kept being drummed into us during CSS level 1 (and later) the number 1 job of the rider once the turn has been completed and throttle cracked is to stabalise the bike by gradual roll on of throttle throughout the remainder of the turn. ... anything else? Cheers Rob Quote Link to comment Share on other sites More sharing options...
racer Posted February 2, 2007 Report Share Posted February 2, 2007 No no no. Don't mind at all. How funny. What a difference a year makes. This is the thread I was referring to the other day when I mentioned how far we'd come since the last time Woody, TZ and I were on about this subjeect a year ago. About 600 million miles or so around the sun, haha. Anyway, if you tip into a corner at constant throttle you slow down due to the cornering forces I think. I don't think the smaller tire circumference has any direct effect on speed. Although the wheel will turn more RPM for a given speed at lean than in a straight line making the speedo read inaccurately higher than true speed. Maybe higher than what was indicated prior to tipping in...? Whether or not the bike eventually reaches a steady state ... hmmm. In terms of the original problem, assuming steady state in top gear (overdrive) prior to tipping in... My initial gut reaction is to say it will depend on the radius of the corner and the final drive ratio of the bike. Fifty mph is a good clip but sixth gear overdrive...hmmm. That's barely fast enough to maintain sixth gear in the first place. There are so many other variables I don't know if it is possible to make a standard determination. Assuming a shallow bend on the highway...OK sure. Rolling into a tight bend at fifty in sixth gear with steady throttle....? I don't know. Maybe in a lower gear. Something less than 1:1 for instance would be one thing. Anyway, I'll have to read through this thread over the weekend. There was some funnny stuff about juggling sledge hammers and such as I recall... Quote Link to comment Share on other sites More sharing options...
Robsalvv Posted February 2, 2007 Report Share Posted February 2, 2007 Yeh, there was some funny stuff in this thread I wish I had another year of high performance track work under my belt... sigh. Just on the wheel diameter thing, if you've got a constant throttle, therefore a given amount of fuel going into the engine, the bike MUST slow down as you tip it in. Discounting the cornering friction forces side of things, the bike would have to slow down anyway because the engine revs aren't changing, but the rear wheel diameter has effectively reduced... so you cover less distance for each revolution. See? The speed you eventually settle down to depends on how far you lean. Conversely, for a constant throttle, you'll start to speed up as you stand it up. The flip side is the one you mention, that if you hold the (true) velocity steady as you're tipping in, the revs must go up as the lean angle increases. A smaller wheel needs to go around more often for the same speed, so for a given lean angle and speed, you'd need more throttle than if you were travelling in a straight line. As to what would happen if you had a huge flat play area, marked out a large diameter circle, countersteered the bike into a known and constant lean around this cirlce and kept going round and round rolling it on... You'd eventually bump up against the rev limiter in 6th {that would be near 300km/h on my bike! Yikes!} and the sudden automatic "roll off" could be a bit exciting!! Before that happens, it'd be better to gradually reduce the roll on till you eventually stop and hold a steady throttle position. There'd be some weight transfer forward as the bike gently sorted out it's dynamic situation until it settled into a steady contstant velocity. We've been well taught to roll on once the turn has been finished in order to put the bike into it's ideal traction picture, but there's nothing to say that a bike wouldn't happily keep turning a corner with a neutral weight transfer picture, i.e. constant velocity, instead. Thoughts???? Cheers Rob Quote Link to comment Share on other sites More sharing options...
racer Posted February 2, 2007 Report Share Posted February 2, 2007 Respectfully, if you discount cornering forces you are not talking about the reality of cornering anymore. If you hold a constant or steady throttle position when you lean into a corner, actual or "true" road speed will decrease due to cornering forces. The simple fact that you are inputing the same amount of power and adding more resistance will dictate a decrease in speed. Same fuel. Same power. More friction/resistance/non-conservative/dissipative force. Less speed. A steady throttle at lean will equal acceleration as you stand it up due to less resistance. But no faster than you were before you leaned over with that same throttle. Yes a larger circumference wheel will cover more distance for a given RPM, however, the RPM is not a given here, the throttle is. As you lean the bike over, wheel speed and RPM may relatively increase due to a smaller circumference wheel, but the POWER remains the same. Conversely, given that same constant throttle/power, when you stand it up, any RPM's gained due to that decrease in circumference will be lost again. The power input does not change. Gotta run. Cheers. Quote Link to comment Share on other sites More sharing options...
Robsalvv Posted February 3, 2007 Report Share Posted February 3, 2007 Hi Racer. I think we're discussing the same side of the coin... I understand about the cornering forces - I just didn't appreciate that they were as important in the "slowing down in a corner" process. I figured that the wheel diameter effects were more important. Your post highlighted an important subtlety that I should have realised under my own steam! Throttle position doesn't necessarily equate to engine revs!! e.g. going up an incline with the same throttle position, the bike will slow down due to the load. Those cornering forces are basically a load. If you don't adjust throttle when you tip in, the bike will slow due to the extra load AND due to the smaller effective wheel diameter. I remember discussing this in a level 1 CSS class recently (in Australia), and that's where I got the impression that the wheel diameter issue was all important in understanding why a bike slows down in the cornering process for a given engine revs. Perhaps Steve Brouggy dumbed the discussion down for simplicity... At any rate, I'm happy to have broadened my understanding on the issue. I guess this highlights how even more important rule #1 is. Rock on! Quote Link to comment Share on other sites More sharing options...
racer Posted February 3, 2007 Report Share Posted February 3, 2007 Cool man. I started to use the hill as a load (or lack of load if going downhill) as an analogy but for some reason I thot it might be confusing. That's great that you came up with it! I wondered however if you might come up with a two stroke just under the powerband picking up rpm's due to smaller wheel circumference in the corner to get onto the pipe and thereby gain more power and speed mid-turn... Yeah, I think the bigger wheel/smaller sproket thing comes into more play when gearing for redline or calculating speed in gears for alternate tranny sets on a roadracer. Or maintaining drive ratio when changing to a different tire size. Or getting the power down better on a dragster. So, now we are left with the question of the bike eventually settling into a "steady state"...or not? I'm leaning toward "yes" as the norm. However... Technically I think it is still somewhat case sensitive. In the given terms and conditions of the original thought experiment, if you try to climb a steep hill starting off at 80 kph/50 mph in sixth gear you could eventually stall if the hill was steep enough. The throttle and power delivery aren't much off idle in that scenario. But open it up to 100 kph or more and I think you'd have to climb a ski slope to stall. Although cornering loads in a given corner/radius are in fact dictated by speed. The faster you go the steeper the mountain gets... Damn. OK I"m done. G'night. PS I always thought the trick was to grow old without growing up...... Quote Link to comment Share on other sites More sharing options...
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