The 2 the Max Project

[hodakamax]

Just for fun I weighed the flywheel which came in at over two pounds which is about 1% the total weight of the vehicle. Not insignificant. The flywheel, whether CDI or standard ignition, still nibbles away at the F (Force) part of our equation as in F=ma. Creating electricity from spinning magnets takes power from our driving force namely the engine. Removing this system will have a two-fold effect on our equation.

Hey, thanks Jack and Gang for your comments and research. I am taking notes!

Maxie

[Hydraulic Jack]

Just to put some perspective in here, F=MA is a statement of how much force is needed to accelerate a given mass. Assuming you are more interested in top speed and not low elapsed times, once a machine approaches or achieves its top speed, acceleration drops to near zero, which means that the force needed to maintain forward motion decreases as acceleration decreases. Not that the weight of the machine isn't important. It's just that it isn't the holy grail either. At speeds approaching 100mph on a small displacement bike, you will get a lot more bang for buck from aerodynamics than from a few less ounces of mass.

[hodakamax]

In F=ma we must consider things like air resistance and friction as negative forces. They are reducing the forces available. Without any negative forces our racer would maintain the speed it had been accelerated to such as in a space environment. If engine force continues our racer would always continue to accelerate but in our earthly environment we are still limited to the F=ma equation. Acceleration is always dependent on our mass and how much force we have. We have to reduce the mass and/or get the sum of the forces increased by things like streamlining and reducing mechanical friction or more power. We can't go any faster in our environment because all our forces have been cancelled out by minus forces. When forces become net zero were going as fast as possible, acceleration is zero.

I always have to write all this down to explain it to myself. That was fun.

Maxie

Ok, a little side note. We should mention that F=ma is Newtonian physics. Relativity would come into effect as our racer approaches the speed of light after accelerating with the same engine force. More and more force would be needed as we approach the speed of light which would be the ultimate speed limit. F would have to be infinite to maintain the speed of light or our mass would have to be zero. Hey, just quoting Einstein, It's not like I understand all of this.

[Bill2001]

What is needed here is the Sagan corollary. Get out. Ride. Enjoy. Repeat.

[matt glascock]

Just to be a bit geeky and trot out what I can remember from college physics (fuzzy at best, but a required premed course), a more apt formula than the classic F=MA basis for Newtonian mechanics might be the equation used to determine terminal velocity. Of course, this equation is used to determine the terminal velocity of an object falling from height, but many of the principles contained in the equation remain consistent and applicable. The equation states that:
Terminal Velocity = the square root of ((2 x M x G)/(p x A x C)) where M = mass, p = density of the fluid being moved through, A = cross sectional area perpendicular to the direction of movement, C - drag coefficient, and G = acceleration (in this case, the 9.8 M/S x S due to gravity but in a speed run, the propulsive force of the 100 cc motor - you could replace G with F/M where F = propulsive force resulting in the numerator being (2 x M x F/M)). Any manipulation which decreases the factors within the denominator will increase the terminal velocity. Moving through lower density air, decreasing the surface area (streamlining) and drag coefficient (which applies to aerodynamics as well as the running components of the machine) will all allow a higher terminal velocity. Similarly, enhancing the ability of the motor to accelerate through higher revs and taller gears will positively effect the numerator and thus the terminal velocity. Lets just skip over the effect of mass for now. Indeed, none of this is as interesting as the Sagan Corollary provided by Bill, but I need to reconfirm my status as an over educated s#*t head.

[Hydraulic Jack]

Well, you wouldn't replace the gravity constant with F from Newton's second law of physics, because F isn't necessarily a constant, nor is it necessarily related to achievable speed, but I agree that the terminal velocity formula would be more relevant.

Given that there are a number of variables involved, let's say that a given engine can produce a specific amount of power at a certain rpm. Doesn't matter much what those numbers are, just to know that they exist. If it takes 10 horsepower, of if it takes 10 foot pounds of torque to maintain rpm at speed, what that speed can ultimately be is then a function of gear ratios and tire diameters. If you limit the motive source to, as an example, 10,000rpm, it doesn't matter if your engine make 10 horse power or 100 horsepower, you still won't go any faster than what your final drive ratios permit, assuming you can get maximum rpm in top gear. You might get there faster with a lighter bike and you might maintain it easier, but you won't go any faster.

It is enough, then, to simply have enough power, expressed as you will, to maintain a given target rpm in top gear, and your speed will be the math product of those rpm and gear numbers. At that point, F is no longer relevant, nor is A, nor for that matter is M. Instead, you will need only the amount of power needed to match parasitic drag from all sources. Such as air, the fluid through which you ride.

I understand that making things lighter will make the job of going fast easier, but having spent some time on a motorcycle in excess of 100mph, I know that getting out of the airstream is more important than tuning for that last have a horse. If that same bike weighed 150 pounds instead of 320, it would still be limited to 110mph unless I changed either the ability to rev at the upper limit, or the gears or tires, because once I hit top rpm for that engine in sixth gear, 110mph is all there is.

[taber hodaka]

So? --------Clarence

[matt glascock]

Hey Jack, you've illuminated the weakness of direct application. Here's my thinking - likely wrong. Yes, the force of gravity is a well-accepted constant. Its the motive force which accelerates a falling body to the ground. In a moving motorcycle, the engine is the motive force propelling the bike forward. In a loose association with reality, I made the force generated by the engine a constant presupposing it is operating wide open at its most well-tuned state and with optimal gearing and tire diameter. Flawed yes, but a feeble attempt to make the terminal velocity equation work. Other than that, you have made an excellent and deep dig into the nitty and gritty of the effects to overcome in the quest for pushing out the point where the worlds of force and resistance collide. Nicely stated.

[Bill2001]

Might be relaxing to watch "The World's Fastest Indian" to realize how good we have it...

[hodakamax]

Wow! What a fun discussion! In my simple scenario and example of F=ma, I was trying to show that each component indeed does have an effect on our record run whatever the vehicle and/or force. F will always be forces acting for or against our goal. Gravity, fluid resistance, friction and thrust are all plus or minus vectors of force. In the quest for our goal these are the factors that can be simply stated. A lot of variables are falling into the force category.

In our simple equation, gearing, horsepower, tires, barometric pressure, fuel, time, gravity and other seemingly muddying factors are relevant in achieving the total force, but the total force is one number, the sum of all the forces, F.

Since our equation only has three components we cannot discount the importance of each one or we're getting off the path. Mass is one of the components and for a record attempt should be reduced with equal importance as it's directly proportional to the force and acceleration. Acceleration is change in velocity and is how we get to our record number by applying force to a mass.

Ah, a cup of coffee, an intellectual discussion and I'm ready for another great Day!

Maxie

By the way, The Worlds Fastest Indian story is ever-present when working on the project. What a fun movie.

[matt glascock]

Agreed Maxie. What is interesting is that while we are discussing these principles in terms of the entire bike and rider moving along on a speed run, they apply equally, with certain adjustments in the variables, to all moving parts of the motorcycle. For example, within the motor, the resistance to optimal high-performance output (MAX power ) is supplied by the friction at the interface of any moving part to anything else. The upshot being the need to address all these individual moving systems with the same attention to all the individual variables effecting ultimate speed performance as you do for the bike as a whole and to optimize the numerator factors and attenuate the denominator factors since your goal is to achieve ultimate velocity performance by the bike and pilot. This concept readies the table for discussions on enhancing internal engine, drive train, and wheel hub/axle lubrication, heat dissipation, and on and on and on. Good stuff!

[hodakamax]

Thanks Matt, a good discussion for sure. I love this stuff. I'm not overly educated but I am a science geek and I do like to stir things up. I lost a very good friend last week and my memories of him will be drinking a wine or two and discussing the origins of the universe and other mind blowers like quantum physics. Not that we were qualified but interesting questions were asked and discussed. All good for the brain and we had a good time. There's more to life than TV we concurred. All strange but fascinating. It's been fun discussing practical applications such as how fast we can go with what we are limited to and Newton figuring this all out years ago to help us stay on track. Wow.

Max

[taber hodaka]

wind resistance I think is a big factor, and wheel and tire size. I think Jack could have been a professor or maybe was at MIT. ----------------- Clarence

[matt glascock]

My condolences, Max. Hopefully the happy memories of times as you've described will replace the sorrow you currently know. Also, I agree - these are great discussions.

[hodakamax]

Ok, back to reality and hardware developed to cheat the ever increasing wind force. These posture changing footpegs hopefully will allow the rider to be partially prone and reduce the frontal area of the rider. Sounds good in theory, whether I can fold up on this thing remains to be seen. Our recruited rider will have to be light and small but first things first.

Finally, one rear footpeg bracket has been fitted and the shifter linkage has been fabricated and assembled. There's still cosmetic work to do here but I must say that the mechanism really shifts smooth. It's time to mount the other side and figure out this proposed cable rear brake idea. One step at a time.

Maxie

[Hydraulic Jack]

Matt,

What you are describing would fall under Newton's first law of motion. Objects at rest stay at rest until acted on by external force; objects in motion stay in steady motion until acted on be external force.

The external forces here would be largely drag. Seals, bearings, gear faces, tires, all turning energy into heat, which is a parasitic by-product constituting force applied against the object in motion. If you want to hunt for small fractions of parasitic drag, you can do such things as leaving out wheel bearing seals, and using extremely light weight grease, or even light oil, on the bearings. Not what you would do with a motocross bike, but for a one run, two run speed attempt, why not. It's just a maintenance hassle but can reduce rolling resistance.

Tires should have little or no tread. Flexing tread causes tires to produce heat, which is an energy loss. Tires should have very high pressure to limit flexure. It makes them tedious to ride, but reduces drag. You will notice that your average racing bicycle has ridiculously skinny tires with extremely high internal pressure. There is a reason for this.

Frontal area should be reduced where possible, and contoured where the area can't be further reduced. Spoke wheels generate a huge amount of drag. It's like turning two large, inefficient fans beating at the air, creating turbulance.

Even a small amount of fairing in the area above the front tire and in front of the rider can make a large difference in reducing drag, as can a fairing behind the rider which returns air flow to the slip stream with a minimum of turbulence. Consider the tear-drop shape. This is a very efficient aerodynamic shape, blunt end to the front, slender end to the rear. Even kids on bikes these days have helmets shaped this way even though they don't go anywhere near fast enough to make use of the shape.

And so on. These areas of design will gain more in the end than will shaving off a few ounces, even though you do everything you can in all areas. But what you look for is return on investment. How much effort, how much return. Go for the big ticket items first, then work your way down to exotic metals.

[racerclam]

I just noticed that your building for building top speed , cool! Here is a customer of mine that just set a world record in August this year for 50cc class with his Honda NS 50 . I did the porting and carb work. I'm kinda proud 8o) He definatly got the stream lining thing figured out. You can see pictures that are more clear on the testimonial page of my web site

Rich

[racerclam]

Oh and The Bike that Greg Watkins built went about 87mph , it kept sucking the carb bowl dry and would have to recover a few times during the run . So I built him a large bowl carb but he hasn't gone back out with it

Rich

[Bullfrog]

Rich,

I may be missing something, but it looks like rising fuel levels will "trap" an air bubble in each of the two added "wings" of the re-worked float bowl . . . and that would limit how much additional fuel will be available. Is there some feature which allows the air in the new "wings" to vent to the original float bowl area?

Was higher flow float valve not an option?

On a VERY closely related digression, one of my mentors at PABATCO once told me the story of how unlimited drag racers had all seemed to bump into an invisible "wall" on top speed. It seemed that no matter what they did, they couldn't seem to gain any more significant speed/acceleration until . . . someone simply installed larger diameter fuel delivery hoses from the fuel tank. The details are foggy . . . but it might have been Don Garlitts???? (and he might have won the national championship on that idea?)
Ed

[racerclam]

Ed there was drilled holes in the upper part of the walls that were not there yet in the pic , Good call though 8o) and the needle valve was drilled as large as possible .136" and the pet cocks also opened up. . Running 5 miles at wot makes one thirsty. Garlits was a wiz, in 1974 he set the world top fuel record at 5.73 seconds and 243mph. Slow for now days. It was cool the we had that car in our auto shop for us to check out and sit in , at So NV Votech. He also pioneered the rear engine dragster after blowing his foot off

Rich

[hodakamax]

Here's the other side mounted up with a front brake plate with a cable boss all modified to fit the rear hub. This in-between linkage has me baffled for the moment and I'm accepting clever ideas, even hydraulic. A brake rod is also not out of the question with a pivot where the old foot brake lever was.

Maxie

[viclioce]

Just looking at it from this one photo, I would guess that if you can change the pedal attachment point so it’s back about an inch to inch and a half further, that you may be able to do it by offsetting the brake rod with two, 90 degree bends, as long as you reinforce the 90 degree bends with something to keep the brake rod from stretching back out. Just a 90 degree triangular piece welded in place, or even just some additional round stock welded in place to hold the 90 degree angle. Seems like that should do the job simply enough. What do you think, Max? Victor

[hodakamax]

Ah, thanks Victor. I think I'm starting to visualize how to tackle the problem. I have to look at things for a while. I think by moving the foot brake arm 180 degrees where it's pulling rather than pushing and installing a bell crank pivot near where the old brake pivot was, it will be a straight pull to the rear hub with a rod much like the stock set-up.

The vertical movement of the swing arm is what complicates the problem for a direct hook up. By moving the transfer point bell crank near the swing arm pivot as in the stock position should alleviate the problem methinks.

Max

[Bullfrog]

With the brake lever pivot point and the brake rod attach point being almost at the mid-point between the swing arm pivot and the rear axle . . . swing arm movement makes a brake rod pretty problematic. This may indeed be a situation where cable or hydraulic actuation is called for.

Your last post suggests that you are thinking about linkage from the brake lever actuation arm forward to near the swing arm pivot and then linkage from there back to the hub brake lever? Or did I misunderstand the paragraph? Seems like a lot of linkages - but if the various pivots and Heim joints are pretty "tight" (not much free play), then it may be as good as (or better than) a cable setup.

Ed

[Bill2001]

Looks good Max.
I thought that a cable-actuated rear brake was on the menu? As BF notes, the relationship betw the brake rod and the swingarm pivot is critical.
At any rate, the use of bellcranks and tight pull rods is a good setup. Large-scale R/C aircraft use heavy, snug components so you may be able to swipe ideas or hardware from there.