Darryl Noble said:
RalphMy taste of music is probably not to good but I do prefer the Willie & crew’s version.
And the road will go on forever,
Till next time, cheers. The old fardt in Ore-Gun
from gearing to highway men??? GEEEEEEEEEEEEEEEEEEEEEEEEEEEEz just keeps getting better at least no bashing going on, I guess that’s some consolation!! The Regal
Greg Elmassian said:
(http://www.elmassian.com/images/stories/misc_train/derail.jpg)
Greg
/Derail ON Heck, this thread could be an LSC record. Can’t stop it now.
Ralph Berg said:
I will expand further. Torque and horsepower are two different animals. An optimal gear ratio is dependent on both the application and the motor specifications. For optimal pulling power, gearing has to be matched to take advantage of the torque curve of the power plant. Even if the torque curve matches the horsepower curve in electric motors, pulling power is going to be different at different engine rpms. Peak horsepower for internal combustion engines is achieved at high rpms. Peak torque is usually achieved much lower in the RPM range. Cars and trucks have multiple gear ratio transmissions to keep the engine closer to the power curve of the engine. Gearing matters just as much to pulling power as it does to top speed, as well as low speed. Ralph
Ralph, your way of thinking is generally correct, but please let me help you with some detailed comments: >I will expand further. >Torque and horsepower are two different animals. They indeed are different physical quantities but the relationship between the two is very simple. You only need rotational speed (rpm) to link one with the other:
(http://upload.wikimedia.org/math/a/2/9/a2907f37b56e0bde1ea3ae32e23af7be.png)
As you can see from the above equation, you can derive power from torque using rotational speed. If you do this, you will see that the maximum power in electrical motors is achieved at half the maximum rpm at half the maximum torque. >An optimal gear ratio is dependent on both the application and the motor specifications. >For optimal pulling power, gearing has to be matched to take advantage of the torque curve of the power plant. I suppose you mean pulling effort or force, not power. Also, strictly speaking you need to define what you are optimising, otherwise referring to an ‘optimum’ is meaningless, in this case I believe you mean maximal not optimal. In the case of torque on internal combustion engines, there is a maximum torque which is delivered at some rpm value and this is perhaps what you have in mind. Things are different in an electric motor. This is because in electric motors torque is (linearly) increasing with decreasing rpm. This is very different from internal combustion engines for which torque quickly drops at low rpm. This is also the reason why electric motors do not require gear boxes with multiple gear ratios, they deliver maximum torque at 0 rpm (stalled) and maximum power at half of their maximum rpm. Please note that gearing has no effect on the power delivered to the wheels, if you rescale rpm by a certain factor, you need to rescale the torque by 1/factor and the product of these two is simply 1. This is consistent with the law of the conservation of energy - the power delivered by the motor is the same as the power delivered by the wheels with or without any gearing in between (we assume no energy is lost in the gears). The gearing will only determine the speed at which you can use the particular level of power - this is why you should use maximum desired speed as a design criterion for using your available maximum power. This also means that, as you suggest, one only needs to look at the torque in order to determine acceleration (equivalent to pulling force divided by the mass - weight of the locomotive or the entire train depending what is your design criterion.) In electric motors this consideration is facilitated by the linearity of the relationship between torque and rpm - the highest torque is achieved for the smallest rpm, down to zero rpm. As gearing simply multiplies the torque delivered by the motor, you can use the torque up to the limit determined by the slipping of the wheels or the limit of stalling, whichever you achieve first with your motor - gearing - locomotive weight combination. There is no point in increasing the torque by increasing your gear ratio if your wheels slip, you will not be able to pull more nor will you accelerate faster. In other words the gearing will only affect your acceleration and pulling force up to the point when the wheels start slipping - this is why you should use the weight of the locomotive and the torque of the motor to calculate the gear ratio which will provide the desired acceleration (or pulling force) to your locomotive. >Even if the torque curve matches the horsepower curve in electric motors, pulling power is going to be different at different engine rpms. Torque line never matches the power curve on electric motors. Torque vs rpm relationship is linear, power vs rpm relationship is quadratic (inverted parabola). The relationship is given by the formula above. Please check the plots on page 9 of this thread. To come up with a motor/gear ratio design, you need to do two things 1) determine what is the maximum acceleration which you want to achieve up to the point of slipping - this will be determined by the maximum torque of your electric motor, gear ratio and the weight of the locomotive 2) determine the maximum speed and load which you want to achieve - this will be determined by the maximum power of your motor. Depending on some additional constraints, such as the mode of operation (continuous etc), heat dissipation (heat sink or other cooling etc), you should work with say 75% - 95% of the maximum values. For example if you want to use your motor on an a plane you will want to use the lightest motor possible so you will have to use values very close to 100%. Generally, except for some very specific applications, it will make no sense to use only say 40% of the available power in your design, because you could buy a motor half the power and still use only 80% of its total power under maximum speed and load. You can see these principles used and applied to an example of a Pittman 9000 series motor on page 9 of this thread. Please note that in the case of the K-27 locomotive, the example motor/gearing combinations considered provide much more torque and more power than the locomotive can utilise due to its limited weight, therefore all design criteria are significantly simplified and only the maximum speed remains as the parameter of choice. In a full size scenario, you usually do not have so much spare power and torque, therefore design criteria are much tighter. >Peak horsepower for internal combustion engines is achieved at high rpms. Peak torque is usually achieved much lower in the RPM range. >Cars and trucks have multiple gear ratio transmissions to keep the engine closer to the power curve of the engine. >Gearing matters just as much to pulling power as it does to top speed, as well as low speed. For the reasons I listed above, you cannot compare internal combustion motor driven vehicle with electric motor driven vehicle. Electric motors do not require multiple gear transmission, and this is why trams, or electric locomotives do not have such. Gearing will influence maximum speed and acceleration. On the K-27 it will only influence maximum speed and nothing more because the wheels slip when you apply too much drag (or accelerate too fast). If the locomotive wheels slip this means that there is more torque than the locomotive can use - there is no magic here, contrary to what some people want you to believe. Best wishes from Tokyo, Zubi
Thanks, Zubi,
I know more about electric motors today than I did yesterday.
You said gearing only affects acceleration and top speed.
Excuse my ignorance, but are you saying too high a gear(numerically low), will not create wheel slippage on acceleration?
Ralph
Ralph, Let us look at it like this. Slippage is a function of the following variables: Mass ‘m’, (static) friction coefficient ‘mu’ and the force ‘F’ tending to cause (horizontal) movement. Force F is determined by the torque ‘tau’ and the wheel diameter ‘r’, as F = tau / r. Once we fix the variables: mass, friction coefficient, wheel diameter the only which remains is torque. So torque is the only determinant of slippage. Once torque is too high your wheels will start slipping. “Too high” means that the force F = tau/r tending to cause (horizontal) movement (that is the drag), is greater than the friction force Ff = m x g x mu, where m is mass g is gravitational acceleration and mu is the friction coefficient (m x g is simply weight of the vehicle). Now this too high may or may not happen depending on the torque at the wheel axis which is a product of the torque on the motor axis times the gear ratio. If the gear ratio is lower numerically, the torque on the axis is lower and you may fall just below the threshold of slippage if your gear ratio is numerically low enough - or if you apply lower voltage to your motor which also lowers torque. I hope this helps a little, Best wishes, Zubi
Zubi,
With that explanation I can say I understand what you’ve been talking about now. At least the post before this last one. 
David
David, thanks, I am glad to hear this. As for the last post. I will try to illustrate this to make the story more accesible, but now I have very limited time - sorry about that, Zubi
So Zubi, when are you going to come up with some actual real life testing of the K-27 to put some flesh on your theories?
No real life testing means a theory remains just a theory.
Zbigniew Struzik said:Actually, I understand the concept of less slippage with higher gearing as well, just not the formulas.
David, thanks, I am glad to hear this. As for the last post. I will try to illustrate this to make the story more accesible, but now I have very limited time - sorry about that, Zubi
David Ross said:Meaning of course that proves our point.Zbigniew Struzik said:Actually, I understand the concept of less slippage with higher gearing as well, just not the formulas.
David, thanks, I am glad to hear this. As for the last post. I will try to illustrate this to make the story more accesible, but now I have very limited time - sorry about that, Zubi
Lower the gear ratio and improve the traction. At low speed.
mike omalley said:
Hmm. As an ignorant but interested novice, it seems to me that Zubi has made his point well--the motor is powerful enough that changing the gear ratio would not increase the number of cars the K27 would pull. As I read it, this is what Stan Ames claimed in the original quote.There are several videos on Youtube of the K27 pulling cars VERY slowly, for example this one, posted by Stan Ames, who apparently is evil for some reason I can’t quite grasp and may have rigged the thing in some way
http://www.youtube.com/watch?v=Z1eW4phOT4E
But then there are other videos showing the K27 pulling quite nicely at a low speed while also denouncing the thing as badly geared! Huh?
http://www.youtube.com/watch?v=VP9Y7itCtOw
The video above seems to be demonstrating that the K27 can do precisely what the comments claim it can’t do!
I’d love to try one out, and see if I could figure out what the fuss is.
3 amps?
What current are the pins on the Ames socket capable of handling?
Sincerely,
Joe Satnik
Zbigniew Struzik said:And, that brings us back to "I give up." It's no longer worth fighting about with this kind of tripe being broadcast. But don't think me weak, I have some good historical precedent for knowing when to bow out, at least publicly.... consider this:
;-))) Mike... You may not need to buy the K to understand that, in all likelihood, the whole fuss is because Tony's business hurts. This may be due to the following reasons: 1) he is not capable of delivering the technology to cope with currents around 3 Amp or so. 2) his client base is unwilling to pay the extra $$$ for higher current devices or, alternatively, his profit margin sunk... If one is unable to win using 1) technology 2) price, one may be tempted to resort to 3) propaganda. Cottage industry strives on tuning and little upgrades but it suffers if there is nothing to tune or upgrade. Now please imagine for a minute a scenario as Terry describes where he fails to see any problems with his Bachmann products. http://www.largescalecentral.com/LSCForums/viewtopic.php?id=10204&p=2 and this means no new gears, no new drives, no new fixes... This scenario is a complete disaster for the cottage industry, so if there are no problems, they need to invent some!! Best wishes from Tokyo, Zubi
[i]I, Galileo, son of the late Vincenzo Galilei, Florentine, aged seventy years, arraigned personally before this tribunal, and kneeling before you, Most Eminent and Reverend Lord Cardinals, Inquisitors-General against heretical depravity throughout the entire Christian commonwealth, having before my eyes and touching with my hands, the Holy Gospels, swear that I have always believed, do believe, and by God’s help will in the future believe, all that is held, preached, and taught by the Holy Catholic and Apostolic Church. But whereas – after an injunction had been judicially intimated to me by this Holy Office, to the effect that I must altogether abandon the false opinion that the sun is the center of the world and immovable, and that the earth is not the center of the world, and moves, and that I must not hold, defend, or teach in any way whatsoever, verbally or in writing, the said false doctrine, and after it had been notified to me that the said doctrine was contrary to Holy Scripture – I wrote and printed a book in which I discuss this new doctrine already condemned, and adduce arguments of great cogency in its favor, without presenting any solution of these, and for this reason I have been pronounced by the Holy Office to be vehemently suspected of heresy, that is to say, of having held and believed that the Sun is the center of the world and immovable, and that the earth is not the center and moves:
Therefore, desiring to remove from the minds of your Eminences, and of all faithful Christians, this vehement suspicion, justly conceived against me, with sincere heart and unfeigned faith I abjure, curse, and detest the aforesaid errors and heresies, and generally every other error, heresy, and sect whatsoever contrary to the said Holy Church, and I swear that in the future I will never again say or assert, verbally or in writing, anything that might furnish occasion for a similar suspicion regarding me; but that should I know any heretic, or person suspected of heresy, I will denounce him to this Holy Office, or to the Inquisitor or Ordinary of the place where I may be. Further, I swear and promise to fulfill and observe in their integrity all penances that have been, or that shall be, imposed upon me by this Holy Office. And, in the event of my contravening, (which God forbid) any of these my promises and oaths, I submit myself to all the pains and penalties imposed and promulgated in the sacred canons and other constitutions, general and particular, against such delinquents. So help me God, and these His Holy Gospels, which I touch with my hands.
I, the said Galileo Galilei, have abjured, sworn, promised, and bound myself as above; and in witness of the truth thereof I have with my own hand subscribed the present document of my abjuration, and recited it word for word at Rome, in the Convent of Minerva, this twenty-second day of June, 1633.
I, Galileo Galilei, have abjured as above with my own hand.[/i]
I feel about the same way at this point. Particularly if you consider that legend says when he read this publicly, that at the end, Galileo was heard to say, under his breath, “But, it DOES move!” except that in my case if in fact it does move, it’s not because it came properly equipped to do so.
Matthew (OV)
Gallileo–interesting if somewhat grandiose choice
Gallileo was the one who was using scientific, empirical evidence, while the church were using common sense real world experience. Gallileo was supportng Copernicus, who advanced the wild theory that the earth moved, while common sense real world experience told you the sun moved around the earth, contrary to your wild theory. That would seem to put Zubi on the side of Gallileo, and science, and Tony on the side of the church, a side I’m sure he would not want to be associated with
My name was used in some replies–I just want to make it clear that I’m not insulting anyone, accusing anyone of base motives, or impugning anyone’s honesty. I just wanted to figure out what was going on and thank to some offline emails, I have.
The one thing this thread has convinced me to do is stay out of 1:20:3!
All I can say is… 16 pages? I now really appreciate my stupidly simple Mack’s, they just run & run & run…
(http://gold.mylargescale.com/vsmith/Whadahellizit5_painted_01.JPG)
I always knew that Tony was a closet believer.
Has anything been decided? Is it safe to come in out of the rain?
