Another gearbox discussion

[just-an-allusion]

I'll throw in that they had a quantity issue as well.
The numbers they needed to make were well under the minimums the majors were even willing to look at especially for a unknown company.

Whomever ended up making the gearbox it was going to be far more expensive than any other because of 1. difficult large shifting ratios and, 2. no high volume price breaks.

That's one of the problems that often hamstring new technologies/inventions, i.e., research and development-you've got to find out what works before you can mass reproduce it.

 

[power]

Good point. probably possible. with electric motors and those kind of small resonance characteristics due to the motors natural frequencies could be an issue with gears with some backlash. so, a flywheel could be usefull there. I dont think it would solve any issues with the changing of gears. actually, the less inertia in that regard, the better. less force on the teeth if the rpms were mismatched as they are with sequential gear boxes.

mk

With regards to the flywheel (or lack thereof), I don't think people are getting my point (or maybe I am wrong about it), but I think one thing a flywheel does is smooth out torque delivery. Lets say the PEM has some high frequency noise and the torque delivery fluctuates very rapidly with rapid, subtle variations in torque. A flywheel slows down the rotational changes so the gears don't experience those "fluttering fluctuations". With no flywheel the eMotor may be able to "micro-jackhammer" at the gear teeth during shifts. This is just my own (perhaps half baked) pet theory.

JB alluded to the fact that there were multiple "modes of failure" for the DT1.0 transmission, so we are probably only "scratching the surface" here.

 

[TEG]

Yeah a flywheel would definitely work against their goal of trying to get the eMotor to change RPMs as quickly as possible. It sounds like the existing mass of the rotor was too much as it is.

If they ever need variable ratios it would be good if they found a CVT that could work.

 

[just-an-allusion]

Despite the mindset expressed here (just as it is in a greater extent with Tesla and just about any other other EV manufacturers), though in keeping with this particular train of thought for the purposes of relaying an ideology in a manner in which it would be understood under the present frame of mind, I'd like to point out that the inherent proprietary operational disposition of any (electric) motor is in a single "gear" orientation. Any attempt to implement additional "gearing" would only serve to overly complicate a predominantly simple (singular) functional aspect of the technology, i.e., "over thinking" the basics, as previous history with the development of this technology demonstrates.

To this end, IMHO, my thoughts on this issue are that Tesla (or any EV manufacturer) should abandon any efforts to devise an "economical" method (note that I haven't mentioned that it could not be done, only that it would not be financially feasible from any reasonable perspective at this point in time given the exorbitant material cost of implementing a multi-geared transmission) as an ill-conceived pipe dream and stick with the time proven, standard method of operation commonly associated with motors, i.e., one speed/"gear".

With that said, it is my view that if it is the intent of any EV manufacturer to actually produce a multiple speed motor, they should do so by working to elaborate on/to evolve the parent technology while strictly adhering to the confines of that particular technology and not attempting to implement the technology of a completely differing discipline (electrical as opposed to mechanical), in the process avoiding pollution of an intrinsically pure technology (electric) with another (mechanic) that is atypically dirty like some form of bastardized cross-pollination.

Following this train of thought, instead of beating the metaphorical now long dead horse, if an EV manufacturer wishes to add differing speeds/"gears" to their motors, why not merely stick to the tech and simply add additional "poles" with associated "synchros" to "govern"/"modulate" their activation/operational "frequencies", hmm"?"

Why not merely go to "source" instead of outsourcing"?!?" Pass it along please.

 

[doug]

^^^^

I really don't see what you're going on about here. Cars are inherently mechanical objects and you still seem to be missing the point of gearing.

Or is this "reduction gearbox" more so a practical application as a means of "de-tuning" the motor so that no one kills themselves/Tesla drivers cannot outrun the police? Just curious.

Simply put, reduction gearing allows for more torque at the wheels by providing "mechanical advantage". This is a concept worth reviewing.

 

[just-an-allusion]

^^^^

I really don't see what you're going on about here. Cars are inherently mechanical objects and you still seem to be missing the point of gearing.

Simply put, reduction gearing allows for more lateral force at the wheels by providing "mechanical advantage". This is a concept worth reviewing.

Are you referring to LF as it equates to a tire's properties of deflection and recovery during operation as it relates to peak-to-peak, first harmonic, second harmonic, and higher-order harmonics?



Or another form of LF?

 

[just-an-allusion]

Granted...

Cars are inherently mechanical objects...

...In the totality of their design, yet the sole feature that I'm alluding to is that which concerns it's power plant/motor which, from the overview, is wherein the troubles lies, is it not?

Sometimes progress comes in the form of baby steps instead of leaps and bounds, as we would all wish.

 

[doug]

Are you referring to LF as it equates to a tire's properties of deflection and recovery during operation as it relates to peak-to-peak, first harmonic, second harmonic, and higher-order harmonics?

No, I suppose should have said linear force as in horizontal, non-rotational (lateral was perhaps a confusing word to use in this context). Actually, I should have taken it back one step and said torque but that tends to be a harder concept. Torque is converted to linear force through the "simple machine" of the wheel. Mechanical advantage, sometimes known as force multiplication, allows you to get more force (or torque) at the output than you supply at the input at the cost of distance (or rotation). Energy is conserved.

 

[just-an-allusion]

No, I suppose should have said linear force as in horizontal (lateral was perhaps a confusing word to use in this context). Actually, I should have taken it back one step and said torque but that tends to be a harder concept. Torque is converted to linear force through the simple machine of the wheel. Mechanical advantage, sometimes known as force multiplication, allows you to get more force (or torque) at the output then you supply at the input at the cost of distance (or rotation). Energy is conserved.

In other words, you're concerns are centered on transferring the rotational force of the motor, the "torque", to the wheels/drive train, correct?

If so, please note that nothing mentioned in the technique that I alluded to above refers to transferring the workload from the motor to the pavement, only in modulating/regulating the rate of the rotation of the motor, it's "speed", at any given time since that was the topic being discussed.

As for actually transferring the workload to the pavement...really, how hard could it be to facilitate?

Think "propeller".

 

[doug]

In other words, you're concerns are centered on transferring the rotational force of the motor, the "torque", to the wheels/drive train, correct?

Well that is, by definition, what a transmission (or a gearbox) does, which is the topic of this thread. My concern (i.e. my reason for replying) is that your posts suggest gaps in understanding. I've suggested some topics you could look into to fill those gaps.

... the sole feature that I'm alluding to is that which concerns it's power plant/motor which, from the overview, is wherein the troubles lies, is it not?

If with all that you're trying to say Tesla should make a better motor, I'm sure they're working on it. What they have now with DT1.5 is working pretty well, though.

 

[just-an-allusion]

Well that is, by definition, what a transmission (or a gearbox) does, which is the topic of this thread. My concern (i.e. my reason for replying) is that your posts suggest gaps in understanding. I've suggested some topics you could look into to fill those gaps.


If with all that you're trying to say Tesla should make a better motor, I'm sure they're working on it. What they have now with DT1.5 is working pretty well, though.

No, no, no.... It's not that I'm missing some "gaps in understanding", it's that I'm merely leaving out what I view as unnecessary components, the results of an attempt at cross-application integration of two clearly divergent technologies.

What I'm suggesting/questioning is why not merely use the "motor" itself as the "transmission" (multiple "poles"=two birds...one stone) instead of (IMHO) needlessly over complicating a basically straight forward process of poer management?

It would be helpful if you had some background in/experience with the varieties of induction motors...do you?

 

[donauker]

It would be helpful if you had some background in/experience with the varieties of induction motors...do you?

Based on your posts I would estimate that my understanding of AC inductions motors is greater then your understanding of the part played by reduction gears.

I would be very interested in seeing your motor specifications for your AC induction motor which will produce approximately 8 times the torque of the motor built by Tesla Motors. Please include weight, size, efficiency and the method of cooling used for the rotor.

 

[ChargeIt!]

Ok ... pardon me for "gearing in" ... but "inspiration" is not giving me the proper "inspired drive" to satisfaction ...

I would agree that direct drive is the most efficient and simplistic ... but you need a REDUCTION gear. Let's try some simple geometry and 'rithmetic with a motor directly driving the wheels:

Assume at 125 mph your motor turns 14,000rpm. Meaning your car travels 125 miles or 125*5,280 feet in one hour, or 125*5,280/60 feet per minute. Since your drive wheels are thus traveling 11,000 feet in one minute while the 14,000 revolutions happen, each revolution is 0.79 feet. This would match the circumference of your drive wheel, or 12*0.79 measured in inches or an equivalent 12*0.79/PI inches DIAMETER.

Sorry but I would prefer not to run my Tesla Roadster on 3.0 inch wheels which spin at 14k rpm.

I would prefer a final drive ratio of .... oh say ... hmmm ... what would be a nice number ... how about 8.32 ? That would allow me to drive a single-speed gear reduction transmission on wheels with 8.32*3.0 = 24.96 inches diameter. I think an 17" wheel with Yokohama 225/45R17 tires might just work out (45% * 225 mm * 2 converted to inches plus the wheel diameter).

Did I miss inspiration's point and am I way off subject ?

(Notes: 1) No insults intended; 2) my cursory search did not find the actual final gear ratio for the Tesla Roadster.)

 

[graham]

2) my cursory search did not find the actual final gear ratio for the Tesla Roadster.)

Is this what you were looking for?

Tesla Motors - technical specs

Transmission
Single speed fixed gear with electrically-actuated parking lock mechanism and mechanical lubrication pump
Overall Final Drive 8.28:1
Reverse Reverse direction of motor, limited to 15 mph
Final Drive Ratio 3.12:1

 

[ChargeIt!]

Yeah! Thanks! That's it. I was close (8.32 vs 8.28) !
( I had guesstimated the ratio so that the calculations would match up with the tire size. )

 

[power]

its not really a problem . the rotor mass is still yet a fraction of what a combustion engine inertia would be. a sequential gear box with a 80% rpm drop would be more than achievable. again, this is what the porscheGT3 cup car does all day long with near 500hp and at 7-90000rpm.
a one gear change would certanly be very easy, relatively speaking.

mk

Yeah a flywheel would definitely work against their goal of trying to get the eMotor to change RPMs as quickly as possible. It sounds like the existing mass of the rotor was too much as it is.

If they ever need variable ratios it would be good if they found a CVT that could work.

 

[power]

no he is refering to the gear box alowing the available power of the motor to be utilized by the tires at any vehicle speed in question. Forget about motor torque for a minute, its the torque at the rear wheels at any vehicle speed that is being talked about. to maximize this, max power is needed. (not max torque) the gear ratio tesla selected is like a 1st gear on most cars. the motor can extend near the same torque as a internal combustion engine to double the rpms with out the risk of bending valves . But, the power available is much lower later in the vehicle top speed, for which a gear box, even a second speed , could help with.
Gearing doesnt create power, it helps better utilize the power you have available. With the Tesla roadster, this happens near 8000rpm for max power, even though max motor torque falls off at 6000rpm.

mk

Are you referring to LF as it equates to a tire's properties of deflection and recovery during operation as it relates to peak-to-peak, first harmonic, second harmonic, and higher-order harmonics?



Or another form of LF?

 

[power]

I follow you here, but that is not really the question (which is getting more and more convoluted)

I think its agreed that the tesla 8.3:1 reduction is almost perfect for the motor and drive electronics. my point was to get another gear in there , with a 80% rpm drop to not only take the top speed up, but give much better acceleration in a key area of performance, that being in the 80 to 120mph range.

electronic gearing, as what i see as being suggested, is not just as simle as pulling out a few motor poles! there are switcing losses in the control circuitry, back emf, winding impedenace, etc. There never will be one electric motor that can provide constant power. If there was, it would waste a lot of technology and cost to do what an advanced gear ratio could do. (i.e a CVT -IVT ).

Part of the confustion still boils back to the ole power vs torque discussion.
power determines the torque at the wheels that gives the acceleration. maximize the power at ANY vehicle speed, and you maximize your acceleration.
Remember, Acceleration = Power/(mass x velocity). So, if you can get the Tesla Roadster at a higher power range (i.e. near 8000 motor rpm) then you will maximize its accelertion potential.

mk

Ok ... pardon me for "gearing in" ... but "inspiration" is not giving me the proper "inspired drive" to satisfaction ...

I would agree that direct drive is the most efficient and simplistic ... but you need a REDUCTION gear. Let's try some simple geometry and 'rithmetic with a motor directly driving the wheels:

Assume at 125 mph your motor turns 14,000rpm. Meaning your car travels 125 miles or 125*5,280 feet in one hour, or 125*5,280/60 feet per minute. Since your drive wheels are thus traveling 11,000 feet in one minute while the 14,000 revolutions happen, each revolution is 0.79 feet. This would match the circumference of your drive wheel, or 12*0.79 measured in inches or an equivalent 12*0.79/PI inches DIAMETER.

Sorry but I would prefer not to run my Tesla Roadster on 3.0 inch wheels which spin at 14k rpm.

I would prefer a final drive ratio of .... oh say ... hmmm ... what would be a nice number ... how about 8.32 ? That would allow me to drive a single-speed gear reduction transmission on wheels with 8.32*3.0 = 24.96 inches diameter. I think an 17" wheel with Yokohama 225/45R17 tires might just work out (45% * 225 mm * 2 converted to inches plus the wheel diameter).

Did I miss inspiration's point and am I way off subject ?

(Notes: 1) No insults intended; 2) my cursory search did not find the actual final gear ratio for the Tesla Roadster.)

 

[just-an-allusion]

Based on your posts I would estimate that my understanding of AC inductions motors is greater then your understanding of the part played by reduction gears.

I understand both the necessity and practical application of the reduction drive unit(s), i.e., inasmuch as a single stage reduction gearing setup requires the input shaft (motor end) to complete two(2) rotations to every one(1) of the output shaft (wheel end), and that a second stage reduction gearing setup would require the input shaft to complete four(4) rotations to every one(1) of the output shaft's, slowing it's overall revolutions as a byproduct, I fail to see the benefit since everyone appears to desire more performance/speed from their cars, but that's not what I'm getting at as I (as you can hopefully tell by now) feel that switching to a two-stage/two-gear setup would be defeatist at this point.

I would be very interested in seeing your motor specifications for your AC induction motor which will produce approximately 8 times the torque of the motor built by Tesla Motors. Please include weight, size, efficiency and the method of cooling used for the rotor.

Intellectual Property("IT") is IT only for as long as someone doesn't blab about it out in some public forum/I'm sure you would.

 

[just-an-allusion]

Ok ... pardon me for "gearing in" ... but "inspiration" is not giving me the proper "inspired drive" to satisfaction ...

I would agree that direct drive is the most efficient and simplistic ... but you need a REDUCTION gear. Let's try some simple geometry and 'rithmetic with a motor directly driving the wheels:

Assume at 125 mph your motor turns 14,000rpm. Meaning your car travels 125 miles or 125*5,280 feet in one hour, or 125*5,280/60 feet per minute. Since your drive wheels are thus traveling 11,000 feet in one minute while the 14,000 revolutions happen, each revolution is 0.79 feet. This would match the circumference of your drive wheel, or 12*0.79 measured in inches or an equivalent 12*0.79/PI inches DIAMETER.

Sorry but I would prefer not to run my Tesla Roadster on 3.0 inch wheels which spin at 14k rpm.

I would prefer a final drive ratio of .... oh say ... hmmm ... what would be a nice number ... how about 8.32 ? That would allow me to drive a single-speed gear reduction transmission on wheels with 8.32*3.0 = 24.96 inches diameter. I think an 17" wheel with Yokohama 225/45R17 tires might just work out (45% * 225 mm * 2 converted to inches plus the wheel diameter).

Did I miss inspiration's point and am I way off subject ?

Yeah, pretty much, other than the point of increasing the inherent inefficiency of the gear reduction drive unit that much further by adding yet another gear/stage.

(Notes: 1) No insults intended; 2) my cursory search did not find the actual final gear ratio for the Tesla Roadster.)

None taken. I'm use to people not understanding/misunderstanding the ideas/concepts that I attempt to convey...it comes with the territory.