# Tesla testing



## 2cycle (Jul 2, 2009)

After reading the article some more it does mention about going to their web site to see the dyno tests, so it sounds like they used a chassis dyno to measure rear wheel hp. I think it was something like 1200 lb/ft to the rear wheels from start to around 40 mph then it starts a linear drop to the peak speed.


----------



## Bowser330 (Jun 15, 2008)

2cycle said:


> I picked up a car magazine this weekend because it had done a multi day test session with the Tesla. The guy really liked it for stoplight to stoplight fun. He mentions the lack of top speed but also reminds us that top speed is rarely used and was worth the trade off of the off the line punch.
> They showed some interesting numbers that were either chassis dyno figures or onboard dyno figures. It pretty much shows what I thought all along, it has great off the line torque to the rear wheels but as soon as it gets past 40 mph it's all gone and heading down hill quick. They showed a comparison to the V-6 Camaro and as soon as the Camaro shifts to second gear the torque to the wheels as already more than the Tesla is at that point during a sprint. When you campare the weight specs you will see that the Tesla is more than 1000 lbs lighter, that's where the performance comes from. After reading that write-up I would have to say a 2 or 3 speed tranny would surely make the torque to the rear wheels show better *but the weight would slow it down off the line* to gain the top speed and it wouldn't be worth it.


The weight of what? The transmission? I feel the original two speed option would truly make this a super car terror... so yes it would add another 100 lbs of weight, but the car is already overall pretty damn light...and that second gear would really help that flat torque curve come to life at higher speeds...

It would be cool if they were to offer the 2 speed tranny as an add-on option...

I have noticed that the Bmw. Porsche, and other tuners are using the seconds it takes for 60-130mph as a performance comparative standard...

The figures i ran of the Tesla's multiplied torque showed it being pretty underpowered from 60-130... in comparison to a Porsche 911 turbo for example...


----------



## ClintK (Apr 27, 2008)

Bowser330 said:


> It would be cool if they were to offer the 2 speed tranny as an add-on option...


Wasn't one of the reasons they dropped the 2 speed was because of poor reliability? If I remember right, it was hard for them to find a transmission that could shift at 14,000 RPMs.

Side note... sure the muscle car magazines will complain it can't do 140 mph, but I'm sure a fraction of the owners will even get near 100 mph - and their waiting list for the car shows their design tradeoffs are acceptable.


----------



## Bowser330 (Jun 15, 2008)

ClintK said:


> Wasn't one of the reasons they dropped the 2 speed was because of poor reliability? If I remember right, it was hard for them to find a transmission that could shift at 14,000 RPMs.
> 
> Side note... sure the muscle car magazines will complain it can't do 140 mph, but I'm sure a fraction of the owners will even get near 100 mph - and their waiting list for the car shows their design tradeoffs are acceptable.


If they wanted to find a transmission that could handle it, they could have..because there are transmissions that could handle 14,000rpm...

I think they realized, like you and others have said before, that most people would care more for performance around the 0-60 range rather than 60-whatever...so they scrapped the idea of the trans more because of that rather than sourcing a transmission....


----------



## WarpedOne (Jun 26, 2009)

> If they wanted to find a transmission that could handle it, they could have..because there are transmissions that could handle 14,000rpm...


Such a transmission is another thing everyone says exists but noone can show it to me. Nor Tesla Motors. Magna couldn't make one, XTrac couldn't make one. They've both tried and failed.

Now, whom am I supposed to believe? A random forum guy or specialist who tried and failed?


----------



## Bowser330 (Jun 15, 2008)

WarpedOne said:


> Such a transmission is another thing everyone says exists but noone can show it to me. Nor Tesla Motors. Magna couldn't make one, XTrac couldn't make one. They've both tried and failed.
> 
> Now, whom am I supposed to believe? A random forum guy or specialist who tried and failed?


"Random forum guy?"

Nice to meet you too Mr. 18 posts

Believe whomever you want too warped one.


----------



## WarpedOne (Jun 26, 2009)

Post count says nothing about the subject on hand. 
Show me the transmission that you say exists. I am fed up with armchair engineers that know everything way better than those who do it for their living.

I would expect from people on this forum to know something about Tesla Motors, their problems and achievements yet I find the same **** here as everywhere else.


----------



## Bowser330 (Jun 15, 2008)

WarpedOne said:


> Post count says nothing about the subject on hand.
> Show me the transmission that you say exists. I am fed up with armchair engineers that know everything way better than those who do it for their living.
> 
> I would expect from people on this forum to know something about Tesla Motors, their problems and achievements yet I find the same **** here as everywhere else.


good luck getting a healthy discussion going with your piss poor attitude.


----------



## WarpedOne (Jun 26, 2009)

Form over substance eh? Lets all sing khumbaya and ignore the facts?

You came forward with:


> If they wanted to find a transmission that could handle it, they could have..because there are transmissions that could handle 14,000rpm...


Facts are that Tesla Motors spent over 10 million $, tried 2 different transmission suppliers and suffered over a year of delays trying to produce a reliable 2 speed transmission that could handle those 14k rpm, be lightweight and efficient enough. And reliable. And quick.

In my book that counts for wanting it badly. They wanted it so badly that they almost failed as a company. There is a saying around here that goes something like "If there isn't any, even army can't take it".

Now, If you know of such a transmission by all means point it out. I (and many others) want to know of it also.


----------



## CroDriver (Jan 8, 2009)

WarpedOne said:


> Form over substance eh? Lets all sing khumbaya and ignore the facts?
> 
> You came forward with:
> 
> ...


As far as I know the 2 speed they have used was a standard Honda transmission with only two gears left inside. If a Honda transmission could take it I don't see a reason why they couldn't make a custom transmission for their needs.

Modern superbikes can spin to 17.000 RPM



















I know that they haven't much torque but their transmissions are very light. I'm pretty sure that it IS possible to make a transmission for a high speed - high torque AC motor.


----------



## WarpedOne (Jun 26, 2009)

> As far as I know the 2 speed they have used was a standard Honda transmission with only two gears left inside.


?!?!? 
Where did you get that info?


----------



## CroDriver (Jan 8, 2009)

WarpedOne said:


> ?!?!?
> Where did you get that info?


I really can't remember. I think that I "know" that for years but I don't know where I got that info from. 

Just did some googling but didn't find any usable info


----------



## WarpedOne (Jun 26, 2009)

I don't know what they've used for their first prototype. Motorcycle transmission makes sense for such a thing as it is only a proof of concept. For the first prototype the main issue is availabilty.

Direct from Darryl Siry:


> Update: Tesla VP Darryl Siry contacted us to clarify the issue with the original X-Trac gearbox. Apparently the problem was not one of actual durability of the transmission itself. Tesla evidently spec'ed out a two speed unit with no clutches. The design intent was to do clutch-less shifting and manage the torque output of the motor during the shifts. Unfortunately the rotational inertia of the motor made this plan unworkable as the torque output couldn't be changed fast enough. According to Siry there were never actually any mechanical failures of the X-Trac transmission, it was simply a matter of Tesla not being able to get their control strategy to work adequately with the hardware. Subsequently Tesla contracted Magna to develop a dual clutch two speed gearbox. Unfortunately, this is the design that had durability issues leading to Tesla's ultimate decision to revise the motor for more power and go with a single speed unit for production. The vehicles running with the interim single speed gearbox are actually using the original X-Trac box with the lower gear locked out (for prototypes) or removed entirely (early production cars). - Sam


That "couldn't be changed fast enough" was about 4 seconds IIRC.


----------



## Bowser330 (Jun 15, 2008)

The members on the Tesla forums actually explained the issue with the transmission more clearly so I understand that it wasn't just about a 14,000 rpm transmission....The problem looks to be more specifically the gearing drop from ~12,000rpm down to 7,000rpm...

Warpedone touched on that with the D. Siry quote:


> _...Unfortunately the rotational inertia of the motor made this plan unworkable as the torque output couldn't be changed fast enough..._


As you would expect there really hasn't been any large need for a single gear drop like that for this application or any other that I know of...so there hasn't really been much r&d on it... Its not that it cannot be done..There are way more advanced technologies out there than a 2 speed EV specific gearbox...patience warped one.

There were also some good ideas on the Tesla forum...(paraphrasing)
(1) Why shift at 120000rpm? It would make more sense for a 9000rpm shift (81mph) down to 7000rpm (9-7..is a down shift that is handled by Porsche GT3 cup cars)

(2) Why not just have a sequential shifting transmission that can blip the gears down in milliseconds down 2 steps instead of one 12-9-7 or something like that. 

Both valid ideas.


----------



## CroDriver (Jan 8, 2009)

Bowser330 said:


> (2) Why not just have a sequential shifting transmission that can blip the gears down in milliseconds down 2 steps instead of one 12-9-7 or something like that.


Wasn't the two speed transmission in the Tesla a sequential? A sequential gearbox is the only reasonable solution IMO. A automatic transmission with a torque converter is not very efficient.

And I think that the problem was not a slow transmission (or gear change mechanism). The motor (or motor controlling) was the problem. 



> The design intent was to do clutch-less shifting and manage the torque output of the motor during the shifts.* Unfortunately the rotational inertia of the motor made this plan unworkable* as the torque output couldn't be changed fast enough. According to Siry there were never actually any mechanical failures of the X-Trac transmission, it was simply a matter of Tesla not being able to get their control strategy to work adequately with the hardware.


So Tesla wanted to make a clutch-less two speed gearbox. In this case the motor has to prepare itself for the next gear. When shifting from the first to second gear it must lower the RPM to a exact figure to make a clutch-less shift possible. 

Since Tesla uses a AC motor I think that this shouldn't be a major problem for them...


----------



## Bowser330 (Jun 15, 2008)

CroDriver said:


> Wasn't the two speed transmission in the Tesla a sequential? A sequential gearbox is the only reasonable solution IMO. A automatic transmission with a torque converter is not very efficient.


I think the idea was...12-9-7 as quickly as possible..that is three speeds with two shifts:
(1) 12,000rpm to 9000rpm
(2) 9000rpm to 7000rpm

I agree with you CroDriver, I am also a bit confused by this quote:


> _According to Siry there were never actually any mechanical failures of the X-Trac transmission,* it was simply a matter of Tesla not being able to get their control strategy to work adequately with the hardware.*_


----------



## WarpedOne (Jun 26, 2009)

> Since Tesla uses a AC motor I think that this shouldn't be a major problem for them...


It is not only you guys that are confused by this. I get many comments along the line that it should be easy/doable to slow down the motor. Even from 14.000 to 7.000 rpm. Even when the rotor weighs about 50 pounds. Even in only half a second.

The problem lies in their controller. Is it possible that while the controller tried to stop the motor and absorb all that energy in half a second (about 50 kW of power) some huge current spikes occurred that some part of their electronics just couldn't handle? Maybe not under all possible circumstances? 

Remember the controller is air-cooled and can overheat. What if the controller already overheated and it had to absorb that surge of power while down-shifting? Ten times in a row? You cannot write into owners manual something like "When the controller overheats you should not down-shift". Car costs 100.000$ It has to work under all "normal" circumstances. Repeatedly.


----------



## major (Apr 4, 2008)

WarpedOne said:


> Even from 14.000 to 7.000 rpm. Even when the rotor weighs about 50 pounds. Even in only half a second.


Hi Warped,

Why would they be trying to go from 14kRPM to 7k when the peak power is back at 7 or 8k?



> The problem lies in their controller. Is it possible that while the controller tried to stop the motor and absorb all that energy in half a second (about 50 kW of power) some huge current spikes occurred that some part of their electronics just couldn't handle?


And why would they try to "absorb" that energy in the controller? Simply dump it back into the battery. The controller surely is capable of converting 50kW and the battery capable of 50kW short term charge. 

I've seen heavier rotors decelerate faster than this with the dyno connected to the shaft with similar or smaller size inverters (controllers). It is not an insurmountable problem with the physics. But may present some unique control challenges. 

I don't know the specifics about the Tesla transmission or the development they did. But if they couldn't validate the transmission, they did the right thing releasing it direct drive. Seems like a well performing vehicle to me 

Regards,

major


----------



## Batterypoweredtoad (Feb 5, 2008)

50lbs isnt that much. I doubt that is much different than most manual transmission ICE vehicles when you account for flywheel, clutch, crank, pistons, etc... Add in the fact that you can use some electronic control to slow the motor and I'm surprised they couldn't make it work. On the flip side they are a small operation, so I bet they pay big bucks for [email protected] instead of having people beg them to use their product.


----------



## 2cycle (Jul 2, 2009)

There should be no reason mechanically that a simple 2 speed couldn't be made. I'm not quite sure what the shift delay problem is all about. A cassette style transmission doesn't need much more than a handful of milliseconds to unload enough torque to smoothly lock the next gear. 
I don't know who Tesla had build the prototypes but if it wasn't a cassette style they were likely doomed from the beginning. You don't have to be an engineer to see that coming.
Another thing about the Tesla power curve, if your shifting past 9500 rpm your not helping yourself out. It looks like the power peaks near 9000 rpm and any transmission mechanically should handle that no problem.
My bet is it was a money thing. They already went so far over initial predicted cost that they made the call.


----------



## Duncan (Dec 8, 2008)

The initial post said 
"As soon as it had reached 40mph its all over"
If I am reading the specs right peak power is about 80 mph and the bugger has still got 
150 Kw at its governed top speed (125 mph)
The torque curve shows constant torque from zero to 60 mph
I suppose you could increase the rear wheel torque by gearing it down and then changing up a gear but you would want to run to 12,000rpm then change down to 7000rpm
Now this is all with the stronger motor but it does beg the question of why you would need a gearbox at all


----------



## Duncan (Dec 8, 2008)

2cycle
Why would you change at 9500 rpm ?
at that rpm you are only about 3% below peak power, 
you have a wonderful flat power band 
from 6000 rpm to 11000 rpm you are within 7% of max power
The initial flat torque curve takes you through the part when you cannot use all of the power then you still have 150 kw at a highly illegal max speed


----------



## Duncan (Dec 8, 2008)

Sorry to keep messing about

But another look at the Tesla power curve showed that gearing the thing lower may (tyres permitting) increase its acceleration up to 40 or 50 mph but then it is power limited and that flat power curve means that adding gears could only help a tiny little bit and then above 110 mph


----------



## JRP3 (Mar 7, 2008)

2cycle said:


> My bet is it was a money thing. They already went so far over initial predicted cost that they made the call.


Yes, the cost, the need to get a product to market, and the realization that by increasing the power they really didn't need a two speed at all.


----------



## 2cycle (Jul 2, 2009)

Duncan said:


> The initial post said
> "As soon as it had reached 40mph its all over"
> If I am reading the specs right peak power is about 80 mph and the bugger has still got
> 150 Kw at its governed top speed (125 mph)
> ...


 

Maybe the term "it's all over" wasn't really a good term. I've been looking for the link online to see the dyno tests and the comparison to the Chevy but no luck so far. Anyway, their graph overlay of the Tesla compared to a V-6 Chevy Camaro showed the Tesla having great torque to the rear wheels up to 40 mph then a linear decent. Once the Chevy shifts to second gear the torque to the rear wheels was already surpasing the Tesla and remained higher than the Tesla all the way to peak speed which is likely pretty close between the cars seeing as the Camaro was only a V-6 model.
When we set up a trans ratio you need to know the powerband as compared to the desirable rpm drop upon shift. The tesla can overrev quite a bit as noted on their simple graph but the real numbers would need to be looked at to find the true sweet spot. Look at it this way, if the peak power is 250 hp, and 1500 rpm past peak is 230, and 1500 rpm before peak is 230, then you will accelerate much faster if you shift down 3000 rpm and make another run through the power peak area rather than let it keep running a downhill slope.


----------



## Buckster (Nov 4, 2009)

Surely it would react better to a torque converter type arrangement, a simple two cone system would suffice and could be built lightly while retaining reliability, it would remain a one speed transmission but by shifting up the drum at a preset point would reduce rpm. There are multiple ways to manipulate a torque converter.


----------



## 2cycle (Jul 2, 2009)

was reading tid bits from the article again and came across the cost comparison "in California" to a gas burner. They were charged crazy amounts to charge the car at night. The few days they spent driving (500 miles I think) they spent $45 on electricity. They equate that to driving a car that gets 33 mpg, not that tough to find when you can settle for a 2 seater, my friends new Corvette gets 30 mpg.

How does Cali figure they are helping anything by charging 3 times what the rest of us pay for electricity. Why is being green mostly for the rich minority?


----------



## gor (Nov 25, 2009)

2cycle said:


> There should be no reason mechanically that a simple 2 speed couldn't be made. I'm not quite sure what the shift delay problem is all about. A cassette style transmission doesn't need much more than a handful of milliseconds to unload enough torque to smoothly lock the next gear.
> I don't know who Tesla had build the prototypes but if it wasn't a cassette style they were likely doomed from the beginning. You don't have to be an engineer to see that coming.
> Another thing about the Tesla power curve, if your shifting past 9500 rpm your not helping yourself out. It looks like the power peaks near 9000 rpm and any transmission mechanically should handle that no problem.
> My bet is it was a money thing. They already went so far over initial predicted cost that they made the call.


absolutelly no reason - torque - same and in a same range as 6 syl car they shown and go lower... 
-doesn't has to have 4 gears... or change it often...
- what's wrong with the regular clutch? wouldn't have to worry about motor deceleration - clutch and wheels would take care of it : )
p.s. - pict: tq&power curves from the net;

_pps. top speed is drag, effort & hp limited - whatewer it is; final rpm at wheels: 24’’, 1000rpm=71.3mph; 2000 =142.6_


----------



## gor (Nov 25, 2009)

2cycle said:


> I picked up a car magazine this weekend because it had done a multi day test session with the Tesla. The guy really liked it for stoplight to stoplight fun. He mentions the lack of top speed but also reminds us that top speed is rarely used and was worth the trade off of the off the line punch.
> They showed some interesting numbers that were either chassis dyno figures or onboard dyno figures. It pretty much shows what I thought all along, it has great off the line torque to the rear wheels but as soon as it gets past 40 mph it's all gone and heading down hill quick. They showed a comparison to the V-6 Camaro and as soon as the Camaro shifts to second gear the torque to the wheels as already more than the Tesla is at that point during a sprint. When you campare the weight specs you will see that the Tesla is more than 1000 lbs lighter, that's where the performance comes from. After reading that write-up I would have to say a 2 or 3 speed tranny would surely make the torque to the rear wheels show better but the weight would slow it down off the line to gain the top speed and it wouldn't be worth it.


according to data http://www.teslamotors.com/performance/acceleration_and_torque.php

Sport: 
288 HP (215kW) @ 4,400-6,000 rpm
395 lb-ft (400 Nm) @ 0-5,100 rpm
Overall Final Drive
8.28:1


Size - rear
225/45 R17


125 mpg: wheel rpm= 1683.82

------------
torque (acceleration) rises until 45mph and than going down, HP after 53mph down

max torque at: 5100 24.97*0.0029735/8.28=45.73mph
max hp at: ... =53.803mph


----------



## major (Apr 4, 2008)

gor said:


> 395 lb-ft (400 Nm) @ 0-5,100 rpm


Hey gor,

Thanks for jumping in. But these numbers are off.

What is your point? You put up a bunch of specs and such, but don't say anything as to a point. 

You like the Tesla or not? You think it would be better with a tranny or not? You got a tranny for it or not?

Inquiring minds want to know. 

major


----------



## gor (Nov 25, 2009)

major said:


> Hey gor,
> 
> Thanks for jumping in. But these numbers are off.
> 
> ...


do i like it? - don't know 
that's why raw numbers, anyone can draw own conclusions, to like it or not

i don't like if something cut on the middle - but - it is does what it suppose to - it does 0to60 3.7 and goes 125mph; 
so they play it wise - first production model goes simple, no excess - good for most applications; other models can be different with and/or without trannys; plus there is something for aftermarket to mess with and push farther : )))


----------

