wish of accessories and modification list

[BrammoBrian]

The Zero SR is geared so that it's just about traction-limited in acceleration, at least up to 60 mph. Zero claims 0-60 in 3.3 seconds (0.83G linear acceleration), top speed of 102 mph .. pretty damn fast.

Alternatively, you can tradeoff a bit of low-end acceleration with taller gearing. Say 0-60 in 4.0 seconds, 120+ top speed. This would be lighter and at least in the same ballpark acceleration-wise as the Empulse, tested at 4.8 seconds 0-60.

So with "only" 50 kW = 67 hp, you have far more top-end than you can use legally on the street, and still very quick acceleration.

And for race applications, virtually everyone has settled on a big motor and direct drive instead of a medium motor and a transmission. That's a pretty ringing endorsement of direct drive.

And I've got a bridge in London to sell you...

Let's see an independent test that verifies the 3.3s 0-60mph and top speed claim.  This is the danger of bench-racing from optimistic press releases - you can draw the wrong conclusions. The bike would require significantly more power to achieve this superbike level of acceleration.  This customer description of the acceleration doesn't seem to verify the claim either:

Protomech, It's hard to compare since it was a while since I tested the FX but I think the FX feels stronger from a stand still but the SR has a lot more power once the bike has past 30-40mph.

And yes - going high voltage changes the game - both in performance and in cost.  This is the reason that the Empulse RR is direct drive.  It works well, but we still lose out to the 1000cc superbikes at the end of a very long straight as we can't move the power curve to the next speed range like they can (i.e. with a gearbox). 

Remember that we raced the best Zero has to offer at Thunderhill at the end of the season.  Our bike was still heavier than the Zero and had the same transmission.  Guess who came out on top:

http://brammoforum.com/index.php?topic=2234.0

The gearbox provides the optimal performance from a low voltage system.

[protomech]

I'd love to see an independent test as well. Comparing specification claims against real-world tests pretty much requires weasel words like "ballpark".

It's worth noting though that Zero tested at 5.2 seconds 0-60 for the 2013 S ZF11.4 in the Cycle World test, which is coincidentally exactly what they're claiming for the 2014 S ZF11.4.

Zero claims 57% more current for SR, 56% more torque. 5.2s / 1.56 = 3.3s. Gearing is the same. So their 0-60 mph performance claim is reasonable, if the motor performs like they claim.

They reach their power peak at approximately 62 mph (4000 RPM) before torque starts to taper off (edit: 88 ft-lb at 4000 RPM, torque has already started to taper off). So they don't need more power to perform as indicated.

At Thunderhill Kenyon was basically riding a 2014 SR with a fairing, and Eric Bostrom was much faster (4-5s iirc) on the semi-faired TTX.

Is Bostrom that much of a better rider? Maybe .. Kenyon is by all accounts damn good.

I'd love to see the same rider test both bikes, as in the Cycle World review.

[BrammoBrian]

Zero claims 57% more current for SR, 56% more torque. 5.2s / 1.56 = 3.3s. Gearing is the same. So their 0-60 mph performance claim is reasonable, if the motor performs like they claim.

I think you've discovered how that 0-60 time was calculated by Zero.  Looking forward to ReFuel this year...

[protomech]

And yes - going high voltage changes the game - both in performance and in cost.  This is the reason that the Empulse RR is direct drive.  It works well, but we still lose out to the 1000cc superbikes at the end of a very long straight as we can't move the power curve to the next speed range like they can (i.e. with a gearbox).

There's a perfect demonstration of this in effect, in this quarter mile drag pitting a new Corvette against a Model S P85. Ignoring the Corvette driver's higher reaction times, the Vette had a lower ET and higher trap speed than the Model S. Also, it's very clear especially on the second heat that while initial acceleration is very similar between the two cars, the Tesla starts to fade at higher speeds relative to the Corvette.



Two ways to look at this.

1) The direct-drive Model S lost to the six-speed Corvette, and by a fair margin (~10 mph trap speed, 0.3 seconds ET). Yay gearboxes!

2) The Model S is damn near as fast as the Corvette, despite 10% lower peak power and 1300 pounds of extra weight. Plus, you know, the whole seven-seat vs two-seat thing. Yay direct-drive!

It's all about the application.

[BrammoBrian]

That is a pretty good example of where even high voltage direct drive can lose out (BTW - compare the top speed of the Tesla to the Corvette).  The question that makes this relevant to our conversation is... what would happen if you combined those performance curves?  i.e... the electric torque curve + the gearbox?  If GM had created an electric Corvette with a 3,4,5, or 6 speed transmission, would it have beaten the Tesla by a greater margin?  Or... another way to look at it is:  If Tesla had a 2 speed gearbox on the Model S, would it have been able to beat the Corvette?  You would need to factor in shift times, but I would assume they would be lightning fast given the current range of technology for "quick shifting".

A transmission does add cost and weight, but it also allows you to reduce cost and weight in your motor. Typically, the parts in a transmission are much less expensive than those in a modern permanent magnet motor (I do realize Tesla uses AC induction).  As far as adding complexity, I really don't think this is a strong argument against it as we have been building vehicle transmissions for as long as we've been building vehicles.  It's not as though introducing the transmission exceeds a level of integration complexity that the industry has been successful at many, many times before in the past. 

Also... both cars obviously have the rear wheel torque (RWT) to exceed the traction limit of the rear tires.  Therefore, the car that has a superior traction or launch control should accelerate harder.  I would assume, based on my experience, that it is easier to implement a very responsive launch and traction control system on an EV versus trying to do so on an internal combustion powered vehicle.

[BrammoBrian]

Our friends over at BRD have thrown their opinion on motors and gearing into the ring, so I thought I'd share it here:

http://faster-faster.com/community/?p=145

I agree with much of it (especially the focus on RWT versus motor torque) and thoroughly enjoy the nice graphics.  Unfortunately, I think the "magic" motor control software they are referring to is simply advanced field weakening, which most of our small industry is already using to gain this effect.

[flar]

Hey Brian, is there any anecdotal feedback from your racers as to how often they shift the TTXs in a race compared to the similar ICEs they may have raced?

[protomech]

Yes. Motor torque as a spec (without context of gearing) needs to die.

I thought field weakening was primarily intended to extend power beyond the sudden dropout at nominal max rpm. I wonder how they're getting more torque early - perhaps that's the internal shorter gearing and then field weakening during the (nominal) constant power regime.

[BrammoBrian]

Yes. Motor torque as a spec (without context of gearing) needs to die.

I thought field weakening was primarily intended to extend power beyond the sudden dropout at nominal max rpm. I wonder how they're getting more torque early - perhaps that's the internal shorter gearing and then field weakening during the (nominal) constant power regime.

Yes, I think your hypothesis is correct.  They are attempting to show the benefit of the lower gearing afforded by implementing field weakening and being able to spin their motor at high rpm under the field weakening current.  They don't mention that this is a particularly loss heavy way to achieve high rpm and will likely cause thermal issues, so should be used sparingly. 

[ttxgpfan]

Brammo needs to/would be the first motorcycle manufacturer (or anyone really) to offer a decent bicycle rack.  The Brammo guys are MTBers.  You guys need to figure out a way to get a rider and his bike (be it MTB or Road or whatever) and his riding gear to the ride, and have a convenient way to store his motorcycle gear while riding.  This is important.

[00049 (AKA SopFu)]

Brammo needs to/would be the first motorcycle manufacturer (or anyone really) to offer a decent bicycle rack.  The Brammo guys are MTBers.  You guys need to figure out a way to get a rider and his bike (be it MTB or Road or whatever) and his riding gear to the ride, and have a convenient way to store his motorcycle gear while riding.  This is important.

Don't leave out Cross bikes! Here's me with my other favorite two-wheeled vehicle:

[protomech]

Saddlebags for gear + http://2x2cycles.com/product/motorcycle-bicycle-rack/ ?

[00049 (AKA SopFu)]

Saddlebags for gear + http://2x2cycles.com/product/motorcycle-bicycle-rack/ ?

Contacting 2X2 now! 

[ttxgpfan]

Ohhhh.