EV transmissions

[RickXB]

[That must have been the fire sale.  Regular pricing for the SR was $1,000 less than an Empulse R.

yep, without that price, i wouldn't be a EV rider

[Ted Dillard]

By the way if you're interested, and hopefully not too far off-topic, but Biff (a guy active on both elmoto and ES) did a great couple of posts on high vs low voltage, and kindly let me republish them here:

explanation: https://evmc2.wordpress.com/2015/02/10/voltage-high-or-low-explained/
the math: https://evmc2.wordpress.com/2015/02/12/voltage-high-or-low-the-maths/

Bottom line is it's more about the parts and pieces, and what makes a practical build than anything else, at least that's what I got from it.  For example, for my CBR600RR build, I want 100kW, and the Emrax 268 with the Rinehart controller wants to play at just shy of 400V.  The amps are less, so the cabling and connecting is less money, size and weight.  Of course, builder/user safety is a big concern too.

But it's all hinging on my motor choice.  (100kW @ 45lbs.)  The efficiency and power between the two all come out in the wash.

That build plan is here: https://evmc2.wordpress.com/2014/12/20/shopping-list-superbike-check/
...and no transmissh.   

[protomech]

Interesting that both Biff and Luke have spoken recently about HV (300+V) systems against LV (~100V) systems.

Biff mentions the difficulty of quick-charging at low voltage, but I think he misstates the importance of the network effect.

Who would start selling a LV electric car that essentially trickle charges on 200A QC stations? A 50 kWh LV car would charge at only 20 kW (2.5h) from a "100 kW" QC station.

Who would start selling or retrofitting QC stations to support these LV cars? The cablesets and connectors would need to be redesigned, all of the power electronics inside the charger would need to be replaced. More expensive than simply adapting an existing design for multi-standard CHAdeMO + J1772 combo. Even at "moderate" QC power levels like 100 kW, a 20 ft 1000A cableset and connector will weigh around 100 pounds .. and be worth about $150 in scrap value just for the copper. Hope the charging park is well-lit ..

[flar]

For my own part of the debate - I tried a 2012 Zero S and it wasn't enough to wow me, but it was enough for me to consider EV bikes.  The promise of the Empulse sounded more like what I was looking for and when I finally tried it, the performance matched what I wanted for a street bike/commuter with a wow factor.  I also tried the 2013 Zero S that had the newly designed motor before I pulled the trigger and my impression was that if it had been available a year earlier I wouldn't have bothered waiting, but it wasn't and since the Empulse offered a higher acceleration wow factor at the same time (actually a month or so earlier), I was happy to go with it.  Note that at the time I did note that their roll-on performance at speed felt very similar, but the 2013 S still did not have the urgency from a stop light that I like.  I've never ridden the SR so I'm a bit curious about that, but I've already made my EV bike purchase for the near future so I don't necessarily want to know.

WRT the transmission being a handicap in the process of cornering - if I was racing it then it might be more of a factor, but for my back-road mountain riding it's not an obstacle because I don't row the gears for every corner.  I pick a gear for a stretch of road and stay in it.  In that respect the Empulse is more like an on-the-fly tunable single gear bike in terms of how much effort I expend.  The number of gears works well for that since the different parts of Skyline may cause me to choose any of up to 3 different gears for a minute or two at a time and for a fairly small total range of speeds (i.e. some parts might average 50, some 60, but it's not like I'm doing 20 here and 90 there).  With only a couple of gears I would find maybe only 1 gear that worked for an entire run.  I suppose the transmission could have just the 3 or so gears I use on Skyline, but that would be purpose built for that one situation and we have 6 speed gear sets already available.  I also take into consideration that I already have a familiarity with how much of a difference a single gear shift makes when choosing gears from among 6.  I'm coming up to a really satisfying set of curves on Skyline on the Empulse and I already know just how many clicks to make so that the next 5 corners work very well.  I would have to spend a few months learning a whole new set of gear intervals if they had provided a 2 or 3 gear transmission.

I've seen a number of reviews of the Empulse where the transmission was docked for a lot of reasons that you can train out of yourself in just a couple of rides if you talk to the right people.  The most obvious is "don't pull in the clutch at a stop light" and I've seen comments in reviews that made me wonder if the riders had at least been reminded of that given the comments they were making.  There were also comments about the clunk from a stop which is eliminated using the 2 inch rollback technique that I first remember Shinysideup describing here.  Matching revs and the motor whining is also an indication that they didn't try power shifting which works amazingly well on this bike.  With a proper 1 minute discussion before a test ride, the impression of the transmission on this bike can dramatically improve.  This, of course, goes against the standard marketing comment that the transmission is there for familiarity (well, to a point, and it is possible to get where you are going without being aware of any differences to be sure - but for ... sake, go over a few points for maximum enjoyment, no?).

[flar]

One question for the people who understand electric motors and controllers here.  I know that the Tesla can pretty much be driven with a single pedal, using generous regen to slow the car down.  The same can be done with the Empulse, but you definitely need to shift down to 1st for some intersections to get it nearly stopped as some of the higher gears don't quite provide the same "I'll get you nearly stopped" response.  The regen can also be modified by choosing Sport or Normal mode so it is somewhat under the control of the electronics as well (and can't the Zeros tune this with their phone app?).

My question would be - would high voltage systems be more capable of providing more regen braking (and tunable/selectable engine braking like you get with your pedal position on a Tesla) even with a single tall gear?

(And there is still that issue that someone claimed that Vectrix had patented the concept of selectable regen through reverse handlebar twists - is that true, and is that still true now that they've been liquidated?)

[BrammoBrian]

I think the question we have to ponder before you answer this question is... "What is ENOUGH performance?".

I don't think this argument holds water either, now that we can see numbers from bikes like the Energica, the Mission, performance like the racing of the '14 Zero SR, your bikes, and a field of gas bikes.  The only argument that makes any sense to me at all is that of the choice being for the "rider experience".   Unless I missed something, when you compare performance between similar bikes with, and without a transmission it's a wash at best. 

Here's some reference: https://evmc2.wordpress.com/2013/04/27/transmission-questions-finally-answered-zero-brammo-comparison/

Here's another post re the Laguna Seca results ca. 2013: https://evmc2.wordpress.com/2013/07/21/transmission-debate-qualifying-results-at-laguna-seca-fim-err/

As with anything else in engineering and Physics, you can get to the same place any number of ways.  I have no problem with Brammo using a transmission, though I think the general consensus is that 6 speeds is more a function of what was available than what was best.  And I have no issue with riders wanting a transmission because they simply like it better. 

I don't, however, feel like anyone can point to one design or another and say it will give you better performance, and I'd truly welcome an education on it if I'm wrong.  As long as it doesn't include the phrase "torque multiplying" 

You might have missed the re-match between the TTX and Kenyon's Zero S race bike...

In the same 2013 season, Kenyon came out to race in the final AFM race of the season with the same Zero S that he placed 2nd on at Laguna Seca.  This time, we put Eric Bostrom on the bike.  The result was that Eric finished a six lap race ahead of Kenyon by about 20 seconds.   

https://www.brammo.com/blogs/?p=1916



Then... in 2014, we gave the TTX to Eric for the ReFuel event at Laguna Seca, where he bested the Zero qualifying lap record by over 2 seconds on his single, flying lap.  He was also faster than Jeremiah Johnson's modified Zero, the fastest of the rest, by over 6 seconds on the day.   

https://www.brammo.com/blogs/?p=1946

Do I think that this settles things - No, of course not.  I just want to highlight the difference a rider makes in maximizing the available performance from any motorcycle.  Eric, a professional rider, was able to use the transmission to full advantage. 

Here are the primary benefits over direct-drive (which I am also not against as a solution):

1. You can use a physically smaller motor as you require less torque from your motor.  This may equate to more efficient packaging of your battery, if done properly.  It theoretically makes the motor magnetics less expensive as well.
2. Clutch can be used to disengage the driveline in an emergency.
3. Final drive gearing is less critical with a multi-speed transmission as the rider can select different ratios.
4. Maximize acceleration and top speed. Less compromise.
5. Allows for variable regen through the gears as Flar has mentioned.
6. Since you cant' stall and the motor has torque from 0 rpm, you can choose not to shift. IF you're feeling lazy, put her in third and ride it like a scooter.

Here are the downsides:

1. Adds some weight (although your motor is smaller and lighter) and complexity.
2. Increases the driveline harshness with more moving parts and resulting mechanical tolerance (slop).
3. Requires more rider training and skill to master.
4. Adds cost to an already expensive product. 
5. Having to explain the difference between motor torque and rear wheel torque by using the term "torque multiplication" over and over... 

[skuzzle]

Any thoughts on why a wet clutch is used for the Empulse?  With the electric motor there is no engine by-products to deal with.  It seems like a dry clutch would allow the best gear oil to be used.  The oil change interval would probably go from 3000 miles to probably over 20000.

[Chocula]

That is the best looking Zero I have seen yet.  I also love the look of the "half" fairing on the Brammo and would love to see that be made available in a street legal configuration for my Brammo.

This has been a great discussion and while I agree with Ted that with a big enough motor and controller, a transmission is not needed.  Unfortunately, until a bike is available that I can afford which is traction limited up to about 80 mph with a top end of at least 150, a transmission will still offer some advantages.

It took a few weeks of riding to get used to riding smoothly on the Brammo, but like everything else, you get better with more experience.  The drive train lash is just as bad on my ICE bike, its just that everything else is rattling so much you don't notice,  the clutch on my ICE bike is way smoother, and its engine does not have nearly the instant torque like the Brammo.

I can also see value of a transmission in racing once electrics become popular enough to separate them into classes based on motor and controller size.

[Ted Dillard]

Thanks Brian.  On the riders, I've had long conversations with Rob Barber who rode the Ohio State IOM bike to third last year, about transmissions, riding style, riding strategy, use of regen, etc and how it's different than gas bikes with transmissions - admittedly not electric bikes with transmissions - and he likes it.    I've talked to a few other pro riders as well over the years.  I think that, bottom line, they all are still learning about the EV drivetrain and how to ride it - tranny or no. Think what Kenny Roberts did for riding style in what, the early '70s? 

Barber, interestingly, runs the bike with little or no regen, and prefers controlling his front-to-back braking himself.  He also feels that the rider control is more "pure" and allows better entrance and exit to curves once the rider understands the timing.   etc etc. 

For me, personally, the lack of transmission on an insanely powerful bike is precisely what I love about electric motorcycles.  Beginning and end of story.  See this: http://insideevs.com/electric-motorcycle-primer-insideevs-style-part-1-ride/

And not to be a bitch, but I don't consider either the Empulse or the Zero SR to be "insanely powerful".   

"Do I think that this settles things - No, of course not."  If there was information, performance and data that supported a transmission as clearly better for performance, that would be one thing.  The fact that the two bikes are closely matched serves to make my point.  But to toss the EV ride experience "baby" with the transmission ideology bathwater, it's not my choice. 

And as I've said before, it would be a shame if the folks who like shifting didn't have that option.

And, I do have to crack up at your mention of cost.  Somewhere else - I think it a comment thread on IEV maybe, I got beat up because they claimed Brammo claims one of the reasons they use a tranny is the "cost factor".  Something I hadn't heard before.     I think they even attributed the claim to you lol.