Dealing with the Clunk

[Shinysideup]

OTOH, once customers realize what is going on, that hardened steel protrusions are going into hardened steel slots, maybe their concern will dwindle to where mine is: Zero. And they will just be left with the joy of riding this responsive machine and learn to love, as we all have with other bikes, its Brammoquirks. (tm) 

This is not to say that if the lash went magically away tomorrow, I wouldn't fully appreciate the silence. I just want readers to know that this issue is about the level of a pimple on the hair of gnat on a beautiful racehorse, compared to the unsurpassed grins that this machine creates for, say, this rider, on a daily basis.

[Jeff]

Brammoquirks. (tm)

Yeah.  While I definitely notice the lash, I just don't really care.  It's . . . odd, to be sure, but so is not having an exhaust pipe.

Having commuted daily on the bike for a few weeks now, I can confirm that it is manageable with some practice and acclimation.  If Brammo were to offer me a choice of any one thing to be changed about the bike, I'd say a locking seat release is more important to me than finagling a gentler engagement of the two insane forces I am violently jamming together.  (Haha and probably less engineering time as well)

[Richard230]

I occurred to me today that if you owned a typical Harley, with loud pipes making their "potato, potato" sound at idle, you probably wouldn't notice a transmission "clunk" all that much.  But with the Empulse being completely noiseless at "idle", the transmission noise becomes much more obvious. 

[flar]

My concern is less with transmission wear than chain wear.  I would think that a chain on an electric motorcycle with its smoother flow of power (no pulsing from the IC) would last much longer, but not necessarily if it is being subjected to a jolt on every launch.  Is a longitudinal jolt bad for chain lifetime?

[ttxgpfan]

I am pretty sure there is a standard cush drive on the Empulse, so I wouldn't think there would be any greater force applied to the chain.

[protomech]

I occurred to me today that if you owned a typical Harley, with loud pipes making their "potato, potato" sound at idle, you probably wouldn't notice a transmission "clunk" all that much.  But with the Empulse being completely noiseless at "idle", the transmission noise becomes much more obvious.

Reminds me of the Leaf review by autoblog green:

The headlights are more compelling, bulging out from the fenders more than some concepts displayed on the auto show circuit every year. Predictably, they serve a functional purpose. When Nissan was testing the Leaf, they noticed a fair amount of wind noise coming off the side mirrors. And with any EV, exterior noise is amplified due to the lack of racket emanating from under-hood. So the lights were redesigned to split the air leading towards the mirrors, eliminating buffeting and drawing a clear line through the atmosphere.

[BrammoBrian]

I am pretty sure there is a standard cush drive on the Empulse, so I wouldn't think there would be any greater force applied to the chain.

Correct. There's a cush drive in the rear wheel.  The chain is X-ring 520, so no need to worry about that.  We're actually contemplating dropping the Empulse TTX down to 420 chain to reduce weight and friction losses. We'll need to maintain and even replace the chain more often, but it should increase delivered power to the rear wheel by a couple of horsies...

[ttxgpfan]

I like it when Brian tells me I'm correct.  Makes me feel like I'm paying attention.

[implovator]

FWIW, my $0.02 on the driveline lash.

Firstly, I feel better calling it a thunk than a clunk. It's omnipresent, but it never feels harmful. Only time will tell how the transmission holds up, but I think the cush drive is performing admirably. And for the record, my BMW GS has the exact same thunk, but it feels a little less severe because it's one noisy, vibrating mess.

Secondly, as a experienced motorcyclist, I can easily explain it away as standard driveline lash that's made way more apparent because of the way the clutch is used on this bike.
  A) Off the line, you don't use the clutch and so it will thunk. Thanks a ton to someone (Richard230?) for mentioning the rollback at a light. I naturally do this anyway because I always come in hot at stops and the fork usually pushes me back when it extends a good deal.
  B) Up shifting, you usually release the clutch with no throttle input because even the slightest input will spin up the motor when no under load. Consequently, the engine braking kicks in before you can get back on the throttle. I found that with some practice, I was able to smooth out the upshifts by slipping the clutch a little and barely rolling on the throttle at the right time. At first I was afraid of blipping the throttle too much and burning up the clutch when I engaged it at a motor RPM that was too high. But then I realized, that this is perfectly safe because it's not like the clutch is stopping a metric ton of rotating mass at a high RPM. There is very low rotation mass in this motor.
  C) Slow speed maneuvering doesn't require the clutch, and so the thunk is worsened. Some mentioned (again Richard230?) dragging the brake while keeping the throttle open slightly. It does this trick, but it's not really my style. Instead I just try to roll on really slowly. It still thunks, but I'm really not too worried about it.

I guess my final thoughts are that this is a new experience for riders of both ICE bikes and direct-drive electric bikes. It just takes a little getting used to. Now I just hope I remember to pull in the clutch at a stop the next time a drive my GS. DOH!

[flar]

  B) Up shifting, you usually release the clutch with no throttle input because even the slightest input will spin up the motor when no under load. Consequently, the engine braking kicks in before you can get back on the throttle. I found that with some practice, I was able to smooth out the upshifts by slipping the clutch a little and barely rolling on the throttle at the right time. At first I was afraid of blipping the throttle too much and burning up the clutch when I engaged it at a motor RPM that was too high. But then I realized, that this is perfectly safe because it's not like the clutch is stopping a metric ton of rotating mass at a high RPM. There is very low rotation mass in this motor.

Or...just  don't use the clutch to up shift at all.
Apply upward pressure to the shift lever,  momentarily ease off the throttle,  and you'll be quickly and efficiently in the next gear...

[ttxgpfan]

Thinks makes me wonder why a quick shifter isn't stock on the bike.  Just bang the up shift and computer cuts the throttle.  It's be a nice aftermarket feature.

[FreepZ]

Or...just  don't use the clutch to up shift at all.
Apply upward pressure to the shift lever,  momentarily ease off the throttle,  and you'll be quickly and efficiently in the next gear...

I've been using that trick, and it works very well.

[flar]

  C) Slow speed maneuvering doesn't require the clutch, and so the thunk is worsened. Some mentioned (again Richard230?) dragging the brake while keeping the throttle open slightly. It does this trick, but it's not really my style. Instead I just try to roll on really slowly. It still thunks, but I'm really not too worried about it.

I find that a bit of zen is the best solution here.  Relax and think further ahead and you will transition from power to regen less often and less abruptly and it will almost seem like the clunk has disappeared.  And, once you get used to just how much the transmission has lagged, your own wrist will start to know just how exactly to transition the throttle to turn the CLUNK into a tap-and-go...

[Gavin]

Zen? I like it....just don't go into a meditative trance while driving

As for the slight up pressure, ease off throttle and slip into the next gear...sounds fun...can't wait to try and master it...

I take it you do use the clutch to down shift, or does the ease off the throttle, have regen slow you down and slight down pressure on foot pedal work without the clutch too?

So many tricks to try and instantly master....

Gavin

[flar]

I take it you do use the clutch to down shift, or does the ease off the throttle, have regen slow you down and

Technically, gearbox-wise, the opposite can be used for downshifting without the clutch.  It would involve pressing down on the shifter while blipping more energy with the throttle (reduce revs to upshift because that matches what the next gear up is expecting and increase revs to downshift because that is what the next gear down is expecting). I've done it in the past with my ICE bikes, but I haven't bothered with the Empulse because I only downshift while on full regen and there is no danger of over-revving in that state.  I did notice when I first started riding it that it would easily do a clutchless shift from 2nd -> 1st, but it didn't happen as readily for 3rd -> 2nd and I never bothered to work on it to master it since downshifting with the clutch is not prone to redlining the motor.  So instead I just settled on downshifting with clutch while on regen as my preferred habit...