Dealing with the Clunk

[Shinysideup]

My experience, at 1500 miles, is just exactly as Brian describes: The tranny is quit a bit smoother, especially after the 600 mile oil change. I've gotten more refined in my throttle control. I'm executing quick, smooth gear changes, up and down, more and more often.  I've come to terms with the quirks of this bike, clunks and all, and even come to like them as the Empulse's "character."

I heartily agree with keeping the software as aggressive as it is for takeoffs. I probably would have purchased the 2012 Zero when I test rode it many months ago were it not for the anemic performance off the line. I need to jump in front of traffic and the Zero oozed. Deal killer. So glad I waited for the Empulse where I can even jump in front of other bikers most of the time. And yes, I love the feeling of imagining the perplexed look on their faces: "What WAS that?" It's a real motorcycle, that's what! And Harley's sound SO 19th century now!

Sure, Normal mode and 3rd gear will reduce the clunk sensation, but where's the fun in that?

[ttxgpfan]

That sounds more reasonable. I have owned 18 motorcycles and never have I experienced a clunk on take off. Only when you actually shift especially into first can there be a clunking sound. This Empulse clunk is something new related to the electronics. If someone from Brammo would be so kind as to explain exactly what it is and assure us that it will not lead to problems down the road, that would be good enough for me. I could live with it.

http://esbk.co/2013/01/24/esbk-studios-episode-16-interview-with-brian-wismann-of-brammo/

[ttxgpfan]

My VFR (take drink) had some pretty serious engine braking which amplified the slack in parking lot maneuvers.  I was taught and taught to teach that dragging the rear brake at very slow speeds while countering with the throttle was just proper technique.  Not an issues on my little 500 when I was learning though. 

I take it the Empulse in normal mode is quite a bit quicker than your 500 Ninja?   Can't wait until you flick the sport mode button.  Probably like the day I discovered what happens if you rev a Honda V4 past 7000rpm.  Weeeeeee . . . ahh crap, brake brake, brake . . . whew. 

[FreepZ]

Hey Gavin, I recommend this link.

[Brammofan]

We need to come up with a more elegant-sounding word than "clunk."
I have some suggestions but will keep them in reserve.

[Gavin]

That third video is the bomb...it finally clicked in my head...

So a gas bike is always at 1000 rpms or higher, even at a stop
The electric bike is at 0 rpms at stop.

Add in the quiet of the electric bike at rest and the lack of vibration of the electric at rest...and the killer torque at take off....and suddenly the pronounced gearlash makes sense.

Cool. A) I can at least appear smart and explain it to people who test ride my Empulse (because EVERY ONE of my friends is gonna want to ride it)...and B) It will help me practice getting that perfect start of the line.

One other question...Brian, when doing pure city driving in traffic...and maybe wanting to shift less or not at all...do you recommend riding all them time in 2nd gear or 3rd gear....and is there a downside to that for the bike (other than the slower start, which, in traffic, isn't a big deal---we don't have lane splitting here in New Mexico so I'm not always ahead of the traffic...at least not at first )

Gavin

[BrammoBrian]

I would recommend calling it "gear lash" or "drivetrain lash".  I am opposed to calling it "slop" as it implies there's a problem or something just isn't tight when, in fact, this lash is intentionally designed in to allow the transmission to operate effectively.  The motorcycle transmission is a jewel of modern engineering, being compact, abuse tolerant (i.e. robust), AND relatively inexpensive.  While the backlash at low speed could be seen as a negative of the design, the positives are that the gearbox provides a very positive feel during shifting (i.e. nobody's mentioned that they have a hard time determining if they've engaged the next gear or not) and there is very little likliehood of finding a false neutral.  These are positives that our racers tend to focus on, and they typically do not even mention the gearlash as they've long since learned that smooth throttle and shifting inputs = fast lap times.

[Gavin]

PG

Prominent Gearlash or Pronounced Gearlash

LOViNG

Lack Of Vibration and Noise Gearlash

Gavin

[Richard230]

Interesting discussion.  I might add that recently some motorcycle companies have spent considerable time making small changes to their transmission shifting "dogs" in order to reduce the clearances in the gear-train in an effort to reduce slack and increase shifting precision. One way this is done is to bevel the dogs slightly to smooth engagement and make the engagement more secure so that the transmission will not pop out of gear after shifting (another problem on some models).  Designing and manufacturing motorcycle transmissions has been going on for well over 100 years now and the process is still being refined. Unfortunately, even small changes like this take time, effort and money. My guess is that Brammo or their transmission supplier will improve the gearbox and reduce the internal slack in the future.

[protomech]

the positives are that the gearbox provides a very positive feel during shifting (i.e. nobody's mentioned that they have a hard time determining if they've engaged the next gear or not) and there is very little likliehood of finding a false neutral.

Both of which [edit: lack of positive engagement and occasional false neutral] I experienced with the gearbox on my GS500 gas bike.

[Brammofan]

I would recommend calling it "gear lash" or "drivetrain lash".

So, if the assembly line in Hungary starts making the Empulse, would it be proper to call it "Hungarian Gear Lash?" (say it quickly, out loud).


I'll be here all week, folks.

[BrammoBrian]

Both of which I experienced with the gearbox on my GS500 gas bike.

Yes, with half the peak torque versus the Empulse R's...

[BrammoBrian]

Interesting discussion.  I might add that recently some motorcycle companies have spent considerable time making small changes to their transmission shifting "dogs" in order to reduce the clearances in the gear-train in an effort to reduce slack and increase shifting precision. One way this is done is to bevel the dogs slightly to smooth engagement and make the engagement more secure so that the transmission will not pop out of gear after shifting (another problem on some models).  Designing and manufacturing motorcycle transmissions has been going on for well over 100 years now and the process is still being refined. Unfortunately, even small changes like this take time, effort and money. My guess is that Brammo or their transmission supplier will improve the gearbox and reduce the internal slack in the future.

Richard - agreed on all counts. The unique challenge to our motorcycles is that the initial "hit" of torque on the dogs can be very high owing to the electric motor.  True statement that we will continue to develop and improve this system, but I also think it's pretty darn good right now.   

[ttxgpfan]

This is all pretty interesting to me because it seems that it is most certainly going to push transmission design.  One thing that has become very clear to me is that the drive line lash is quite noticeable on the Empulse for all the stated reasons.  It seems to be noticeable enough that a few of the newer [to motorcycling] riders find it intrusive, distracting, and two that I know of so far seriously felt something was going to break.  More experienced riders seem to merely acknowledge it as a characteristic that they get to master.  Clearly there is nothing wrong and people have reported, as has Brammo, that the transmission gets much smoother once broke in.  So, while everything is fine and designed properly, newer riders are finding themselves intimidated.  Clearly education can and does eliminate the intimidation but, as I face everyday at the bicycle shop, there is only so much you can do and only so much most people will pay attention to and internalize.  Only time will tell how many people perceive this as an issue.  If enough do then Brammo and SMRE will probably feel they have to come up with something.  I'm actually excited by that idea, and the prospect of seeing what they may come up with.

[Richard230]

I have been reading motorcycle magazine road tests for 50 years and rarely did I hear much about motorcycle transmissions making noise and having a lot of slack in the drive train during the early days when a big motorcycle was one that had 500cc.  Frankly, I think the testers were happy if the transmissions shifted without grinding or popping out of gear.

However, recently I have been hearing more comments about transmissions making "clanking" noises when shifting into first gear from neutral and sometimes when shifting between gears. I note that these noises seem to be associated with name-brand American-made V-twin engines of around 100 cubic inch displacement, with (no doubt) lots of heavy parts moving around that need their speed changed when shifting gears.  So I think Brian is right about the noise issue being related to a lot of torque trying to move parts that have a lot of inertia.

I don't think the noise will affect the operation or life of the drive system, but I do think that some sort of method to cut down on the noise, perhaps by rubber dampening the drive-line or modifying the off-idle throttle response, might be something to consider. 

Electric motorcycles are noted for being quiet and making a clunking noise when taking off is probably not something that most riders want to hear.  Plus, it gives some road test reviewers and potential customers something to complain about.  I am sure Brammo will find a way to mitigate the noise in time now that it has come to their attention as being a customer concern.