6 speed electric bike?

Interesting. I wonder how badly it even needs a clutch?

The transmission is a great idea, but there is no need for a clutch, and really its only benefit would be pulling it in diving into a corner (for the people who don't like drag brake) but the manufactur should design it with adjustable drag brake anyways, and when the electric motor is being spun it recharges the battery.

So honestly, they should dump the clutch and save some weight.

The transmission is a great idea, but there is no need for a clutch, and really its only benefit would be pulling it in diving into a corner (for the people who don't like drag brake) but the manufactur should design it with adjustable drag brake anyways, and when the electric motor is being spun it recharges the battery.

So honestly, they should dump the clutch and save some weight.

I'm personally a big believer that clutches help transmissions.

Some people swear up and down you can shift without hte clutch, some people say down shifting will hurt it but up shifting is fine, others say the opposite. Some people swear you can WOT shift with no clutch..

I know you physically can shift without the clutch, but IMHO, unless you shift easy and perfect, you are just shaving life off your transmission. Power shifting with no clutch will never be good, I've replaced too many transmissions with rounded off gears. Not saying clutchless shifting caused it, but it certainly doesn't help anything except maybe going fast!

But to each his own. Not saying anyone is wrong, just saying I use my clutch personally. No trophy at the end of my trail riding, or street riding :thumbsup:

What I say to anyone who says you can power shift without a clutch, would you power shift a 1980's bike that you didn't want to harm the tranny in?

Just my 2 cents, I know there will be like 50% of riders who will disagree with me. Everyone has their own opinions. If I want a bike to last and don't plan on yanking it apart, I'll stick to shifting with the clutch :confused:

Of course a race bike you are doing bottom ends in every 100 hours, screw it, not like it'll cost a lot to slap some gears in it every few hundred hours. But when you start talking about putting 500+, or even thousands of hours on a transmission, that is when things become a little more iffy on clutch use :worthy::thumbsup::busted:

I just thought it was cool so I uploaded the page, as I knew a lot of people were complaining about the electric bikes being one speed.

I personally don't care for electric bikes, just thought it was another step forward for them :smirk::thumbsup::moon:

The last bike in the photos has a gas tank:excuseme:

... unless you shift easy and perfect, you are just shaving life off your transmission.

"Easy" can be as harmful as anything else. The best way is to relieve the load on the trans by one means or other, and then shift quickly and cleanly from one gear to the next. The quickly part is the key, since what rounds off the locking lugs is having the lugs collide with each other when they are less than fully meshed. As long as the lugs are deeply overlapped when the load hits, they can stand a huge amount of abuse.

I will give you that dragging the lugs out of mesh under full power is NOT good for them, though, and it may actually be worse than the impact of hitting the next gear.

"Easy" can be as harmful as anything else. The best way is to relieve the load on the trans by one means or other, and then shift quickly and cleanly from one gear to the next. The quickly part is the key, since what rounds off the locking lugs is having the lugs collide with each other when they are less than fully meshed. As long as the lugs are deeply overlapped when the load hits, they can stand a huge amount of abuse.

I will give you that dragging the lugs out of mesh under full power is NOT good for them, though, and it may actually be worse than the impact of hitting the next gear.

That's what I meant by easy, shifting and matching the revs, letting the bike slide into gear

I just fully believe that slamming the next gear, either WOT or letting off the throttle, is bad, and not clutching makes it way worse.

Of course, rolling off the throttle, and gently clicking up a gear when the revs match, or even down shifting and bliping the throttle, I think is the best. Of course, this slows people down.

So that's why I think it's best to clutch, since no one in a race condition is going to wait for the bike to shift easily on its own clutchless. I do it sometimes with no clutch, but thats when I'm riding extremely casually, say to the gas station, or on the sport bike just cruising in traffic, or on a trail when I'm resting and have my hand off the bar. Other then that, I clutch every shift :thumbsup:

edit: I guess of course, and electric bike, probably as soon as you chop the throttle, its most likely unloaded and safe to shift clutchless. Hell for an electric bike, I'd say about the best setup would be a push button shifter, with a 'motor cut', to cut power to the electric motor for a split second.

Of course this is just my speculation

I would think the time for a human to dis-engage the clutch, shift, re-engage it would be a lot slower than a microswitch on the shifter to momentarialy cut power to the motor. A heck of a low cheaper too.

Push button, paddles, standard lever same difference.

I'm personally a big believer that clutches help transmissions.
I'm in the 50% who agree with you.

Although I think a hydraulic clutch is a little overboard for this application. One could get by with planetary gears for compact application of a three speed and something that resembles syncros on a H pattern transmission for a really light clutch cable pull. Obviously, if you combine a planetary gear and any other gear change method, you can get a six-speed tranny.

Otherwise really cool. About 10 times out of my price range, but still really cool.

So what's next? CVT?

That's what I meant by easy, shifting and matching the revs, letting the bike slide into gear
I don't want to argue endlessly over the point, but it sounds like you think we're in agreement when I don't think we are, and I want to be clear. Words like "gently" and "let it slide into gear" are not what I'm saying. While I do think the load should be reduced when shifting, the shift itself needs to be quick and positive to minimize the clashing of the locking lugs.

Speed matching, as can be done in an automotive trans, is not really an option in a motorcycle because the gearbox does not spend any significant time in a neutral state between gears to allow the shaft speeds to change from the previous gear speed to the next before engagement occurs. Ever try double clutching your sport bike? :thumbsup:

Speed matching, as can be done in an automotive trans, is not really an option in a motorcycle because the gearbox does not spend any significant time in a neutral state between gears to allow the shaft speeds to change from the previous gear speed to the next before engagement occurs.

Are you saying planetary gear sets cannot be used on motorcycles? I'm fairly sure three planetaries with three bands would give you up to eight speeds (no reverse, sorry :thumbsup:). There are probably some optimizations to be made, but that's a trivial way to do it.

Are you saying planetary gear sets cannot be used on motorcycles? I'm fairly sure three planetaries with three bands would give you up to eight speeds (no reverse, sorry :thumbsup:). There are probably some optimizations to be made, but that's a trivial way to do it.
Of course not. Just talking about conventional MC gearboxes, as everyone else has been.

Planetaries would solve the gear clash problem, and mechanical operating systems for them have been around since the Model T at least. 8 speeds from 3 gear sets is a practical limit, although I believe more are theoretically possible. And there's no reason you couldn't have reverse. :confused:

I wonder how much of the impetus to install a clutch and multispeed transmission is practical need vs the desire to replicate the way a dirtbike with an IC engine works.

I wonder how much of the impetus to install a clutch and multispeed transmission is practical need vs the desire to replicate the way a dirtbike with an IC engine works.

I tend to agree with your latter assertion in this case.

It has been clearly demonstrated that a clutch is not needed with an electric drive. IC engines need some kind of clutch or fluid coupling because they produce no torque at zero RPM. Motors generally produce maximum torque at zero RPM, which works well at startup. Diesel electric locomotives don't have mechanical clutches of any kind and they have substantial stall torque requirements :thumbsup: I don't think they have multiple speed transmissions either. I know the older ones don't.

Electric motors are generally constant power machines, whereas IC engines are generally constant torque machines. The RPM range is limited, so a transmission is needed. Depending on your top end requirements, you could design a motor drive without a transmission and many do. Even still, six speeds seems like overkill to me. I tend to think two should be enough.

Even still, six speeds seems like overkill to me. I tend to think two should be enough.
Aren't Diesel electric locomotives just a generator?

Although I agree, I think the six-speed was a "because we can" not "because we need to"

Aren't Diesel electric locomotives just a generator?

Although I agree, I think the six-speed was a "because we can" not "because we need to"

Yes, a diesel engine, a generator, and a several motors (one for each truck I think). I had the chance to to sit in the cab of of and old school (50's era) 1500 HP 16 cylinder diesel electric locomotive. We were in the back (near the "pusher"). The conductor came by and I asked if that was the locomotive back there. He said "yeah, want to take a look?" :confused: I jumped at the chance. He took us back there, it wasn't running at the time. He said, "hang on, let me fire it up". Literally, he turned on one toggle switch, and pushed the "start" button. The lights dimmed a bit, grrr...grrr...grrr... VROOOOM! :busted: That 60 year old diesel was running just like that! Apparently those same engines were used in WWII era diesel submarines, very reliable.

We walked past the engine, which is 10 or 15 feet long and maybe 6' high, most of the locomotive. At the business end of the diesel is the generator. It's a cylinder about 2' long and maybe 3' in diameter. It seems like a very large engine turning what looks like a smallish generator. :thumbsup: The controls are even more sparse. There is one speed lever about the length of your finger. It has three positions: slow, fast, and faster. That's it. There's a direction lever also. There's a serious ammeter that essentially displays torque. The conductor talked to the engineer up front and when he called for a "push" the conductor switched the direction lever from neutral to reverse, and moved the speed lever to the slow position. The ammeter moved up showing the torque was being added :worthy:

That is all there is to it. There is definitely no clutch or gear shift lever. I'm sure the newer models are bigger and maybe more sophisticated, but I think the basic design hasn't changed much. I have heard the generator has six phases and the traction motors are polyphase induction motors very much like industrial 3-phase motors. I think more phases are preferred for smoother operation.

I've also seen the cab of DC metro subways. It's 70's technology, but not much in there either. Of course, there's no engine, just motors powered by 750 Volt tracks. I will say this, those metro cars can move out! Sometimes, when there aren't many riders, the motorman will open it up and you better be holding on to something! In the old days they would get it up to 70 mph on long straights, but I think there are too many stops to do that now. It's the same deal, no clutch, no multi-speed transmission.

I've seen pictures of traction motors, there was even a "How it's Made" episode with a few brief glimpses. They looked to be a bit smaller in diameter compared with the wheels and maybe half the width of the trucks, but it was hard to tell from that perspective.

Edited by msiddalingaiah

Diesel electric locos are "just generators" all right. The engines are massive, as stated. The one referred to above was probably an older F7/FP7 or something like a GP9 at only 1500hp. A few years back, as a birthday present, I got a ride on a BNSF SD60M up Cajon Pass and back down. The power of the things is palpable as they climb. The SD60M uses a 16 cylinder, 3800hp version of the EMD 710 series engine to drive a generator producing 2.8 megawatts. There is a traction motor at each of the six axles. The SD70, 80, and 90 are more powerful yet.

The motors themselves can be switched to generators when the loco is equipped with dynamic braking. In this system, the throttle is pushed forward from the zero point, the motors become generators and feed current through an array of resistor coils (like a huge heater) and a set of fans that cool them, mounted on the roof. They can offer almost as much braking power as they can tractive force this way.

The advantage to having the prime mover (the diesel power source) turn a generator that drives the wheels with motors is the elimination of any transmission or complex drive gearing, and the fact that the engine can operate at a steady state, always at it's most efficient RPM. CSX claims that their fuel usage equates to being able to move a ton of freight over 420 miles with a gallon of diesel.

Typical traction motor. The axle passes through the large bore at the front:

d77.jpg

For scale, a motor casing from a larger loco:

c2007wilm2.jpg

Returning to the electric bike and the transmission, it seems to me that using a multi-speed box would allow the use of a smaller, lighter, less expensive engine with less input power requirements and lower stall torque output while still permitting a reasonable upper road speed range with good acceleration. Maybe not, though.

The one referred to above was probably an older F7/FP7 or something like a GP9 at only 1500hp.

Correct. I believe it was the Minnesota Zephyr, which is an F7A:

pictures%5C17876%5CMNZX788%20F7A.JPG

It's an old machine, but it shows how efficient, smooth, powerful electric drive has been around for a long time.

On a related note, we toured Pepco's coal fired Dickerson electric plant many years ago. They had three 200 MW generators at the time. The turbines are massive, but the generators and exciters are really not that big. Dickerson is also quite old, but all it takes is lots of copper wire/bars and silicon steel.

Returning to the electric bike and the transmission, it seems to me that using a multi-speed box would allow the use of a smaller, lighter, less expensive engine with less input power requirements and lower stall torque output while still permitting a reasonable upper road speed range with good acceleration. Maybe not, though.

I'm not so sure. At the end of the day, it all comes down to power. A transmission can't give you any more power than goes in, it can only trade off RPM for torque. An IC engine needs a transmission because its power band is relatively narrow. Motors have limits too, but the problem is not as acute. One solution is to use multiple, smaller motors meshed with a common output gear. The motors could be connected in series/parallel combinations to electrically "change gears". I think locos play that game also.

The real key to smaller, more powerful motors is materials. If we had materials that could support higher magnetic flux densities, we could make smaller, lighter motors. Some of that happened in the 80's/90's with rare Earth magnets. Cordless drills really took off because of those magnets. Of course, it can be done without magnets, but even the best ferromagnetic alloys have limits as to how much magnetic flux they can support before they saturate.

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