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[mKlRivPwner]

okay.  I know I'm probably beating this to death.  But thanks to a wonderful gift called "ADD" I have to keep thinking about it until I fix all the bugs out of it.  Here we go!

Set up:
Motor     Jackshaft 1     Jackshaft 2      rear end
12           24                   NA (direct drive shaft)
              9 (1a)              27 (1b)
            Clutch 1
             12 (2a)             24 (2b)
            Clutch 2
             16 (3a)             20 (3b)

Have Clutch one spring at 1000 RPMs.  Have Clutch 2 spring at 1350 RPMs.  All gears on Jackshaft 2 will be fixed.  Hears 1a and 2a will be on one-way bearings.

This way when torque is shifted from 1st to 2nd, clutch 1 will grab gear 2a, but gear 1a will be 'pushed' by 1b.  Gear 3a will still be free spinning thanks to the clutch between 2a and 3a.

Likewise, when torque is shifted from 2nd to 3rd, clutch 1 and 2 will be engaged so 3a will drive jackshaft 2 and the drive shaft.  Gears 1a and 2a will be freespinning thanks to the 'push' they will receive from their counerparts on Jackshaft 2.

Completely automatic and perfectly smooth transition.

Of course now I want to go build one  :-(

[Bogan]

have you heard of the zero shift gearbox? sounds like it does exaclty what you want

[mKlRivPwner]

Looks real neat, but it's still electronically controlled and monitored.  I know that it isn't much electricity, but the point is more "I'm not electrical engineer."  I'm not going to wire up a transmission and all the controllers.  And modifying a salvaged transy would be overweight and require a fluid resevoir, pumps and pulleys...  I know adding a transmission will already produce internal friction which will create drag on the motor and create inefficiency.  Adding a pump and pulley system will increase that.  And adding electronics to monitor and control the whole thing will just decrease it that much more.  So this whole deal plus me not wanting another "advanced electric hinderence" to figure out and try to work out led me to attempting to build a purely mechanical, self-contained transmission.  Automatic just made sense, because they can be self-contained and self-monitoring if they are done right.

So a CVT, or a Zeroshift, or a salvaged and modified manual might make sense to many of you, but I find the simplicity and contained nature of the mechanical automatic transmission I described below to be a great fit for the concept of an electric motorcycle.

[Bogan]

ah, i thought your clutches were electronically controlled as well, after reading closer it seems they are centripetal clutches which engage at different rpms, sounds like a very neat idea. There are a few possible issues i can see with applying it to an electric bike:

Space and weight, extra chains, clutches, gears, gearbox & oil will take up space and add weight, so you will probably have to cut down on a battery or two, decreasing the range.
Efficiency, extra chains, gears etc will create a significant amount of drag i would imagine, furthur decreasing the range.
And automatic shifting may not be a very good idea on a bike, when the centripetal clutch engages the motor will have to decrease speed rapidly, which may jolt the rear wheel a bit, and also greatly reduce the available torque, if it happens when powering out of a corner the bike could tip in and startle the rider.....

Also just though of another thing, when the motor and jackshaft A get to clutch engaging rpm, the gear ratios will change, jackshaft B and the wheel speed wont, so jackshaft a will greatly decrease its speed, below the clutch engaging speed, so a standard centripetal clutch wouldnt work there, it would just burn out rapidly. You could use some sort of locking centripetal clutch, but then would run into problems with downshifting.

Hopefully ive understood you design right, if not disregard most of my comments!

[Bogan]

just though about it some more, putting the clutches on jackshaft B should overcome that last problem

[mKlRivPwner]

Switching the clutches to Jackshaft B should resolve the RPM drop issues.  This and Clutch Slipage should alleviate the jossle between gears.  How much it will alleviate, I won't know until I build a prototype at least.  And unfortunately that could be a ways off.

As for space, By situating the "transmission" longitudnally with a drive shaft instead of an extra chain will help.  The transmission itself shouldn't take up any more space than the motor would already be taking up.  And by mounting the motor with the shaft facing forward will allow the "transmission" to mount alongside for the most part.

Weight and mechanical drag are the only major concerns.  And again, the true effect of this will only be known once a prototype is built and tested. 

I'll keep anyone interested updated with progress as I make it. 

[cheese]

How about a planetary gearbox?

[mKlRivPwner]

The short answer is buildablilty and price.

A planetary would cost quite a bit, and would not be something the average person could reasonably construct in their garage.  On top of this, there are electronic controls that I am trying to avoid.

When it comes down to it, if I were to add a true transmission, I would be compelled to add a CVT.  It's simplicity, compact size, and wide range of gear ratios would be best suited for EV's.

By adding a planetary gearset, I would be moving into a realm where the average owner/operator would no longer be able to maintain the machinery him/herself.  Instead, it would need to be serviced in a transmission shop if anything were to go wrong.  In this build, the average motorcycle rider would be able to open the gearbox and understand sprockets and chains.

An interesting idea.  But I'm going to leave that one to the manufacturers.

[NewAge]

Agreed, even the shop engineers are ready to throw in the towel on the trans concept (complexity and cost),
they are now taking a closer look as adapting a comet cvt.

[chdfarl]

I plan use a two stroke gear box on my build removing 1st gear to lose friction and weight since an electric motor puts out good torque at low rpm but ill play with that. If you don’t know a two stroke crankcase is sealed off from the transmission so its easier to cut off without blocking off a big hole in the case the other thing is that they are smaller and lighter I know there are friction and weight losses with a gear box but those big underdrives people use limit top end and show that even an electric motor struggles under that type of load and I figure there would be a big current draw when accelerating

[chdfarl]

I found this from a link off V is for Voltage im becoming a big fan of the guys at Motorcyclist Magazine i plan to use a gear box in the build ive been planning based on my understanding of how they work that is explained quite well in that article

http://www.motorcyclistonline.com/newsandupdates/122_0910_electric_bikes_go_green/index.html