Greg Owen wrote:
> Jeff Shanab wrote:
>
>>Actually if I had the ability to play there is one more idea I would
>>like to try.
>> Use a locking torque converter. It would start at 3:! or 4:1 then
>>transition smoothly up to near 1:1 then you lock it in to 1:1.
>
>
> Jack Murray is trying it and posted about it a week or so ago:
>
> http://www.mail-archive.com/[email protected]/msg08016.html
>
> See #8, "CVT results update"
>
> Please pardon me for a moment as I talk through and ask some basic
> questions. I've been trying to absorb a lot of information and want
> to check some of my assumptions.
>
> It sounds like some people directly connect their motor output to
> their wheel output, in the sense that some number of axles or gears
> maintain a X:Y rotation ratio at all motor speeds. This has the
> advantage of simplicity, but the disadvantage that the high starting
> torque of motors places strain on the components and causes shearing
> and breakage (as seen by all the pretty pictures this morning).
> Another disadvantage is that the motor cannot operate in its most
efficient mode across all speeds.
>
> Jack Murray, at least, has tried a Torque Converter. This seems to
> soften the impact of high initial torque on the rest of the
> connection, yet allow a locked X:Y rotation ratio once a certain speed
is reached.
> The advantage is that it takes the stress off the components, the
> disadvantage is that the motor is still unable to adjust into the most

> efficient mode across all speeds.
>
> Although Jack called it a CVT, I don't think a torque converter is
> truly a CVT - it's variable only up until it locks, and the variable
> stages essentially trade off efficiency for smoothness.
>
> As I understand it, a real CVT would allow the gear ratio to be
> adjusted at any speed to allow the motor to run at its most efficient
> RPM, and to lessen the impact load during high-torque starts. Doing
> this would require somewhat smart coordination between the motor and
the CVT.
>
> So, that's my set of assumptions and beliefs based on what I've been
> reading. Are these correct, or am I missing aspects?
>
> My followup questions are essentially these:
>
> 1) Is some sort of impact softening mechanism like a torque converter
> generally necessary, except in racing vehicles where off-the-line
> torque trumps the goal of "not breaking stuff"? Or is this something
> dependent on calculations such as motor characteristics, drivetrain
> design, and weight of vehicle?
>
> 2) Are there other advantages to the Torque Converter I'm missing? Or

> is the 1:1 ratio at speed a better end case than I imagine?
>
> 3) Does the stress of high torque overcoming inertia impact the motor
> as well as the drivetrain?
>
> 4) Is anyone running a CVT? What kind? Native or aftermarket?
> Special considerations?
>
> Any insight people can share on these questions is greatly
appreciated.
> I'm a newbie and a techie so trying to understand all the car details

> is both difficult and fun.
>
> Thanks!
> Greg
>
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