Subject:
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Re: Automatic Transmission
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 30 Nov 1999 23:47:35 GMT
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Viewed:
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526 times
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In lugnet.robotics, Robert Eddings writes:
> I have been working on building an automatic transmission for quite some
> time but have yet to come up with satisfactory solutions. I am looking
> for additional ideas to try. What I consider to be an automatic
> transmission in this case is:
>
> [Drive train defaults to a high speed / low torque gear ratio. When
> resistance on the gear train causes the motor to stall, the drive shaft
> transfers (slips or flips) to another gear train with a lower speed /
> higher torque gear ratio. When the resistance is lowered, the drive
> shaft reverts back to a higher speed / lower torque gear train.]
>
> One experiment used a worm gear that slid along the drive shaft. The
> worm gear first drives the high speed / low torque gear train. The worm
> gear is kept from sliding forward by a collar in front of the worm gear
> that slides freely on the drive shaft and is connected to rubber bands.
> When the resistance to drive the first gear train is greater than the
> resistance caused buy the rubber bands, the worm gear slides forward to
> engage another gear train. This almost works but I can't keep the worm
> gear from binding between the gear trains and causing a stall.
I haven't built a transmission this way, but I have built a number of sliding
worm gear mechanisms. I've found that you have to leave enough room between
the drive gears so that the worm gear is only in contact with one at a time.
(This is especially true in your case, where all of the drive gears are
presumably coupled to the same output axle at different gear ratios.)
To make sure that the gear crosses the gap without getting lost between gears,
I use extra stationary gears (which won't rotate) as "stepping stones". These
gears are mounted halfway between the drive gears, and usually on the other
side of the worm gear from the drive gears. When the worm gear is working, it
sits between the stationary gears, in contact with a single drive gear. When
it hits a stationary gear, it begins to slide until it gets to the next gap.
Sorry, no pictures yet. (I've got a backlog of creations that I'm trying to
post pictures of, but where does the time go?)
I'm not sure if this technique is compatible with the automatic transmission
that you describe, but I think it might work. One drawback with this approach
is that the output drive shaft will stop spinning while the worm gear is
sliding, which would be disastrous in an automobile tranny. (Have you ever
stepped on the brake by accident when you were reaching for the clutch?)
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Message is in Reply To:
 | | Automatic Transmission
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| I have been working on building an automatic transmission for quite some time but have yet to come up with satisfactory solutions. I am looking for additional ideas to try. What I consider to be an automatic transmission in this case is: [Drive (...) (25 years ago, 30-Nov-99, to lugnet.robotics)
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