Subject:
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Infinitely Variable Transmission (IVT)
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Newsgroups:
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lugnet.technic
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Date:
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Sat, 29 Mar 2003 01:14:07 GMT
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Viewed:
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2583 times
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I have replicated some more technology used in agriculture.. ;) IVT
transmissions are used in tractors for a few years, but are also appearing
in busses, cars and other vehicles.
An IVT is a Type of CVT (continuously variable transmission). An IVT
generally uses planetary gears. The engine is connected to the sun gear,
planet gears are connected to 1 planet carrier and the whole thing runs
inside a ring gear. The planet carrier is connected to an output shaft, the
ring gear is connect to the engine but through a device that can speed up or
slow down the speed. This is often done through hydrostatic drive, which
allows variable speeds but is not powerful enough for heavy applications.
Hydrostatic drive will do for the ring gear of an IVT.
The planet gear will spin at one speed, the ring gear will rotate against
it. When they spin at the same RPM the planets will not move, but if the
ring gear is sped up, the planets will start traveling in one direction
which rotates the planet carrier, which then rotates the output shaft.
When the ring gear is slowed down, the planets will travel in the other
direction, reversing the output shaft.
This gives us 3 states:
Forward movement
Reverse movement
Hold (PowerZero)
PowerZero will keep the output shaft at one position, you can not turn the
outputshaft in PowerZero. It uses engine power to keep the output shaft
still.
John Deere has a video and info on how it works:
http://www.deere.com/en_US/ag/feature/2002-product-intro-ivt-7000ten-7020ser
ies-6420tractors.html
First problem I had was the absence of ring gears in Lego. The only thing
that has a suitable ring gear is a turntable. Unfortunately the turntable
cannot be powered, so I mounted a second turntable on it of which I used the
outside gears to power the ring on the other turntable.
I built this:
http://www.brickshelf.com/gallery/FlyingDutchman/IVT1/ivt3.jpg
The 2 bottom shafts are engine and control, the top is the output shaft.
More:
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=38552
By powering the engine shaft by a motor, and the control shaft by another
motor which speed could be slowed down using a potentiometer to reduce
voltage, and some gearing, I was able to make that work. :)
Barely though... The control motor did not have enough power at lower
voltages to keep that big thing turning.
I am trying to get NEW Lego geared motors. If you have new motors for sale,
let me know I need them.
The top of the top turntable can turn freely since there is too much
friction on them to mount it solid to a frame, same with the bottom of the
bottom turntable.
Unfortunately this design is too big to be used in anything. Using newer
parts which I do not have I could construct a single turntable version in
LDraw.
Since the power of the motor at low voltages was not enough to keep stuff
turning I started devising a way to use the "engine" motor and the control
motor together using a differential. Basically the "engine" motor would run
the planet gear, but would also be used to power one side of a differential
and the control motor would power the otherside, then the differential would
be connected to the control shaft. In theory it should work. I just never
got the gearing right...
Why didn't I get the gearing right you may ask. Well I ACCIDETALLY built an
IVT using a differential!
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=38554
Basically it is a subtractor with negatives. The "engine" turns slower than
the max speed and faster than the min speed of the control motor with the
potentiometer. Running the control side faster than the engine side gives me
one direction and running it shower than the engine side gives me the other
direction and running them at the same speed gives me PowerZero. Of course
they turn against eachother to make it work.
I think this is long enough, I suggest you watch the video on the John Deere
site and look at the LDraw if you want to fully understand it.
Questions are welcome.
Gerard Steenbeek
BTW. We took delivery of a new John Deere tractor with the IVT transmission
so I was playing with it for an hour or so and it is really cool in real
life.
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Message has 2 Replies:
 | | Re: Infinitely Variable Transmission (IVT)
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| "Gerard Steenbeek" <interdutch2000@hotmail.com> wrote in message news:HCHKrE.20r7@lugnet.com... (...) (URL) ies-6420tractors.html This seems overly complex. Why not just have the hydraulic pump and motor drive the rear wheels? Why do all the other (...) (21 years ago, 29-Mar-03, to lugnet.technic)
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