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Old 04-24-2008, 04:28 AM   #1 (permalink)
Nomadic Chicken
 
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My 1st CVT concept - feedback anyone?

I've designed my own version of a CVT transmission.
Although it may not be as versitile as the Anderson
transmission i'm hoping it would prove to be more
durable.

I'm seeking feed back from the commonsense members
we have (frank, go nuts on this one) and the engineering
members we have for problems, considerations, and anything
that should you feel i should be made aware of when
considering this design.

Obvious things i should point out:
1 - it's not to scale and my animation skills suck.
I also did not bother trying to animate the speed
difference because i feel it should be self
explanitory. (and my animation skills suck)

2 - the "Pressure Plate" that the semi-sphere pushes
against is on a geared/grooven shaft, this is what
makes the shaft turn without the pressure plate slipping
from the shaft.

3 - high tension spring - self explanitory.

4 - the "Sliding Shift Pedel" would have to have some way
to be extreemly lubed for the constant friction of the
ball's shaft.

5 - torque at the elbow joint? durable enough?

As the ball nears the center of the pressure plate
speed should increase.
And, of course, as it nears the edge of the pressure plate
the speed of the transmission gear should decrease.

general feedback anyone?
feasiblity of Design on 1-10?
Durability of design on a 1-10?

Thanks.

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Old 04-25-2008, 12:14 AM   #2 (permalink)
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I've seen simialer ideas carried thru in super mileage vehicles, mostly because they can disengage the drive and coast without drag, and from what I saw that is really the only advantage, friction drive, by nature is not efficient, it is also high wear, when you are trying to get one part to rotate another part it is best to have them as close to possible to being in the same plane, other wise you end up with alot of wear, and alot of heat, the designs that work on simaler ideas as yours that are pushing a 80lb vehicle + 140lb driver tend to wear out within about 20 miles, but that is acceptable if they only have to travel 10 miles to win, it's when they had other problems and had to make more runs around the track, at that point their drive train started to wear out and parts failed.
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Old 04-25-2008, 10:17 AM   #3 (permalink)
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Take a look at the "transmission" on an older Snapper Rear engine Riding lawn mower.

Similar concept, but uses a large wheel rather than the sphere. Works very well in low speed application (don't know about a highway vehicle), holds up well, can pull a load no problem, etc etc.

http://www.odref.com/partsimages/Ste...9;STENS-240440
+
http://www.sjmparts.com/popup_image....D=6455&image=0

Bottom is Smooth

How did you make that animation?
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Old 04-25-2008, 04:27 PM   #4 (permalink)
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i used 3D Studio Max R3.1 (very out of date, current version is 9 or 10)

It's one of three designs I'm looking at.

The upside of this design is that it can be disengaged completely.

The downside of this design is that it never reaches an overdrive gear at the transmission level. in fact, it never even reaches a 1:1.

I like the Anderson CVT design ( http://www.andersoncvt.com website currently down) but the flexible teeth on the cone gears look unreliable to me.

I would like to make a CVT where the main transference is done using a motorcycle chain, but I'm not having any luck on finding a way to do it.

Later on I'll animate 1 or 2 other designs i have in mind and see how that flows with the feedback.

Odref.com isn't bringing up a reference.
I saw the pulley gear on HowStuffWorks.com but a steel belt in high temperature resistant rubber just sounds like it would wear out too easy and be difficult to replace.
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Old 04-27-2008, 10:37 AM   #5 (permalink)
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My favorite cvt design was one that Honda came up with a number of years back for a down hill bicycle, it had a cam that ran rocker arms with moving pivots, so the leverage could be changed, those rocker arms then pushed on ratchets that turned the out put drive shaft, the only draw back of it was that it was to heavy for a bicycle.
I have three Snapper push lawn mowers with self propel that uses that type of drive, it works ok, but you can defently see the wear, we've owned them for around 15 years and I've replaced that rubber wheel at least 4 times, I would guess they might last 50 hours of use, the reason is that the rubber wheel is rolling on a disk, so it's trying to twist the mating suffice, this causes alot of wear.
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Old 04-28-2008, 12:38 PM   #6 (permalink)
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I've only owned 1 snapper and it was a rider (maybe 5 years before it caught fire), never had any issue with transmission. When first looking at it I would have expected similar failures to what Ryland experienced, but I never did. (hence the Recommend)

I keep thinking that shaping the plate like a cone/ hemisphere would help, but I do not think that it would.

Oh well, back to the drawing board.

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