Subject:
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Re: z14 bevel gears (was Re: hinges and bevel gears, was Re: 60 degree problem
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Newsgroups:
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lugnet.build
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Date:
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Fri, 30 Jul 1999 15:26:44 GMT
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Viewed:
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2042 times
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In lugnet.build, Robert Munafo writes:
> Okay, I'll bite -- how do you get 7/6 to be anywhere close to SQRT(3)? 7/6 is
> 1.167, and SQRT(3) is 1.732. Is there an additional 2:3 ratio hidden inside • the
> "8880 transmission"?
No, I just failed to mention that I gear down by 2, then up by 7/6;
which is quite close with 1.714. Both have the same center distance, which
is extremely helpful with the 8880 setup.
>
> Also, I'm having a little trouble figuring out how the transmission works in
> the 8880. The instructions are here:
>
> http://www.kl.net/scans/8000/8880/
>
> and I've figured out that it has four wheel drive with three differentials, • and
> a mechanism for engaging one of four different output shafts to the input (or
> the other way around, because you turn the wheels to make the pistons go) --
> but it's still a little hard to see how it all fits together. It also looks
> really spread out so I'm wondering if all that stuff is really part of the
> transmission.
Yes it is. Why it is spread I don't know; it makes frame or transmission
changes a bit more effort, but yields some extra long axles.
The mechanism really joins one of two input shafts to one of two
output gear sets; the output gear set are linked such that one
input shaft gets its direction reversed compared to the other, which
means that a single reverse gear is not possible unless you space the
shafts out some (1/4..1/2 stud?), which is a tad difficult as the
gear shift plate has to be centered over them.
So, in the normal case (4 fwd gears), the input shafts are linked
with a neg. ratio, while the output gears are linked with a pos. ratio.
>
> - Robert Munafo
>
> In lugnet.build, Gregor Benedikt Rochow writes:
> > [...]
> > [2] I found a great new use for these - at 1.5 studs center distance
> > (or the equivalent 1-stud-over, 1-brick-up),
> > they mesh well with the replacement z12 bevel gear,
> > particularly if you use 2 z14s back-to-back and 2 z12s fac-to-face.
> > Ratio is 6:7, of course. Very useful for a very compact 8880 (SuperCar)
> > transmission; 7/6 is very close to SQRT(3), so 7/6 on the input
> > and 3/1 on teh output axles results in ratios of (roughly)
> > 1, SQRT(3), 3, 3*SQRT(3). Very nice ratios, and very compact, particularly
> > combined with the V8 moved to the front and FWD only (will Consumer
> > Affairs sell me 4 more 8880 wheels, so I can have 2 FWD cars?).
NO. But hey, the MT dragster is only $50 for 390 parts, and
includes 2 8880 wheels= :P
-gbr
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