Subject:
|
Re: Heavily modified 8880 chassis, succesfully motorised and solar powered.
|
Newsgroups:
|
lugnet.technic
|
Date:
|
Sun, 9 Mar 2003 16:04:14 GMT
|
Viewed:
|
2283 times
|
| |
|
|
> I certainly understand the lacking parts thing. Still, I think it would be fun
> to build a car using the best available ideas for each feature on the car,
> instead of depending on the "built in" ideas of one auto chasis. Has anyone
> ever tried to seriously combine all the very best performing solutions from
> every recourse to make the ultimate composite auto chasis? Sorry for the long
> sentence but I think it says what I mean. It would require many people to
> supply the ideas for such a project. I would like to see it tried but it is
> far beyond my means. Well anyway I wish you the best on your project and will
> look for more postings. :-)
> Best regards to everyone,
> Paul
Nicely ambitious idea, but I don't nearly have enough lego to make it
reality. Right now it's just a 8880 derived solar car for me. :)
Today at about 16:00 the sun decided to come out a bit. There were still
some very thin clouds, and the sun had long passed its highest point, but of
course I still had to try out the car. :)
I meassured the solar panel's Short Circuit Current (the current that goes
through the circuit when shorted) and it was .45 amps. That has been as high
as .74amps on brighter days, so that should give an indication of the sun's
strength today.
The car could easily get going in 1st gear. 2nd gear was somewhat harder but
most of the time it could accelerate from that as well. First gear has a
motor/wheels ratio of 8/81, 2nd gear has a motor/wheels ratio of 4/27. In
second gear acceleration was terribly slow and I didn't have enough room to
really have it get up to speed. In 1st gear, acceleration was good, and at
the end of my 15 meter stretch I was running along with the solar panel in
my hand. :D
At 16 volts the motor can get up to about 5500 - 5750 RPM(the solar panel
can reasonably get up to about 17 volts, it can go higher but then the
current drops heavily), and I think it was somewhat maxed out in
acceleration in first gear, so it must have been doing 8-9km/h. (I won't
bore you with the math behind it)
That's already a lot faster than it has ever done with the lego motor, and
it's with only about 2/3 of sun intensity. With more sun I should easily be
able to max out 2nd gear, which gives almost 13km/h.
Then comes 3rd gear, which has a ratio of 8/27, and thus should max out at
almost 26km/h. I honestly don't expect to get near that. Then we have 4th
gear, which is totally mad, and theoretically maxes out at 39km/h...I can
dream, can't I? :)
Ideally I should have a gear that maxes out at about 18-20km/h. It could
probabbly get going, take very long to accelerate, but still reach maybe 15+
km/h. The thing is, I'm VERY happy with my current gearbox design. It's VERY
strong (has NOT gone 'crack' on me yet, no teeth brusing at all) and uses
pretty much as little as possible gears and axles. Changing a gear ratio is
going to require big modifications. My best hope of changing it without
altering the gearbox is by doing something about the reductions between the
motor and the actual gearbox. It's now done by 2 pairs of 16&24 tooth gears
(giving a 4/9 reduction before the gearbox itself). If I could somehow work
out the construction right to change that into one 8&24 tooth reduction,
giving a 1/3 reduction before the gearbox, that would probably be perfect,
and would make 3rd gear max out at 19km/h. It's just going to be hard to
allign the motor and the rest of the axles well enough for that, while
keeping it all strong. I'll post an updated .ldr of my current design soon,
so anyone generous enough with his time can help me come up with a good
construction to make the 'perfect' drive ratio reality. :D
|
|
Message has 1 Reply:
Message is in Reply To:
40 Messages in This Thread:
 
 
 
- Entire Thread on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
This Message and its Replies on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
|
|
|
|
