Subject:
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Re: JCB JS220 Excavator
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Newsgroups:
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lugnet.technic
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Date:
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Tue, 25 Nov 2003 23:54:04 GMT
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Viewed:
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4445 times
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In lugnet.technic, Steven Lane wrote:
>
> The functions aren't 'digital like", I know because I too have a digger just
> like Jennifer's. You can move the sticks slightly and get a proportional
> output.
I'd agree with this, it is possible to control the pneumatic valves so that more
or less air gets through them. Rather than the problem with pneumatics being of
digital in nature, to my mind the biggest problem is their elastic or springy
nature.
> I watched Jen's digging vid and I think all she needs is a bit more
> practice.
You want to watch that mouth of yours pal :-) Seriously though, it was indeed
not my best digger performance. Conditions were not ideal on the beach and I was
trying to stay out of camera shot and keep the filming concise etc. In addition
to this....
> I think when digging you should dig with the elbow and use the bucket's crowd
> feature last.
Indeed so, scraping the dirt along with the dipper is the right thing to do,
then curling the bucket to scoop before lifting it out with the boom. The
trouble was that the dipper on the model did not have enough breakout force to
initially shift the sand, but the bucket did, so I had to jiggle the bucket
about a bit to either loosen up the sand and/or get the ideal leverage point for
the dipper, and then the dipper could be moved.
The fact that it dug damp sand at all was enough for me; I had half expected
that it would not be able to.
> My prediction for the future is maybe using different source's of air for
> different functions. Jen's bucket crowds very quickly because it's powered at
> the same pressure as that used to raise the 4 rams of the arm. If you had a
> second supply at quarter pressure the two functions would be more proportional
> to each other.
Yes, I had thought about doing something similar for this model but for a
different reason. With independent pumps for each function then all functions
could be performed simultaneously rather than the air flowing down the easiest
route. I based this on the real JS220 which has 2 hydraulic circuits for the
boom functions. These can be combined into one for extra force, this could be
quite a smart addition to a lego excavator too.
In the end I didn't bother with this in the interests of parsimony. But as you
say, there is always tomorrow.
Jennifer
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Message has 1 Reply:
 | | Re: JCB JS220 Excavator
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| (...) I recind my comment about you needing practice :-),wet sand is the worst type. (...) Thats an even better idea I might borrow (blatantly steal :-) it! Steve (20 years ago, 26-Nov-03, to lugnet.technic)
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Message is in Reply To:
| | Re: JCB JS220 Excavator
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| (...) Hi Tobbe The functions aren't 'digital like", I know because I too have a digger just like Jennifer's. You can move the sticks slightly and get a proportional output. I built my model to test the dual axis control mechanism I came up with that (...) (20 years ago, 25-Nov-03, to lugnet.technic)
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