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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Thu, 27 Nov 2003 01:59:52 GMT
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Viewed:
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4232 times
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In lugnet.technic, Jennifer Clark wrote:
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In lugnet.technic, Ross Crawford wrote:
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One question I have though - did you investigate using an adder-subtracter
in the base? using the centre axle for drive and the clutch gears for
turning might make driving easier, eliminating the lag problem with the
clutch gears, which would only affect turning. Not sure what effect it would
have on the slewing problem though....
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I have done some tests in the past with adder-subtracter based tracked
vehicles and have two major problems with them. The first is that in straight
line travel you are only getting the benefit of one motor driving the tracks,
whereas with the normal method of one motor per track you get two motors
doing this. The other is that I found control of the vehicle less intuitive
with the adder/subtractor.
In any case, with the large gear reduction after the clutch gears, the lag is
really insignificant. You have to really look for it to notice, and if you
didn’t know about it I don’t think you would know it was there.
I think if one was to slew with an adder/subtracter it would drive the
vehicle and turn it simultaneously, probably a worse outcome than the current
situation which only drives the vehicle in a straight line.
My suspicion is that adder/subtracter diff arrangements are more appropriate
for robotic than human control.
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Hmmmm you may be right - I’m still disappointed you didn’t implement automatic
bucket release though ;)
And have you seen those new mini excavators that have the ability to move the
dipper assembly sideways? they have a sort of parallelogram linkage and another
hydraulic cylinder. I should try yo get a pic of one.
Also I saw the other day a JCB backhoe with an extendable dipper - it was
telescopic, with the hose for the bucket & bucket release doubled back inside
it. I’m not sure what it is intended for, but this guy was just using it when he
needed to change the backet, so he didnt have to have the alternate buckets so
close i guess. Anyway, there’s another couple of challenges for you ;)
ROSCO
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Message has 1 Reply:
 | | Re: JCB JS220 Excavator
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| (...) One of these days :-) It is probably doable with the small pneumatic cylinder. (...) I came across this when building the JS70 model on my website, the datasheet mentioned a "parallel offset boom" and I had no idea what it was until I asked (...) (21 years ago, 28-Nov-03, to lugnet.technic, FTX)
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Message is in Reply To:
| | Re: JCB JS220 Excavator
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| (...) I have done some tests in the past with adder-subtracter based tracked vehicles and have two major problems with them. The first is that in straight line travel you are only getting the benefit of one motor driving the tracks, whereas with the (...) (21 years ago, 25-Nov-03, to lugnet.technic, FTX)
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