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colin
Joined: 16 Jun 2004
Posts: 102
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quote:
Originally posted by Spockie-Tech:
The Chinese are masters of "value engineering" -
The Deacons Masterpiece
a poem by Oliver Wendell Holmes
Have you heard of the wonderful one-hoss shay,
That was built in such a logical way
It ran a hundred years to a day,
And then, of a sudden, it - ah, but stay,
And I'll tell you what happened without delay,
Scaring the parson into fits,
Frightening people out of their wits,
Have you ever heard of that, I say?
Seventeen hundred and fifty-five,
Georgius Secundus was then alive,
Snuffy old drone from the German hive.
That was the year when Lisbon-town
Saw the earth open and gulp her down,
And Braddock's army was done so brown,
Left without a scalp to its crown.
It was on the terrible Earthquake-day
That the Deacon finished the one-hoss shay.
Now in building of chaises, I tell you what,
There is always somewhere a weaker spot,
In hub, tire, felloe, in spring or thill,
In panel, or crossbar, or floor, or sill,
In screw, bolt, thoroughbrace, - lurking still,
Find it somewhere you must and will,
Above or below, or within or without,
And that's the reason, beyond a doubt,
A chaise breaks down, but doesn't wear out.
But the Deacon swore (as Deacons do),
With an "I dew vum," or an "I tell yeou,"
He would build one shay to beat the taown
'N' the keounty 'n' all the kentry raoun';
It should be so built that it couldn' break daown:
"Fur," said the Deacon, "'t 's mighty plain
Thut the weakes' place mus' stan' the strain;
'N' the way t' fix it, uz I maintain,
Is only jest
T' make that place uz strong uz the rest."
So the Deacon inquired of the village folk
Where he could find the strongest oak,
That couldn't be split nor bent nor broke,
That was for spokes and floor and sills;
He sent for lancewood to make the thills;
The crossbars were ash, from the strightest trees,
The panels of white-wood, that cuts like cheese,
But lasts like iron for things like these;
The hubs of logs from the "Settler's ellum,"
Last of its timber,--they couldn't sell 'em,
Never an axe had seen their chips,
And the wedges flew from between their lips,
Their blunt ends frizzled like celery tips;
Step and prop-iron, bolt and screw,
Spring, tire, axle, and linchpin too,
Steel of the finest, bright and blue;
Thoroughbrace bison-skin, thick and wide;
Boot, top, dasher, from tough old hide
Found in the pit when the tanner died.
That was the way he "put her through."
"There!" said the Deacon, "naow she'll dew!"
Do! I tell you, I rather guess
She was a wonder, and nothing less!
Colts grew horses, beards turned gray,
Deacon and Deaconess dropped away,
Children and grandchildren - where were they?
But there stood the stout old-one-hoss shay
As fresh as on Lisbon-earthquake-day!
Eighteen Hundred; it came and found
The Deacon's masterpiece strong and sound.
Eighteen hundred increased by ten;--
"Hahnsum kerridge" they called it then.
Eighteen hundred and twenty came;--
Running as usual; much the same.
Thirty and forty at last arrive,
And then came fifty, and Fifty-five
Little of all we value here
Wakes on the morn of its hundredth year
Without both feeling and looking queer.
In fact, there's nothing that keeps its youth,
So far as I know, but a tree and truth.
(This as a moral that runs at large;
Take it, - You're welcome. - No extra charge.)
First of November - the-Earthquake-day,
There are traces of age in the one-hoss-shay,
A general flavor of mild decay,
But nothing local, as one may say.
There couldn't be, - for the Deacon's art
Had made it so like in every part
That there wasn't a chance for one to start.
For the wheels were just as strong as the thills,
And the floor was just as strong as the sills,
And the panels just as strong as the floor,
And the whipple-tree neither less nor more,
And spring and axle and hub encore,
And yet, as a whole, it is past a doubt
In another hour it will be worn out!
First of November, 'Fifty-five!
This morning the parson takes a drive.
Now, small boys, get out of the way!
Here comes the wonderful one-hoss shay,
Drawn by a rat-tailed, ewe-necked bay.
"Huddup!" said the parson. Off went they.
The parson was working his Sunday text,
Had got to fifthly, and stopped perplexed
At what the - Moses - was coming next.
All at once the horse stood still,
Close by the meet'n'-house on the hill.
First a shiver, and then a thrill,
Then something decidedly like a spill,
And the parson was sitting up on a rock,
At half-past nine by the meet'n'-house clock,
Just the hour of the Earthquake shock!
What do you think the parson found,
When he got up and stared around?
The poor old chaise in a heap or mound,
As if it had been to the mill and ground!
You see, of course, if you're not a dunce,
How it went to pieces all at once,
All at once, and nothing first,
Just as bubbles do when they burst.
End of the wonderful one-hoss shay,
Logic is logic. That's all I say.
------
OK, so you didn't really need to read all that,
But bait your breath, and don't say drat,
A valuable lesson you can learn today,
Build it well, that is to say;
Don't over-engineer,
It won't help to re-gear.
P.S. The poem was written in 1858, so chinese might be the masters but the concept is nothing new.
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Sat Jun 19, 2004 10:08 pm |
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Nick
Experienced Roboteer
Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW
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I re-worked all my drill motors over the weekend and did some proper testing on them with very interesting results:
Taking a totally new XU1 motor, I ran it and measured the current using a reasonably accurate clamp meter. After a 5 minute run-in it drew 2.5A.
I then totally dissasembled the gearbox and cleaned every trace of grease out, then reassembled with all metal gears. With no lube at all, the gearbox was much easier to turn by hand and even had a little 'run on'. Running it again for 5 minutes gave a current of 2.7A. That wasn't what I expected, given that the gears turned more easily by hand. The moter was WAY noisier too. This could have been due to the new metal gears spinning at high speed in the first stage.
I then pulled everything apart again and applied a generous coat of white lithium grease to everything (but far less grease than it came with). Running this for 5 minutes gave a current reading of only 1.9A  and the noise was down but still greater than with the original grease packing.
Conclusions:
1) The grease that comes witht the motor is not all bad but is probably mainly for noise reduction.
2) Reducing the lubrication is definitely a bad idea; more noise, current and heat.
3) Lithium grease is a huge improvement on the chinese stuff! I saved over 500mA of current drain, which equals a longer run time, less motor heat and cooler FETs too  It doesn't get runny when hot like the original stuff does, either.
More thoughts:
Glen is right about my motor experiences with broken pins, except that they were all in the second stages. That means that I moved the weakest link from the plastic gears to the pins. This means that the gearboxes should have transmitted more energy before they broke, the trick is to have a wheel that spins before the pins snap... I have been getting better results with 3" wheels.
I found the 'secret' to reassembling a gearbox properly! Its next to impossible to explain in writing, but I will be happy to show anyone who is interested at the next event.
_________________
Australian 2015 Featherweight champion
UK 2016 Gladiator champion
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Mon Jun 21, 2004 10:10 am |
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Nick
Experienced Roboteer
Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW
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Yes, I tested with no load so the results should be reproducable by everyone.
What a lower current draw and lower heat means is that the motor is not wasting energy just pushing the gears around and has more output power to push your bot around the arena.
When the motors are in a bot and under load, I would expect that top speed would be a little higher, run time should be longer, and all your drive train parts (battery, controller, motor, etc) should be a little cooler. The difference might not be much, but even 10 seconds of full power could turn a loss into a win.
To get the metal gears to fit, I ground off the raised section on one side of the gear. I finished it off with a fine file to smooth out the grind marks and remove the burrs between the teeth. A 'Vise-grip' locking wrench is perfect for holding the gear - the teeth on the Vise-grip jaws mesh with the gear teeth.
When replacing the new gears in the gearbox, put them in with the flat side down, away from the motor. That way you getthe most mesh with the motor pinnion.
_________________
Australian 2015 Featherweight champion
UK 2016 Gladiator champion
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Mon Jun 21, 2004 11:20 am |
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Ajax
Experienced Roboteer
Joined: 17 Jun 2004
Posts: 298
Location: Sydney
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quote:
Originally posted by Nick:
Yes, I tested with no load so the results should be reproducable by everyone.
What a lower current draw and lower heat means is that the motor is not wasting energy just pushing the gears around and has more output power to push your bot around the arena.
When the motors are in a bot and under load, I would expect that top speed would be a little higher, run time should be longer, and all your drive train parts (battery, controller, motor, etc) should be a little cooler. The difference might not be much, but even 10 seconds of full power could turn a loss into a win.
To get the metal gears to fit, I ground off the raised section on one side of the gear. I finished it off with a fine file to smooth out the grind marks and remove the burrs between the teeth. A 'Vise-grip' locking wrench is perfect for holding the gear - the teeth on the Vise-grip jaws mesh with the gear teeth.
When replacing the new gears in the gearbox, put them in with the flat side down, away from the motor. That way you getthe most mesh with the motor pinnion.
The Metal gears will increase the noise output of the motor no mater what type of grease is used. A heavier grease will help reduce the noise, but noise is not a problem realy. (noise as in sound level not RF)
Nick did you also clean all the ball bearings & shaft under the circlip the re apply grease there as well. this will give a very slight improvment, not noticeable though.
Everyone needs to remember that when cleaning there motors. Be carefull though one false move and you have little balls every where.
_________________
It's all about the destruction.
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Mon Jun 21, 2004 3:28 pm |
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RoboWars Australia Forum Index
-> Technical Chat
did you do the test with no load? if so do those result tell you much about the savings/improvments when they are run in your bot?
. I also see on the forums that the US guys split the gearboxes fairly often.