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Subject: Re: Reducing contact resistance for low volt use?
Summary: What do you think of these ping times eh?
Reply-To: You can't see me, and I pass right through planets...
References: <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
X-Newsreader: Forte Agent 1.91/32.564
Date: Tue, 07 Jan 2003 11:08:43 GMT
NNTP-Posting-Date: Tue, 07 Jan 2003 06:08:43 EST
On Tue, 07 Jan 2003 03:39:15 GMT, jmuchow@SPAMMENOTcamlight.com (John
Muchow) Gave us:
>>>>>>>With 20-30 cells in series powering that motor, that's a lot more than
>>>>>>>100A, even with wire and connection resistance.
>>>> You keep getting this ass backwards. Series batteries do NOT
>>>>produce ANY more current than does any one single cell in the pack.
>You keep confusing the configuration of the battery packs used in the
>machines we're discussing and the configuration of the cells tested
>with the discharger I'm building.
>If one cell won't deliver the current I need through the discharger
>(with the MOSFET full on), then I can add a second cell (or more) in
>series. This higher voltage will cause more current to flow. I can
>then measure the voltage across one cell to determine its performance
>at that, now higher, discharge current level.
>>>> Nice embellishment, but quite meaningless. Instead of operating
>>>>outside the levels of design for the batteries AND the motors, you
>>>>should select a motor that does the same job at the PROPER voltage.
>There are almost no components run at their rated values inside a
>If we had the weight allowances to do so, we might just do something
>like that...but I doubt it. Someone would very quickly up the voltage
>to the motor and gear it down more for more torque and acceleration.
>Especially since they know that the motor will still last WAY beyond
>the point they need it to.
>>>> Juicing up a motor over its spec is a step backward as they go DOWN
>>>>in efficiency as you go up in voltage, regardless of the observed
>That's a great theoretical spec but it doesn't affect most builders as
>they'll just increase the voltage further to make up for the
>inefficiencies. I don't care if the motor draws 120% more current at
>double the voltage due to decreased efficiency. I get a LOT more
>torque and speed anyway. It doesn't matter to builders that they
>can't get the theoretical maximum efficiency as they can't fir the
>batteries and motors need to do so in the robot.
>>>>There are plenty of high torque motors that can
>>>>perform at the same (better) levels as your overtweaked motors do.
>I invite you to find one that can perform better than the ones
>currently in use. Hundreds of people have been searching for motors
>for these applications for years and hundreds of motors have been
>tested....by folks who know a lot more about motors than you and I do.
>Any of us can find a high-torque motor that operates more efficiently
>at the voltages we have available. Finding one that has a machined
>(not cast) mount that can survive a high-G smash or being flipped 6ft.
>into the air is another matter. How about surviving a stall-condition
>because my frame and motor mounts got smashed by a 27-lb tool steel
>bar spinning at 2000RPM? Many high-torque motors burn out in seconds
>when stalled. How much would your motor cost? If I have to replace
>one every event, it better be inexpensive. How about not being larger
>than the wheel diameter of my robot (down to 2.5")? Does it have a
>shaft that I can attach my gears or sprockets to?
Very interesting. You should check out old surplus high speed line
printers from the impact printing era. Every spec you named is their,
and they even have position indicators on them. Toothed belt drives.
machine mount faces. small diameter. Wow. I want to take a cam shot
of my motor now. :-]
Actually, I don't think these have the torque that you need.
Nevermind. :-] The body is only 2 inches, but the mounts are 2.5.
The wires feeding it are only 18 Ga, so I doubt it is in the class
you need, but the resolver is cool, double staggered, with calibration
circuitry. Very fine resolution.
The maker is Clifton Precision, a Litton Industries company.
Their demise since the line printer days is unknown, but I doubt that
with a parent like litton, and customers like DEC, they are anything
but thriving still.
I will post a binary in alt.binaries.pictures.misc under the name of
Litton photos with Litton.jpg. It would probably only pull about ten
or fifteen amps. stalled. It is a 24v unit.
> I don't have room
>for a brushless motor controller, better be PMDC. Does it have
>terminals that I can use? Most motors have terminals sized for their
>"typical" applications, not near-stall conditions. Does the motor
>weigh more than the ones we're using? I can't use the extra torque if
>I don't have the weight budget for it.
Maybe they would make good weapons deployment motors. :-]
>Several motors are currently used by the different weight classes in
>combat robotics and R/C plane and car users have their own set of
>motors (with some crossover between the two).
Slot car motors! Go MICRO! Use a tiny bot that evades their
wheels, and gets under them, and zaps them with an HV Discharge.
You guys must watch those things in pits, not cages. :-]
> Lots of research has
>gone into these motors...*especially* the plane/car motors. But, new
>ones are found occasionally and you'd have lots of friends in the
>combat robot or R/C communities if you showed up with all these motors
>you say you can find. I look forward to reading about these motors
>that you'll soon recommend...especially in the R/C and BattleBot
There are plenty of DC motor makers out there. I suppose you
*could* have investigated all of them.
>>>> You are shooting yourselves in the head, much less the foot.
>I feel like doing just that after answering all these separate posts.
Hehehe... the torture of it all.
The word(s) for today...
Dedashort dedashort dedashort short short... The Lone Shorter!
And his brownish side-kick, Copper Man!
I am *Short* Batterystard... Fill Mah Battery! Err... Empty it,
-"Fat Bastard".. hehehe.
I make your battery spit and sputter...
-very old '70s commercial about cars filters, except using the word
"dirt" where "short" is. :-]
Lemmie guess... none of that cheered ya up.
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