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 Brushless drivetrain??

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rjw
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PostSubject: Brushless drivetrain??   Sat Jul 03, 2010 10:15 pm

Has anyone had any experience with brushless motors for a combat robot drivetrain...maybe with the Novak sensored setups or something similar?

I heard of a few people playng with this a while back, but it seems to have all gone away???

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PostSubject: Re: Brushless drivetrain??   Sun Jul 04, 2010 5:54 pm

thanks for the info Smile

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Josh Raichel
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PostSubject: Re: Brushless drivetrain??   Sun Jul 04, 2010 6:46 pm

Stay brushed. They have alot of torque at extremely low rpm, which is where you will be spending most of your driving time. stop start stop start etc...

Brushless have a problem with cogging at heavy loads....
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rjw
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PostSubject: Re: Brushless drivetrain??   Sun Jul 04, 2010 7:07 pm

That's why I was asking about the Novak sensored setups.....are they the answer or just hype?

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rdubard
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PostSubject: Re: Brushless drivetrain??   Tue Jul 06, 2010 11:24 am

Well, I kinda agree with the logic of brushed=low speed torque and no cogging,

but. . .

If you are thinking of trying Novak sensored, I would recommend getting as far away from low turns as possible--the 17.5 is not bad, but I would go a high as possible---they have a Crawler that's supposed to be a 21.5 turn equivalent, and the motor should resist cogging better. If you are using something like a Banebots gearbox, the standard 540-can motors that come with those have Kv of 1500 or so, and many brushless inrunners often run at 4000-to-6000 in their Kv. (Just checked the specs on the Crawler and it's 1600Kv)

Also, I think the current draw consideration may be a bit of an issue, depending on how big you want your motor to be. In my opinion, the vast majority of small (15lb and below) bots have way too much power and speed in their drive,and it just gets wasted on spinning the wheels. Since brushless draw so much current (even if they are much more efficient), then you might scale back on the total power output from what you would select in a brushed setup--but then again, I could be way wrong.



Good luck.

ps-I messed with a 5700Kv Mamba Max setup and a drill motor gearbox (36-to-1 gearing ratio , I think) several years back, but that was before I figured how to program the ESC to eliminate delay between reverse and forward, so it was basically useless for drive. It was unsensored, too. I got it to run on the bench, but then ran out of time to mess with it and never got back to it.
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PostSubject: Re: Brushless drivetrain??   Tue Jul 06, 2010 11:25 am

Is this for the MELTY? 'cuz then it would all make a lot more sense!!
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rjw
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PostSubject: Re: Brushless drivetrain??   Tue Jul 06, 2010 11:34 am

rdubard wrote:
Is this for the MELTY? 'cuz then it would all make a lot more sense!!

i've been interested in hearing about any brushless drivetrain success or failure stories, but at the moment, Yes as an option for a melty.




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Josh Raichel
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PostSubject: Re: Brushless drivetrain??   Sun Jul 11, 2010 12:30 pm

Alex Udanis wrote:
Here is some one from swpa using a mamba with a p60 combo
http://farm5.static.flickr.com/4071/4549674606_98ccb5a736_o.jpg

Brushless lifter:
http://farm4.static.flickr.com/3377/4562781419_dc710b4374_b.jpg

Lifter was bad. No torque at all.
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rjw
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PostSubject: Re: Brushless drivetrain??   Sun Jul 11, 2010 4:17 pm

Short discussion and link to some formulas...incase you missed it

http://forums.delphiforums.com/n/main.asp?webtag=THERFL&ctx=search&o=relevance&af=31&be=0&f=this&qu=brushless+kt&Go=Search

All I've really found to be fairly conclusive is that 4 pole motors seem to have better startup than 2.

What's the story on that lifter? looks like a 2 stage bb gbox and not enough mechanical advantage in the lifter mechanism?

It's worth a look at what Neu is clearing out once in a while, although they don;t seem to update very often.

I picked up a couple of 1100 series motors for my little melty for $50 each, which is still pricey, but basically 1/2 retail price.

I am hoping that they will spin up from a dead stop ??

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rjw
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PostSubject: Re: Brushless drivetrain??   Sun Jul 11, 2010 4:59 pm

the pdf link is definitely related to brushless motors??

What are ou sayingabout the lifter? it did or di not have any startup torque? sounds like did not???

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PostSubject: Re: Brushless drivetrain??   Sun Jul 11, 2010 11:58 pm

No that I've noticed

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rjw
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PostSubject: Re: Brushless drivetrain??   Mon Jul 12, 2010 12:33 pm

Computer acting up with this forum again yesterday?????

I haven't done extensive fwd/rev testing of anything but the micro pros , with no load. With a load, on max's , micros and monsters, fwd to rev ....the motor does have to come to a stop. more load = more noticeable, but I don't think there's a 1 second delay...have you called and asked?

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rjw
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PostSubject: Re: Brushless drivetrain??   Mon Jul 12, 2010 12:52 pm

Is the problem bolt pattern, shaft length or both?

Like I said, with no load, the motor seems to go from fwd to rev instantaneouly.

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rjw
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PostSubject: Re: Brushless drivetrain??   Tue Aug 17, 2010 10:54 pm

Alex

I converted Sting to brushless and had a few radio glitches. But now that they are ironed out, I would never go back

You'd be surprised at how much LESS amperage they use.

I am in the process of retrofitting my 12 (It stings) at the moment. The key is to have just anough power to light up the wheels, which sting does easily. with that, there is no cogging. You just light them up and push....

I look at it this way....many use either scorpions or bb escs in 12/15's and they're only good for around 12 amps continuous. No need to slap a 100 amp mamba max pro combo in there, just want more, with brushless reliablility.

Just some thoughts....

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