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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 1:03 am

.


Last edited by Alex on Wed Mar 23, 2011 5:29 pm; edited 1 time in total
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rjw
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PostSubject: Re: Brushless drivetrain??   Sun Jul 04, 2010 5:54 pm

thanks for the info Smile

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PostSubject: Re: Brushless drivetrain??   Sun Jul 04, 2010 6:26 pm

If you have the amps for it I would say go for a sensorless system

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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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PostSubject: Re: Brushless drivetrain??   Sun Jul 04, 2010 8:08 pm

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

There was a local team using a Novak 17.5 sensored motor and they were still sputtering on start up so I'm gonna say it might be a little better but they are still lacking on torque.

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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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PostSubject: Re: Brushless drivetrain??   Sun Jul 11, 2010 11:29 am

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

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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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PostSubject: Re: Brushless drivetrain??   Sun Jul 11, 2010 1:15 pm

Josh Raichel wrote:
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.


Because for a lifter you need starting torque.

RJW: Have you found any correlation between start up torque and kv?

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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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PostSubject: Re: Brushless drivetrain??   Sun Jul 11, 2010 4:33 pm

rjw wrote:
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 ??

I don't believe those equations apply to brushless motors. I used a standard equation on the lifter and it said it should of had 20+ pounds at the tip and i didn't actually lift even 5lbs due to cogging at start. Sure it may have that much torque while its running but i believe it has a lot of start up.



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