Could someone point me in the direction on how good a meter to get for checking the resistance on brushless windings?

Thanks Kevin

Any Fluke digital multimeter should work well. I would choose a Fluke because they are well known to be high quality, accurate and durable. One such would be the Fluke 115

From Amazon - http://www.amazon.com/Fluke-115-Compact-True-RMS-Multimeter/dp/B000OCFFMW

From eBay - http://shop.ebay.com/?_from=R40&_trksid=m38.l1313&_nkw=Fluke+115&_sacat=See-All-Categories

hank, those meters are not very good at measuring low resistance values.

For a good measurement you need a good meter that can read in the 0.001 ohm range. like this one:

http://www.testequity.com/products/1281/

what is the reading that we are looking for on most motors because i dont know very many hobby shop owners that want to buy a 400+ meter.

Yeah, what resistance readings are we looking to measure? Is a milliohm meter needed?

good question, haven't been able to get any info from Novak yet either

Wouldn't checking these numbers create a hassle and run off new racers? What would someone hope to gain by knowing them? .01 , .1
per lap?

I thought from reading other posts, our intention is now to make racing less confusing for the NEW Guy, and less of a hassle for the old ones~~ <just kidding>

I think NOVAK recently said they aren't going to provide any numbers any longer...

I guess we can get more technical I can take my HP3458a meter or my 8508a referance multimeter and right before we check the motors I can calibrate my meters using a fluke 8520a calibrator. Sounds like fun

Yes and no. Brushed stock motors used to easy to tech because of the way they were designed. Older brushless motors have no external way to see what wind they are... my understanding is that all newer brushless motors are required to have a perm. marking on the outside of the can. Of course people could rewind the motors (both brushed and brushless) and no one would know it unless it was tore down and unwound.

The need for some to actually want to know the resistance of a motor's windings is fascinating. We have run 27T brushed motors for 20+ years. Can anyone answer this.... what is the resistance of one pole of a brushed motors 27T armature? If you don't know and never measured one, then why do you HAVE to know what it is for a brushless motor when you were never concerned about it with brushed motors?

The problem lies in the fact people ARE rewinding motors. It's much easier to check the motor with a meter and say it's illegal vs. the process of tearing it down. Even then, you can wind a motor by hand much more efficiently than a machine can do it So even if you unwind it and it shows the proper wind, a handwound will have a distinct advantage because it has less wire in it than a machine wound motor.

I had a motor of mine at snowbirds with another driver that was DQ'ed because 1 pole was a tenth below minimum. I'm happier with that than having a motor brought back to me in pieces.

shoot boylan an email he can tell you what they looked for

All of our BL motors are wound by hand right here in SoCal. I think it is amusing to think that some "tuner" can rewind a motor better than our winders who have experience winding thousands of motors.

Also, we have designed proprietary testing equipment to check motors at every stage of manufacture (including the more accurate resistance measurements). Maybe the Chinese imports are wound inconsistently and need to be rewound.;)

We stopped offering guidance on motor testing due to the somewhat vicious comments and criticism from posters on this forum. Also, because no other motor seller was offering numbers. Now we encourage race directors to compile their own databases of measurements for use in their regions.

Good post. everyone and there brother wants to know everything about the motors, yet when they find out that not every motor is the exact same then they get upset. i say thanks to novak for giving us good motors and having a trade up program for us racers!

let us just try our best to make racing easier for the new racer rather then make everything so complicated! yes the top guys want to know every detail to pinch out the last 10th of a lap but sometimes knowledge we have discourages the new guy. just my 2cents though.

All of our BL motors are wound by hand right here in SoCal. I think it is amusing to think that some "tuner" can rewind a motor better than our winders who have experience winding thousands of motors.

Also, we have designed proprietary testing equipment to check motors at every stage of manufacture (including the more accurate resistance measurements). Maybe the Chinese imports are wound inconsistently and need to be rewound.;)

We stopped offering guidance on motor testing due to the somewhat vicious comments and criticism from posters on this forum. Also, because no other motor seller was offering numbers. Now we encourage race directors to compile their own databases of measurements for use in their regions.

me thinks this had something to do with novak dropping the posting of numbers idea?

http://www.hobbytalk.com/bbs1/showthread.php?t=202857&page=34

Humpty,

We did have low inductance numbers for both 21.5 and 17.5. The low for 21.5 is 50.0 for each coil and 33.6 for 17.5. I do think the numbers need to be reviewed and changed for both classes. Some of the older motors have a low inductance reading. Every racer was allowed to have 3 motors. The extra motors check on Saturday night was within there limit. There was only 1 motor lower than 50.0 in 21.5 and it did not leave the tech trailer until the event was over. The motors that you are referring to check ay 51.5 and 52.4. The motor that won the 21.5 race was a 55.4 motor. We had many discussions about that over the weekend. I am sorry that you did not like the way motor tech was run.

Sam Ledford


Are you sure it was 33.6 for 17.5 class? I know that the ROAR rule book clearly states 36.5 per pole for Novak motors measured from the ring to A, B, C.

EA


If that is the case then the motor I had with me and the one I bought onsite Friday morning at the hobbyshop were both illegal.....35.3 and 35.5!!!!!



http://www.roarracing.com/approvals/brushlessmotors.php

Stock Novak Novak 3417SS 17.5 Pro 36.5 February 15, 2008

Good ol'e Novak quality control.

Right there in color!

EA


We had same issue at On Road Nats..


Hi Sam,

I know you and Mike did an Awesome job from everyone I have talked to from the race and not trying to question your's or Mike's abilities but why was the min changed to 34.7 when the rule book clearly states 36.5. I know someone else had to have told you guys to allow this but do not want to assume who it was.

Thanks
EA


Half of the field would have been tossed using the 36.5 number so who messed up here, Roar with bad numbers or Novak with terrible QC?


Well I know how ROAR came up with the 36.5 number when making the rules and it was more than fair on the samples they received. So I would figure it was Novak with a change in the way they are making or winding the motors.

As for it being chaged mid race or begining of the race (if it indeed was) is wrong. I know guys who have spent a lot of time this summer getting the closest motors they could to 36.5. I know at the On-Road nats we were not allowed to run anything below that. I had an LRP that was 36.4 one 1 pole and was told it was NOT legal to pre-tech. Several others were told the same thing as well.

EA


The resistance numbers posted on Roar's web page, as with all rules, constantly need updating as technology and knowledge changes each day. If we used the number on the Roar site, 86+ percent of the motors would have been disallowed to race (41 out of 48). Would have this been fair? A shortage of motors with the posted inductance would have occurred and the consequences would have been tremendously severe post race with racers not even being able to race with their box stock off the shelf motor.

Several motors were new from the hobby shop so this is a concern and this will need to be amended for the future. Tech at the Nationals last weekend was extremely successful, with no issues or protests at the event for 17.5. TQ cars were constantly tore down after heats and timing modifications were also checked throughout the weekend.


now i'm not sure but me thinks since the inception of novak motors each passing week the min # of inductance was lower and lower and lower....

and if you think "all" of your motors are tested and run the same you realy are kidding yourself..

I myself had a mis marked (NIP) 10.5 turn out to be an 8.5
another racer in florida owns (still owns) a 21.5 that is a 17.5 again mis marked
and most of the toplevel racers know if you get lucky you will get a novak motor that runs like a raped ape..it may be 1 out of 500 but man you can dominate with that motor for awhile...

and if you don't believe me ask danny B
and yes i'm sure most if not all brushless manufacturers have good and bad days as well..

let's just say alot of lumps in the oatmeal have been hashed out over the last 2 years and more still to come.

and yes now it takes a 400.00 meter to properly tech a brushless motor
this is on top of the 200.00 race directors dumped on a inductance meter a year or two ago...

that kinda hurts

and as you see there is still alot of confusion on exactly what number to look for and what meter to use to find it.

my question is this.....

WHY DO ALL THE 10.5 21.5 AND 17.5 MOTORS ALL HAVE A DIFFERENT NUMBER TO BE LEGAL?

why isn't every 17.5 a certain number and if your under it's ilegal to use?
same goes for 21.5 and 10.5 motors why is a lrp number set differently from a hacker or novak?

this may have been answered before?

Here are some thoughts on this.... One issue I can see brewing with motor winds right now is giving a set minimum value for legality. You can have an ‘out of the box’ ‘right from the hobby shop’ motor not legal according to these minimums being set (as was found at our race and other races unfortunately). What is a racer to do if he/she bought a legal motor that is not legal for racing? What we found last weekend is that meters can read all over the place. We had five meters at the ‘birds and two were fairly new BK meters, and all read more than a point apart. We couldn’t get each meter to read exactly the same when checking the same motors. So when motors are flirting with a minimum number this can be an issue. One thing we did that worked great was a having a test motor that we could go back to every day, at different times, with fresh and old batteries, to get verifiable confidence the meter was accurate. It is very easy to calibrate meters so we set a backup meter based on this. Was our meter perfect? Not sure (and not sure there can be a perfect meter). For the 21.5 class we choose a higher range and it seemed to be the best move for this race. Most everyone had motors above the 53 minimum, but only a few would have some lower. We did see legal brand new motors under 53, and under 140 double pole (but stuck with a higher legal limit). We did have a list of a couple hundred 21.5 numbers from the Nats and other races so we felt good with this number. But as mentioned, some of the new batches of motors are coming in a bit lower and tracks might have to reset their minimum to allow them. We can’t be turning away new motors, can we? But having data from hundreds of motors from each brand and each wind might be next to impossible. The main thing with tech I see is making sure motors are what they are advertised as (10.5, 13.5, etc). Roar helped us out with a set of numbers for each brand of motor and each wind, and also a number from motors that had one wind removed. This was crucial in helping us know if ‘motor brand X’ was on par with this range of findings. If racers remove a wind or a motor is mis-marked, it will show up without a doubt. Looking at the Roar ranges of motors though you will see a huge range of inductance numbers for the same wind with different brands. This is confusing for some for sure, and where some future problems may arise. Different materials, rings, solder, wire gauge etc make different numbers. I know there is a talk of checking with resistance and this might eliminate having to remove a rotor to check (but we still have to check rotors are spec and not modified). Also a big part of tech is looking to see if a motor is not tampered with and original from factory. This is fairly easy to do. I know more and more are playing around with unwinding some motors but reassembling them to factory specs is still hard. It would be awesome if somehow each manufacturer had a dye they could use in their last solder process on the rings that was 100 percent identifiable and could not be reproduced, or even a branding of some sort that was in the solder. This could help end doubt somewhat. Inductance numbers was never brought out with brushed motor days, and I am sure it was checked. There were just good ones and mediocre ones. Kinda what some racers are finding now looking for the lowest possible inductance. But the verdict is still out what all this means, as we saw fast runs with different ranges at the ‘birds with a top racer, where he went the fastest with a motor two points higher than his lowest.

It would be great if a company could sell an inductance tester that was standardized so each track could calibrate their meters to that maybe? Something small simple that was the same from piece to piece.. not sure it can be done... just a thought.

I am forwarding your motor tech comments to Bob and Adnan. Steve, also, but he was there so is probably aware of your testing procedures.

LOL.. I was just looking for some advise on a meter to purchase for myself to verify my stuff and to have at my disposal a meter to check other windings as well.

So if anyone else has advise on what brand,model number etc... man some of you guy's read into a simple qustion and it turns into more than it needs to be but that's usually the case. Thanks again to the few that actually lent some help.

mike boylan just made his longest post ever! and with very good iinformation.

koz at the very least you can go on what mike just said..it is good information.

Boylan's POST Broken up for easier reading!

Here are some thoughts on this....

One issue I can see brewing with motor winds right now is giving a set minimum value for legality.

You can have an ‘out of the box’ ‘right from the hobby shop’ motor not legal according to these minimums being set (as was found at our race and other races unfortunately). What is a racer to do if he/she bought a legal motor that is not legal for racing?

What we found last weekend is that meters can read all over the place. We had five meters at the ‘birds and two were fairly new BK meters, and all read more than a point apart.

We couldn’t get each meter to read exactly the same when checking the same motors.

So when motors are flirting with a minimum number this can be an issue.

One thing we did that worked great was a having a test motor that we could go back to every day, at different times, with fresh and old batteries, to get verifiable confidence the meter was accurate. It is very easy to calibrate meters so we set a backup meter based on this.

Was our meter perfect? Not sure (and not sure there can be a perfect meter). For the 21.5 class we choose a higher range and it seemed to be the best move for this race. Most everyone had motors above the 53 minimum, but only a few would have some lower. We did see legal brand new motors under 53, and under 140 double pole (but stuck with a higher legal limit). We did have a list of a couple hundred 21.5 numbers from the Nats and other races so we felt good with this number. But as mentioned, some of the new batches of motors are coming in a bit lower and tracks might have to reset their minimum to allow them.

We can’t be turning away new motors, can we? But having data from hundreds of motors from each brand and each wind might be next to impossible.

The main thing with tech I see is making sure motors are what they are advertised as (10.5, 13.5, etc). Roar helped us out with a set of numbers for each brand of motor and each wind, and also a number from motors that had one wind removed. This was crucial in helping us know if ‘motor brand X’ was on par with this range of findings. If racers remove a wind or a motor is mis-marked, it will show up without a doubt. Looking at the Roar ranges of motors though you will see a huge range of inductance numbers for the same wind with different brands.

This is confusing for some for sure, and where some future problems may arise. Different materials, rings, solder, wire gauge etc make different numbers. I know there is a talk of checking with resistance and this might eliminate having to remove a rotor to check (but we still have to check rotors are spec and not modified). Also a big part of tech is looking to see if a motor is not tampered with and original from factory.

This is fairly easy to do. I know more and more are playing around with unwinding some motors but reassembling them to factory specs is still hard. It would be awesome if somehow each manufacturer had a dye they could use in their last solder process on the rings that was 100 percent identifiable and could not be reproduced, or even a branding of some sort that was in the solder. This could help end doubt somewhat. Inductance numbers was never brought out with brushed motor days, and I am sure it was checked.

There were just good ones and mediocre ones. Kinda what some racers are finding now looking for the lowest possible inductance. But the verdict is still out what all this means, as we saw fast runs with different ranges at the ‘birds with a top racer, where he went the fastest with a motor two points higher than his lowest.

.....

Mike, were there any random motors being pulled or checked during qualifying? If so what were the findings on them? In a thread which was I think for Paved Oval Nats (could be wrong) the numbers that were given for 21.5 were a 50 for each poll and you used 53 as the number. So if there were motors that showed up at that race that around 50 it would be safe to say that they would not have been legal at the birds. But since the numbers weren't posted for this class until the race week the low number motors would have been present and could have been used if someone wanted to try and get away with it. At the Oval Masters race motors needed to be submitted to tech before racing and then a sticker was applied to them. Although not the perfect solution but something. Would that sort of system not have been good for the biggest oval race of the year. I'm not knocking what you and your crew did, the race ran very well and qualifying was very close. I think you gave out 59 lap runs to almost every 21.5 racer on Friday so if a lower inductance number was worth the little extra then that would have been the situation to want a little extra and move up a coulple of spots.

FYI: Buddy and I noticed the meter at the 'Birds tech area didn't zero out properly when shorting out the aligator clips. It was 0.6 off. I noticed that this was the same amount it showed lowered than it should. My BK Pro meter tested the same motors 0.6 higher. (My BK Pro has an adjuster dial that allows you to zero it out.)

I bought a new 21.5 from the hobby shop that I couldn't use because it failed on the 'Birds tech meter, even though it passed on my BK Pro meter. (One pole measured 52.8 in tech, but measured 53.4 on my meter.) In the future, I recommend using a meter in tech that has the option to zero out.

FYI: Buddy and I noticed the meter at the 'Birds tech area didn't zero out properly when shorting out the aligator clips. It was 0.6 off. I noticed that this was the same amount it showed lowered than it should. My BK Pro meter tested the same motors 0.6 higher. (My BK Pro has an adjuster dial that allows you to zero it out.)

I bought a new 21.5 from the hobby shop that I couldn't use because it failed on the 'Birds tech meter, even though it passed on my BK Pro meter. (One pole measured 52.8 in tech, but measured 53.4 on my meter.) In the future, I recommend using a meter in tech that has the option to zero out.

I agree! BK should be the standard.

I do know that the BK is the meter that a few of the manf use as their standard. I hope I am not mistaken but I believe some of the BK meters have a self cal that needs to be preformed before use not every time but at least once a day.

Good points guys. We ended up just using the normal one we have used weekly because we were used to it... but having BKs for all races might work too. I am confident the numbers were good for the race though. We had most 21.5's come in around 54-55... and several new ones were this way. But a few new ones were also under 53, around 52. Tough yes... and I hate some new motors came in low. I am sure the number will have to be lowered at future races now if the majority of new motors are coming in a little lower. We thought about pre-tech but with so many entries we didn't think it could be done efficiently and effectively. Brushless and LiPo are evolving fast so I am sure by next year things will be different and a whole new ball game. I was with Paul Schaub tonight and we unwound some suspicious motors we kept that indeed were 1 wind less (20.5 and 16.5) and the inductance showed.... so we were happy in the numbers. I am also kinda curious (and I know others are too) what tracks around the country are doing for number limits for the rest of the winter and into spring, and if anyone is doing tech at tracks please post your number limits and any findings, etc. Thanks!!! cya

Mike what range were you using with the BK meter? We have been using 200 micro henries and measuring from pole to pole and getting readings anywhere from 140 to 154. It seems the older motors have the lower numbers but the new motors seem to have much better rotors.

just curious Mike what were the readings on the motors that were a wind off?

I don't have the numbers with me here... Cliff, seems 140 is still the norm for double pole checking. BK's I have seen read a little higher checking double pole, but doing single pole most meters are closer in range to each other. I think Roar is doing testing on 21.5's now so it will be interesting to see what they publish for motors. I am off to Daytona. Go Smoke and JR!

Thanks MIke