12 kw rc motor
- Thread starter markobetti
- Start date
liveforphysics
100 TW
Arlo1 said:Just a little secret I'll let you in on thats the 9th time I've ever used a lathe lol.liveforphysics said:Kick ass! That bearing is going to be super low drag.Nice work!
You did a great job!
How does the bearing feel to spin by hand now?
markobetti
10 kW
- Joined
- Jul 16, 2009
- Messages
- 620
Great work , hope its stiff enough. liveforphysics, Arlo , Yesterday was holiday here so no possibility for me to send it. So monday, i promise .
Thud
1 MW
Arlo,
I love what you have done here. (did luke put you up to it LOL). either way good job. So far I am coming to hate that power robbing skirt bearing. This looks great. I am off to order some loose ceramic ballz now :lol:
I love what you have done here. (did luke put you up to it LOL). either way good job. So far I am coming to hate that power robbing skirt bearing. This looks great. I am off to order some loose ceramic ballz now :lol:
Feels about the same as before I think it might need to wear in a bit.liveforphysics said:Arlo1 said:Just a little secret I'll let you in on thats the 9th time I've ever used a lathe lol.liveforphysics said:Kick ass! That bearing is going to be super low drag.
You did a great job!
How does the bearing feel to spin by hand now?
Haha Luke and I are a team. I have another idea for a retainer I will build if this one gives any issues!Thud said:
As for the balls get them from a known good place there is no point cheeping out on them because good ceramic balls will only need 6-18 to replace the steal balls and there is very little load on them.
olaf-lampe
10 kW
Arlo1 said:
I know there is a significant weight difference between the ceramic and steel balls, but would it help to reduce the number of steel balls instead of exchange them? Would it be possible to remove some steel balls without destroying the original ball retainer?
Would that be an option for those without a lathe and teflon?
Olaf
liveforphysics
100 TW
Ceramic balls are a hell of a lot harder than the best steel balls, they can't gall on the surfaces so lubricate becomes negligable (further reducing drag and heating), and for a given RPM, they have a lot less pressure against them on the race due to the lower mass.
When the cost is like $0.10-0.20 per ball (or whatever deal you find), I can't see how it would make sense not to get ceramic balls.
When the cost is like $0.10-0.20 per ball (or whatever deal you find), I can't see how it would make sense not to get ceramic balls.
Thud
1 MW
Ceramic ballz are the shiz for a 50k rpm gyroscope.......
After my bench testing the last couple days I am more concered with ultimate iron loss issues. My smaller 80/100-180s just don't like to spin more than 8-10k without starting a nasty spike in amp draw & unloaded heating. (no real data on the heating other than fingers ) I have not even begun to play with my CA120 motor yet. But reading the data sheets & seeing the issues a few others are having....I suspect we have found the limiting factors for "continuouse" ratings on HoBo's.
I guess you know best where your line of "diminising returns" is. I would really like to see where this leads ultimately. these are phenominal motors & I love seeing whats going on to get them into that last 1% of their potential.
After my bench testing the last couple days I am more concered with ultimate iron loss issues. My smaller 80/100-180s just don't like to spin more than 8-10k without starting a nasty spike in amp draw & unloaded heating. (no real data on the heating other than fingers
) I have not even begun to play with my CA120 motor yet. But reading the data sheets & seeing the issues a few others are having....I suspect we have found the limiting factors for "continuouse" ratings on HoBo's. I guess you know best where your line of "diminising returns" is. I would really like to see where this leads ultimately. these are phenominal motors & I love seeing whats going on to get them into that last 1% of their potential.
olaf-lampe
10 kW
liveforphysics said:
If I could replace the balls without destroying the original retainer it's a no brainer off course...
But a complete new ceramic bearing is how much?
-Olaf
I could not find a compleat bearing with ceramic balls in this size. So... And a good bearing with steal balls is $50-150 so that would meen you can add at least 100 to that!
The retainer is impossible to take a part with out destroying it because it's rivited together.
The price you will find for ceramic balls is ~$1 a ball and you won't need 31 like it originally had.
The retainer is impossible to take a part with out destroying it because it's rivited together.
The price you will find for ceramic balls is ~$1 a ball and you won't need 31 like it originally had.
liveforphysics
100 TW
I actually found that bearing in full ceramic. It was $540usd. I can't remember who even sold it though... I don't think it was VBX or Bocca...
Ok so i just went to test the collossus again with my 18 fet and blew 6 fets!
Come on marko get that stuff shiped so i can build a real controler!
Im going to hook 3 monster fets to it and use the signal out put to run it tonight I will have a running motor or a fireball but I will not give up either way Im walking home so I midays well make it worth my while!
Come on marko get that stuff shiped so i can build a real controler!
Im going to hook 3 monster fets to it and use the signal out put to run it tonight I will have a running motor or a fireball but I will not give up either way Im walking home so I midays well make it worth my while!
liveforphysics
100 TW
Make sure you either start out at lower voltages, or that you fit a boatload of those caps I gave you on those fets. It would be a shame to nuke them over a little ripple/spike.
All I got left is to run the signal wires and mount the caps and im done but im not too worried about the fets Im thinking the controler is going to give!liveforphysics said:
A wise man once said "all controlers are evil and must be punnished to there death"
liveforphysics
100 TW
I'm not worried in the least about over-current on the FETs (wow, it's weird to say that), but if you are running at say 95v pack voltage, and you get a swing of 10v ripple, it could nuke the FET over just stupid over-voltage across DS, which would be an extremely lame way to kill FETs that should be otherwise unkillable (unless they shoot-through...)
liveforphysics
100 TW
Arlo1 said:
That was a really smart thing to do.
Good call. Thud said:Ceramic ballz are the shiz for a 50k rpm gyroscope.......
After my bench testing the last couple days I am more concered with ultimate iron loss issues. My smaller 80/100-180s just don't like to spin more than 8-10k without starting a nasty spike in amp draw & unloaded heating. (no real data on the heating other than fingers
yes, i agree -heres what i found from testing the std turnigy 80-100-180kv motor skirt bearing at 7000rpm:
standard as delivered: 86w used at 20deg c, after 2 mins the grease heats it up to about 60degc and the loss drops to 45.3w.
clean it out, and run mobil 1 10w-30 engine oil (not too much though) and it drops to 15.4w (agian after 3mins of running to throw off the excess)
clean it out, and run wd-40(and plenty of it), and even with the steel covers on, so it stays there, only 3.4w lost! -straight away, and it now free spins for bloody ages after, almost frictionless.
put simply they put grease in bearings std for high loads and long life without further lubing, but at very high rpm grease becomes concrete, gets hot etc.
i know ceramic balls are better for high rpm, but if your pressed for time then i just dont think the 3.4w lost is the big player here, its the iron loss..
the pdf is a graph of the watts lost from a turnigy 80-100 motor from 0 to 11000 rpm at idle (cos the magnet cycle speed is what matters, 11000 on this curve is like under 7000 rpm for the collosus) and clearly this is not a happy place to be (850w lost on the turnigy and about 2000-3000w lost on the collosus)
i know the turnigy got scalding hot (even the magnets themselves from eddy currents??) within 5 seconds so im keen to see what people find here with the collosus -the bigger 120 black turnigy looks to get ugly a bit early at around 5000+ cos its got 24 magnets?
so these can all still be hugely impressive motors if we work on getting them up and running properly in their happy range.
Hillhater
100 TW
I hope the WD40 was just an experiment and not a suggestion for long term use ?
WD40 has no lubricating properties at all ! .... you may as well run the bearing dry.
a few drops of auto trans fluid might be a better substitute.
WD40 has no lubricating properties at all ! .... you may as well run the bearing dry.
a few drops of auto trans fluid might be a better substitute.
AussieJester
1 TW
Hillhater said:
"no lubricating properties at all"
Direct from Wd40 website
"WD-40 protects metal from rust and corrosion, penetrates stuck parts, displaces moisture, and lubricates just about anything. WD-40 is also great when it comes to cleaning grease, grime and other marks from most surfaces."
http://www.wd40.com.au/wd40/index.php
Depending who you believe 15% of WD40 is mineral oil, either way i'm positive its a shit load better than running bearings dry as you suggest.
KiM
liveforphysics
100 TW
On the note of running dry, many ceramic bearings I've bought actually have a sticker on the bags they come shipped in that says "dry bearing operation only, do not lubricate"
With a steel bearing, just any film that prevents the steel balls from chaffing to steel races is the important thing. It's not like this skirt bearing is under any load, it's simply to prevent the magnets from crashing into the stator in the event the motor takes a big bump while spinning.
With a steel bearing, just any film that prevents the steel balls from chaffing to steel races is the important thing. It's not like this skirt bearing is under any load, it's simply to prevent the magnets from crashing into the stator in the event the motor takes a big bump while spinning.
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