Revolt RV-series motor review and comparisons

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madin88   100 MW

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Re: Revolt RV-series motor review and comparisons

Post by madin88 » Jul 10 2018 4:40am

ElectricGod wrote:
Jul 09 2018 3:17pm
I can check RPM with my laser tacho at a 66 and 82 volts.
If you have a CA you could program it to show you the RPM in tenth instead of the speed.
You would need to set the wheel circumfernce to 1666 or something like that, but better check the manual or CA thread.
Just for clarity, what's no load current?
Measure the current it draws at WOT without any load at two differnt voltages like 10s and 20s battery.
Write down the exact voltage so you can calculate the Watts later with the Amps you measure.

I think the maximum no load consumption for this motor will be around 300W. This tells you max usable RPM.

btw: what controller are you using?
ElectricGod wrote:
Jul 09 2018 11:35pm
Checked a few things.

Phase resistance: 57.6-57.7 mOhms.

Inductance: .2 to .21 uH

I doubt that a phase is wound incorrectly with that small of a difference.
Yes that can be called as consistent wound.
Whats the kV?
The sale version is 57kV (no other windings to choose), but this could have been different when you bought yours..
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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 10 2018 12:02pm

madin88 wrote:
Jul 10 2018 4:40am

Measure the current it draws at WOT without any load at two different voltages like 10s and 20s battery.
Write down the exact voltage so you can calculate the Watts later with the Amps you measure.

I think the maximum no load consumption for this motor will be around 300W. This tells you max usable RPM.

btw: what controller are you using?

Yes that can be called as consistent wound.
Whats the kV?
The sale version is 57kV (no other windings to choose), but this could have been different when you bought yours..
I can do that. For bench testing I built a rig that lets me precharge and includes a watt meter for controller testing. I'll test at 66 volts and 82 volts and let you know amps at WOT.

I'll be using a PowerVelocity 12 fet controller I am modding for a friend.

I think my motor is the 57Kv version, but I'm not entirely sure. I can check it with my tacho once I add halls to it and spin it up.

How does the no load watts tell you the max usable RPM? Motor theory is not exactly my strong suite.
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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 10 2018 12:08pm

Found a better hall option...why grind a wider slot in the stator teeth when you can use SMT halls instead that will fit in the gap as is!

I'll have to find the appropriate part that duplicates the SS41F, but that won't be hard...and of course NOT buy from ebay.

https://www.ebay.com/itm/1PCS-SS511AT-S ... SwhkRWb4lY
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SMD halls

Post by ElectricGod » Jul 10 2018 12:34pm

I think any of these will work in place of the SS41F. What do you think?

https://www.digikey.com/product-detail/ ... ND/3045883
https://www.digikey.com/product-detail/ ... ND/3045884
https://www.digikey.com/product-detail/ ... ND/5253443
https://www.digikey.com/product-detail/ ... ND/5253457

And of course the SS41F...for comparison.
https://www.digikey.com/products/en?keywords=ss41f

I was surprised I didn't find a direct replacement for the SS41F from Honeywell in SMD.
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Re: Revolt RV-series motor review and comparisons

Post by madin88 » Jul 10 2018 1:17pm

ElectricGod wrote:
Jul 10 2018 12:02pm
How does the no load watts tell you the max usable RPM? Motor theory is not exactly my strong suite.
The higher the RPM, the higher the no-load Watts.
Above a given point the motor will just overheat without any load because it cannot shed the heat anymore which is coming from eaddy current and hysteresis losses.
You want to stay below that point (RPM).
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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 10 2018 3:38pm

madin88 wrote:
Jul 10 2018 1:17pm
ElectricGod wrote:
Jul 10 2018 12:02pm
How does the no load watts tell you the max usable RPM? Motor theory is not exactly my strong suite.
The higher the RPM, the higher the no-load Watts.
Above a given point the motor will just overheat without any load because it cannot shed the heat anymore which is coming from eaddy current and hysteresis losses.
You want to stay below that point (RPM).
Oh of course...I already knew that, but thanks for explaining. I didn't realize that was what you were referring to.

BTW...I can run at a maximum of 32S or 131 volts. I have a controller that's good up to 150 volts. Sounds like I should try 16S, 20S, 24S, 28S and 32S and see what happens. Find that sweet spot! My bench battery pack is made of 8 4S LIPO packs and I can tap into it at each of those 4S connections. At some point we will see heat building up. I've done this test on an HLD inrunner. 82 volts was great. 100 volts was OK, but the motor warmed up to about 90F in a 70F room. 131 volts was a bad idea. The motor temps were climbing well above 120F within a minute or 2 of running.

Before I can do this test, I need to add halls to it.
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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 10 2018 7:32pm

I bought some SMD halls from mouser.

AH175-WG-7-B

They are not quite exactly like a 41F, but close enough that it shouldn't matter.
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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 11 2018 1:32pm

larsb wrote:
Jul 11 2018 10:38am
The main problem killing my Revolt motor was eddy losses in the rotor. I guess the magnets aren't electrically isolated from each other and the back iron ring, also it looks like there's metal foil between the magnets.

I see something similar on the pics of your motor. When a rotor is built like that it surely is not for performance..
Are you saying that gaps between the magnets is better? That the magnets conduct between each other? I have some very high end hub motors build just like this. The magnets touch.

This is a mini hub monster. It looks like there are gaps, but that is just at the rounded corners of the magnets. Inside they touch.

Image
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Re: Revolt RV-series motor review and comparisons

Post by larsb » Jul 11 2018 2:40pm

Touching and conducting is not the same thing so the hubmonster and similar motors can still be good. The larger the low resistance current path, the more eddy losses so conduction between magnets is bad and conduction towards backiron is bad.

I think the optimum for efficiency is not touching but slightly less magnet coverage (=gaps). I guess this is due to less agressive flux change when magnets are spaced out.

Segmentation of magnets is done to lower eddy heating and losses in magnets. You could google "joule loss magnet segmentation" or "eddy loss magnets" - you'll find plenty of hits.

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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 11 2018 3:23pm

larsb wrote:
Jul 11 2018 2:40pm
Touching and conducting is not the same thing so the hubmonster and similar motors can still be good. The larger the low resistance current path, the more eddy losses so conduction between magnets is bad and conduction towards backiron is bad.

I think the optimum for efficiency is not touching but slightly less magnet coverage (=gaps). I guess this is due to less agressive flux change when magnets are spaced out.

Segmentation of magnets is done to lower eddy heating and losses in magnets. You could google "joule loss magnet segmentation" or "eddy loss magnets" - you'll find plenty of hits.
You may be right that there's some kind of thin insulator between the magnets in the mini hubmonster. I don't know if there is or isn't. Wouldn't gaps between the magnets also need to have the magnets insulated from the rotor iron as well?

Thinking about this more, I have quite a few inrunners and I don't think anything like that exists. The magnets are in electrical contact with the rotor iron. I have several outrunners that are bare metal inside and the magnets are glued to it. There's no guarantee that they are insulated either. Lots of outrunners use metal spacers between the magnet ends. The magnets have direct electrical contact through multiple sources. This would be no different than grinding a slot in the lamination's so they were shorted together...if the effect is the same. I'm guessing the magnet losses is not as great since it's not addressed in any motor I've ever taken apart. I'm certainly not an expert on this, but I have something like 15 motors and taken them all apart at least once. I don't remember seeing some way that electrically isolates the magnets from each other.

This probably the most expensive motor I have...AstroFlight 3220. The magnets are glued down to the iron core and then these aluminum caps are clamped down on either end. Lots of possible electrical contact and no evidence of insulation.

Image

I'll have a Motenergy ME-1202 in a few days. It's radial and dual stators. I'm curious if those magnets are isolated?
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Re: Revolt RV-series motor review and comparisons

Post by larsb » Jul 11 2018 4:06pm

Interesting.. Are the magnets segmented in those motors? How many magnets for each pole?
It only takes insulating glue or a layer of varnish to sink the conduction.

Should be possible to measure the actual resistance and compare. I can try it on my rotor.

My Revolt motor gets hotter rotor than stator most of the time. Normally the largest losses are copper losses in an ok motor so something's wrong.

Same reported in this video for rv-160 pro:
https://youtu.be/6whYU1mLjlU

The rotor design is not good. If it's the magnets or backiron type or conduction.. It's hard to tell but for sure losses are where the temps are high.

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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 12 2018 12:01pm

larsb wrote:
Jul 11 2018 4:06pm
Interesting.. Are the magnets segmented in those motors? How many magnets for each pole?
It only takes insulating glue or a layer of varnish to sink the conduction.

Should be possible to measure the actual resistance and compare. I can try it on my rotor.

My Revolt motor gets hotter rotor than stator most of the time. Normally the largest losses are copper losses in an ok motor so something's wrong.

Same reported in this video for rv-160 pro:
https://youtu.be/6whYU1mLjlU

The rotor design is not good. If it's the magnets or backiron type or conduction.. It's hard to tell but for sure losses are where the temps are high.
I wish I had a picture of the armature of my 3220. It's not like I haven't pulled it out a few times. it's a 4 pole armature (8 magnets) and they are held in place with eopxy and they butt up against each other. It's possible there's a thin layer of epoxy between the magnets, but that's no guarantee there's not an electrical path as well. I'd have to pull an armature, take some close-up pics and test on a meter to be sure.

I have an idea for the Revolt motors. If current flow through the magnets is a significant concern, then I bet I can remove the magnets. They are only glued in place and I bet a solvent of some kind will release the glue or epoxy. It's not ideal since magnets are machined before they are magnetized, but I could grind or sand 1mm off each one. Water flow will keep the magnets cool. That will "fix" any issues here. Once the chrome is removed, the magnets will oxidize on any exposed surface, but I intend to coat the stator and interior of the armature in electrical paint anyway.

On my C80100, which has 2-4mm gaps between the magnets, the stator is the hot spot and the armature seems to only be warm from radiated heat. Maybe those gaps really are important after all!

I'll probably be using JB weld to re-mount the magnets. It's not conductive despite having metal in it. I doubt the metal in it will make much magnetic difference either. Maybe some other epoxy option? any ideas? I'm not married to JB weld, but it is cheap and holds up at pretty high temps.

What do you think would release the magnets from the bell?
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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 12 2018 12:10pm

I just googled for "astroflight 3220" and looked at pictures. I was surprised at how many of them were mine. I guess google knows me too well! Didn't see any of the armature removed.
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Re: Revolt RV-series motor review and comparisons

Post by larsb » Jul 12 2018 12:50pm

Actually JB weld IS conducting no matter what they say. I found a test that was performed with two separated/glued plates that did conduct after the hardening.

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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 12 2018 1:36pm

larsb wrote:
Jul 12 2018 12:50pm
Actually JB weld IS conducting no matter what they say. I found a test that was performed with two separated/glued plates that did conduct after the hardening.
Sometime back I put my DMM on some cured JB weld, there was some resistance, but it was like 1 megohm. THat's pretty negligible. The black part (steel) is the conducting portion and it's only something like 20% metal. Then you mix that with the white part (hardener) in a 50/50 mix. Not much metal gets to make contact after that, but I suppose it depends on the amount of the "Steel" component you add.

That would be an interesting test...and I don't care about sacrificing some JB weld.
1. Put a 1/2" diameter blob of "steel" on a non-conducting surface.
2. Measure it's resistance.
3. Add a 1/2" blob of hardener on a non-conducting surface.
4. Measure it's resistance.
5. Mix them together.
6. Measure the resistance.

I'll see about doing this tonight...if I remember.

Also JB weld has MarineWeld. The black tube is called resin not steel. I wonder if it's still metallic?
I bought some MarineWeld...will know soon enough.
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Re: Revolt RV-series motor review and comparisons

Post by larsb » Jul 12 2018 2:36pm

If you repeat same test then take two metal plates, glue with thin layer of glue and measure between them. This is a normal joint so is more representative. I wouldn't use JB. Why take a chance?

But the most interesting test is if the motor works :)

What is no load A?
Will it function like it should?

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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 12 2018 4:37pm

larsb wrote:
Jul 12 2018 2:36pm
If you repeat same test then take two metal plates, glue with thin layer of glue and measure between them. This is a normal joint so is more representative. I wouldn't use JB. Why take a chance?

But the most interesting test is if the motor works :)

What is no load A?
Will it function like it should?
IF JB is non-conductive, then it's not a problem.

I'm waiting till I get halls in place before doing any testing. I replaced the shielded bearings already. Halls are the last thing for now. I bought some SMD halls so I don't have to grind out a spot in the stators. Looks like they will arrive tomorrow.
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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 12 2018 10:12pm

Afew more pictures and I measured the resistance between adjacent magnets and it just a few ohms. So much for electrical isolation between magnets. They are held in place by some kind of hard clear glue or epoxy.

When I took the motor apart, I discovered it had only one key between the shaft and the bell top. I bought keys in multiple sizes and lengths and put in the longest ones the shaft keyways can take.

Image

The magnets are all touching each other. It looks like they were all placed inside the cylinder and are slightly too small for the ID. I don't know what this white junk is between the magnets. Maybe it is some poor attempt at electrically isolating them? If so, then a thin strip of plastic would have worked far better.

Image

There is this single gap that's wider than all the rest of them.

Image
Image
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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 12 2018 10:14pm

Halls arrive tomorrow so I'll be able to close up the motor and test it out after that.
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JB Weld test

Post by ElectricGod » Jul 12 2018 11:44pm

If anyone cares...

Regular JB weld and JB kwik both contain iron and are attracted to magnets. They are NOT conductive below 10 meg ohms.

JB's MarineWeld does NOT contain any ferrous materials and is not attracted to magnets. It is also NOT conductive below 10 meg ohms.

AKA...MarineWeld will make a good option for mounting things in a motor.
Last edited by ElectricGod on Jul 27 2018 11:24am, edited 1 time in total.
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Marine JB Weld

Post by ElectricGod » Jul 16 2018 12:33pm

JB MarineWeld works for uses in motors.
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Regular JB Weld and MarineWeld

Post by ElectricGod » Jul 16 2018 7:26pm

JB MarineWeld works for uses in motors.
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MarineWeld

Post by ElectricGod » Jul 16 2018 11:32pm

JB MarineWeld works for uses in motors.
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Re: Revolt RV-series motor review and comparisons

Post by Miles » Jul 27 2018 2:44am

Topic split to here: viewtopic.php?f=30&t=95487

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Re: Revolt RV-series motor review and comparisons

Post by ElectricGod » Jul 27 2018 11:26am

Miles wrote:
Jul 27 2018 2:44am
Topic split to here: viewtopic.php?f=30&t=95487
Thank you Miles!
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