VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss)

Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby Votan » Sat Aug 01, 2020 6:14 am

Golear, I would really have fun with you, if I did not know that what you are writing is an attempt to show devotion and subordination, expecting who knows (although I imagine) what.
When will you finally realize that we are not interested in either Bill's quarrels with Harry (and vice versa through you), or in most of your ready-made answers in this issue, that are full of jumbo theories sprinkled with plenty of slander?
And also, when will you finally realize that what matters in the end, is the motor to be as quiet and less vibrant as possible with the best possible speed stability in exact 33,33 rpm, plus long term maintenance free with sturdy construction?
And finally and most of all, that what matters is its sonic result in MY OWN setup?
So, bad news for you (ones more!): We (with Total Eclipse Package-Condor motor) already know that, because we are experiencing it. End of the story._
P.S. Concerning the total analog ADS, in my setup at least, it was sonically inferior to my (...digital) SDS that (unfortunately) replaced.
Don't you concern about the so many years of anxious questions of many forum members about when the new, long-awaited ADS will be released? Add now and a new motor....
So I think it is time for VPI, instead of underestimating, or stoning the competition, to overcome it! I'm sure they can ...
Prime Sign/10"3DR/Finite Element(FE) platform/SOTA's Total Eclipse/Lyra Titan/VPI Ring/WW Silver Eclipse 8 Ph.C/Groove+ SRX MkII Ph. St./Moon 740 Pre/Moon 820 PSU/ATC 100 Active Speakers/AQ Niagara IC/WW Silver Electra AC,FE Ref Rack/RPG Room Treatm.
User avatar
Votan
Senior Member
 
Posts: 378
Joined: Sun Dec 02, 2018 4:59 pm
Location: Greece, Larisa.

Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby vienna acoustics » Sat Aug 01, 2020 1:33 pm

You nailed it Michael.
And just to clear this all analogue illusion, the highly appraised HW40 DD is not a only using a BLDC motor too, but also digital circuits, to control the speed, like all the direct drives (except Brinkmann dds) in the market right now. Which is an absolutely right approach in order for them, to offer high torque and accurate spot on speed at 33.333 amd 45.000 rpm! However this should be also applied to their belt and rim driven tts.
Obviously HW is opposed to this design and I would like to read his clear position for this.
!
vienna acoustics
Senior Member
 
Posts: 486
Joined: Mon Apr 09, 2018 10:07 pm

Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby Golear » Sun Aug 02, 2020 12:12 pm

By the way, we should, of course, look at the entire implementation. The SOTA motor is dynamically balanced, has less play in the bearings, and the body is more rigid, the whole package has less vibration/noise. As for (possible) torque cogging, it looks like it is extremely well managed.

I wonder if whoever makes the motor for SOTA has a version that runs off the mains.... May be the only part that needs to change is... the windings?
Golear
Senior Member
 
Posts: 479
Joined: Wed Nov 30, 2016 4:51 pm

Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby theeng » Sun Aug 02, 2020 2:56 pm

Golear,

There is nothing exotic about the SOTA BLDC motor - its mostly an off the shelf design - https://www.anaheimautomation.com/produ ... 96&cID=22; and by all measure pretty inexpensive. The use of two ball bearings is likely driven by the motor's likely rated speed >>1000rpm. No mention is made of the ball bearing quality; but given the low cost, they are unlikely to be ABEC-3 or 5. Also, given the cost, I am not sure how they can 'dynamically' balance all rotors - that is very labor intensive and given the very low mass, not sure of benefit - there are many grades - read ISO 1940 or API 610.

The item SOTA needs to be careful with motor pods (VPI replacement) is heat. Yes, its higher torque than the Hurst http://hurst-motors.com/papbdirectdrive.html, but it can draw a lot more power (watts), and running it at low rpm likely trades motor efficiency; and for 3-phase BLDC motors, the speed control has 'tuning' parameters that have to be optimized otherwise, the motor can run very hot (shortening life), as has been reported here; and this is dependent on the 'rare earth' permanent magnet magnetic properties - and specifically Br (residual flux density) which also dictates back-EMF.

The stator windings for the SOTA motor and the VPI Hurst are Class B - rated 130C, and for every 10C less that the stator operates - the motor life doubles. The Hurst motor draws 7-10 watts, so overheat in the motor pod is very limited risk. The BLDC motor that VPI used in the HW-40 has the motor housing mostly open to air - https://www.vpiindustries.com/single-po ... hite-Paper, so VPI was likely sensitive to the heat issue. FYI - always remember that when in a motor-pod, air is a thermal insulator - if the motor pod reaches 130F, you better believe that the motor stator was HOT. And, the 'rare earth" magnet is likely Neodymium, which believe it or not, if the magnet/rotor temp get too hot - it can demagnetize - its all dependent on the magnet properties.

Make no mistake that 3-phase BLDC motors have a lot to offer; but the devil is in the details, they can be very complex; and getting a 5-yr warranty can be a challenge - there is a lot to go wrong. FYI - Hurst makes 3-phase BLDC motors http://hurst-motors.com/brushlessdc.html, and they look quite similar to the SOTA motor.

Take care & stay well,
Neil

PS/My last project with the Navy included a 400-HP 3-phase high speed permanent magnet ac synchronous motor with magnetic bearings designed to last 50-yrs - I know more about these motors than I ever wanted to know - :lol:
theeng
Member
 
Posts: 98
Joined: Mon Dec 09, 2019 9:47 am

Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby Votan » Sun Aug 02, 2020 3:44 pm

Hi Neil,
The issue of motor overheating is something I at least did not notice in my SOTA motor, checking very often the (very thin and good heat conductor) top plate on which the motor is screwed and in full contact, in my modified VPI pod.
Sota suggested to lower the voltage to -4V to the members of the forum who faced overheating problems. They did that and mentioned that problem solved.
Nevertheless, on the subject of natural motor ventilation which I think crucial, I suggested a solution in my post (viewtopic.php?f=7&t=14369&start=10#p61264) about what I intend to try as soon as I return from my summer vacation (I am retired, you see).
P.S. By the way, I find that you are a very knowledgeable engineer and I congratulate you because, above all, at last we read a serious and thorough review of the construction and operation of the motors under review.
Stay well you too
Michael
Prime Sign/10"3DR/Finite Element(FE) platform/SOTA's Total Eclipse/Lyra Titan/VPI Ring/WW Silver Eclipse 8 Ph.C/Groove+ SRX MkII Ph. St./Moon 740 Pre/Moon 820 PSU/ATC 100 Active Speakers/AQ Niagara IC/WW Silver Electra AC,FE Ref Rack/RPG Room Treatm.
User avatar
Votan
Senior Member
 
Posts: 378
Joined: Sun Dec 02, 2018 4:59 pm
Location: Greece, Larisa.

Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby theeng » Sun Aug 02, 2020 4:29 pm

Hi Michael,

Your way of introducing air flow will work, but you will need lower air vents to draw-in the air, but you may compromise acoustics. I am not saying the motor is noisy, but Airborne noise acts like a wave-field and it will beam (very directional) through any opening or orifice.

I wonder if using Soft Silicone Thermal Putty such as https://electrolube.info/pdf/tds/044/TCP400.pdf or Silicone Thermal Pads such as https://www.amazon.com/ADWITS-Thermal-C ... 022&sr=8-2 may not kill two birds with one stone as they say. The thermal putty can be used to ensure the motor housing has good thermal contact with the motor pod housing and at the same time provide acoustic dampening. As a putty, its relatively easy to apply (and remove for motor replacement); and Thermal Putty appears dielectric so no electrical issues.

Stay well.
Neil

PS/Thank-you for the compliment, and let me return the compliment; I respect your insight and engineering acumen.
theeng
Member
 
Posts: 98
Joined: Mon Dec 09, 2019 9:47 am

Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby Votan » Sun Aug 02, 2020 5:21 pm

Neil,
Concerning the lower air vents you mention, as I mentioned in my previous link, they are already provided by placing distance washers as well between lower edge of the main slot of the pod and the lower aluminum plate (which is held with screws between the rubber feet and the main cylindrical slot of the pod).
Also, as an alternative to the heat-conducting materials suggested by you (thanks for that), I think, your justified fear of the directional noise emitted from the gaps, to deal with it with DIY glasswool sound barriers that do not impede the free circulation of air.
Also, I thank you too very much for your kind compliment.
Michael
Prime Sign/10"3DR/Finite Element(FE) platform/SOTA's Total Eclipse/Lyra Titan/VPI Ring/WW Silver Eclipse 8 Ph.C/Groove+ SRX MkII Ph. St./Moon 740 Pre/Moon 820 PSU/ATC 100 Active Speakers/AQ Niagara IC/WW Silver Electra AC,FE Ref Rack/RPG Room Treatm.
User avatar
Votan
Senior Member
 
Posts: 378
Joined: Sun Dec 02, 2018 4:59 pm
Location: Greece, Larisa.

Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby theeng » Sun Aug 02, 2020 9:19 pm

Michael,

Error in ability to space the lower plate noted. The acoustic properties of glass wool is well defined - http://www.acoustic.ua/st/web_absorption_data_eng.pdf, but I am not sure you will get enough installed to be fully effective, and this report from 1950 on the gas permeability https://nvlpubs.nist.gov/nistpubs/jres/ ... 05.A06.pdf could challenge whether you will get good air flow noting that glass wool is also a thermal insulator. But, that is why we experiment - nothing ventured, nothing gained.

Stay well,
Neil
theeng
Member
 
Posts: 98
Joined: Mon Dec 09, 2019 9:47 am

Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby Golear » Sun Aug 02, 2020 10:43 pm

@theeng
Thanks for the info. I was a bit skeptical about the dynamic balancing, too. Anaheim Automation does not say that their motor is dynamically balanced. And perhaps we can assume, short of authoritative info, that it isn't. I'm not sure about the skewing, either. It's not totally clear from the photo. And there's no shaping of the input signals to deal with torque cogging. This is not an issue with most BLDC motor applications, of course (fans, model airplane motors, electric skate boards, etc).

Odd that I pose a couple of questions in this thread, and then that subject shows up in the photo ...from who knows where.... posted by Vienna Acoustics...

I didn't think about heat. I did read somewhere that rare-earth magnets are not as sensitive to heat as conventional magnets. But, of course, god is in the details.

PS: seems the SOTA motor costs less than the Hurst motor. I suppose one still has to buy a motor controller.
Golear
Senior Member
 
Posts: 479
Joined: Wed Nov 30, 2016 4:51 pm

Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby Votan » Mon Aug 03, 2020 4:11 am

theeng wrote:Michael,

Error in ability to space the lower plate noted. The acoustic properties of glass wool is well defined - http://www.acoustic.ua/st/web_absorption_data_eng.pdf, but I am not sure you will get enough installed to be fully effective, and this report from 1950 on the gas permeability https://nvlpubs.nist.gov/nistpubs/jres/ ... 05.A06.pdf could challenge whether you will get good air flow noting that glass wool is also a thermal insulator. But, that is why we experiment - nothing ventured, nothing gained.

Stay well,
Neil


Neil, thanks for the links, but I did not intend to cover air venting gaps with glasswool, nor of course to put in contact with the whole motor pod, since as you rightly say, glasswool is an excellent thermal insulator, something that is against our intentions here. Just place glasswool in some distance away from gaps, so that any emitted (imperceptible anyway) and air transmitted motor noise, to be trapped/absorbed much like the noise reduction curtains on highways, with the added advantage here that glasswool is an excellent sound absorber. In any case, it is still one of the trial & error experiments that is the golden rule (mine at least) in hi end anyway.

edw, Dorian, VinBob at al.
Is there anything newer from the long term operation of your SOTA motors at -4 Volts, compared to the initially observed overheating?
My concern in this is focused on its possible effect on the long-term reliable and trouble-free operation of the motor, given its hitherto undeniable superiority both in terms of quietness, speed stability and sonics.
Prime Sign/10"3DR/Finite Element(FE) platform/SOTA's Total Eclipse/Lyra Titan/VPI Ring/WW Silver Eclipse 8 Ph.C/Groove+ SRX MkII Ph. St./Moon 740 Pre/Moon 820 PSU/ATC 100 Active Speakers/AQ Niagara IC/WW Silver Electra AC,FE Ref Rack/RPG Room Treatm.
User avatar
Votan
Senior Member
 
Posts: 378
Joined: Sun Dec 02, 2018 4:59 pm
Location: Greece, Larisa.

PreviousNext

Return to General Audio

Who is online

Users browsing this forum: No registered users and 9 guests

x