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3 Phase Class D amp for DIY BLDC motor Drive
3 Phase Class D amp for DIY BLDC motor Drive
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Old 17th May 2017, 05:21 PM   #21
Pyramid is offline Pyramid  United States
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Quote:
Originally Posted by rsritchey View Post
Can you also attach the CAD files for the pulleys?
The attached file was for the pulleys....
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Old 17th May 2017, 05:25 PM   #22
rsritchey is offline rsritchey
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Yes, I showed it to a mechanical engineer at work, and he said he could get it made for me easier if he had a solid works (or other CAD program) model of it.
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Old 17th May 2017, 05:33 PM   #23
Pyramid is offline Pyramid  United States
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Quote:
Originally Posted by rsritchey View Post
Yes, I showed it to a mechanical engineer at work, and he said he could get it made for me easier if he had a solid works (or other CAD program) model of it.
I don't have Solid Works. It's a fairly simple design, most machine shops should have no problem with it.
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Old 17th May 2017, 06:06 PM   #24
rif is offline rif  United States
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3 Phase Class D amp for DIY BLDC motor Drive
Does anyone have familiarity with emachineshop.com or similar? I don't, but if it works like oshpark, where someone saves a design and anyone can order it, that would be ideal I would think
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Old 17th May 2017, 10:24 PM   #25
Pyramid is offline Pyramid  United States
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Quote:
Originally Posted by rsritchey View Post
Yes, I showed it to a mechanical engineer at work, and he said he could get it made for me easier if he had a solid works (or other CAD program) model of it.
OK, so I downloaded the free CAD software from emachineshop.com and after a few false starts, was able to recreate both pulleys and export them in .STL format. Emachineshop.com quoted $229 for 10pcs and $281 for 25 pcs (I think 1 pc was $180). The material is spec'd as Acetal which is the generic term for Delrin.

When I had the local machine shop make pulleys, the prices were similar but I sent them a motor so they could dry fit the center bore and dial in the tolerance so the fit was snug but not an interference fit and not sloppy so the pulley would wobble. I don't know if the tolerances indicated in the attached files are adequate or not; maybe if/when someone has pulleys made, they can have that conversation with the shop. The original machine shop that I tried could not keep things concentric. The center bore was done with a boring bar and for the 4mm part, was very small and deflected too easily. The shop that finally did the pulleys used a high speed lathe and removed very small amounts of material at a time.

PN 8900-03-0600 has a 4mm center bore, PN 8901-03-0600 has a 0.25" center bore.
Attached Files
File Type: zip Pulleys.zip (115.1 KB, 51 views)

Last edited by Pyramid; 17th May 2017 at 10:46 PM.
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Old 17th May 2017, 11:15 PM   #26
TonyTecson is offline TonyTecson  Philippines
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3 Phase Class D amp for DIY BLDC motor Drive
if you have an update, just post it as a latest upgraded version...
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Old 17th May 2017, 11:25 PM   #27
InSides is offline InSides
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As mentioned, the datasheet for the motors (well, for the BLWR series) specifies a tolerance of 0.012mm for the shaft diameter. Not sure how that translates to practice, i.e. how much shaft diameters differ in practice between motors.

Ideally, one would do like @Pyramid and have the shop dry fit the part to the exact shaft it will mate to. That is what I intend to do anyway - I've been told that tolerances might need to be adjusted should one opt for a different material.
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Old 17th May 2017, 11:42 PM   #28
cary300b is offline cary300b  United States
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First and foremost, I would like to thank Bill for all the work he has done and for sharing his designs with the rest of us.

Reading posts in this thread, and other related ones, put me back on a learning path.

Here is some information about my project -

I made replica of a turntable that I owned once upon a time - Micro Seiki RX-5000.

Several changes/improvements, such as stainless platter, stainless bearing housing, machined solid aluminum base, etc were incorporated. At the risk of sounding arrogant, I would say that the replica is every bit as good as the 'real thing'. Photos will follow.

The best drive option I could come up with was DC motor and FG servo control board salvaged from a vintage Pioneer turntable. This motor was design to drive a platter with 200mm hub underneath. I had to tweak the board to increase the speed and machine larger pulley in order to drive 310mm diameter stainless platter weighting in around 20kg.

Needless to say, when I found out about SG4 project, that Bill so generously shared with us, I jumped on it and built a drive for PAPST motor that came out of an EMPIRE 298 turntable. This PAPST motor variety has 4 posts holding two rectangular plates together and I believe this design is superior to other PAPST frame options out there.

SG4/PAPST AC drive works well and it is definitely a big improvement compared to vintage Pioneer FG Servo DC motor. Due to a high speed of the PAPST motor (1800 rpm), fairly small diameter pulley is required. Therefore, contact area between pulley surface and kevlar thread that drives the platter is also very small and rather large tension of the thread is required to avoid slipping. Once the tension of the thread is properly adjusted it takes about 8 seconds to bring 40lb platter from 0 to 33.33 rpm.

PAPST motor is very quiet but I still have to find optimal capacitor value and try two phase connection that would eliminate capacitor.

Out of desperation, I tried modifying Hurst AC motor with very little success. First, I added an oilite bronze sleeve on the bottom of the original housing so that the rotor shaft is supported on both top and bottom. Improvement was negligible and motor was still quite noisy. Next, I machined new solid aluminum motor housing, transplanted Hurst coils and rotor and used ABEC 5 rated ball bearings on top and the bottom. Motor looked like a serious piece of engineering after all this was done. I wanted to believe there was some improvement to justify time I spent, but in all honesty there was none.

Hurst people should consider replacing micrometer in their company logo with a pipe wrench or a sledge hammer. Joking aside, my conclusion is that no level of modification would make Hurst AC motors suitable to drive turntable platter.

Yesterday I purchased two BLWR motors and ordered circuit boards and parts. I can't wait to put it together and try...
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Old 18th May 2017, 12:05 AM   #29
Pyramid is offline Pyramid  United States
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Update to post #25: The CAD drawing for the 4mm shaft part (8900-03-0600) did not have the 4-40 threads going all the way through to the center bore. This is corrected in the attached file.
Attached Files
File Type: zip Pulleys.zip (115.1 KB, 65 views)
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Old 18th May 2017, 12:08 AM   #30
cary300b is offline cary300b  United States
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Precision boring small ID hole is somewhat difficult task. Also, type of material being machined makes a HUGE difference.

Boring bar required is very small and it easily deflects during the cut. The only way to do this right on a regular engine lathe is to remove very small amount of material in a single pass to minimize tool deflection.

Boring/drilling an undersized hole and reaming it to size does not guarantee precision fit. This is simple/cheap operation and shops often employ it.

Absolutely best way would be to drill/bore slightly undersized hole and then grind the ID to a desired size. Grinding tolerances are typically in 0.000x" range but precision grinding is quite expensive.

Don't let my comment discourage you. Difficult doesn't mean impossible if machine shop guys know what they are doing.
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