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Thread: Boring out an impeller collar
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12th May 2018, 10:37 AM #31Diamond Member
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Thanks Bob(L) for your write ups and explanations of motors, VFDs dyno tests and vibration analysis etc over the years. While I am unlikely to ever replicate them, I do find your writings most interesting and informative, and if some time I need to undertake something similar, I will have a good starting off point. Like BTs magazine quality photos, your explanations are always easily understood, and often well illustrated with graphs and photos of your test rig setups which would compare most favourably with an article in a technical magazine, so well done and thank you very much for taking a considerable amount of your time to share your findings with us.
Rob.
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12th May 2018, 12:07 PM #32Member: Blue and white apron brigade
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Thanks Rob. I spent most of my working life writing technical reports and research papers full of stats and graphs and used to teach technical writing to physics students so you you could say I have had a bit of practice, and maybe I should be doing a better job with my forum posts than I do, just getting a bit slack since I retired I guess.
I know what I do is OTT sometimes for basic MW, but it's sort of autopilot mode for me, see something, measure it, measure it again, UH-HO, make something to measure something else, collect data, analyse the data, repeat, several times, go around in circles, run out of puff, try to come to some conclusions, plonk it all on the forum. Repeat. It's how I fill my day.
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12th May 2018, 02:11 PM #33Diamond Member
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12th May 2018, 03:43 PM #34Member: Blue and white apron brigade
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Just in case this passes you by I just checked the 3P impeller rotation and I realised had it the wrong way so had to redo all the 3P measurements - I also did some other motor frequencies.
New results replace old in the post above.
In general even lower vibes than before.
The 3P with the impeller going the right way is significantly noisier that the SP with impeller.
@ 50Hz the SP with impeller was 76.5 db @ 1m while the 3P is 82dB, and 90db @ 60Hz.
I think I know why that might be the case and that is has something to do with internal impeller/housing clearance. Despite my best attempts to stay consistent I know I didn't put the wooden box around the impeller back on the same way because the impeller started to hit the inside of the wooden enclosure and I had to chip out a bit more wood for clearance. If I did not hog out enough clearance wood it will make the impeller scream.
Last edited by BobL; 29th Jun 2019 at 01:27 PM.
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12th May 2018, 07:43 PM #35Member: Blue and white apron brigade
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More farting around - his time to see if filling the old unfilled keyway on the shaft makes a difference.
I don't expect it will make any difference because the vibe levels are already low anyway.
I whipped up a pseudo curved half key from a bit of galv strap using my thin kerf cutting wheel and a small linisher.
IMG_3043.jpg
IMG_3045.jpg
The first thing I noticed is that the noise levels are back down by about 3dB.
I seriously doubt its due to filling the unfilled keyway but where the clamps are located on the steel plate on top of the temporary wooden impeller enclosure seems to affect the noise..
Now for the vibe data.
I'm not convinced any of this is real or at best marginal.
20% of the vibe is now from the motor itself so I suppose this is about as good as it gets.
Still worth a shot.
Screen Shot 2018-05-12 at 4.22.15 pm.png
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12th May 2018, 10:32 PM #36Diamond Member
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Well I for one are grateful for your little dissertations, even if I am unlikely to follow your example, they are interesting and make one realise just how much behind the scenes effort is undertaken by designers to turn a concept into reality.
I now see where the polish comes from in your writings, thanks again and keep up the good work Bob.
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18th May 2018, 10:43 PM #37Member: Blue and white apron brigade
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Well the motor and impeller are finally back together inside the Dust Extractor housing.
As usual it's the side issues which consumed far more time than I anticipated.
Fitting the motor and impeller back in was much harder than taking it out especially as all this is being done inside a cupboard 600mm deep though a just a 450mm doorway.
Taking the motor and impeller out was relatively easy because it was a "down and out” motion, but going back in was an “in and lift up” exercise which was much harder,.
When the old motor and impeller was being removed it fell onto the baffle box and being made out some crappy chip board is partially fell apart so it had to be rebuild.
impeller2.jpg
In the end I took the motor shaft bolt out (fortunately I had not already thread locked it) and fitted a large eye bolt in its place, attached a chain to the eyebolt and incrementally pulled / levered the motor and impeller up via the entry port ( which has also been replaced) using the chain and placing wooden blocks underneath eh motor.
I was really pleased with my drilling as everything lined up and all the bolts when back on without jamming
Replacing the 5m long SP cable with 3P cable took up the most time as I thought I could just solder one cable to the other and use the SP cable to pull the 3P through but it got stuck and so had to remove gyprock lining panel to rescue it.
I eventually saw the 3P cable was a touch thicker than the SP cable which probably caused that,
Anyway I finally had the impeller spinning in its housing with some basic wiring back to the VFD.
Tomorrow I need to sort out the remote VFD operation and a few other things and then do some flow testing.
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18th May 2018, 11:14 PM #38Diamond Member
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It sounds like it was one of those mongrel jobs Bob, where everything that could go wrong or be difficult, did, and the job was longer and more frustrating as a result. I sure hope that the final bits and testing go well for you, good luck'
Rob.
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19th May 2018, 12:46 AM #39Member: Blue and white apron brigade
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19th May 2018, 04:45 PM #40Most Valued Member
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Nice work Bob. I really appreciated the effort you put into the testing part and the vibration graphs. I love a good graph!
Please tell me that the resultant vector sum of all three was done by the app and not done manually by you!
Anyway, I'm happy for your results. well done to you and AB. It's great fun catching up with forum members.
SimonGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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19th May 2018, 09:02 PM #41Member: Blue and white apron brigade
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Nah - I did the sum its not that hard )
As I said above I have installed the motor and impeller and a new connector and here are a few pics
This is what I had before, a pot plant pot with a transparent inspection port.
It was not a smooth transition and it leaked
inputPort.jpg
And here is the new setup with an easily removable Polycarbonate sleeve - works a treat
joiner4.jpg
It now sings along at 60Hz with current draw dependent on number of dust ports open on machinery etc.
More details here: Upgrading a 3HP Single Phase DC with 4HP 3P motor and VFDLast edited by BobL; 22nd Feb 2022 at 11:11 AM.
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