Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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Mark Harry what is your opinion of the draper machine? I would have thought the oval pattern it makes would be a very good match for your style - But you use an Elgin right? 
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Richard Caldwell
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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I am looking into using a variable speed setup for my mirror grinding machine. This seems to be a very nice variation of grinding machines so that's why I bumped the thread. What I want is a control knob that allows me to adjust the speed of the turntable and/or the eccentric without the whine, hum or other irritating noise many variable speed setups have. I repeat, WITHOUT the whine, hum or other irritating noise most variable speed setups have. 
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Richard Caldwell
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 372
Loc: UK
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My old Draper used to make a noise like a very ancient steam loco, you get used to it eventually.
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Mark Harry
Post Laureate
Reged: 09/05/05
Posts: 3126
Loc: Northeast
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"Mark Harry what is your opinion of the draper machine?"
**************
Never laid eyes on a real one. In the shop where I worked, we had CNC polishers, and Elgins exclusively. Oh, and one other, a pair of hands!
M.
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So many projects, so little time!
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john nichol
Vendor- Nichol Optical
Reged: 06/10/07
Posts: 10
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The problem with the Draper machine is that it does not lend itself well to off centre (sorry I'm English) work, this can be a limitation when it comes to figuring.
John
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GlenM
Vendor
Reged: 05/20/07
Posts: 1740
Loc: Lancashire UK
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Just logged in after a few days with health problems. It's good to see that you have joined CN John.
Could I just say that the mirrors I have purchased from you in the past have been excellent.
Good to see you here.
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Glen
www.lyraoptic.co.uk
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john nichol
Vendor- Nichol Optical
Reged: 06/10/07
Posts: 10
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Been around for a while Glen, just a little shy when it comes to posting!! Thanks for your comments about my mirrors.
John
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GlenM
Vendor
Reged: 05/20/07
Posts: 1740
Loc: Lancashire UK
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Sorry John,didn't realise.
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Glen
www.lyraoptic.co.uk
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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O. K. back to the Thread.
Anyone know a hot setup for a variable speed grinding machine? I need to adjust the speed of the turntable and/or the eccentric without the whine, hum or other irritating noise many variable speed setups have.
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Richard Caldwell
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8334
Loc: Bremerton Washington
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Quote:
O. K. back to the Thread.
Anyone know a hot setup for a variable speed grinding machine? I need to adjust the speed of the turntable and/or the eccentric without the whine, hum or other irritating noise many variable speed setups have.
Well..My 60+ year old machine utalized large bronz wheels that run against each other. The smaller which afixed to the drive shaft drives the much larger one that drives the vertical stroke arms and table. When the smaller wheel runs against the larger closer to its central the larger one turns faster. If you slide the smaller out to the larger ones edge the control arm/table rotates slower.
Of course..I'm the luckiest person alive..since I was given my pre WW2 4 table/tub machine.
Honestly I don't know of any machine that isn't noisy to some degree. My 4 table machine is very quiet...short of its motor and chain drive noise.
Grinding mirrors makes more noise....... 
Good luck in your search.....
All my machines have their noises...the Double table Draper..clunks back-n-forth...the Porter's leather belt drive and gears makes a repetative burring clink...and then the 4 table machine whirs and makes chain clinking noises...
Rob(I just play the shop radio a bit louder)
(Now the blank cutting machine makes the worst noise)
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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john nichol
Vendor- Nichol Optical
Reged: 06/10/07
Posts: 10
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Richard,
Let me explain the system I use with my machines here in the UK, it involves using the single phase mains electricty supply to run a 3 phase motor. By using a phase inverter it is possible to run a 3 phase motor from mains and have the facility to maintain torque whilst being able to vary the speed. The system works very well and there are no noise problems. I recommend it as a great method of producing a variable speed machine with all the advantages that this will give you.
John
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Glig
sage
Reged: 10/02/05
Posts: 370
Loc: Baltimore, MD
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This only works with 3 phase motors? And what is a "single phase mains electricity supply" Is it a self contained unit or a kind of installation from the power company?
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Richard Caldwell
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john nichol
Vendor- Nichol Optical
Reged: 06/10/07
Posts: 10
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Hi Richard,
The single phase supply is what is 'piped' into every home as standard, I am sure it will be that same in the US. 3 phase is used by companies running heavy duty elctrical machinery with higher power demands. You could look on ebay for phase inverters (single to three phase), or google it, might prove helpful.
John
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Mark Harry
Post Laureate
Reged: 09/05/05
Posts: 3126
Loc: Northeast
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I'm wondering if John is referring to frequency control, possibly? That readily changes speed with induction AC motors.
I use DC drives, for they maintain mega-torque at low speed. It offers extremely wide range, and are also very efficient with today's controllers. If you want to get rid of the hum, there is a way to install a filtering capacitor somehow to get rid of the 'spikes' on the DC side. You won't hardly note that it's running. The capacitor has to be matched to the particular setup. Don't ask me how, though. I prefer to hear them run anyways.
M.
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So many projects, so little time!
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Redstone2
journeyman
Reged: 02/28/09
Posts: 5
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Hello,
I have a MOM that I am converting to a three speed turn table with a VFD eccentric. The turn table will be driven by a three speed PSC motor (removed from a HVAC air handler). The eccentric will be driven by a 1/3 HP, 3 phase motor (I found it on Ebay for $0.99 + 20.00 s/h). The VFD also came from Ebay for $45.00.
To prevent "humming" proper attention must be paid to shielding and grounding. If you are looking into an AC VDF, I would recommend finding the install manual for a Minarik VFD02-D230AC or an Altvar 11 VDF. Both manuals will give you points and tips on installing a VFD.
I am building a series of pulleys for the VFD motor in order to give a wider range of eccentric speeds without motor cogging (and resonance) being a problem. DC is a good option also; I just found some good deals on an AC VFD.
Tom
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