Grinder Balancing again

Richard Shute heeft ons zojuist aangekondigd :

Would like to read that pdf..!

Richard Shute presented the following explanation :

Yes please!

I have to confess I'm not quite sure what you did but it sounds very Interesting. I for one would appreciate a fuller explanation if that 's what a pdf means.

regards Andy Cawley

Hello Chaps, sorry for the tardy reponse, but I can only access NG's in the morning so it's a 1 day cycle - very tiresome, but that's life.

I gave up trying to upload a picture to Photobucket, I've tried with a couple of browsers and both last night and again this morning. I've no idea why it isn't playing ball, but I did manage to put a pdf here:

There were only two design criteria: 1) Fit within the grinder cover,

2) Make from scrap material & balls I had in the box

Given the opportunity I'd have made it larger in diameter and probably used slightly larger balls as both would allow a greater imbalance to be corrected. As it is, the balls are 3/16" (5mm) dia, they run in a track which leaves them just enough space to rattle about freely without getting trapped, but not so radially deep that they can be in anything other than in single-file when stopped.

I used 6 or 7 or so - approximately, carefully selected to be round - yes, of course, I'm being flippant. Frankly I was skeptical it would work and just put 'some' in, but it did and I never pulled it off the count them. As long as there is plenty of empty space I suspect the actual number doesn't really matter much, 'though presumably more would be able to correct a larger imbalance up to a point - where there are so many that they can't separate adequately

The 'lid' is dished to allow the nut to go on the end within the cover and is also governed by the length of the shaft sticking out of the grinding wheel. I put a small squirt of oil in the groove before putting the lid on as corrosion protection and possibly as lubrication

- seemed a fair idea.

I hope it works for you guys. Richard

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Richard Shute was zeer hard aan het denken :

Thank you..!

Richard Shute explained on 30/03/2010 :

Thanks,

The 'in towards the centre' lip on the RH part looks like the only difficult part to machine and I don't really see a need for it, providing the two parts are made to fit such that the balls cannot escape.

Does this work with a grinder fitted with a wheel at either end of the motor shaft? I would expect one to be needed for each wheel.

I'm trying replying via Google Groups as I'm sick of the 3hrs-ish a day only access to NG's from my ISP, so this may appear differently from my previous post

Harry, I agree with you. The lip started as a mild replication of a ball bearing track which seemed a good idea initially when I thought I might not be able to fit a lid, but after putting the lid on it becomes superfluous and the lid is definitely needed or the balls will probably fall out when it's stationary and it would also fill up with grit and crap which would be no good. It's not difficult, I just used a grooving tool, but I could have saved some axial length had I omitted it - or used larger balls, if I had them :-)

As I said at the start, it was an entirely empirical undertaking which evolved as each bit of swarf got removed, no plans, no measurements, no 'design', just lob it in the lathe and make some swarf till it fitted - not my usual approach, but sometimes it happens.

It is fitted to a grinder with a wheel at each end. I was very aware that one wheel (Chinese cheapy) was much more badly balanced than the other (Norton) so in the first instance I made only the one balancer and put it on the 'bad end' just to see. Certainly at some point I will make a second, but the better wheel is not badly worn and at present the overall balance is pretty good so it is well down the list....

Richard

Try setting up an account with freenews.netfront.net.

No password required and it lets you post as well as read. I resorted to it when my normal usenet service was down for maintenance. It covers all my usual groups, fast access and no time constraints or posting limits.

That's useful to know in case my ISP ever decides to cut the news feed, thanks Dave. (Mind you, that might just tip me into changing ISP instead!)

David

Thanks for that - it seems most counter-intuitive, does anyone know how it works?

-- Peter Fairbrother

82 microns, and falling

Gosh! that looks simple. I take it that the balls are not crowded and automatically take up a position that resolves any imbalance. Wow!! I look forward to hearing the theory if any body knows it; not that it really matters 'cos it apparently works.

Thanks for the info. Andy Cawley

Hello Peter, It's actually blindingly obvious once you draw out a sketch of the situation. I have put one here:

We want the whole system to rotate about the bearing centre as indicated by the centre cross mark. But, the 'system' will try to rotate about the CoG as marked.

This then means that the balls are flung to the far side of their circular track and in doing so move in a manner such as to counteract the imbalance about the bearing centre. The whole lot thrashes about for a bit until it stabilises, and the only stable situation is 'balanced', providing the mass of balls available is adequate.

Richard

PS Thanks Dave for the NG pointer, but I'm already using them. It is the ISP who somehow prevents access for much of the day, 'though perversely and uniquely, I did have access yesterday afternoon.

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Hello Andy, Yes you are correct, the crucially important feature is that the balls are NOT crowded, indeed I'd say something less than 30% is about right so they can move and bunch as best suits the instant.

I haven't bothered to do any theoretical analysis on this, but for a

1st yr student it should be an amusing diversion to see the most efficient filling and other dynamics of it all. Richard

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Ah sorry. I'd only looked at the Google post and not noticed your others were already from Freenews.

It's unusual for an ISP to block Usenet. P2p yes, mine does that for a few hours every day but I can't see why Usenet would be a problem to anyone or even how they'd block it.

Not at all. ISP's block/throttle usenet to stop/limit binary downloads. Downloading pron/DVDs/TV programmes/CD ISOs from a binary newsgroup provider uses mega bandwidth.

ISP's that block/throttle typically don't discriminate between binary and text-only newsgroups or indeed binary and text-only servers.

AFAIK the ISPs maintain a list of newsgroup servers and throttle/block at IP level.

Sometimes, the ISP will provide an in-house text-only service and block third-party services.

HTH.

Dave Osborne was thinking very hard :

They tend to block the port number rather than the IP. You can easily get around it by using a newsreader and news server which allows use of a none standard port number.

Neat.

I guess you could apply this to a number of situations - how about a self-balancing faceplate for example? You might need rather large balls though...

Regards, Tony

counteract

Got them !!!!

AWEM

High time you attached them to your faceplate then ;-)

Regards, Tony