Author Topic: Tacho for mill  (Read 5535 times)

Offline boatmadman

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Tacho for mill
« on: October 26, 2009, 12:29:36 PM »
Being the proud new owner of a seig x2 mill and accessories, courtesy of CC - thanks Dave - I couldnt wait to have a play.

So, plugged it in, clamped it to my workmate and turned it on, without a tool, just to see it work!

All went well, looked around it...mmm nice, played with the variable sppeed.....nice, but hold on a sec, this means that I only know for sure what speed it is doing when it is stopped and at full speed in either ratio....need to improve this.

Idea, optical hand held tacho, £25 and upwards, but means I have to find it and hold it every time I turn on the mill.

0300 hrs wandering around work and  :smart: a bike computer measures rpm of the wheel and displays in kmh - a rev counter!!!!

Got the abacus out, and after much work, realised that there is a constant number that when input as the wheel size, will display a number in kmh that is numerically the same as the wheel revs.

And the magic number is..1667

Went to that well known car and bike parts shop, bought a computer for £9.99, first having checked it has a 4 figure output, 000.0  took it home and entered the magic number, mounted it on the mill using a small neodym magnet (not the supplied one) on the mill spindle, glued the pickup on the body with superglue, turned it on and bingo, it works.

Now, is it accurate? YES!! but you do have to ignore the decimal point in the speed readout to gt the revs.

I borrowed an optical tacho from work to check it and its spot on.

Drawbacks? only one so far, it only goes up to 2000rpm!

Nice touch? It has an auto power up when the mill starts, and auto off 10 mins after stopping. :thumbup:

Ian
If it works, take it apart and find out why!

Offline andyf

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Re: Tacho for mill
« Reply #1 on: October 26, 2009, 12:37:20 PM »
Hi Ian, I got one last year from Halfords, but it only goes up to 100kph, representing 1000 rpm. No doubt the makers thought that most cyclists wouldn't be doing more than that - it's 60mph, ater all. I might drop in to see if the Altrincham branch has one like yours - what was the name on the packaging, please?

Andy
Sale, Cheshire
I've cut the end off it twice, but it's still too short

Offline Darren

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Re: Tacho for mill
« Reply #2 on: October 26, 2009, 01:24:51 PM »
Very nice idea, my only worry would be the magnet taking flying lessons  :zap:

Oh and balance now being off a touch?
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Offline boatmadman

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Re: Tacho for mill
« Reply #3 on: October 26, 2009, 02:22:21 PM »
The unit is an 'echowell star'

I have just done a few more trials with it and found that, yes, the magnet flew off at high revs, over 2000. As far as the balance is concerned, the magnet is very light and the shaft radius is small, so out of balance forces will the there, but small. I think I will mark on the dial a range of speeds then remove the magnet to avoid out of balance issues.

Using the borrowed optical tach, I have found that the spindle speed is actually twice that indicated on the machine label. The machine has had a drive belt conversion fitted, so I was wondering if this is the result of the conversion.

More trials needed, but for now, its off to work :scratch:

Ian
If it works, take it apart and find out why!

bogstandard

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Re: Tacho for mill
« Reply #4 on: October 26, 2009, 02:25:46 PM »
Cut the magnet in half, then your readings should only be half of what it should be. :doh:

Very nice improvisation BTW.


Bogs

Online jim

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Re: Tacho for mill
« Reply #5 on: October 26, 2009, 03:00:41 PM »
thats a great idea.

i'm now thinking, two magnets (180 deg apart) input 838 (half 1667) and secure with a cable tie. then you've got balance.

i was just thinking i wonder what my mill runs too, Mrs Jim has just reminded me its already got a display :doh: :doh: :doh: :doh:
if i'd thought it through, i'd have never tried it

Offline 75Plus

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Re: Tacho for mill
« Reply #6 on: October 26, 2009, 04:49:37 PM »
Here is a deal for a bike computer that has an RPM function although I don't know the max. reading. Under $4 US with shipping included!  :clap:

http://cgi.ebay.co.uk/Bike-Bicycle-LCD-Cycle-Computer-Odometer-Speedometer_W0QQitemZ230382322805QQcmdZViewItemQQptZUK_Sporting_Goods_Activity_Monitoring_MJ?hash=item35a3db4475

I have one ordered and will report back when it arrives. My plan is to make a new cap that covers the draw bar nut and mount the computer on it. I will put the magnet/s in the notch/es of the spanner nut that retains the spindle. By doing it this way I can remove the computer and cap as a unit and any flung magnets will stay where I can find them.

Joe

Offline CrewCab

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Re: Tacho for mill
« Reply #7 on: October 26, 2009, 05:21:08 PM »
The machine has had a drive belt conversion fitted, so I was wondering if this is the result of the conversion.

I believe so Ian

http://www.youtube.com/watch?v=C_6atCLtSWk

On the video Low range is @1500RPM, that's a little lower than you've found, high about 4000RPM, I never used the high speed  :bugeye:

Hope all is well and your having fun.

Dave

Offline CrewCab

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Re: Tacho for mill
« Reply #8 on: October 26, 2009, 05:21:57 PM »
The machine has had a drive belt conversion fitted, so I was wondering if this is the result of the conversion.

I believe so Ian

http://www.youtube.com/watch?v=C_6atCLtSWk

On the video Low range is @1500RPM, that's a little lower than you've found, high about 4000RPM, I never used the high speed  :bugeye:

Hope all is well and your having fun.

Nice idea about the tacho  :headbang:

Dave

Offline boatmadman

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Re: Tacho for mill
« Reply #9 on: October 26, 2009, 05:47:32 PM »
Jim,
securing with a cable tie might not work, you have to get the pickup really close to the magnet to get the reading. Maybe some tape on the spindle to protect it, then a blob of glue to help hold the magnet to the spindle - will try this when I get up tomorrow.

2 magnets might be a good idea actually, it will give better low speed readings.

Ian

One other interesting function of the computer is that you can see how far the mill has travelled while standing stil!!
« Last Edit: October 26, 2009, 05:55:12 PM by boatmadman »
If it works, take it apart and find out why!

Offline John Hill

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Re: Tacho for mill
« Reply #10 on: October 26, 2009, 06:02:49 PM »
I have used these little bike computers for a couple of things, anemometers etc but the last one I bought is useless!  The calibration for wheel size is no longer there instead it has a table of most common bike wheel sizes so the mathmatics becomes more difficult!
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Offline andyf

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Re: Tacho for mill
« Reply #11 on: October 26, 2009, 06:03:35 PM »
Thanks for the info on the brand, Ian.

I thought about 2 magnets, but the bike speedo I bought wouldn't cater for an 833mm circumference wheel. I suppose that such a wheel (under 11" dia) might be unusual on anything except a kiddy's bike.

Ideal would be to find or attach a horizontal rotating surface to the spindle, drill a hole in it and glue the magnet in there. That would restrain it, and with luck, the material removed to make the hole will weigh about the same as the magnet, which will help keep things reasonably balanced.

Andy
Sale, Cheshire
I've cut the end off it twice, but it's still too short