Jul 13, 2011 at 7:55 am #1276656
Edit: Resolved. Going with an electronic counter. Thanks all.
I'm doing some fabric testing and need a mechanical 6-digit ratchet counter. It will get attached to a piston shaft that is compressing a wad of fabric, counting each stroke, at around 50 cycles per minute. I need to keep track of about 3 million cycles.
I've found this Line-Seiki in Japan for $20US + shipping + international money order etc.
I've found a USA made Veeder-Root for $210 + S&H.
And I found some on eBay for $8 that last about 8 hours/24,000 strokes. (China Plastic Junk)
If you have any leads I'd appreciate them.
If you have any ideas "out of the box", I'd appreciate them.
Thanks.Jul 13, 2011 at 11:00 am #1758896
I'm not sure exactly how "accurate" you need your counts to be. But if you have a specific and consistent cycle time can't you just measure time in the testing machine?
At 50 cycles/minute and 3million cycles you're looking at 1000 hours of testing time. At this point even being off by 1 hour is still only 0.1% inaccuracy which is far more accurate than probably just test subject variability.
Also if you're doing 3 million cycles you need a 7 digit counter, not 6.Jul 13, 2011 at 11:08 am #1758899
McMaster-Carr has a variety. They aren't always the cheapest, but they stock everything and ship very fast. Scroll down about half way for the lever-type counters.
JerryJul 13, 2011 at 11:18 am #1758902
You can buy little digital pedometers that clip to a belt. Often for as little as £1/$1.
Get one, and replace the gravity switch with a decent microswitch, or, better still, an IR (non-contact) switch that won't wear out; the cycle rates you're talking about are pretty serious… hmmm… will your test rig survive that many cycles… ;-)
Can't remember how many digits they have; maybe not enough.
Either that, or get some other electronic counter; electronics these days are cheaper than mechanics…
ps. my first suggestion was going to be 'get a cheap calculator, and modify it so that a switch replaces the '=' button, and start if off with +1 =========='. Should be good for 10 digit counts…Jul 13, 2011 at 12:36 pm #1758927
@Dustin: Testing along the way, mechanical failure interruptions, power outages, and a variety of other things make the manual bookkeeping a challenge. I know… I'm doing that now. I Am able to keep a "hash mark" count of the millions. I just don't want to do that for the 99,999s.
@Jerry: a resettable McMaster-Carr 6-digit is $106 + S&H. Better, but still more than I'd hoped.
@Kevin: I've thought about cycle computers and pedometers, but I don't think any of them are 6-digit.
Hacking a calculator is a possibility. Just need to find the right calculator, a reed switch, magnet……
A digital counter, power supply, actuator…I'll do some searching.
Thanks all for the input.
Anyone else?Jul 13, 2011 at 1:19 pm #1758943
You might give a Lufkin measuring wheel a shot. They're less expensive than the counters at MMC and should be just as effective for this application. You should be able to take the wheel off, make a crank arm the appropriate length to get the units to work out and its all gravy from there.
Don MeredithJul 13, 2011 at 1:43 pm #1758949
@erdferkelLocale: S. California
You might want to consider an electronic counter like an omron along with a microswitch. This combo should be good for many more than 24000 actuations. Try ebay…Jul 13, 2011 at 1:52 pm #1758953
"This combo should be good for many more than 24000 actuations."
That is a little shy of 1 to 3 million.Jul 13, 2011 at 5:12 pm #1759026
@Kevin – Thanks for the push into the digital age….
I found a counter that is battery operated (10 years), 7 digit, resettable, with a "no voltage" closure input for $29. Every time the plunger comes down it can close a switch. Pretty simple.Jul 13, 2011 at 5:16 pm #1759029
@b-g-2-2Locale: Silicon Valley
"That is a little shy of 1 to 3 million."
What is a couple of orders of magnitude among friends?
–B.G.–Jul 14, 2011 at 10:18 am #1759267
> @Kevin – Thanks for the push into the digital age….
I guess being an electronic engineer, I had to fly the flag a bit…
As for the switch input to the counter, I'd seriously suggest looking at a non-contact opto-switch, because the test cycles you're talking about are likely to severely tax a conventional switch. A typical, quality microswitch might have a quoted life of only a million operations. It's the mechanical bits that wear out; hinge, plunger, spring, contacts etc.
An opto switch will just keep turning on and off (although it would be wise to consider the MTBF; different failure modes for mechanics and electronics…)Jul 14, 2011 at 12:33 pm #1759314
Magnetic and optical all require some sort of additional low voltage power.
So I'm going with a "no voltage contact switch" input to the counter. The counter has built-in "de-bounce" circuitry. I've found a Tamiya microswitch ($2.50 each) that seems to rated at 10,000,000. I'm waiting for a call from Tech Support. And if it is only 1,000,000 I'll preemptively replace it every 750,000. NBD.
Thanks for you input. I appreciate the suggestions and considerations.
Inasmuch as I am flying blind, I need as much help as I can get.Jul 14, 2011 at 6:31 pm #1759434
Years ago I needed a counter and found that I could use a calculator. It was a Hewlett Packard with RPN ( you enter 1 first, then enter 1 + repeatedly). Worked great for 50,000 to 100,000 cycles.
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