Mechanical Ratchet Counter – Source?

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.

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.

http://www.mcmaster.com/#mechanical-counters/=d5ssma

Jerry

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…

First hit on google.co.uk. About £50. US sources look to be about the same price.

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…

@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?

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.

Lufkin Measuring Wheel at Lowes

Don Meredith

lightpack.blogspot.com

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…

"This combo should be good for many more than 24000 actuations."

That is a little shy of 1 to 3 million.

@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.

"That is a little shy of 1 to 3 million."

What is a couple of orders of magnitude among friends?

–B.G.–

> @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…)

Kevin,
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.

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.

Best regards