Crazy idea?

Since you're going to have a second battery, why not just have a 12v battery? A 6v to 12v converter to charge the 12v battery and you're done. While you're at it, put in a cigar lighter across the 12v and you'll have a place to plug in your phone charger or a radio. ;-)

--
"I am a river to my people." 
Jeff-1.0 
WA6FWi 
http:foxsmercantile.com

Clutching at straws?

Like this?

What type of 12v clutch to you have? Disc, band, planetary, radial pin, ratchet, etc?

Some random thoughts, suggestions, and sanity checks:

1. The auger is going to generate quite a bit of torque. If the auger gets hung up on a rock, something in the drive chain is going to absorb the energy. Usually, its a shear pin or shear bolt. If you put a disc, band, or radial pin clutch in between the drive and auger, it will be the disc or band that takes up the load and convert the drive power to smoke or a pin that gets sheared.

1. I'm not sure what manner of PTO you have but if it's reversible, be sure your clutch will work equally well in reverse so you can back out the auger after you get it hung up on a rock. Disc clutches will usually work in reverse. Radial pin clutches, will not. Band clutches might work, depending on design.

2. Electrically, you want the system to run either on 6 or 12VDC, not both. Finding a 6V disc clutch might be difficult but replacing the generator, battery, starter, gauges, etc on the tractor probably more difficult. As a compromise, I suggest hanging a small battery and small alternator somewhere on the tractor just to run the 12v clutch.
3. If your auger is driven by a drive shaft with two universal joints, then maybe forget the electric clutch and use a radial pin clutch instead of a disc clutch. Note that some augers come with clutches: If you have machining capabilities, you could probably make one of these.

1. You wouldn't have this problem if the PTO was hydraulically coupled to the post hole digger. If you're proficient at putting together hydraulic system, it might be easier and better than installing a mechanical clutch. A hydraulic pump and motor, a disconnect valve, combined with a reversing control valve, would work, but is rather complex and potentially expensive. However, it has the advantage of only needing a single shear pin, no machining, and nothing on the tractor, PTO, or auger needs modification. The hydraulics on the PTO could also be used to power other impliments and machines.

More:

"Clutch for a Post Hole Digger"

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

The clutch's coil is not rewindable I presume, if it is that would be easier to live with.

NT

Greetings Jeff,

Yeah, that's the tractor.

A disc type from a riding mower.

I have the post hole digger. They all come with shear pins which are really grade 2 bolts. This is industry standard. Lots of folks ruin their digger gearboxes when they use grade 8 bolts instead of grade 2.

No reverse on the PTO. You have to take the bolts out and unscrew the augur using a big wrench. That's how it was done in 1939 on inexpensive tractors.

I wanted to somehow connect the generator in series with the battery but I like your extra alternator idea. Then there is a totally separate circuit. I like that idea.

I think I like the hydraulic idea the most. With a hydraulic pump and motor the augur could be reversed out if it gets stuck. And there would be no spinning driveshaft hanging out in the wind. I need to look at some surplus hydraulics.

Thanks for the great ideas Jeff. Cheers, Eric

You may want to look into something like a boost converter similar to this one:

YOu input anywhere from 5 to 12 volts and get out 12 to 60 volts. You will have to look for one that will take 6 volts as I thinkthis one just starts at 8.5 volts.

I have used some similar to this but only at 1 amp output.

The are almost like a DC transformer. You put in say 6 volts at about

10 and you get out 12 volts at 5 amps, not counting the efficency of the device.

Got any maximum torque specs on this disc clutch? My guess(tm) is that delivered torque to the auger is MUCH higher than what the disc clutch can pass before it starts to slip and smoke.

What's the diameter of the auger?

The engine is rated at 20Hp. The PTO spins at 540 rpm. That should produce 194 ft-lbs of torque.

So, will your mower disc handle 194 ft-lbs (plus a safety margin)? ... the gross torque on a walk-behind lawnmower is generally between 4.50 and 8.75 ft-lbs. ... a riding lawnmower generally has 10.5 to 26.0 gross horsepower. Methinks I'm beginning to smell clutch smoke. Looks like the clutch might be undersized by a factor of 10x or more.

The auger is fairly well matched to the tractor. I blundered across this spec sheet for a walk behind post hole digger: It wants 275 ft-lbs of torque at 140 rpm. If I slow the PTO down to

140 rpm, the delivered torque would be: 140 / 540 * 194 = 50 ft-lbs which is still 2x - 5x times what the riding mower clutch can handle.

Yep. The shear strength of the bolt also needs to be calculated. What size bolt are you using?

You didn't supply a number for how much current is required to lock the clutch at 12V. My guess(tm) is that it's not much. If so, then you don't need the battery and charging circuit. You could actuate the clutch solenoid solely with the battery.

Does the clutch solenoid need power to activate, or remove power to activate? (Normally disengaged, or normally engaged?) My guess(tm) is probably the former for safety reasons. If the engine slows down, the solenoid might drop out, but that's acceptable because the machine is not expected to be digging holes at idle or slower.

I also like the hydraulics idea. It's far more complicated, but also far more useful and versatile.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Have you looked into modifying the hydraulics?

I, after being chastised by you more than once, made sure to mention that the clutch draws about 5 amps in my original post. I appreciated the chastisement because it helps me to write better posts. The clutch is designed to handle about 16 HP, which is what my tractor PTO was able to deliver when new. But you are correct about the clutch probably slipping because it is designed to be run at about

2800 RPM. Especially with the big augur, which is 11 inches in diameter. I'm pretty sure the 6 inch one would be OK though because it is now being powered by a 3 HP motor. I am gonna look at all the surplus hydraulic I know of to see how much it would cost for the pump and motor combo. It really wouldn't be very complicated and I do understand hydraulic systems. Eric

I am not suggesting your idea(s) is (are) crazy. Nor am I suggesting that the suggestions here are crazy, either.

But. William of Occam suggested that we not multiply entities needlessly. Y es, you have a 1930s-40s tractor that uses a system that is radically unsaf e by modern standards. But, it works as found, as-is.

My summerhouse neighbor has a tractor of similar vintage with a similar sys tem in place. He has rigged a small tripod-type device that attaches and sw ings up to hold the auger in the raised position without need to run the hy draulics. That device fits so closely and looks so much like it was 'meant to be' that it might be factory-original. I will ask him the next time I se e him.

Would something like that even fit/serve/be possible without such gyrations as you are contemplating for a clutch, auxiliary power and much more?

There is another very common solution called "limiter chains" that are enti rely adjustable, and would allow you to fix the travel-height of the auger by their length.

Lastly, as these are expensive, there is a PTO Slip-clutch (to be distingui shed from an overrun clutch) that will also decouple the PTO from the devic e attached.

The chains and the clutch are off-the-shelf devices still made for that tra ctor to this day. The first device I cannot find - it may be home-made.

Jeff A: a 6 V aux.socket will charge a phone just as easily as a 12V device , what with smart chargers these day. Just an FYI.

Peter Wieck Melrose Park, PA

Can your neighbor's device be used while sitting on the tractor? I need to be on the tractor when operating the post hole digger. Because the auger must be rotating when it is raised and to hold it in the raised position. And I stay away from the rotating auger. If your neighbor's device can be worked from the seat then if you could please take some pictures and email them to me I would be very grateful. Pictures with a yard stick or tape measure included would be a big help for scaling. I still like Jeff's hydraulics idea. It gets rid of the spinning driveshaft and allows reversing out of the hole. More than once I have hit roots or big rocks that required removing the shear bolts and unscrewing the auger from the ground with a pipe wrench. I have looked for and not found a clutch that is made for disconnecting the PTO rotation from the device being powered. You got a link? There are slip clutches but they won't work and I already have an over running coupler installed but they are just to keep the driven implement from back driving the tractor. Eric

We will not be in the area for a bit - but he is very friendly and I would be glad to get pictures if he is available.

Peter Wieck Melrose Park, PA

In the meantime:

Once upon a time made electric PTO clutches. All I see now are mower-clutches vs. in-line clutches. But they may still be available.

More later, I hope.

Peter Wieck Melrose Park, PA

Oops. I screwed up the above paragraph. As you noted, you did mention that the 12v clutch drew about 5A. That's not huge, and I think it might work. It will need some testing to see what the clutch will do at voltages below about 10V. I also screwed up the last word. Instead of actuating the clutch solenoid with the battery, it should be actuated with the alternator, generator, or PM motor.

Thanks. I just hate it when I make a mistake and need to be reminded that I'm not perfect.

I don't know. Big maybe, but it is worth trying the 6 inch clutch. However, I still like the hydraulic solution better because of the versatility.

My experience with hydraulics is limited to helping build Rose Floats for Cal Poly Pomona in the late 1960's: to rebuilding and repairing 3 hydraulic wood splitters over the last

40(?) years. In other words, I'm not an expert on hydraulics.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Were transistors or semi-conductors also around back then? Incidentally, I know little about science, math and technology, so you know: I'm just curious.

In 1939? No.

--
"I am a river to my people." 
Jeff-1.0 
WA6FWi 
http:foxsmercantile.com

I know little about science, math and technology, so you know: I'm just cu rious.

Yes:

Diodes were the first semiconductor electronic devices. The discovery of cr ystals' rectifying abilities was made by German physicist Ferdinand Braun i n 1874. The first semiconductor diodes, called cat's whisker diodes were ma de of crystals of minerals such as galena.

An accurate, but totally useless answer that you cut and pasted from:

Transistors weren't invented until 1947.

Generators were in use until the '60s, and mechanical regulators were in use up to the 70's because prior to that they didn't have reliable diodes and transistors.

So I repeat, in 1939, no.

--
"I am a river to my people." 
Jeff-1.0 
WA6FWi 
http:foxsmercantile.com

In cars, Rambler had alternators with solid-state voltage regulators starting with the 1964 models. (It was a Motorola system.)

--

----------------------------------------------------------------------------- Roger Blake (Posts from Google Groups killfiled due to excess spam.)

NSA sedition and treason --

Don't talk to cops! -- Badges don't grant extra rights --

-----------------------------------------------------------------------------