Let's talk grapples!

[rusticretreater]

What you call a diverter valve is usually called a third-function valve.

As for your electric driven thumb, I think your main problem would be insuring you have enough amperage to run it, keep your battery charged and not burn out the alternator.   Activating the motor would require a robust switch/relay setup that will stand up to outdoor duty.  And of course, the fuses to protect the system.

Then there is the driveline hookup from the motor to the thumb itself.  You will likely need a chain and pulleys to multiply the torque of the electric motor. Another requirement is a way to keep that lubricated and protected from the elements.

Also, rain/snow/sleet might be an issue if you do work in that kind of weather.

[beenthere]

Potentially silly question- I like the idea of the Thumb to add to my existing Artillian pallet forks on my JD 430 Loader.  But I only have the loader arms up and curl hydraulics so I would need a diverter valve and a bunch of new hoses and other hardware.  So I was also thinking about the post from davch00 and thinking of building my own.  In doing so, I was thinking it might be more straightforward to build something with an electric actuator instead of a separate hydraulic cylinder.  That would eliminate the need for the diverter valve and the extra hydraulic hoses and fittings.  I'd already have to do wiring to a switch for the diverter if I went that route, so I call the electric wiring a wash.  And I would be able to remove the thumb by just unplugging an electric connector instead of the hydraulics.

A quick search on ag-rated electric actuators yields some results from TiMotion - I'm sure there are others - but their MA3 series says it has maximum force of 16,000 Newtons or about 3,500 lbs, and is rated for washdown.  Haven't done the design yet to see if that would be sufficient.

Any thoughts on this approach?

alecs
After getting The Thumb, I have considered doing just what you are thinking. Even though I have already plumbed in the hyd lines through the 430 loader frame to The Thumb hyd. cylinder. I was looking at the actuators listed on Surplus Center. Think I calculated that The Thumb would work adequately well holding brush and logs with enough force to do the job.
Now my 3rd function valve that I added is used to move the hyd. cylinder on my top arm, but have to switch lines over to The Thumb when it is mounted (most often on the forks). Have considered an electric diverter valve from Surplus Center but it would be a very tight fit, and haven't been brave enough to try to fabricate it in there. Would be convenient, but the linear actuators is an easier alternative (maybe)..

Like your approach, and look forward to the results if you follow through with it.

[alecs]

What you call a diverter valve is usually called a third-function valve.

As for your electric driven thumb, I think your main problem would be insuring you have enough amperage to run it, keep your battery charged and not burn out the alternator.  Activating the motor would require a robust switch/relay setup that will stand up to outdoor duty.  And of course, the fuses to protect the system.

Then there is the driveline hookup from the motor to the thumb itself.  You will likely need a chain and pulleys to multiply the torque of the electric motor. Another requirement is a way to keep that lubricated and protected from the elements.

Also, rain/snow/sleet might be an issue if you do work in that kind of weather.

I was thinking of an electric powered cylinder that would connect mechanically just like a hydraulic cylinder.  I looked at the specs on these and the amperage is proportional to the force that it is exerting, so the high amps (about 20) would only happen when you are really clamping down on something.  Otherwise, it's very low amps when you are only retracting or extending with no force.  The speed of the device is also proportional to force, so it would move quickly when you start and then slow down under a load.  Might be hard to feather the position.  I think the duty cycle is certainly low enough for the battery/alternator to handle it.  The unloaded amperage is similar to having the headlights on and the full load amperage wouldn't be that much different than the starter motor in terms of load.  The cylinder I looked at was IP rated for washdown/pressure washer so I think it would be rugged enough.  I just need to find out where to buy one (and how much $)

This was the first google result I found - not settled on this particular model, just something along these lines.

https://www.timotion.com/en/products/linear-actuators/ma3-series

[rusticretreater]

That's a pretty cool device.  I immediately was thinking again about the alternator and available amperage.  While it is only a periodic spike in amperage usage when activating the actuator, if the alternator is repeatedly pushed to an upper limit it will certainly burn out.

So, I would find out the ratings for the alternator.  Pay attention to output at certain rpms because you won't be running things wide open.  At those mid range rpms, turn on all the electrical devices and measure the amperage output of the alternator.

Add in the amperage required for the actuator(according to the chart it will be around 20 amps) and see if the alternator can supply that level of amperage.  Then subtract 10% from the alternators rated output and check that it is more than the required amperage.  If not, your alternator could be pushed to the limit and generate heat and probably burn out a diode or two if you do night work and use lights, etc.  At least you will know what is going on with the system.

This might be a bit much for some folks, but I like to figure these things out.

[beenthere]

I was looking at the 12v linear actuators at Surplus Center, in particular the ones with 8" stroke. 

https://www.surpluscenter.com/shop.axd/Search?keywords=linear+actuators&page_no=5&fq=1_category:1787

Did not think about the load on the alternator, but certainly would be a serious consideration. 

[alecs]

beenthere- I was looking at some similar actuators but found that a lot of them were designed for things like hospital beds, power recliners, and adjustable height desks.  I worried they wouldn't be rated to leave outdoors on the tractor.  There was one on the link you sent that was rated at 1000 lbs force and IP65 water resistant.  That might be the best bet. 

In designing the linkage, I want to optimize the relative lengths and positions of the actual thumb (on one side of a pivot) and the part where the actuator connects on the other.  if the distances were equal and opposite one another, 1000 lbs on the actuator would be 1000 lbs clamping force.  But if the grapple thumb is 5x longer than the arm that the actuator attaches to you'd only get 200 lbs clamping force.  Not sure what the required force would be.  For just holding a pile of brush it would be a lot less than if you were trying to set a log on a mill in the "limp wrist" position with the loader frame curled all the way down.

I'll keep looking into this and see.  Whether hydraulic or electric, I think the design of the thumb would be essentially the same.

[alecs]

rusticretreater- The way I was thinking about it, if the 20+ amp load of the actuator occurred for 5 seconds out of every cycle, even if you were grabbing a log and clamping the heck out of it every 5 minutes, that's only 1/60th of the time.  So your average amps would be 0.33, well within tolerance for the alternator.  Even every one minute, that would be only 1.67 amps.  So if the alternator didn't have 20A to spare, it would momentarily draw from the battery and then the battery would be replenished between cycles.  

Are you concerned that's not the right way to think about it?  I agree if the load were continuous you'd be in danger of frying the alternator, but seems like a brief peak load wouldn't be a major issue.  

[beenthere]

were trying to set a log on a mill in the "limp wrist" position with the loader frame curled all the way down.

First off, I would never think of using a grapple to "set a log" on a mill. Too many things can, and likely will, go wrong no matter how tight a grip one thinks they have on that log.

[beenthere]

Saw this in the "jokes" thread, thought it might help here in this grapple thread.

https://www.instagram.com/constructionvidz/reel/C3kZDAyAwN0/

[newoodguy78]

I've been doing some poking around for excavator attachments lately and stumbled upon a mechanical grapple made by Westendorf. 
After watching a couple videos they seem like they might be a budget friendly idea for what seems like a fair amount of people on here with the compact/smaller tractors without hydraulics looking to install a grapple. 
I have no firsthand experience with these whatsoever but not requiring a third function install keeps a fair amount of money in the purchaser's pocket. 

Fully hydraulic grapples are incredibly handy for sure and tough to be without once you've run one. That said seems like with a little seat time someone could get quite efficient with a mechanical one. 

[alecs]

The mechanical grapple looks pretty useful and the simplicity of no additional hydraulics or wiring is pretty cool.  Anyone have experience using one?

[OlJarhead]

I asked about the. on tractorbynet and decided against them myself.

[rusticretreater]

Interesting.  I notice how they label it a brush cutter, not a root rake grapple.  You don't have real control over the bottom teeth except at certain angles as the lower teeth dangle.   While much better than no grapple at all, it does look a bit clumsy at times.  Doing some accurate log picking from a pile would be a bit difficult IMO.

[Buickal]

I don't have a mill (yet) but I went with a grapple attachment for the front end loader on my Kubota 7040 and have a 3pt pallet fork attachment on the back for moving pallets (one pallet has a fuel tank on it, 2 pallets with 300 gallon water tanks, one pallet has a box on it for carrying miscellaneous stuff).  I've carried lumber on the forks to build hunting blinds.  Just used a ratchet strap to secure it.