BH77 - has anyone considered converting mechanical thumb to hydraulic?

[broncorm]

Subscribing
I've wanted to do this since I got the tractor with manual thumb

 

[CDN Farm Boy]

I did also find a place that would do customer cylinders for not too outrageous prices - so in my mind the last big hurdle to mentally work out is the figuring out the exact right valve to use to control the thing.

Why the custom cyl? I'm using a 2" x 10" from Princess Auto and it works just fine. While I had to do slight (easy) mods to the mounting tubes, the main (expensive) parts of the cyl are still intact.

 

[ameador1]

Subscribing to this thread...

I have a Mahindra 3535 with manual thumb and thinking about modifying this to hydraulic. The info in this thread has been helpful in understanding the concerns to think about and the kinds of options to consider. Thanks for posting all this great stuff!

 

[Sysop]

Old thread, not a lot of action to subscribe to. No comments since Christmas '13.

 

[ameador1]

Old thread, not a lot of action to subscribe to. No comments since Christmas '13.

Yeah I know, but subscribing adds it to my 'subscribed threads' list - some good info in this thread. If I don't subscribe to it now, I'll never find it when I want it again...

Do you have the hydraulic details figured out on our models? As far as what lines to use, type of control units, etc...? If you have that stuff already worked out, then looking at my thumb may be the last piece of the puzzle. I figure at some point I will do this with mine - probably not until next year at best, but I want to understand this stuff better in any case. Research early you know... But hey, if you get around to checking out my setup and know how to work out the details, then maybe sooner

I think... I (you too?) have an aux hydraulic connection back there - sounds like that would help make the conversion easier.

 

[bumperm]

I'm in the wait-and-see crowd. Been using the manual thumb (which is truly amazing for plucking whole sage brush!), but do intend to go hydraulic.

I may have a partial answer for one of the concerns previously mentioned, and that is the issue of having the bucket curl, when it comes up against the thumb, over pressure the backhoe or tractor hydraulics upstream when it acts as the master cylinder. A pilot controlled check valve, installed at the thumb cylinder will lock the cylinder, isolating the cylinder hydraulics until the thumb control valve is activated. This doesn't stop the thumb cylinder itself from being "overpressured", but I see this as less of a problem or issue.

When building the top and tilt for my 3-point, the top cylinder (from SurplusSales) already came with DPCV, I added a single PCV to the tilt cylinder to solve the "creep down" issue.

bumper

 

[Sysop]

The hydraulics typically used on these backhoes for the thumb is just a diverter valve plumbed into (I think) the curl function, with a footswitch control.

 

[bumperm]

Sysop, going with a diverter has appeal (fairly simple), but the downside is one cannot have both the thumb and curl closing or opening at the same time, as one's thumb and index finger would. Also, the deck on my BH77 doesn't offer much foot room to add a switch, though I'm sure it can be done.

In any case, there are other options, especially if the tractor already has additional rear hydraulic function valves, or an additional spool can be added to the hoe's valves (not likely with the BH77). In my case, I have rear hydraulic valves for top and tilt as well as a joystick electric controlled 3rd function valve for the loader. The latter could easily be used for the thumb by running the hydraulic lines back to the hoe and by paralleling the two buttons on the loader joy stick.

bumper

 

[ameador1]

Yeah, I can see how having the bucket and thumb move at the same time would be nice. Moving logs around would have been extra nice being able to do it that way. But I suppose if only one at a time were able to move, it would just be a little more work. Not too much of a big deal. I assume the diverter mentioned is like a selector? You choose path A or path B for the hydraulic fluid to flow, so you would either be controlling the bucket, or the thumb? So, the pedal moved one way would be path A, and moved the other would be path B? If so, what if it is in the middle? Do you get 50% to both paths?

 

[Sysop]

Actually in most instances you don't operate both at once on these smaller units with less hydraulic flow. You either set the bucket against the item and pin it with the thumb, or vice versa. Most I have seen operate their backhoes no differently than if they had a mechanical thumb. But being able to adjust the thumb from the operator's seat versus climbing down and adjusting pins is well worth the investment for many.