BH77 - has anyone considered converting mechanical thumb to hydraulic?

[briandantz]

I will do a photo shoot tomorrow AM. i was buying a DRO for my mini mill. Told my dad. He was curiously interested. he is still machining at the ripe old age of 80. getting hard to read the dials, so i bought a 3 axis unit on Ebay for $475 shipped. installed it Thursday and friday evening, finished this morning. really nice unit. He thought he was he was paying for it. I blurted out "Happy Father's Day, and clean up the mess, old man"! Bolted out the door before he could say anything.

I love a good surprise.... i will post some stuff tomorrow.

Here ya go!
https://www.youtube.com/watch?v=YTQwA6k1fK8&edit=vd

 

[wdchyd]

Your gonna love the DRO Briandantz......it'll cut your time in half on any setup time and projects with dimensions

Don't know if you have tried this yet but there are charts (machinist handbook) for jigboring round bolt circle patterns..... you can dial in many different bolt patterns with the help of a DRO....works slick

 

[bumperm]

When I "hydraulicized" my BH77, I used this cylinder as it has adjustable ports: http://www.baileynet.com/product/19560

It has exactly the right stroke, but overall length is about 1" too short. As such, when the thumb retracts all the way it contacts the body of the cylinder when there is almost a inch of travel left in the ram. Today I removed the cylinder and cut off the cylinder end sleeve, welded in a 0.900" spacer (and while I was at it, repositioned the zerk fitting so it is on the distal end of the cylinder and easy to reach). Now travel of the thumb and clinder is just perfect. Fully retracted, the thumb is about 1/8" away from the cylinder body. Fully extended, the rod is about 1/8" away from contacting the dipper itself - - so travel is full in both directions without anything bonking anything else. Whoopie!

Just got my Bro-Tek ripper today. Haven't had a chance to put it on to try it out . . . will do that tomorrow and add results to appropriate thread, It does look good though.

 

[briandantz]

When I "hydraulicized" my BH77, I used this cylinder as it has adjustable ports: http://www.baileynet.com/product/19560

It has exactly the right stroke, but overall length is about 1" too short. As such, when the thumb retracts all the way it contacts the body of the cylinder when there is almost a inch of travel left in the ram. Today I removed the cylinder and cut off the cylinder end sleeve, welded in a 0.900" spacer (and while I was at it, repositioned the zerk fitting so it is on the distal end of the cylinder and easy to reach). Now travel of the thumb and clinder is just perfect. Fully retracted, the thumb is about 1/8" away from the cylinder body. Fully extended, the rod is about 1/8" away from contacting the dipper itself - - so travel is full in both directions without anything bonking anything else. Whoopie!

Just got my Bro-Tek ripper today. Haven't had a chance to put it on to try it out . . . will do that tomorrow and add results to appropriate thread, It does look good though.

Hi,
Update on projects. haven't logged in recently
1) thumb... is awesome! when i built mine, i cut off welded clevises and rotated the works to get the far port at 3 o'clock. (i didn't used the one you specified because i knew i was going to cut whatever cylinder i boughts as soon as it showed up) I used the clevis tangs as a base to weld in new bushings (that's where i "added" my length to 19 1/4" closed plus 8" stroke) leaves 1/8" gap when fully retracted. i have to thank you again for your and DFK's ideas.
2) DRO's... Dad loves his new DRO OMG!!!
3) Rear remotes. Have parts for one tractor. Shelved this until firewood id done
4) Firewood. need to cut. split and stack 1/2 cord a day for the next 8 days, then i am done. Thumb is HUGE with firewood.
5) Miller 330ST Aircrafter. Blew SCR pack in current control section. Cried a little. looked at prices of replacement unit of similar or better quality. Pulled myself together) Got out meter and diagnosed. bought used replacement on Ebay and installed... Frankenstein lives again!!!
6) Built Wireless DRO project and installed on Enco Mini Mill. Android app runs on your phone or tablet and connects Bluetooth to the milling machine. Very cool... i will post a flick of this on my YouTube page shortly. i have X and Y up and running for south of $200 bucks, all in...

 

[bumperm]

Hi,
Update on projects. haven't logged in recently
1) thumb... is awesome! when i built mine, i cut off welded clevises and rotated the works to get the far port at 3 o'clock. (i didn't used the one you specified because i knew i was going to cut whatever cylinder i boughts as soon as it showed up) I used the clevis tangs as a base to weld in new bushings (that's where i "added" my length to 19 1/4" closed plus 8" stroke) leaves 1/8" gap when fully retracted. i have to thank you again for your and DFK's ideas.
.

Brian,

I agree with the "awesome". However, when measuring and trying to find the optimal cylinder for the thumb (this converting the Kubota mechanical thumb on a BH77 hoe), I measured 10" stroke as being optimal, as 10" stroke allows all the available travel of the thumb, full retract and full extension. If using an 8" stroke cylinder, you are forced to sacrifice one or the other - - most likely on the extension side. If using a longer than 10" stroke, somethings going to bang in one direction or the other - however, an 11" stroke would work with a 1" long mechanical stop on the rod to limit retraction. Couldn't find a suitable 11" anyway.

Using an 8" stroke means 2" less extension which equates to a lot more than 2" of thumb movement due to geometry and leverage. And while that doesn't strip away much of the thumb's functionality, it does limit some of its ability and dexterity in grasping objects in some positions. For some tasks. e.g., when using the thumb to pluck out long tap root plants such as sagebrush, and to grab and rip out saplings, the reduced range of thumb motion would at times be ackward. Also in some apps the additional thumb extension or travel increases the size of the work area without having to move the tractor. Not so much affecting the far reach, but mostly allowing use with more convenience (or dexterity) up closer to the tractor.

bumper

 

[briandantz]

Brian,

I agree with the "awesome". However, when measuring and trying to find the optimal cylinder for the thumb (this converting the Kubota mechanical thumb on a BH77 hoe), I measured 10" stroke as being optimal, as 10" stroke allows all the available travel of the thumb, full retract and full extension. If using an 8" stroke cylinder, you are forced to sacrifice one or the other - - most likely on the extension side. If using a longer than 10" stroke, somethings going to bang in one direction or the other - however, an 11" stroke would work with a 1" long mechanical stop on the rod to limit retraction. Couldn't find a suitable 11" anyway.

Using an 8" stroke means 2" less extension which equates to a lot more than 2" of thumb movement due to geometry and leverage. And while that doesn't strip away much of the thumb's functionality, it does limit some of its ability and dexterity in grasping objects in some positions. For some tasks. e.g., when using the thumb to pluck out long tap root plants such as sagebrush, and to grab and rip out saplings, the reduced range of thumb motion would at times be ackward. Also in some apps the additional thumb extension or travel increases the size of the work area without having to move the tractor. Not so much affecting the far reach, but mostly allowing use with more convenience (or dexterity) up closer to the tractor.

bumper

this is weird. i am going to remeasure the kubota linkage. something doesn't jive here.

 

[CDN Farm Boy]

I'm with bumper, it's a 10" stroke cyl you need. At full extension there is about 1/4" clearance before the rod touches the tip of the dipper boom and at full retraction the thumb just contacts the body of the cyl making for the tightest possible storage.

If I remember right from 2 yrs ago, 8" is close to the stock linkage allowance but 10" fits much better and is the right lenght off the get-go. Don't measure the linkage, measure the maximum possible travel of the thumb itself.

See 4th post on page 9 for my setup.

 

[bumperm]

I'm with bumper, it's a 10" stroke cyl you need. At full extension there is about 1/4" clearance before the rod touches the tip of the dipper boom and at full retraction the thumb just contacts the body of the cyl making for the tightest possible storage.

If I remember right from 2 yrs ago, 8" is close to the stock linkage allowance but 10" fits much better and is the right lenght off the get-go. Don't measure the linkage, measure the maximum possible travel of the thumb itself.

See 4th post on page 9 for my setup.

I think you're on it . . . the stock mechanical linkage doesn't allow full thumb extension travel. I also measured the actual "throw" of the thumb to come up with a 10" stroke and ended up using this one, $177 from Bailey Hydraulics: http://www.baileyhydraulics.com/product/19560
primarily as it has a unique capability, with two ports at 90 degrees from each other on the cylinder end (one has a plug so you choose which to use), while the rod end of the cylinder has a rotating gland so you can position that port however you want.

The cylinder is "almost" perfect. There were two things to mod. The collapsed length comes up about 1" too short, so I cut off the cylinder end sleeve and welded in a .9" spacer. This was just tack welded at first, so I could mount that end and then muscle it into perfect alignment on the tractor bracket - as near as I can tell, the upper dipper bracket for the thumb linkage was just a little off alignment on my hoe - the slightly too short spacer allowed for some wiggle room in alignment. I did not disassemble the cylinder, just drained it, extended the rod all the way, and wrapped a wet rag around end before welding the spacer and sleeve back on. This also allowed me to reposition the zerk fitting so it's more convenient.

Having a thumb, even a mechanical one, is a huge plus - opens the hoe up to a whole nuther world of use and convenience. And having it hydraulic is SO much better than mechanical. Kubota is really missing the boat on not offering a hydraulic thumb as an option on all their hoes.

 

[briandantz]

I checked the old linkage because I originally started with a 2" x 10" cylinder in my plan, the old Kubota linkage had 9" travel. I sacrificed 1" of travel but I had to ponder this a moment to figure out why i did this (this was 2 months ago). I want BOTH ports on the side, which forced me to start the cylinder farther away from the factory clevis mounted on the dipper so the port would be clear of the factory bracket. my setup is 19 1/8" closed and 27 1/8" extended. Going to a 10" would have made the retracted length too long (21 1/8") because of the extension I installed on the fixed end (thumb would not store flat).
I also had concerns about the rod hitting the cross brace on the thumb when extended if i used a 10".

I knew this going in, though. All good.

I attached 3 photos. extended, retracted and clearance between thumb and cylinder when retracted.

It's super cool. Anyone without a hydraulic thumb is being deprived of it's full capability. Great for firewood processing too.

 

[bumperm]

Probably would be easier to compare if I had a regular bucket mounted rather than the Bro-Tek ripper tooth, but if you compare the thumb angle to the dipper, you can see what full thumb deflection looks like with the 10" cylinder I'm using. The last picture shows the location I settled on for the solenoid switch. This position offers the most protection for wiring and switch, absent a shield. I may install a shield later, welding mounting tabs for it to the dipper stick as it will need to be removable to service other parts. However, this location does offer substantial protection without a guard - - unless you try real hard to bonk it!

BTW, I like the Bro-Tek ripper a lot and will do a separate review on it later.