What length of thumb for a PT mini-hoe?

[KentT]

Since the most use my PT has gotten is with the minihoe grubbing brush and the grapple bucket piling brush, I'm seriously considering buying a thumb kit and having it welded on...

What size do I need? Could I impose on someone to measure theirs? (I can't readily measure mine, since it's currently 900 miles away. )

A guy on eBay is selling them in 16" and 20" lengths... I'm guessing the 16" would be the best fit...

16" Adjustable Thumb

Ideally, it would be nice if one pin position would allow the thumb to go inside the bucket, while a different pin position allowed it to meet the bucket teeth... The excavator that cleared my land had his adjusted to go inside the bucket -- he could snap 12" pines into pieces like breaking toothpicks... or, more gently grasp them so firmly that they couldn't slip.

Also, I think I'll have some gussets welded on the boom, to avoid Sedgewood's experience. With a thumb, it would be SO EASY to overstress the boom to QA plate's butt-weld mounting...

Thanks in advance!

 

[BobRip]

I will measure mine Sunday afternoon and get back to you.

Bob Rip

 

[KentT]

Thanks, Bob. That would be super!

 

[Sedgewood]

<font color="red"> Also, I think I'll have some gussets welded on the boom, to avoid Sedgewood's experience. With a thumb, it would be SO EASY to overstress the boom to QA plate's butt-weld mounting...
</font>

Alas the weakest weak point wasn't a lack of gussets thought that runs a close second. It was the thin wall (1/8 inch) tubing PT made the boom from. You can see that in addition to the kink in the boom near the gusset that the whole length of the boom has a gentle bend in it. The replacement boom is 1/4 inch wall. You might want to reinforce the boom as well as the gussets.

My home-made thumb is arranged so the tip just clears and goes into the curling bucket. This has worked well. I thought when I built it that I might need to remove the thumb to dig but I never have. As long as I'm careful not to pack the dirt into the bucket with the thumb it digs fine with the thumb in place.

I'll go out later and measure the thumb.

Here is a link to my minihoe web page.

Sedgewood

 

[Sedgewood]

Here's a picture of the relationship of the bucket to the thumb on my minihoe. The distance from the heel of the thumb to the nearest point on the boom is approx. 11-1/4 inches. The heel of the thumb just scrapes the inside of the bucket as it curls.

I put up a couple more pictures on my web page, one with the bucket fully curled and one showing the point where the new boom is welded to the quick attach. My memory failed me on this one. I thought some extra gussets had been added but that's not so. The welder just replaced the tube using the original gussets. It's held up fine. It was just that silly thinwall boom that wouldn't take the "grab-it-and-growl" abuse the thumb encourages.

Sedgewood

 

[KentT]

Thanks, Sedgewood. Those additional pictures and the added description are VERY helpful, especially with the reinforcing you had done.

I wonder if the lighter weight of my PT-425 will prevent stressing the mini-hoe like yours? The PT pucker will likely set in before I can stress it too much going up or down -- it's the twisting, side (lateral?) forces that concern me most...

Without replacing the tube itself -- like you did -- I'm wondering how much reinforcement would be added by "scabbing on" angle-iron to the corners of the tube and in beefing up the gussets, as shown in this pic in red and blue.

Reinforcing the Minihoe

Do you think these types of reinforcement would be enough -- remembering that the 425 will pucker much quicker...

 

[BobRip]

I took some pictures and the number I got was about 12.5 inches. The first picture shows the bucket and angle of the bucket (pretty much 90 degrees from the boom.

Bob Rip

 

[BobRip]

This is a close up to show the ruler.

Notice that the second tooth is bent out. I measured from the first tooth.

Bob Rip

 

[KentT]

Thanks, Bob -- that helps a lot. I'll see if either of the guys selling these on eBay will consider building a shorter version.

 

[J_J]

The size would depend on what you want to do. If you want the tip of the bucket to touch the tip of the thumb for picking up objects you would get the size as your picture. If you want the bucket to roll past the thumb, you would get a shorter thumb. They also make adjustable thumbs. This is the adjustable thumb that I built from a kit. It is also foldable.