Amulet excavator thumb

[brain55]

I couldn't decide which forum to post this in. I finally decided it was more of a welding job than anything for me. Anyway, I ordered an Amulet thumb for a customer's Caterpillar 305 CR excavator Friday. They have to build it and ship it to me. I expect to see it the coming Friday and put it on Saturday. I will definitely post pictures before, after, and during. It should be a fun job. The hydraulics are already on the machine so all I really need to do is weld the brackets for the cylinder and thumb, mount them, and make the hoses to the cylinder.

I quoted my customer $3000 for the job.

Brian.

 

[firemanmike69]

Make sure to tack everything up and test fit it first, we just got the wrong size thumb from them twice. Looking forward to your pictures buddy

 

[brain55]

I definitely will tack and test first. Especially since it is my first time installing a thumb that wasn't a factory kit.

Brian

 

[Arc weld]

There should be instructions for welding the thumb brackets on. If it uses separate small brackets for the cylinder and thumb hinge pins, they can be welded all around. If it uses a large mounting plate with the cylinder and hinge mounts already attached, only weld on the sides lengthwise with the stick/boom. Don't weld across the top and bottom (across the width of the stick). That's an application where you could use Shield Arcs suggestion to put silicone seal across the boom to keep moisture from getting under the plate.

 

[TomSeller]

If it uses a large mounting plate with the cylinder and hinge mounts already attached, only weld on the sides lengthwise with the stick/boom. Don't weld across the top and bottom (across the width of the stick). That's an application where you could use Shield Arcs suggestion to put silicone seal across the boom to keep moisture from getting under the plate.

I have welded a little but in no way am I a welder. Why wouldn't you weld all the way around?

 

[brain55]

There should be instructions for welding the thumb brackets on. If it uses separate small brackets for the cylinder and thumb hinge pins, they can be welded all around. If it uses a large mounting plate with the cylinder and hinge mounts already attached, only weld on the sides lengthwise with the stick/boom. Don't weld across the top and bottom (across the width of the stick). That's an application where you could use Shield Arcs suggestion to put silicone seal across the boom to keep moisture from getting under the plate.

These are the welding instructions I have so far. We'll see if they send any more with the thumb.





Brian

 

[Arc weld]

I have welded a little but in no way am I a welder. Why wouldn't you weld all the way around?

It would add stress to the stick welding straight across it. The instructions show curved ends and also to leave a space un-welded in the middle. I'm sure Shield Arc could explain it better than I could.

 

[Coyote machine]

I hired a pro welder to attach the cylinder bracket plate to the dipper stick on my tractor's subframe mounted backhoe. The instructions for the weld process were quite detailed and clear. they said to fit the thumb onto the hoe and gave an area in which to locate the plate. They said to clean all paint from the weld area, to dry fit the plate and test the fitment before welding. We did this and then tacked the late to retest actual fit. Once verified, we welded ONLY along the sides of the plate and stick, NOT across as clearly stated in the directions.
We took the extra precaution to remove the battery ground during the process so no damage from the welding could carryover to the tractor's electrical system.
The work cost $150, and took a couple of hours to complete from start to finish. The results are good.

 

[Shield Arc]

I have welded a little but in no way am I a welder. Why wouldn't you weld all the way around?

Generally the reason is stress raiser. And the HAZ / Heat Affected Zone. That's why you see in really stressed area where fish plates are required, engineers will want a diamond or oval shape fish plate. With diamond shape fish plates its a good idea to tail out the weld like in brain55 weld detail he posted.

Stress concentration - Wikipedia, the free encyclopedia

 

[TomSeller]

Generally the reason is stress raiser. And the HAZ / Heat Affected Zone. That's why you see in really stressed area where fish plates are required, engineers will want a diamond or oval shape fish plate. With diamond shape fish plates its a good idea to tail out the weld like in brain55 weld detail he posted.

Stress concentration - Wikipedia, the free encyclopedia

Makes sense. Thanks