Backhoe thumb pins?

[Johnny Glenn]

Thanks for looking in - I've just finished fabricating a thumb for my backhoe but on the first try out - the 1 1/4 steel pins bent. Not sure what type of steel they are but certainly not strong enough. What type of steel should I look for? Thanks

 

[Taylortractornut]

I buy bent hydraulic rams at the scrap yard. If they had bad bores or something is wrong beyond repair Ill use the rods as pins. THe 1 1/4 pins on my 12500 pound excavators thumb are made from these and I have never bent one.

 

[David Devuono]

Got any pictures of your design?

 

[mrmikey]

Got any pictures of your design?

Ditto, it'll take a lot to bend an 1 1/4 pin, I'm wondering if the geometry could be doing it....Mike

 

[LD1]

Got any pictures of your design?

Ditto, it'll take a lot to bend an 1 1/4 pin, I'm wondering if the geometry could be doing it....Mike

Yep. Pics are worth a thousand words:thumbsup:

 

[J_J]

Johnny Glenn,

Can you show us a close up pic of your thumb assembly with cyl attached?

How far apart were the cyl support/mounting tabs, and how wide was the cyl ends. If you put a lot of pressure on the center of a long pin, you could expect it to bend under the right circumstance.

Did you have a clevis, cross tube, or swivel eye on the cyl end.

 

[wdchyd]

Shy of buying hardened 4140 steel material for pin stock, Taylortractornut is right on with the used hyd rods......you won't find any good steel at normal steel places....if you used hot rolled steel or cold rolled 1018 (better but not good enough) then it's not strong for pins....

the rods used for hyd use is pretty good stuff.....

also regarding the geometry...if the ears on your pin bosses are too far apart then the column strength will be compromised and pins will snap.....

Column strength is like comparing snapping a full length pencil in your hands vs snapping a short piece of the same pencil in your hands....

 

[20 20]

without pictures it's hard to imagine what you have. With that said a bent pin is better then something else breaking, allways have to look at the bright side