I finally had a chance to use my Mini Ex, a Yanmar 35-5 with a hydraulic thumb. I'm new to the excavator world but I think I was born to play in the dirt! My question is this: When I close the bucket on the thumb the bucket hydraulics will force the thumb to retract. Is this normal? Does the bucket have more force that the thumb? Does this cause any problems? If a person was lifting a large rock would you have to keep the pressure on the thumb to keep it from letting go of the rock? I guess when I find some rocks to lift I'll find out but if someone with experiece could chime in that would be great
Ahhh, lucky you! Other operators have experienced the opposite when they "roll the bucket into the thumb"...the thumb doesn't give and they bend the rod on the thumb cylinder! The bucket should have more force than the thumb. The bucket needs this force for digging. Likewise, any hyd thumb is not going to have a cylinder that can withstand the force created by the bucket, that's not what it's designed to do. Ideally, the thumb circuit should have a relief valve that will allow the thumb to retract when the bucket is rolled into it with sufficient force, whether it's just the bucket or with a rock in the bucket. The proper way for you to operate the thumb is grip with the thumb and not the bucket. It's like this; you want to pick up a large rock, you position the rock in your bucket, then drop your thumb to grip the rock without any more positioning with the bucket. Now it's possible the relief setting of your thumb is too low. I have no idea what your thumb relief pressure should be, but I think it's safe to say that if you grip a rock as noted above and the thumb won't hold it, you could probably stand to increase the relief pressure a bit, but it would be nice to find out what the machine's relief spec should be.
G,day upnover. Exactly what ATCO said!. Can you post some pics of your thumb and the machine. I'm not far off ordering a thumb for my 27-3. I would really appreciate any pics you can get.
Sounds like your thumb has been set up correctly or maybe slightly under powered but either way this is better than a wrongly configured thumb which as ATCO said allows for a bit of operator flexibility!!!! I would say as long as the thumb holds a load under adequate pressure to prevent safety issues then leave it alone.
Exactly! +1
http://www.agwaymfg.com/ami/utility/miniex/thumbs/stickpivot.php The above link is to the manufacturer of the thumb and my buckets. Seems like it is very good quality stuff. I have pics on my other PC which is at work. I'll try and post in the next few days. I never thought about bending the thumb cylinder, that would have hurt $$$. I think I better try it first on some rocks or logs before messing with any relief valves. Great to have experts help, Thanks for the replies.
Thumb pictures Finally got pictures of the AMI thumb on the 35-5
Looks like a great bit of kit - especially as it allows you to pick up buckets which beats lugging them around by hand!!
Hey Strott: I was wondering, when you Englishmen use the word "kit," what exactly does that refer to? Does it mean heavy equipment generally? Some day you'll teach us Yanks to speak English properly. Just wondering. Thanks m8.
It is just a very general term for something usually manufactured which we use/work with e.t.c It is usually associated with machines/equipment of any size from heavy equipment to a little petrol chainsaw. e.g. a sports car could be described as a brilliant bit of kit because it handles well and goes like stink!!!!
To be a bit pedantic, the term kit in the more formal sense refers to a collection of things that go together to do a task. Such as tool kit, shaving kit, model kit. I believe that the term has a military origin and soldiers are equipped with a soldiers kit to enable them to do their job and their bag for carrying stuff is called a kit bag, hence the song "pack up your troubles in the old kit bag and smile, smile, smile". Also when a soldier is given his/her stuff the term used is to 'kit out'. However the Brits do use the term kit to refer to a singular item (which may be made up of many parts), which goes back to the military as some items where less useful than others to a soldier and as such some items where referred to as being a good part of the kit. I suppose it can be argued that the things around us are all part of a big kit that enable us to live our lives. Technically you could refer to a house as a good bit of kit but it is generally not.
Thump Wow that thumb is a "strange" thing i ve never seen something . Are this thumbs often used in the USA? Somehow i think it might be great to have such a thumb because it is ready to use in every situation. We often use this grappels, the are qucikly connectet and very moveable and useful. 90 percent of the Compact excavators in my location have a powertilt, "wrist operation" this makes the use of a thumb almost impossible. http://www.huppenkothen.com/3_produkte/produkte.php?rubrikID=38 Greets from the Mountains...
Thumbs on excavators are very handy actually. Once you use one you will wonder how you worked without it. My mini-ex has a mechanical thumb so it doesnt work as nicely or as easily but none the less it is a back saver. It works great for tearing out roots, picking up stumps, setting stones for stone walls, picking up concrete slabs, etc. I have picked up rocks 3' in diameter with ease, normally if you can get the bucket around it then the machine will pick it.