So I am looking at purchasing a 13t excavator for general farm use and want a thumb but also want a machine that can run aux. attachments. In looking at different machines some come with dedicated aux. line with either full flow(assuming from main pump) to a defined gpm on the aux. line. Other machines that have a thumb show no aux. line even available from the manufaturer so is just another spool valve added for the thumb from the main pump and what are the limitations to that for running aux. equipement. Any advise or info is appreciated.
The Japanese machine used to all come with an extra valve spool which could be used to run a thumb or other type of attachment. The extra circuit could be two pump or one pump. The smaller machines sometimes only had one pump but the valve could take the entire flow from that one pump or a metered flow which essentially was about the same as a single pump in a two pump system. What you can run for attachments will depend on the amount of flow you can get to the end of the stick. Now days the manufacturers are looking for ways to reduce the cost of the machine and increase the revenue that might be obtained on a sale so they are dropping that extra valve from the standard machine and making it a costly option you have to purchase. Some machines now also have an option called combo hydraulics. Basically they y off one leg of the thumb circuit with a three way valve and drop the oil directly into the cooler or the return filter in the tank. This give a low restriction return so you can run attachments like compactors and hammers. Usually when that is done and an attachment is installed you have to hold the thumb up some how so provision is made for a pin to be insert to hold the thumb to the stick. This is a short explanation. It can get really involve depending on the brand of the machine and any particular model.
Thanks every bit helps.
What machine are you looking at buying?
Been a few, this post was originally about a JD120 that has a thumb. Talked to the dealer service dept. and he figured the thumb was low flow and low pressure. Looking at a PC130-7k right now though so any thoughts on that machine is appreciated.
The Komatsu excavators with closed center load sensing have a mono block main value with the provision to add valve sections to the end of the mono block. Those sections can be either one pump or two pump flow so you have to purchase the valve that you need if they are not already installed. I have had little to do with the Dash 7 line but I'm guessing it is not a lot different than the Dash 6 line. I don't know if it is a single pump system or a two pump system. Those are questions to research before you purchase. I believe you can program pump flows and absorption torques from the monitor panel to set up your attachment.
Thanks for the info, gives me a better idea what is going on.