Howard:I happen to think that a 500 pound furnace full of molten metal falling uncontrolled is a "real" problem. Besides I was responding to a question from Jeshua about power failure. I would think you would have pointed this out and provided the solution in one of the first posts on this topic. Instead a person with no hydraulic experience had to figure this out. Two or three years from now somebody reading this may try and build one of these without your 30 years experience helping. Thanks to me they are now aware of the need for a lock valve. I think they need to know both the advantages and the disadvantages of the system before they start the project. Carl
From: Stonetool <owly@...
Sent: Sunday, August 14, 2011 10:05 PM
Subject: Re: [hobbicast] Ok, I'm old and brain dead
There are countless scenarios with any system...of things that could go wrong. This one has a very simple and reliable solution. All it requires is a hydraulic lock valve. Presumably you will be using a double acting cylinder. The lock valve requires pressure on one side to allow flow on the other. In other words the load cannot come down unless you have hydraulic pressure. It's a simple common component, and inexpensive.
It's clear that you really are determined that this is not the way to do it....... I'm not going to waste any more time on this ........ There is a distinct difference in approach between someone determined to find real problems and address them, and someone simply determined to find reasons why something will not work. The servo approach WILL work fine..... It is used in numerous applications, and can in this one. I've endeavored to address all of your concerns, and there are solutions to all of them. I've explained the advantages of this system as clearly as I can......... It's up to you now. I've said all I'm going to on this subject untill and unless someone actually intends to build one ..........
Sent from my iPad
On Aug 14, 2011, at 2:05 PM, Carl <carl_r2000@...> wrote:
> Jeshua:It takes about 20 pounds of force to turn the wheels on a power steering car if it the wheels are off the ground. It doesn't matter if the engine is running or not. If your 500 pound furnace is tilted up and the power fails you will have about 20 pounds of force holding it up. 500 - 20 = 480 pounds of downward force. It is going fall fast. The same thing will happen if for any reason you let go of the control lever for a second. Carl
> From: Jeshua Lacock <jeshua@...>
> To: email@example.com
> Sent: Sunday, August 14, 2011 8:17 AM
> Subject: Re: [hobbicast] Ok, I'm old and brain dead
> On Aug 14, 2011, at 9:07 AM, Stonetool wrote:
>> You seem to want to find problems where they don't really exist..... While it is true that you have to hold the handle or the furnace will return to the upright position, the fact is that you are either pouring or not pouring. It is difficult to imagine a situation during a pour when you would want to simply freeze the position and walk away...... The fact is that when you pour metal you want continual pouring, and need to regulate flow constantly as the as the level in the crucible drops....... In any case it would only take a little friction on the handle to make the furnace remain when you let go of the handle. It will take almost no force to hold the furnace up, so the only friction needed is slightly more than what it takes to hold the handle up.
>> With any project of this type, there are numerous piddly details to address as you design and build. I tend to dismiss them ..... They crop up as you proceed, and are a part of the process. There are no 800 lb gorillas here ..... nothing to make this system impractical or unworkable, or particularly difficult. This system has significant advantages over a plain valve and control in that it offers easy fine tactile control ..... a conventional valve does not due to the dead space, and difficulty of achieving exact motion. The best analogy remains steering a car. Your car gives precise, accura
[Non-text portions of this message have been removed]