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  • Oil viscostiy recommendation please .....

    I am again over thinking a problem … but I just can't help myself, it is in my nature.

    I have stripped the mast, pump and motor from an old Raymond stand up picker (20R30TN made in 1982) and mounted them permanently as lift between the first floor and second floor. I have eliminated the reach cylinders.

    The original oil called for was Texaco Rando HD-B. I checked with Chevron and this is now Rando HD-46

    I am planning on using synthetic oil (most likely Royal Purple Syndraulic) …. unless someone can give me a good reason not to.

    My question is what viscosity? I realize the original equipment used 46 but then I started reading articles on oil (big mistake on my part).

    From what I read, external hydraulic gear pumps must be kept in the range of 12 to 300 cST (centistrokes) with 25 to 100 being optimum.

    The unit is in a controlled environment of 70 deg (say 65 to 80). It will only be used a couple times a day so the oil will not get warm from use. The circuit is designed to only run the motor while actually lifting (also I am using a flow control valve …. 4-20 mA controlled by a PLC to give a smooth start and stop …. that dumps back to the sump through a third port) so no heating of the oil from running through the relief valve. Also, since there is no longer a drive, the oil will not heat up from the power steering (which used the same sump).

    So, all this said, from the Royal Purple charts, Syndraulic 46 oil is about 129 cST at 70 deg F and 25 cST at 130 deg F. On the other hand, Syndraulic 32 oil is 83 cST at 70 deg F and 25 cST at 115 deg F

    Syndraulic 46 seems to be close to the Rando HD 46. Chevron did not have a specific viscosity chart but did send me a “ASTM Standard Viscosity Chart” and told me their oil conforms to this. According to this chart 46 oil is 120 cST at 70 deg F and 25 cST at 127 deg F.

    Both will work (I've been told this by several people) but how do I choose between the two (other than flipping a coin)? There must be some benefit of using one or the other.

    It would seem from what I have read that the Syndraulic 32 is better suited at my ambient temperatures and may protect better on start up. But this was a 30 year old machine and I am a bit worried about putting a thinner oil through a pump with wear on it. Also, even though I can't imagine the oil heating up much at all, 115 deg F is not that hot and maybe even just running it through the pump once will be enough to generate that much heat. Are there any other factors that I am overlooking?

    Any suggestions????

    Thanks …. Mike


  • #2
    Yes, you are over thinking it, Mike. Use which of the two oils is cheaper. If you're certain ambient temperature is always between 65-80 degrees, go with the 32 cSt oil. Being synthetic, it'll provide all the lubrication you could ask for, even if temperatures get hot. That being said, both oils will have excellent viscosity index, and will be a great choice. Flip that coin.

    Comment


    • #3
      Thanks so much ...

      The temperature will be right around 70 as the lift is being mounted in my house.

      This is actually going to be used as an elevator. My wife was paralyzed from the shoulders down in a diving accident at the age of 12 .... she is 37 now. We have been living (freezing when winter temperatures here in VT hit -30) for three years onsite in an old RV while we built a house. We moved into the unfinished first floor last summer. When we started designing, we got a quote from two companies. Both companies gave quotes of $15K for an elevator. Plus we found a grant for $10K if we purchased one. Since the land was ledge and we were quoted $30K just to dynamite a basement out of the ledge, $5K seemed like a good deal ... so we built up. All the finished living area (bed room, kitchen, living room, ... ) are up stairs. Last spring we got both companies in ... both now gave quotes of almost $40K .... way out of our budget! So I bought an electric forklift for $850. I stripped off the mast, pump and motor. i mounted the mast into the house. I am now working on the hydraulic controls.

      It has taken me a few months but I am finally ordering parts and starting to plumb the unit. I had a lot to learn and as you can see with my oil question, I have been overthinking every part of the system. My main pump runs of batteries and I have a back-up pump "just in case". I have interlocks on the doors and limit switches if it travels too far. I checked out the pressure drop across every valve (I had to changed them all from my original spool valves to low leak load check valves). I even calculated the flow rates and velocities in the pipes.

      I have repaired a number of hydraulic units but never designed one. I want to make sure I get it right.

      Thanks again so much for the advice on the oil.

      Mike

      Comment


      • #4
        Well, if this is for an elevator MOVING PEOPLE, I'm glad you're over-thinking it. Who is designing the hydraulic circuit for this? There are a lot of ways to get this wrong.

        Also, do you have mechanical fail-safes in case of hydraulic failure?

        Comment


        • #5
          I (with a lot of reading and help from anyone I could find on the web), have designed the hydraulic circuit. I was actually amazed at the number of ways things can go wrong.

          I actually tried to get help from local sources (well free help since I have a very limited budget). Also remember I am in VT where the largest city is only 42,000 people. The forklift people will not talk with me. They only repair exactly to factory standards so they limit their liability. I understand this as my last job was with Westinghouse Nuclear. We could not change or substitute any part unless it went through an engineering review first. There is really only one local hydraulic shop. They are part of a truck repair shop and deal only with fixing or rebuilding units. They could not answer any of the questions needed answers to.

          As you can imagine, I have had a lot to learn. This does not make me an expert by any means but I feel confident that I have designed a unit that will operated reliably and be safe.

          A great example of things I had to learn about were valves. In my first design, I used spool type solenoid valves. This seemed logical since the original forklift and my neighbors backhoe both used manual spool valves.

          They I looked at their leak rates and ability to hold loads …. ouch!

          So I changed everything to poppet type solenoid valves.

          I did know there had to what I kept calling a “hose break valve”. Took me a night to find out what I was looking for was a “velocity fuse”.

          I didn't want a “jerk” when the unit started lifting and I wanted to slow the unit as it neared the top so I found a 3 port flow control valve. I am planning on controlling this with a 4-20 mA signal from a PLC.

          I have put an over travel limit switch at the top of the lift (and using good electrical design practices, this shuts off power to the pump and does not just tell the PLC to stop …. I have seen PLC's fail).

          I tried to learn off my neighbor. He tried to do a similar lift in his barn years ago. He told me it caught fire because the motor did not shut off when the lift reached the top. I am not sure why this would have happened …. I am guessing it was in his electrical control circuit. Also this tells me that forklift motors must have a limited duty cycle. I am putting in a timer to shut off the motor if it runs for more than 2 minutes. The total lift should take less than 1 minute.

          The main pump will run off two deep cycle 12 volt batteries. This will give me power for several lifts in case of an outage. I also purchased a complete backup power unit that was designed to operate a 2 or 4 post auto lift.

          Really the only thing I don't have a backup for is the actual cylinder (wish I could find a spare … I would purchase it).

          I have interlocks on both the bottom door and the top gate. The unit will not move it either is open. The doors are “locked” so that the bottom door can not be opened if the lift is up and the upper gate can not be opened if the lift is not up.

          Even thought I have looked at this a thousand times, I appreciate anyone with knowledge of hydraulics reviewing my design and commenting on it. I am always looking for input to see if I overlooked something.

          I have attached a copy of the circuit. Would it be helpful to start a new thread labeled “hydraulic circuit for review” so that more people look at the post?

          Just as a final thought, this is a private elevator, only for my wife's use. To limit our own liability, I am not planning for visitors to use it “just for the fun of it”. With the exception of a couple of older relatives and two friends we know in wheelchairs (who have so far not come to visit us in 6 years of marriage), every else can take the stairs.

          I went through a similar exercise 7 years ago just before we were married. My wife need medical care every 4 hours so she had never traveled (returning home every 4 hours for care in a hospital bed). I had the idea (I was living in SC and her in VT) to purchase an old RV and convert it so I could do her care while on the road. I bought a 10 year old RV for $18K but was floored to find out they wanted $25K just to put in a lift. I cut a new door, designed and built a lift that slid out from under the unit so it did not take up any interior room, gutted the interior to make more room, installed a hospital bed on tracks to I could move it from side to side (to get on both sides as room is tight), designed and built an overhead track lift to transfer her from the wheelchair in the front to the bed in the back (I was quoted $10K for this lift). For both of these lifts, I used electric motors and not hydraulics. When I designed it, I had plans on using it for day to two week trips. As I mentioned, we ended up living in it so the lifts in such have been in constant use for three years.

          Here is a link to pictures of the project: https://mcsele.shutterfly.com/2299

          Thanks again …….

          Mike

          Attached Files

          Comment


          • #6
            Hmmm ... not sure why the "xxxxxxxxxs" before the web address. It should be "https"

            Thanks ...... Mike

            Comment


            • akkamaan
              akkamaan commented
              Editing a comment
              Use the Post Link-feature (chain-link button symbol)...
              I believe that xxxxxx-thing is an anti-spam-robot-thing, so if the forum gets hacked by a robot, the robot can not post functional links, it will be the way you just did...

          • #7
            Which valve is proportional? Your flow control is a symbol for a 3-port priority-type flow control, but shows no electrical control.

            I have a few comments.
            1. Your circuit is creative. Whose poppet valves are you using?
            2. Lose the hosebreak valve, 11. They're nothing but trouble. Just plumb all your valves right up to the cylinder.
            3. Is the strainer 12 part of the power unit?
            4. I think you need a mechanical lock in case of hydraulic failure. Like a pawl and notched track. The pawl could be held open by a hydraulic cylinder. If you lose hydraulic pressure, the pawl locks on the track.

            Anyway, I'd like to tell you your circuit looks good, but if you do it and fail, I don't want you to come back on me. LOL

            Who's doing the mechanical installation?

            Comment


            • #8
              Valve #3 is the proportional valve. It is a Brand Hydraulics EFC-05-24. It should dump 100% through the "EX" port till I start putting signal to the valve ( actually to the valve via a special control board that is built by Brand for their valve). By getting a bit "creative" with the circuit, I was able to use only one proportional valve. This saved me money ... the valve was $300 and the control board $500.

              I just sent out a request for prices on valves. I think I have settled on Parker. They seem to have a good reputation. I also looked at Eaton and Sun. I was told (but have not verified) that Eaton valves have a long lead time and are expensive. I looked at Sun .... they had twice the leak rate as the Parker and Eaton (both had the same). This makes me think they are a "cheaper quality" valve.

              I had been thinking about the hosebreak valve. I had read they can be a problem. I was going to set it at 9 GPM (I think this is what the original valve that was on the forklift was set at). My max pump flow is 5 GPM so I was hoping for minimal problems. I was even thinking about loading the lift with barrels of water and disconnecting the line (into a bucket) to see how fast the lift drops. The cylinder only has a 3/8" NPT port on it and may not flow much more than 10 GPM even with out a valve.

              The strainer is not part of the pump. It is a simple Cessna gear pump directly coupled to a 24 volt motor (all stock off the forklift).

              A pawl locking system is something I had considered early on. I had actually thought about it so it would make it easy to "hold" the platform at the upper location. I then got a bit worried because you would need power to retract the pawl before moving the lift. The way I have it now, assuming the lift would be in the upper location it you are on the upper floor, you can lower it with no power either by using the manual override on valve #4 or by lower lever on the back-up power unit as it is manual valve.

              I am doing the installation myself. I used pipe to roll the mast into the house and a block and tackle to stand it up. I am a machinist by trade. I have an ac welder and a mig / tig unit here. You can look at the RV project to get a feel for the work I can do.

              As I said, having worked as a self employed contractor for the past 10 years, I understand liability. Westinghouse required me to have a 10 million umbrella policy. When I started there in 1999 it cost me $2500 .... by the time I took a full time position with them 10 years later, I was paying $15,000 each year. It was one of the factors that made me take a full time position with them. Hmmmmm .... didn't think I was going to meet a woman 800 miles away, quit my job and move a year later.

              I do appreciate any advice (design, suppliers, anything, ....) !!!!!!!!!!!

              Thanks again ...... Mike





              Comment


              • #9
                Obviously adding URL links is not possible when posting Comment, only when posting Reply....

                Comment


                • #10
                  Thanks!

                  I appreciate you showing me that.

                  I don't use a lot of forums. In fact I just found this one last week.

                  Mike

                  Comment


                • #11
                  Hmmmm .... OK so I used the "link" and put in the entire URL. Instead of putting in the entire link " ....... shutterfly.com/2299" it only put in the first part and dropped off the 2299 ( which is the page the RV project shows up on ).

                  Any idea what I did wrong?

                  Mike

                  Comment


                  • akkamaan
                    akkamaan commented
                    Editing a comment
                    Mary, can you please ask why it is not optional to post links on a Comment ?

                  • akkamaan
                    akkamaan commented
                    Editing a comment
                    Another issue is that when using quotation marks, they show up like "this"

                  • mgannon
                    mgannon commented
                    Editing a comment
                    Working on it. The xxxxwebsite link is a spam blocking tool. We need to get the workaround in. Thanks for the heads-up on this!

                • #12
                  Whelp... looks like a hyperactive default spam management system. Should be fixed now.

                  Find design engineering news and engineering videos on Design World. We provide engineers and other industry professionals key design engineering resources.

                  Comment


                  • akkamaan
                    akkamaan commented
                    Editing a comment
                    That's what I assumed it was in one of my comments above, an anti-spam feature...
                    Thanks to you and Mary for responding so quick!

                • #13
                  Search the world's information, including webpages, images, videos and more. Google has many special features to help you find exactly what you're looking for.

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