Hydraulic Circuit Help Needed

I am pretty well versed with manual machining and TIG welding, but hydraulics are foreign to me. I have tried my best to internet-educate myself on the topic of fluid mechanics, but I am desperate for the advice of folks that know better than myself. I am in the planning process of building a volumetric mixer for fine aggregates (a small trailerable unit). Essentially, I will have 2 bins of separate material that need mixed at a 4:1 ratio. I figured on screw conveyor-feeding the two bins over a larger inclined conveyer screw system to mix and discharge the material. Preliminarily, the two material bins will be discharged with 6" diameter screws, and will be geared to discharge at 4:1 over the 12", 10' long mixing conveyor, which will be set on about a 40 degree angle. The bins will hold about 5 and 20 cu. ft. respectively, with an exposed screw lenth at the bottom of the bins of about 3'. The weight of the material will be about 60 lbs per cu. ft. Ultimately, I would like my mixed material to come off the the final mixing conveyor at about 5 cu. ft./minute, give or take. So, I will work on attaching the hydraulic circuit that I have created for the power transmission when I have it figured out how to attach it. For now, I think I will need to power the unit with a 20-30 HP gas or diesel engine (since it will be a mobile mixing unit). I am trying to err on the heavy side just in case. The attached diagram should be pretty explanatory of my plan (if I figure out how to attach it), but I am lost when it comes to line size, and gpm and psi of the sytem. Not to mention, there are so many outputs of motors, that I am sinking deeper and deeper trying to figure this out. I just had a baby, so enrolling in a fluid mechanics school is out . Any and all suggestions and criticism to help me fill in the blanks would be appreciated. Thanks in advance.

Benny

Cannot seem to get my diagram to attach. I made it in Word - it is about 33 kb. I tried saving it as a web file - shrinked it to 796 bytes ... rejected. Any suggestions on how to get this to attach. Thanks.

Benny,
If you design the circuit you can troubleshoot it. I highly recommend the following books, they have been invaluable to me.
-dale

Industrial Fluid Power - Volumes 1-3
Fluid Power Data Book

Womack Machine Supply - Textbooks

Couldn't it be as simple as equal PSI/volume available to each hydraulic motor with GPM difference in the motors creating the 4:1 ratio and fine tuned with adjustable flow reducers and sprockets/chain to the screws? Most hydraulic motors in good condition, can be counted on to pretty accurately convert volume into specific rotational output, though dissimilar loading can/will result in differential action between two hydraulic motors fed from the same source of pressurized fluid, overcome with dual chamber pumps or two pumps driven by the same source, providing yet another tuning point.

I'd lean toward a single "motor", (maybe even straight off the engine, eliminating the hydraulic motors) and good 'ol mechanical spliting of 4:1 but there are variations in flow rate of different materials too. I got involved with that in the 50's with attempts at modifying a concrete block plant toward simplistic automation but the dang aggregate quarry kept changing the water content in the sand and gravel they delivered. Mechanical ratios were easy but even with pnuematic vibrators bolted to the bins, flow would hang up and without modern moisture sensors, the final water content couldn't be automated....... reaching an "agreement" with a competing quarry on water, helped a lot.

Ratio by gearmotors and a generator might simplify the mechanics, all three components, (motors and generator) easily replaced, wiring much easier to run than twice-as-long hydraulic circuits, (gotta' get the oil back) and don't leak oil. Provides an option, generator(s) in truck, extention cord, less crowding on trailer.

I'd think that tuning of the flows to two different "graduated", (like a measuring cup) containers, or placing each on a scale, could lend it'self to fine tuning without making bad ratio mixes, before introducing the material-combining conveyor belt as a finishing touch. Just dump the buckets back in the bins, tweak and try again.....

Benny, if variations in material "viscosity" are not a factor, you're half way home, good luck and other folks will have good ideas when you get the promised diagram attached.


Bob

Benny,

Here are some unprofessional thoughts. I have built several hydraulic machines and they have worked well. If you design your machine from the motor backwards to the pump, it sometimes becomes 'self designed' as the components come from the factory with HP/GPM values and piping sizes already in place.

The screws will call out required HP for different speeds and materials so a hydraulic motor can be spec'd for each of them.

The total GPM for all the motors will allow you to spec a pump which will in turn call out how large a electric motor or internal combustion engine is needed to run it.

All the components will have pipe sizes that allow for the designed GPM of that component so you don't need to guess. This may sound like a simplistic approach but it will get you started.

Stuart

atomarc said:

Benny,

Here are some unprofessional thoughts. I have built several hydraulic machines and they have worked well. If you design your machine from the motor backwards to the pump, it sometimes becomes 'self designed' as the components come from the factory with HP/GPM values and piping sizes already in place.

The screws will call out required HP for different speeds and materials so a hydraulic motor can be spec'd for each of them.

The total GPM for all the motors will allow you to spec a pump which will in turn call out how large a electric motor or internal combustion engine is needed to run it.

All the components will have pipe sizes that allow for the designed GPM of that component so you don't need to guess. This may sound like a simplistic approach but it will get you started.

Stuart

Click to expand...

Good stuff Stuart......

Bob

I can alway count on PM for good sources of help. Thanks so far for the good advice. I will look into the books pronto. Robert - thanks for the insight. I thought about 240v power at first, but I balked at having to work around a generator ... I won't rule the idea out just yet. For the last suggestion - I will see if it makes sense to work backward. Still working on the diagram upload.

Benny said:

I thought about 240v power at first, but I balked at having to work around a generator ... I won't rule the idea out just yet.

Click to expand...

I know exactly how you feel about that Benny. I used to have a 240V "wall saw", cut's concrete walls, with water cooled diamond blade, water spraying everywhere, river underfoot! It made me very nervous.

....but just sayin', generator in truck, TEFC motors, "liquid tight" flexible conduit and NEMA 3, (outdoor rated) box with waterproof connection of extention cord and plug at generator only.....

....kidding, not making a pitch, I got rid of that saw, couldn't afford the underwear bill..... but your operation may not be nearly as dangerous.

Bob

What part of Ohio are you located in? Ohio is loaded with A-1 Concrete Leveling franchises that use a truck mounted hydraulic driven 6” mixer with related hydraulic drives and controls to feed it. Talking with one of those folks /looking at the set up may answer a lot of your questions.

IMHO hydraulic is the only way to go for this application ....

Joe

I have just a little experience with this, but will add, a number of years ago, a customer built their own recylcling line for cardboard and had a bunch of gear head motors running the conveyors and they were constantly wrecking them. I suggested going to direct hyd motors and they never had annother problem, and they were rough on stuff! dumping a couple of tons of wet corrugated in at a time, etc. you can also easily have a overload protection with a dump valve,

The file size is only 33kb for my hydraulic diagram, but it will not take. A picture is worth 1,000 words, but maybe I can describe it in less. At any rate, starting at the top, I have a vented hydraulic fluid tank with a suction line down to the pump (which will be gas or diesel driven - more than likely). Off of the pump, the high pressure hydraulic line passes through a pressure gauge and relief valve, then into an adjustable flow valve with a pressure gauge in front of it (this could be my first problem area, but I will keep going). Out of the flow valve, the pressure line connects to the motor, then from the motor back into the valve. Then, I have a line going out of the valve into the next gauged flow valve. The same scenario is replicated into the second motor and the third, final motor. From the last flow valve, I have a return line going through a filter, then into the tank. That is what I have drawn up. Is it proper practice to connect multiple flow valves this way, or should I route the output from each motor directly back to the tank, which would require some sort of 3-way manifold for the input for each valve? Ok, thanks again to all of you so far. I look forward to more advice now that I have a little more info on the table. Building backward makes sense, but I just want to make sure that I am not trying to drive a nail with a screwdriver with my routing, if I have problems with the basic fundamentals of my circuit.

keep it simple.
I would have same sized motors and run them in series one behind the other as it refers to the fluid. i would achieve the speed differential with gear boxes or sprocket and chain. this would give the simplest hyd. circuit and the most economical. you need 1 valve-1flow control-2 motors-1 pump-and hose. what you don't need is 1 valve-1 flow control- flow manifold that's a biggie for cost.