PC1800 Front Shovel (1/12)

[Lil Giants]

Originally Posted by steamer

What a beautiful setup for a slip ring. Just put a generous coating of dielectric grease on the copper rings to stop pitting and it will last forever!! And it looks to me like that Alberta loonie is shrinking smaller with every picture, go Justin!!!!!
Rob

I was going to suggest the same thing as Rob... the slip ring in my JD850 is somewhat similar to yours Kornel with brass contacts, before adding the dielectric grease the friction created a black soot on the contacts creating a loss of electric connection... not a moments trouble since 4yrs ago.

[DADSGARAGE]

That is a very helpful suggestion guys!! Thanks!!! Difinetly going to do that when I get it wired up for the first test, still need to order the gear/box motors and finish a number of things yet before it's ready for a test run....Thanks again!!
KP

[kerst]

Nice slipring!

[tracksntreadslou]

Every time i come on here i learn something ...Break out the popcorn ..think this tread deserves that ...I dont see anything wrong with that slip ring ..thanks for sharing ...good to see you you back on this build

[DADSGARAGE]

Originally Posted by tracksntreadslou

Every time i come on here i learn something ...Break out the popcorn ..think this tread deserves that ...I dont see anything wrong with that slip ring ..thanks for sharing ...good to see you you back on this build

Thanks!!! I think we all learn from each other on here, everyone has new ideas and designs and it is always interesting to see what other have built and how....

KP

[DADSGARAGE]

Finished working on the hydraulic fitting....took longer than I thought...lol

Next will be another test run with 4 cylinders using a new motor and belt drive, need to find out if there is enough volume when running the pump at 1200 RPM

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[DADSGARAGE]

Did some more "high tech" testing of the hydraulics....turns out it does work but not as planned...lol...the open center valve is not the best for running more than one function at a time, live and learn, need to convert it to a closed center which will mean the PRV will be bypassing all the time when the controls are in neutral instead of free flow back to tank when using an open center valve.

Started testing with 20 lbs and then added another 20lbs to see what it would do with the 40 lbs....the extra weight made little to no change in cycle times or pressure

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After running it with the 40lbs I noticed the 1/4" threaded rod was bending under the load, so went back to using only 20lbs for the "wire and wood" testing...lol

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The motor and belt drive seems to work well, using a small adjustable pulley on the pump so the RPM of the pump can be changed a bit while using the same input RPM of the motor

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[RCP57]

That's a shame about the valve bank but I'm sure you will get it sorted out. Looks like a good simple setup. I say just paint the plywood and get digging.lol

[Lil Giants]

So what pressure are you currently running at?

So you can't feather two valves together at all for simultaneous movement?

I don't fully understand the open/closed concept, but I'm pretty sure these german made rotary valves are open center, as there is two return lines off one side of the valve; one goes through prv & the other direct to tank. Precise movement of the tx & I can get all 3 valves to work together.

[DADSGARAGE]

Originally Posted by Lil Giants

So what pressure are you currently running at?

So you can't feather two valves together at all for simultaneous movement?

I don't fully understand the open/closed concept, but I'm pretty sure these german made rotary valves are open center, as there is two return lines off one side of the valve; one goes through prv & the other direct to tank. Precise movement of the tx & I can get all 3 valves to work together.

The PRV is set at about 275psi, the operating pressure was about 210 PSI

Yes two valves can be used together but the speed of both functions changes as well as the pressure, I can understand the pressure change but flow should remain constant no matter what the pressure is.....a positive displacement pump (gear pump) that delivers say 2cc per revolution should always deliver that amount of oil no matter what load is on the system,what will change is the pressure and the speed the oil needs to travel through the system....

In an open center valve all the flow from the pump is allowed to flow "freely" back to the tank when the spool valves are in the neutral or center position...so my thinking was that it would be a good way of eliminating the use of an ESC on the pump to gain some battery run time, the pump would always be running at a constant RPM and would take less power to just keep moving the oil in the system unrestricted when no function is being used, instead of always having a load on the pump and motor when using a closed center valve that needs a way of allowing the flow to get back to the tank using some type of unloading valve....but a closed center valve system always maintains a constant pressure in the system which is set buy the unloader valve or PRV, the open center has almost zero pressure in the neutral position because there simply is no load or restrictions in the system which is good in one way and bad in other ways.....

[sparkycuda]

The hydraulic stuff can get confusing very quickly. Yes, a fixed displacement pump will deliver same volume for same pump speed, but if divided between circuits, each circuit gets only a part of that volume, so each function will be slower than each individually. Also, for a given valve opening, oil volume is directly related to pressure on that circuit. If using two circuits at once and both valves are opened the same amount, the circuit with the least resistance (and lower required pressure to move it) will move first. Only when that circuit bottoms out or it's valve is closed, will the other (higher required pressure) function move. Throttling or feathering the two valves during operation is the only way to compensate so both functions can move simultaneously while operating at different circuit pressures. Pressure-compensated (and usually with variable displacement pumps) take care of this for operators, but are much more complicated systems. Yes, the open center system does reduce heat and horsepower needed when in neutral. But having some "standby" pressure, as Mario stated, does give quicker response when activating. Also, open center may allow a function to drop a bit when first pressurizing a circuit - I don't think our model circuits have load-check valves to prevent this.

Ken

[DADSGARAGE]

Originally Posted by sparkycuda

The hydraulic stuff can get confusing very quickly. Yes, a fixed displacement pump will deliver same volume for same pump speed, but if divided between circuits, each circuit gets only a part of that volume, so each function will be slower than each individually. Also, for a given valve opening, oil volume is directly related to pressure on that circuit. If using two circuits at once and both valves are opened the same amount, the circuit with the least resistance (and lower required pressure to move it) will move first. Only when that circuit bottoms out or it's valve is closed, will the other (higher required pressure) function move. Throttling or feathering the two valves during operation is the only way to compensate so both functions can move simultaneously while operating at different circuit pressures. Pressure-compensated (and usually with variable displacement pumps) take care of this for operators, but are much more complicated systems. Yes, the open center system does reduce heat and horsepower needed when in neutral. But having some "standby" pressure, as Mario stated, does give quicker response when activating. Also, open center may allow a function to drop a bit when first pressurizing a circuit - I don't think our model circuits have load-check valves to prevent this.

Ken

Yup....it does get confusing very quickly for me!!! Lol
Here is what I understand....if a pump at a given RPM moves 2 gal/min is attached to a cylinder that has a total volume of 2 gallons it should take one minute to fill the cylinder....if you have two of these 2 gallons cylinders it will take longer to fill them both, in this case twice as long. The larger the total volume of the cylinders being used the longer it takes to fill them all and the cylinder movement speed will be reduced accordingly. What I don't understands is why this isn't happening like it should....this pump supplies much more volume than what is really needed....there should be a surplus of volume left over when using multiple cylinders....but where is this surplus going??? I think that in this valve body there is always some flow allowed to bypass the spools and flow to the return port even when the spools are totally open to the cylinders!!?? One would think that all the flow would be channeled through the spools that are being used and only allowed back to the return through the return hoses on the cylinders. Yes/No ???

[sparkycuda]

Interesting?!?! Have you confirmed the volume of oil being supplied by the pump? Disconnect the return line at the tank and put a container that is calibrated or that you can measure the actual quantity easily. Depending on how large your reservoir is, run the pump without actuating any circuits and measure the amount returned. May have to run for only 15 or 30 seconds, but confirm pump delivery. What pressure is being displayed during this test? Confirm system maximum pressure will make 275 PSI. Bottom a cylinder (either direction) by fully stroking control valve and see if relief valve actually is 275 PSI. Also, at this condition, return oil volume should match max output of pump. (You may see a slight decrease if the motor reduces RPM while under relief pressure, plus no pump is 100% efficient. Most big gear pumps can be up to 98% efficient when new. I'm guessing yours should be near that.) When you saw the system operate at 210 PSI, was that while cylinders were actually moving? Should go to 275 PSI when cylinder hits end of stroke. If there is a question about individual circuit flow, disconnect a cylinder line and put it into a container for measuring. Stroke valve fully and measure volume delivered to circuit. At same time, see if any oil is being returned via the valve return to tank. Should be practically nothing. If is significant amount, the valve may have something going goofy. Also, observe system pressure at this condition.

Ken

[steamer]

Speed in hydraulic's can only be changed by two things, pump rpm and volume of oil. The pump is designed to give max cc at the max diameter hose that can be fitted to the pump output.
If you put on small hose it acts like a restriction in the circuit. Also to get max flow every hose from tank to pump to valve and back to tank has to be the same diameter or you'll have the same restriction in the circuit. If the pump is the same as what I think you have the inlet and outlet in 9/16" Dia. =1.767 sq. in. Sizing the hose down to 1/4" .785 brings you down to about 2.25 less volume than the pump can produce = slow cylinders.
I think if you up size all the primary circuit hoses to the proper diameter then you'll able to control it from there with motor rpm.
Hope this helps.
Rob

[DADSGARAGE]

Originally Posted by steamer

Speed in hydraulic's can only be changed by two things, pump rpm and volume of oil. The pump is designed to give max cc at the max diameter hose that can be fitted to the pump output.
If you put on small hose it acts like a restriction in the circuit. Also to get max flow every hose from tank to pump to valve and back to tank has to be the same diameter or you'll have the same restriction in the circuit. If the pump is the same as what I think you have the inlet and outlet in 9/16" Dia. =1.767 sq. in. Sizing the hose down to 1/4" .785 brings you down to about 2.25 less volume than the pump can produce = slow cylinders.
I think if you up size all the primary circuit hoses to the proper diameter then you'll able to control it from there with motor rpm.
Hope this helps.
Rob

Speed in hydraulics can be changed.....but the pump RPM is directly related to the output volume, so short of up sizing a pump the only way to increase volume flow is to increase the pump RPM. The pump I'm using is really much to big for what I'm using it for so I don't need the max output it can produce....you are right about creating an unnecessary restriction due to under sized hoses but the current sized plumbing is actually within the proper sizes for the flow rate, there are oil flow speed charts that can help in getting the proper combination of flow, hoses sizes and the ideal flow of oil in feet/second....suction is the slowest, pressure lines are the fastest and the return is a bit slower than the pressure lines. The ideal oil flow velocity according to the charts is....suction 2-4 ft/sec, return is 10-15 ft/sec and pressure lines are 15-25 ft/sec...this is for full size systems but I would think the same would apply to smaller scale as well. I think the problem I'm dealing with isn't the flow from the pump but more about where its disappearing to....not going to the cylinders...it's either the PRV or valve body not doing what is should .

[Lil Giants]

Pressure makes a dramatic difference in hyd speed too... looking back to pg1 I see the size cyl bores you're using are 25% bigger than my 850 hoe that has its working pressure at 475psi, but your front shovel is likely going to be 25% bigger too... try your cycle speed tests at 450psi.

[DADSGARAGE]

Originally Posted by Lil Giants

Pressure makes a dramatic difference in hyd speed too... looking back to pg1 I see the size cyl bores you're using are 25% bigger than my 850 hoe that has its working pressure at 475psi, but your front shovel is likely going to be 25% bigger too... try your cycle speed tests at 450psi.

Hey Joe.....yes pressure does have its advantages....the only way to increase pressure with what I'm working with is to increase pump RPM, if the resistance or load isn't there the system will not make more pressure. The open center valve pressure with the controls in neutral is zero...I'll bet with your system the pressure is always at operating pressure. This build might be bigger than your 850 but I'm hoping to run it on half the pressure, so I have over sizes the cylinders to somewhat compensate for running a lower operating pressure...this may end up being a bad idea....lol

[Cooper]

I may not be the best advise but I would think a tapered pin and seat would be better. Assuming you have the capabilities to hold tolerances. And I'm sure you do . I would think the hard part would be getting the right spring. I've been wanting to make one myself and have just assumed a taper would snap and flow better than a round bearing surface. ill be following how you make out so my learning curve might not end up with more parts for the recycling bin. . Appriciate you posting your progress good or bad.

[Supermario]

This goes beyond my knowledge and experience with hydraulics. I troubleshoot and fix existing systems made by people much smarter than me, never designed or thought about making a relief but based on hyd principals the ideal relief would be a needle type seat.
Just like cylinder diameter and surface area effects the amount of power generated , so does the smaller the surface area of a relief needle valve effects the strength and sensitivity of a relief and better for that cracking pressure type operation.
Like I say.... Beyond my pay grade but that's how I see it. Nice thing is you already know flow rates and the amount your dealing with and I wonder if there's a formula out there that would tell you port size and needle dimensions to get what your looking for?

Hmmmm, i might be able to get you a pilot relief valve that runs at about 350psi come to think of it! I'll let you know next week.

[tc1cat]

Tapered pin and seat sound good but would not be my choice for a PRV. I deal with tapers every day at my real job. We make our tapers down to .000015" tolerance on diameter and .000015" tolerance on taper. These tight tolerances are used for a pressure fit of the male and female tapers. The parts are not held together by any bolt or screw just the mating of the 2 tapers under any type of pressure. A PRV using a tapered pin may lock up on you if the 2 surfaces were close to a perfect match on tapers. It takes a lot of force to get 2 matching tapers apart. Some times they don't have to be that actual close to make a very secure fit. This is in the medical field for replacement hips, shoulders, and knees.

I would use a ball bearing rather than make a tapered pin.

Just my thoughts and opinion.