ASV RC100 Relief Valve not working correctly?

[tuckinlugz]

Hello. I really need some help with this. I bought the machine about 2 years ago. A 2006 model RC100. It came with a loftness G1 carbide cutter that I was told needed new teeth.

Before buying th machine I had talked to a service tech at my local dealer and he told me if I bought one (rc100) that I should come in and get a valve installed that would bypass something so that when I stalled the cutter head it would allow me to still be able to control the loader arms. He said that if I did not have this valve I would have to turn off the machine and turn it back on in order to start working again. I never checked to see if this was true, I just took it right over there and had it put on.

I also had them check the pressures for everything and and make sure it was good. THey said it was all ok.

I tried out the cutter, it seemed to not work very well, so instead of buying the new carbide tools, I decided to do the Loftness kwik axe conversion that I had read about on here.

I got it up and running, and I thought it was ok but I still wasn't impredded too much, but I was new to mulching and I thought maybe I was just expecting too much.

It just seemed to bog down to easily, even in small brush. So I took it to another hydraulic shop to see if they could test the pump. They stuck something in the cutter to stall it out and see if any fluid passed through the motor and it did not so they advised the motor was good and they also checked the flow and it was right at factory specs.

I demoed a gyro trac 500hf head and it cut like a scalded dog, blasted right thru everything, it was even throwing sparks from the dirt that was in the material.

I knew the 500HF head was better than mine, but it was like 4 times better/faster, easy. Never stalled on the brush.

So I was still confused on whether it was that much better, or if I have another issue.

I did some research and found that the gyro head has a 2 speed hydraulic motor, and mine was one speed.

I also had factory pressure relief valves on the loftnedd cutter that I tried to adjust to see if anything changed. It never did, and I ended up taking the whole refief valve setup off the cutter head. I was told my machine had one built in so this would be ok. It ran the same after and I have done a lot of work with it since then.

I have never been able to cut more than a half acre in one day, and I have read that people running carbides can easlily do an acre a day (unless it's like all 6" oak tress etc.)

So I just have to go slow and it cuts fine, but I just think there has to be something else wrong. The only thing that I can think of is that maybe the pressure relief valve on the machine may be cutting in too early? Causing the cutter to slow down instead of kicking thru the needed torque.

I have the quick disconnects still in place, they aren't leaking or anything, but I have heard that they can slow it down, but the dealer says they are rated for 70 gal a minute so it wouldn't matter.

I bought a brand new brush monster 6' high flow model and it doesn't seem as good as it should be either, so I was thinking maybe the same problem.

The only other thing I can think of is to rent another machine or cutter or both and compare them, to try to eliminate something.

Sorry about the lengthy post, but I figure I need to include as much info as I can to see if anyone can give some advice. Thanks!

 

[tuckinlugz]

And exactly how does the pressure valve work? What pressure should it kick in at? And can it be adjusted?

 

[McCaskey]

My Carbide Cutter has a white number "8" painted on the motor, visible from a hole on the front cover. That's the size for RC100 flow & pressure rates. Maybe you got the wrong motor? Originally I had a "6" motor which would barely mow grass without stalling.

The CC G1 has an internal relief valve, factory installed.

RC100 does not have a tachometer so it's hard to tell if the throttle is really wide open. The throttle pedal can bottom out on the cab floor when the cable becomes stretched, engine won't be at max RPM's.

 

[tuckinlugz]

Yes I have a #8 motor, visible from the side. When I bought the head I called Loftness and they said mine was setup for an RC100. I told them I did the conversion and they said I could go with a #7 motor if I wanted, but I decided to kep the #8 and get some different pulleys to make it a little faster. By internal relief from the factory I am assuming you mean under the cover for the motor, this is the stuff I took off. All that is left is the hoses going straight into the motor.

I am not 100% sure if the machine is running at full throttle. The pedal does hit the floor, but it looks like spring is bottomed out that goes thru the cab near the inside a/c return air filter. What rpm is full throttle supposed to be? Maybe I can check that.

 

[J_J]

Full throttle through a hyd motor is based on the flow in GPM's that you provide, and it is the resistance of the hyd motor during work is what develops the pressure. A relief should be in the circuit to protect the motor, as it will blow the seals or whatever.

Do you know the GPM rating and pressure of the hyd motor? Do you know the pressure of your pump and the GPM.

Here is a for instance, If your hyd motor has a displacement of 22 cu in, and your pump can produce about 3000 psi, at 20 GPM's, you could expect the hyd motor to develop about 34.85 HP

Cutting head velocity will be based on the diameter of the drum and the cutting teeth.

motor rpm = 210
torque = 10,510in lbs or 875 ft lbs

If two different machines have the same flow and pressure, then they both should run the cutter head the same, with equal expectations.

Have you checked your relief settings, and have you did a flow test to see if the pump is producing the rated flow?

If your system stalls out, that means that the motor can not overcome the resistance to cutting, due to displacement, pressure, and flow volume.

If you lose 1000 psi somewhere, your motor is now down to 22.95 HP.

 

[Robbie Hegwood]

First things first. Take your machine to a shop that can flow test it. This will settle everything. It will tell you flow verses psi and it will be going thru the relief valves so if there not working it will be discovered.

Max flow should be 37-38 gpm. Now remember you will never actually see 37 gpm. That is at a very low psi. the flow meter's start loading @ 500psi so we might see 28-30 but this is okay, a bit of a misunderstanding in the hydraulic world. Flow will decrease as psi increases. @ 0 gpm you should have 3650 psi. 3400 older machine's. If your shop can, and your machine is set @ 3400 have them turn it up to 3650.

Now if your machine passes this test then there is indeed a problem with your cutter. Yes I would remove the quick couples. They rob 200-250 max psi and create heat.

Now if it checks out you are comparing a Honda to a Hemi.

Loftness motor, fixed displacement probably piston small CC.

Gyrtotrac motor, Variable speed, variable displacement, bent axis motor.

 

[tonyoz]

If it is running one head better than the other then the problem is most likely in the hyd motor on the poor performing head. The hyd motor should have a relief valve fitted which should be set at lest 10% higher than the pressure of the carrier. With a flow and pressue it is not hard to test. If the rc100 is delivering the correct flow the throtle cable may be OK.

 

[tuckinlugz]

I had the flow tested which showed the flow was between 38-40. I did not know when the flow decreased the psi increased.

I will try deleting the quick disconnects but it'll take some time to figure out the fittings I need to buy. Should I just buy some caps to put on the ends if I take them off?

 

[Robbie Hegwood]

Let me be clear, I like Loftness equipment, the unit I had served me well. BUT... a side by side comparison shows the real difference. I was blown away when I was actually able to run a planier head. You have pitted the "worst cut" against the best. For production it's hard to beat a planier.

 

[J_J]

I think what tonyoz is talking about is removing the QD and connecting nipples between the two hoses, but that kills the Quick Disconnect thingy.

You could instead go to the next size up QD for less flow restriction.

I am not sure what tonyoz means about the psi decreasing when the GPM increases. There will be a slight pressure loss due to the length and size of the hose, but not a big thing.

If you put a pressure gage just off the pump, you should see the pressure remain almost steady if the same resistance is used. If you are checking the relief pressure, you add resistance until the fluid builds up to the relief pressure. Perhaps tonyoz can explain the ratio of pressure to GPM's thing.

The thing that is going to change pressure the most is the motor, or cyl, or whatever is causing the resistance to the hyd flow. Heat and length and size has some effect.

tonyoz quoted 38 GPM for low pressure, but the specs for the motor or pump gives the specs as max GPM, and max pressure. I believe if the manufacturers wanted us to know the pressure rating for each GPM, they would have provided a chart.

And what is the 10% psi setting above the carrier. Are you talking about pump max psi, or hyd motor?

If you had a pressure gage installed at your station to monitor the aux pump pressure, you will see the idle pressure of the motor, and any pressure up to stall pressure when you are using the mulcher. The pressure will vary as you work the machine.