Rc4wd excavator valve question

[rccrazy523]

I am currently in the process of rebuilding my excavator and I am thinking about removing the fourth valve and using a PRv valve to regulate the pressure. What do you guys think about that? Would that be a good or bad thing to do? Would that help or hurt the Performance
thank you for all your help in advance

[chris deacon]

When you say a PVR valve i presume you mean a Pressure reducing valve? You will need a way to control this valve. Why do you want to get rid of the 4th valve may i ask?
Im not sure if you know how the 4th valve works on the 4200xl?
It opens when none of the hydraulics are being used to allow the oil thats not being used to go back to the tank. Then every time you use a hydraulic the 4th valve will close so all the oil can be used to move the rams. This 4th valve allows the pump and motor to last a lot longer. I might be telling you how to suck eggs here but i just thought i better make sure you understand what it is doing?

[rccrazy523]

Chris, thank you for your help.
The reason I was going to remove the 4th. valve is, I was thinking about mixing the channels to operate the pump only when needed.
Is this a better setup? Or, do you think I should leave the 4th. valve?
I see a lot of excavators running this setup with no 4th. valve.
THANK YOU AGAIN FOR YOUR HELP

[chris deacon]

Well the way i see thing is stopping and starting a motor will only make the motor wear out quicker? Also you have to think about how long it takes for the motor to spool up every time you operate a ram. Personally i think that a 4th valve is a brilliant idea and i dont see why other companies have not employed the same method?

[Cooper]

4 valve is a 4th potential problem,,, the valve itself, servo controlling it, and programming to operate it.

Prv, pressur relief valve, is the same thing that the 4th valve is doing, just without all that extra stuff, a simple spring and bb (so to speak)

For what I have been able to conclude about others using a valve to alter flow is for a possibility of non labor on the pump itself. With the servo controlled valve the oil is under no restraint (pressur) when no other valves are in use,(no stick com,and) thus releasing the flow unrestricted to circulate through the system. And not causing the motor to labor anymore to build pressure. Sounds good but just more things to go bad in my opinion. And for the Jung style pumps and planetary reduction on pump gear shaft it's just not really gaining much. Run time? Well if I can run for over an hour it may get me to add a couple min more in reality. So not much advantage. Now on the gear mesh pump the 4200 has, reliving pressur may help but again any real significance? Probably not. Prv, set it and forget it!! But one thing is to tie in an actual dial gauge to see what pressur you are actually running. It can be removed after set up or just stay if space provided.

As far as motor on /off. The motor isn't too bad as far as heat from constant start stop but the esc will not like that. Fact of our type of speed controllers is that are coolest at full throttle or at max signal input. By stopping/starting running half speed that is what esc's don't like and generate more heat when used that way. Now for efficiency, motors suck down electricity during initial start up. So if you wanted to stop /start pump with stick input , the best bet would to keep the pump running at say 30% then ramp up to your max rpm for stick input. A lot of programming but easily doable. Originally I had that with my ex but changing radios I just said ?!$$& it, and put the pump on a dial pot with switch to turn it off on. That way if I'm in sand, not much pump speed needed, harder soil I can turn it up. (Longer run time, but not really a pressur gain as I have the prv set) I think I have the converted 4200 running around 350-375 psi, that a bit higher than normal but I made it heavier than normal too.

And some way to achieve the realism of hydraulic movements it to use your end point travel on your servos settings. That will allow the actual valve to only open so far thus restricting the flow of oil resulting in slower ram extension/retraction. But still allow whatever pressure you have set.

And a bonus is you can have an extra valve for say a thumb if you eliminate that way of controlling flow.

[Supermario]

I'm a firm believer in the saying " if it ain't broke don't **** with it " .......but, I also believe in the saying " there's more than one way to skin a cat " !

that being said, you can definitely eliminate the 4th valve and run the system as you say. It's like changing a system from load sensing to pressure compensated in a matter of speaking.
Problem is like Coop said. The brushless motor and esc in a 4200 won't like a lot of start stop. And as he said keeping a slow speed and then ramp up when running a function would fix that but then you still need a prv to dump the oil off back to tank when no function is used other wise you'll have a heat issue.

I think the best thing you could do is replace the motor and esc. Install something that is capable and set up to handle a start stop type system. I think of RCP57 Volvo excavator he built. Pump only runs according to stick movement and that thing runs great!

Personally I don't mind the 4th valve set up and have no servo problems.....yet, now that I've said it.

[schmoking]

original motor and esc is not gonna work for that kind of setup, it could be a fire hazard on that esc i think

mine has a robbe 5055/45 motor and a robbe 50a esc. i think its intended for large scale ships.
with this motor it still got plenty of power but the speed is abit slower than original.. but i like it. with an inch cut of the bottom
of the driver cab it makes it all more to scale.
at startup it stutters abit until i open one of the valves... but i got the old one with 3 valves.
i have the 4 valve block just missing some connections..
i expect that to be much better on startup, stil not sure it would be good enough to use as start stop setup tho...

i have a pressure gauge in rear cab window so i can keep an eye on it.
motorstart i use a dial to control... i run the motor at low rpm, usually around 15 to 20 bar pressure against 3 closed valves.
i setup the dial so i get max 25 bar, i dont wanna blow it up lol.
then use the mixes to up the rpm when i open a valve... and even more when i open 2 or 3.
this makes it much more precise and it doesnt loose a lot of speed when i use all functions at once.
im really happy with this setup. not really expensive upgrade either... no more heat issue

i would maybe look into what motors those high end german machines are using, that are running this start-stop setup..

[stevec]

could you put a link up for the robbe 5055/45 motor and a robbe 50a esc on youtube you say that the runing time is a lot longer which lipo is that by the way thankyou for posting this

[schmoking]

well i bought the excavator just under a year ago and i havent made any videos, but i found an old video from a previous owner.
the way its set up in the video is without any channel mixing. the way i got it now id say its a little bit faster and it will speed up when i use more than one channel.

in the video description he says he gets 3-4 hours of runtime, i never timed it but i probly get about 2 hours on it now... but the batteries came with the excavator when it was new.
so i guess a new battery would help.

https://www.youtube.com/watch?v=MZlacv4pztY

[fhhhstix]

The pump motor is just to fast on 12V so I run mine on 7.2V and as I have showed Izzy and a few others it digs just as well on 7.2V I do give up power to the tracks at the moment but I have a 4:1 gear reducted motor to put in it then I will go back up to 12V. The forth valve is a dump valve not PRV and since when it is open ther is no real load on the pump or motor. I have my pump set up on a 3 pos switch 0,50,100% it is mixed so you can run it from a dead stop but i usaly run the pump at 50% for no demand and upon demand it goes to 100%. As soon as you move any function the pump kicks up and the froth valve closes.

This is just how I have mine set up and it works good for me and I am happy with it. I think I will be even happier when I get the new pump motor installed.

[Lil Giants]

Originally Posted by chris deacon

Well the way i see thing is stopping and starting a motor will only make the motor wear out quicker?

It's not the motor, it's the esc that will fail. And being Chinese electronics, there's no thermal protection built into the esc, so when the esc overheats to it's melting point there will either be just a puff of smoke when the esc burns out or it will catch fire... no shyt! I've heard it happened to several guys with the Chinese dump trks. that hyd pump motor runs from a dead stop.

Personally i think that a 4th valve is a brilliant idea and i dont see why other companies have not employed the same method?

It's b/c Eagle Machinery company is retarded, they're using a motor that's much too large for it's application... their solution is to dial back EPA to 19% instead building or buying out of country a properly spec'd motor.

Something else, the PRV that's in these Chinese models, the coiled spring is much too stiff & with the barrel so short - not a lot room in the 1st place for a proper length coil to allow the BB to move to relieve pressure & allow flow. Throw that piece of crap away & make your own with a longer barrel for a lighter spring so you can get a much finer tuned pressure setting & that 4th valve wouldn't be needed.

[Lil Giants]

Originally Posted by stevec

could you put a link up for the robbe 5055/45 motor and a robbe 50a esc on youtube you say that the runing time is a lot longer which lipo is that by the way thankyou for posting this

Robbe went tits up this summer. But I've heard that Multiplex has taken over quite a bit of their production line up... the Robbe Roxxy esc's I use in my Fumotec models, eta mid to late September.

[fhhhstix]

Originally Posted by Lil Giants

Something else, the PRV that's in these Chinese models, the coiled spring is much too stiff & with the barrel so short - not a lot room in the 1st place for a proper length coil to allow the BB to move to relieve pressure & allow flow. Throw that piece of crap away & make your own with a longer barrel for a lighter spring so you can get a much finer tuned pressure setting & that 4th valve wouldn't be needed.

That is a fact and mine came with a plunger inside the barrel and the finish was horrid so I tuned them both up with some polishing so the oring on the plunger would allow it to move easier. I also adjusted the spring. I found out quickly something was wrong when I could not maintain a steady psi each time I demanded psi.


The forth valve is similar in function to a CAT hyd system. Don’t change the speed of the motor or pump but adjust the flow going to the valves. Where it differs is the real machines do this with dual variable pumps and the model does it with a dump valve not exactly the same thing but still the same result.

Replacing the junk motor would help a bunch I have found that it will lock up due to its poor tolerances and that alone makes it hard to start without a load. A gear reducted motor would be a big improvement the motor spins way faster than the pump can use so slow and more starting power would be a help. The vario uses a belt drive with a smaller cog on the motor and a bigger cog on the pump hence the gear reduction slow it down and utilize the power spent to operate the pump

[elvis65]

a little racist I think.

[bigford]

well my KAT dont have the dreaded 4th. ch but we all saw the video at cabin fever!!! she looks real pretty on the lowboy

[Cooper]

Originally Posted by elvis65

a little racist I think.

Let's not be hyper critical and bring all the b.s. Politically correctness into this hobby, it is simply a reference to the whole world business machine, don't read a book about it, buy a cheep machine and also buy a high quality machine and educate yourself. There is a difference between cheep, inexpensive, low quality, high quality, and expensive. Economics 101- no such thing as a free lunch!!

Please delete if offensive, I just don't want to be politically correct and worry about hurting someone's feelings, that is too much like work and this hobby is as far away from that as I can get

[elvis65]

ok

[Lil Giants]

Originally Posted by elvis65

a little racist I think.

I changed it... better? I have no personal resentment to the Chinese ppl or any other ethnicity on this planet.

China mentally in manufacturing on the other hand from my viewpoint, they're all about production & couldn't care less about quality, just get it out the door, sell it cheaper than anyone else can & sell lots!

[elvis65]

Hi
I totally agree, for a couple of dollars more in the production costs and a little more time they could produce some hi quality stuff.
but it's just that will do mentality and sod the quality that will always let things down.
dave

[uktwin]

Originally Posted by Cooper

Let's not be hyper critical and bring all the b.s. Politically correctness into this hobby, it is simply a reference to the whole world business machine, don't read a book about it, buy a cheep machine and also buy a high quality machine and educate yourself. There is a difference between cheep, inexpensive, low quality, high quality, and expensive. Economics 101- no such thing as a free lunch!!

Please delete if offensive, I just don't want to be politically correct and worry about hurting someone's feelings, that is too much like work and this hobby is as far away from that as I can get

Its not racist at all,, its a fact, 40 years ago Japanese motor bikes were the same, made out of monkey metal, put a spanner to it and it crumbled, still good enough to see off our(British) motor cycle industry but then they thought having a vertically spilt crankcase was a good idea to keep oil in., you get what you pay for in any engineering and the longer you do it the more you realise that, this why its so hard to get any plans of machines as OEM's are afraid cheap Chinese parts are put into their machines, damaging their reputation, Aviation and F1 are paranoid about it.

regards
Kevin.