needle tank vent, open or closed during operation?
 

Ok, hope I don't get flamed out of this forum for this one. The 4200xl comes with a needle type vent for the hydro tank. Most of you have probably seen it. The question is should the vent be open or closed during operation? Is this a one way needle valve for pressure to escape if need be? I know you can add oil through the pressure fitting(blue.) I've been running mine pretty open as that's how it came. I've been coming across vids and threads of people closing it during operation and just opening it when adding oil. Any thoughts? Here's the vent valve. For the most part just wondering if I'm missing some performance with it open during operation.

http://store.rc4wd.com/Ventilation-S...nk_p_1823.html

Re: needle tank vent, open or closed during operation?
 

What I do with mine is after changing oil or it sitting awhile I open it work the booms by hand to get the air out once air is out of the system I shut it. Not sure if that's right or not but seems to work. Found video at 16:00 mins he explains it
https://www.youtube.com/shared?ci=3i1e5HE3od8

Re: needle tank vent, open or closed during operation?
 

Funny you should mention Medic's vid. Thats one that got me thinking about it.
I've never had my cylinders with that much air in them that they wouldn't work at the get go.

Re: needle tank vent, open or closed during operation?
 

Ya I have had that my main rams of rings were shot from new and leaked alot of air into it so would have to bleed them before every use. What a pain that was.

Re: needle tank vent, open or closed during operation?
 

The vent should always be open.

Medic filled his reservoir way too full, no allowance for heat expansion.

NEVER in my life have I ever had to manually bleed a double acting cylinder, not even 1st initial start up of a new never ran before model. There's something mechanical wrong with that model! Near the beginning of the vid when he flipped the wrong switch for the pump, did he turned off the mix so the 4th valve didn't function correctly? Quite likely the "air lock" he has from sitting a long time is b/c his tank is too full & the vent is closed, the pump has lost it's prime & the oil won't gravity feed from the tank.

The only time I ever manually open/close cyls is for an oil change to push 99% of the dirty oil out, Pump off & open each valve both ways. Put in fresh oil, turn on pump, cycle each cylinder a couple times from the radio operation, check/add oil level, then do the next valve/cyl(s). The pump will push the air out of the system itself.

Re: needle tank vent, open or closed during operation?
 

Huh I did not know that but after I read that it makes perfect sense. Once I get it back from my LHS I'll have to crack it open or alot open?
Thanks,
Joe

Re: needle tank vent, open or closed during operation?
 

A couple turns, doesn't have to be a lot, but it does need to vent.

My Fumotec models use a Jung pump with a remotely located reservoir, the supply line to the pump is 6 or 8mm, the pressure line from pump to valve is 4mm. I can't recall, but I think the supply line from the Eagle model is the same 4mm as the pressure line, and they're using an oil reservoir that is much too small for the volume that their pump draws. Even in life sized equipment, the supply line ID is always much bigger than the pressure line, as the pump relies on gravity fed oil supply.

Re: needle tank vent, open or closed during operation?
 

Right on Giants, thx for the heads up. So is it a one way needle valve unless you use the press in ficture if wanted? To me if you have a 1//2 full tank you wouldn't want more air allowed into the tank and possibly cause bubbles or foam in your lines so you'd want it closed? Or does the rising and lowering (expansion/fluid in and out) of that 1/2 tank essentially keep it air tight? I've tried to read up on r/c hydro but the subtleties I'm still working on.

Re: needle tank vent, open or closed during operation?
 

The tank on that model is much too small. You should upgrade to a plastic fuel cell for an airplane or heli. Much easier to see the oil level & a higher oil volume will reduce foaming & the chance of the supply line sucking air b/c your model is at an awkward angle. And if you go with a new tank, increase the supply line & fittings to atleast 6mm so the oil will flow more freely to the pump.

Re: needle tank vent, open or closed during operation?
 

So today I watch the whole RC Sparks video noticed on his model that the supply line to pump draws from the top of tank... that's dumb! I can't recall clearly, but I thought mine drew from bottom side of tank. You guys with your newer models have sump line atop tank?

Re: needle tank vent, open or closed during operation?
 

I'm up at work now so I can't check mine but I found a picture on rc4wd website looks like the suction to the pump is from the top.
http://i65.photobucket.com/albums/h2...psrialfc1n.png

Re: needle tank vent, open or closed during operation?
 

Yes it is from the top. I've been looking around to find a nitro fuel cell to replace the stock tank, main question is how do you have enough wall thickness for your fittings on the plastic fuel cell? Do you need to create some bosses for the fittings to be secure?

Re: needle tank vent, open or closed during operation?
 

That's what the problem is, you get an air bubble in the sump line & that gear pump isn't self priming. Maybe closing the vent when not in use will prevent that, but it should be open when it's operating.

Threading a fitting into a plastic fuel tank, carefully drill the correct under sized hole, manually thread fitting into tank, unthread it, then add sealant to fitting threads & screw it back, not over tightening fitting pulling out threads. Let it dry 24hr. I've done a half dozen this way & have never had one leak.

Re: needle tank vent, open or closed during operation?
 

Right on. Do you have any recommendations on sealant? Thanks for the info.

Re: needle tank vent, open or closed during operation?
 

Just curious - when the suction fitting is at the top of the tank, is there a stand tube from the fitting down to the bottom of the tank?

Ken

Re: needle tank vent, open or closed during operation?
 

Nope.

Re: needle tank vent, open or closed during operation?
 

There must be a suction tube the fitting screws into or it wouldn't work at all without the tank being right full. :thinking:

Given how horrible this model company's machining tolerances are with cyls & valves leaking from new, chances are the tolerances in the pump aren't perfect either, and that's why it won't prime on its own & won't hold prime during periods not in use.

For sealant, I've been using the same liquid putty sealant that I use with plastic water fittings. I'm sure a blue or red locktite would suffice too.