Hydraulic top link issues
- Thread starter Kodiak45
- Start date
- Views: 34070
We're trying to help... don't worry about it. Personally, I like needle valves since they are so adjustable from zero to 8 gpm. It's very slow to cut it off.... dial, dial, dial it down. What I like is once you find the sweet spot, you can see where that mark is so you can dial back to it.
3/8 NPT 8 GPM PRINCE WFC-6 IN-LINE FLOW CONTROL
Rich B1
Veteran Member
- Joined
- Jan 28, 2017
- Messages
- 1,122
- Location
- Stone Creek, OH
- Tractor
- NH TC21D, 3 Craftsman GT’s…..old but tough, AGT Industrial QH 12
Since gravity or working forces can act in both directions on a top link cylinder, I would do double Parker type restrictor valves. You also are dealing with rod and barrel flow differences so you can adjust flow for same speed in both directions.
If you over run a cylinder, you can introduce air from mild cavitation. That is why I prefer restricting the exhaust side. The restrictor functions as a dynamic brake in effect.
The flow rate to the cylinder won't change, but the cylinder speed can be restricted using the restrictors.
Rich B1
Veteran Member
- Joined
- Jan 28, 2017
- Messages
- 1,122
- Location
- Stone Creek, OH
- Tractor
- NH TC21D, 3 Craftsman GT’s…..old but tough, AGT Industrial QH 12
That's the ticket. Those work really well.
olPete
Gold Member
Very interesting, thanks Teg and Rich. One of my spools has a sticky flow rate adjuster so the toplink is usually plumbed into that bank.. I'm considering getting what you advised the OP for my mower, it has a single acting lift cylinder and my ears pricked up when you said it free flows one way. I don't like to adjust it too slow on the drop, as it's then too slow coming up. Sounds just like the answer to our problems.
Pete
Pete
Luke'sScreenName
Elite Member
- Joined
- Mar 1, 2015
- Messages
- 3,710
- Location
- Lakes Region, NH
- Tractor
- Kubota MX4800 with BH-90X hoe; Hustler FastTrack 48; B3300SU (sold); 1969 Case 680B CK (sold)
Does anyone know how much vacuum (negative pressure) is needed to cavitate hydraulic fluid?
OP
Kodiak45
Gold Member
- Joined
- Feb 11, 2013
- Messages
- 322
- Location
- SC
- Tractor
- long 2460 - belarus 250 - JD 4230 - Kioti DK40SE
I plan on using the flow control valves when they arrive rather than the restrictor ports. So correctly me if I'm wrong, but I am going to put both of these controlling the exhaust flow on each port...right? I took the cylinder off tonight and brought it home so when I install the valves I can make sure all the air is out and hopefully my problems will be solved. The knowledge on here is amazing.
olPete
Gold Member
Yep that's the one! So the flow in is restricted but the flow out is not, as I understand it at least.
I'd maybe clamp it in a vise with the ports at TDC so the oil inside stays in, and you won't introduce any air that way, or have too much mess to contend with.. I'm nervous actually.. really hoping you get the results we're all after.. and it's not even my $$
( don't worry I've learned a lot on this thread myself, I'm just a farmer on the other side of the world.. I've always liked to see things as solutions yet to be discovered, rather than problems! )
npalen
Elite Member
I believe you should put restrictors of any type on the port where the fluid is coming out of the cylinder. This would be the port at the rod end in the case of a top link cylinder which would normally be in tension from the weight of the implement.
Putting the restriction on the base end of the cylinder only would tend to create a vacuum if the tractor pump wasn't able to keep up with the "free fall" of the cylinder when lowering.
Edit: Might be more accurate to say: With the restriction on the base port of the cylinder, the oil would flow out of the rod end of the cylinder faster that it could enter thru the base port restriction thus creating a vacuum.
Last edited:
