TnT on B2910 still need help.

[gotrocks]

TnT Kubota B 2910
Where to start, "With a little help WHOLE LOTTA HELP from my friends"
Especially Bird, Mike and Ron and my local buddy where I purchased the fittings & hoses.

July 24, 2007 6C040-95100 Hyd outlet kit Received July 26, 2007 77.52
1-800-488-3407 Surplus Center Tanya 12:52 PM
July 26, 2007 9-7470 2 spool valve\ 79.99
9-7258-12 hyd cyl = 94.95 17.90 267.79
9-7258-4 hyd cyl / 74.95

August 3, 2007 Pick up salvage SS trim tab, cut & fit to bolt on ROPS for valve mount
August 7, 2007 Cut/weld cylinder Go back move retainer clip for ratchet handle
August 8, 2007 Pick up balance of fittings and hoses 160.43
After receiving the valve and cylinders I decided to mount the valve one the back of the right fender. One of my sons had a discarded SS trim tab from a boat so I got the abrasive blade and cut me a bracket (pic) Bored 2 holes to match ROPS bolts then 3 small holes to mount the valve. (Cut too small for access to pressure valve, see below)
Cut the ends off the short cylinder and cut the clevis ends off the fixed link from tractor, that made it easier to keep the 15 degree angles when welding to cylinder.
We pulled the piston all the way out and weld a little then immerse a little in water being careful to keep water out of cylinder. Middle of cylinder never got too hot to touch.
Mounted everything and cut old garden hose to check length of each hose.
Put quick connects on the top link, since it has to come off to use PH digger.
Start up oops, 2 connections not tight. They are now. No leaks.
Side cylinder will not lift roll over BB.
Called tech support to ask about loud squeal- Dave said try adjusting the pressure.
Since it is now mounted and hooked up I cannot adjust the pressure without removing it from the bracket. (Oh well, when it is adjusted maybe it will stay adjusted) Not done yet. 8/8/07
8/9/07 Was able to loosen valve from mounting plate with all hoses connected.
Got pressure to valve, at present I am increasing by ¼ turn at a time blade will now lift but blade drops while sitting. "A little knowledge is a dangerous....."
I’ve just about bottomed out on the valve and there is still a little drop with Kub running.
Should I run pressure all the way in till it does bottom out?
It is lifting and seem to be working OK in that regard. It just does not "stay put."
I just read a post that mentioned a pilot valve on cylinders, I don’t think I have that.
Is that something that is required to stop the movement of the cylinder?

 

[RonMar]

NO. IF you are going to mess with pressure settings on relief valves, you NEED a pressure gauge installed, if only temporarilly to setup the relief. Setting up incorrectly could damage lines, cylinders, valve blocks, seals or the pump itself...

The cylinder leaking down could be one of several things:

1. There is still air in the cylinders and it is slowly being purged past the piston seals when the cylinder is under load. This should eventually clear itself and the drooping symptoms go away. You can speed this by disconnecting the lower link, fully retracting the cylinder(fill the lower portin of the cylinder with fluid) Then stand that end of the cylinder upright and allow any trapped air to rise toward the hose fitting. Then fully extend the cylinder in this position and allow the fluid below the air to force the air out the hose and back thru the valve.

2. A pilot valve is basically a type of pressure activated check valve located at the cylinder that seals off the cylinder when no pressure is applied from the valve. A spool valve can leak back pressure past the machined portions of the spool, particularly if the cylinder is under heavy load(small cylinder making high pressure due to the weight it is supporting, see number 3 below). If you search around on the net, you will see pics of a hydraulic toplink that has a pilot valve at the cylinder. Usually looks like a metal block on the side of the cylinder(where hoses attach) with hard metal lines to the cylinder ports. Yours do not have them...

3. The cylinder is not large enough for the job and is exceeding relief pressure thru dynamic movement or leaking fluid past the piston seals. If you get me a few dimensions, we can calculate how much force is needed and how much is available from the cylinder. I need to know the following:
A. System rated hydraulic operating pressure.
B. Cylinder bore/stroke and rod diameter.
C. Length of lower lift arm from balljoint/pivot center where it attaches to the tractor, to the impliment lift pin center.
D. Distance along lower lift arm from where it attaches to tractor to where the cylinder attaches.
E. Total weight of box blade and distance from lift pins(where lift arms attach) to the middle of the box. A pic of the box would be nice also so I can estimate where the Center of gravity of the box is, based on mount structure, blade and scarifier locations.

 

[MJPetersen]

Called tech support to ask about loud squeal- Dave said try adjusting the pressure.

This squealing is a bother to me too. What is squealing? Is it the relief valve, the pump or something else? If the relief (often factory set for around 2000 psi) then is it caused by low setting (PLEASE DO NOT SET WITHOUT A GAUGE), overloaded cylinder (too small for the load), or restriction in line or connections. If the pump, could be cavitation, caused by air or low oil flow in the pump suction line. What causes that? Low oil level, plugged suction screen or filter, or air leak in suction line (You did not run the return from the valve to the suction line of the pump, did you?).

I am trying to figure out from your description what exactly is going on. Maybe a pic is in order.

Mike

 

[gotrocks]

Thanks Mike and Ron,
I have to fill in for a sick worker to day and next week.
But I will get some answers to your questions ASAP.

 

[3RRL]

I'll bet the squealing is like groaning or creaking when the cylinder pulls in or retracts because of the load on it. It may not be large enough for the job and the rod is flexing slightly due to severe load?

 

[gotrocks]

Ok all you great guys, Mike Rob Ron and Bird, I'm back at it.
I think the squeal I mentioned was the first use without any implement attached and was just "blowing" the air out on the first few extention/retractions. It seem to have stopped now.

I have been doing some additional calculations since your questions regarding lenth of lift arms etc.
When I was ordering the cylinders it was suggested that I get at least a 1" rod.
That I did BUT I only ordered a 1 1/2 " piston. I had callculated this as
Pi * R square. .75x.75= .5625 x 3.1416= 1.767 x 1900 psi = 3357 lbs.

BUT I did not consider the mechanical dis-advantage to the lift arm set up.
Now since your mention of arm length DUH, now I come up with the following
(see pic)
Arm pivot to lift point 12" to end of arm + 12" ctr implement 39" 12/39= .307 MA
.307 x 3357 = 1030 lbs

Since these are not exact measurements the answer seem to be,
I'm squeezing the juice out of my T&T. Looks like I should have ordered 2" cylinders.

What say you (all) to these conclusions?.
Should I get larger cylinders or wait until I blow these up? (can that happen?)

I thought that since Kub book states Max pressure 1920-1992 psi
and everything ordered states 3000 psi everything would be OK as far as psi was concerned.

 

[Bird]

Should I get larger cylinders or wait until I blow these up? (can that happen?)

I'm afraid you're getting into something now that I don't know enough about to help you. I would have used 2" cylinders alright to start with, but I don't know how much difference it'll make, or whether you'll blow the seals out of the smaller ones or not.

 

[RonMar]

Actually I think you missed something in your calculations. That force you calculated based on a 1.5" piston(.75" radius) will be for the pushing force of the cylinder. You are using the pulling action of the cylinder to lift the weight. You need to subtract the rod diameter area(.7854 SQ/IN) that covers up the piston face, from the piston area when retracting. That leaves you with .9816 SQ/IN on the retract side of the piston X 1900PSI for a force of 1865 LB. Using your moment arm figures, That only gives you 572 LB of force at 39"...

I think you need bigger cylinders.

 

[gotrocks]

Ron, it is a delight to hear from you.
You have brought an important fact to my attention, too bad I did not consider the rod dia. in my calculations.
What was the old TV Gillett commercial "Push Pull Click Click,, change blades that quick"
Or I guess that's why one does not want to get the cart before the horse.
He can pull more than he can push, but hyd cylinders can push more than they can pull.
Enough of this, I just want to make sure any others that consider this kind of project for themselves are aware of the different capacity to PUSH & PULL.
Live and learn, die and forget it all!
I have ordered 2" cyl with 1.25 rods, ball park they will pull twice what the 1.5 cyl will do.

When they are changed out I'll post another pic or two.

 

[rural2]

I don't have an opinion on all the hyd. calcs. and not even sure if this info will have any value to you at this point. But, I do know this works on my B7800.
Top cyl. = 2 3/8", ram = 1 1/8"
Tilt cyl. = 2 7/8=, ram= 1 1/8"
No weird noises and they have done everything asked of them.
The tilt cyl. leaks down apx. 1/8" every 20 minutes when the tractor is running, slightly more when the tractor is not running. The top cyl. has a DPCV with zero leak down near as I can tell. I plan to add another DPCV just like it to the tilt cyl.