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Loader Hydraulics


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#1 cpg OFFLINE  

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Posted November 03, 2014 - 10:57 AM

I found some steel and I am seriously considering building a loader for my Cub Cadet 107. If has a few places where I can run a hydraulic pump and to be cost effective my idea is to get a log splitter pump to run the loader hydraulics. The ones I found are 11 gpm which seems like it would be enough for a garden tractor loader with how small the rams will be. I know the gpm drops off a lot when it goes to the second stage so it will be slower but maybe that will just give me more power for heavy loads? I know there are loaders out there for these tractors and just wondering what people have for pumps.



#2 Auburn David OFFLINE  

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Posted November 03, 2014 - 11:51 AM

I am one of them use what you have type shade tree builders..it always seems to work out fine...even when it shouldn't...LOL



#3 TUDOR OFFLINE  

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Posted November 03, 2014 - 01:59 PM

a) FEL hydraulics for a GT require no more than 6 gpm at WOT. You will not enjoy trying to control a loader at 11 gpm! Controlling one at 6 gpm is a right proper witch and not for the inexperienced operator.

 

b) With 2x18 lift cylinders, the 900 psi normal unloading setting for a 2-stage pump will lift about 900 lb.

 

c) All new hydraulic components for a GT FEL cost north of $1000. The most expensive component being the collection of hoses and fittings required to connect everything.

 

If you mismatch hydraulic components badly like that, having it work anywhere close to correctly ain't happening.


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#4 Cvans OFFLINE  

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Posted November 03, 2014 - 08:46 PM

Kept blowing the seals on my loader pump. Talked to Surplus sales and they said that my pump was too large for my reservoir thus cavitating the pump. If your reservoir holds 2 gallons your pumps output should not exceed 2 gpm. This should be great plenty for a GT's small loader cylinders. 



#5 TUDOR OFFLINE  

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Posted November 04, 2014 - 12:36 AM

Kept blowing the seals on my loader pump. Talked to Surplus sales and they said that my pump was too large for my reservoir thus cavitating the pump. If your reservoir holds 2 gallons your pumps output should not exceed 2 gpm. This should be great plenty for a GT's small loader cylinders. 

The proper size pump should have sufficient flow to raise the arms of a FEL 10" per second at operating speed. For my GT, that's 7 seconds to 71" above ground at the lower bucket pin. That's at 2/3 throttle with about 4.6 gpm flow.

 

For a stationary hydraulic system, the rule of thumb is a minimum of 2 gallons of reservoir capacity for each gallon per minute of flow. Mobile hydraulic systems do not have the luxury of having that kind of volume available and use the less restrictive rule of thumb of a minimim of 25% of maximum pump flow required for reservoir capacity. In some applications, less than 10% has been the norm for decades. The power steering pump in a car flows about 2 gpm, but the reservoir holds considerably less than one quart.

 

The ideal reservoir for a loader is the posts. They are tall and thin, affording lots of cooling surface and adequate head for the pump to draw from without creating a vortex which will allow air to be pulled into the pump supply line. It also ensures that the pump supply port is flooded with no vortex no matter what working angle the tractor occupies.

 

The reservoir capacity on my loader is nominally 2 gallons and the max pump flow is 6 gpm. The pump has given no problems in over 1000 hours of use.


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#6 cpg OFFLINE  

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Posted November 04, 2014 - 07:34 AM

I did some research and would a large truck power steering pump work? I know they run over 1000 psi which should be enough and I read that some will put out around 4 gpm. I plan on using a 5 gallon reservoir I have so fluid volume shouldn't be an issue. My brother had an old truck with power steering pump lift for a plow and it would lift the plow really fast. I know that was only one lift cylinder but it didn't seem like an especially large power steering pump either and I have heard of people using them for 3 point lifts on a GT.

 

Another possibility I thought of was that the splitter pump I was looking at is rated for 3600 rpm. If I had it belt drive off my accessory pulley could I just use a larger pulley to slow it down and drop the gpm? The issue there is that I'm not sure if it would also drop the pressure.


Edited by cpg, November 04, 2014 - 07:37 AM.


#7 Cvans OFFLINE  

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Posted November 04, 2014 - 02:04 PM

I used a Truck steering pump to lift the dozer blade on an old WC Allis Chalmers for years without any problems. Ran it off of the side PTO pulley.  Also planning to use one to lift the tiller on a Craftmsn gt18. I did enlarge the oil reservoir the WC and will do the same on the GT18. The reservoir on the WC held no more than 2 quarts after being modified but was only supplying one short cylinder. 

 

The pump on the Bolens is now is just less than 1 gallon per minute. It works ok but next time I would probably go a little larger. 


Edited by Cvans, November 04, 2014 - 02:08 PM.

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#8 Auburn David OFFLINE  

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Posted November 04, 2014 - 02:13 PM

I am getting some good info off this post for my hydro mower deck project..thanks everyone..keep the info coming.


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#9 TUDOR OFFLINE  

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Posted November 04, 2014 - 02:28 PM

WIll the pump from a heavy truck work? Yes.

 

Will it be satisfactory for a FEL? Ummm, not really. P/S pumps are flow controlled to their maximum flow rate and attain that rate at about idle for a GT engine. They will flow the same amount of fluid at idle or WOT. This is not what you want when making precision lifts, eg. loading an engine into a tractor, or an air conditioner onto its stand. For that type of lift you want a much lower flow rate. With a reqular pump you can adjust the flow rate with the throttle. For lifting or lowering implements, lift speed is normally not a critical consideration, although lifting a heavy tiller at high acceleration rates is not going to do the lifting device any favours when it come to the end of its travel.

 

Normally, pump rpm affects flow rate only. It has a very limited affect on pressure. If  you want to use the splitter pump, the pump needs a pulley almost twice the diameter of the one driving it. While a splitter pump will work at 600 rpm (engine idle, 2:1 reduction), it will not flow at its best at pressure due to normal internal leakage for lubrication.

 

Hydraulic lines are sized to accomodate the flow rate. Maximum flow rate for 1/4" hose is 5.6 gpm. Most applications will use 1/4" hose for up to 6.1 gpm because WOT is rarely used for FEL work. For an 11 gpm flow rate, 1/2" hoses are required. The price of fittings and hoses rises fairly quickly as the sizes get larger.


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#10 cpg OFFLINE  

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Posted November 04, 2014 - 10:58 PM

Thanks for all the help and input. I have been struggling to find a smaller pump which is why I asked about the power steering pump though not ideal. However, I just found that Northern Tool carries a small hydraulic pump rated at 7.8 gpm at 3,000 rpm so I could gear it down just a little and should be right in that ideal range to control the loader speed with my rpm. It looks like I can get some hose at tractor supply for a fairly reasonable price, especially since they will only be going on a small loader. It looks like the most expensive piece will be the two spool valve.



#11 Cvans OFFLINE  

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Posted November 05, 2014 - 12:21 AM

Mine was purchased from Surplus Center and they have them in all sizes and capacities. 



#12 TUDOR OFFLINE  

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Posted November 05, 2014 - 12:51 AM

Pump displacement should be 0.36 - 0.39 cu-in.

 

This one has a 1/2" shaft.

 

This one has the 5/8" shaft that I prefer.

 

Pay attention to the direction of rotation. Many don't work so good when turned in the opposite direction.

 

There are 11-15 hoses required for a FEL, depending on whether or not steel tubing is also used. Long lengths of hose have a tendency to 'walk' with the pressure variations and make loops that are not pretty to look at. Steel tubing, while not expensive in its own right, has tooling costs attached that will get your attention. You need a bender and a 37° flaring tool. The complementary steel tubing for 1/4" hose is 3/8"x .035" wall.


Edited by TUDOR, November 05, 2014 - 01:08 AM.

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#13 Cvans OFFLINE  

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Posted November 05, 2014 - 01:11 AM

Steel tubing also does a much better job of dissipating heat. Excessive heat can be very destructive to a hydraulic system. 


Edited by Cvans, November 05, 2014 - 01:12 AM.


#14 cpg OFFLINE  

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Posted November 06, 2014 - 08:27 AM

I actually do have some manual tubing benders and a flaring tool so that might be the way to go for the long lengths. Thanks for all the help; at least I have a better idea of pump and hydraulic needs.






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