Hydrostatic pump question

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Dale_F
Posts: 77
Joined: Mon Jan 30, 2012 9:58 am
Location: Chiloquin, OR

Hydrostatic pump question

Post by Dale_F » Wed Nov 28, 2018 4:28 pm

I am working on my gas/hydraulic which has a hydraulic pump connected to a "log splitter". I want to replace this setup with a hydrostatic pump but am having a lot of trouble getting information and specs, and figuring out what I need.

My locomotive is a 7.5" SW1500 and has 2 hydraulic motors - one on each truck. The motor is a twin Kohler.

I have heard I should use an Eaton 6 or 7, but talking to an eaton distributor, he was completely confused. I have found an interesting option, but have no clue if it will work. It is a "Dixie Chopper 65070". Can someone look at this and tell me if this is the right direction? Cost is (of course) a huge priority.
https://www.dixiechopperpartsdistributo ... -Gear-Pump

I really like this option also, which is a replacement for the Dixie Chopper...
https://www.lawnmowerpartsworld.com/law ... p-10a-308/

I would welcome some ideas on what I can use. If you give me makes, I would sure also like specifics (like model). Again, cost is a huge consideration.
Thanks.

rkcarguy
Posts: 1247
Joined: Tue Aug 22, 2017 10:33 am
Location: Wa State

Re: Hydrostatic pump question

Post by rkcarguy » Wed Nov 28, 2018 6:52 pm

I just went through sizing pumps and motors for my 2" scale Baldwin S-12 project which is powered by a Honda GX390 and will also be hydraulic. There is a lot more involved than just buying some parts. The pump sizing relative to your gas engine, and the "fluid ratio" of the pump to the hydraulic motors and even wheel size is super important. The cubic inches per revolution, efficiency %, max rpm and torque, all play into what you can and can't use.
Being you have existing hydraulic motors on each truck, what's the specs on those, and what is your wheel diameter? Any chain or gear reduction between the hydraulic motors and axles?

ERIE S-1 BERKSHIRES
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Joined: Sun Jan 25, 2009 12:43 pm
Location: Barberton Ohio

Re: Hydrostatic pump question

Post by ERIE S-1 BERKSHIRES » Wed Nov 28, 2018 8:49 pm

I bought a non powered rail system fa from a friend of mine ,I put a Kohler Magnum 8 horsepower couple to an Eaton 11 pump the hydraulic motors on the trucks are 5.9 cubic inches Cheryl Lynn to this date no problems hydraulically been running since 2011

ERIE S-1 BERKSHIRES
Posts: 53
Joined: Sun Jan 25, 2009 12:43 pm
Location: Barberton Ohio

Re: Hydrostatic pump question

Post by ERIE S-1 BERKSHIRES » Wed Nov 28, 2018 8:54 pm

Also in the future I am building an SDP-45 Erie Lackawanna 3657 and I will do a hydraulic build series for the engine as when I build the engine I will do on step by step

rkcarguy
Posts: 1247
Joined: Tue Aug 22, 2017 10:33 am
Location: Wa State

Re: Hydrostatic pump question

Post by rkcarguy » Thu Nov 29, 2018 12:13 pm

ERIE, can you elaborate on your top speed, and are the motors plumbed in parallel or series?
There is next to nothing for pump/motor sizing info on here for gas/hydraulic builds and it would be nice to have more available.

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BigDumbDinosaur
Posts: 827
Joined: Tue Jun 28, 2011 9:19 pm
Location: Midwestern United States

Re: Hydrostatic pump question

Post by BigDumbDinosaur » Thu Nov 29, 2018 12:15 pm

Dale_F wrote:
Wed Nov 28, 2018 4:28 pm
I am working on my gas/hydraulic which has a hydraulic pump connected to a "log splitter". I want to replace this setup with a hydrostatic pump but am having a lot of trouble getting information and specs, and figuring out what I need.

My locomotive is a 7.5" SW1500 and has 2 hydraulic motors - one on each truck. The motor is a twin Kohler.

I have heard I should use an Eaton 6 or 7, but talking to an eaton distributor, he was completely confused. I have found an interesting option, but have no clue if it will work. It is a "Dixie Chopper 65070". Can someone look at this and tell me if this is the right direction? Cost is (of course) a huge priority.
https://www.dixiechopperpartsdistributo ... -Gear-Pump

I really like this option also, which is a replacement for the Dixie Chopper...
https://www.lawnmowerpartsworld.com/law ... p-10a-308/

I would welcome some ideas on what I can use. If you give me makes, I would sure also like specifics (like model). Again, cost is a huge consideration.
Thanks.
You are going about it all wrong. See above post about knowing pump and motor displacement, etc.
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I'm an old guy. What's your excuse? ☻

rkcarguy
Posts: 1247
Joined: Tue Aug 22, 2017 10:33 am
Location: Wa State

Re: Hydrostatic pump question

Post by rkcarguy » Thu Nov 29, 2018 12:35 pm

^^^^
BDD taught me well:) Plus a bunch of internet research and flow graph reviews from various pumps/motors.
Unfortunately I have found most in the hydraulics business don't know a whole lot about sizing the pumps and motors to obtain a desired ratio, so I have had to work them out myself using the cu/in specs and flow charts. Surplus center sent me some flow charts that show the GPM @ various pressures for the Dynamic motors.

ERIE S-1 BERKSHIRES
Posts: 53
Joined: Sun Jan 25, 2009 12:43 pm
Location: Barberton Ohio

Re: Hydrostatic pump question

Post by ERIE S-1 BERKSHIRES » Thu Nov 29, 2018 7:00 pm

The 11 gallon log splitter pump that rail systems used it's cubic inch was.711, the Eaton 11 pump is 1.15 cubic inch in gallons per minute on that pump was around 18 gallons flow rate. I believe the 5.9 H series Cheryl Lynn Motors are the only ones capable of flowing that amount of liquids, my locomotive can do pretty good speed if needed and the motors are in series it flows through the front one first and then to the back one

rkcarguy
Posts: 1247
Joined: Tue Aug 22, 2017 10:33 am
Location: Wa State

Re: Hydrostatic pump question

Post by rkcarguy » Thu Nov 29, 2018 8:17 pm

The 1.15 pump/5.90 motors sounds about right, that's what I've calculated for my locomotive project but due to fact I'm modeling in 2" scale I have 7" wheels, and have an 18/30 chain reduction off of the motors to the axles. This would be 1:1 direct drive if I was modeling in 1.5" scale with smaller wheels, but I choose to do it this way so I would actually have some adjustment beyond the hydraulics via the chain drive by simply changing the 18T sprockets.

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BigDumbDinosaur
Posts: 827
Joined: Tue Jun 28, 2011 9:19 pm
Location: Midwestern United States

Re: Hydrostatic pump question

Post by BigDumbDinosaur » Thu Nov 29, 2018 10:42 pm

In my F7, I'm using a pump with 1.79 ci/rev displacement, driving series-connected traction motors with 5.9 ci/rev displacement. This combination results in a theoretical speed ratio is 3.23:1. It doesn't sound like all that much "gear reduction," and wouldn't be except for two features. One is the hydrodynamic coupling between the prime mover and pump, which allows the engine to run much faster than the pump during train startup. The other feature is transition.

Transition has two states. When in low transition, some of the pump's output is directed back into its inlet through a valve-controlled "recycle circuit." This is similar to the principle on which a hydrodynamic torque multiplier (aka torque converter) operates.¹ The energy that is in the recycled oil is added to the energy being delivered into the pump from the prime mover—almost no energy is wasted. Due to the effect of the recycle circuit, the apparent pump displacement is smaller than the 1.79 ci/rev theoretical displacement (it works out to approximately 1.15 ci/rev in low transition). Therefore, the prime mover has to run faster in order for the locomotive to achieve any given ground speed. In exchange for the reduced speed, torque at the wheels is much higher, which translates into higher tractive effort. In low transition, the effective "gear ratio" is 5.36:1, neglecting slippage in the hydrodynamic coupling.

Upon switching to high transition, the recycle oil circuit valve is gradually closed. Now all oil flow is directed to the traction motors and the pump's apparent displacement is the same as its actual displacement. The effective "gear ratio" is now 3.23:1. Torque at the wheels is proportionally reduced but maximum speed is proportionally increased.

power_assy_es03_reduced.jpg
F7 Power Assembly: Transition Valve Lower Left


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¹In a hydrodynamic torque multiplier, a large difference in speed between the pump (the member driven by the prime mover) and the turbine (the member that drives the load) will cause oil flow to be recirculated back to the pump due to the action of the stator, which acts as a reaction device. The recycled oil's energy is added to the energy applied to the pump by the prime mover. The result is more force is applied to the turbine blades, producing higher torque. As slippage decreases, so does torque multiplication.
—————————————————————————————————
I'm an old guy. What's your excuse? ☻

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