What are you trying to accomplish?
I'm mentioning Darley because that is what I'm familiar with. Hale and Waterous make good pumps too.
We have a truck buillt on a Ford 800 with a front mount pump that can pump and roll. It has a Darley 750 gpm 2 stage pump, and can exceed the 750 by a good margin during pump test from draft.
Darley makes at least a 1500 front mount pump, although not all engine manufacturers rate their engines for that much flow driven from the front hub of the crankshaft
Darley also makes a hydraulic driven pto pump that they rate up to 1000gpm. The advantage of hydraulic drive is that it can generate the pump volume independent of ground speed.
In real world applications, I don't know why you would need that much volume for pump and roll. The pump and roll is of benefit in a brush fire.
If you have your heart set on pump and roll, and 1250 gpm then a conventional chassis rig with a front mount pump may be your best bet. (or least expensive option)
Another way to do this with a midship rig is to add a separate pto pump for the pump and roll. If you are wanting to flow several remotes or boosters for brush work, a separate 250-350 gpm pto pump should be adequate.
Our pump and rollin' engines
The Brush Engines that we have in the two Departments where I work vary..... at one Department, we have a combination of P.T.O. driven pumps. At the second Department I work for (a much larger Department) we have Auxillary driven pumps.
My personal preference is the Aux. driven pumps. Some of the advantages are: Totally independant of the vehicle motor (simply put..... you can pump whatever p.s.i. you need, no matter what speed you are driving..... or not driving), Aux. pumps' fuel lines can be tied into the vehicles fuel tank/system, Aux. pumps are so easy to use and operate, Aux. pumps truly "pump and roll", certain hoselines or all hoselines can be tied into the Aux. pump, still have the capabilities of flowin' Class A/B foams, modern Aux. pumps only have one button to start and engauge the pump, are very simple pumps..... so when something goes wrong.... it is very easy to troubleshoot.
Disadvantages are: It' s another pump that must be checked daily/weekly or whatever your Department S.O.G. states, Aux. pumps are normally limited in size (the largest I have seen is 500 g.p.m.), Aux. pumps may take up a little more space than other pump types, yearly drafting certifications are required even for Aux. pumps.
In my opinion, for wildland........ there is no pump that even comes close to the Aux. pump. In So. California, we know a thing or two about wildland fires.
Pump and Roll imformation
I hope this helps you on the matter of pto’s and pump and roll . the simplest pto on our cars are power steering pump and alternator these are belt driven pto’s. even the transmission and drive train are pto’s. an other example is a riding lawn tractors cutting deck to farm tractor rear output shaft . Commercial applications are garbage trucks but some units can not engaged the pto in drive.
Cement trucks, tow trucks, and those in the snow belt most state and local plow and spreaders run on ptos.
In the fire service most standard fire engines pumps are a type of pto . At the rear of the drive engine to the drive transmission to a transfer case from there it either goes to the drive train or pump gear . As for pump and roll fire fighting units (wild fire units) there (for this) 3 basic types of pumping systems on these unit.
There are auxiliary engine/self powered pumps from simple 50 gpm gasoline pumps up to 1500 gpm diesel powered pumps . The larger gasoline and diesel powered units can get certified the same as a standard fire engine . For brush truck/grass unit 4 types of basic pumps 1) low pressure /regular volume 2) regular pressure/regular volume 3) high pressure/regular volume 4)high pressure/low volume (like pressure sprayer pumps) also CAFS systems . The first 2 are generally single stage centrifugal pump the third multiple stage centrifugal pumps or positive displacement pumps and the fourth generally use positive displacement pumps are piston, diaphragm ,roller-tubes/vane or rotary gear pumps .
Then the basic pto pump and roll units are powered off the truck engine. They are connected to what we call power several ways . 1)Belt drive like the power steering pump.2) the front fly wheel where generally where the belts are connection. A larger pulley is added . 3) if there is a gear (front fly wheel) behind the belt pulley access and away to bolt a the pump on to the engine. 4) connected to the rear engine fly wheel before the transmission 5) some truck manufactures have placed access ports on the transmission this is a connection point. 6) access port on a 4x4 transfer case 7) a transfer case is added between the transmission and rear axel 8) by extending or placing the front drive shaft
The last type of general type of pump and roll system is a hydrostatic pump system this is a 2 pump system the first pump is a hydraulic pump that powers the firefighting water pump . The hydraulic pump is connection pretty much like the first type of pto pumps then powers the firefighting pumps . In my research I have found a company makes a hydrostatic pumps up to 1500 gpm .
As with the 2 basic pto pump and roll pumping systems they have the same pressure/volume styles of pumps as the self powered .
The last system is a pressure vessel tank system . This is generally for uses in the home/ranch/farm ,industrial ,and/or airport use. The are water system, compressed air foam system , wet chemical and/or dry chemical systems. The unit consist of a steel round tank in which water and/or foam or other chemical up to the ¾ of the tank and then it is pressurized or a 2nd tank of air, nitrogen , or co2 to charge the tank to the discharge point. Generally this system is the best compressed air foam system . But it has one major draw back when you are out of the pressurizing agent the system no longer works till it is refilled again. But it require the lowest system maintain.
There are advantages and disadvantages to all the systems.
Here is pro’s and con’s sheet I found several years ago from a company no longer in business
Pump and Roll Capabilities For an interface type engine to function effectively, it must be able to pump and roll, or be able to flow water while the vehicle is in motion, and have a large GPM capacity for structural firefighting. Small skid mounted pumps are great tools for fighting grass fires, but the output volume of the pumps is very low. On the other hand, split shaft pumps on full size pumpers have the volume, but they can't pump and roll.
For years, fire apparatus have used PTO (Power Take Off) driven pumps to accomplish this requirement. PTO units are attached to the vehicle transmission or flywheel and allow the pump to turn while the vehicle is stationary or traveling. This allows a vehicle to pump and roll. However, the pump pressure is tied directly to the engine RPM, which causes the nozzle pressure to rise and fall as the vehicle speeds up or slows down. This does not make for good firefighting, especially for the person on the nozzle.
There are two methods of driving a water pump that provide a large volume output along with pump and roll capabilities that have proven to be very effective...engine driven pumps and hydrostatically driven pumps. Let's take a look at both and learn more about them.
Engine Driven Pumps
Just as the name describes, the pump is driven by an engine that is independent of the chassis engine. The pump is attached to the back of the engine, driven directly off the crankshaft. This combination is typically mounted to the frame rails just behind the cab, basically in the same location as a traditional cross mount pump.
Small diesel engines work perfect for this application due to their low maintenance, long term durability and low heat output. Due to the close proximity of the water pump to the engine, the low heat output is critical in reducing the possibility of cavitation of the pump. In the past, when gas engines were used for this application, the engines produced an excess amount of heat, which could not be dissipated before reaching the pump housing. The heat would raise the temperature of the water in the pump, causing cavitation.
Since the pump is driven by an engine that is separate from the chassis engine, it does not care whet speed you are traveling when you want to flow water. It can be a 2 MPH crawl, or a 50 MPH blast down the freeway, the water pressure will not change as a result of road speed. These pumps are typically set up with controls at the pump panel as well as in the cab, allowing the apparatus operator the ability to control the pump without leaving the drivers seat. The pump can even be fired up and ready to go as you are arriving on scene.
With an engine driven pump, you have the option of pumps ranging from 750 GPM up to 1,250 GPM. These are rated fire pumps, capable of handling any structural needs you may have, and meeting ISO ratings for a structural engine.
All the desired accessories that are installed on traditional pumpers can be installed on an engine driven pump, such as foam systems and electronic controls. Some manufacturers have even developed CAFS units that are built as an integral part of the engine driven pump, eliminating the need for a separate compressor motor.
Hydrostatically Driven Pumps
When you require a compact interface pumper that provides structural capabilities, yet you do not need to meet ISO ratings, there is no better system than the hydrostatically driven pumps.
Hydrostatic systems are well known for their use in cement mixers and farm equipment, vocations that require the ability to provide constant component operation, regardless of engine speed. These systems must operate constantly, any time the vehicle is in operation, so long term durability is of utmost importance.
A hydrostatic system consists of a swash-buckle type hydraulic pump that is attached directly to the engine crankshaft, which in turn spins a hydraulic motor that is attached to the water pump. Even at an idle, this type of system is capable of achieving 100 GPM at 100 PSI. Increasing the RPM increases the speed of the pump, increasing GPM and PSI accordingly. Typically to get the most out of a hydrostatic system, a two stage pump is utilized.
This system works perfectly to provide a 500 GPM pumper on a short wheelbase chassis, since the system takes up little room and does not require a transfer case in the drive system.
This is also one of the simplest pump systems to operate, since all you have to do is flip a switch and turn a knob and the pump is in gear and producing water. With in cab controls, the driver can operate the vehicle without leaving the cab.
The state of California Fire Department has been using hydrostatic pump since about 1980’s in their model 05,14,15,and17. For more information check out Roscommon Equipment Center
answers to comments/questions
“because basic pto pumps you are at the mercy of the rpm/speed of the truck. which is no problems when you are not moving you can ramp up the rpms/engine speed.. but when you are going do that field at 2 mph and trying to get a nice stream .. it is not going to happen..”
With a 1st gear ratio of 4.59:1 and the selectable low range rear end ratio of 7.39:1, we’re confident (at least mathematically) that we’ll achieve a ground speed of approx 3mph at 1100rpm. This speed will be further reduced by ground that is softer than pavement.
The PTO pump will be geared (PTO & Pump Transmission) to produce 100 gpm at 100psi at 1100 rpm engine speed (the speed of the impeller is 4500 rpm). The Firefox bumper turret has a selectable flow that will most likely be set at 30gpm.
On the PTO pump side (totally independent of the main midship pump through a check valves) is a Darley pressure relief valve that is adjustable (Darley says 75-800psi). This is important because when the driver goes above 1100rpm the additional pump pressure generated will be returned to the booster tank. This allows the driver to have his foot to the floor (2200 engine rpm and an impeller speed of 9000 rpm) and the pressure generated is still 100psi / 60gpm. Of course the pressure relief valve allows us to either reduce or increase the pressure to tweak the flow. This paragraph was worked out with the Waterous engineers.
“My question was to Firefighter1692. Why a Waterous and not a Darley pto pump. I would think if possible you would be better off with the same make. One could also ask, why not a Waterous main pump.”
We saw the Waterous pto pump in service, although it did not work well, due to bad gearing. Quite simply the truck moved too fast to be effective, and when the truck was slowed to a manageable speed the flow was not there.
We studied the data of how that particular truck was designed, and discovered that with proper gearing it could be made to travel at a crawling speed (1100rpm engine speed). Conversely with the foot feed pinned (2200rpm), the pto pump impeller turned near it’s upper limit of 9000rpm.
Now why Darley? It’s not a popular pump in this part of the world. We found that in regard to pumps it got into that Ford-Chevy-Dodge debate.
Everyone that did not have a Darley could not tell us why, and everyone we talked to that did have one were happy with it. The US Navy uses Darley fire pumps.
The feature we really liked with Darley was the check valve between the pump discharge and the main manifold.
This did two things for us.
First, since this is a rural responding truck that relied heavily upon drafting, the check valve means that the operator does not have to shut the discharge lines to prime the pump. While this may not be as important on initial setup, sudden loss of prime while members are in the structure needs to be dealt with quickly.
Second, it isolates the main (Darley) pump from the main manifold when the PTO pump is using it (the manifold). We were not sure what the effect may be (seals. etc), of subjecting a pump to 100-400 psi from the other pump through the discharge and turning the impeller the opposite direction. So we just decided to isolate the two systems and not take any chances.
Another feature we liked on the Darley pump was injection packing.
There were other considerations, but this getting long……
Hope this helps, stay safe