Eastern Power Equipment 

285 Route 9  PO Box 97  Barrington, NH 03825

Phone 603/664-7776  | Toll Free 866/664-7776 | Fax 603/664-7420  | email chuck@easternpowerequipment.com

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Understand your power-source options

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Your A.R.A.-affiliated rental professional can help you determine the power source to fit the job.
Most rental tools require a power source - LP-gas, propane, gasoline-or diesel-fueled engine, compressed air; or electricity – to function. So it’s important to know your power-source options, and how and why one option may be better than another for the work you’re doing. Count on your A.R.A.-affiliated rental house for help in determining your exact needs.

Understand your power-source options
Your A.R.A.-affiliated rental professional can help you determine the power source to fit the job.
Most rental tools require a power source - LP-gas, propane, gasoline-or diesel-fueled engine, compressed air; or electricity – to function. So it’s important to know your power-source options, and how and why one option may be better than another for the work you’re doing. Count on your A.R.A.-affiliated rental house for help in determining your exact needs.

• The Lowdown on Engines
  Conventional Piston Engines – 2 and 4 Cycle
  Two-cycle piston engines -- Engineering has led to advancements in two-cycle engine design. Today, engines are more fuel efficient and cleaner burning while maintaining the power-on-every-stroke feature and longevity that they are well known for.
  Compact, lightweight, two-cycle engines are:
• Usually air cooled
• Great for many hand-held tools, such as trimmers, saws, vibrators, rammers
• Required to use a special oil/fuel mixture
  IMPORTANT! Follow exact specifications for two-cycle engine oil-to-gas mixture.
• Four-cycle piston engines – The majority of today’s rental engines are four cycle, and are fueled by either gasoline or diesel. Other than keeping an eye on oil and coolant levels, and replacing filters when recommended, four-cycle engines are relatively trouble-free and long-lived.
  Small engines = up to 25 hp
  Medium engines = 25 to 100 hp
  Large engines = 100 hp and above
• Medium and large engines tend to be liquid cooled rather than air-cooled
• All four-cycle engines are lubricated by oil from a bottom pan or sump
• Most modern engines have an auto shutoff feature when oil levels dip too low
  IMPORTANT! Maintaining the proper level of oil is critical.

Which is Best – Gas or Diesel?

Engine manufacturers offer these observations about how to choose between gas or diesel fueled engines.

• Gasoline engines:
• Typically are less expensive than diesel engines
• Start better in colder weather because gasoline does not gel, as diesel fuel has a tendency to do
• Run much quieter and cleaner
• Can be fueled easily. Not all service stations carry diesel fuel
• Are lighter than diesel engines, a factor in the overall weight of equipment
• Diesel engines:
• Last longer
• Require less maintenance
• Are more fuel efficient
• In some cases, approach the light weight typical of gasoline engines
• Rely on compression ignitions that are, in most cases, built with stronger components and higher torque backup. Click here for more information on torque rise
• Usually have a higher original purchase price, but longer life in the field
• Can survive under more rigorous conditions
• Are now available for compact, medium-sized and small machines

What’s So Important About Torque Rise?

Torque rise, or torque reserve, is a measure of lugging ability (low-end power) when the going gets tough and the engine revs down. If your engine came from the United Kingdom, specifications may refer to “torque rise” as “backup.”

General rule of thumb – The more torque rise, the better! The engine may sound like it’s about to bog down and stall, but then it just keeps on churning, like the Energizer bunny.

You can feel, hear and mathematically see torque reserve. Your A.R.A.-affiliated rental expert can look up “peak torque” and “torque at rated horsepower” on the engine spec sheet. Then, to determine torque rise:

• Divide peak torque by torque at rated horsepower
• Carry it out to two decimals
• The answer will be “1” followed by a two-digit number that represents torque rise, expressed by a percentage.
  Example:
  1.27 = 27 percent torque rise
  A rating of 30 percent would be better yet
• High torque rise is especially important in such machines as articulated wheel loaders, for instance, which lug down as they burrow into a pile of dirt or begin to dig.
• On machines like excavators and backhoes, you can hear them respond to the increasing load as the crowd cylinder forces the dipperstick through the pass and the bucket curls into the dirt. If they stall out, they may not have the torque reserve to handle the load as it builds up.

Your Rental Pro Can Help

No matter what type of engine you and your trusted A.R.A.-affiliated rental expert agree on to do the best job, it’s important you know how to start and maintain the engine in the field.

Familiarity is key. Save time at the job site by having your rental professional show you how to:

• Check the oil and fuel levels
• Make sure the fuel supply is on
• Operate the choke and ignition switch

Your rental expert can share important engine specifications to help determine the right engine for the job. Before you go, here’s some great information to know.

• Many engines 50 hp and above are diesel, especially in applications that require the engine to run at a constant rpm – usually under 3,000 rpm for peak efficiency – for long periods, such as on a pump or generator.
• Diesels are more robustly designed for durability and are about 40 percent more fuel-efficient than comparable gasoline engines.
• Engines made in the United States are rated in SAE or brake horsepower. They are tested to strict standards of a dynamometer to produce a measure of horsepower at a given rpm.
• Torque – the ability of an engine to produce rotation with a given force – is rated in foot pounds and is a good spec to be aware of:
• Engines with high torque are better able to handle a heavier load at lower speed.
• Engines with less torque have to wait until higher rpm is reached before producing full power.
• Because of their design, diesel engines are typically used in high-torque applications.
• In some instances, too much torque could produce too much power at the wrong speed and damage the engine and whatever it is powering. On the other hand, being “over engined,” with too much horsepower and a high rpm can wear out clutches and take a toll on equipment.

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Generators  

Choosing the Right Generator

Generators rated 2 through 10kW (10,000 watts) are the backbone of the portable electric power rental market.

Smaller units – 16 watts to 1 kilowatt – are typically for homeowners, do-it-yourselfers, campers or emergency use

Larger units - may power an entire job site, run a particularly large piece of

equipment or supply standby power

While most have gasoline engines, diesel-powered generators are preferred by contractors who have a lot of other diesel equipment on site and a ready supply of diesel fuel.

Generator rentals begin with your A.R.A.-affiliated rental expert asking you the simple questions:

1. What are you going to run?
2. How long will the job take?
3. What’s the typical load on the generator?

• To determine the right size generator, your rental pro will check the nameplates or manuals to determine wattage of the equipment (lights, tools, heaters, etc.) to be connected to it.
• Your rental pro will put all these factors together and select the proper unit that allows for some reserve power.

General rule of thumb: It’s always better to oversize than undersize when matching the generator to the intended use. For example:

• If you need to run two circular saws and a drill, and you and your rental expert figure the total consumption will be around 3,500 watts, then it’s best to use a 4-kW generator because it has a built-in cushion factor. Larger generators also will have more plug-ins.
• Another reason for slightly oversizing the generator has to do with how a typical electric motor ramps up to speed. Depending upon its efficiency, an electric motor can consume two-to-three times its rated power draw until it reaches its proper rpm. Most generators can handle this under surge-load conditions. On the other hand, resistive loads (lights, heaters) will consume only their rated power throughout when they are in use.

Tips From Your A.R.A. Rental Pros

Your A.R.A.-affiliated rental expert can help you keep up with advancements in generator technologies, and provide you with other information. Here are some things they would like you to know:

• Besides the given horsepower of the engine, your A.R.A.-affiliated rental pro can help you understand important specifications such as maximum (or surge) output and rated output.
• Heat is the biggest cause of generator breakdown. Voltage drops as the result of overloading from excessive power demands and can cause motor burnout as well as wiring and insulation damage.
• Voltage drops are also harmful to the electric tools being used. Better generators have thermal or electromagnetic breakers to prevent this from happening.
• Trouble shooting includes checking gas and oil levels. First make sure the unit is on a level surface, then check for a tripped breaker, overloaded receptacles, ground-fault interruptions, incorrect use of extension cords and low oil shutoff.
• Most generators today are of the newer brushless design, especially in smaller units. These are typically low-maintenance items and need little more than an oil change at the recommended intervals.
• Better generators are 120/240v switchable. Most contractors prefer 120v, but there is the occasional need for 240v to power tools such as core saws and breaker hammers.
• Fuel run times are rated in no-load, half-load and full-load conditions, and by tank size.
• Larger electric-power delivery devices include gen-sets, and fully integrated matched or coupled engine/generator units that deliver large amounts of power. These range from 8kW to 200mW and are used for light towers, load banks (multiple plug-ins) at special events, chillers during power interruptions and many other applications.
• Generators may be pad or trailer-mounted and can be specified for prime or standby power.
• Long-term use includes load shedding and peak sharing when the local utility grid cannot reliably or efficiently meet the needs of the user.
• Add-on rentals may be needed and include electric tools, lights and components required by the tools themselves, such as saw blades.

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Compressors 
Determine the Right Compressor for the Job

Air compressors range in size from small, extremely portable units for rooftop use up to tow-behind, diesel-driven behemoths that are as big as a compact car. In determining the proper size of compressor to handle the job, the number and types of tools you plan to connect to it are important variables to share with your rental expert.

• Small – 4 cfm or below are:
• Diaphragm-type, as opposed to piston (reciprocating style) compressors, are light-duty units designed for intermittent use by the homeowner or handyman
• Direct-driven
  Example: If a homeowner is roofing and he and a helper are both using air-powered roofing tackers drawing 2 cfm each, then a tankless 4 cfm unit is ideal.
• Medium – 6 to 20 cfm are:
• Normally twin or four-cylinder units, depending on rating and efficiency of the piston/valve design
• Electric powered
• Powered by standard 112v, 15-to-20 amps found on most job sites
• Best with gasoline engines for use on remote locations where power hasn’t been connected
• Belt-driven off a pulley of the engine or motor
  Example: If two subcontractors are using framing nailers that draw 3 cfm each, then a 5-hp gasoline engine or 1½-hp electric motor delivering 6 cfm will work.
• Large – 20 cfm and above are:
• Needed for use on portable lifts, on fastener applications and for using multiple ceiling-texture sprayers
• Required to have a rating of at least 80 cfm when powering a jackhammer
• Often diesel-powered, tow-behind compressors with 100 to 800 cfm are needed to run multiple jackhammers, pumps, air tools and other tools at a construction site
• Great for helping contractors when a unit is down, when there are extra subcontractors who need power or when a larger compressor can help them finish a job quicker
  Example: You’ll need a 100-cfm unit for one air hammer, a 200-cfm unit for two, etc.

The 180-cfm compressors account for about half of all compressor rentals.

Whether the unit is direct or belt-driven, uses an electric motor or an engine, relies on an air tank or is tankless, the cfm rating (cubic feet per minute produced at operating pressure, not horsepower or tank capacity) is the most important specification you need to know. These units:

• Can handle two concrete breakers, plus a smaller chipper hammer or rock drill, and are still compact enough to be easily towed
• Are the all-around workhorses of the rental industry
• Are usually diesel driven with engines rated 45 to 60 hp

Your Rental Pro Has the Knowledge

Count on your A.R.A.-affiliated rental professionals for important information about compressor rentals. By listening to their advice before taking the compressor to the job site, you can avoid problems. Here are some tips they’d like to share:

• Horsepower doesn’t make air – the compressor does.
• Tanks don’t make air – the volume is a matter of piston stroke and cylinder bore.
• Tool manufacturers may specify that a tool needs 80 psi and 2.4 cfm. Size the compressors accordingly.
• It’s always better to err somewhat on the side of over capacity. Allowing a bit of wiggle room to compensate for coupling leaks or for a tool with weak O-rings is recommended. A tool with blown O-rings can require up to 2½ times its specified rating in order to function properly.
• Ideally the compressor should run 60/40 – 60 percent off time to 40 percent run time – although compressors made for the contractor, unlike home handyman units, are designed to run continuously, if needed.
• The cycle time – the time needed to produce a full tank of air – should be on the unit. If it takes too long to recycle or is constantly recycling, worn tools or leaks may be the culprits.
• If your air tool requires 4 cfm and your compressor is producing 2 cfm, you’re going to continually wait for it to build tank pressure to reach operating pressure – not a good scenario.
• Air-tool oil, extra air hoses and couplers are add-ons usually available from your A.R.A.-affiliated rental house.
• Before leaving the rental house, your rental pro should tell you that the unit has the proper amount of oil in the sump, and provide instructions on how to check it – usually through a site glass – throughout the day.