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NEDRA Rulebook

The NHRA has incorporated electrics into their rulebook.  Therefore, NEDRA no longer has a separate rulebook.  Below is an explanation of the NHRA rules specifically as they apply to electric vehicles. If you have any questions about any of the technical rules please contact our technical representative at tech@nedra.com.



"NHRA Rules Explained" Index

0.1 Introduction
0.2 Overview
0.3 Designation
1 Motor and Fuel System
1.1 Motor
1.2 Fuel System
2 Drivetrain
2.1 Clutch, Flywheel, Flywheel Shield
2.2 Driveline
2.3 Rearend
3 Brakes and Suspension
3.1 Suspension, stock-bodied vehicles
4 Frame
4.1 Deflector Plate Open-bodied vehicles
4.2 Wheelbase
8 Electrical
8.1 Batteries
8.2 Fusing of Batteries
8.3 Recharging
8.4 Ignition
8.5 Master Cutoff
8.6 Wiring
9 Electric Powered Motorcycle Designation
9.1 Motor
9.2 Batteries
9.3 Master Cutoff
Glossary



0.1 Introduction
The NHRA rules for electric drag racing are a condensed version of the original NEDRA rules. Our goal here is to more fully explain these rules so that competitors can more easily comply with the rules and National Hot Rod Association (NHRA) inspectors can be sure that competitors are complying with both the letter and the intent of the rules.

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0.2 Overview
The rules in the electric vehicle section of the NHRA Rulebook (quoted below) are specific to electric vehicle drag racing. They are not the only rules that apply to EVs in drag racing. The NHRA General Rules and the NHRA ET Handicap Racing rules must be adhered to as well. Thus, you need to obtain a current NHRA Rulebook from your local track or parts store to have a complete set of rules.

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.3 Electric Powered Vehicle Designation(7.50 (*4.50) seconds &slower)Requirements and specifications for electric powered vehicles are the same as E.T. Bracket Vehicles - Section 1A - with the following exceptions.

Electric vehicles must meet the all the requirements in the rest of the NHRA rulebook, specifically in the E.T. Bracket section and the General Rules section.  

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1 Motor and Fuel System

1.1 Motor Electric Motor(s) only permitted”

You can use more than one electric motor to power your electric drag vehicle (EDV.) Conversely, the internal combustion engine (ICE) competitors are restricted to using a single ICE. This rule also prevents a competitor from using a combination of an electric drive other types of engines such as ICEs.

    Maximum height of electric motor output shaft centerline 36-inches on OEM trucks; all others 24-inches.”

A motor weighs quite a bit. If you mount it too high in the vehicle, it makes the center of gravity (c.g.) too high and can make the vehicle unstable. In the past, ICE competitors raised their engines to raise the c.g. to help transfer weight onto the rear tires during the launch. Some folks did not exhibit common sense in the extent that they raised the engines, so a maximum limit was imposed. This rule is to remind the EDV competitors that they are subject to this height limit as well.

    "Exposed-motor electric-powered vehicles with open frame, vented, or brush replacement window motors must install a motor shield, minimum 0.024-inch steel or 0.032-inch aluminum, or 0.120-inch Lexan.

A non-conductive shield made of minimum 0.120" clear Lexan is preferred by NEDRA and allowed by the NHRA. (See more about this shield below.)  

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1.2 Fuel System

    "All conversion vehicles must remove fuel tanks and fuel system, including vapor storage equipment, from vehicle.”

If you are building an EDV, you have to remove ALL of the fuel system. This also means that you can't have a fuel-powered heater or auxiliary power unit (APU) on your EDV that you built yourself (conversion.) Hybrids and other OEM EVs are allowed to have fuel tanks, etc. (To set an official NEDRA record, nothing other than batteries is allowed to power the vehicle.)  

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2 Drivetrain

2.1 Clutch, Flywheel, Flywheel Shield

    "Flywheel and clutch meeting SFI Spec 1.1 or 1.2 (2-disk maximum) mandatory on any car running 11.99 or quicker. Flywheel shield meeting SFI Spec 6.1, 6.2, or 6.3 mandatory on all cars running 11.99 (*7.49) or quicker.”

If your EDV has a flywheel or clutch, and you are running 11.99 or quicker, (7.49 in the 1/8) you caned use an ordinary flywheel or clutch. You must use a flywheel and/or clutch specially built for racing. You also have to have a specially designed bell housing shield to contain an exploding flywheel.  In ICE drag cars, flywheels explode on a fairly regular basis. The shrapnel causes a lot of injury. The NHRA wants to remind the EDV competitors that they must adhere to all the rules regarding flywheels and clutches.  

Exposed-motor electric-powered vehicles with open frame, vented, or brush replacement window motors must install a motor shield, minimum 0.024-inch steel or 0.032-inch aluminum, 360 degrees to provide protection from flying commutator bars, molten copper, plasma, etc. in the event of a motor overload.”

When you overload or over-rev a DC electric motor, all sorts of nasty stuff comes flying out of the commutator area. A shield is needed to keep this from hitting the driver. Note that this shield is only required for –exposed-motor” vehicles. If the motor is under the hood in the engine compartment of a full bodied car and there is sheet metal between the driver and the motor, there is no requirement for additional shielding. (However, there is no harm in having this shielding, regardless.)

    "A motor plate, minimum .125-inch steel or 1˜2-inch aluminum, may be used to adapt the motor to conventional transmission.”

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2.2 Driveline

    "Driveline loop mandatory on any non-OEM vehicle running 16.00 seconds or quicker. See general regulations 2:4, 2:11.”

A driveline loop is installed close to the front of the driveshaft on a rear wheel drive EDV. If the universal joint should break, the loop constrains the driveshaft and keeps it from digging into the pavement (and flipping the car) or tearing through the floorboards and injuring the driver. Note that the requirement for a loop is at a substantially slower ET for an EDV than for ICE cars. This is because EDVs typically weigh more and typically produce much more torque than do ICE cars.  

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2.3 Rearend

    Chain drive vehicles must be equipped with a chain guard constructed with minimum 0.125-inch steel or 0.250-inch aluminum, covering width and top run of chain to centerline of sprockets.”

You'll notice that the thickness is twice that required in the motorcycle rules. This makes sense since the torque and HP of a typical four-wheeled EV is much greater than that of a motorcycle.

This rule has been recently changed by the NHRA. A full chain case was required in the 1998 and 1999 NHRA EV rules. (I believe this originated from the EVTC rules.) There is nothing about EDVs that would require special rules for chain drive systems. The standard NHRA rules for chain guards apply to EDVs. The standard NHRA type chain guard protects the driver and allows the broken chain to drop onto the track, minimizing the risk of a jam-up that would lock the rear tire(s.)  

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3 Brakes and Suspension 

3.1 Suspension, stock bodied vehicles

    OEM three-wheeled vehicles permitted.”

Electric three-wheeled vehicles are allowed. Conversely, ICE three-wheeled vehicles are NOT allowed.  

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4 Frame

4.1 Deflector Plate Open-bodied vehicles

    ”Each vehicle must have protection for driver from traction motor overload. Must protect driver from motor plasma, flying commutator bars, molten copper, bursting batteries, and spraying electrolyte.”

In an open-bodied vehicle, you must have a shield between the driver and the battery pack(s) to protect the driver from the debris and plasma from bursting batteries. Open-bodied cars MUST have the commutator  shield (described in the driveline section above) regardless of whether the motor is enclosed by the body or not. A sheet of 1/8-inch Lexan is the preferred shield, but other materials can be used.  

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4.2 Wheelbase

    Minimum 90-inches, unless the car has original motor or is a conversion electric powered vehicle with motor in original (internal combustion) position.”

Lightweight short vehicles with two rear wheels are very difficult to control on the drag strip. Under hard acceleration, if one rear wheel loses traction, the force from the other wheel can abruptly spin the car if the wheelbase is too short. OEM cars are heavy enough (and typically slow enough) where this problem is not severe. Thus, conversions and OEM EVs with the motor left in the original position can have a wheelbase shorter than 90-inches.  

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8.0 Electrical

8.1 Batteries

    Must be securely mounted and outside driver compartment.”

Batteries must be isolated from the drivers compartment. That is, battery packs physically inside the drivers compartment must be fully enclosed in boxes. Batteries that are fully enclosed by boxes are considered –outside” the drivers compartment.

    Batteries must be installed so as to withstand a force 4 times (vertical) and 8 times (horizontal) the weight of the battery pack and each battery or battery pack must be secured with bolts and straps commensurate with the size and weight of the battery. (Contact NHRA for requirements).”

The batteries must stay with the vehicle in a collision or roll-over. Its almost expected that the support structure will deform, but the batteries must not fly loose. The mounts and supports for each battery and each battery pack must be strong enough to withstand 8 times the weight of the batteries in the horizontal plane (front direction, back direction, and side directions) and must withstand 4 times the battery weight in the vertical axis (up and down directions.

The rules are structured to give complete specifications for two common methods of mounting batteries and then allow alternate methods by design submission and prior approval.

If you are mounting the batteries on a flat plate, use Table 1 to pick the bolt size for the weight of the battery and then use Table 3 to pick the strap size. If you are mounting the batteries in a box or rack, use Table 2 to pick the bolt size for the weight of the battery and then use Table 3 to pick the strap size. If you have some other design that isn't a flat plate or a rack with the batteries held in with bolts, you must submit your design in advance to the sanctioning body and they determine if it meets or exceeds the basic criteria.

All this makes it easy for the racers to make a battery hold down system that works and it makes it easy for the tech inspector to determine if each hold down system meets the NHRA rules.

For example, let's pick out bolts and a strap for a 45 pound battery, mounted on a flat surface. The minimum bolt sizes from Table 1 would be: 7/16" Grade 1, 5/16" Grade 5, or 1/4" Grade 8. I have a box of 1/4" Grade 8 bolts, so I'll select them. Next, I look at the strap table. Table 3 says that I should use 0.084" steel or 0.139" aluminum. I have some 1/8" (0.125") steel on hand, so I'll pick that. From the same line on the table, the cross section must be 0.120 square inches. I divide the cross section by the thickness to get the width of the strap. Thus, the minimum width = 0.120 / 0.125 = 0.96".

On a flat surface, each battery must have a bolt on either side. Bolts can be shared with an adjacent battery, however. Thus, you could mount three 45 pound batteries side-by-side with 1/4" grade 8 bolts between each battery with one bolt at each end for a total of 4 bolts.

You can use several small bolts in place of one large bolt.  In a box or rack, if the bolts are captive, you can use washers in place of straps. In a box or rack, when using straps (or a cover plate) you must have end (edge) bolts, but you need not have a bolt on each side of each battery. However, the bolts must be sized for the weight of the batteries that each bolt is securing.  

    Battery may not be located above the top of the rear or drive tires in open wheeled cars, nor outside the body lines in bodied car, except OEM production line electric powered vehicles.”

Just like the restrictions on raising the motor, this rule is in place to keep the c.g. within sane limits and the batteries mounted in a safe and sensible location.

    Batteries must be completely sealed from driver compartment.”

The batteries must be separated from the driver by some sort of barrier. The firewall of an ordinary car is considered –sealed” even though it has a quite few penetrations through it. Thus, there may be a few penetrations or small openings in your battery box, much like a firewall. Although not stated specifically in the NHRA rules, it is a wise practice to provide a vent from the battery box to the outside of the vehicle.

    All open bodied vehicles must use absorbed glass mat or starved electrolyte batteries for power source.

Absorbed glass mat (AGM) and starved electrolyte batteries are the high performance sealed type batteries. There is no –free” liquid to splash out in the event of a collision or burst battery.

    Traction motor and/or any high current wiring may not be located in drivers compartment”.

In the event of a short circuit, the traction wiring will sometimes light up like a fuse. Its important to keep the smoke and plasma away from the driver. If it is impractical to route the high-current wiring outside the drivers compartment (like in a dragster) it must be routed through a duct or conduit that will contain the smoke and plasma that would result from a short circuit. Thus, it will be –sealed” from the drivers compartment, just like the batteries.

    Instrumentation wiring permitted.”

You can run a high-voltage wiring to your instruments inside the drivers compartment. High current wiring is not permitted, however. The amount of high voltage wiring inside the drivers compartment should be kept to a minimum.

    All traction motor wiring must be isolated from the chassis.”

All traction wiring, including all of the motor and battery wiring, must be isolated from the chassis of the car. This is a very important safety practice. Unlike typical 12 volt car wiring, the high voltage wiring in an EV is completely isolated from the chassis of the car. This practice greatly reduces the risk of a shock and greatly reduces the risk of a fire.

When the traction wiring comes in electrical contact with the chassis, it is called a –ground fault.” It takes two, separate, ground faults to produce a complete short circuit. If the car has no ground faults, a person may inadvertently touch the high voltage wiring, yet not get a shock even though they are touching the car chassis as well.  It is important to check for ground faults on your EDV before every race.

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8.2 Fusing of Batteries

    All battery packs must have over current protection. Circuit breaker(s) or fuse(s) permitted. Such protection devices must have a DC voltage rating equal or greater to the nominal pack voltage.”

There must be a fuse or breaker associated with each distinctly-separate battery pack in the EDV. The DC voltage rating must be greater than or equal to the TOTAL nominal pack voltage. For example, if the vehicle has a 240 volt drive system, it must have 240 VDC (or greater) rated protection devices. An AC voltage rating will NOT do. Fuses and breakers may be paralleled.

A device designed for AC typically will not "clear" a DC voltage much over 28 VDC. The fuse blows, but a stout arc remains to continue to carry current and start a fire.

    Current rating must be lower than a short circuit current that pack can produce without damage.”

The 2001 NEDRA rules require that not only must the pack be protected from over-current, the main (safety) disconnect must also be protected from overcurrent damage. The same protection device (fuse or breaker) can serve both functions. The continuous current rating of the protection device must less than or equal to the continuous current rating of the main (safety) disconnect.

It is important to note that not only the continuous carry current of the fuse should be less than the rating of the contactor, but the carry current curve of the fuse should lie completely below the carry current curve of the contactor. 

    ”Battery sub-packs must be individually fused.” 

Often, all the batteries are not in the same location or battery box. If there are distinctly separate battery boxes (packs) that are connected by cables, each separate pack must have a fuse (or breaker.) The fuse (or breaker) must be rated for the vehicle voltage, not just the separate pack voltage.

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8.3 Recharging

    ”Batteries may be recharged in the pits or other designated areas only.”

You may not charge your EVD in places other than where the track officials tell you it is permitted. Pretty straight forward, but they have to spell it out for some folks.

    ”All vehicles must be connected to AC power supply (earth) ground when charging.”

It is rare that you get access to a plug-in at the track. If you do, you must connect the frame of your EVD to the ground wire of the supply. If you are charging from a generator, you should connect the frame of your EVD to the ground wire of the generator.

    ”All battery chargers must be equipped with an output fuse rated for 600 volts and a current capacity at least 125% of the maximum charger DC output.”

This is another holdover from the EVTC. It's easy enough to comply with and no one complains, so no one has bothered to go though the effort to change it.

In addition to this "regulatory fuse" you should have a charger output fuse (or breaker) that is rated for at least the maximum DC voltage output of the charger (if it is on the DC side of the rectifier.)  This fuse must protect the charger, the vehicle wiring, the charge connector, and the charger output conductors. Thus, the fuse current rating is set by the weakest of these components. If the charger is rated at 20 amps, but the charging cord is rated at 15 amps, the fuse rating can be, at most, 15 amps.

It's wise to have more than one fuse (breaker) in the circuit. One fuse should be located in the charger, the other in the vehicle, (where the charging wiring ties into the traction wiring.) The vehicle charging fuse should be sized to protect the portion of the charger wiring that stays with the vehicle.

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8.4 Ignition

    "All vehicles must have a visible indication of a 'live' car, except OEM."

One of the biggest, and most overlooked, hazards in electric drag racing is a driverless launch. When you "start" an EV, it makes no noise. Thus, without some obvious visible warning, it appears to be "safe" even though it is not. Just like an ICE vehicle at the track, you may not "start" an EV without a driver in the driver's seat.

    "An externally activated switch or switch control must be installed on the outside of the vehicle and clearly marked to indicate OFF position."

See "Master Switch" below. There must be some convenient way to operate the main disconnect from inside the vehicle too. It can be a separate switch, if desired.

    "A RED triangle must be clearly visible the power system is turned on. This may be a light or a mechanical indicator."

An easy way to comply with this rule is to put a red triangle on your key ring. Don't leave the keys in the ignition when the driver is not in the car.

It's smart to put an indicator light on the dash that is powered by the controller input connections. If the main (safety) contactor malfunctions, the light will show the problem. Your life may depend on the main contactor, so it is smart to have the indicator to double check proper operation.

    "Traction battery pack must be physically disconnected when switch is in the off position."

There must be mechanical contacts that open up. You can't use a semiconductor 'switch' to serve this purpose. An electrically-operated contactor can be used as well as a mechanically-operated contactor. Some folks use a large connector for this purpose.

It's important to note that this main "safety" contactor may NOT routinely open or close under load. That is, it must be separate from any contactor used to throttle the vehicle, or pre-charge the controller

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8.5 Master Cutoff

    "All vehicles except OEM must incorporate a master electrical disconnect switch that must disable all electrical functions. Switch must disconnect traction motor battery pack section of circuit, and if switch is push-pull design, push must be 'off' function."

This sounds like there are a lot of high-current disconnect switches involved, but there need not be. Often, there is one main 'safety' contactor in the battery pack circuit that is operated from more than one location. Conversely, you may opt for several separate large-current disconnects to fulfill the requirements.

NEDRA and the NHRA strongly recommend that the master disconnect switch be located on the rear of the car. The NHRA requires that the master switch be located on the rear of ICE vehicles.

The simplest way for a daily driver EV to comply with this requirement is to mount a stout toggle switch on a sheet metal plate, wire it in series with the main ('safety') contactor coil, and shut the trunk lid on the plate. (Toss it in the trunk as you leave the track.)

Although there is no requirement in the rules, it is very smart to have a way to easily disconnect both the positive and negative leads of the battery pack. Most folks use a big Andersen connector for this. When the plug is out, you know that every high-voltage wire in the car is de-energized. This makes any work on the car much safer.

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8.6 Wiring 

    "All high-voltage wiring must be located and secured to prevent contact by driver and/or spectators. Any wiring over 24 volts must be completely covered."

When the hood is closed, and the car is race-ready, there must be no way for someone to touch a live, bare, conductor or terminal on the traction circuit (over 24 volts.) You can have exposed high-voltage under the hood or under service covers. You or one of your crew must be present when there is exposed high voltage. This is to keep curious spectators from injuring themselves. Ordinary folks don't comprehend that "car wiring" can be deadly, so you really have to be vigilant in the pits.

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9 Electric Powered Motorcycle Designation  (7.50 (*4.50) seconds & slower)

    "Requirements and specifications for electric powered motorcycles are the same as E.T. Bracket Motorcycles - Section 1C - and Electric Powered Vehicles - Section 1F - with the following exceptions.  

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9.1 Motor

    "Electric motor(s) only permitted."

This rule is to prevent the ICE racers from somehow using the EV rules instead of there own rules. Also, note that you can use more than one motor if you care to.

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9.2 Batteries 

    "Wet, (free liquid) battery prohibited."

  You can't use flooded batteries on an EV motorcycle. If the battery has liquid inside that sloshes around, you can't use it.

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9.3 Master Cutoff 

    "All electric motorcycles must be equipped with a switch, attached to the rider with a lanyard, capable of shutting off all power to electric traction motor."

This is much like the "master cutoff" required in Section 1F above, but it shuts down the main contactor (or breaks the traction battery circuit) when you part ways with the bike. The main ("safety") disconnect must be physical contacts, just like in Section 1F.

NEDRA has added a new rule for 2001. On a motorcycle, the driver must be able to actuate the master cutoff with both hands on the handlebars and both feet on the pegs.  

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Glossary

APU Auxiliary power unit. This is a fueled electric generator used to power an EV on long trips.

c.g. Center of gravity. The balance point of a vehicle.

Conversion An electric vehicle that was not mass produced. That is, an EV that you built yourself.

E.T. Elapsed time. The time it takes a vehicle to travel the 1˜4-mile distance.

EVD Electric drag vehicle. A drag racing vehicle powered by electricity.

Ground Fault An electrical connection from the traction wiring to the chassis of the vehicle. This is a dangerous condition.

ICE  Internal combustion engine. Typical gasoline engine found in most cars.

NHRA National Hot Rod Association. Largest sanctioning body for the sport of drag racing.

OEM Original equipment manufacturer. An OEM car is one that is mass produced.

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