Master shut-off on Top Dragster?

I am not sure how to set up my master shut off based on NHRA rules. They say I can only have one shutoff, but I have two electrical systems and the mag that I have to kill, and they say I have to do it on the positive side. When I bought the car it was wired to only kill the mag with the push cable.

My starter system (on board by rule in top dragster) is 48 volt, and is simply a cable going to the solenoid, and from there to the starter. Off of one of the batteries I pull 12 volt for the delay box, tach and so forth. Then there's the mag. Any idea how I kill all of these things with one push cable switch?

-Brian

 

How are you doing the 48volt starter when the rules say a maximum of 2 batteries?
is it legal to plug in an external battery pack?

 

When I first popped the top on the car, I thought I was looking at two normal sized 12v batteries, but when I started taking it apart it became apparent that each "battery" was a pair of 12v batteries hooked together as a pack. I'm going to eliminate one pack and see if it will start on 24v. I'm pretty sure it will, and it will save me about 26lbs. And, no, as I read the rules, you cannot have a start cart.

That being said, I still have the problem mentioned above. There have got to be other dual voltage cars with a mag and a master cutoff. How do they do it?

-Scouder

 

Kill Switch

Flaming River makes a kill switch with one button but two separate internal switches, one for the mag and one for the battery. Go to "flamingriver.com" Switch is part # FR1010 $119, Terminal Covers part# FR1003TM $12.

 

Before the Flaming River switch came out I made one up using 2 switches side be side with the shafts tied together with a bar. Worked the same way.

Seems to me that the rule needs to be refined.
1: IF you do not have an alternator (as would be the case when using a mag)
2: IF you do not have an electric fuel pump
Then there is no need for a switch on the 12 v side......is there?

With a Magneto and a mechanical fuel pump is there anything else that needs shut off to avoid engine run on? Can't think of anything.

Having said that I still give them what they expect to see rather than attempt to explain it on a hot day to a tired tech guy.

Dave Koehler
http://www.koehlerinjection.com

 

I came up with a solution late last night while I should have been sleeping.

The plan to kill all 3 circuits simultaneously using the push cable switch is as follows:

1. Put the cable switch on the 12 v positive side. So it is disconnected when the switch is open.

2. The 48v side is wired direct to the starter solenoid, so it is open anyway (I didn't think of the solenoid as a disconnect switch, but it is). The power to trigger it will come from the downstream side of the cable switch, so if the cable switch is open the solenoid can't close (start).

3. Hook a normally closed relay to the coil terminals so it is grounded when the 12v is switched off. As soon as the cable switch is switched on it energizes the relay, and opens the coil so it can fire the engine. Then the mag kill switch in the drivers compartment will be wired either directly across the coil leads or across the relay leads (whichever is cleaner) so it can be shorted by the driver.

Seems pretty simple, as the only thing I've added to the car is the relay for the coil.

-Scouder

 

I have the Flaming river one no problems since 1998 was priced realisticly also.
Rick

 

Agreed. What is the intent of the rule? If it is to shut down the engine as quickly as possible (and I believe it is), then something to kill the ignition is the best way. I use a switch at the back of the car to operate the main electrical relay (50A). If that is turned off, it will close the mag relay by default.

 

shut off

I wouldn't worry about it. I run in Div 1. Never had one on.mine Tell them when you see one on a TAD you will put it on. yours. lt goes along with the on board batterys. and starter.Bull Shit. When the class grows the way it is. there will be no room for a 7 sec. car anyway.Do whAT YOU NEED TO DO AND KEEP IT TO YOURSELF.only CRY BABY WILL COMPLAIN.don't tell or show anyone. Hell they still need DELAY BOXES TO DRIVE.cause they can't drive with out one.
ANY ANYONE WHO DOESN'T LIKE IT MY NAME IS Don ONIMUS 267-625-0891.

 

I just love the way you think!

-Scouder

 

Yeah, with thinking like that, who needs this tech forum...................

 

The only time we ever got checked we had to start the motor and the tech guy killed it with the switch. We run a mag kill one the same Bat kill. Flameing River. Larry was real P-----sed he doesn't like killing with grounding the mag.

We are NOT a top dragster but I think the issue is the same Kill the Motor.

Delay Box Hell my driver has a built in delay box He delays everytime at the lights. Just jokeing Son hehehehehe.

By the way people Larry [Moparious Maximus] is a new DAD with a girl child. I smell a Jr Dragster in my future mmmmmm can you put a blower on a Briggs?

 

This is my 3 year old. There ain't nothin like little girls helping daddy. She already asked if she can drive the dragster. By the way, she really did pull the valve cover nuts (once I broke 'em loose).

-Scouder

 

Congratulations Dad Larry and grandad Larry, Scouder, she's an absolute doll. Enjoy her everyday, they grow up way too quick and then one day they bring home some hard-ape they are totally in love with that doesn't know jack about racing................don't ask how I know that...........

 

Thanks Ron, I hope she grows up working on race car stuff, and maybe getting in the drivers seat, who knows.

 

I cannot imagine anything making a daddy prouder. It broke my heart the other day to have to explain to her that she couldn't ride WITH me in it.

-Scouder