Just picked up an 86 Olds Station Wagon for the demo derby at the Lake County Fair (IL). Anyways, I have heard of people welding something in the rear end to make both wheels spin, which is critical for demolition derbies. What do I need to weld together? Also, anyone have any other tricks for prepping a car for the demo derby? Thanks in advance on this non-thirdgen topic.

 

Pull the diff cover, weld the spigears together. It'll last a bit longer if you heat the gears to a dull red, and remove the temper then weld, otherwise it's tough to really weld them to last.

Minimize the amount of travel on pavement, to eliminate the welds cracking apart.

 

Yes do what 8Mike9 said, weld the spider gears together really good, just don't get any weld splater on the ring and pinion gears.


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It is stronger to weld the side gears directly to the carrier. You can lay down four heavy welds that way. I used this method on my daily driver Chevy truck. It has a 12 bolt rear with 35 inch BFG's. You'll get tire squeal at every turn, but the extra traction is worth it.

[This message has been edited by N_IROC (edited July 22, 2001).]

 

It's best to weld them with stainless rod. We're not talking about just a little weld. You need to weld it up as much as you can filling in all the spider teeth and welding around the spiders as much as possible. You're trying to make the carrier and spider gears one piece.

I had them done on my old 4x4 years ago by someone else.

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1. Foam in the tires and use steel wheels (not alloys). One of the first things you'll do is run over debris from all the other victims;

2. Keep the AC condenser in place to cushion the radiator. Remove the thermostat, cooling fan, and fan shroud. Replace the long fan/pulley bolts with short ones to keep the pump pulley in place. Keep the heater core as your "radiator" - you'll remove enough heat with the heater/defroster on full to keep running for a long time. Also remove any grille trim since the shattered plastic can penetrate the radiator pretty easily - you don't want to be a victim of your own debris;

3. Move the battery to the interior if you can. Inside a rear seat footwell in a marine battery box is pretty safe;

4. Reinforce the front bumper with whatever steel you can weld/hide in there. A 2" pipe is pretty good, or channel iron would work nicely;

5. Fully roll down or pop out all the glass you can ahead of time. The windshield will not "explode" if distorted or impacted, but all the other glass will. Keep a small prybar in the car so if the windshield does take a hit you can rake it out of the way and make a hole to see through;

6. Remove the transmission oil cooler lines from the radiator and close the loop with a section of hose rated for oil under pressure. If the radiator does take a hit you may lose all the trans oil and be dead in the water;

7. Don't forget to have plenty of fuel in the tank (easy to forget - and if you develop a leak you won't run out as fast);

8. Weld the doors and tailgate shut. The latches and hinges aren't that substantial;

9. Paint the car a dark color - you're a smaller and less obvious target if you are harder to see (besides, my favorite color is black);

10. Cut away any unnecessary exhaust parts that might get hung on debris or collapse on impact. A loud car sounds a little "meaner" too - you can at least intimidate some of them;

11. Use only DRIVE and REVERSE, since manually shifting raises line pressure and can maximize any oil loss from leakage;

12. Keep the spare tire and jack in the car if allowed. It creates a nice cushion, and the jack is a structural member.

13. If it is a full-size wagon (rear wheel drive) cut or disconnect the emergency brake cable. One side impact can lock your rear brakes and leave you helpless;

14. DO NOT fold down the rear passenger seat. You don't need the steel seat back coming through your seat;

15. Stay off the brakes whenever possible. You're better off rolling with the impacts than sitting still and absorbing all the energy with the chassis;

16. Weld the tie rod sleeves to the tie rods - these break easily in side impacts;

17. If you are really serious, foam in all the body panels with insulation foam. You can get some real rigidity with foam in the voids.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Thanks for the replies. What should I use to heat the gears with?

Vader, I have a couple questions/comments about your reply:

2. Why would I want to remove the t-stat and the cooling fan?

4. I wish I could, but it's not allowed.

6. My dad lost races because of the trans cooler lines. Luckily he realized to do exactly what you said.

14. I think I have to remove the back seat anyways.

17. Can't do that one either.

#3,5,10 are already rules that I have to do anyways. Thanks for the long response.

 

Although I've never run in a demo derby there are a few other things you can do to survive longer.

Lower the engine compression. This can be done by putting large chamber smog heads on the engine. Going from a 58cc 305 head to a 76cc 350 head will really bring the compression down. A low compression engine doesn't produce a lot of HP. Less HP means less heat. Less heat means if you lose the rad, the engine will keep running longer. There are demo drivers that have a different car at each event but the engine is the same. They build an engine to survive and after the event, pull it out for the next car.

As for heating the gears, Welding will get better penetration when the metal is hot. If the welding arc doesn't have to heat the metal, it will penetrate deeper into the metal forming a better weld. Heat them up with a welding torch or a rosebud.

 

The cooling fan will find it's way through your radiator unless you remove it. Taking out the fan and replacing the hub/clutch bolts with short ones will give you another 3-4" of "cushion" up front.

Removing the thermostat will cause the engine to run cooler and at a lower cooling system pressure (I.E., longer before overheating). Your heater core and blower will remove all the heat you need. You might want to run with a lower pressure radiator cap or loose cap as well.

Incidentally, you can't get much lower compression than an '86 305 in a 'B' wagon body. I don't think a different set of heads is worth the trouble.

As for your first and original question, don't be amazed if you pull the inspection cover and find a set of clutch cones in the diff - many of the big wagons had a posi axle.

I'm half tempted to come over and watch...

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

BTW - Does Rockenbach have any of the Hummers yet? Maybe you could take one for a "test drive" on the night of the race.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

oh about foam in the tires- use that expanding foam crap they sell for insulation and put a nozzle from a fix-a-flat can on it, i bet that will work really good.

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Vader, I haven't seen the Hummers there yet I don't think. I'm usually too busy looking at the Z06's.

Anyways, will the welds in the rearend eventually break in the race if I do weld the spider gears? Any other tricks you guys can think of? Money isn't really an issue, because my dad's work is sponsoring my car.

Thanks for the replies.