Front end geometry

[bdsharp]

Over in the Oval Forum I had asked about the benefits of independent front wheels and the general opinion was that there wasn't much, because with the "tripod effect" of a properly set guide, there should be very little weight on the front tires anyway. But I've seen some chassis where the guide is on a drop arm such that only the weight of the arm is on the guide, and the full weight of the front of the car is on the front wheels. I can see a drop arm would be good for drag racing, but is it generally seen on oval/road course cars? I don't know a lot about slot car chassis theory; what's supposed to move and what's supposed to be rigid, where the weight goes, etc. What's the dope?

[Smokeio]

Front end setup depends on how much grip you have at the rear tires. The principal idea here is what you want the rear inside tire to do in a corner and you are using the front tires to help you. If your track has a lot of bite like at a commercial track with glue, most people find a tripod setup works best. In a turn the rear inside tire unloads and just the outside tire does the work. As the grip decreases, most times the best setup is where the front tires ride on the track and support the weight of the car. This helps keep the rear inside tire loaded and provide some form of grip in a turn.

[waaytoomuchintothis]

I would only add that independent fronts pair best with unequal grip on the rear. For our oval enduro years ago, we used an independent front end and a grippy tire on the left (inside) side, and a slightly less grippy tire on the outside. This allowed the outside rear to slip a little bit, while the inside tire kept it pressed down on the deck in turns. This made for much faster turns and did not affect the straights at all. For last year's Showme Showdown (which I didn't finish before the race), I did an independent front end with a massive camber and the mismatched tires on the rear, and although difficult to do in a small space it was gratifying to see how it ran. A word of caution about this-- Independent front ends are fragile, and they may bend out of alignment in a hard crash.

[strangebrew]

I've got independent fronts on the ASA car I'm building, but I've got some odd rear wheel geometry.
I have been building some of my cars with a drop guide, because I think it stays slotted better
if there's contact or if you climb wheels with your "neighbor".
Also one of my last year's Showdown entries would pull the front wheels on the straights & tend to de-slot.

[bill from nh]

The strength of independent fronts will depend on how they are constructed. They can be built just as strong as a solid axle front end. It was commonplace to use drop arms on road course cars prior to about 1972. When set up properly, they still work. :) I think building a drop arm chassis is more work than building a tripod car.

[waaytoomuchintothis]

That's true enough. I remember chassis with a weighted drop arm, as well as sprung.

Unlike the drop arms, independent fronts in 1/32 are different from 1/24. There's just so little room in 1/32nd front ends. I've done it in brass and steel, and they can get knocked out of whack very easily. Of course, they still work, but the alignment can drive you crazy, rebending after a hard hit with only moments to get it right.

[slothead]

I'm not sure exactly what you mean by independent front wheels - free spinning or they can move up/down independently?

Years ago I built oval chassis with free spinning front wheels that were not fixed in place on the chassis - they floated with the body on hinged body mounts. The body was isolated from the chassis and the chassis itself was one long drop arm weighted down by the motor.

Slothead

[waaytoomuchintothis]

Its just independent spinning. Very big in HO racers.

[bdsharp]

[strangebrew]

[slothead]

That car with the independent floating front wheels was amazing - raced it at a club track and easily won the championship. We raced all custom-built replicas of dirt modified cars, even the bodies were made from brass and tin. It had an extreme offset weight bias to the inside and was absolutely glued to the track. I'm not the greatest driver, but was able to run an entire 100 or 200 lap feature without a de-slot.

I still have the entire car sitting on a bedroom bookshelf, even though the rear foam tires are crumbly and the front tires have split. It reminds me of the golden days of slot car racing when a bunch of us would race weekly at both a commercial track and at a club track. Good times.

Slothead

[RichD]

If you coat your front tires they will have no grip to speak of, so it doesn't matter much if the wheels rotate independently or not. That being said most of my cars have indepandent front ends. I use a hollow front axle and aftermarket wheels with set screws. I push an eyelet into one end of the axle to act as a retainer, a wheel without the set screw goes on that end and one with the set screw goes on the other end. The wheel with the set screw will turn with the axle, the one without a set screw can turn independently.

[smithspeedway]

On solid axle cars, we use collars on one wheel. 1/8" collars fit inside most front wheels. It does make it difficult to use an insert. Look carefully at the front wheel. The collar fits inside a Parma 3/4" front.



Steve