RR and COM question?

[Aron]

Well it's that time of year again. I haven't posted for a while. Last year my son and I did the Batman car with the LED lights in it. (pics in picture forum)This year we though we would try working a little more on speed. So I thought I would come here and ask the opinion of the experts I am using a Derby worx pro rail rider tool and I have a couple questions to get some of your opinions. As you likely know this tool bends the rear wheels at 2.5 and the fronts at 1.5. In the instructions for tuning the car it says the car should have only 1 inch of drift after rolling 5 to 6 feet on a flat surface. After reading some of the other posts on here some of you suggest the car should turn more than that. Any suggestions? Oh it also talks about notching the body1/16 to prevent the rear wheel from rubbing the guide strip. I presume they mean notching the non domminate side rear wheel?

Also any thoughts on a COM with a standard wheel base can(using factory slots) 7/8 in front of rear axle has been sugested in some of the other posts.

[Stan Pope]

I presume they mean notching the non domminate side rear wheel?

Let's think this through ... RR alignment steers the dominant front wheel toward the rail, dragging the wheel behind it toward the rail, too. (Will the rear wheel reach the rail? Hope not!) Meanwhile the wheels on the opposite side get pushed away from the rail ... so they're okay.

Also any thoughts on a COM with a standard wheel base can(using factory slots) 7/8 in front of rear axle has been sugested in some of the other posts.

7/8" is safe. You can shorten it if you do the rest of the car well ... and the better you do the parts, the closer you can pull that CM back!

[Aron]

Ok now I'm confused more. This sheet says if the right front wheel is dominant the car should drift to the left

[Aron]

Oh I think I got it now if I notch in the front dominant wheel it keeps the rear wheel from rubbing the guide strip

[Stan Pope]

Oh I think I got it now if I notch in the front dominant wheel it keeps the rear wheel from rubbing the guide strip

[rpcarpe]

That's Right. Test it on a roll board or a track section. Make sure your rear wheel behind the DFW doesn't rub the center guide.

[tgrimstead]

I have my kids cut the car out the normal 1 3/4 inches wide. Then glue a section of Popsicle stick on the sides of the rear where we drill the axle holes. This keeps the wheel from touching both the guide rail and body if the wheel drifts off the axle head. Easier for the kids to get right.

[rpcarpe]

I like the extra wood idea! I've shaved off the 1/16, but I might try this popsicle stick idea on a car this year.

On the other hand, if the axles are canted properly, the wheel should never touch the wheel body. Right?

[Aron]

I like the popsicle stick idea too! I wonder if some pack rules would be against doing this?

[Rukkian]

The extra wood sounds good, however, it may pose problems with drilling if you use the pro body tool.

[tgrimstead]

You can use the body tool first. Then drill a hole with the #44 bit through the pop stick. Apply some glue to the back and use a old nail to line up the hole. Clamp, and let dry. A far as rules, some question came from a father ( who's daughter lost.) as if it was a washer. It was deemed by judges after check in, since it was wood permanently affixed to the body that it was merely an extension of the body. I asked the dad " You really think that the Popsicle stick made the car faster? Really?" Of course he claimed we had solid axles . People can be hilarious!

Yes, if your axle is correctly canted it shouldn't be an issue. This was more precautionary, in case it hit a bump or something wacked it out of alignment. Then hopefully the wheel would only rub the body, not the rail too.

[quadad]

7/8" is safe. You can shorten it if you do the rest of the car well ... and the better you do the parts, the closer you can pull that CM back!

Just adding ... flavor your aggressiveness with knowledge of the track(s) you will be riding on. The smoother the track and joints, the more aggressive weight placement - but I wouldn't suggest less than 3/4" unless you have really good alignment, parts and a similar-to test track. This also plays into how much drift you would want to use. Typically more drift as the track gets rougher and similarly the more aggressive COM, the more drift may be necessary to keep it stable. This is where a "Test and Tune" night could be a big help.

[tgrimstead]

3/4 is aggressive. Call me vanilla, but I like to play it safe at about 1 to 1 1/4 inch.

[sporty]

7/8th is a safe and good place to be. I run less than that, but not much less. for a standard wheel base car.

But 1 inch is super safe.

It depends what you want to do. Go super fast, Go fast or just run good.

I run 5/8th to 6/8ths on a standard wheel base. With a drift of 3 1/4 to 3 1/2.

1 and 1 1/4 is what I woudl call the starting point when new into this sport I would call it level 1

Level 2 would be 7/8ths.


Level 3 would be 6/8ths.

Level 4 would be 5/8ths.


Level 3 and 4 I would only recommend with having good building and tuning ability.

Sporty

[rpcarpe]

1/2 inch is near insanity! I couldn't keep the prototype car on the track. Good thing it was just a test car.