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Old 09-29-2014, 11:01 PM   #1
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Default One Ways, again

Talking to one of the better drivers at my track about his Capricorn 1/8 electric (foam tires) I asked how does the front one way - rear spool combo works. He was of the opinion that around corners the oneway drives the outside wheel given that the inside wheel does not have enough weight on it to grip.

Theory would have you believe that given the virtually non existent roll of the 1/8 cars, the front inside wheel would not lose traction ever, hence the one way would drive the inside wheel whilst the outside one is freewheeling (spinning faster as it goes around the corner on the longest arc).

Anyone with experience can confirm that there is enough roll in these cars to shift drive to the outside?

Also, the rear spool is an enigma to me, I would imagine the rear would want to step out no end especially given the front one way drive that hooks around corners incredibly tight.

That said, his car is amazingly fast with no obvious oversteer issues (of course, I can not ascertain the amount of skill/effort it takes to drive the car, but he makes it look really easy).
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Old 09-29-2014, 11:16 PM   #2
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One ways were quite popular back the day when i started racing. When using one ways, the vehicles corner harder off throttle(front wheels are allowed to spin at different rates). But if you needed to panic stop and used the brakes, most likely the car will spin out(only rear wheels brake) making braking almost impossible. But since most of the big races today mandate four wheel braking, thus the extinction of the front one way.
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Old 09-30-2014, 12:49 AM   #3
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8th on foam have massive amounts of grip and huge amounts of power. The spool/one-way combo works because its more important to have a car that is positive on power than a car that makes the most of its tyres. 8th cars are very point and squirt when you see them driven, none of the tidy flow of an electric rubber car.
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Old 09-30-2014, 01:22 AM   #4
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I am not sure I understand what you mean by "positive on power" sosidge.

How does that relate to the one-way front dilemma I mentioned above?

And about the rear spool, are you saying the huge foam tires have so much grip the car can't spin out?

You are right about the "point and squirt" thing.
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Old 09-30-2014, 02:06 AM   #5
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You need the one-way to make the car steer. The one way lets you pivot the car fast off-power or even "handbrake" the car into the turns. A diff or solid axle is much slower to respond. On power the one way acts like a spool as well so you get maximum stability under traction.
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Old 09-30-2014, 03:44 AM   #6
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Quote:
Originally Posted by sosidge View Post
You need the one-way to make the car steer. The one way lets you pivot the car fast off-power or even "handbrake" the car into the turns. A diff or solid axle is much slower to respond. On power the one way acts like a spool as well so you get maximum stability under traction.
Yes and no. The one way on traction acts as a spool if both tires are loaded. If one is unloaded, the other one pulls which is different from spools because with a one way the one wheel that pulls can be outside or inside the corner.

If it's the outside wheel, you have the rear trying to follow the same length of track or longer as the front (possibility here for the rear end to step out).

If it is the inside front wheel doing the pulling, you have the rear end trying to follow a trajectory which is going to be the same or shorter than that of the front (good).

This difference is what bothers me and I don't understand how it's dealt with by this setup. My friend at the track argued that situation 1 never happens.
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Old 09-30-2014, 04:05 AM   #7
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Quote:
Originally Posted by niznai View Post
Yes and no. The one way on traction acts as a spool if both tires are loaded. If one is unloaded, the other one pulls which is different from spools because with a one way the one wheel that pulls can be outside or inside the corner.

If it's the outside wheel, you have the rear trying to follow the same length of track or longer as the front (possibility here for the rear end to step out).

If it is the inside front wheel doing the pulling, you have the rear end trying to follow a trajectory which is going to be the same or shorter than that of the front (good).

This difference is what bothers me and I don't understand how it's dealt with by this setup. My friend at the track argued that situation 1 never happens.
Since you are already an expert in the field I am surprised you felt the need to ask the question.
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Old 09-30-2014, 04:17 AM   #8
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Quote:
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Since you are already an expert in the field I am surprised you felt the need to ask the question.

Don't be offended. I am trying to understand because it seems the theory does not satisfactorily explain the experiment. That is why I sought the racers who have experience with these beasts.

I am so confounded by this, I am looking on the web where I can buy a Capricorn to study.
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Old 09-30-2014, 06:18 AM   #9
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Quote:
Originally Posted by niznai View Post
Theory would have you believe that given the virtually non existent roll of the 1/8 cars, the front inside wheel would not lose traction ever, hence the one way would drive the inside wheel whilst the outside one is freewheeling (spinning faster as it goes around the corner on the longest arc).

Anyone with experience can confirm that there is enough roll in these cars to shift drive to the outside?
Roll (chassis lean) is different from weight transfer. A chassis with infinitely stiff springs (giving little roll) still transfers weight from the inside to the outside tires during cornering. Weight transfer is only a function of the width of the car, height of the center of gravity, and lateral acceleration. Springs and sway bars let us change the proportion of the weight transfer resisted by the front tires or rear tires, but not the total amount of weight transfer.
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Old 09-30-2014, 06:30 AM   #10
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True, my question is poorly constructed.

So is there enough weight transfer in one of these cars to effectively allow the front outside wheel to drive around corners?
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Old 09-30-2014, 06:35 AM   #11
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So is there enough weight transfer in one of these cars to effectively allow the front outside wheel to drive around corners?
Definitely.
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Old 09-30-2014, 06:44 AM   #12
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So how do they keep the rear end in line? Is it that grippy on the rear that it can't break loose? Or is it (driving one of these cars) a (heck of a) lot harder than it looks?
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Old 09-30-2014, 07:15 AM   #13
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Quote:
Originally Posted by niznai View Post
Yes and no. The one way on traction acts as a spool if both tires are loaded. If one is unloaded, the other one pulls which is different from spools because with a one way the one wheel that pulls can be outside or inside the corner.
I think you are confusing a one way with an open diff. A one way on power is really no different from a spool. Both tires are being driven the same amount. Yes the inside tire could lift and break traction but the outside tire is still being driven the same amount, nothing changes.
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Old 09-30-2014, 07:19 AM   #14
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As for weight transfer, try to find some good slow motion vids of 1/8th racing. They often lift the inside REAR wheel on entry (which helps turn the things with that spool and massive rear tires) and in high bite, bicycling is not uncommon. The Nats in Connecticut several years back pretty much all the A main guys were going through the corner leading on to the back straight on two wheels.
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Old 09-30-2014, 07:22 AM   #15
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Quote:
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I think you are confusing a one way with an open diff. A one way on power is really no different from a spool. Both tires are being driven the same amount. Yes the inside tire could lift and break traction but the outside tire is still being driven the same amount, nothing changes.
An open diff would completely lose traction in the condition you describe through the unloaded wheel (diff out).
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