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Old 09-30-2014, 07:31 AM   #16
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Originally Posted by niznai View Post
An open diff would completely lose traction in the condition you describe through the unloaded wheel (diff out).
Yes I know but we are talking about one ways and again, on power they are just like a spool. Off power it's just like 2wd.
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Old 09-30-2014, 08:09 AM   #17
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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.
Situation 1 never happens. A 1-way will always apply power on the slower wheel first (until the other wheel matches its speed - which then makes it practically a spool).
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Old 09-30-2014, 08:17 AM   #18
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Front one way and rear spool is what alot of drift cars run. I would think you would have an extremely loose car with snappy turn in.
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Old 09-30-2014, 08:22 AM   #19
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Yes I know but we are talking about one ways and again, on power they are just like a spool. Off power it's just like 2wd.
How is that going to be like a spool if one wheel drives around a longer arc than the other?!
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Old 09-30-2014, 08:23 AM   #20
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Front one way and rear spool is what alot of drift cars run. I would think you would have an extremely loose car with snappy turn in.
Drift cars don't have those MASSIVE, soft, sticky foam tires out the back.

To understand a 1/8th you have to understand what it is designed to do. 1/8th has a huge power to weight ratio so the single most important design factor is forward bite for maximum acceleration. That comes from the rear tires and a spool. Everything else is a compromise to try and get the car to turn despite that fact.
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Old 09-30-2014, 08:25 AM   #21
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How is that going to be like a spool if one wheel drives around a longer arc than the other?!
A spool does too. The tires are spinning and scrubbing, just like they would with a spool.
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Old 09-30-2014, 08:38 AM   #22
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On power, a spool and a one-way behave in exactly the same way.
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Old 09-30-2014, 08:41 AM   #23
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A spool does too. The tires are spinning and scrubbing, just like they would with a spool.
Nevertheless. With a spool both wheels are ON power at all times regardless of everything else, with a one way, the wheel that has to follow the shortest trajectory is on power.

If you want a further elaboration, a spool will have the wheels attached to it fight each other around a corner, a one way won't. The spool will force the end it's attached to to take a trajectory that is a compromise between the wheels, a one way will have its end take the fastest trajectory by the very fact that the inside wheel has the shortest distance to travel hence it will "force" the outside wheel to take the long way around. The compromise imposed by a spool will inevitably drive the trajectory of its end wider than a one way (touring cars with spools push when compared with same with one way), the freedom given by the one way will allow the front end to hook around the corner.

All of the above assume traction (grip) is never lost in any significant way (other than scrubbing as you mentioned). This is just to eliminate from discussion situations like 4 wheel drift and so on.

I have watched a lot of videos and I have seen a lot of drifting in 1/8. This is vaguely similar to what happens on our track. Seems like on our track the car is indeed "point and shoot" without any significant loss of grip. Amazingly, the 1/8 goes around corners like a TC only tighter and a heck of a lot faster.
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Old 09-30-2014, 09:11 AM   #24
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On power, the outside is never going to freewheel. There is just not enough grip for that. Take out the rear belt and drive around with just front wheel drive. It's like ice as far as forward bite goes. On power, those suckers are spinning from drive, there is no over run on the outside. The only way to get the situation you describe would be to putt around a corner as slow as possible with just enough throttle to engage the clutch.
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Old 09-30-2014, 09:31 AM   #25
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Okay. I am talking about an electric 1/8 (that is what my friend has, the Capricorn electric conversion 1/8), so there is no problem with going very slowly.

But I can see your point. I guess something similar happens here. As someone mentioned before, perhaps the chassis leans enough that drive on the inside is not available hence the outside wheel drives.
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Old 09-30-2014, 09:49 AM   #26
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Even if the chassis doesn't roll, both tires will drive because of slip angle and slip percentages.

Except for when going very slowly, like driving your real car around a crowded parking lot, the tires are always acting at some angle of slip and percentage of spin. Actually they slip at parking lot speeds too just not enough to really have to worry about. When you hit the throttle, the tires start to spin at a rate somewhat FASTER than would be required to go the vehicle's current speed. With real cars on real rubber pneumatic tires, maximum acceleration occurs when the tires are being spun somewhere between 2-8% faster than the vehicle. More than that and you're smoking the tires. Less than that and you're grandma

I suspect optimal slip rates for foam tired rc cars is actually higher than that but have no solid data to confirm.

For the front tires to go around a corner with no scrub, the outside tire might need to spin 2 or 3% faster than the inside but if you are on the gas with an average slip of 10%, both tires are going to be spinning faster than the car is moving. The only difference is that the inside tire might have a slip of 11% while the outside is seeing only 9%.
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Old 09-30-2014, 11:07 AM   #27
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That is probably a good explanation, but as you say, we'd need some hard data to confirm. And I would need some first hand experience to understand.

I foresee a Capricorn will join my collection.
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