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Old 04-21-2003, 05:29 PM   #781
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Spinning a car

What does it mean to "spin" a car? Does it mean giving the car a push with the motor not connected to the drivetrain?
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Old 04-21-2003, 05:34 PM   #782
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Axiom5B,

i'm no expert. can say that i've just started the hobby.
would be very pleased if i can achieve 6-7 second goal.

if anyone does not mind me asking, what do you have to do to get a longer free wheeling on a shaft driven car?

again, only using stock bearings at the moment, not sure if using ceramic bearing would help.

any suggestions?

Thanks
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Old 04-21-2003, 05:51 PM   #783
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A longer spinning drivetrain doesn't mean anything. There are too many factors that contribute, both good and bad. Some examples of both good and bad things that both make the drivetrain spin longer would be: Good-high quality bearings, lite lube, perfect gear mesh. Bad- More rotating mass!!!. A lighter drivetrain will be more efficient and put more power down than a heavier one but will not spin in the air as long.
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Old 04-21-2003, 05:55 PM   #784
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I've used a 6 mo. old Yokomo persision bearings and my wheels spin for about 3 - 4 seconds. Used a Royal Oil and adjusted a shims on the diffs.
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Old 04-21-2003, 05:56 PM   #785
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Quote:
Originally posted by SpeedTech
Hi Guys,

We are still looking on schedule for delivery of cars this week. We should be able to start shipping them out this Friday.

Steve Wang
But, what about the email that we were supposed to recieve a week before the arrival? Cause this is my first pre-order from you guys, so how do we go about selecting the shipping method and all that stuff?

I'm a little confused about how we finish the ordering process. Is that whats going to be in this email?

Thanx
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Old 04-21-2003, 05:58 PM   #786
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Quote:
A lighter drivetrain will be more efficient
that is true.

Thanks Mo, Futureal

Last edited by racer; 04-21-2003 at 06:15 PM.
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Old 04-21-2003, 06:02 PM   #787
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Quote:
Originally posted by Axiom5B
Wouldn't a heavier driveshaft give the drivetrain more momentum and therefore spin longer?

3 seconds? I have seen TC3's with drivetrains that spin for 6-7 seconds easy.
That is precisely why the "spinning the wheels" test is not a good indicator of how well a car is going to perform on the track. Because of its mass distribution, a shafted car will spin longer than a belted car in almost any situation. This isn't to say that it's not worth making it spin as freely as possible, but whether a car spins for 3, 5 or 7 seconds is not going to matter whatsoever on the track.

You need to think of the drivetrain from the motor's perspective, not from the wheels/shaft/belt perspective. If I'm the motor, how much energy will I need to expend to spin the car's drivetrain under load? This is where the efficiency of the drivetrain comes in. Well-performing bearings, well-meshing gears, a clean belt/shaft, freely spinning CVDs and so on are all things that could impact this.

Once the car goes into "coast" mode, the difference between a 7-second-spinning shaft car and a 2-second-spinning belt car is irrelevant. The drag put on the drivetrain from the magnetic friction (inefficiency) of the motor, from the friction between the wheels and the racing surface, and the friction from the wind resistance of the car's body will all negate the issue. This argument, of course, assumes that we are not talking about extreme variances, like a lead shaft versus an aluminum shaft, or a chain-drive versus a belt-drive.

I'm not sure I'm explaining it correctly, but I think if you put your mind to it and visualize all the different factors, you will see that it makes sense.

edit: Took me too long to type, and mo beat me to the punch.
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Old 04-21-2003, 06:13 PM   #788
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My sentiments exactly futureal. Perhaps it be better to see how easily your drivetrain "spins up" as opposed to giving your wheels a good crank and see how long it spins. If you can blow on your spur, and the drivetrain spins up then I'd suppose you're pretty much good to go Mine used to do that, but not anymore
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Old 04-21-2003, 06:19 PM   #789
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futureal,
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Old 04-21-2003, 07:08 PM   #790
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My single belt car is pretty efficient.

Darkseid- Mo's last breakage was a HUGE hit and the car went about 8 lead laps before it broke. I won't be jumping on the yok bandwagon anytime soon but it did get to race while my faster qualifying car was in the pits.
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Old 04-21-2003, 07:21 PM   #791
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I had a straightaway lead from the 9th starting position when I broke too. I destroyed the front of that Losi though...LOL
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Old 04-21-2003, 07:26 PM   #792
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I agree with the thoughts about the free spin test. I have raced a Losi XXXS since they came out and they have always been very effecient, yet never really spin for a long amount of time. I do not want something that is tuff to spin but would prefer something that is fast on its wheels verses with the tires off the ground...lol

So I guess a better question would be Mo and other SD owners, do you feel the SD is an effecient car with good punch and top end?

Jeff
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Old 04-21-2003, 07:27 PM   #793
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A more valid test would be to take two different cars and do a drag race. The cars should have the same weight and the same ESC, motor, tires, and batteries should be used.

I think it was in this thread or another that John Bull tried this.

-Headbanger
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Old 04-21-2003, 08:09 PM   #794
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Quote:
Originally posted by Headbanger
A more valid test would be to take two different cars and do a drag race. The cars should have the same weight and the same ESC, motor, tires, and batteries should be used.

I think it was in this thread or another that John Bull tried this.

-Headbanger
The reaction time in a drag race Is too much of a factor. eaven If you run them individually with a tree and timing system the reaction time of the driver is never going to be exactly the same from race to race.
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Old 04-21-2003, 08:25 PM   #795
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Ya i agree with you all on the drivetrain spin thing, i was just making a comment about the previous post. A drivetrain that spins when you blow on it is a free drivetrain definitely. However, usually those ones that spin for 6-7 seconds are very easy to spin by blowing

Quote:
Originally posted by rtypec
My sentiments exactly futureal. Perhaps it be better to see how easily your drivetrain "spins up" as opposed to giving your wheels a good crank and see how long it spins. If you can blow on your spur, and the drivetrain spins up then I'd suppose you're pretty much good to go Mine used to do that, but not anymore
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