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Old 02-18-2003, 11:23 PM   #1
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Arrow How free is your drivetrain?

prompted by john stranahan's recent post in the tc3 assembly tips thread, i was wondering how long your race ready car drivetrain will spin with your pinion off? nothing crazy here, just by pushing the tires. i've seen some shaft cars roll and actually have the spur settle back in. as for the belt variety, i've played with some pros cars and have not been impressed. i've also heard of accounts of some losi's and xray's spinning for 5 to 10 seconds. but i'm looking for facts here. not the shaft vs. belt discussion. just a poll of sorts to gather some data. thanks.
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Old 02-19-2003, 12:24 AM   #2
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Default Please note...

the weight of a tire and bearings can make a diference.
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Old 02-19-2003, 12:57 AM   #3
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Hey Seaball, interesting post.

Can you please enlightning me on how I measure this?
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Old 02-19-2003, 01:12 AM   #4
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i know this is not a shaft vs belt thread....but i seems to get smoother drivetrain from my belt cars(414m2/C4.1/SV102) than my shaft cars(3 Barracudas/1 TB evo).....cant remember which thread was it but there was either evo3 or tc3 that others claim to be able to make the spur moves by blowing at it??anyone with shaft drive car willing to share any general tips on freeing the drivetrain??i've checked the front and rear diff without the input gear from the shaft attached and it is free...rooll the center shaft with no diffs attached holder and it's rolls nicely and freely also .....only when i assembled everything than i seems to have some drag....gear mesh between input gears and diff gear seems correct with some backlash to it...could the shaft be bent??but it couldnt be on all my 3 Cudas that's for sure...all these were testred with old gear and even new ones....hope someone can help here....
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Old 02-19-2003, 01:36 AM   #5
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my TB EVO III will roll for about 10-15 sec, and it will turn over by simply blowing on the spur gear.

this is also done with the optional aluminum axles, i'm sure with the steel ones it would spin for longer since they would provided more weight to keep it spinning.

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Old 02-19-2003, 06:13 AM   #6
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Friend's TC3 would spin for 7-10 seconds without wheel attached!
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Old 02-19-2003, 08:48 AM   #7
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Your not gonna get the belt cars to spin for a terribly long time because the belts have to bend around the gears and this requires force. A belt transmission could very well require less force to move, but spin for a shorter amound of time because it is constantly scrubbing energy off when it flexes the belt. Alll a shaft car has slowing it down it the friction of the bearings and the drag the tires create moving through the air. TO get a accurate measure of how free your drive train is you would have to have a way of measuring the force required to move the spur. But to compare this all cars would have to have to same spur and the same internal ratio, so you cant realy compare.

Last edited by Cyclonus; 02-19-2003 at 08:51 AM.
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Old 02-19-2003, 09:59 AM   #8
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Quote:
Originally posted by Ian
i know this is not a shaft vs belt thread....but i seems to get smoother drivetrain from my belt cars(414m2/C4.1/SV102) than my shaft cars(3 Barracudas/1 TB evo).....cant remember which thread was it but there was either evo3 or tc3 that others claim to be able to make the spur moves by blowing at it??anyone with shaft drive car willing to share any general tips on freeing the drivetrain??i've checked the front and rear diff without the input gear from the shaft attached and it is free...rooll the center shaft with no diffs attached holder and it's rolls nicely and freely also .....only when i assembled everything than i seems to have some drag....gear mesh between input gears and diff gear seems correct with some backlash to it...could the shaft be bent??but it couldnt be on all my 3 Cudas that's for sure...all these were testred with old gear and even new ones....hope someone can help here....
Ian

Cuda's need a little TLC on the 16T & 39T gears to make the drive train smooth and spin for a long time...
For starters..... you'll need some 400~600 grit wet dry sand paper and you'll need to spend about 3 hours just removing all of the peaks on the bevel and diff gears and buy doing this you'll be able to tell just by the gear mesh and that there is less noise too!! especially if you have a Motor/shaft mount holder ( which usually makes the drive train noisy )

But with the 400( 320 is what I use less time )
start to remove a liberal ammount of material ...say about 1mm on the 39T Diff gear ....

This should take a whole Sh!t [email protected] of resistance out of the Barracudas' drive train

also a little bearing prep doesn't hurt either

Try this and let me know
BTW my cuda's on aveage can spin for about 10~14 seconds without tires !! but before all of the prep work they only spun for about 5~6 tops


-Dave
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Old 02-19-2003, 10:27 AM   #9
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I have seen professional drivers do a roll test. Pick a slope and let it roll from a stop.

no batteries

all cars could compare then.

Later
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Old 02-19-2003, 10:34 AM   #10
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The importance of free drivetrain is great in stock racing. The thing you have to consider is the loaded friction of a drivetrain. The ability of a drive train to freespin can be missleading. a tc3 will out freespin a xxxs every time but wich is more efficient its hard to tell. A tc3 has 8-10 friction points at all times when loaded because of the gearmesh and the losi has much less. I think it is better to reduce frinction than to get upset about freespin.
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Old 02-19-2003, 10:42 AM   #11
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Default Smooth Drivetrain

You can also check a drivetrain before and after repairs with you charger, Turbo 35, Lrp, or what ever has a motor feature.
First check the motor at 4.0v, check the amp draw. Possible stock motor is from 5-7 amp give or take, then install the same motor into a car. Set the pinion to spur mesh and the check the amp draw with the same voltage. Try to get the closest to the original amps without the drivtrain. I run a Mission, and with the stock motor pulling 7.0 amps, it would pull about 7.2 amps. So the drivetrain requires a .2 amp to move it.
This another way to determine efficiency. And it is only a guide.
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Old 02-19-2003, 10:48 AM   #12
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Default How free is your drivetrain?

I say someone checking freeroll on his 414M at the track. He spun the spur gear with his finger and it must have turned for OVER 15 seconds. My jaw just dropped and I walked away.
My Pro-3 get a few revolutions of the drivetrain and that's it, but interestingly enough, there are only maybe one or two other cars that are faster on the straight and I tend to gear on the conservative side.
I tried removing the shield/seals on the bearings and really didn't notice any difference except they got gritty after one race. I think the dirt in the bearings slows you down more than the shields would.
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Old 02-19-2003, 11:31 AM   #13
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Pops , with a belt drive car you need to use a belt dressing to soften up the belts..

There are lots of ways to soften up the belts, some use motor spray , others used tire grip. I will let the others pitch in their suggestions...

But the answer to your problem is with the belts ....
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Old 02-19-2003, 01:29 PM   #14
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I don't know if this is correct but wouldn't shaft drive cars spin for longer because all of the drive train components (diff gears and shaft) are rotating and carrying energy like a flywheel, where as belts do not "rotate" and cannot carry energy in the same way.
IMO this isn't a fair test for a free drive train, does this make any sense?
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Old 02-19-2003, 01:48 PM   #15
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I have been going back and forth between my XXXS belt car and my TC3 and heres my data. My Tc3 spins for about 5 or 6 seconds. Could be better-but I get lazy on pulling out all the carpet fuzz, etc..... ITs free enough that I dont feel any loss in performance.

My Losi G+ will spin for only 2 seconds-maybe-But it boogies on the track so I feel thats good enough free spin for the belt car.

More important to the free spin I think is the resistance you feel while turning it over slowly by hand. And not the start-up resistance, but the resistance from constant-but even pressure. The TC3 is like extremely little resistance and the Losi is very light resistance. Both are excellent. If you could design a machine that could display the amount of pressure needed t keep the drivetrain spinning at a set RPM-maybe then the answers would be clearer.

LouisB-what a cool concept about the flywheel effect of a shaft car and that of a belt car. Very cool.
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