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Shaft drive TC... Why so few...

Shaft drive TC... Why so few...

Old 09-30-2014, 10:24 AM
  #31  
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Originally Posted by bertrandsv87 View Post
Come on guys... Mine is bigger than all of yours !!! LoL !!!!
I have yet to experience that elusive torque steer in all my tc4's , brushed and brushless, but my brushed mod car is way smoother than my brushless mod car, accelerating and decelerating.... In short carpet tracks I prefer to use brushed mod motors(6turn to 9turn)......just sayin....
What class are you racing?

I am racing an old Yokomo SD-SSG in 21.5 blinky and doesn't bother me much, but I wouldn't think it has a chance in mod. Or even 21.5 boosted.

I used to race this very same car in 27 turn (stock) brushed and it was okay, but in 19 the torque steer was obvious.

Either way, I love shaft drive, but don't have illusions. Until it's sorted out (like the Awesomatix but perhaps with the motor further in - just an aesthetics issue and just for my taste) I don't think there will be another (for me).

The TB EVO6 is a nice looking car like all the Tamiya cars (and I agonised no end over the desire to buy one), but is plagued with poor quality issues worthy of a banana republic economy. That and I think the gear diffs are a bit on the small side. Needs more oil volume and sturdier gears. Or a nice diff with straight gears like that on the last Corally TC.

If Tamiya listened to me, they'd put the crownwheel outside and the shaft (drive pinion) lower and to the side. That would require hypoid teeth on both. Offset the shaft to the battery side from the motor mount aft and to the motor side fore of the motor mount, and I'll pay anything that cost.
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Old 09-30-2014, 10:32 AM
  #32  
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Awesomatix has addressed the torque steer issue anyway with their floating diffs. But these are really only ran in mod classes, as even guys in 17.5 dont notice any torque steer effects. If your noticing it in 21.5, maybe something else is going on, or thats not a 21.5 your running.
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Old 09-30-2014, 10:39 AM
  #33  
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I race in all the classes with my tc4's: mod asphalt(brushless 3.5t), 13.5t, 17.5t, mod carpet(7turn brushed)... I run my rear ball diffs on the loose side most of the time, but I never experience the rear end coming loose on acceleration... Hell, I don't even see any torque steer in my Ntc3... I think running a front spool with lcd drives cures that torque steer issue... I use to run a 27t brushed in the 17.5t classes, and I did not finish last at all with the limited upgrades I had then, and when you consider that the 17.5t cars are only a second per lap slower than the mod cars, then you can easily understand why brushed mod motors can compete in small carpet tracks... Don't throwaway your brushed motors guys! Use them wisely....
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Old 09-30-2014, 02:02 PM
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Niznai, I think you are off the mark.

Torque steer comes from the spooling of mass in our cars longitudinally. Specifically all that matters is the mass moment of inertia of those parts (shaft and rotor, plus maybe a small gear or two), and how quickly the mass is accelerated or the rate of change of the RPM. The actual RPM does not matter, just how quickly it changes. These two directly influence torque steer... higher values mean more torque steer.

Now, a brushed motor has a greater amount of mass in the rotor and it is much farther away from the axis of rotation giving it a much much higher MMOI than a brushless rotor, which is lighter and more compact. Google MMOI if you are not following this.

And second, as for the acceleration of the parts. Assume two cars, one brushed, one brushless, that have very close to the same acceleration and top speed. Knowing brushed and brushless one knows the brushed car is geared higher than the brushless. Less torque but more RPMs. So the brushed cars rotor is going through more RPM change in the same amount of time as the BL.

All of this equates to brushed motors having much more torque steer than brushless because their parts have higher MMOI and higher rates of change of RPM.

Oh and I'd like to add I am building a TB04Pro2 I am pretty excited about.
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Old 09-30-2014, 02:11 PM
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I understood all of this perfectly and appreciate the explanation. Now one more question...How the hell do you people know this crap? Did I miss a class in high school or something?
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Old 09-30-2014, 02:15 PM
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Originally Posted by Carnage9270 View Post
I understood all of this perfectly and appreciate the explanation. Now one more question...How the hell do you people know this crap? Did I miss a class in high school or something?
None of this was ever taught at my high school. Fortunately there are many good books on race car engineering and vehicle dynamics out there.
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Old 09-30-2014, 02:19 PM
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Originally Posted by Carnage9270 View Post
I understood all of this perfectly and appreciate the explanation. Now one more question...How the hell do you people know this crap? Did I miss a class in high school or something?
I've got a mechanical engineering degree I don't use for anything but RC tech analysis!
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Old 09-30-2014, 02:28 PM
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Just remember that most of it is BS anyway. I personally don't think that the Awesomatix is a great car because of its shaft-drive but because of its innovative suspension and chassis design. The car would probably be just as good with a belt system.

As for torque steer, the only shaft drive car without that is the A700 with the isolated drive and front gearbox. When the front gearbox is bolted to the chassis, like in a TC4, HPI Pro 4, or any other shaft drive car, the torque twists the chassis and that changes the weight on all four wheels. It's just Newton's old action-reaction law. Whether this causes 'torque steer' depends on many other things, like how flexible the chassis is, the power of the motor, the grip of the racing surface, and other stuff.
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Old 09-30-2014, 02:42 PM
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These laws were here way before Newton, and the Ancient Egyptians knew them then..... In any case the torque steer effect is too negligeable to affect my tc4's, and if you want, you can create your own tc4 mobile gearbox system to try to solve the problem....
Originally Posted by DesertRat View Post
Just remember that most of it is BS anyway. I personally don't think that the Awesomatix is a great car because of its shaft-drive but because of its innovative suspension and chassis design. The car would probably be just as good with a belt system.

As for torque steer, the only shaft drive car without that is the A700 with the isolated drive and front gearbox. When the front gearbox is bolted to the chassis, like in a TC4, HPI Pro 4, or any other shaft drive car, the torque twists the chassis and that changes the weight on all four wheels. It's just Newton's old action-reaction law. Whether this causes 'torque steer' depends on many other things, like how flexible the chassis is, the power of the motor, the grip of the racing surface, and other stuff.
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Old 09-30-2014, 02:43 PM
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Originally Posted by DesertRat View Post
Just remember that most of it is BS anyway. I personally don't think that the Awesomatix is a great car because of its shaft-drive but because of its innovative suspension and chassis design. The car would probably be just as good with a belt system.

As for torque steer, the only shaft drive car without that is the A700 with the isolated drive and front gearbox. When the front gearbox is bolted to the chassis, like in a TC4, HPI Pro 4, or any other shaft drive car, the torque twists the chassis and that changes the weight on all four wheels. It's just Newton's old action-reaction law. Whether this causes 'torque steer' depends on many other things, like how flexible the chassis is, the power of the motor, the grip of the racing surface, and other stuff.
Think there will be a day when Awesomatix will ditch the shaft and make a belt car using their patented shocks?
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Old 09-30-2014, 02:46 PM
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They already tried that, and they concluded that shaft drive was faster...
Originally Posted by inpuressa View Post
Think there will be a day when Awesomatix will ditch the shaft and make a belt car using their patented shocks?
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Old 09-30-2014, 02:49 PM
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Aren't the dampers just smaller copies of the Sachs Rotary Damper?
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Old 09-30-2014, 02:51 PM
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Originally Posted by bertrandsv87 View Post
They already tried that, and they concluded that shaft drive was faster...
Maybe that was just a case of poor engineering.
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Old 09-30-2014, 02:57 PM
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Originally Posted by bertrandsv87 View Post
They already tried that, and they concluded that shaft drive was faster...
I think that needs to be revisited... because shaft would have dominated the world by now if that was true.
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Old 09-30-2014, 03:03 PM
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Originally Posted by patorz31 View Post
Aren't the dampers just smaller copies of the Sachs Rotary Damper?
I've never seen the internals of an Awesomatix shock so I have no idea (anyone got pics?) but I don't think so. The Sachs dampers were not cylindrical.
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