R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 09-30-2014, 11:24 AM   #31
Tech Elite
 
niznai's Avatar
 
Join Date: Feb 2009
Location: All over the place
Posts: 2,940
Default

Quote:
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.
__________________
Team Greasy Weasel

The best upgrade to any car is some driver skill.
niznai is offline   Reply With Quote
Old 09-30-2014, 11:32 AM   #32
Tech Elite
 
theproffesor's Avatar
 
Join Date: Feb 2005
Location: Lugoff SC
Posts: 2,834
Trader Rating: 58 (100%+)
Default

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.
__________________
The brighter the picture, the darker the negative. USVTA member #112
theproffesor is offline   Reply With Quote
Old 09-30-2014, 11:39 AM   #33
Suspended
 
Join Date: Feb 2011
Posts: 6,240
Trader Rating: 1 (100%+)
Talking

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....
bertrandsv87 is offline   Reply With Quote
Old 09-30-2014, 03:02 PM   #34
Tech Addict
 
Wade....'s Avatar
 
Join Date: Nov 2011
Location: St. Paul
Posts: 565
Trader Rating: 2 (100%+)
Default

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.
__________________
Wade Huesman, TCORC Secretary/Pencil Pusher
Wade.... is offline   Reply With Quote
Old 09-30-2014, 03:11 PM   #35
Tech Master
 
Join Date: Feb 2014
Location: Kirkland, WA
Posts: 1,033
Trader Rating: 6 (100%+)
Default

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?
__________________
-Mike B.
Carnage9270 is offline   Reply With Quote
Old 09-30-2014, 03:15 PM   #36
Tech Lord
 
wingracer's Avatar
 
Join Date: Nov 2007
Posts: 12,861
Trader Rating: 24 (100%+)
Default

Quote:
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.
__________________
Sean. Certified speed crazed mowron.
Team Shepherd USA
www.ashfordhobby.com
wingracer is offline   Reply With Quote
Old 09-30-2014, 03:19 PM   #37
Tech Addict
 
Wade....'s Avatar
 
Join Date: Nov 2011
Location: St. Paul
Posts: 565
Trader Rating: 2 (100%+)
Default

Quote:
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!
__________________
Wade Huesman, TCORC Secretary/Pencil Pusher
Wade.... is offline   Reply With Quote
Old 09-30-2014, 03:28 PM   #38
Tech Elite
 
DesertRat's Avatar
R/C Tech Elite Subscriber
 
Join Date: Mar 2011
Location: Sniffin the 'Sauce Fumes
Posts: 2,705
Trader Rating: 2 (100%+)
Default

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.
__________________
I race toy cars for fun. If I need to explain, you'll never understand.
Current rides: Diggity DC4 Chassis #10. Losi JRX-S Type R. Losi 22 4.0, CRC Xi (retired), CRC Altered Ego Aluminum Chassis. Associated B4 based dirt oval late model.
WTB: Carpet racing in Arizona.
DesertRat is offline   Reply With Quote
Old 09-30-2014, 03:42 PM   #39
Suspended
 
Join Date: Feb 2011
Posts: 6,240
Trader Rating: 1 (100%+)
Default

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....
Quote:
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.
bertrandsv87 is offline   Reply With Quote
Old 09-30-2014, 03:43 PM   #40
Tech Master
 
Join Date: Sep 2009
Posts: 1,904
Trader Rating: 9 (100%+)
Default

Quote:
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?
__________________
Lost in RC limbo
inpuressa is offline   Reply With Quote
Old 09-30-2014, 03:46 PM   #41
Suspended
 
Join Date: Feb 2011
Posts: 6,240
Trader Rating: 1 (100%+)
Default

They already tried that, and they concluded that shaft drive was faster...
Quote:
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?
bertrandsv87 is offline   Reply With Quote
Old 09-30-2014, 03:49 PM   #42
Tech Master
 
patorz31's Avatar
 
Join Date: Nov 2007
Location: Edmonton Ab
Posts: 1,430
Default

Aren't the dampers just smaller copies of the Sachs Rotary Damper?
__________________
Northern Alberta Scale Car Auto Racers Pres. and Promotions
SCHUMACHER RACING Canada,TEAM POWERS, Mon-Tech,Sanwa
patorz31 is offline   Reply With Quote
Old 09-30-2014, 03:51 PM   #43
Tech Apprentice
 
fitforbattle's Avatar
 
Join Date: Jan 2010
Location: Skara, Sweden
Posts: 67
Default

Quote:
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.
__________________
Yokomo BD7 / SpeedPassion Reventon Pro AJ Edition / LRP x12 Vector Octa-wind 5.5T / Futaba S9352HV / Gens Ace 5000mAh
fitforbattle is offline   Reply With Quote
Old 09-30-2014, 03:57 PM   #44
Tech Master
 
Join Date: Sep 2009
Posts: 1,904
Trader Rating: 9 (100%+)
Default

Quote:
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.
__________________
Lost in RC limbo
inpuressa is offline   Reply With Quote
Old 09-30-2014, 04:03 PM   #45
Tech Lord
 
wingracer's Avatar
 
Join Date: Nov 2007
Posts: 12,861
Trader Rating: 24 (100%+)
Default

Quote:
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.
__________________
Sean. Certified speed crazed mowron.
Team Shepherd USA
www.ashfordhobby.com
wingracer is offline   Reply With Quote
Reply



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 03:18 AM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net