Cvt in rc cars

[steelo]

I was thinking over the weekend, my (real) car uses a ‘CVT’ transmission which really is nothing more than 2 ‘pulleys’ that change sizes as the vehicle accelerates/decelerates and a belt. What if there was a way to implement this into R/C cars? It seems like a simplistic solution to gain optimal torque and top end speed.

[Percymon]

Good old Daf technology - two cones and a rubber belt for constantly variable drive

Fit a fast motor, ballooning of the tyres alters the gear ratio lol!

 

[steelo]

LOL…true. Most people hate CVT’s but I actually love it in my HRV =)

 

As far as application in a RC car, I would think it would be beneficial over fixed gears. You should be able to get an ideal gear ratio to provide optimal torque/power.

 

[danb1974]

At least on electric cars, maybe there would not be such an improvement, since an electric motor does not have a torque issue when starting, and it can go to really high rpm (over 30.000 rpm)

[steelo]

True, but even with an electric motor I would think it would be more efficient.

[Wooders28]

IC engines have a fairly narrow power band meaning you can set the CVT to the best rpm to suit the application. 

They tried it on F1 cars back in the 90's (a very young David Coulthard,if you YouTube it!),but it didn't take off.

Elec motors have torque from 0 rpm so,I'm guessing the benefits, If any, due to weight and extra gear complexity, would be minimal.

[Mokei Kagaku]

Not the DAF principle, but Kyosho released their CCVT series 25+ years ago.

http://www.classic.rc-junkies.net/?p=2882

 

 

[Backlash]

Its been done.... By RC4WD for the 1/14 scale trucks..
 

 

[NobbySideways]

I love it. Proper engineering.

 

[Mokei Kagaku]

On ‎10‎.‎05‎.‎2016 at 6:39 AM, Backlash said:

Its been done.... By RC4WD for the 1/14 scale trucks..

Technically impressive, no question, but for what purpose? I mean, the Tamiya trucks hardly need more than one ratio anyway (for virtually all purposes enough torque and speed in 2nd gear), so the CVT imho doesn't add any actual benefit. Also, manually shifting the gears of 3-speed gearbox is a big part of the fun driving them. Which is then lost with the CVT.

 

[Backlash]

44 minutes ago, Mokei Kagaku said:

Technically impressive, no question, but for what purpose? I mean, the Tamiya trucks hardly need more than one ratio anyway (for virtually all purposes enough torque and speed in 2nd gear), so the CVT imho doesn't add any actual benefit. Also, manually shifting the gears of 3-speed gearbox is a big part of the fun driving them. Which is then lost with the CVT.

 

Maybe its for those who would like to model a truck with an automatic gearbox?

OR simply not needing or having to install a 2nd servo for the gear shift so that the truck can be driven from a 2CH radio, and still get good low down torque, and a reasonable top speed..??

I run 55 + turn motors in mine, and I still feel that an additional 2:1 transmission would be useful so that I could use second and third gears..

[Mokei Kagaku]

3 hours ago, Backlash said:

Maybe its for those who would like to model a truck with an automatic gearbox?

OR simply not needing or having to install a 2nd servo for the gear shift so that the truck can be driven from a 2CH radio, and still get good low down torque, and a reasonable top speed..??

I run 55 + turn motors in mine, and I still feel that an additional 2:1 transmission would be useful so that I could use second and third gears..

 

If someone really want an AT in their truck, I'm sure the RC4WD CVT is OK. As you of course know, back when 4ch RC kits were so much more expensive than 2ch, the "saving" of one channel would save quite a bit of money and probably justify the additional cost of the CVT.  As cheap as RC-gear has become, that would hardly be a valid argument anymore.  And personally, I think the manual shifting is thee major contributor to the fun of running the trucks. Not the least when pulling a heavy trailer and using the downshifting to slow the truck down before a turn.

 

As for your wish for a lower overall ratio, I fully agree, and as I don't know the ratio "span" of the RC4WD CVT, it's possible that this is a big advantage over the original 3-speed MT? Back when the King Hauler and Globe Liner were released, it was virtually impossible to source high turn 540's to fit, so instead we sourced 8t pinions with a lot of effort and installed 27t rotors in modified motor cans (with strong magnets and advanced timing for lower rpm), especially to slow the trucks down a bit in 3^rd gear, rather than any need of more torque.

 

(A friend and I also got the 4:1 transmissions from Graupner that are mounted as an extension of the motor (intended for motor gliders). They are compact, dustproof and with all tempered steel gears (and ball/roller bearings of course) and surprisingly high quality for being from Graupner, but unfortunately a bit too long at about half the length of a 540. So my friend ended up using it in his Kyosho RV and I in my CC-01 instead.)

[Backlash]

48 minutes ago, Mokei Kagaku said:

 

If someone really want an AT in their truck, I'm sure the RC4WD CVT is OK. As you of course know, back when 4ch RC kits were so much more expensive than 2ch, the "saving" of one channel would save quite a bit of money and probably justify the additional cost of the CVT.  As cheap as RC-gear has become, that would hardly be a valid argument anymore.  And personally, I think the manual shifting is thee major contributor to the fun of running the trucks. Not the least when pulling a heavy trailer and using the downshifting to slow the truck down before a turn.

 

A lot of people just feel more comfortable driving with a wheel type radio, and there are very few wheel radios that offer a 3 position switch as a 3rd channel to operate the gears..Those that have children driving their rigs may also find that a basic 2ch radio (be that wheel or stick) is preferable to a complex 4+ channel radio.. Most 4+ CH radios are also quite large, and maybe more difficult for children to hold and use..

Children may also find the 3 speed box to be a little complicated, and the CVT transmission should still offer a wider speed band than a single speed gearbox, or locking the 3 speed in just 1 gear..

Specs can be found here..
http://store.rc4wd.com/EcoDrive-114-CVT-Automatic-Transmission-for-Tamiya-114-Semi-Trucks_p_4897.html