Anybody thinking 3,4 or 5 speed

[humongous]

Here's a thought. Why not rig up a 5 or even 6 speed transmission on a standard road car maybe HPI RS4. Wouldn't that carry it well over 100mph?

Cheers,

Humongous

[EddieWeeks]

I think a CVT (constant variable transmition) is the way to go... A 5th scale
could use one off a scooter.

Eddie Weeks

[wildcatter]

dear humongous i was wondering if u know of any good shaving sites ? :eek:

[minitdriver]

Why not machine one yourself?Putting a 4 speed tranny on a RS4?Not happenin.Unless you stretched the chassis.That would be the easiest way.
STay classy readers
Ken

[mgs9]

I dont know about trannys in these cars but in real cars if the final gear is too wide when you change into 5th, it will actuly slow down do to the lack of power. Meaning yea you might have 5-6 gears but will there be enough power to use them.

[DaFF]

5 or 6 speed in a r/c car means loads of pinion and gears, thus leading to more rotationnal mass.

That is the reason why nobody has done it before.

Further more, it is very difficult to set each gear to engage one after the others... ( on a centrifugal system ). Gosh, ppl with only 2 speeds have already problems, I don't want to know how to set-up a 6 speed system LoL

Eddie,

A CVT is usually done with belt and pulley that have a variable diameter.

On those system, the power is transfered by the side of the trapezoidal belt.

Given the friction coefficient of belt onto pulley, I can tell you:

1- It's off no use on high power engine ( although I think it should be OK for r/c car )

2- It's inefficient as hell, meaning you'll lose of lot of power throught this system.

I am saying this from first hand experience with them ( believe it or not, I've been racing mupped when I was young, high end mupped - 49.9 cc engine - that goes well over 70 mph on skinny tires - very scarry ! )

I've seen very tricky CVT, I've play a lot on the mass off the CVT system, the mass are there to engage sooner or later, pretty neat stuff...

DFF

[EddieWeeks]

So... Why would it not work... My 5th scale had a 23 cc.. there is
plenty of room for a 50cc with a CVT.

Do you know a web page so I can look at a few of them... Thanks

Eddie Weeks

[CENthasizer]

Can someone explain a CVT? how it works? I may have an idea i saw in a car mag for a transmission, but i want to know if its the same thing you guys are talking about.

[CENthasizer]

Ok here is what i am talking about. I am NOT good at CAD and mechanical objects! so i dont know how to put this in 3D, which would express it easier.
The yellow lines are the springs, the white cones are cone like shapes which can move laterally. the red lines are the belt. this is looking at it from the front obviously. Anyways as the speed increases the cones move out making the gear size become smaller with speed. Is this what you guys are talking about?

[DaFF]

Yes, this is what I am talking about, eventhough CVT system are way more complicated than that LoL:

- you have to have a system to keep the tension of the belt constant because as the pulley diameter will become smaller, the belt will get more and more slop
- there are as well calibrated weight rollers that will push the moveable side of the pulley
- obviously a clutch too to engage or disengage the system

anywya, there are mutliple CVT system.

The one I know are from mupped and scooter.

Usually mupped have a single pulley CVT system while scooter have a dual CVT.

Mupped have the engine rotating on a axis in order to compensate for the variation of diameter of the pulley i.e. having the belt tension constant.

Scooter use the CVT in a different way, the engine is fixed and that's where the double CVT comes handy ( the belt tension is constant on a double CVT system )

I didn't find a lot of info on CVT system, but this might help you understand how it works ( dual CVT system, both diam eter of pulley have variable diameter):

http://perso.wanadoo.fr/x9-500/images/transys1.gif

double CVT system on high end 500 cc scooter:

http://perso.wanadoo.fr/x9-500/images/techn/400variateur7.jpg

Here is the mupped system for variable diameter pulley:

http://zone103.free.fr/mob/images/schemavario.jpg

Mupped usually don't use rollers but rotating mass instead.

Single CVT system on a mupped:

http://zone103.free.fr/mob/images/variocompet.jpg

I can see why someone would like to get a system like that on a high speed r/c car.

My best recommendation would be to buy a CVT system from the race scooter and mupped.

The Italian are the king when it comes to parts for racing mupped and scooter.



DFF

[DaFF]

A few sample of racing CVT system you can buy off the shelf:

Polini speed:

http://www.ales-moto.com/img/Z_News02.jpg

Malossi mutlivar:

http://membres.lycos.fr/jmobylette/photos%20test/vario05.jpg

Bidalot G1/G2

http://membres.lycos.fr/jmobylette/photos%20test/vario01.jpg

Doppler ER1/ER2/ER3

http://membres.lycos.fr/jmobylette/photos%20test/vario06.jpg

and Girodau to name a few...

Good luck !

DFF

[furnik28]

record player speed control idea thread

[mgs9]

record player speed control idea thread

Wouldn't that be just like a speed controll. :confused: You would just be adding more or less voltage to the motor.
Thats how I would assume it would work I never took a record player apart.

[furnik28]

:D :p :eek: you have 3 discs, 2 are the same diameter. they have a o-ring or some other friction contact to the big disc. one little one is conected to the engine whitch moves up and down the splined shaft when u accelerate. the power gose through the big disc and tranfers the power to the diff it acts like a fly wheel its got no electronics in at all