What's an impulse variator?

Your foot on the brake pedal of your car.

And what happens to efficiency?

Of what?

Efficiency is 100%. 100% of the energy gets dissipated in heat. Even the sound that is emitted gets dissipated in heat and it's generation is a load on the system so still 100% efficiency, that is if slowing is your objective! You weren't specific as to the objective.

An example of an Impulse Variator is a speed controller for DC separate excitation or permanent magnet motors operating from a single phase AC mains. The rotation speed of the motor is governed by synchronizing and controlling the duration of each cycle of ac applied to the motor.

Correct!

It could be one of those invented sci(?)-fi type words. I found this star-trek reference by googling.

But the German translation (Schlagstärkevariator) suggests that it could also be a controller for the size of gas pulses. (Otherwise known as a sphincter?)

I am a nasty creature, I got him to show it to me.It wasn't bulky and control was by one lever.It was spun by a very small induction motor and the change of speed was smooth and there were no strange noises, can't figure out how it's different by the regular variator.He claims enormous efficiency and one internet search leads me to an AUDI car but nothing like a detailed description.I regulated it close to 20 rpm and loaded it as hard as I could but it didn't feel a thing.

This guy is into special things, he's into harmonic drives and he talks about friction based harmonic drives...

"enormous efficiency" Like how much greater than 90%?

I have been told (unable to check) that the usual limits on toroidal variators are losses due to flexure at the high pressures needed to stop slippage. Theoretically loss at low load could be reduced by using variable pressure - but that doesn't seem to relate to "impulse". Could he be using some sort of vibration to increase the adhesion without excessively increasing contact area (and so minimise slippage?)

Hello Tedi,

Me thinks your friend is pulling your leg!

An Impulse variator is any means that varies the speed of a motor.

bb

As long as there is an impulse involved.

In the electronic method a rheostat controls motor speed in a very wasteful way compared to an impulse controller that varies the "when "and "for how long" of applied power.

The mechanical description above describes the smoothed transfer of engine power to the drive axels of a car by Impulse Variation.

There was a commercial on TV that describes the affect by showing a car with a cup of coffee on the console that doesn't spill during acceleration and shifting.

Hi kudukdweller9,

I have not seen that particular advert. But I have seen a demonstration of driving where a pint of beer is placed on the hood. Much the same thing really?

Take it easy my friend.

bb

Exactly.

I am glad they had variations on the same theme because I don't like redundant commercials.

how about a billiard cue? with this you can change the direction spin an impulse of the ball

Hello Epke,

I suppose you could say your right foot is the best known impulse variator?

bb

I dunno about you, but I would say its the right hand!

Hello chris288,

I suppose it all depends what you ride?

Hey, take care OK

bb

Well if i ride my employees it is my right foot, work harder you lazy bums!

when i ride my...uhm yeah

?

Always on topic...lol. I wonder what part of that was the variator?

I guess the variator is the hand that slaps him

Blink thank you for your answer;Guest make an account an send me a personal message; the rest of you - it's good when an engineer has a background in electronics but when one hears "impulse variator" and imagines something strictly electrical that means he/she is a poor engineer

Hello Tedi,

How are you?

I do not think you are a bad Engineer at all ! You were just thrown a phrase that through you for a while, that is all. [p[] But, you know you will get a straight answer from your friend's on this site, right?

It is sorted now, do not worry about being a bad Engineer. The fact is you must be a good Engineer because your 'mind' and thoughts automatically went to find an 'Engineering' answer to solve what was a new question to you?

Take care

bb

Hello Kris,

Hope all is well with you?

I guess the variator is the hand that slaps him.

Nice one Kris!

bb

Toroidal variators.

Found this: I saw the principal in a Pop Sci mag some time back too.

Above is the Torotrak variator, it affects the speed of rotation of the sun gear and is responsible for the smooth variation of ratios, which the Torotrak transmission produces.

Inside the variator are two pairs of discs. The space between each pair of discs forms a hollow doughnut shape or 'toroid'. Within each toroidal space there are three rollers. These rollers transmit drive from the outer, engine driven, discs to the output discs located in the centre. The rollers transfer power between the input discs and the output discs via a traction fluid.

Each roller is attached to a hydraulic piston. The pressure in the pistons can be increased or decreased to create a range of reaction torque within the variator.

The variator shown below is an inline piston design, where the packaging requirements require a compact lever arrangement as shown in the picture below.

A new even more compact version of the variator has recently been developed where the rollers are all controlled by one piston. Torotrak have termed this design 'Epicycloidal Roller Control' (ERC).

The problem with these (and all other mechanical variators I have seen) is that the velocities of the surfaces don't match all the way across the contact area, which results in frictional losses. Narrower contacting regions have lower frictional losses but there are limits to this, both in terms of maximum torque transmission and the onset of flexural losses.

I knew about friction losses due to slipping but I just learned about flexural losses.

Will you explain in a sentence or two, please?

Basically it's just the material of the "wheels" distorting under pressure. As the material returns to its original position, a proportion of the energy required to produce that distortion is converted directly to heat, and a proportion goes to vibration (and eventually to heat). The distribution between these effects and frictional losses depends on the materials and profiles of the components. Designers usually try to minimise overall cost (including manufacture, wear, and losses) - although in consumer markets there may be an over-emphasis on either manufactured cost or losses under specific published conditions.

Although what you say is true, in practice, these units are remarkable efficient, with the toroidal types and steel belt types being 97% or more efficient. Surprisingly, the fabric "rubber" belt style (as used on snowmobiles and motor scooters) can be 95% efficient, even with their relatively soft materials.

Audi found, several years ago, that fuel efficiency was better with CVT than with manual transmission, so (in their case) the ability to run the engine at closer to its efficiency peak more of the time canceled frictional losses. Of course, even straight cut gear teeth have to slide across one another to function, and quieter types do even more sliding.

I think it depends on the conditions of use -and whether the measurements correspond to this. If you measure at maximum load the variator should be efficient. But my understanding is that, unless you provide a secondary mechanism to correct the pressures or spacing*, the loss in a variator is almost independent of load, whereas at least some of the loss mechanisms in a gearbox reduce with reducing load.

*I don't know whether this is becoming more commonplace.

I think you are right, although reducing the forces used for adequate friction as the load is reduced is becoming fairly common, I think. I am going to be using a simple belt type in my prototype vehicle, and it will be interesting to see what the losses are under various loads.

If variators are implemented in cars one of the things that would follow is the removal of the gas pedal.The system will take care of what regime the engine works in, the driver will only select acceleration.Of course the engine will work at the most optimal regime for the circumstances present.But I'm afraid huge power-plants and generators don't use CVT and they could benefit a lot from such costs cut.I have no idea what's the friction loss in gear teeth but I believe their sphere of application and the fact I know of only one industrial application of CVT is enough to live without that knowledge.

But I still don't know what an "Impulse Variator" is.

For machines it appears to be a system for preventing or smoothing out jerkiness of transferred power.

That's not helpful - even if I didn't already, this thread would already have told me what a variator is. (For those who don't recognize it as an old friend, a mechanical version would once have been called a CVT)

CVT

Talk about slow time-to-market: 500 years after being developed, Leonardo Da Vinci's transmission hub is finally going into production with Ellsworth's The Ride bicycle.
Da Vinci, the Original Industrial Designer (sorry, Raymond Loewy) developed a transmission based on independently rotating spheres. The NuVinci hub offers a smooth transmission of power without the jerky clunks that come with changing gears on today's chain-and-derailleur bicycles. I guess if your beard was three feet long, you'd look for a way to get rid of the chains too.

That bicycle is featured in Popular Science Dec 2007, page 42 & 46. cool stuff.

Chris

I think I want one.

Until I go there and disassemble it to pieces its existence is questionable!

And do you know what this is?

http://www.youtube.com/watch?v=a49d5cJOGQ0

Another perpetual motion device.

Hi Tedi

Check the link .you will find a better answer.

http://www.4engr.com/forum/t279-impulse-variator.html