A simple electronic RPM based actuator?
 

I've been churning a secret squirrel idea in my head for a couple weeks now. I need some sort of actuator to make my idea work though. I need something that can adjust angle (spin) or length based on RPM. As an example, VVT adjusts angle based on RPM - but it's much too complicated for my particular use. Are there any examples of simple motors/actuators/etc that I can use and control with an aftermarket ECU? It's probably out there plain as day, but I can't think of anything.

Thanks!

so you need a variable output instead of just an on off at a certian rpm? You may be able to build some circuit based on the pwm of the injector channel. im pretty sure the water meth circuit works off of pwm based on rpm in megasquirt.

yes, on/off would make it pointless

I'm running a hydra, so I can run it from it's own PWM.

Stepper motor w/ driver circuit?
(G)

never heard of a stepper motor, but looked it up, and it could very well work. Also gave me the idea to use some sort of servo...I've got a very nice RC car - why didn't i think of that!?!?...

So I wiki'd "servo"...

RC servos are composed of an electric motor mechanically linked to a potentiometer. Pulse-width modulation (PWM) signals sent to the servo are translated into position commands by electronics inside the servo. When the servo is commanded to rotate, the motor is powered until the potentiometer reaches the value corresponding to the commanded position.

Now I'm trying to find a larger than RC, high torque servo!!

How much torque do you need? RC servos are made pretty big.
http://www3.towerhobbies.com/cgi-bin...&I=LXGLN4&P=ML
152 oz/in

http://www3.towerhobbies.com/cgi-bin...?&I=LXAAD4&P=7
292 oz/in

292 oz/in = 1.52 ft-lbs?

i was thinking 10 ft/lbs or so would be fantastic, maybe overkill, but not sure yet.

i keep looking, and it seems like servo motors go from RC applications at under $100 to industrial size/industrial cost systems, which are ridiculously oversized. Seems like they would make something appropriate for robotics, but having trouble finding it. I'll keep looking tomorrow, but really have to go to bed now

Why not use a solenoid and Hydra's electronic boost control? I haven't used Hydra, but it's pretty standard protocol to allow boost per rpm.

These guys rock: http://servocity.com/

Specifically, they have big linear servos (up to 115 lbs thrust): http://servocity.com/html/linear_servos.html
and massive, mega-torque rotational servos: http://servocity.com/html/robotzone_servos.html

4,995 in/oz enough for you? (That's 26 ft/lbs.)

http://servocity.com/assets/images/S...n_outline2.jpg


Also various servo controllers:
http://servocity.com/html/servo_controllers.html
http://servocity.com/html/dual_servo_driver.html



Just make sure that your ECU will generate a variable duty-cycle PWM signal at a fixed frequency, and you're golden.

You, Sir, are my hero

What are you trying to do? Make an adjustable rear wing?

adjustable length intake manifold.....

interesting

I've got 2 designs floating around in my head with the idea of maximizing helmholtz resonance across the entire RPM range by adjusting the length of the runners as engine speed varies.

I wish I had an ME degree

I wish I had a machine shop

I wish I had welding experience

Trombone

Thats 1 of the 2

I know...thats why I went back to school to be a machinist.Now I have 2 out of the 3 and I know about30 people with the 3rd.Good luck with the design...thata what I thought you were going to build.
(G)

Depending on what you are doing maybe you could retrofit components from a variable length runner setup from a bike, like a Yamaha R6.
http://www.sportrider.com/bikes/146_.../photo_02.html
I'll bet that it would be really expensive to get a used one though since that particular feature has not been out for long. Sportbike tech wars, gotta love it.

My best friend and I track motorcycles, we learned about that system when they were coming out with it. It's a fantastic concept, and achieves a similar thing to what the 99-00 VICS achieves by changing the dynamics of the resonance chamber to accomodate two seperate focused RPM ranges (although I suspect the YZF does a MUCH better job at it.) Ideally, I would like to be able to tune such that the intake runner length is "infinitely" adjustable between the maximum length (Idle) and minimum length (8k rpms) so that at any given RPM, the intake runners are tuned for that engine speed.

On our honda outboard motors BF225A 4 strokes they have a dual stage intake manifold. It works off a vacuum pot, Changes the intake from long runner to open chamber as the rpms increase. I believe the engine is a v6 originally from a honda CRV. They also have VTEC. I think somewhere online honda has a video describing this. Dunno if this helps but it was very interesting when I went to school for them.

I worked a bit with helmholtz resonance at my summer ME internship. cool stuff.

Looks like BMW has already invented/proven the theory with something called "DIVA"

I feel like I should design some sorta system like this for our fsae car... keep us updated.

Anyone have any technical information regarding best dimensions for the intake runners before I do the math and "over engineer" (i use the term lightly, because the end result will likely be crude at best :D ) the range of runner lengths?

If I remember correctly, the Mazda 787B had adjustiable length velocity stacks too, and they used the headlight motors from the same year RX-7 to move them. Aparently they were tough enough to survive 24 hrs and win
Le Mans in 1991 on an engine that redlined a bit higher then ours

Im sure they were tired into RPM somehow, not sure exactly how they worked though, if different pulsewidths would cause them to extend only so far or what ever, and im sure that they were geared so they would go from max to min position quickly... the headlights on mine move really quick, so i can see them extending and retracting the intake stacks faster then you reving it from idle to readline in nuetral

Theirs seems to be made of a FRP or some other composite material... probobly good so it does not heat soak i guess

Could probobly get more info from rx7club about the specifics

http://www.rx7.net.nz/r26b-2.jpg

That is very cool!

Just saw a neat article about this.

Porsche is using some form of variable length intake on one of their turbo cars. The intent is a little different though. Typically, like on the 787B, the intent is to use the resonance to compress the air into the cylinder.

Well, this creates excess heat.

So what Porsche is doing, is while not in boost (or in low boost, not sure), their manifold acts like normal and helps compress the air into the cylinders. Then as boost pressure builds, the harmonic tuning changes such that the manifold causes the air to expand. They're making up for the lost charge pressure with additional boost and allowing the intercooler to do its job. Just avoiding the addition heat generated by harmonic resonance compression.

Neat stuff....
--Alex

Dlaitini, thats fantastic! I just dont know how well it would fit into our engine bays :P

They are compensating for heat caused by harmonic tuning? It sounds like these guys are running on the ragged edge! I'm not sure it would be a good idea for porsche to put this into production cars, but good on them for engineering to such an exacting requirement!

Yeah that is what I was thinking. That has to be well into diminishing returns territory and not that important on a street car. That is the kind of design detail that makes high-end racing engines so interesting.

for some reason, the only way packing wise on a miata, i see an intake shaped like a trombone.

The runners will increase and decrease their lenght, and if also tied into an Plenum, can also use forced induction if the tolerances are close enough on the sliding part... or if enough air is pushed in to overpower what leaks, lol

I'm currently considering an idea which involves a rotating cylinder to increase/decrease runner length. An rotating inner cylinder would be completely encased in a non-moving outer cylinder with the exception of a seal where the servo connects to the inner cylinder assembly. The seal would look similar to the current VICS actuator seal.

I just need a better way to prototype it than what I'm currently doing.