what kind of motor do i need?

[berguney]

Hi, i'm building a custom bike, and i want to set up a headlight module which will be able to turn the headlights to an upright position when the ignition switch is on.
i will try to draw the positions i want, you can look to the drawing.
thanks.

View attachment 65110

 

[cr0sh]

By "bike", are you meaning "motorcycle"? If so, then I would suggest a small linear actuator; perhaps something from these guys:

https://www.firgelliauto.com/

 

[berguney]

Yeah, a motorcycle

 

[BioniC187]

The linear actuator from a cars central locking system is fine, you can pick one up from a local scrap yard next to nothing. You also have to have a method of keeping the head light in the up position after it is activated. You don't want to rely on friction to do the trick for this

 

[berguney]

How about using a servo motor? Do you think it works?

 

[jpanhalt]

If you mean a model servo, there are certainly models available with the power you need. Most servos will need continuous power to maintain position, or you could develop a latching system* to retain position and use the servo only for movement.

One exception to that is known as a "gear servo," which has just two positions (up or down). With modern microprocessor controllers for regular servos to duplicate the slow action of full size aircraft landing gear, though, I suspect gear servos may become harder to find.

John

*Just anything over center should work. Check the landing gear designs for model aircraft. You probably want the default/rest position to be up and the servo moves the headlight down to "latch."

 

[cr0sh]

How about using a servo motor? Do you think it works?

Believe me, I thought about a servo when I answered your question. The reasons why I thought a *quality* linear actuator would be better were several:

Servos are generally "back-drivable" when the PPM signal and power are removed. Most linear actuators can't be back-driven, unless explicitly designed for it.

Model servos are sturdy, but they are not generally designed for use in an "automotive"-type situation; a quality linear actuator can be much more suitable in such an application (heat, exposure, material strength, etc).

Servos need to have a specific PPM pulse train used to set the position of the servo, which means more complex circuitry to control it. For a linear actuator, you can simple purchase one with "end-stop" switches, which cut the power off when these end points are reached. You only need to reverse the power connections (h-bridge) using a switch or relay to change the motor direction. Note, though, that not all linear actuators have this option, plus you would need to properly design your mechanical interface so that the end stops correspond to the fully up and down positions of the headlight. If this is not possibly, then you would need to get a linear actuator with a feedback system (which is typically some kind of optical or mechanical pulse system, or a feedback potentiometer to measure position); in that situation, the linear actuator becomes -more- difficult to control than the servo, because you have to build the feedback circuitry yourself which is already a part of the servo.

Here's the thing, though, that you need to think carefully about: While such a headlight would look cool in operation on a motorbike, ultimately the headlight is there for safety, especially at night. Should the mechanism fail while you are riding in a dark area (perhaps at high speed), the light may reposition to the "down" position - causing a potentially very unsafe situation. Whatever option you choose, you need to take this into account, and take all steps to prevent this from occurring.

My main reason for the selection of a linear actuator was that I was mainly concerned about the simplest and most robust mountable actuator that could get the job done, that would be the least likely to fail, even if power was removed.