Gas Engine Pull Start Test Machine

pwindz · Mar 29, 2021

I would like to build a gas engine pull start test machine. I envision a electric motor with a large cam or pulley. Pulley diameter would be T=f*d. Force ~ 200 lbs. Torque = motor torque.

I need to control rotation. Depending on pulley dia. might start at 0 degrees and stop at 90 degrees.

Needs to have at least speed control. Big person would pull fast and a little person will pull slow.

Force control would be a plus. To do a programed profile to match a actual pull start would be the best.

Any recommendations on a type of motor needed and control system need?

willxfmr · Mar 29, 2021

With the variables you need to control, I think you are going to need a servo and controller.

drbitboy · Mar 30, 2021

What quantities are to be measured?

Total work for one pull?
Max HP?
Max Force/Torque?
Force/Torque vs. time at ~10ms samples?

I wonder if a water brake would be easier to instrument.

James Mcquade · Mar 30, 2021

i agree with willxfmr. a servo with a rack and pinion system.
there are a lot of details you are leaving out.
minimum / maximum pull distance, do you have to use all the pulling distance, min pull force, max pull force, dwell time between pulls, instant speed requirements and torque for the pull, what happens if the engine starts, a person pulling on the rope is generally linear, not a circular motion like a wheel. these are just a few of the things to think about.
i do not know if this is a personal project or work application, but these items need to be considered. We quoted a system similar to this years ago and these items came up.
james

jaden · Mar 30, 2021

Attached is a suggestion for the pull mechanism. The spacing between the sprockets defines the pull distance. Torque multiplication is in the drive train to the motor. A VFD could provide speed control to the motor.

pwindz · Mar 30, 2021

willxfmr - "With the variables you need to control, I think you are going to need a servo and controller.
__________________

Will a servo have enough torque, power, and speed to pull over a two cylinder 500 to 1000 cc engine?

What kind of controller?

pwindz · Mar 30, 2021

James Mcquade said:
i agree with willxfmr. a servo with a rack and pinion system.
there are a lot of details you are leaving out.
minimum / maximum pull distance, do you have to use all the pulling distance, min pull force, max pull force, dwell time between pulls, instant speed requirements and torque for the pull, what happens if the engine starts, a person pulling on the rope is generally linear, not a circular motion like a wheel. these are just a few of the things to think about.
i do not know if this is a personal project or work application, but these items need to be considered. We quoted a system similar to this years ago and these items came up.
james

James - thanks for the reply. Quick estimate on distance would be 2.5 to 4 feet and distance should be adjustable. Dwell time would also need to be adjustable depending if its a starting tests or a duty cycle test.

The system would need to have reverse to allow re-coil rewind the pull rope.

Do you think a servo will have enough speed, torque and power to pull over a two cylinder 500 to 1000 cc engine? Can you be more specific than just a servo?

willxfmr · Mar 30, 2021

pwindz said:
willxfmr - "With the variables you need to control, I think you are going to need a servo and controller.
__________________

Will a servo have enough torque, power, and speed to pull over a two cylinder 500 to 1000 cc engine?

What kind of controller?

Short answer is yes. Servo motors come in a wide variety of sizes and HP(KW) ratings. The motor and controller are usually a matched pair. For instance you would use an Allen Bradley controller for an Allen Bradley servo. There are exceptions to this, but I usually see them paired by manufacture. For a more detailed answer, you would need to define exactly what you need for speed and torque.

Bubba.

James Mcquade · Mar 30, 2021

i would get with your local distributor and see what he recommends.
then upsize a minimum of 10 hp (my opinion), after all, this is a life cycle machine at times.
use 100% duty factor. stress the max pull force required.
james

saultgeorge · Mar 31, 2021

Hi, my first thought would be a servo drive using a linear motor. Rexroth makes them, I had a look at one on my last job. They are quite powerful and fast. Also very expensive. Without spending too much time, I'm not sure if Rockwell has those or not.
They're like a miniature magnetic powered rocket sled on a track. The track can be made long enough for you to get the distance you need. Reversing is no problem to recoil the start rope.

bright676 · Mar 31, 2021

Why not just get a electric starter from the engine manufacture?

Gas Engine Pull Start Test Machine

pwindz

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James Mcquade

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