Best angle of the rail for a Garage Door Opener


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Thread Number: 62277 / Tag: Other Home Products or Autos
Best angle of the rail for a Garage Door Opener

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Post# 848621 10/30/2015 at 13:15 (3,094 days old) by mb1280 ()
Checkrate/Likes I've been trying to alleviate some loudness in a garage door, and this seems to be an answer, but I don't know exactly why. From the Manual, Chamberlain LiftMaster 3280 - page 11 . . . i.imgur.com/Mqg4J1s.gif... A 2x4 laid flat is convenient for setting an ideal door-to-rail distance. The top of the door should be level with the top of the motor unit. Do not position the opener more than 4" (10 cm) above this point. This page has a link to the complete door opener manual . . . the LiftMaster� Model 3280 . . . please see page 11 chamberlain.custhelp.com/app/answ... * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Question: What physics is going on here, with the angle of the garage door opener rail? . . . What are the options for the rail? 1.) angled down - as seen in the manual, this is how you want it, but specifically, why? 2.) horizontal - I think this would make it harder to pull, than if angled down, and wear out the motor faster? 3.) angled up - I think this would make it harder to pull, than if angled down, and wear out the motor faster? Some explanations that I've gotten: * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Your opener appears to be installed almost level with the garage door, rather than angled backward. That will cause the jerky/noisy operation when you close the door. Go to your local home improvement store, and buy some angle iron, and lower the power head. (See the section in your manual titled "position the opener") When the door is fully opened, the opener rail should be max 2" above the edge of the top section. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Friction - and the fact that when you reduce the normal force on the rollers / rods, yes the engine works harder but the friction is reduced. It's called the normal force. Ff=uFN Force friction = coefficient of friction x Force normal www.mrfizzix.com/weightlifting/fr... The greater the angle, the less the normal force, and thus the less friction, and less noise, unless you have a loud motor. When angled down, the normal force is reduced, which in turn reduces the friction, and sound. The equation above shows that the friction is reduced. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Inclined Plane . . . en.wikipedia.org/wiki/Inclined_pl... I wonder why they don't say to put the header bracket 1 foot higher than where the motor will be, maybe a greater angle would be a benefit. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Pulley . . . en.wikipedia.org/wiki/Pulley... * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * I think it has to do with Force, friction, and the pulley. Springs are also involved. I don't think the Inclined Plane has anything to do with it. That's about moving an object from lower to higher, or the reverse. Another question would be, how do you determine the best angle for the belt or chain / rail? Or, is there a range that works? And why? * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * If being a pulley is the best explanation, why, exactly, does angling it down make it work better than, say, having the force pull parallel to the ground? It's a 1/2 horsepower motor, so the Force equals 1/2 horsepower. What equation uses Force, and an angle, to determine . . . ? . . . what . . . work? . . . Is that it? This is not an easy question to answer. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - I wonder if this page could do an example with a garage door: www.physicsclassroom.com/class/en... "In a previous part of Lesson 1, work was described as taking place when a force acts upon an object to cause a displacement. When a force acts to cause an object to be displaced, three quantities must be known in order to calculate the work. Those three quantities are force, displacement and the angle between the force and the displacement. The work is subsequently calculated as force�displacement�cosine(theta) where theta is the angle between the force and the displacement vectors. In this part of Lesson 1, the concepts and mathematics of work will be applied in order to analyze a variety of physical situations." * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * On my to do list: 1.) measure height, floor to ceiling 2.) how far down is the rail on each end? 3.) how long is the rail? 4.) it's a 1/2 HP motor See if I can plug these values into the Work formula, with the angle (cosine) What's the difference in Work done at the current angle, horizontal, or in between? See if someone else can verify what I come up with. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Post# 848626 , Reply# 1 10/30/2015 at 13:43 (3,094 days old) by kb0nes (Burnsville, MN)
Checkrate/Likes I've never seen or installed an opener where the rail wasn't horizontal or basically perpendicular with the door. While is is possible that small changes in the angle of the rail may alter the forces slightly, I think any variation will be insignificant. Where did this advise come from? In any case I can't imagine that altering the rail angle will change noise levels. For that first and foremost insure that the tracks, rollers and hinges are installed tightly, aligned correctly and well lubricated. Make sure that the opener itself is securely fastened also. If you have an all metal door without insulation it is bound to be noisy, the door is just a big sound board. Damping the panels is about the only way to quiet that down. Pull the manual release and run the door up and down by hand, is it quiet then?

Post# 848798 , Reply# 2 10/31/2015 at 07:18 (3,093 days old) by arbilab (Ft Worth TX (Ridglea))
Checkrate/Likes If the noise does not vary as the door travels between full open and full close, the noise is not due to motor load and cannot be reduced by changes to installation parameters. Certain of these machines are inherently noisy and nothing can be done to abate the noise short of replacement with a different design. Mine was noisier than I thought it should be yet it always worked perfectly and never developed issues. I had the contractor replace the entire door, cable and spring assembly when they installed the opener. The 'growl' when operating never changed. It's been 8 years since I lost my house so I can't claim to remember exactly, but I believe the test of proper spring tension was to disconnect the opener mechanically, open the door halfway and it should stay there. If it falls from halfway the spring is too weak and if it raises from halfway the spring is too strong. To the best of my understanding proper spring tension is the prime determinant of motor load. And as above, noise is not a reliable measure of system balance. Try this: Pull the decoupler and operate the opener. If it's as noisy as it was when it was actually driving the door there is nothing you can do to change that.

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