Motor for a Sliding Gate

Will your gate be sliding on the ground? How will you drive it? Gear/chain/belt?

I'd look at remote gate openers.

Openers 4 Less - Offers Gate Remote Controls | Automatic Gate ...

Not an endorsement↑

I will be driving it by gear and yes it will be sliding on the ground forward and backward motion.That means for my gate according to the link I will need a Tr-3 gate opener.

Negative.

The TR-3 operator is for slide left or right gates. For forward and backward operation, select the BR-549.

Doorman, the BR549 has been superseded by the latest model # OU812.

i don't understand why it needs to slide on the ground. would mounting a caster wheel on the end of the gate reduce the power needed?

i think a garage door opener will work. then you will be able to control it with a remote.

The HP of the motor also depends on the speed you want to operate the gate.

Mine is 20 Ft and slides (rolls) on a rail. Works on battery, power assisted.

With toothed wheel and 20 Ft strip.

FAAC (Italian) works already 6 years and has a lot of features. There is a dealer in the USA.

"The HP of the motor also depends on the speed you want to operate the gate."

Well said, it can be moved by 10 HP motor or even by 2 HP motor through appropriate gear train, 'speed is the key'...

Power = rate of doing work.

Work = Force x Distance the force is exerted.

If the gate already is installed, you can use a spring scale or something to measure the maximum force required to operate (slide) it. That gives you the "Force" in the equation above. How far does the gate move? That is the distance. How much time do you want the gate to take to move that distance? That gives you the time and therefore the rate of doing the work. Then you just use the correct units. 1 Hp = 33,000 ft-lbf/minute. There is your force (lbf), distance (ft.) and time (min). You will need a speed reducer and that will add load to the motor. Probably an additional 15% of what you calculate above would work.

You need to work out the Inertia of the Whole Door system to start the motion and reach the required speed. After that, only the friction losses will need to be overcome.

The Starting force will not be the same all the way. It will drop when the door starts to move.

Calculating inertia is good but not as good as measuring actual force required with something like a spring scale. With one measurement you get inertial effects (slow speed device), frictional effects, peak, and running forces. Going with peak makes for a conservative design. Keep it simple - why make it hard?

yes, it is true that you will get the starting force required etc with the scale method. The point is that this should be used to work out the required torque at the driving shaft, and then the motor Power. this is not equal to the force x distance travelled by the door ... as you stated before. that is all.

You're right. Torque is not the same as power. The original question was about how much horsepower was required. My answer addresses that. Torque required is a more a matter of selection of the speed reducer (torque multiplier) ratio and efficiency. This is a very slow moving mechanism which means there will be a high ratio for reduction of speed and therefore a high multiplication of torque. Motor torque must be evaluated but is unlikely to be problem.

If you have the initial Force required to start moving the door to the required speed, and the size of the driving Gear coming out of the reduction gear box (Pitch Diameter), (required to have the required linear speed) you have the Torque. Then W = ∏ x n x T, where n = turns per second of this gear.

You should add the losses in the gearbox etc and some margin.

Good old "STICTION" its called!

Ok first, your gate MUST be setting level. If it is not then you truely are pulling or pushing 300 lbs and will need a big motor.

If the gate is level then your not pulling 300 lbs of weight only a portion of the weght and a small motor like post above will work. The weight is on the supports keep them greased.

Not necessarily 100% true, if for example a Garage door opener is used, it is very useful to have one direction in which gravity pulls, maybe with a start helper of a strong spring.....

Though I have to say that generally I agree with you completely for any system that pushes and pulls, it must be level.....maybe one could adjust the Garage door opener to do both quite easily!

I prefer rails to any other system, easier to level.

I am going through the same thing... But: Mine is a Rolling "Brick Wall" For my Back Gate, & Drive way. I Plain to use a winch, 12 V. & something else to push it. I have 4" V Wheels (8). { My swing out "Wall Gate in Front Works Great!)

AND: Build a couple of Shelves to Mount A 12V. Batt. & Auto.2 Starters; With a belt to sprockets to a Wheel. About, 20:1 Drill Press Drives, for speed reduction. Starters Facing each other For Direction choice.

I have seen many industrial gates with 1/2 hp motors.They were supported on free end by a dual parallel caster wheel, and at the fixed end by idler rollers.A #40 chain ran the length of the gate, and was routed around the drive sprocket of the gear head approximately 2" diameter drive pulley, and a 60 RPM output.There were limit switches at each end to prevent over travel.These gates see very rough service, operating many times per day, and last for years.Some of these gates are over 30 feet long.Length does not seem to make much difference since the load is rolling and level.

The normal failure mode is a limit switch, or lack of lube on chain, or slack chain wrap-up.

Grainger can supply the motor/gear head combo, and since you are an electrician, wiring the reversing control should be no problem.

One of the best reversing controls I have seen in over 40 years of experience is the GE.It is mechanically and electrically interlocked to prevent a short circuit.This in not an endorsement, per se, merely my experience.I am sure there are others of equal quality.

A good way to get a feel for the operation is to go to a local industry and look at their rolling gate drive system.Just tell the guard what you are up to and get permission first.

Hope this helps

Hey thank you guys this is all useful info...

My experience of garage doors I recall an overload feature which reverses if it comes down on your car or kids. I think it would be well worth while having something to prevent this door crushing anything in it's path, perhaps like lift doors with the photo detectors across the gap. Also personally I would have a flashing lamp or audible alarm when this thing is in motion or about to start.

The electrics are pretty standard open/close/stop and limit switches , usually two sets as the damage is substantial if it fails to stop, and then interlocked reversing contactors.

GA for some good ideas.

I personally would also monitor motor current just in case something gets caught, or the limit switch(es) fail. I do believe there are chips for just such a usage, but it's too late at night for me to bother to look. Even if there are none, a low value resistance can be monitored for current flow/voltage drop, to achieve the same....

I saw a guy at my last company machining a 4" piston for opening a gate - using his town water supply. 40PSI on a 4" plate = 500lbs push force. This was back in Oz, where freezing wasn't ever going to be a problem. There was already a 40PSI hydraulic source in his garden by the front gate, all he needed was a 12V low power solenoid system to drive it. At each end of the piston there were two solenoids - push (from the water supply) and vent (to the garden).

His piston was only about 1m long, he was using it for swinging gates. You could possibly make a 15' long piston, or use a 3' long piston and wire ropes through pulleys, so 3' drive @ 500lb force translates to 15' drive at 100lb force. Your gate weighs 300lbs, but I doubt you will need to put 300lbs force against the side of it to move it.

ensure that your gate is placed on rollers that give fair ground clearance. the weight of the gate is only important in identifying the support rollers otherwise no work is done against it, ideally the gate should freelly roll laterally and have no vertical motion.A 1.5 hp induction motor with a reduction gear system or pulley belt drive and a timer should then be perfect.

Sir:

Depending on the quality of your electrical service I would explore using a 12 VDC electric winch. Off road auto suppliers have them, if you need a really big one marine anchor windlasses can be used and they have 24 VDC models

After you have sized the motor, find an equivalent 12VDC electric winch. I live in PR, lose power at least twice a month. My gate weighs in at 200 is on a rail and is a bear to move. Of course, you must remember we lose power mostly when it rains.

Regards,

Jim W