How do you build an auto mechanical gate

[ns_in_tex]

I am interest in building a mechanical (no power involved) pasture gate.

Maybe something along the lines of this bump gate.

Can anyone provide any information on something like this?

 

[Tevi]

Why not try a 12volt solar powered unit

 

[wroughtn_harv]

Neal you've got a sick mind.

I think that's why I like you. /forums/images/graemlins/grin.gif

It is an interesting concept, the bump gate. It doesn't give much information but I think I can figure it out.

It's easy to make a self closing gate. Offset hinges work like a hose. After all, gravity always works.

So the trick the bump gate has is releasing the latch.

The trick part is the speed you hit the gate. If you hit it going too fast the gate is going to swing open and then come closed before you're through. Too slow and the gate won't open enough to give you time to get through.

The secret is in the hinge. It's sorta like real estate. You make your money in the buy, not the sell. /forums/images/graemlins/grin.gif

Let's say you have a standard old sixteen foot farm gate like they sell at the farm store. And you want it to open and close with your only input being the bumper of your vehicle.

First, your hinge post has to be substantial and plumb. Without that you're relieving your bladder into a stiff north wind with your back facing south.

Your top hinge should be the standard L bolt into the post. Pin facing up. The best thing for the gate side would be Heim joint or rod end bearing.

The bottom hinge is where it gets interesting. What you want is for the pin to be offset just enough to where you're lifting the gate up as you swing it open. Where it gets tricky is with this bumper activation idea it has to lift up going in either direction.

There's already the concept out there in use across the country in chainlink walk gates that have to be self closing like around swimming pools etc.

On the post is bolted a plate. This plate has two parallel slots. In this case, about an inch to an inch and a half apart would be my guess.

On the gate is two pins the same distance apart. Like if you took a tuning fork with three quarter inch tongs and bent them at nineties near the end.

When the gate is pushed the tong or pin on the gate opposite of the push picks up the pivot motion of the gate.

Point here. The top hinge carries the weight. The fit has to be sloppy enough to allow the angle difference between the gate closed and fully open. That's why I recommend the heim joint. You get the flexibility to allow the angle change without losing the smoothness of the pivot motion in the hinge itself. The bottom hinge is just a flexible pivot point.

The bottom pin--slot positioning controls the speed of closing and the length of time the gate is open. Ideally when the gate hits full open there is a minimum gravity influence so the gate hangs there for a short period of time before starting it's downward or closing arc.

The bump arms are attached to a cam operation that activates the gate latch via cable. When you hit the bump arm it moves inwards pulling the latch open the opposite side of the gate.

It's as simple as skinning a dead cat.

What makes it tricky is having the good hinge post and figuring out the speed to hit the gate. Those things make it like trying to figure out how to skin a live cat.

 

[ns_in_tex]

Actually, the first location I want one, electricity is available. I just wanted to keep cost and maintenance down.

I have a electric roll gate at my front entrance, and as anything, it requires repairs.

My thinking, less parts, less cost & less maintenance.

I may have to buy one of the Bump Gate kits to see how it is done. From the pictures, I can figure it all out, except the time delay for the release to close.

 

[bobodu]

I was thinking along the lines of self closing hinges.Say we take a toilet paper roll and cut it in half on a slight diagonal.Hold it upright and give it a twist.The top half will ride up and around.The gates weight will return it back down.Seen breakaway mailbox arms made this way.I be concerned about the critters "worryin" (wroughtnharvs term...which I like very much /forums/images/graemlins/grin.gif) the latch open.Maybe a pull rope or something high enough to bump the roof of the truck?

 

[sneaky_pete]

Bump gates are extremely common in southwest Texas, but I've hardly seen them anywhere else. They would be relatively easy to construct if you've ever seen one in person, but hard to explain how to construct.

There is no latch on the ones I've used, they're held closed by gravity and the weight of the gate. The trick to going through one is to stop with your brush guard just touching the gate, then give your truck enough gas so that the gate is pushed out of your way enough to get through (quickly) but not hard enough so that it hits you in the **** on your way out. If you don't push hard enough, they will come back too soon and knock your outside mirror off or scrape the side of your truck. But you can't hit them at any speed at all; you've got to come to a stop before pushing or you will ruin your truck and/or the gate pretty soon.

 

[OkeeDon]

Seems like the explanations of how to build a bump gate offered above will certainly work, but if I understand them, they are more like push gates than bump gates. Reviewing the Australian gate, including watching their movie, it's a spring operated gate, possibly using something like an overhead garage door spring that is mounted vertically in or on the hinge post. There would have to be something like what Harv described so that the momentum and the spring pulls the gate open, then the weight of the gate returns it to the closed position and rewinds the spring. Their bump bar is also spring loaded, so it pivots enough when hit to release the latch, then resets to the latched position. I got only the briefest glimpse of their delay latch in operation, but it appeared to be a latch that is fighting gravity -- it latches when the gate makes contact, but a counterweight on the other end of the latch fights against the latching position and releases in a couple of moments, allowing the gate to swing shut.

If I'm anywhere close on how it works, it's one of those things that will drive you crazy experimenting with mountings, spring rates, latches, geometry, etc. forever until you get it right. While I'm intrigued by stuff like that, I also don't like re-inventing the wheel, so I'd probably order the kit from Australia and spend more time enjoying it.

It's a neat idea. Here's my question. Such an operator would serve my primary concern of keeping my dogs inside our fence, and would also make it easier for guests, meter readers, propane delivery trucks, fire fighters and other legitimate users to enter the property. But, since anyone could enter the property, it doesn't serve my secondary concern of providing some additional security against intruders.

So, the question is, how much additional security does an electrically activated fence provide? Start from the standpoint that anyone can get into anything if they really want to; someone with a bigfoot truck could simply drive through the swale and over the pasture fence anywhere they like, for example, simply ignoring the gate. But, I'm thinking more about the younger folks who typically are looking for quick, easy targets where they can grab something to pay for their drugs. Do you think the electric gate would be more of a deterrent, or would almost any gate give them enough pause to move on to my gateless neighbors?

 

[ns_in_tex]

Hi Harv,

I think you hit the nail on the head about my sick mind.

I just can not get it to work the way I want it to, & yet it seems to work overtime, creating work for me.

Now the truth is, I seem to want to do whatever it takes, regardless of the amount of work, if I think it will save just a little work, over a long period of time. I think this may be because I am just plain lazy.

I have read your post 3 times, and think I am getting closer to understanding how it works. The lower portion of the hinge is where I am not clear exactly, or have not pictured it in my mind.

I have a brochure on the bump gate & it does not show the hinge, but does say it closes by gravity. It also shows a mecanical latch to catch the gate in the open position, but does not show the release, which says it is time adjustable, for long vehicles, like motor homes, trailers, ETC.

Do you know if the hinges you describe are available, ready made or do I have to construct them?

 

[ns_in_tex]

I am thinking you are describing something like a refrigerator door cam?

 

[ns_in_tex]

Sneaky Pete,

I remember seeing some in west texas, years ago, but did not stop to inspect. (big mistake). I recall at least some had a tall post with a heavy weight hanging off one side on a cable. I presume this may have been for closing and not just a counterbalance.

If this is the case, maybe some of our west texas friends will chime in and explain.