Bat gate design for 36" culvert

[steven.millett]

Does anyone have any plans for building a decently constructed bat gate for a 36" I.D. lined, plastic culvert? It doesn't have to be bombproof, but should be strong enough to keep local kids from busting in (or damaging) with rocks. Its a vertical culvert.

[caverdan]

You might try and get ahold of a street type sewer lid and metal fixture like the utility company uses. We did this to a vertical cave entrance right next the tourist road leading to a local tour cave. It says Sewer on it and everything. It's been there for years and nobody has bothered it. Seriously.....who would lift a sewer lid looking for a cave opening?

You could also rig a remote control latch release using a choke cable or something along those lines to keep it in place.

[driggs]

You might try and get ahold of a street type sewer lid and metal fixture like the utility company uses. We did this to a vertical cave entrance right next the tourist road leading to a local tour cave. It says Sewer on it and everything. It's been there for years and nobody has bothered it. Seriously.....who would lift a sewer lid looking for a cave opening?

Yeah, good thinkin' buddy, that'll sure keep them stinkin' bats out! Hell, manhole covers are even free if you snatch 'em at night!

[NZcaver]

Does anyone have any plans for building a decently constructed bat gate for a 36" I.D. lined, plastic culvert? It doesn't have to be bombproof, but should be strong enough to keep local kids from busting in (or damaging) with rocks. Its a vertical culvert.

Hi Steve. Is that for the culvert I'm thinking of? The trip I did with you last year?

[caverdan]

Looks like I didn't read the whole post.........hard for bats to fly through a sewer lid....

[MUD]

I was once told by a bat biologist that bats cannot fly vertically in that tight of a circle. Maybe wyandottecaver can answer that. I'd like to know myself.

[batrotter]

Here's a pic of one built at a mine entrance in Indiana:

[steven.millett]

Thanks for the idea batrotter. Any thoughts on this?



I'm thinking 6inch wide, 1/2 inch flat stock
steel, ~30-35ft of it depending on spacing between slots.

It will be locked in place by a 3/4" metal rod. The lock will be
inside the gate and will prevent rod from sliding in one direction.
(The cave wall will prevent from sliding in other (I think, but am not
positive).

Any idea how much this will cost? What slot width is needed for bats
to fly through a vertical slot?

[NZcaver]

Steve, I stumbled across this photo on line and thought you might be interested.

[Anonymous_Coward]

I'm interested to know why you would put a bat gate on a culvert entrance. What did the natural opening look like?

[wyandottecaver]

hmmm dunno how I missed this topic.....

standard spacing for bat gates is 5 3/4 inches. this allows as much flight room as possible while still being small enough to exclude *most* people.

It is also better, but not critical to angle the bars about 45 deg.

A 36" vertical tube certainly isn't what most bats would prefer, but they should also pass it fine. Given its a lined plastic culvert they might even simply climb it. Once home I will dig up pictures I have of a cave with a 36" culvert (metal) that is very near vertical and its gate which hosts plenty of bats.

As for entry design, I would suggest leaving LOTS of clearances for your rod, lock hasp, etc. Mud, rust or cold hands can make finely crafted gates a real pain. Also, rubber lock covers are worth their weight in gold.

[steven.millett]

wyandottecaver ,

I look forward to seeing those pictures. The cave is owned by a state organization which has so far been friendly to cavers and plans to continue to allow us to visit the cave (its a newly discovered cave and access is limited to the people who've helped work it so far). The gate is desired as there is a 30ft vertical culvert at the cave entrance, and a high school, boarding school near by. We want to make a good attempt at preventing a local kid from finding a rope at a hardware store and trying to get into the cave and hurting them self.

Now before all of you start telling me how there are thousands of caves with vertical entrances and no gates let me explain. This is from an area in the northeast where vertical caves are unheard of. Pretty much any cave in this area is completely horizonal and less than 300ft long.

[wyandottecaver]

oops! thanks for reminding me. Once again I'm at work, but this time I'll write myself a note :)

[wyandottecaver]

Here are some pics. probably more gate than you need but you could make it less bombproof Note that the lock is a tab that goes through the sidebar and takes a lock hasp. The sidebars are hollow underneath.

[Tom Gilleland]

We built a culvert gate in the Grandview Mine located in the Grand Canyon. It lies at about 30 degrees, but I think the design would work fine on a vertical shaft. We installed the actual gate down inside the culvert to make it hard to attack. This gate uses work-hardened Manganal steel for the bars. This steel is very strong against hacksaws and battery grinders. Note that a pair of bars slides out together. The removable bars sit in pipe sleeves that are welded to the culvert. A square box of steel encircles the culvert and the fixed bars are welded to this box. We used PUF foam around the outside of the culvert to seal it in place. Stone and dirt cover the foam to protect it from UV deterioration.

The Townsends bats at this site have no problem flying through this gate. I've seen many bat species fly vertically up small mine shafts. I've discussed this with Jason Corbett of Bat Conservation International and he feels that if the bats like the roost enough, many species will have no problem flying vertically through a gate. Many species are very maneuverable in their flight skills, California Leaf Nosed bats can even hover and would have no problem navigating vertical bars. You could test it first by building bar section of the gate out of PVC pipe and see if the bats still use the site. Some fast flying bats like Mexican Freetails probably would not this configuration, nor would a colony that is really big.

Here's a picture of the outside of the culvert:


Here's the inside of the culvert at the gate:


Tom Gilleland
MineGates, Inc.