Build a Baseball Batting Cage: Weight Requirements for Posts

[Serge Voyer]

Hi all,

Not sure if I'm in the right section, but here is my problem:

I would like to build a batting cage that is easy to take apart.

I would use 4 * 10 foot steel post of 1 inch diameter.
The netting weight about 50 lb and would be held with cables .
The posts form a rectangle of 12 feets by 45 feets

How much weight sould i put at the base of each post, in order to hold the net up for kids to hit baseball Inside?

Could you also give me the formula used so i can adjust the weight if i want to use a bigger net?

Thanks in advance,

Serge

 

[Borg]

You would need a ridiculous amount of weight to hold the posts in place. Since you want to be able to take it apart, I would suggest using guy lines to hold the poles in place.

 

[sophiecentaur]

I imagine this needs to be rolled up for transport? That makes it harder but the sections could have diagonals to keep them square. Wide disc shaped concrete feet work ok for the temporary cages they put round some building sites. How about the bases that are used for garden umbrellas (filled with sand)?

 

[Serge Voyer]

Thanks sophiecentaur, i didn't think about the based for umbrellas, that's exactly the idea, but i think they would have to be wider, and also the whole would have to be on one side of the disk so the weight is opposite of the post. I'm thinking about multiple cement disk stack one on top of the other, on one side of the disk a whole the size of my post, and on the other side a whole shape like a handle for easy transport.. This way it's easy to transport for one person.

How much weight would i need at the base of each post do you think?

The guy line is not an option because at home I'm putting the cage in a parking lot.

 

[Borg]

The guy line is not an option because at home I'm putting the cage in a parking lot.

You could attach the guy lines to concrete similar to sophiecentaur's suggestion and you would need less weight. 50 pounds of weight on a 10 foot pole will generate a good amount of torque at the base otherwise. It's easier to counteract the torque from the top.

 

[sophiecentaur]

Braces, rather than guys, would provide some support in tension and in compression. Braces need to be tubular and not strip (I found to my cost when I tried to brace a mast with a wind turbine on it.
I am in UK and have no idea of the size or shape of this thing. How many sides etc?
Presumably you want to keep the feet out of the cage area. I have seen (I think) rectangular concrete bases which would not encroach much. But it wouldn't be hard to cast your own bases (with reinforcement inside, perhaps) and get them just right to suit. Stacking them would mean a lighter load to carry from car to site.
You ask what weight they would need tone. I have no idea but I guess it would have to deal with a large kid running straight into it on occasions. It's not just the bases but the frame members that would count. Galvanised scaffold pole would work better than light weight ally tube but it would make your eyes bulge when moving it about

 

[Borg]

Braces, rather than guys, would provide some support in tension and in compression. Braces need to be tubular and not strip (I found to my cost when I tried to brace a mast with a wind turbine on it.

That reminds me that the whole thing is 45 feet long. You will need more than just poles at the corners or else it will sag a lot in the middle. From this old thread in 2008:

Well it depends upon a lot of stuff, like the properties and temperature of the wire, and the span/sag ratio. The wire will take the shape of the catenary (hyperbolic functions, kind of tough to calculate manually), however, if the sag is relatively small in comparison to the span (say the sag is less than about 10 percent of the span), then the catenary curve is very closely approximated by a parbolic curve using the following equation: T=wl2/(8d), where w is the weight of the wire per unit length, l is the horizontal span between supports, d is the sag, and T is the horizontal tension in the cable. So, given T, l, and w, you can easily calculate d (the sag at the low point of the curve).

 

[Serge Voyer]

You could attach the guy lines to concrete similar to sophiecentaur's suggestion and you would need less weight. 50 pounds of weight on a 10 foot pole will generate a good amount of torque at the base otherwise. It's easier to counteract the torque from the top.

Thanks, i didn't think of that, and i like that it will take less weight at the base.

 

[Borg]

You're welcome. I do think that you will need a minimum of 2 addition poles in the center. Off the top of my head, the net will probably sag 2 to 4 feet in the center of a 45 foot span depending on how much tension you can consistantly apply across that distance.

 

[sophiecentaur]

Did you consider an arched structure? It would be inherently strong (as with polytunnels). You could have several light weight arched spars like a tent. A tube of netting could hang from flexible spars and a struck ball would not hit a spar because the netting would contain it. How much money have you to spend?

 

[Borg]

Did you consider an arched structure? It would be inherently strong (as with polytunnels). You could have several light weight arched spars like a tent. A tube of netting could hang from flexible spars and a struck ball would not hit a spar because the netting would contain it. How much money have you to spend?

I agree. I think that the picture in my first post would be his best option.

 

[sophiecentaur]

I agree. I think that the picture in my first post

Haha what a wally I am. I was working on a smart phone and didn't see the picture.
It looks a perfect idea.
It could be difficult sourcing such large diameter curved tubes at a reasonable price, though. But curves are bound to be the best solution - even if it involved using a lot of hoops with lighter tent spars.

 

[Borg]

The top probably doesn't need to be too strong. The poles could be a combination of standard metal poles with thin, flexible PVC between them. Wouldn't be the prettiest thing but it would be cheap.

 

[OCR]

The top probably doesn't need to be too strong. The poles could be a combination of standard metal poles with thin, flexible PVC between them.

Some tricks on bending PVC...

https://www.youtube.com/results?search_query=how+to+bend+pvc+pipe

I've used the 'sand' method to bend exhaust pipe... it works reasonably well, if you don't go too small on the bend radius...