Spring for mail box post

[wbrian63]

First - not interested in any store-bought solutions - I want to fab my own fix - thanks.

The elderly couple that lives across the street is just about at the point where someone needs to hide the keys to the truck.... For the 2nd time in as many months, they've backed into our mailbox.

The current post is 2x2x1/4" tube fashioned in an "L" shape. That places the post away from the curb about 12" while providing the proper height and offset for the postal service.

I'm trying to come up with something that will allow the post to give. Right now, the mailbox takes the brunt of the force and deforms while the post pushes away.

I'm thinking the easiest thing is a spring of some sort that will allow the post to give regardless of what direction the of impact.

I've looked at online spring sellers and I have no idea how to calculate how big a spring I need.

Looks to me like I need an expansion spring, but calculating the bending force is beyond me. I basically need the mailbox to be stiff enough for the normal activity of the postal service (opening and closing the door, inserting mail and packages, etc) to not cause the mailbox to move, but when the Mr or Mrs once again makes contact the mailbox will move away without causing more damage to the box.

I don't much care if there's damage to the tailgate of the truck, but I'll probably fashion a bumper covered with rubber hose to the front to make it contact safe.

The post is about 30" tall from the ground to the point where the horizontal bar attaches. Ideally, I'll cut the post and weld the spring in place a couple of inches above ground level.

Greatly appreciate any suggestions.

 

[Kevin54]

This PDF shows that they use a torsion spring http://www.flexpostinc.com/wp-content/uploads/2014/01/Concrete_Model_Assembly.pdf

http://www.flexpostinc.com/store/products/flex-mailbox/

http://flexiblemailboxpost.com/details.aspx

 

[MP&C]

Metalhead has some coil springs he's trying to find a use for....


http://www.garagejournal.com/forum/showthread.php?t=262599


As another option, I've seen the sleeve over a post that allows it to pivot to the side, an angular taper persuades it where to stop. Would something like that help, or are they backing straight into it? Perhaps some Mad Max armor welded around the mail box


Swing away version:

 

[kmkalf]

What about going to a salvage yard and get a coil spring out if a light duty vehicle or from a strut assembly. Unsure if that would work since they are made for vertical force and not horizontal. My grandma has a 4" pipe that is concreted into the ground and the tube is full of concrete and has taken plenty of beatings without damage.

 

[404]

This solution gets the post out of the way completely.

http://midlifeinmaine.wordpress.com/tag/snowplow-proof-mailbox/

Not store bought!



Regards,
404

 

[steel 35]

First thought, old garage door spring.

 

[wbrian63]

I'd love to create a "I dare you" post - but that won't make for good neighbors...

They're really nice people and paid for the replacement mail box the last time this happened. I really would prefer to avoid having the conversation again - it's embarrasing for them and I don't want to put them through it.

Kevin - that solution is (was) exactly what I'm looking for. They even sell the spring as a separate part for - eek - $74.99. I was willing to pay that, the price is in-line with my other searches for a extension spring. However, they want $30.00 to ship it!!!! The damn thing will probably fit in a "if it fits it ships" box from the USPS for goodness sake!

That's just not right.

404 - nice solution - but I don't live in rural Maine - I live in a neighborhood in the 4th largest city in the US. Won't fly with the (yes - I've got one too) HOA...

MP&C - I saw the thread from Metalhead - that's what made me think of it. I've also seen those setups like you describe, but they're more tailored to snowplow abuse. The neighbors are hitting it at about a 15-degree angle or less. That's too narrow to allow for a swivel-away solution. I had thought about a rotation setup where the horizontal arm meets the post, easy enough to do with a couple pieces of plate, a bolt and an axial bearing. Could even fashion a return spring with a stop to allow clockwise rotation (the direction of the impact), but again, the angle they approach from is still going to generate too much push at the wrong angle to have something like this work.

KMKALF - 1st - great looking Corgi. 2nd - that's an option, but I think the solution here lies with an expansion spring - one where the coils touch when the spring is at rest.

Keep 'em coming - I appreciate any an all suggestions.

 

[wbrian63]

First thought, old garage door spring.

Thought about that too, but then I saw the various online sources that use a coil spring and the coils on a garage door spring would be way too thin.

 

[jimgood]

I think the garage door spring is a good bet. Pipe in the ground with half of the spring in it. Separate pipe above ground with half the spring in it. Joint a few inches above ground level. Make the upper pipe bigger than the lower one to keep rain out.

Not sure how you keep them from killing the mailbox though. They're just going to push it all the way down until hits the ground. But at least you won't have to replace the post.

 

[zkling]

If they keep hitting it in the same direction each time, how about a hinge and a shear pin setup?

One of those flexible parking/traffic sign posts?

 

[RECox286]

Relocate your mailbox ?

Any light duty (car) front end suspension spring will work for

you. Springs are not really good for welding to, but as long as

your kids won't be using it for a "ride" you won't have any

trouble. If the welds break, just reweld.

Uncle Bob

 

[paranoid56]

i think you are going about this wrong. I would make it stupid over built and strong. say, 5" .25wall pipe buried 5ft into the ground filled with concrete. make a exo steel box for the mail box, paint it all to match and you would be good for years.

 

[mtwaterguy]

i think you are going about this wrong. I would make it stupid over built and strong. say, 5" .25wall pipe buried 5ft into the ground filled with concrete. make a exo steel box for the mail box, paint it all to match and you would be good for years.

Try reading post#1 and post #7. I'd say again, but from your post it's certain you haven't read them yet.

 

[yhprum]

Put a motion sensor alarm on the mailbox so they know when they bump it!\

 

[nti06]

What about the holder for the pressure washer wand at the coin op car wash?

 

[paranoid56]

Try reading post#1 and post #7. I'd say again, but from your post it's certain you haven't read them yet.

i did, and hes trying to shift damage from his mail box to it just folding over. but why not just shift the damage to the people backing into it? this will stop people from doing it, with a spring, they are just going to keep backing into it.

 

[Farmall450]

What about going to a salvage yard and get a coil spring out if a light duty vehicle or from a strut assembly. Unsure if that would work since they are made for vertical force and not horizontal. My grandma has a 4" pipe that is concreted into the ground and the tube is full of concrete and has taken plenty of beatings without damage.

Sadly illegal for me at least.

 

[Kevin54]

i think you are going about this wrong. I would make it stupid over built and strong. say, 5" .25wall pipe buried 5ft into the ground filled with concrete. make a exo steel box for the mail box, paint it all to match and you would be good for years.

i did, and hes trying to shift damage from his mail box to it just folding over. but why not just shift the damage to the people backing into it? this will stop people from doing it, with a spring, they are just going to keep backing into it.

He said they are elderly and they are good neighbors.

Also, a homeowner can be held liable if a mailbox would injure someone. This isn't so much in the OP's situation, but for some rural areas.

If it were me, I would design something with a shear pin, so it would break off, then you just have to put another pin in, OR the spring if you can find one. Hopefully if they are as old as you say they are, and their driving habits are that bad, possibly in the next year or so, they will fail their drivers license renewal exam.

 

[Farmall450]

He said they are elderly and they are good neighbors.

Also, a homeowner can be held liable if a mailbox would injure someone. This isn't so much in the OP's situation, but for some rural areas.

If it were me, I would design something with a shear pin, so it would break off, then you just have to put another pin in, OR the spring if you can find one. Hopefully if they are as old as you say they are, and their driving habits are that bad, possibly in the next year or so, they will fail their drivers license renewal exam.

Wouldn't you think his box will still get trashed before the pin shears?
Unless you get the HD ones they show a semi parked on, I'm not sure the pin would break in time.

 

[2ndGearRubber]

Weld two car springs together. I had a neighbor with a similar issue, as their mailbox was at the apex of a particularly slippery winter corner. Eventually after the proof of concept winter passed, they planted some shrubs around it to make it pretty and functional. Although I always enjoyed the look of the matte black coils.

Then weld a steel plate to the top, with small screws holding the mailbox on. Just in case the box would be replaced in the future. 2 front coils from a truck may meet the desired height.




But beware, if you bend it all the way, and let go of it - those springs have some *** behind them!

 

[kerrynzl]

I recommend using a couple of Subaru springs

 

[zkling]

Wouldn't you think his box will still get trashed before the pin shears?
Unless you get the HD ones they show a semi parked on, I'm not sure the pin would break in time.

You design it so the shear pin fails before the device is destroyed. It's a mechanical fuse. It would be real simple in this application and probably safer. A spring stiff enough to prevent the box from blowing around can store a good amount of energy upon release.

 

[EdT]

Here's a crazy thought. Let's assume that you have the government issue 4 x 4 wooden mailbox post just for purposes of discussion. Set it into the ground however you normally do and cut it off just above ground level. Put it back together with a hinge on the side opposite where your neighbors bump into it. Get a couple of the strongest rare earth magnets you can find and put one in each end of the post at the joint such that the magnets are attracted to one another. I have some magnets that will pull around 70# and they are only about an inch in diameter. The way magnets work, as soon as they move a little bit, the force holding them together drops off dramatically and the post with the mailbox attached will fall guided by the hinge. You would have to make an arrangement at the top of the post so that the back of the box doesn't get crushed when it falls. There are several vendors of rare earth magnets on the internet, You can find them as fast as I can. Lee Valley tool is one that comes to mind. They also sell the "cans" that go over one end of the magnet and significantly increase the pull. Just crazy enough it might work.

 

[Yamaguy]

Here's a crazy thought. Let's assume that you have the government issue 4 x 4 wooden mailbox post just for purposes of discussion. Set it into the ground however you normally do and cut it off just above ground level. Put it back together with a hinge on the side opposite where your neighbors bump into it. Get a couple of the strongest rare earth magnets you can find and put one in each end of the post at the joint such that the magnets are attracted to one another. I have some magnets that will pull around 70# and they are only about an inch in diameter. The way magnets work, as soon as they move a little bit, the force holding them together drops off dramatically and the post with the mailbox attached will fall guided by the hinge. You would have to make an arrangement at the top of the post so that the back of the box doesn't get crushed when it falls. There are several vendors of rare earth magnets on the internet, You can find them as fast as I can. Lee Valley tool is one that comes to mind. They also sell the "cans" that go over one end of the magnet and significantly increase the pull. Just crazy enough it might work.

The best answer I have seen yet!!

 

[wbrian63]

He said they are elderly and they are good neighbors.

Also, a homeowner can be held liable if a mailbox would injure someone. This isn't so much in the OP's situation, but for some rural areas.

If it were me, I would design something with a shear pin, so it would break off, then you just have to put another pin in, OR the spring if you can find one. Hopefully if they are as old as you say they are, and their driving habits are that bad, possibly in the next year or so, they will fail their drivers license renewal exam.

I want to keep my neighbors happy - they're good folks. I have other neighbors whom I wouldn't pi$$ on to put them out if they were on fire...

Don't want to cause more damage to their vehicle - just want to prevent having to replace the mailbox every so often.

I've contacted one of the vendors that has the spring for $74.99 to ask why they want so much for shipping - we'll see what they say.

I have thought about a hinge on the back of the post with a stout spring down the front bridging the hinge line, but that will only work well with a direct impact at 90 degrees to the hinge pin. Anything much off center will just end up tweaking the hinge - at least that's my opinion.

As for damage to the mailbox itself - it is indeed the weak link in the chain. However, I plan to fashion a "front bumper" out of some 1/2" rod formed into a gentle curve to allow that to be the first point of impact. Cover this with some 1/2" automotive heater hose will make it people-safe and non-marring.

Thanks for the responses to this point. I do appreciate all the feedback.

 

[sean Buick 76]

Maybe have a 1 inch wood dowel between the upper and lower sections of the 4x4... If they hit it the dowel will break off and its an easy fix to put a new dowel in.... And to keep the box its self safe raise it higher out of the line of fire.

 

[petawawarace]

Put a spring in the base so that it moves slightly. Then wire in a switch so that as soon as it starts to move it sets off a large air horn. Just hope they don't have a heart attack!!!

 

[wbrian63]

I ordered this spring:
http://www.flexpostinc.com/store/replacement-parts/replacement-spring-kit/

I find as I get older that I have to balance available time with the desire to "fab from scratch". My original restriction on "no store bought" meant that I didn't want to replace my existing post/box with a turn-key solution.

This spring, with a little fab work for brackets, can be adapted to my current setup.

Thanks Kevin54 for the lead.

BTW - this is (from my limited experience) a good company to work with. When I originally tried to order from them, their website was going to add $30 for freight. I have a real problem with "perceived" inflated freight charges, so I eMailed their sales dept and asked why the freight was so high.

They responded in about an hour with an explanation that the website applied an average freight amount to cover all potential destinations. If I sent them my zip code, they'd be happy to quote actual freight costs.

The spring weighs 6 pounds, and the revised freight costs are now $13.00 - fair enough.

I sent them shipping and billing addresses and they called me for the CC # - bing, bang, boom - the spring is in the mail...

I'll post some pictures when I get the spring installed.

Thanks for all the help. GJ members are top-notch.

 

[JieselDeep]

Late to the party, but why not just bolt your post to a pice of 2x4 in an inverted T. Nail the T to another piece of wood secured to the ground with Simpson clips of some sort. Nails will pull out easily enough when backed into, especially with the lever action of the post...pull the bent ones and hammer in a couple more nails and you're good to go. No damage to mailbox, or car, but a slight guilt trip when they see you out there fixing it.