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Author Topic: Blind concrete bolts  (Read 2619 times)
kwood
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« on: June 29, 2008, 04:50:50 PM »

Has anyone used blind bolts such as concrete anchors for mounting seats or something?  I saw some at Lowes in 1/2 inch with great load capacity.  I would be putting these through laminate floor and two layers of 1/2 inch plywood.  Any thoughts? 

Thanks,
Kevin
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Melbo
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« Reply #1 on: June 29, 2008, 05:10:35 PM »

Depending on the style they may but remember that wood will compress and concrete won't

Red heads will pull out of wood but not concrete

Other styles may work better.

Melbo
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« Reply #2 on: June 29, 2008, 05:47:53 PM »

I have used them a lot for mounting sign cabinets to brick buildings. The loading in that application are mostly shear, people also use them for bolting down stationary tools.

Can you get underneath? If it was a seat holding me, I'd prefer to drill and tap a hole in some plate and weld it to the structure.
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« Reply #3 on: June 29, 2008, 06:14:20 PM »

I am just looking at all options before taking out the wheel wells.  That looks like quite a project.
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« Reply #4 on: June 29, 2008, 06:31:22 PM »

Can you use a toggle bolt.  They are available (but maybe hard to find) in 3/8".  Not the best solution in terms of strength but maybe an alternative for you.
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« Reply #5 on: June 29, 2008, 06:34:54 PM »

Personally, before I would dismantle the bus, I would use the largest lag screw possible! I mean one day those seats may have to come out and then what, you dismantle again! Better you than me! My floor has 2 layers of 3/4 inch plywood and I defy anyone to pull my buddy seat out and IF a collision occurs bad enough to remove MY seat the way it's in, I won't be around to worry about it anyway!
You will learn that a LOT of your ideas are good but will most definitely get shot down on these boards because there is always a better way. Hardly anyone will first say, your idea is good!
Just do it and forget about it! If you listen to each and everything everyone says, you'll never finish your project due to so much doubt!
Heck I've done so many things I was told wouldn't work, it's a wonder my bus even runs but I AM using mine and enjoying it where others are still struggling with "ideas"!

BS
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Cary and Don
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« Reply #6 on: June 29, 2008, 07:17:22 PM »

We did a compromise on this.  We used big bolts through the floor and really big washers on the back side.  The driver seat bolted through into the compartment under it.  The passenger seat bolted through two layers of plywood flooring.  The seat belts were bolted through different holes.  That makes for ten bolts holding each person and their seat in place.  That should be enough that they aren't going to pull through the floor.  If the floor comes up, that could be another story.

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« Reply #7 on: June 29, 2008, 07:30:36 PM »

Wood is fine to bolt to if you spread the load out and the member you bolt to is thick enough. If you are happy with the washers then great. Just remember wood will shrink over time and you may have to retorque the bolts. Lots of boats and airplanes have been built almost entirely of wood and seats and belts are attached with no problem. Of coarse steel is always the stronger choice but sometimes it just is not a practical choice. I repaired a seat for a competition aerobatic pilot that was an integral part of the 4130 steel fuselage frame "it failed during a snap roll" I beefed it up with gussets and finger doublers after re welding new tubes in place. And this was designed by engineers.

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Don4107
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« Reply #8 on: June 29, 2008, 09:51:25 PM »

"I mean one day those seats may have to come out and then what, you dismantle again!"

That is one of the reasons you build a backup plate that is threaded or has captured nuts.  There are many places you can compromise in building a bus.  The seat/seat belt anchors that are keeping your arsh or more importantly your unsuspecting passenger(s) from being tossed through the windshield is not one of them.  Lag bolts? Give me some grade 8s with enough backup that it has to tear half the floor out with it!

Good luck
Don 4107
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kyle4501
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« Reply #9 on: June 30, 2008, 04:46:16 AM »

I'm with Don on this one.

Yeah, the chances of being involved in a collision may be low, but I didn't plan on someone running a stop sign either.

Stuff happens & I'd rather not have to worry about my seat coming loose & the passangers becoming projectiles while still in their seats.  Shocked

I guess some would rather put in extra effort for their safety. That's why we are building our own.  Grin
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« Reply #10 on: June 30, 2008, 06:13:44 AM »

I think backup washers about 1 1/2" in diameter with those grade 8 sae thread bolts would do the trick, I wouldn't want a member of the family or a friend to end up through the windshield!
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« Reply #11 on: June 30, 2008, 08:10:07 AM »

As has been pointed out, this is not an area to take chances on.  The front end of a bus is a kill zone anyway in serious wrecks.  But even in lesser collisions, if the passenger flies through the window either because they weren't belted in or their seat broke loose, their chances of death or permanent injuries greatly increases.

What about making a steel or thick plywood (better yet, hardwood plywood) mounting plate nearly the same size as the foot print of the seat?  Create proper mounts on it for the seat to mount to (removable).  If using steel this could be weldnuts or bolts coming up through it and welded in place or secured with a nut to create mounting studs (use grade 8 hardware).  If using plywood for the base plate, use very large washers top and bottom, then on top put a lock washer and a nut tightened down tight.  Size the bolts so that this leaves enough sticking up to mount the seat to (I would use grade 8 hardware for this).

Make any necessary holes/recesses in the flooring to allow for bolts/nuts protruding from the mounting plate.  Attach the mounting plate (steel or hardwood) to the floor using a lot of large toggle bolts (i.e. every 4" around the perimeter of the mounting plate, plus a few placed around the interior of it) and a healthy application of heavy duty construction adhesive.  This is assuming you have replaced the flooring in that area and it is very well mounted to the floor framing.  If you haven't done that, you should.

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luvrbus
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« Reply #12 on: June 30, 2008, 09:03:13 AM »

kwood, read the pullout testing on lag screws available at any fastener supply they don,t even test on plywood and the lag screws are 6 inches and longer in Douglas pine tested on end grain and side grain. And you can not use a anchor bolt in 2" concrete and have any pullout strength to it
« Last Edit: June 30, 2008, 09:11:19 AM by luvrbus » Logged
Dreamscape
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« Reply #13 on: June 30, 2008, 10:14:22 AM »

As was said many times. Do Not use Lag Screws, they will pull out!

All bolts are rated on shear strength. Us a Gr 8 bolt of sufficiant thickness with back up plates or very large washers. I like the plate idea better because you can drill the proper hole for the size of bolt. For a 1/2" bolt I would size the plate to no smaller than 1/4" thick and 6" square. You could even weld the plate to a framing member to add support, if one is available. Also double nut, nyloc or use loctite. Concrete anchors such as red heads will pull out. The best way to anchor in concrete is using anchors that are used with epoxy, that will never pull out.

FWIW,  Wink

Paul
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kwood
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« Reply #14 on: June 30, 2008, 02:24:44 PM »

I like the idea of the mounting plate.  Grade 8 bolts could be threaded through a taped hole up through the seat.  The bolt heads could be counter sunk into the floor.  The problem still remains on how to anchor the plate to the floor as I am having trouble getting to the under side of the floor.

Kevin
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luvrbus
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« Reply #15 on: June 30, 2008, 02:36:36 PM »

Kwood I am not a MCI person but can you not reach the bolts from the fuel door the MCI 8 I owned had a small stainless open box that could be removed to reach the bolts
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Blacksheep
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« Reply #16 on: June 30, 2008, 03:06:39 PM »

You guys can say what you want but MY lag bolts are not coming out in a collision. I say this because I am thew one that put them in. They did NOT go in easy! I used a 1/2 inch drive ratchet with a 3/4 inch socket and then it was still hard to get them thru the 2 pieces of 3/4 inch thick hard plywood! I'm talking about hardly being able to turn the ratchet hard! Squeeky hard! In fact at one time I thought I was going to have to use a breaker bar! 8 bolts took about 1 1/2 hours! Trust me, they aren't coming out, besides the seat belts are bolted to the frame and if anything stupid happens, they will hold the passenger AND the seat!

BS
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H3Jim
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« Reply #17 on: June 30, 2008, 04:58:15 PM »

Even though they were difficult to get in, I bet an accident the lags in wood would still pull out.  I pray that we never find out.
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« Reply #18 on: June 30, 2008, 05:06:23 PM »

A backing plate is a good idea and better than just large area washers. If you can trial fit the assembly and be sure all your holes line up then some liquid nail or some other similar adhesive should be fine. After all it is simply just to hold it in place in case you want to remove the seat right?

I would be cautious about tapping the plate. You want to be sure you have enough threads to do the job, If in question you can weld nuts to the plate to be sure. Another option is nut plates that can be riveted to the plate. Either is fine.
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wvanative
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« Reply #19 on: July 02, 2008, 01:19:00 PM »

You guys can say what you want but MY lag bolts are not coming out in a collision. I say this because I am thew one that put them in. They did NOT go in easy! I used a 1/2 inch drive ratchet with a 3/4 inch socket and then it was still hard to get them thru the 2 pieces of 3/4 inch thick hard plywood! I'm talking about hardly being able to turn the ratchet hard! Squeeky hard! In fact at one time I thought I was going to have to use a breaker bar! 8 bolts took about 1 1/2 hours! Trust me, they aren't coming out, besides the seat belts are bolted to the frame and if anything stupid happens, they will hold the passenger AND the seat!

BS

Well As I see it lets say you went with the lag bolts with the seat belts bolted to the frame, I'm not sure about the weight of the seats but I'd guess 100 to 300 lbs, add the weight of an average person 150 to 250 and you could have a total weight of from 250 to 550 lbs. If the bolts failed but the belt held I would hate to think of the G-forces exerted on the person in that seat, and with the possible weight behind it you could possible cut them in half. Maybe  someone could run some numbers on what kind of forces at driving speeds you might get. If it were me I'd want it bolted to solid steel.

Ok guy's Blacksheep might have something going here that will require a test with an old bus. and of course a test dummy. First Who wants to be the dummy LOL.

WVaNative
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JackConrad
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« Reply #20 on: July 02, 2008, 01:37:59 PM »

A standard nut thickness is equal to the diameter of the bolt it is made to for (a 1/4" nut is 1/4" thick, a 1/2" nut is 1/2" thick, etc.).  We welded 1/2" plate steel to the bus frame before installing the wood floor. 6 holes were threaded for 1/2" fine thread bolts (4 for the seat pedestal ands 2 for the seat belt). 3/4 plywood sub floor and finish wood floor was installed with oversize holes at each threaded hole.  Seat pedestal and seat belts were then attached with grade 8 bolts.  Less would have probably been adequate, but  this was one place I not going to take any chances.  Drivers seat used OEM bolts and pedestal. OEM was 4  1/2" fine thread bolts through framing under driver's area with washers and self locking nuts.  Jack
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Blacksheep
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« Reply #21 on: July 02, 2008, 01:47:30 PM »

Jack sounds like you did a great job as always and went the extra step/s!

BUT...

I swear some of you guys crack me up! If you spent even half the time on your bus as you do pondering over what is right and what is wrong, you might eventually have a running bus or at least one that is liveable!

G-forces? This ain't a friggin nascar racer were talking about! Were talking about a 30k lb plus vehicle that is good to get out of it's own way! Heck half or more of you don't even use them to get them moving!

I guess these lag bolts I used that are NOT coming out are in the same catagory as the waste tank I "hung" from my upper frame in my bay! That WAS supposed to come out from all the sloshing and fall somewhere in the middle of the interstate and wind up killing a family of four! Guess what? Nobody killed in the last 5 years and being that it's aluminum, which was a definite no no, there has been no leaks of any kind!

I think sometimes you guys need to use a little common sense and  better judgement as in look outside the box? Take the blinders off and get the bus done and ENJOY life as it is!

BS

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Don4107
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« Reply #22 on: July 02, 2008, 04:07:50 PM »

Ace,

It is clear that you simply don't grasp the physics of a collision.  You are old enough to decide if you want to mount your seat with wood screws.  (From your description, improperly installed wood screws, wrong size pilot holes.) If you want to be the first one at the accident to get a real close look at the pavement, that is your choice.  Subjecting a passenger to that is another thing. 

Recommending it to another is irresponsible.  Kevin was not sure so he asked.  Kudos. I think Kevin is on the right track to mounting his seats safely. 

It may take me a little longer to get my next bus on the road, but at least I will have the satisfaction of knowing that I did not knowingly cut any safety corners to get it there.  In the mean time I will still occasionally sit in my properly bolted down drivers seat and make Detroit sounds with my lips while hoping nobody gets in your way out there on the highway causing you to test you alternative seat mounts.   Grin

Don 4107
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Don 4107 Eastern Washington
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« Reply #23 on: July 02, 2008, 05:58:31 PM »


I know I am very new to this forum.  I post several Questions to the members for there opinion.
I have appreciated all the knowledge from others who know more that I do. I must say I do not want
advice that will { even a little } put my wife and kids at risk. For someone to recommend lag bolts in a
wood floor to hold a seat and safety belt is just plain wrong. The cost of grade 8 steel bolts along with
a piece of steel is only  a few bucks. I work in the construction field and can say in no way shape or form
should lag bolts be used in a wood floor to hold a seat or seat belts. Wood expands and contracts with
the weather. Posting what you may have done is one thing. Telling others it will be safe with such attitude
is just plain not good.  I am surprised that you didn't use duck-tape to mount your seat.
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Blacksheep
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« Reply #24 on: July 02, 2008, 06:08:47 PM »

Duct tape? How did you know that I used that to hold my ceiling up? You guys know all the tricks! Can't get anything past any of you!
BS
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cody
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« Reply #25 on: July 05, 2008, 02:43:07 PM »

I was curious on the lag bolt idea so I posed the question to a friend of mine that is a structual engineer, and another friend that does accident reconstructions for the state police, they didn't know either but said it wouldn't be hard to find out, we used 1/2 inch lagbolts, and screwed them thru 2 thicknesses of 3/4 in plywood and on a vertical pull it only took 475 pounds to pull them completely out, on a 30 degree angle (thats what he figured the frontal impact of a crash with a 40 percent decrease in speed within the first 1.5 seconds, the guy even stated the G force created by the simulation of rear ending a car at 55 miles per hour assuming the car was going 30 miles an hour and the bus traveling at 55 miles per hour) the pounds needed for that situation increased to 515.  Their opinion was that even without impact, the force generated by hard braking could turn the seat into a launching pad, at the very least it would "most certainly" fail to remain secured.  I posed the next question to them, what would happen if the seat belt held, their response was that it would cut the person in half easily and that was without impact, only hard positive breaking of a 30,000 bus traveling at 55.  I felt that these 2 guys would be qualified to answer the question and that is the answer they gave, whether it's right or wrong doesn't matter, they just gave a straight forward reply using their knowledge base of their particulare fields.  Their opinion that to do that would be suicidal at the very least, so for whatever it's worth, thats the answer as seen by them.
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