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Author Topic: Blind concrete bolts  (Read 2738 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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paulcjhastings
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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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kwood
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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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Len Silva
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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.

Don and Cary
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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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