Bolt strengths

[Zephod]

I'm glad I found this. According to my calculations my waste barrel attachments should hold over 7,000lbs - sufficient to hold a maximum 130lbs

At least now I can stop overdesigning stuff so much. My underbody battery cage will hold a 20lb battery and will probably weigh 20LBs itself. It will be suspended from 16 x 5/16 bolts. That should work!


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[Iceni John]

Remember that those are all static loads.   Moving vehicles also have to withstand dynamic loads.   I design for dynamic loads three times greater than static loads, i.e. each full 110-gallon water tank is about 1000 lbs static load, but up to 3000 lbs dynamic load.   That's why each tank's support frame is hanging from ten double-nutted 1/2" threaded rods that are attached to the frame rails and structural body longerons.

John

[Zephod]

I'm sure even with a dynamic load of 3x 40lbs, 16 x 5/16 bolts should be fine.
As for my waste tanks - both grey tanks are 15 gallon and are supported by 5 chains with the weak points being the turnbuckles so 5 turnbuckles at 130lbs max for a 130lb tank. Basically, 5x the max dynamic load. The ends of the chains are fastened and the load shared between 28 x 5/16 bolts.

I'm using a single 35ah battery. I see no reason to use anything more powerful when all it powers is ventilation and a USB charging station. That's my 20LB battery and I'll have to build a cage for it which will probably end up being the same weight as the battery.


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[HB of CJ]

Do not forget the rare airborne event running over the non avoidable road debris.  This would include big heavy junk coming off of whatever including tires, wheels, loose truck load stuff and whatever.   This could result in a momentary 3-6 gee event.

The bottomless pothole also comes to mind.  On the interstate in New Mexico crossing a river on a bridge in such bad condition you could look down 100 feet to the water ... all while being in the truck lane with zero warning of such.  Interesting results.

It would be embarrassing to have your Bus Conversion rendered heavily damaged by stuff inside and outside the coach breaking loose when some initial better engineering design and construction could prevent such.  What could fail?  Interesting. 

[muldoonman]

Do not forget the rare airborne event running over the non avoidable road debris.  This would include big heavy junk coming off of whatever including tires, wheels, loose truck load stuff and whatever.   This could result in a momentary 3-6 gee event.

The bottomless pothole also comes to mind.  On the interstate in New Mexico crossing a river on a bridge in such bad condition you could look down 100 feet to the water ... all while being in the truck lane with zero warning of such.  Interesting results.

It would be embarrassing to have your Bus Conversion rendered heavily damaged by stuff inside and outside the coach breaking loose when some initial better engineering design and construction could prevent such.  What could fail?  Interesting. 

Maybe double up on those 5/16 bolts and take all the worry out.

[Zephod]

LOL. My waste barrels will give way, way before the attachments will. As for the batteries, I've not yet 100% decided where to site them. I am very tempted to have them bolted behind the rear wheels.


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[bevans6]

Bolt strength is bolt strength, it's based totally on the material and the cross-section area of the fastener.  Dynamic vs static loads play no part in bolt strength.  SAE grade 5 tensile strength is 120,000 psi, grade 8 is 150,000 psi, socket head cap screws (Allen bolts) are 180,000 psi, as are L9 bolts.  Each of these also have design specifications like thread root radius, radius under the bolt head, type of finish and installation instructions so you can achieve the rated strength in application.  SAE, SHCS and L9 bolts are not really rated in shear strength, it's not part of their design specification, but you usually use 60% of UTS (ultimate tensile strength).  Aerospace bolts (AN/MS and NAS are common) are usually rated in both tensile strength and shear, and are designed for double shear installation.  They come in 1/16" length increments so you can always have the perfect size bolt for your application.  When I was doing car racing I learned an awful lot about fasteners.  I used to install a battery like yours with two 10/32 screws and AN nut plates, and four rivets.

[Zephod]

Bolt strength is bolt strength, it's based totally on the material and the cross-section area of the fastener.  Dynamic vs static loads play no part in bolt strength.  SAE grade 5 tensile strength is 120,000 psi, grade 8 is 150,000 psi, socket head cap screws (Allen bolts) are 180,000 psi, as are L9 bolts.  Each of these also have design specifications like thread root radius, radius under the bolt head, type of finish and installation instructions so you can achieve the rated strength in application.  SAE, SHCS and L9 bolts are not really rated in shear strength, it's not part of their design specification, but you usually use 60% of UTS (ultimate tensile strength).  Aerospace bolts (AN/MS and NAS are common) are usually rated in both tensile strength and shear, and are designed for double shear installation.  They come in 1/16" length increments so you can always have the perfect size bolt for your application.  When I was doing car racing I learned an awful lot about fasteners.  I used to install a battery like yours with two 10/32 screws and AN nut plates, and four rivets.

I'm figuring 16 x 5/16 bolts will be more than adequate. In fact, I'd say stronger than the body ribs that I'm attaching it all to! The driving battery compartment is simply welded to the ribs with single welds the width of each rib.


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[kyle4501]

It isn't just about bolt strength - If the torque isn't correct, or if the bolt head pulls thru, or corrosion from dissimilar metals, or the part you are bolting to breaks off, or, or . . .

Bottom line, make it safe for the people you share the road with.

[Zephod]

It isn't just about bolt strength - If the torque isn't correct, or if the bolt head pulls thru, or corrosion from dissimilar metals, or the part you are bolting to breaks off, or, or . . .

Bottom line, make it safe for the people you share the road with.

Y'all make it way more complicated than it is. You can feel when a bolt is tight and if like me, you use lock washers and lock nuts, you're pretty solid.

Anything can break off from fatigue - we're talking old busses. Nobody has a brand new bus.


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[kyle4501]

Y'all make it way more complicated than it is.

That is because it can be. Fatigue is NOT a result of magic.

Just because you don't understand something doesn't mean it is a trivial matter.

[eagle19952]

That is because it can be. Fatigue is NOT a result of magic.

Just because you don't understand something doesn't mean it is a trivial matter.

some people won't hear even with headphones