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Author Topic: Bolt Strength  (Read 181 times)

mike90045

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Bolt Strength
« on: January 08, 2019, 04:45:37 AM »
https://www.boltdepot.com/fastener-information/materials-and-grades/bolt-grade-chart.aspx

Had another bolt break today.   1/2" di, 20tpi ( fine thread ) It was magnetic SS, USA made not chinese pot metal  (the cast iron was not damaged, I caught it early)

I've been wary of grade 5 & 8 because I've understood they are tough, but brittle and would not last long on a listeroid

What does the hive mind think ?

I've heard tell of get graded bolts, heat them up to temper their brittle hardness and let them cool slowly.   But would that soften them too much ?   

ajaffa1

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Re: Bolt Strength
« Reply #1 on: January 08, 2019, 05:22:53 AM »
High Mike my understanding is that High tensile bolts should be heated until glowing red, they should then be quenched in water to harden them. They should then be heated again until the steel starts to blue, allow to air cool. You should now have a hardened and tempered bolt. The process does vary somewhat depending on the type of steel.

May sound like a silly question but are the bolts snapping or shearing? If they are snapping it could be that they first work loose allowing the engine to hop up and down a fraction increasing the stress on the bolts.
If they are shearing it could be that the base of your engine is rotating a fraction and the bolts are getting guillotined. If it is the later you could fabricate some steel plates one for each corner to stop it rotating. I believe the original specification for mounting these called for a very substantial concrete foundation, the four corners then had to be shimmed to ensure they were level and then set in cement grout before tightening the bolts

Bob

mikenash

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Re: Bolt Strength
« Reply #2 on: January 08, 2019, 06:28:17 AM »
The good news is that 1/2" bolts are cheap (or at least 12mm and 14mm ones are here) so I assume imperial (inch) ones are for you guys

I have 14mm bolts as hold-downs on the Lister

I wouldn't have thought that M12 8.8 bolts would be "brittle"?

And I'd consider trying some stainless bolts - in pump applications we regard them as "tough"

Better-educated folk than me will have a good handle on the properties

mike90045

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Re: Bolt Strength
« Reply #3 on: January 08, 2019, 06:54:51 AM »
Bolts are torqued up tight, then a nyloc nut snugged on as a jam nut.  In the past, they all have snapped, not sheared.   Looks like I've got a bit of flex in the I beams the frame is made out of.  Wow.

Frame is anchored to 8 (or 10) inch slab.  Frame members are 4" i-beams, laid over 4" plywood strips on the concrete, so the wood should take up any irregularities.  Large welded "U" bolts trap the i-beam over the wood strip and pinch it to the slab, with a total of 8 nuts over a 3/4" SS all thread epoxied into the slab.  All that stuff is tight.

mikenash

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Re: Bolt Strength
« Reply #4 on: January 08, 2019, 07:21:08 AM »
My own off-the-cuff diagnosis - FWIW - is maybe you haven't got a bolt problem . . .

Maybe there's a load problem, in that if there is imbalance in the flywheels, the forces they are generating as the imbalance rotates - maybe lateral, maybe vertical, maybe tangential - but all forces wanting to lift/move the base off its mounts . . . maybe those forces are greater than the bolts can withstand

If that is the case, imbalance may have to be addressed?

just my $0.02

mike90045

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Re: Bolt Strength
« Reply #5 on: January 08, 2019, 07:49:52 AM »
My own off-the-cuff diagnosis - FWIW - is maybe you haven't got a bolt problem . . .
Maybe there's a load problem, in that if there is imbalance in the flywheels, the forces they are generating as the imbalance rotates ........

I hope that's not it.  I ran it once early on, before bolted down, didn't seem too wild.    Wow.  What's the guidelines for the flywheel counterweights.  Opposite the offset in the crank ?    I'll look and see where they are, never looked at that before, and I've got a couple hundred hours on it already.  Wouldn't that beat the band, if a flywheel was swapped.

mikenash

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Re: Bolt Strength
« Reply #6 on: January 08, 2019, 08:08:16 AM »
Mike, I could very well be talking through a hole in my head about that

I just know that over here there are hundreds of old Listers that ran for many decades bolted to a couple of bits of timber bolted to a timber woolshed floor.  Even after the timber disintegrated and the floor sagged - they just continued to run . . . .

On here there is a big thread (several big threads) about balancing "Listeroids" and about how some are "hoppers" and some are "drifters"

Have a look and form an opinion . . . .

http://listerengine.com/smf/index.php?topic=6158.0

Try the link above to get you thinking?  There are several such threads

Meantime - there's probably not much to lose by playing with different bolts?  However, if there are odd forces at play, and you lost two bolts during a running session without noticing & stopping - maybe there would be a danger of snapping a corner off of a casting?

Again, better-informed folks than me will know

Good luck

ajaffa1

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Re: Bolt Strength
« Reply #7 on: January 08, 2019, 09:04:31 AM »
Not quite sure how to respond to to a conversation between two Mikes, however, Mike (with problem) I am concerned that you have a plywood filler between your frame and your slab, this could result in a resonant frequency vibration which is stressing the bolts. Cut out the ply and us a cement grout to ensure there is no movement between the two.

Mike (with solutions/recommendations) I totally agree with you that this may be a balancing issue, a hopper is going to destroy bolts, if you replace these with bolts that don`t get destroyed it is very possible that castings will crack. Mike (with problem) you need to check the balance of your engine, please check out 38ac`s information on the wall of knowledge.

AdeV please restrict the number of Mikes to a manageable level, please don`t rename them Michael, even more bloody typing!  :laugh:

Bob

BruceM

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Re: Bolt Strength
« Reply #8 on: January 08, 2019, 03:52:23 PM »
I agree with mikenash.   Serious balancing problem if you're snapping 1/2 bolts, no need to look further.  Get a piece of 2" shaft on Amazon and use 38ac's method for your flywheels, then add/subtract weight as needed to tame it.  Plenty of these on carts. 

I originally mounted mine on a engine room slab, 10" think where the engine was.  Even on the wood base and 1" thick rubber pads, it vibrated the whole steel sided engine shed, audibly.  I used the Mr X method, which took quite a few hours but did work.  On my neighbor's DES 8/1 modified for propane, I used 38ac's method and highly recommend it.

Balance first, then grout as Bob suggests.  You might want to unbolt and slip some carpet scraps or such under it for fine tuning the balance. 


mike90045

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Re: Bolt Strength
« Reply #9 on: January 09, 2019, 07:58:13 AM »
Running nice and smooth again now, all bolted down with real bolts - not frozen butter.   
  We're in a bad storm pattern, hardly any solar harvest, and running a couple hours daily for power.   I sit with the beast when it's running.   Just got about half inch rain dumped in the last hour, lots of water ponding on the ground.

mikenash

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Re: Bolt Strength
« Reply #10 on: January 09, 2019, 05:02:53 PM »
Cool.  Good to hear, Mike

I'll be interested to hear how you get on with bolts.  If you have found a grade of bolt that is tough & durable, I'd be very interested to hear what it is so as to consider using it in other applications

Whereabouts are you located with that bad weather, Mike?

Cheers

mikenash

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Re: Bolt Strength
« Reply #11 on: January 09, 2019, 05:07:18 PM »
Oh - I see your other post "Northern California"  Right