Sway bar installed

"Smallbear wants a modern Syclone, local Maple Leafs spammer" (smallbear94) 09/08/2015 at 09:45 • Filed to: None

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Three thumbs up.

It’s just a tad less wobbly in most situations, but even with that slight difference it feels more alive in some unfathomable way. Come to a corner and it becomes clear. Even though the steering rack still has the lock-to-lock of a tractor, it is much more responsive. It feels better balanced. The tire squeal is much reduced, and now comes more from the back, rather than an overloaded front. You can feel that it’s much less understeery.

Of course, this is old new to those who drive anything with a hint of pedigree, but it’s so awesome to me I just had to make a post about it. It’s like a GTI-effect change. It’s the same truck, and yet somehow it’s not.

Also, because I'm a worrywart who never thinks things through 100% (bad combination), I've just put 2 holes 3/4" diameter in my frame. Should I get an extra peice of steel welded to the bottom to make up for it? It's a full box frame, does it matter? The leaf spring joins the frame about 1' behind the hole.

RamblinRover Luxury-Yacht > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/08/2015 at 09:52

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Three thumbs up.

IT’S FUNNY BECAUSE ONE OF THEM IS IN HIS PANTS.

Frame strength - entirely depends on the size of the hole relative to the frame cross-section, the location of the hole, and the direction of loads (and thus bending moments on the frame). Usually a hole through the side wall will have less of an impact than through the bottom for up/down loads, and bottom holes have less of an impact on side loads. Usually something like what you’re talking about isn’t a real killer.

SidewaysOnDirt still misses Bowie > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/08/2015 at 09:56

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I wouldn’t be too too worried baout the holes. I’d be more worried sealing it to prevent water getting in and it rusting out from the inside myself. You might want to just rustoleum the area to prevent surface rust and cover it up with something. Glad the sway bar ended up doing what you were expecting.

Smallbear wants a modern Syclone, local Maple Leafs spammer > RamblinRover Luxury-Yacht 09/08/2015 at 10:07

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About a 3-1/2” tall frame at that point, about 1-3/4”—2” thick, full box. Hole is located about 1” on center from the bottom of the frame. 3/4” diameter. CoG of a full bed would be on or a little forward of the hole, which is what’s bugging me, since the leaf spring hooks up to the frame on either side of that weight.

But considering this is offered for sale and so many people have had no issues, I don't think I'll have a problem—It's that niggling 1% of my brain that keeps saying "what if, maybe you should reenforce it now" that keeps bugging me.

Smallbear wants a modern Syclone, local Maple Leafs spammer > SidewaysOnDirt still misses Bowie 09/08/2015 at 10:09

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Yeah, I plan to get in there with some sort of rust protector, but I didn't have any on hand. and of course today it rains, just what I needed

Snuze: Needs another Swede > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/08/2015 at 10:09

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I think you’ll be fine. The hole is small and pretty far back, relative to where the highest bending moment is (towards the center of the truck). Also, adding plates to the top or bottom does very little in regards to bending strength compared to the vertical members in the box frame - this is due to the resistance to bending based on the moment of area.

Smallbear wants a modern Syclone, local Maple Leafs spammer > Snuze: Needs another Swede 09/08/2015 at 10:13

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My logical train of thought agrees with you. The 1% says “no, don’t trust the experts”.

That part of my brain needs a fingers crossed setting.

Recommend, and thanks for the reassurance

RamblinRover Luxury-Yacht > Snuze: Needs another Swede 09/08/2015 at 10:16

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Well, yes and no. Adding thickness to the bottom/top alone isn’t a profound impact on its own and the height is the single biggest factor, but the difference between outer height ^4 and inner height ^4 grows in a huge hurry with increase in thickness once the frame is tall enough.

Snuze: Needs another Swede > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/08/2015 at 10:21

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It’s completely understandable - frames are pretty important to the integrity of the vehicle and we’re always trained to think that messing with a vital component is more likely to lead to disaster. Now if you tow haul a lot of heavy loads, I would have more cause for concern, but in general I don’t think it’s a huge deal.

I can show you some of the theory and math if you’re interested in that sort of thing.

Smallbear wants a modern Syclone, local Maple Leafs spammer > Snuze: Needs another Swede 09/08/2015 at 10:25

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I don’t tow much. I do occasionally load the bed to capacity (heck, may have been over once. not sure). Not often in any case.

I am definitely interested in the math if it’s not a pain for you, thx.

Snuze: Needs another Swede > RamblinRover Luxury-Yacht 09/08/2015 at 10:25

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Good point. I’m just thinking that most truck frames aren’t very tall relative to their width that it would make a huge different. I suppose anything helps, though. Also, I just saw this in smallbear’s response to your post, but the hole is 3/4” dia. and center is 1” from the bottom of the frame. That only leaves a 5/8” web at the bottom to resist bending. Even though the hole is round, I might have some concern about crack formation and propagation between the bottom of the hole and the bend where the metal transitions from vertical to horizontal. Thoughts?

RamblinRover Luxury-Yacht > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/08/2015 at 10:26

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Pretty much anything you could do to add a reinforcing plate would compromise the strength of that far worse than the hole. The hole isn’t adding much in the way of brittleness, just a tiny amount of strength reduction - welding would push things much too far in the other direction, as would pretty much anything added to the bottom web with screws/whatever. The top and bottom webs contain a lot of strength. Doing away with one of the sides of the frame completely would cut strength to around half as a rough estimate, doing away with top or bottom web completely would cut strength to about ten percent.

Smallbear wants a modern Syclone, local Maple Leafs spammer > RamblinRover Luxury-Yacht 09/08/2015 at 10:29

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So it would make it stiff enough to break something else instead is what you’re saying?

As to the rest of the info, this is exactly the reassurance I was looking for, thanks.

415s30 W123TSXWaggoIIIIIIo ( •_•))°) > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/08/2015 at 10:44

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Put Por-15 on it.

RamblinRover Luxury-Yacht > Snuze: Needs another Swede 09/08/2015 at 11:09

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I just ran a really rough bunch of back of the envelope sort of calculations assuming a box with 1/8” wall, his dimensions, and unless I’ve done things horribly wrong, his chassis rail wouldn’t even blink at a 3000lb load on one side, or 6000lb on both. Now, with safety factors being what they are and dynamic loads being what they are, that’s not as amazingly safe as it sounds, but it’s still not shabby. If we assumed a reduction in strength of 1/3 distributed through the wall of that side, that’s only ~17% loss of strength overall - and that would be if the entire side were thinned out of steel (think really bad rust). You don’t see that kind of effect from a hole that’s not *right at* the edge, because the distribution of stress in the wall is related to the third power of distance from center (usually). If you take the integral of x^3 from .21 to .64 and subtract that from the integral of |x^3| from -1 to 1, then divide by the full amount that should be the percent remaining strength (wall size and hole locations normalized to -1 to 1 scale). That gives ~92%. A hole *is* a stress concentrator, however. There’s a stress concentration factor of no more than 2.5.

Does that mean his frame is 1/2.5 as strong? Well, no. Not in the least. It means that the sidewall stress is (for purposes of fatigue and to some extent loading) increased by a factor of 2.5, but the actual stress there in the sidewall should be much less even after that than the stress in the top and the bottom. In fact, at the bottom edge of the hole, it should be just under 1/4” of the full stress. 2.5 * .25 = .625. Not an issue.

RamblinRover Luxury-Yacht > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/08/2015 at 11:14

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Welds compromise strength unbelievably. They typically cause the formation of zones of martensite, which is very hard but quite brittle. If you welded something on, it would be stiff until it or something it was welded to snapped at a weak point in the weld zone. We’re talking localized weakness to like 1/3 strength. As to the hole itself, I just ran some numbers for Snuze - back of the envelope style.

http://oppositelock.kinja.com/i-just-ran-a-r…

Short version - worst case, you’re looking at your frame being about 8% weaker at that exact point, and it can take it. There is almost surely another hole location or welded area or something that is worse.

Smallbear wants a modern Syclone, local Maple Leafs spammer > 415s30 W123TSXWaggoIIIIIIo ( •_•))°) 09/08/2015 at 11:16

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Never heard of it. I'll look it up.

Smallbear wants a modern Syclone, local Maple Leafs spammer > RamblinRover Luxury-Yacht 09/08/2015 at 11:17

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Great, thanks.

Really glad I bounced that idea off oppo first...

Smallbear wants a modern Syclone, local Maple Leafs spammer > RamblinRover Luxury-Yacht 09/08/2015 at 11:19

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Recommend.

Snuze: Needs another Swede > RamblinRover Luxury-Yacht 09/08/2015 at 11:25

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Thank you for stepping through the calculations for me. One of the things that annoys me most is I spent all this time getting an engineering degree, and in my “engineering” job I use almost none of it. Especially things like structural mechanics. I remember some of the basics of beam loading and moments of intertia, but definitely didn’t remember anything about the distribution of stress in the wall, and the stress concentration factor.

RamblinRover Luxury-Yacht > Smallbear wants a modern Syclone, local Maple Leafs spammer 09/08/2015 at 11:29

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A Land Rover Series (the old one) 109 (the long wheelbase one - pickup style and so on) has a taller frame cross-section than the short wheelbase versions and extra “strap” steel added to the bottom web in a couple of places just like you were proposing. Several big factors make it different, though:

The frames are edge-welded box sections of flat mild steel. This means:
Less martensite (less carbon present, different welding)
More flexing elsewhere (less strength demanded of the weld)
No single area of weld to fail (welds 48”+ long)

The straps are mostly welded at the side/edge, where weld already exists. No extra likelihood of cracking beyond the normal limits of the frame.

Thin metal - both the original frame and the strap. A large percent increase in strength from a comparatively small piece of metal.

The 50s-80s. Nobody cares if you’re compromising strength in one area or one point when you have very limited ability to figure out where your stress problems are anyway. Build it by guesstimate and overbuild, and if it works, huzzah!

For extra fun, these frames have a lot of holes in them - mostly small ones. The cross-sections are also huge due to that whole thin sheet thing - the frames are >7” tall in places and about 3” wide.

Smallbear wants a modern Syclone, local Maple Leafs spammer > RamblinRover Luxury-Yacht 09/08/2015 at 11:31

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Recommend.

RamblinRover Luxury-Yacht > Snuze: Needs another Swede 09/08/2015 at 12:02

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I’m in an engineering-ish job that uses basically none of this because it’s mostly drawing sheet metal parts... so I do this for hyucks in my spare time. On the stress distribution, I may have gotten that completely wrong since I was back-working from how the moment is calculated, but was forgetting that the calculation for stress at a point in a solid beam is actually just pure distance off-axis. Because stress has to be proportionate to strain, and strain is linear as you head away from central axis. Yes, the strength of the beam from its shape doesn’t actually correlate directly to what the distribution of the total force is, and I am a moron. To figure actual strength reduction, you would have to be weighting the linear increase in strain vs. the distribution by surface area of what is actually bearing the load. Regardless, the sides are under very minimal strain until they actually reach the edges, and the top/bottom are still bearing the brunt, so my number *may* be a good estimate.