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What I did to avoid large and expensive cables is a rear battery, preferably pure lead agm. It acts as a buffer or large capacitor, and only needs two 4 gauge copper / 2 gauge aluminum cables back to the main batt. It's rare, at least in my use cases, to sustain 300+ amp draw, especially with...

Glad to see someone still reading it in 2024! Can't believe it's been 8 years since I geeked out, lol I've recently lost 2 alternators, one on a non-truck. Did some research and realized how poorly most OEM alternators are at supplying high amps @ low rpm, due to lack of cooling and cooking the...

The video shows an F450, which is much stronger than a 350 chassis cab. But good question, I too wondered where they measure it. Took some more digging...

http://d3is8fue1tbsks.cloudfront.net/PDF/Ford/Ford%20f350%20450%20500%20cab%20chassis%20spec.pdf Page 19, F350 chassis, 36 ksi frame, 8.7 sec modulus. 26,100 lb-ft bending strenght, believe it or not, lower than a modern Ram pickup. Thickness by itself can be deceiving. I feel we're all...

Interesting. On Ram 1/2 tons, 5'7 beds have forward bed mounts rear of the control arm bracket, and 6'4 beds slightly ahead of the bracket. In my future crew cab 5'7 bed build, the rear seat is coming out, and heavy stuff will be stored in its place (batteries, water, etc.). The bed will have...

Engineering is so over-rated... BRO science all the way!

Section modulus listed here (under Measurements): https://www.carhp.com/ram/3500-2014/specifications 50 ksi is published data from Ram. 3000 lbs is a conservative minimum based on light wrecker bodies: https://www.millerind.com/products/light-duty/century-411-412 Most that I've seen do not...

Sounds like the absolute worst case for stress concentration! Based on your info, I feel the ideal truck for high speed desert type offroading is a reg cab long bed. Load the COG ahead of the rear axle (easy on a long bed), so during a full compression impact, it's actually bending (not...

Pictures to show why frames always break where they do, look how much thinner it gets past the cab: Now hang a 2000 lbs camper out back, hit a big bump, full bump-stop contact (just inches past the the cab to bed transition), not hard to bend the rails. I just learned this about the Tundra...

Very good point - look at old military trucks like Deuce / M900 5-tons, their "cross country" payload is exactly half of highway payload. A deuce can carry 5 tons on pavement, and a 5 ton can carry 10. Ram should start advertising cross country payloads, lol

Crew cab short beds seems to be the worst for frame bending. 1) COG is almost always behind the rear axle 2) The bump stop is the closest to the cab to bed transition point. That point appears to be a weak-link, thus all the bend examples we see happen here. The frame under the cab is the...

Just hearsay passed around forum to forum. If it really is a Torklift, then it is a bolt-on. Heat treatment on these modern pickups probably falls in the gray zone. Older ones like c-channel Fords were near certainly not heat treated, 36 ksi steel is pretty much rebar grade. Ram uses 50 ksi, GM...

Some math for those curious The Ram 3500 has a frame section modulus of 9.3 in^3, tensile strength is 50,000 psi (or lb/in^2). Multiply the 2 and we have a max frame bending moment of 465,000 lb-in, or 38750 lb-ft. In the wrecker example (3k lbs hanging 6' out back), bending moment was 18k...

I didn't realize the combo has been used for that long. Based on the Raptor / ZR2 / Gladiator frame failures, I'd say big bumps, and many of them over course of 35,000 miles. The Raptors that broke their frames were carrying barely any weight. On the other hand, a 30 foot Class C weighs a lot...

I read on another forum it's the front camper tie-down, apparently welded onto the frame. Don't know for sure though. I want to believe it's the axle arch as well, that's how the older Raptors and ZR2s bent. In that case the bed probably ripped off its mounts, as it remained straight in the photo

Not to turn this into a physics thread, but that's not how forces act upon the frame. I can upload a free body diagram, but this is easier to explain: If your theory is correct, then I can put an infinitely heavy object on that towtruck (say Cat D8) and it'll never flip, right? Because the...

The wrecker I posted was a GM 3500. An Eagle Cap 1165 has a COG at 61.5", or just over 5' behind the cab. That's right on the axle. Even if you shift that back another foot, we're talking 6000 lb-ft of bending moment. If a wrecker can take 18000 lb-ft of bending, day in day out, for years...

Makes zero difference from a frame bending perspective. 3k lbs load, 6' behind rear axle, axle is the fulcrum, bending moment is 18,000 lb-ft

It's not a spec, just based on what 1-ton class wheel lifts are rated to carry (3k lbs at very minimum), and their typical distance from rear axle. I've never seen a wrecker with chassis reinforced at that particular area - just behind the cab. Not saying never, just never seen one.

I believe it's a frame defect, not caused by general overloading. A frame doesn't fail by overloading per se, it's the bending moment. As rear heavy as that camper is, it's no where close to this: 1 ton chassis are designed to lift 3000 lbs 6' behind the rear axle, day in day out. That's way...