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Each vehicle manufacture has different recommendations. They are listed in their body build manuals, some require an angled spliced joint on frame rails, some don't. The Code Of US Federal Regulations Title 49 requires commercial motor vehicles operating on the road to follow vehicle manufacture recommendations for all frame modifications and repairs.

I am a welder with schooling and experience. Not an engineer. I was taught to minimize heat input. By doing anything mor than a 90 degree angle, you are essentially lengthening the cut, and therefore dumping more heat into the material, causing more warpage amd distortion. Ive always wanted to build a chassis from scratch. Id go with 90 degree butt weld if i had to do it, and miters for any angle joints i couldnt bend.

i think they are only seen as "stronger" because the welding isnt up to spec haha

Some good information here, he knows his stuff. Keep it simple works.

The last 1/3 of your video is absolutely on point and describes the situation I. Canada as well. very well presented.

I have seen videos from Germany, where professional aftermarket manufacturer that specializes in lengthening frames for Mercedes Bens trucks, and they did cut it straight down and welded it. I think zig zag cuts and welding is stronger up to a point, but straight down, and if you weld it correctly then you will be fine. And if you add fishplate on top then you are golden...

How about bevel for deep penetration.

more weld surface area with the scarf joint

Thank you for the excellent information.

Here in New Zealand, all chassis splices have to be vertical cuts reinforced with fishplates to meet certification standards.

7:46 I think we can agree that a typical DIY MIG buttweld on a framerail is more likely to stress crack rhan a nondisturbed framerail, To minimize the risk of a catastrophic failure it seems a good idea (or at least a possibility) to put the stressed parts of the weld separated on the frame with a Z .configuration. But of course your simplified stress analysis is quite correct.

What engine do you have and what made you change from the tdi300 or 2.8 TGV?

18:47 you went through and talked about the math in depth, thats far beyond common since, so bassicly Its the material, not the joint. The only concept i could come up with is yes timber framing and weld length but the weld is much longer On a 45 the a 90dgr joint but if the weld is too cold its going to break anyway you slice it. Last point and its the oldest. What is the strongest shape in engineering? The arch. But a chassis needs to have some flex. Look at some of the newer truck splitting behind the cab on some truck that are at the load limits.

Actually, if you look at Japanese beam splices in wood that lock together without hardware that makes a far better joint, then weld it. Short of rust, its not coming apart ever.

In considering the wood scarf joint versus the welded joint in steel, I think it's helpful to remember that wood members have grain which exhibits different structural properties with cut/joinery angles. Although I'm not a mechanical engineer, (retired electrical engineer) I like your presentation with the analysis, which apparently is quite consistent with history/experience. The good engineer applies the principles in a cost-effective manner, consistent with safety and performance requirements. Thank you sir.

I totally agree with this analysis. As an AWS CWI, a welder performing any welds on chassis should be certified for the process and criteria in the WPS of the performed weld. When I worked as a fabricator on NASCAR teams, all splices were made in this manner (both new and repaired chassis).

The justification I've often been given on the "Z" shaped splice is that it gives you more linear area of weld (and the assumption that gives more strength in the weld). Over the years, out on the farm, we have repaired several trailer and truck frames -- we make the square butt joints you advocate, backed up by either a gusset plate welded into the back of the channel, or by "boxing" the frame by welding the gusset oriented so it turns the structural C channel into a box channel on either side of the joint (extending at least 12" on both sides of the joint). None of the repairs have ever failed, even when overloaded beyond original load specs.

18:00 Government regulations and common sense are mutually exclusive.

this is applying my solid mechanics classes to something real, I like that

There's a big difference between a structural building and an auto. Namely the amount of movement. Also it's not the weld that breaks. Only a dumb welder would look at it that way. The top and bottom flanges should not be cut in line with the website.. a c style or z will make the difference in the amount of flex involved. Also a double plate.

I studied shear force diagrams and bending moments many years ago. Practicalities trump the maths. Welding of non new material causes weakness for whatever reason. ( even though the weld is theoretically as strong as the original material) I’ve seen welds fail where I didn’t think they would. If the new weld on old material is not perfect, there may be merit in spreading this weakness over a larger area or distance utilising the load sharing phenomenon. If you were able to weld two Landrover 110 chassis with both options and run both vehicles over hard rocky terrain, my gut feeling is that the shorter weld would fail first.

Ok, now we know about tires. But what about rooftop tents, drones and outdoor kitchens? In all seriousness, your presentations are great, relaxing and are given me things to think about so I subscribed. Another channel to binge watch until I'm caught up! Cheers!

"the strength of the joint is determined by the strength of the base metal and not the joint itself" is a very good point. I think we tend to forget that when we work with mild steel, the weld joint is generally much stronger than the base metal. I've seen these unusual joint configurations in the woodworking world, and I wonder if in those cases the glue joint is weaker than the wood, and a longer joint is beneficial, hence the diagonal or stepped geometry.

Angle is for crash failure. The weld will fold as designed.

It's done, or requested to be done with 'scarf joints', because the variation in skill of welders. Not every shop that takes on these modifications, and certainly not someone doing this in their garage is guaranteed to be a competent welder.

I am in tears, Sir 😢 I have read Lynette Ramsay Silver's book many times.. It's sitting in front of me now. You will find my Grandfather's name on page 323 of the book under 'nominal roll' ... Cameron, Finlay - QX8427, 2/10 Field Regiment, died at Sandakan on 6th June, 1945. He was one of the 288 left behind after the Second March departed on 29th May when the compound was destroyed by fire. Of those 288, a further 75 had been selected for a Third March. And 23 of the remaining 213 left were marched out to a plantation near the air strip and murdered. According to Kevin Smith's book (Borneo - Australia's Proud but Tragic Heritage), these brave men still cared for and comforted one another to the very end, but all were too weak to bury the dead. This task was carried out by Javanese labourers who packed them into a slit trench. I need to find out if records were kept of these specific exhumations and reinterments, because my Grandfather has to have been one of them... In Kevin Smith's account of what happened at Sandakan in the final days & weeks, on page 115 HE NAMES my Grandfather as having passed away on 6th June, 1945 - along with Pte. Tom Cole. That literally jumped off the page and smacked me bang over the head the first time I read it! There was my Grandfathers' name in print - right there! We'd never known exactly where or when he died before, nor did we know about Labuan War Cemetery . But if there are records of where those 190 poor souls were laid to rest in Labuan War ć, then I can narrow down my search for his final resting place. Thank you for your video on the subject.. Most Aussies don't know about this either.. Lest We Forget ❤

I'm so grateful to find your video - it made me very emotional. My Grandfather's is one of the 'Unknown Soldier' graves here. My mother & Grandmother told me all they knew about my Grandfather after Singapore fell - which really wasn't much. His name was Gnr Finlay Cameron, QX8427 - 2/10 Field Regiment, who was sent to Sandakan with B Force following the Allied surrender after the Battle of Singapore. He almost made it to the end - 3 long years in captivity - but only 6 would successfully escape to tell the story of our brave boys. After reading Kevin Smith's book (Borneo - Australia's Proud but Tragic Heritage), and Lynette Ramsay-Silver's book (Sandakan - A Conspiracy of Silence), I learned that my Grandfather died at Sandakan on 6th June, 1945, being too weak to go on the Death Marches.. at least he was spared those horrors. The POW camp was destroyed by fire on 29th May, 1945, as were all records of the prisoner's existence. The last ones, 288 prisoners including the hospital cases, were then left out in the open on a gentle slope opposite the gate to the Japanese compound - to die .. they were all so ill that they needed little supervision.. 23 of these 288 prisoners were taken out & murdered in a plantation near the air strip, and a further 73 were marched into the interior on what is known as the Third March. But my grandfather lingered out in the open on that slope for a whole week before succumbing to starvation, malaria, berri berri and other deprivations. I also learned that Javanese labourers were tasked with packing the bodies of these remaining 192 poor souls into a nearby slit trench - which were later exhumed and reinterred at the Labuan War Cemetery. So if I am able to locate these particular graves that were originally in that slit trench, I would gladly travel to Labuan and kneel at the foot of each and every one of them - because I know that one of them will be my Grandfather's grave, and I personally want to pay my respects and those of my mother (his daughter) who is now 97 years old. Long after the war had finally ended my Grandmother received a small package. It contained three items that belonged to my Grandfather whilst in captivity.. They were discovered wrapped in a scrap of old rag that had been buried under the burned out compound at Sandakan. They were a handmade identity tag in the shape of Australia with his name, Division, & QX number engraved on the front and his home address on the back; there was also his regiment patch, which he'd kept in remarkle condition, and his "Australia" slouch-hat badge. I am so grateful to be able to keep these safe for future generations, and I always march with them on ANZAC Day. Lest We Forget. Rest in Eternal Peace, Granddad.. You will always be my Hero ❤ XX

In a splice, the strongest welds are always the shortest distance.

In some codes or standards, a horizontal weld does not become a vertical weld until 45 degrees. Vertical down welding can be frowned upon. But 45 degrees down could be considered horizontal and better. Just my ignorant guesstimation. Good video.

i lap over my joints

Two reasons I was taught in school. One is that welding across the frame weakens it as far as attaching things. Many things are attached at factory across the frame but also they are designed to bend in an accident. If welding straight across you are changing the strong vs weak points of frame altering the characteristics in a crash. Second it needs to twist. The angle puts the top and bottom welds across from in different spots. You have more weld so the stress on metal beside weld is less as it’s more spread out. From a twisting standpoint the extra stiffness is not all in one spot. It makes for a more even load when rail twists through its length. A straight splice makes the joint stiff in relation to rest of frame and it will crack beside splice. I see it all the time. Work backwards. Look at cracked frames and you will see an area too stiff by near crack.

All this is way above my simple mind. I just cut the damn thing bevel the edges pre heat then weld the crap out of it with good rods and a hot setting. Put a splice plate on the inside and load it up and go. Never had one crack or break.

While I don't disagree with you and indeed you are correct in ideal circumstances (perfect welds), the world isn't always ideal. Many aftermarket welders are not perfect in their welds. Porosity, undercut or other imperfections weaken the joint. A bit of porosity on a horizontal section of a splice (at 0:18 ) likely makes zero difference in strength. Porosity on a square joint (vertical on a chassis) decreases strength. So, I look at it as an extra safety if there are other shortcomings. Not saying the incline or other angle is stronger, just that it may become a safety net. But then, I've been wrong before 😉

Didn't the inclined cut arise to increase weld length to compensate as rated strength of a weld was once deemed to be less than the strength of the parent material?

Thats correct! These joint design concepts are pre- conceived from our use and experience as a people building with wood.

Yup. Got it ! Thank you !

I agree. The chassis steel is likely pretty low grade and the as-welded filler metal is likely 50% stronger, even using a basic steel type filler. It is also a thin section so that limits other effects. Just make a decent clean weld, it is more important than anything else.

A very nice pesentation - I have just come across your channel and I will look at your other videos. The analagy with old timber joits is well put, but a welded joint is closer to a glued timber structure, which generally need to avaoid tensile glued (end-end) joints. There are a couple of reasons for diferent geometries, but not normally required with good welding / low defects / rough back wall or weld edge. In a standard pressed steel box section chassis section this is seldom and issue as the materials and stresses are not normally highly stressed. In certain circumstances this can be different. > Undermatched weld filler material or loss of properties in the HAZ for either stress levels or fatigue. (ie welding >460RQT will more standard electrodes or where post weld heat treatment is impractical, but also nowadays with some higher strength aluminium structural sections. >> Tapers in the tensile flange can change the primary stress in the weld to me more shear stress than tensile, which can have a lower strength requirement. > Start-Stop defects and residual stress. - More for built up and extended flanged beams >>Where the cross flange weld meets the vertical web weld there will normally be multiple overlaid stop-starts where residual stress and HAZ effects can build up or include contaminants. >>Therefor teh web and flange welds are offset from each other and the last weld is the horizontal weld along the the flange web joint, which is then also extended and tapered out. >Original Beam defects >>Some rolled beam sections tend to have more defects in the thickened transition section between the flange and web. These are normally in line with the beam and acceptable, but with welding heat and stress can become an issue. I believe that this was more of an issue with older / historic beams and thicker sections. For your beam anaysis you can use the general UDLs as you have shown and superimpose point loads from the discrete support points on the chassis. Then use continuous beam theory, but your peak bending stresses will still be similar and at similat locations. You can get more complex if you want, but it isn't really any more accurate once load variations and road conditions, dynamics and shock loads are included. more if you want by using 'spring support points at the spring hangers. Of course the loads are not that defined once dynamics and road conditions are included.

Brilliant! I learned a lot, your presentation was clear and concise. In the aviation world, our steel tube structures are required to be internally doubled and scarfed! I have a question with regards to aluminum beams, would love to converse privately.

I see yo have fish plates on your little finger. Hope the fracture healed nicelt🙂

On the other hand , a long enough weld consisting of pure slag can be as strong as the base material - in theory

It's called "looks right engineering". People do it because it looks right , but have nothing to base it on. As a robotic lab analyser technician I constantly see service manuals from instrument manufacturers calling for the lubrication of fluoropolymer coated lead screws when the manufacturers of the lead screws say to never lubricate them. I ran a trial and found the lead screws ran for life with no trouble if not lubricated , but required frequent ongoing lubrication if they were lubricated at any time. The instrument manufacturers did not read the data sheet on the devices they used and made suggestions based on "what they have always done"

i would say it all started due to the fact that diy people welding aren't coded so the more weld the better i repaired way to many defenders and series 2's and 3's and always cut top to bottom never inclined or z cuts but i did it for a living

I'm a coded structural steel fabricator and a former land rover mechanic and worked for an independent landy specialist and later on for land rover indirectly with multiple factory visits back in the 90'sand early 2000's I've repaired and modified ❤100's of landy chassis in my time and never used spliced joints , always square butt joints with a fish plate as per land rovers own preferd repair process's I've also lengthened hgv trailers in this way and they have always passed inspection here in the UK

Goes on about sheer forces while Brian welds his chassis with a Clarke welder from machine mart and a hours worth of TH-cam videos ...

The biggest engineering justification that I can see is that many modifications are being done by more amateur welders that don't have full weld strength and/or penetration of weld due to improper techniques or materials. Additionally , the welds may rust out quicker (also decreasing in strength) due to improper painting and coating after the weld is done. These improper welding methods decrease the strength of the weld joint by up to 50%. Based on that reality, the joint should be analyzed with a 50% reduction in strength to account for what actually happens in the many different shops making modifications. The only alternative is to only allow chassis modifications to be properly inspected and tested by a professional welding company before being allowed on the road. Otherwise regulations for a joint profile should cover the contingencies of the weld being done by the lowest typical trained welders and their inspection and testing techniques. That is the safest way to cover it.

I think most of us, out of an abundance of caution, will add plates or a smaller tube on the inside going a significant length past the repair in both directions.

I have been doing special welding repairs for many years. Some of the people I learned my trade from did there trades in the 1920s. And I can say without a doubt that a "butt joint" is the correct way to join box sections and solid sections. All of the welding preparation and process involved are designed around the "butt joint". Because the only goal is to create a homogenous joint in the least amount of space with the minimum amount of distortion. There is no improved method.

Why not just test the various kinds of welded joints and observe if one outperforms the others?

I can see why they would want to use something other than verticle. It makes sense in my mind even if not mathmatically. If I were to do it though, I would use verticle cut welded then add a stiffener plate, probably somethig like a diamond shape, on each side. In my experience it's better to over build than not. If it ever breaks, it wont be at that joint provided the welds are proper.