In my humble opinion sir, you are a free man. Leave this court and continue your worthy crusade to educate us poor souls. Voice of reason, common sense and experience. Power to you Sire!
Excellent analysis as always. Have been jacking up 4x4s for over 40 years and always leave the jack in contact with the axle once lowered onto stands. Interesting analysis on the brake disc though it's something I don't do habitually as not all discs are created equal. I once had failure of a disc on a jeep (while driving) because the manufacturer in their cost cutting wisdom used pressed steel centres with the cast disc welded to it and readily prone to rust. A truly horrible idea.
I am the first to admit that putting a support under the brake rotor is a bit sloppy but very convenient If I was actually working under the vehicle instead of standing outside it I'd put a support under the axle.itself. What a horror story about theJeep's disk brake.
Hello, this is Todd , I love ur correspondence and the factual information from an extremely intelligent and competent individual such as yourself. At some point, I would like to see a comparison analysis of shear, bending moment, and radial forces, as far as repairs on auto frames or modifications, using welding vs. the proper application of riveting.. joint tensile strength, shear , bending moment, and spiral twist flex loads. Thanku for ur time, look forward to a proven and proper analysis.
My two penneth. If I’m using a jack on a corner which weighs abit over half ton. I’ll use a 3 ton trolley jack or a four or six ton bottle jack. I’ll add support, either an axle stand or decent wood blocks with the largest and widest at the bottom and lower onto that. Then I tension the jack so it’s lifted the load by a fraction and now I have the solid support ready to “ catch” the jack if the jack fails or subsides. Also a good test to see if your jack is leaking by, where after an afternoon or day , is that fractional lift still there? All my axle stands are second hand but of very stout steel construction and by guessing I’d say are rated for many times the load I will ever give them. That means I’m confident to rely on them when underneath my 109. Like a Victorian viaduct, extremely over engineered.
Only problem using the brake disk as support is that without the wheel it’s only attached to the hub with a small locating screw so any unexpected sideways load and it ‘could’ pop off. I’d use suitably sized wood over axle stands anyday esp if you have both wheels off as they will give better lateral stability ( suitably sized) than the rather narrow axle stand geometry.
That's a very good point, exactly the sort of comment I was hoping to receive. I would add that I would never do this is if the other wheel on the axle was off at the same time and you have given a good reason not to.
@@defendermodsandtravels the other aspect that can be drawn from the comment by John Griffen is that this is why two independent processes are much prefered to the pure checking of calculations process. Sometimes it is what is not calculated that bites us ((in the case of the Discovery 1, I think the disk is well bolted, which is quite unusual compared to other more modern cars)) but for my part big brownie points for thinking outside the box John G
Second comment re axle stands. I have three pairs, two of which are high lift, and one of those is ex NATO I never extend them more than a couple of holes, as it looks increasingly precarious. Always conscious of the triangular foot and the potential to tip, That’s why a two foot piece of sleeper with another on top then a 6” square oak post section on top,has such a massive footprint in all directions that with weight on, is not going to move anywhere.
In the 20 years ive been working on or around cars I always leave the jack in place...why wouldn't you unless it's in the way? It can't hurt and if anything does shift its extra support
Totally agree however the troll who criticised my earlier video has other views. It's very difficult to envisage a situation where leaving the jack in place can jeopardise safety provided there's another independent means of support. However I can imagine situations where an axle stand might fail and a jack wouldn't (e.g. sinking into the ground, which a jack is unlikely to do because of its larger base area). Thanks for the comment.
Excellent analysis and explainatio - in my opinion a bit of overkill since very few are able to follow your hard evidence in the first place. I also believe that all RU-vid videos are suggestive and in no way instructions for which the one who goes through the troubles of making them be held responsible! Especially since there is NO agreement between the viewer and the creator! When I first heard of the rantings that came your way my thoughts were immediately "don't let it bother you". An oak doesn't care if a bore rubs his back on it!
You are right that it was probably overkill but I had to kill the suggestion that I was causing the deaths of viewers around the world stone dead. I am a Chartered Engineer and must abide by a code of conduct and could get ito trouble even through these hobby videos. As for my critic? He claims to be an expert in these matters having worked in a mechanical environment for many years, whatever that means. I now have the evidence to engage in a constructive discussion should anyone else critcise my working practices.
I can attest to using dunnage. I once used a jackstand similar to the blue one in this video, on very hardpacked gravel, when the vehicle suddenly shifted as the jackstand sunk into what I thought was a safely hard surface. The only thing that saved me was my habit of putting the removed tires under the vehicle as a safety stop. After that, if I needed to use jackstands on other than concrete surfaces I would put a square of plywood and/or other dunnage under the jackstand.
And therein lies the difference between a real Engineer and someone claiming to be an engineer - just because maybe their work title includes the word "engineer". It happens to those who don't know, that they don't know!
In the UK there's a system of accreditation leading to the title Chartered Engineer, however anyone can call themselves an engineer and it causes much confusion. By contrast only Chartered Architects are allowed to trade as architects. I was amused to see that the guy who came to empty my sewage plant calls himself an engineer, whereas in reality he's just a dude driving a sludge gulper :-)
i think if you've made it to this point you're doing something right. i would absolutely ignore people that leave daft comments . keep up the good work
you've put an admirable amount of effort into this assessment of your practices for a comment that probably should have been disregarded. but to ad to the conversation the only reason i personally stay away from supporting a vehicle on its rotors is the increased risk of it rolling, but if you're supporting only one side of the vehicle that risk seems rather low.
You are right although if you see the depth of the indentation made by the rotor in the dunnage you will realise that there'll be considerable rolling resistance. For it to roll either of the following conditions must be met. 1) The mechanic forgets to chock the other wheels, or 2) the chocks get removed somehow. Oh yes, the vehicle needs to be on a slope too (which is a total no no when jacking). The chance is pretty low although, having worked in offshore construction yards for years, I understand how accidents can happen when they shouldn't. I leave it to the viewer to decide how they wish to support their own vehicles. And yes it was a lot of work but I couldn't leave the critic's comments (about causing fatal accidents around the world) go unchallenged.
I started watching this thinking (and yes, im aware no-one asked lol) I watched that video, and didnt have any problems with the way you worked, especially not with the wood blocks, and I have no issue with leaving a jack support as a fail safe for the very reasons you go one about. Then you started on about the wood blocks, or dunnage to be more precise, and I was like ok good. lol.I do appreciate that you took the comment as well as safety seriously, rather than scoffing it off. I think most people dont quite appreciate the qualities of wood, being a natural material and somehow mysterious to many. While I wouldn't normally put wood or support directly on the disc (dont normally have a need to) if I were going to support it it would be with wood only, I wouldn't ever use a steel jack stand for that purpose, basically for the same reasons you point out here. While I dont expect an answer, I do have a question regarding your analysis: Would there be a difference in the load at the moment of impact, IE shock and would that make a difference? Clearly using wood means it softened that but id be curious if the numbers would be higher for a moment and if the time length of that shock load number mattered to the integrity of the iron? This is purely theoretical as a question mind you and I hope im making sense.
Hi Erich thanks for the comment. I am first to admit it's a bit sloppy to support the axle via the brake rotor. If I had supported the axle tube instead it would have taken 3 - 4 of those wooden blocks on their flat sides (maintaining the same height to width ratio of the pile). I would either have needed to lie on my front to manoeuvre them into place, exposing myself to the risk of jack failure, or to have devised a way of pushing the pile under the axle without going under the vehicle myself. In reality it's just easier to stick a block under the brake disk without exposing myself to risk. Lowering the axle onto the wooden block has no measurable dynamic effects. If I had dropped it from a considerable height onto a really hard surface it'd be a different matter. I hope that helps.
Well done, well done. I find it comical, honestly, how this internet age has made so many people with such little experience able to feel like superior experts on so many matters. The most blaring current example being, I seem to recall a certain submersible manufacturer who recently stated that the experienced submariners all seemed to be old, white military vets, and he wanted his project to reflect a younger, more diverse team. God rest him. There is good reason to respect one's elders, which goes well beyond age. While todsy one can certainly learn a lot about a lot online, and definitely find more than enough resource to get started, experience counts far more than youtube self-education. It's always wise to find an experienced mentor in any given subject.
I have been bemused at the number of videos about the implosion of the Titan mini-sub with many so-called experts popping up, most of whom clearly know little. Although I have some knowledge of externally pressurised cylinders (tubular steel offshore platforms are made from these) I don't know about subs nor carbon fibre so I am steering well clear of the subject. Don't expect any videos from me! Engineering progress often comes in uneven steps with engineers periodically overreaching themselves, accidents occur and there's a period of retrenchment before the the technology moves forward again. This is what happened with steel box girder bridges in the late 60s / early 70s. The CEO of OceanGate appears to have broken all the rules.. It is fundamental that every structure, ship, aircraft, vehicle, industrial process, whatever has to be approved by a competent independent body. It seems that the Titan wasn't in Class (i.e. approved by a Classification Society) and look at what happened. I expect there will be period of conservatism in the design of these extreme depth subs before the technology moves forward again.
Correction to the above: I may actually do a short video on the failure of the Titan hull just to debunk some of the wild rumours and claims being made on YT.
@@defendermodsandtravels I'd be interested in your take on it. I have my own ideas, but the sum of my experience with submersibles is that I once rode one down to about 100M. Any of my own engineering experience with pressure vessels had to do with working on 100KPSI waterjet pumps. I imagine holding pressure outside is a whole different animal from holding pressure inside.
@@soundmindtv2911 There are many whacky ideas out there. One dude who claims to be an engineer reckons it's a form of brittle fracture emanating from a pre-existing flaw when the hull is actually in tri-axial compression and the crack won't go anywhere. Another joker claims that the air inside the imploding hull heated to a higher temperature than the sun and the occupants were vapourised! Sure the air would heat up under adiabatic compression but I think that hypothesis is out by orders of magnitude. I will check it out when I return from my present travels.. I have done some gentle reading on failure theories for carbon fibre composites and it's clearly a complex subject with little consensus of opinion. Under circumstances like this one designs with a generous FOS. There's a simililar situation on the grouted pile connections on steel offshore structures and the recommended FOS is 6. My guess is that the sub's desgners used an FOS in the range 1.5 - 2. I'ĺl continue look into this.
Do me one favour don’t respond to the negativity, once you make a video specifically responding they’ve won. All these type people want is for you to waste your times educating keyboard warriors who already know it all. Excellent videos
You are probably right but one thing I have learned over the years is not to be too hasty in dismissing criticism just in case your critic has a valid point. I have seen a number of avoidable accidents on construction yards where warning signs were ignored.
I work the same way as you, because I also prefer safety. Don't sweat the troll BS. It's just nonsense from someone who isn't prepared to address the underlying internal problem that leads them to engage in recreational outrage.