Home Made DIY Engine Crane Lifting Hoist (0.5 - 1 ton) - Page 1
Forum section: electronics / general

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 31, 2021, 03:49:13 pm
content: so i just like to echo the unlinked website here... in case members or someone out there searching for it...http://www.soasystem.com/eng/engineliftmore detailed info and dimesions are in the website, Cheers.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: November 02, 2021, 11:52:06 am
content: I like the simplicity of this design, but I do have a bit of doubt on the loops with which the hooks of the hoist is connected.It looks like those bent loops are just welded around their end.If those loops are rotated 90 degrees and their ends made a bit wider and longer, then you can weld them to the side of the tubes, which makes it a lot easier to make strong welds. This is "normal practice" in industry, but especially important for people who do not have much welding experience.If I were to make it myself, I would also put some extra thought into being able to take it apart by removing a few bolts, because it would be stored most of the time and only used occasionally.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 02, 2021, 03:11:10 pm
content: The rollers beneth the hoist also don't look very sturdy. Once the rollers collapes the dynamic force can bring down the rest even at a moderate load.The lever ratio looks like 1 :2.5 or so.In the current state I would not use it for more than some 100 kg.

author: PlainName
author_rank: Super Contributor
timestamp: November 03, 2021, 08:43:18 pm
content: Isn't there quite a lot of leverage in the vertical member which might twist the horizontal bar (or even break the welds)? Perhaps some bracing arms on the side opposite the car would fix that.

author: MarkF
author_rank: Super Contributor
timestamp: November 04, 2021, 04:27:29 pm
content: Quote from: dunkemhigh on November 03, 2021, 08:43:18 pmI echo your concern.Wouldn't a solid horizontal bar on the top be better?

author: Kleinstein
author_rank: Super Contributor
timestamp: November 04, 2021, 05:12:46 pm
content: The one piece horizontal and 2 verticals looks better.With the small rollers even a small hole / groove in the ground could give a bumpy ride and quite some dynamic load. The twist bar suspension may than actually be a good thing. It still needs strong welds.

author: PlainName
author_rank: Super Contributor
timestamp: November 04, 2021, 07:42:38 pm
content: QuoteNoI meant the bottom bar, across the two 'feet'. The leverage on that is the diagonal of the vertical bar and the horizontal lift bar. Pick up a decent motor and there is a significant twisting of the welds, not to mention the bar itself.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 04, 2021, 07:49:35 pm
content: The leverage for the twist would be only the horizontal part, as gravity is usually going down. So the vertical part does not really matter.This is still quite a long lever and a relatively small cross section for the welds. The twist in the bar itself is more like a good thing acting as a spring to provide some suspension. The welds are usually less stable than the bar itself.

author: Alti
author_rank: Frequent Contributor
timestamp: November 04, 2021, 08:23:22 pm
content: Don't you think it is too short to lift the drivetrain above front belt? The purpose of it is to drag drivetrain out of the car, isn't it? Or should the front belt be disassembled for the whole operation?

author: MarkF
author_rank: Super Contributor
timestamp: November 04, 2021, 08:46:57 pm
content: Looking at some commercial engine hoists, they have diagonal supports for the vertical post also.

author: james_s
author_rank: Super Contributor
timestamp: November 04, 2021, 08:57:02 pm
content: I'm all for DIY projects, but when Harbor Freight sells a 1 ton engine hoist for just over $200 building one seems kind of like building a screwdriver. Sure you can do it, but unless the material is free you're not saving anything.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 05, 2021, 08:25:30 am
content: Quote from: dunkemhigh on November 03, 2021, 08:43:18 pmditto. your intuition seems to reflect reality.. after finishing the crane and putting it to work.. at just over 200kg of load (i have heavy duty weight scale connected), the lower horizontal arm supporting the vertical arm started to buckle quite badly due to torsional force from vertical arm, so i abort the job, pull back the vertical arm back to its position "debuckle" the supporting arm and add diagonal supporting arms (attached picture) and now i'm confident and tested it can lift 200 or maybe a little bit more kg of load with no problem. i just dont have time to update in the drawing and repost the correction, thinking everybody that going to do this soon will realize the same (lazy me sorry for that)...btw i have full confidence on my welding joint strength. i'm not a good welder but i can weld as many metal and layers as i want to since one box of rods only cost like $5 and i only use not even half or quarter of them in each of my small projects.Quote from: Doctorandus_P on November 02, 2021, 11:52:06 amthe loops were bought ready made from hardware store (i have few stocks so i dont have to buy), they are meant to hang ceiling fan. prewelded to a metal base with 2 holes on it, my part is to weld that base to the hoist, the loops buckled a little bit from my observation during the work, but doesnt really concerning me, i can redo and find much thicker loop, or made my self one, and again, my weld joint is not the weak one.Quote from: Kleinstein on November 02, 2021, 03:11:10 pmyou are right about the small rollers. the front plastic rollers crushed during the work, they are also from my stock, so obviously they are not for this kind of load. although not a sudden crush, i replaced the front rollers with more sturdy one. the rear side seems to hold pretty well, so no replacement needed yet. i tested 200kg+ of "near" static load but you are right i need to be carefull when moving load around. i'm more concern about the material strength, ie the hollow rectangular tube, they are just 2" x 4" 2.3mm thickness, they can buckle first long before my weld joints fail.Quote from: james_s on November 04, 2021, 08:57:02 pmyou are right, but thats not considering the shipping cost. i designed and measured the dimension so i can use only one bar of rect hollow tube (6m length) and it costs $40, thats why i didnt implement double vertical arm and have to do fancy "double bone" lifting arm, because otherwise it will exceed 6m length and i have to buy 2qty of rect tubes and keep most of the extra unused length in my limited store, not to mention double the cost. the most expensive part though is the 2T lifting hoist (chain block unit) $80+ but i'm thinking that i can use for something else, hang it on a house roof and lift something much bigger, for example. with ready made hoist, i cant repurpose the hydraulic jack welded into it.ps: dont mind the painting job. they are hand painted obviously and i'm not sure why the paint quality / brand is so fucked up shrink badly like that, or maybe i was too lazy not to put undercoat before painting. previously i painted with other brand directly to the metal without such problem.

author: coppercone2
author_rank: Super Contributor
timestamp: November 10, 2021, 12:15:37 am
content: The company might occasionally sell you steel that is greased more heavily then the other steel which was beyond what the paint can handle. The problem is cheap steel cleaning is somewhat painful. You probobly need more scrubbing/de greasing. I personally found some of the 'cheap' degreasing methods have shameful performance.. wish I had a sand blasting cabinet. I do a full strip using a black foam paint strip wheel.. but its labor intensive and you need a slow die grinder for the method to be any good (using it in a drill is shit).. but then I also hose stuff down in alcohol, scrub with brillo, and rinse.. with lots of alcohol.. so that ends up not being so cheap when you are trying to count every penny.. thats why these projects are not as popular as you would think... hard to make it look niceacetone, break cleaner, etc.. also work, often better, but sometimes the smell, higher hazard, and increased cost is not worth it. Acetone burns like crazy compared to alcohol if you are degreasing large stuffbut the important thing is making sure the welds dont get bad and that the metal is not punctured by rust.. but given your climate..... I don't think you have any thing to worry aboutif I lived near the desert I would probobly be driving around with flat bars dragging behind my car to clean em up lol.. if it does not trash the car then it might result in rather clean parts that need minimum work.Something to note about outdoor steel structures is that if you get water ingress and I guess it rusts itself shut, it can end up being pressurized with water. I have seen videos of hand railings squirting water when you drill into them.. so be careful using corded tools when you are modifying a outdoor steel structure, as not to get water into the motor (obviously dangerous). And of course if you start boiling rust-sealed water by say trying to torch cut it, you might get a nasty steam surprise.If you grind your welds and finish the surface better obviously it will have a stronger immunity to rust but then you need to buy lots of abrasive stuff that obviously can incur a cost overrunThe wrinkling I often see comes from something akin to milk forming a skin when you heat it to make food. I mostly see it from what I understand to be primer-paint or clearcoat-paint solvent incompatibility, i.e. I believe paint manufacturers make the bottom coat require a more aggressive primer then the top coat, so when the bottom coat dries, you can put the top coat on, and the top coat will not make the bottom coat 'soggy' since the solvent does not effect it so much. Kind of like wet bread. But when the paint is over grease, the bottom does not adhere, so it forms a skin, like milk surface, that dries out and wrinkles since there is less cohesion? of the material. Its not really been explained to me properly by a scientist its just kinda what I came up with. It also shows up if you paint outside of the recoat window, i.e. with epoxy paint if you put a 2nd coat on it after its been allowed to cure for more then a hour or so, it will wrinkle, but if you wait 1-2 months, you can recoat it.. something I learned since I like the look of appliance epoxy on welded steel. It says so on the can but it does not tell you what happens when you ignore the warning.. perhaps after 1 hour it becomes a semi-liquid which is 'sensitive', i.e. things stop mixing/making solutions and start being prone to 'mechanical damage' from rapid composition changes (something along the line of rapid solvent diffusion into a 'thirsty' drying layer causing disturbances seems logical..)

author: floobydust
author_rank: Super Contributor
timestamp: November 10, 2021, 04:48:19 am
content: Having used engine hoists on big V8's, this design is not good:a single small Gr.5 bolt for the hinge- no calculations of shear force on it. It's gonna break...The vertical member has a lot of torque on it, or bending moment as the mecE's call it. I wouldn't expect any weld to survive.

author: coppercone2
author_rank: Super Contributor
timestamp: November 10, 2021, 04:55:16 am
content: thats a good point, that should be some kinda heavy metal pinwhat if you weld triangle plates that go to the top from the bottom instead of the 2 rods. Unfortunately it would weigh a ton also

author: floobydust
author_rank: Super Contributor
timestamp: November 10, 2021, 05:36:12 am
content: It might be a copycat error, hoists usually have a hydraulic cylinder thus the load is shared between two bolts at F and E.I would think torque at C is too much without B-D or H.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 10, 2021, 02:12:31 pm
content: The bolts at E anf F don't share the load - they see opposide directions, so it is more that the load at E add to the load. So the bold at F will see about 1.5 times the load.In the original design the single bold will see about 3-3.5 times the load, as the force from the chain will add. So ideally the lever to the back should be longer.

author: floobydust
author_rank: Super Contributor
timestamp: November 10, 2021, 05:12:59 pm
content: It's been decades since I've drawn free-body diagrams in eng. mechanics.The top member is like a see-saw, with 3.5x factor at the short end. With a 500lb motor, that's 1,744lbs tension for the chain hoist, total reaction 2,244lbs at the bolt. They are summed is what I meant. I don't have exact dimensions.I agree the short end could be longer. This design multiplies the force a lot to have very little displacement but stresses the frame too much.Those U-bolts better be for just holding things at rest. You'd have to loop the chain around the bottom.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 11, 2021, 07:08:04 pm
content: Quote from: floobydust on November 10, 2021, 05:12:59 pmi can draw them for you but its 3AM now and i'm about to go to bed. anyway fwiw, doing full analysis required me not just FBD, but also looking up what type of steel the rect bar is using, and then find the ASTM table for maximum shear/bending moment/etc of that particular steel and to the exact dimension and thickness. its quite an exercise. i wanted a quick job, so i assumed rigid undestructible rect bar, which i was plainly wrong (if i have to blame something else other than me, then i should blame the economy), and oversized weld joints and bolt nut hinge to some ballpark aka experience (or inexperience), its about 1cm diameter much thicker than the diameter of the 2T block chain ring, if it should fail at some shear stress of less than 1T, then it must be some fucked up hunglow steel mixed with sand.Quote from: coppercone2 on November 10, 2021, 12:15:37 amyou have a good point on degreasing the surface before painting which i overlooked, but unfortunately most of the time, paint will be on my last list of priority. if not because steel rusts, i will not paint it

author: coppercone2
author_rank: Super Contributor
timestamp: November 11, 2021, 08:10:10 pm
content: yeah, in these cost constrained situations I wonder if you can get something clean enough for painting using a simple soap scrub or something like that. The post-wash corrosion is not necessarily a terrible thing depending on what paint you choose, so long its oil free.. the rust texture if its fine and clean might make the paint adhere better in some cases I think, but it needs to be like a smooth even layer.And keep in mind this, you can burn the metal clean with fire before painting, so long its a clean flame. Some of the best performance I got from painted parts are zinc-casting 'door mats grates', I cleaned the surface with no residue degreaser, burned it with a torch while it was hanging until there looked to be no more emissions from the metal (and it was toasty), then primer/paint+clearcoat, and it has been lying on the ground near my front steps in snow, wind, ice, rain and dirty shoes for 4 years and the paint job is still acceptable. I expected 1 year from it before it was too nasty. The factory paint job started comming off in large patches, my paint job looks like it only has damage from impacts/abrasion, no big flakes. I spent too long to restore a 15$ object but the durability is impressive.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 11, 2021, 10:24:42 pm
content: i forgot to mention, since alcohol/spirit/ethanol/thinner et al are considered rare earth material to me (expensive and sold in small qty), gasoline is cheap alternative and quite effective and quick time at removing those grease. and fyi i have complete tool for spray paint and have painted automotive grade paint on some equipments i've built, but for this project, i was too lazy to setup my spray paint tools since its only so the metal dont rust in the open space exposed to rain and sun where i put it, not to mention the cost and time needed for proper paint. i bought a used outboard few days ago in poor condition and i'm currently polishing and putting putty and compound to hide scratches and scars before doing another proper automotive grade paint on it.. when aesthetic is in mind, we get to do it properly, cheers