I am finishing out my workshop and in the near future I will be pulling the engine our of my 1985 Mazda rx7 GSL-SE. I have been debating on what to use to pull engine. I could rent a engine crane, but I could but one from Harbor Freight for not many dollars more. However, taking an engine out is a rarity with me so it will just end up collecting dust in the corner for years after I finish this project. So looking around I can purchase a one ton manual hoist for about $70. This is the most cost effective way to go, but I am unsure about mounting it and the weight handling capability of the joists in my workshop.
The joust are made out of 2x6 and run 14’ the width of the building. There are no other supports. The rotary engine isn’t that heavy, it weighs in at under 500lbs. So, is a 2x6 joust strong enough to hold up 500lbs? Is there a simple way to calculate the weight capabilities? What would be the safest and best way to secure the host to the joist? The host has a large locking hook to mount to. I have tried finding the answer on the Web, but without much luck. Thanks.
You should never hang the host. It’s just impolite.
More seriously, if you’re dealing with typical (wood) architecture, I would be very hesitant to try and hoist a ton… even if the math seems to work out, you could be wrong. Fixing a structure is going to cost a lot more than renting or buying a tool (plus, you and your stuff get crushed… wait… if you get crushed you can pay with your life insurance!)
Well, that’s kind of what I was thinking however my net weight isn’t going to be any where near a ton, well under 750lbs. I would buy a ton hoist to have a safety margin in lifting capability. So, wood might not be the way to mount the hoist, but how should I do it? Try to reinforce the joist with a steel plate or just forget it and get the crane hoist?
As far as handing host, that’s what they get for hosting a sub-par party!
On the off chance that you meant that literally, he’s looking to lift a quarter of a ton.
Not being an architect type, I’ll leave my opinions out of that, but if you can buy a hoist, for $70, I’d probably do that and as soon as a friend asks to borrow it, tell them they can have it for $35…or $25 or whatever it’ll take to get it out of your garage forever (assuming you’re never going to use it again, keeping in mind you’ll always have a friend to borrow one from).
You can use a beam calculationsand load tablesto work it out. Multiple the result a few times for a safety factor. But it would be much easier for you to get the cherry picker engine hoist to do it. It’s mobile, they usually fold up or disassemble, and they make good general purpose hoists as well.
(I am a mechanical engineer. This is within my personal and professional experience. )
500 lbs straight down on the beam is not the load case you need to consider. That’s the best possible scenario, where you lift the engine straight up out of the car and it goes with no resistance.
The one where you need to worry about pulling the rafters down is the worst available scenario.
Let’s say the engine gets hung up on some little projection inside the engine bay. Let’s say you don’t notice for a few seconds and continue pulling up.
The worst that can happen is you end up inadvertently pulling the whole car up. At the very least, you should consider the case where you accidentally lift just the front end of the car. Think about what a load of 1000 or 2000 lbs would do.
Now, when you lift, it won’t be straight up. It’ll be at a minor angle. So you’ll have three components of the force, one along each axis. The total force in the chain will be load, divided by the cosine of the angle from the vertical, and you’ll have off-axis forces of that times the sine of that angle on the beam.
The least you should do is measure the unsupported length of the beam, measure the beam’s dimensions, go down a size, and see if the beam calculator tells you that the beam can handle the load. If you really want to get serious, you can do an analysis of the roof truss too, but I doubt that’ll be too much of a problem.
PS: The Harbor Freight “cherry picker” engine hoist isn’t bad, but it doesn’t last too long, maybe ten engine changes.
Thanks for the responses, tomorrow I will run the calculations. Amazing, I have come to the point in my life where I have stopped saying “hold my beer and watch this” and have started asking questions first.
Does an Rx7 engine really weight 500lbs? I thought it was closer to 200. Light enough that two people could conceivably pull it without the benefit of simple machines, but heavy enough that it’s a very bad idea. Maybe that’s with absolutely everything stripped off the block.
But sometimes ‘less fun’ is actually ‘more fun’ then trying to pick an engine up off the floor and hoping you didn’t break the concrete and glad you didn’t take the garage roof down with it.
The answer to this is a highly debated subject on the Mazda forums. Near as I can tell a short block weighs around 220lbs and a fully dressed engine a bit over 400lbs. But when lifting something I always trend to over estimate, figuring if I prepare for 500 and it’s only 300 I’m good.
Yeah, it is. But I have enough pain in my daily life without adding any more. Besides, my wife already thinks I’m a moron, so no need in enforcing that belief!
My “seat of the pants” calculator tells me that a 2x6 with a 14’ span ough to be able to safely bear 500 pounds at mid-span, but of course you’ll want to do the math for real.
If you do find that a single 2x6 is inadequate for the loads you are considering, you might solve the problem by buying one or two studs of taller cross section (say, 2x8 or 2x10), nailing them together, and then laying that assembly on top of, and perpendicular to, the 2x6 rafters. Your hoist would hang from this nice rigid crossbeam, which would distribute your load to two or more of the 2x6 rafters. You would just need to brace your crossbeam so it can’t fall over if it gets subjected to any side load (e.g. if you push sideways on the engine at any point).
You could reduce the span with supports (pillars) under the joist.
Put a couple of 4x4 posts 7 or 8 feet apart and mount the hoist between them.
You could even add an 8’ 2x6 to the mix.
The HB crane has the advantage of being able to be rolled out of the way instead of having to move the car when you want to set the engine down.
If you are taking the trans out with the engine it is likely the car will be jacked up and harder to move.
This is what I did when I needed to hoist an 1100 pound boat for working on the keel. Actually, I think I sistered a couple of 2x10 beams to the existing rafter and then supported it at each end with posts made up of two 2x4’s also sistered together. The span was less than 8 feet and my calculations indicated that I had probably a couple of tons of safety factor.
All told, it was 20-30 dollars of lumber – cheap insurance when you’re talking about your safety and the structural integrity of your man cave.
didn’t do any calculations or deep thought. and i see that what i typed agrees with MarkD as i now go back and read every message.
if you ceiling mounted a hoist you might put temporary supports under the joists on each side of the car; not just a 2x4 on a bottle jack but a 4x4 put in using wood shims.
Thanks to all that have responded. As usual my inquiry was answered promptly and in depth. Looking back at my post I have to apologize once again for my lack of proof reading and my tablet’s stupid auto-correct. I swear if I ever meet the guy who programmed my Toshiba’s tablet auto-correct I am going to kick him right in the yamsack. If it was a woman I will inquire here first for the appropriate action!
Also, I think it is probably OK to hang a host if transubstantiation has not been performed.
OK, enough yuks: Be really careful if these are truss rafters. They are not designed for point loads, and putting one in the wrong place can cause them to fail, and trying to beef them up can cause the load path to change so that they no longer handle the load they were designed for. Basically a truss rafter is designed to take roof/snow loads and transform them to compression loads in the walls, and tension load in the ceiling member. Weird things can happen, like it might be OK if you have a huge snow load on the roof, but you buckle the ceiling if the roof is dry.
If you have truss rafters, and can’t do the engineering analysis, then the only really safe way to do it is to add another complete support structure to the walls, and better to columns that don’t support the structure. You can use ordinary or engineered lumber for this, which has published load ratings.
If this was a one time thing I’d get some lumber and make a triangle frame hoist for a one time use. I’d use the lumber over again. Actually I’d weld and/or bolt something out of steel because I have the steel and the welder already. But three 4x4s and a few 2x4s for cross bracing is all you’d need.
I think the year was 71 or 72 when I went with some friends to help someone pull an engine out of a Chevy station wagon. He had hung a come-along from an old swing set to hoist it with. He had a bunch of rope wrapped around the engine to hook to the come along. As we pushed on the engine to try and get it free from the mounts he cranked on the come along. The rope strained and he shouted “Push” while he kept cranking. The engine didn’t move and he said “Rock it side to side, it’s stuck on the mounts”, and kept cranking. “Here it comes” he said as he strained on the lever. Then someone looked up and said “Uh…”. The cable was completely taken up and the swing set had just bent down to meet it. The engine hadn’t ever budged a millimeter. I heard he got a tow truck to come and pull it out with the hook.
