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View Full Version : OTish Adding a swing crane to a vehicle hoist?



vpt
01-08-2011, 12:47 PM
So I finished my ceiling drywall extravaganza that some of you may have seen in another thread.

Anyhow I have a rotary 10K# overhead two post A-symmetrical lift. I have been thinking of adding a crane to the one post that would be able to swing 180 degrees. The idea for the crane is that I could use it for pulling motors on cars, holding up heavy parts in engine bays, etc. The idea in my head is for the crane to be able to swing like I said and also have the 'head' of the crane slide in and out (toward and away from the hoist post). I would be looking at the same weight that a cherry picker would handle (up to 1ton).

My concern about the deal is if it is safe to have the weight on the end of the crane swung around to the outside of the post? Obviously a vehicle hoist is designed to have the weight between the posts. But what I am thinking is if the post is designed to have 5000# to the inside of the post it should be alright to have up to 2000# on the opposite side of the post.

What are your guys thoughts? Anyone ever seen anything like this?

It would be nice to have an engine crane without the 'feet' of the cherry picker under the vehicle and whatnot.


This is the hoist, the crane would be going on the left post.

http://img239.imageshack.us/img239/4600/everything236ig5.jpg

john11668
01-08-2011, 02:12 PM
I think the crane would impose bending forces on the post far in excess of its design especially with a two poster . The pressings are probably up to the job but wont have a lot in hand .
Would you not be better rigging a small overhead gantry and drop the vehicle out from under the engine. You might have to consider how the balance of the vehicle would change as you take the lump out.

vpt
01-08-2011, 02:37 PM
Sorry I ment the crane would be on the right post in the pic.


The problem with an overhead is the space the beam would take up. Right now I lift cars right up to the ceiling of the shop so there is no room for a beam of any kind to be up there. With the lift it is easier to drop the motors out the bottom of vehicles which the cherry picker also doesn't work for. No problem balancing vehicles while pulling heavy chunks out of them, I have plenty of practice with it, understand what I am doing, and take into consideration what I will be doing when positioning the lift arms under the vehicle the first time.

More than I can say for the local ford dealership that dropped my first truck off their lift after disconnecting the rear end from the truck.

justanengineer
01-08-2011, 02:38 PM
I agree wholeheartedly with john about the lift possible bending. It only takes dropping one vehicle off a lift to make you appreciate them 1000x more-never done it but had to help fix the situation after. Is there a reason you would want to pull an engine from a vehicle on a lift? How would you control it or do other work necessary from the top with it up there? The only time I have ever done anything similar is when removing the entire front end from a unibody vehicle for work, but in doing that the vehicle is lifted off of the engine/trans/front suspension which stays on the ground. I believe pulling an engine with the vehicle up would likely be dangerous should the engine hang up on anything and/or move suddenly as happens quite often as it could knock the vehicle off the lift. If you want safety and comfort when pulling engines - use a pit or grease rack and a regular engine hoist.

Just my $0.02

vpt
01-08-2011, 03:11 PM
The crane would be helpful for letting the engine down after unbolting it from the car. It also would come in handy for heavy items such as complete diesel intakes that can weight 75-100 pounds. They could be lowered onto the engine with ease and precision instead of muscling them up into the engine bay and guessing where it is going when dropping it onto the engine. Could be used for lifting heads on and off motors, holding up all steel bumpers, x-members, etc. Just simply anything heavy that needs to be held in place perfectly for bolting.

I feel pits are the most dangerous thing ever for any shop. Not only for the owner walking around the shop day in and day out but for anyone that walks into a shop expectantly not knowing there is a gaping hole in the middle of the shop.

I use a rack with wheels to drop motors/transmissions onto now but it doesn't work as good for aligning the assembly back up going back into a vehicle. Always some corner or the whole assembly needs to be lifted to line up to mounts and with the engine under the car it is impossible to get a cherry picker over the motor.



From what I read the rotary posts are single piece formed 1/4" steel. Pretty much identical to the posts I see used for shop cranes however they are open on one side which I understand make the post weaker than a complete post.

How about reinforcing the one post to take the forces of the crane? Like say adding a H beam from the floor to the top of the lift. Possibly adding in an extension of the floor plate and a couple or few more anchor bolts into the cement.

rohart
01-08-2011, 04:18 PM
If you dropped a car with its engine hanging, the weight distribution of the vehicle would change instantly. I can see the vehicle dropping trunk downwards.

Are the two posts connected at the top ? If they were, you could at least share the bending out moment of the crane post with the other post.

The moment about the base that each post is expected to take is half the weight of the car at a lever arm of about two feet. If you start hanging further out than that, and in the wrong direction too, I see trouble.

And it would be much better to take some of the moment off the post at the top, than try to get the concrete to take it. This is because the lever arm (again) is ten feet long if you take it at the top, but only a couple of feet if you fabricate an extra bracket at ground level.

vpt
01-08-2011, 04:51 PM
Yes the posts are connected at the tops with eachother. The arms are unequal lengths because the lift is an A-semmetrical lift. the front arms around about 3 feet long fully extended and the rear arms are about 5-6 feet fully extended.

The total length the crane would be estimated 6 feet. Obviously I would use judgement of what weight I would be lifting with the crane and how far out to go with the head of the crane.

http://i303.photobucket.com/albums/nn157/devlish/2010/GLH%20Fix/GLHFix03.jpg

The arms all the way in:
http://img519.imageshack.us/img519/8079/project2car012rl3.jpg

I'll see if I can find a pic with the arms fully extended. Dropping motors, rear ends, transmissions, etc. while a vehicle is on the lift is nothing new to me. No worries on vehicle balance safety there.

Gravy
01-08-2011, 07:45 PM
VPT,

How about using a chain hoist and trolley rolling on an I-beam that is supported crossways on arms projecting forward from the top of each post? The loads on the posts would be in line with the original design parameter. It would just be like a slightly front-heavy car - no additional twisting or side loads.

Evan
01-08-2011, 08:39 PM
I ran a quick calculation on the idea. Assume a six foot long swing arm with 400 lbs on the end. It will produce a torque at the other end of 2700 foot lbs.

Put in an overhead stay to the 3 foot point cuts the torque moment but then produces an end thrust of around 300 lbs. The stay will have to be able to support at least a ton for safety margin. All this assumes the swing arm is plenty strong which adds another hundred lbs to the load.

v860rich
01-08-2011, 08:59 PM
Your lift looks to be about the same as mine, except mine is a symertrical. If you keep the crane attached below where the upper lighter weight section of the verticle post is I can not see a problem.
Most of the cars and trucks that have to have thier engines removed from below are not that heavy and neither are their driveline components.
Sounds like a good idea to me.

THANX RICH

People say I'm getting crankier as I get older. That's not it. I just find I enjoy annoying people a lot more now. Especially younger people!

vpt
01-08-2011, 09:01 PM
Torque of 2700 pounds at the single point of where the crane met the post right? If the actual top mounting point of the crane was higher than wherethe crane arm met the post the force should be reduced is it not?

So right now say I have a 9000# truck on the hoist and the rear arms are extended all the way out to their 5-6' point and are taking their 1/4 of the weight of the truck which would be 2250# 6 feet out from the post, what is the torque value at the post then?

Besides the possibility of the post twisting under load I find it hard to believe that the post can't take the load. A load that it is already suporting in the vehicle threw the arms of the lift.

vpt
01-08-2011, 09:03 PM
Your lift looks to be about the same as mine, except mine is a symertrical. If you keep the crane attached below where the upper lighter weight section of the verticle post is I can not see a problem.
Most of the cars and trucks that have to have thier engines removed from below are not that heavy and neither are their driveline components.
Sounds like a good idea to me.

THANX RICH

People say I'm getting crankier as I get older. That's not it. I just find I enjoy annoying people a lot more now. Especially younger people!


Yes I would definitely keep the crane on the lower portion of the lift. That upper portion seems like it doesn't do much more than support the equalization (correct terminology?) cables.

Evan
01-09-2011, 12:18 AM
Torque of 2700 pounds at the single point of where the crane met the post right? If the actual top mounting point of the crane was higher than wherethe crane arm met the post the force should be reduced is it not?

So right now say I have a 9000# truck on the hoist and the rear arms are extended all the way out to their 5-6' point and are taking their 1/4 of the weight of the truck which would be 2250# 6 feet out from the post, what is the torque value at the post then?


The 2700 foot lbs is produced when you have an arm supported only at one end with a load at the other. It is trying to twist the arm around the support point downward. Naturally it is impossible to mount the arm to an infinitely small point so the load will be distributed over some distance depending on how you build it. It the swing arm were attached to a healthy swivel pin with bearing supports spaced one foot apart on the post then the torque trying to bend the post would be 2700 lbs pushing in on the bottom bearing and 2700 lbs pulling out on the top bearing. If you make the bearings 2 feet apart the the numbers are reduced by half as long as the support point for the arm is centred between the bearings.

For your second question, the load is balanced. The only torque value on the posts is produced by the deflection of the horizontal members. I can't calculate that without knowing the material, the section shape, the section dimensions and thickness.

The lift posts fall into the category known as slender columns. When weight is applied to a slender column the resonant frequency of the column falls. That is the oscillation period of the column when it is disturbed laterally. It is equivalent to a reduction in stiffness. The greater the load the lower the resonant frequency and the lower the effective stiffness. At any particular value of load there will be some value of lateral force that will cause the column to bend enough that it will pass a point where the load changes to compression on one side and tension on the other side instead of being compression on the entire section.

That point marks a transition from essentially linear behaviour to extremely non linear changes in the internal strains on the material. It is a point of instability. Once the beam goes even slightly past that point the strains almost instantly change enough to cause failure and the beam buckles. The values at which this happens for any particular material and section are nearly impossible to calculate accurately so empirically derived values are used that have been determined by experiment.

Safety margins are estimated by using rules of thumb for any particular design and testing carried out to make sure that the design rules are valid. The maximum load capacity of the hoist is based solely on the weight being carried on the hoist as intended. That produces far lower torque moments than would hanging a hoist off the side of one of the supports.

Without doing a full analysis of the entire assembly it is impossible to predict what the result would be. There is a very distinct chance that it would cause the hoist to buckle as the torque loads imposed are more likely to cause buckling than a simple lateral force.

I would not trust that hoist to handle an engine hanging on the end of a six foot arm. My personal experienced based gut feel is that it would fail or be dangerously close to failure. If it does fail you will have no more than a tenth of a second warning. It will fail almost instantly. All it might take is a nice jerk from the engine shifting on it's chain or something similar to momentarily double the instantaneous load. Gravity will do the rest.

Ian B
01-09-2011, 06:11 AM
VPT,

As this is a 2 post car lift, the posts are designed to take a significant bending load. It's not a 4 post, where the vehicle's on a sort of pallet, and the columns are in pure compression. You're right when you say the individual posts are designed to support an assymetric load of 5,000lbs each (plus a hefty safety factor).

If you build a swing crane onto one post (and spread the load in a similar manner to the existing sliders), then as you start to lift the engine, the load on the car supports decreases. It'll put more load on one post than the other, but I don't think that car weighs 5 tons, so you're unlikely to be anywhere near the lift's capacity.

The back supports are so far back that there's no realistic chance of the car falling off boot (trunk) first - even without an engine & gearbox, the CG must still be between the front & back support points.

The only thing I'd watch for is the fact that the slider will be supporting a load in front of the post (rather than between them as at present). This will mean the slider will try to rotate and spread the sides of the post. A couple of hefty steel clamps around the slider & post might not be a bad idea.

Once the engine has been lifted, don't be tempted to swing it forwards and outwards - lift it, drop the car, pull it out backwards and drop the engine straight down.

Ian

Evan
01-09-2011, 09:44 AM
Once the engine has been lifted, don't be tempted to swing it forwards and outwards - lift it, drop the car, pull it out backwards and drop the engine straight down.



How do you plan on preventing that from happening? You cannot count on the operator to simply know that shouldn't be done. Any number of scenarios could arise where it may happen regardless of previous instructions. Perhaps a helpful friend swings it out while VPT is looking for some tool.

That sort of restriction on use is never an acceptable way to provide safety. The system must be able to operate with sufficient safety margin in all configurations in which it may be reasonably used. Not swinging a load on a swinging crane does not meet that criteria.

This is not a situation where "common sense" or eyeball judgement is adequate to make an accurate estimate of the capability of the existing structure to handle the load. Since somebodies life may depend on it you need to be certain. Obviously, by the limitation you impose, you are not.

vpt
01-09-2011, 10:05 AM
I'll have to take a closer look at the posts and get some good pictures of everything to analyze.

After reading what everyone has posted and thinking about it the real threat is the post twisting with a load hanging off one point of the post. Right now I think to over come this I would have to hinge the crane on a separate beam the full height of the post and then mount that beam to the post of the lift from floor to top. This way there will be no twisting force on the post of the lift but a more distributed even pull on the post much like it would see from its lift arms now. I will look into boxing in the upper part of the post to prevent it from expanding and flexing.

I will also see if I can rig up a pole/beam off the post to do some tests with weight and see how the post reacts to certain mounting points and forces before I start building anything.


For the record I would never be using the crane to lift anything like a complete 7.3 diesel out of a truck. when I originally said I would like it to take a ton of weight that was a little far fetched. A complete 7.3 is 1000# and I wouldn't use it for that so I am thinking the most weight the crane would ever see would be a complete 4cyl engine and trans (about 600#). I always use common sense with weight and vehicles especially when stuff is going to be over my head, arms, etc. I would make absolutely sure I would know the limits of anything I am using before I use it. I have turned down work before because the truck was very near the limit of my lift and I didn't want to take any chances with it.

I appreciate all the input and insight from all of you!

vpt
01-09-2011, 10:10 AM
How do you plan on preventing that from happening? You cannot count on the operator to simply know that shouldn't be done. Any number of scenarios could arise where it may happen regardless of previous instructions. Perhaps a helpful friend swings it out while VPT is looking for some tool.

That sort of restriction on use is never an acceptable way to provide safety. The system must be able to operate with sufficient safety margin in all configurations in which it may be reasonably used. Not swinging a load on a swinging crane does not meet that criteria.

This is not a situation where "common sense" or eyeball judgement is adequate to make an accurate estimate of the capability of the existing structure to handle the load. Since somebodies life may depend on it you need to be certain. Obviously, by the limitation you impose, you are not.



Yeah I would not do anything like that. If I know it couldn't handle it at full extension or any position I wouldn't use it. I wouldn't be pushing any limitations with the crane, I would only use it for what I know it can safely handle. Any weight or situation that I would feel would be towards its limits I wouldn't be using it.

strokersix
01-09-2011, 10:36 AM
I wouldn't want someone to get hurt by something I built. Could be a nasty situation.

vpt
01-09-2011, 10:49 AM
I wouldn't want someone to get hurt by something I built. Could be a nasty situation.


Very very rarely is anyone working in the shop with me and when there is it is only my one buddy. I don't let any random people in my shop ever for more reasons besides just getting hurt.

bob ward
01-09-2011, 10:54 AM
The car hoist business is a very competitive business, there is no more steel or strength in a car hoist than the standards call for. Those uprights are designed to work in that exact hoist configuration, no more no less.

Having said that, naturally there are reserves of strength in the design standards and you may well get away with the jib you propose, but you will have absolutely no idea how close to the wind you are sailing.

My other concern would be the concrete fixings. A vehicle on the hoist is hardly ever going to give you an ideal 50/50 weight distribution, so the base is designed to take some moment of course, if you look in the pieces of paper that came with the hoist they will tell you the amount of allowable out of balance.

When you have an engine hanging 6' out from the front of the hoist you are greatly increasing the moment on the base fixing. The base has strength reserves designed into it, but again, with that extra loading you don't know how close you are sailing.

So come the day when there is a front heavy V10 diesel vehicle up on the hoist, you are out buying parts, and the kids pick up a big block with the crane so they can bolt it to an engine stand.

Ian B
01-09-2011, 12:42 PM
Boy oh boy,

From the photo in the initial post, I wasn't thinking this was installed in a commercial workshop - it looks more like someone's home shop to me, but I could be wrong.

VPT says that he has sufficient experience to operate a car lift correctly such that, for instance, once the engine is removed, the car won't fall off back end first. As I don't know him personally, I assume this to be correct. Evan, when you refer to "the operator", my assumption was that this would be VPT himself.

How many of us operate unguarded machines? How many of our home workshops would stand up to an inspection by the host country's HSSE inspectors, as if it was an industrial shop? How many of us have built something that's safe in sensible hands, but could cause injuries if operated by someone who doesn't know what they're doing?

On swinging loads on swinging cranes, take mobile cranes as a random example. It's possible to tip pretty much any mobile crane ever built over sideways if too much load is applied at a low boom angle. The only thing (usually) stopping this is a crane operator who understands load tables and boom angles, use of outriggers & load spreaders etc. There are many, many more examples where commercially available machinery hasn't been (and can never be) "idiot proofed".

The last time I checked, this was still called the Home Shop Machinist BBS, so answers aimed at home users would seem appropriate to me.

Ian

vpt
01-09-2011, 12:48 PM
Boy oh boy,

From the photo in the initial post, I wasn't thinking this was installed in a commercial workshop - it looks more like someone's home shop to me, but I could be wrong.

Ian


That is correct this is a personal home shop. I don't employ other people or have others even come and help. Like mentioned I have the one friend (only one I can trust in the shop) once and awhile help me with certain things but that is it. I would be the only one operating the crane ever.

justanengineer
01-09-2011, 01:13 PM
Now that I can see your pics and after hearing all the discussion about it I can understand where youre coming from. Have you considered the normal under-the-car/lift engine hoist/lowering devices? There are a variety of them that mount/rest across the spring towers/fenders/frame right above the engine and lower parts from above. Those are nice because most dont even require hood removal. My personal favorite I had a few years back looked similar to a normal cherry picker style engine hoist except it had a flat table on top of the arm that had various attachments which allowed removing engines, trans, and axles, very similar to a trans jack. On mine the table tilted via handwheels/leadscrews in 2 planes, could place an engine 4 inches or 8 feet off the ground, and even could hang engines underneath it if necessary. The only reason I gave it up was it was a little too big (came out of a commercial semi diesel shop). You could probably fab up a smaller one inside of a day that would suit your purposes or buy one from a shop closing for even less (last one I saw at auction brought about $50). Just something to think about...either way...good luck with your project.

courtjester
01-09-2011, 01:13 PM
I have not read every post here but it seems to me you want to use your hoist to pull an engine.
Why not make an "H" out of "I" beam and mount it on the hoist bolted to the 4 frame supports to each corner. Use the center "I" beam to put a trolly and hook a chain to it to lift the engine? the hoist gives the lift and the trolly give movement away from the engine bay.

This way the load is balanced on the inside of the hoist supports.
My 2 cents

vpt
01-09-2011, 01:48 PM
Justanengineer:
The fender jack would work for lowering the engines to the floor and raising them back up for installing but still wouldn't work for swinging over and lowering heavy intakes or heads onto motors. The cherry picker style doesn't work for lowering engines to the floor or raising them up off the floor because the lower arms with wheels are in the way.

I have a tranny jack for lowering out transmissions, gas tanks, subframes, etc. from vehicles while on the hoist.

Courtjester:
This is a two post/frame hoist not a 4 post.

Evan
01-09-2011, 02:13 PM
The last time I checked, this was still called the Home Shop Machinist BBS, so answers aimed at home users would seem appropriate to me.


Do you have any idea how the load is transferred from the lifting mechanism to the support columns?

Ian B
01-09-2011, 03:56 PM
Do I have any idea how's the load transferred from the lifting mechanism to the support columns? You mean, what stops the crane mounting from slipping down the column? No.

However, if I were to be the one designing such a mounting, I'd probably pick up on one or two of the emergency brake lugs or holes (whatever this particular 2 post lift has). These are designed to withstand the impact of a 2.5 ton load (per column) falling about 4 inches, and would therefore probably be quite happy supporting the static load of an engine block.

Ian

vpt
01-09-2011, 04:11 PM
I was thinking super glue and some duct tape would be sufficient?

Richard86
01-10-2011, 11:36 AM
http://i244.photobucket.com/albums/gg5/richard986/01-09-11004.jpghttp://i244.photobucket.com/albums/gg5/richard986/12-11-09003.jpg
Here is the one I built for my lift. The lift is a Weaver 11,000lb. One of the reasons I went with this lift is how heavy it is built. I have changed about 20 engines with this crane and the vehicle doesn't even wiggle when I use it. I was amazed at how well it worked. I'm the only one who uses it, so I'm not to worried. I also included a pic of the stands I use for changing fuel pumps. I used to use the crane to pull the box, but the stands work a lot better. It keeps the box in the exact position, so you can just lift the rig back up and install the bolts.
Hope this helps. If the picture isn't very good I apologize. I very rarely post pics, but I thought this time I might have something to offer.
good luck.

Rich

vpt
01-10-2011, 07:49 PM
http://i244.photobucket.com/albums/gg5/richard986/th_lift.jpg (http://s244.photobucket.com/albums/gg5/richard986/?action=view&current=lift.jpg)http://i244.photobucket.com/albums/gg5/richard986/th_boxlift.jpg (http://s244.photobucket.com/albums/gg5/richard986/?action=view&current=boxlift.jpg)

Here is the one I built for my lift. The lift is a Weaver 11,000lb. One of the reasons I went with this lift is how heavy it is built. I have changed about 20 engines with this crane and the vehicle doesn't even wiggle when I use it. I was amazed at how well it worked. I'm the only one who uses it, so I'm not to worried. I also included a pic of the stands I use for changing fuel pumps. I used to use the crane to pull the box, but the stands work a lot better. It keeps the box in the exact position, so you can just lift the rig back up and install the bolts.
Hope this helps. If the picture isn't very good I apologize. I very rarely post pics, but I thought this time I might have something to offer.
good luck.

Rich


That is great and very very interesting but I can only see small 2x2" pics. :(

With heavier loads on the crane do you see any flex in the post at all?

Ford gas tanks I use a tranny jack to lower the tank, do the work then jack back up. For our trucks with platforms dropping the tank is the only way. I have done fuel pump work on my brothers chevy three times every time pulling the box. To me either way seems to be about the same amount of work. Normally on rusty trucks replacing the two broken strap bolts is easier than replacing 6 bed bolts.

Richard86
01-11-2011, 02:15 AM
Sorry about the pics Andy. I'm not really up on the picture thing. I made them bigger hope that helps. There is no movement at all in the lift when using the crane. The heaviest engine I've had on was a 7.3 diesel. I'm with you on the fuel pump deal, the only time I really get to use it is on Chevy's. Which is what I work on the most. If the bolts don't come out easy I just pull the tank. I like pulling the box so I don't have to fight lines and sloshing gas.

If you notice in the pic. of the crane I attached the pillow blocks down on the heavier section of the lift. If I remember right your lift was made similar. The top section is lighter gauge metal.

Rich

vpt
01-11-2011, 09:11 AM
Thanks for the bigger pic! Yes my lift is pretty much the same, I wouldn't think about attaching the crane to the upper bolted on section.

My lift has factory drilled holes for accessories on the side that I have to check out yet to see if they are in the right spots for me to use. I was planning on bolting on the base of the crane instead of welding.