crane uprate – where would you add some metal ?

[Maurice TaylorParticipant @mauricetaylor82093]

Hi, just looked at my Draper 1 tonne engine crane , I don’t think any of the steelwork is designed to fail ,every bolt is a 14mm 8.8. Why would any body design steelwork to fail when it includes a hydraulic ram.The ram will probably have a yield valve to prevent it being overloaded.

Regarding the castors it is easier to control with only 2 swivels ,think supermarket trolley with 4 swivels ,goes anywhere.

Maurice

Edited By Maurice Taylor on 10/02/2021 11:00:52

[SillyOldDufferModerator @sillyoldduffer]

Posted by JasonB on 10/02/2021 08:02:05:

As Noel says I would have though they should be designed to" fail" at the ram long before structural failure, simply by the rating of the ram only being able to lift the quoted SWL plus a bit of give and preventing an overload. Hence why I mentioned the ram early n in the thread.

…

I don't disagree because I don't know, but what part of the ram fails? Unlikely to be the piston O-ring because it has to be secure enough to maintain a seal every time the ram is pumped up and released. Unless the cylinder expands like a balloon sufficient to break the seal when over-pressured? The pump valve leaking is a candidate, though I guess a weak seal on the pressure release thingy is more likely. Perhaps the length of the pump handle limits the amount of pressure the user can apply and the pump piston leaks if excessive pressure is attempted. There are many possibilities.

Unpicking the design of Stueee's crane is 'real engineering' in the sense that more than practical skills and common sense are needed. To work out how and where the crane might fail needs a solid understanding of the materials used combined with knowing how to calculate the forces at each point in the structure. Otherwise we are all guessing!

For example, the maximum force on the hook and chain is obviously 500kg, approx 5000N, but the force on the other end of the jib needs thought. It's much higher than the rated load because the jib acts as a lever. We're looking at 15000N or more, and it's all applied to the axle-bolt connecting the jib to the rear strut. Unless sized correctly, the bolt or jib will fail. And the jib beam has been weakened by the hole – by how much?

The strength of the jib beam, with hole, and the strength of the beam, and the strength of the rear strut all have to calculated together and kept in proportion. Similar analysis is needed for the rest of the structure. The purpose is to identify where forces concentrate, how big they are and whether they compressive or in tension so the design can accommodate them safely. In Stueee's crane think the rear strut is in tension, which affects the quality and size of the weld needed to join the hinge part to the strut. Having done all that, it's also necessary to confirm the crane is stable however high the load, and when the crane is turned.

White collar engineering is hard. Beyond me I'm afraid – my maths skills aren't good enough. It's very sad…

Dave

 

Edited By SillyOldDuffer on 10/02/2021 11:15:55

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, when using swivelling castors on all four corners, it is best that all of the load should and certainly the centre of gravity, be inside the centre of all the wheels, when they are all pointing towards each other, but tall narrow loads are normally worse than a wide shallow loads, but of course if you are raising a wide shallow load that is heavy on an engine crane, it can have the same effect as a tall narrow load. Lifting and moving heavy items should always be treated with respect and a little thought should be given before hand, i.e. a risk assessment and safe procedure should be adopted and all loads should be moved as close to the ground as practically possible. Stueee's pallet transfer truck is a good item to use, but even these can topple if the balance isn't correct and if you have, to move it down a slope, the load should go first, but the slope should not be a steep one and it would pay to lash it onto the truck. You should not pull it down a slope, because if you loose control, it is most likely it will run you down. I have even seen someone loose control of a four wheel barrow when pulling it down a fairly shallow slope with a heavy load on it, but lucky for him it steered away from him and run up against a grass bank.

Regards Nick.

[Sam Longley 1Participant @samlongley1]

Normally the limit on the ram is the power of the pump. That usually is the part that cannot deliver any more force. I have overloaded jacks & got to the point where the jack handle has just bent or the bracket to the pump has bent or the pump has let go & the ram has gradually sunk back

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Dave, the ram is quite likely to bend the more it is pumped out. I've seen 4 inch rams that have bent due to overload, but the seals all held.

Regards Nick.

[Nigel Graham 2Participant @nigelgraham2]

A common point here is an assumption of an overloaded engine-crane physically breaking, with much discussion on how and here.

Would it not, as some do ask, have a safety-valve in the cylinder or pump that would stop overloading in any position of the arm?

"Fixed castors"… Eh? Fixed wheels, ,yes. I have used these hoists on smooth indoor floors and in the street, and they are awkward brutes to manoeuvre.

'

For moving large machines much wider than a pallet-truck, and with an off-centre, centre of mass, I would prefer skates (might be available on hire?) or rollers. Pallet-trucks are designed for closely-symmetrical loads and are not very stable otherwise – I have moved enough on a large yard with various slopes and dips.

A point with rollers though – never place them under the load with your fingers round them. Always lay them on the floor and roll them in under by open palm.

Similarly when pushing anything into position where a slip could trap your fingers or take your knuckles off; be it a heavy machine or a spanner. (A spanner is more safely pulled round, wherever possible.)

My work sometimes took me to an outdoor laboratory where I noticed the staff's practice when assembling a set of big steel poles linked by sleeves and pins to suspend heavy loads from a crane. They would hold the locking-pins by fingers but only as far as inserting the tips into the outer sleeves, and push them home by open palm.

Basically consider that loads of any sort can suddenly slip or drop despite care.

.

Years back I worked for a company making very high-precision, industrial screen-printing machines, mainly exported. One day it engaged a timber-merchant across the road to use a side-loader to lift a big square, wooden box onto a lorry trailer. Unfortunately the machine hidden inside weighed perhaps a tone or so – and was L-shaped in plan. It appears that no-one thought to mark the centre of mass on the box and to advise the side-loader driver; but luckily the resulting drop did not injure anyone. It did though, damage the printing-machine starting its journey to a customer far overseas. By chance the company was near to completing another so finished and sent that, but the result was delays to two important orders.

[duncan webster 1Participant @duncanwebster1]

I wouldn't rely on any safety features being built in to the hydraulics. I was once trying to get some wheels off axles using a 1te hydraulic jack. 7 came off as expected but one just would not move. Turns out later it had been loctited on. Anyway being an impatient so and so I just applied some scaffold pole to the lever, and finished up in a heap on the floor when the jack cylinder actually burst. I've still got it somewhere, it will come in handy for something!

In the day job I one got called in to investigate a failed scissor lift platform. It was supposed to lift several tonnes through several metres, then some shot bolts would fire forwards and the platform would rest back down at the set height. What had happened was that the intrlockery had gone awry and the table came up under the advanced bolts. As the geometry of scissor lifts changes from down to up the ram extends, but the mechanical advantage changes so you need a lot less pressure to lift a given load when it is up than when it is down. However, when you stop the platform going up with an external constraint, the now nearly fully extended ram gets a lot more pressure then it has seen before at that extension and actually buckled, resulting in several tonnes of platform and load coming down very quickly. Fortunately no-one was foolish enough to be underneath. This was an industrial job, not mass produced down to a price.

Edited By duncan webster on 10/02/2021 12:57:12

[not done it yetParticipant @notdoneityet]

Posted by Stueeee on 10/02/2021 09:14:43:

Posted by noel shelley on 09/02/2021 23:56:05:

Castors on the rear are a necessary evil but if you have castors on the front it will become VERY dangerous and difficult to control.

Did you follow the weblink I put up in my previous post? Engine crane with swivel casters It would be surprising that this company, who sells to professional users would be selling an inherently dangerous product. Certainly if the crane in question was deemed unsafe at end use in a commercial garage or workshop, the HSE would take appropriate enforcement action.

Perhaps you missed the number of castors on that hoist? There are only four on the one under discussion. Let’s compare apples with apples.

[Adam HarrisParticipant @adamharris13683]

To be useful in lifting machinery I find engine hoists need to be modified by increasing the height. I used to have a height-modified 1 ton Draper engine hoist and found that eventually the wear on the shape of the bolt holes in the frame locating the rear of the legs (the holes are in quite thin plate) led to a serious lack of rigidity/stability so I bought a new subframe section from Draper (Draper are great for availability of spares) and then sold it (modifications removed) and treated myself to an upgrade with the 2 Ton SGS. The SGS has much thicker plate where the bolt holes are. The Draper has slightly wider legs which does offer slightly better stability. My method of raising the height is very simple: by putting the column on a wall of 3 steel box sections bolted together (compression resistance) and made 2 longer aft support bars (stretch resistance) to connect to the taller column accordingly. I also changed the legs' front wheels to heavy duty Flexello fixed steel castors. It is not very stable operating on ground with any sort of slope, but otherwise it is fine on tarmac/concrete driveway, manoeuvring under load can only be effected with a 6 ft metal pole levered under the rear frame bar inching it in the direction desired.

Edited By Adam Harris on 10/02/2021 14:34:13

[StueeeeParticipant @stueeee]

Posted by not done it yet on 10/02/2021 13:35:35:

Posted by Stueeee on 10/02/2021 09:14:43:

Posted by noel shelley on 09/02/2021 23:56:05:

Castors on the rear are a necessary evil but if you have castors on the front it will become VERY dangerous and difficult to control.

Did you follow the weblink I put up in my previous post? Engine crane with swivel casters It would be surprising that this company, who sells to professional users would be selling an inherently dangerous product. Certainly if the crane in question was deemed unsafe at end use in a commercial garage or workshop, the HSE would take appropriate enforcement action.

Perhaps you missed the number of castors on that hoist? There are only four on the one under discussion. Let’s compare apples with apples.

No I didn't miss that fact, however, the mid casters visible in the weblink I posted are there solely to be in contact with the ground when unassembled crane is moved. The mid casters on that crane, like those on mine will be clear of the ground when the legs are folded out with the crane in use. So in essence, yes I feel I am comparing apples with apples.

In my view, there has been a near universal decrying of swivel casters on this thread without any solid evidence being produced of why they are inherently dangerous.

[Adam HarrisParticipant @adamharris13683]

I thought the 4 SGS swivelling castors looked a bit feeble but they have surprisingly held up absolutely fine. They are similar to the rear wheels of the 1 ton Draper , which I did once have to replace. The legs on the 1 ton Draper have heavy duty fixed castors at the front (unlike the 2 ton SGS) and personally I think that is a more reassuring arrangement hence my changing the SGS to fixed front castors too

[Adam HarrisParticipant @adamharris13683]

Stueeee you are of course quite right about the purpose of the mid castors

[Adam HarrisParticipant @adamharris13683]

Incidentally as regards the angle of the axle of the fixed front castors, on the 1 ton Draper they are mounted at an angle to the leg so that the axle is correctly aligned with forward travel. My modified SGS also has the mounting angled for forward travel. But even with the forward castors fixed, the rear swivelling castors do permit one to manoeuvre the whole crane around in a turn with the aforesaid 6 ft metal pole lever, of course lowers the  machine so it sits on the legs before doing turning manoeuvres

Edited By Adam Harris on 10/02/2021 15:01:45

Edited By Adam Harris on 10/02/2021 15:15:44

[Adrian R2Participant @adrianr2]

As an abstract exercise, comparing the two designs indicates where the makers think the weak points are:
– Top jib reinforced by triangulation around the upper ram pivot
– Two tension stays at rear to reduce risk of vertical post tilting sideways

The problem with using the hydraulics as a load limiter is the extendable jib surely? If the ram is sized for max load with short jib, then it can potentially overstress when extended.

(No qualifications to back this up apart from decades old physics A level and youthful misadventures with farm machinery, you have been warned)

[Martin KyteParticipant @martinkyte99762]

Whilst I concurr with the idea that beefing it up is a. not worth it and b. potentially hazardous I do think that providing a system like this is tested afterwards and that could be quite simply done the hazard could be avoided.

All one has to do is decide on the aimed for maximum load, add in the required safety factor and load it to that figure. The load need not be taken more than an inch above ground so nothing much would happen in the event of a failure. I woud suggest this be done on home built systems too. It's no different to doing boiler tests at twice working pressure. If it doesn't break you know you are safe at half the loading, if it does well you wouldn't want to use it anyway.

So essentially if you must alter anything like this engine hoist, test it first in a way that it can fail in a safe way.

regards Martin

[Nigel Graham 2Participant @nigelgraham2]

Adrian –

The manufacturers do tell users the maximum SWL at the different settings but might discreetly design them so that they will withstand some abuse and will "fail safe".

Martin –

"An inch above the ground… " Commercial crane-handling courses teach always to ease the load just off the floor, and pause to ensure all is correct before further lifting and moving. Usually if that shows anything at all, it is as simple as adjusting the slings for balance. And that is for normal operation, not just for load-testing the lifting equipment.

It is no bad thing to follow such practices in our own workshops – whether the hoist is lifting a brand-new 6" lathe onto its cabinet or taking the strain when you are changing one of its heavy chucks.

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by Nigel Graham 2 on 10/02/2021 17:41:28:

Adrian –

The manufacturers *************************************

Martin –

"An inch above the ground… " Commercial crane-handling courses teach always to ease the load just off the floor, and pause to ensure all is correct before further lifting and moving. Usually if that shows anything at all, it is as simple as adjusting the slings for balance. And that is for normal operation, not just for load-testing the lifting equipment.

It is no bad thing to follow such practices in our own workshops – whether the hoist is lifting a brand-new 6" lathe onto its cabinet or taking the strain when you are changing one of its heavy chucks.

Hi, when I did my wheeled mobile crane course, (every three years) just easing the load off the ground was always emphasised to check everything was OK before the full lift and when contract lifts were on site, they always did the same, and of course a good banksman would guide you to do this and check before giving you the OK to carry on.

The big difference between a crane and these engine hoists, is a good crane operator can lift the load truely vertical, whereas these engine hoists lift in an arc, so the best position for the boom to be when taking the strain, is horizontal, but of course that is not always possible.

Regards Nick.

[Dave HalfordParticipant @davehalford22513]

Posted by Adam Harris on 10/02/2021 14:50:21:

Incidentally as regards the angle of the axle of the fixed front castors, on the 1 ton Draper they are mounted at an angle to the leg so that the axle is correctly aligned with forward travel. My modified SGS also has the mounting angled for forward travel. But even with the forward castors fixed, the rear swivelling castors do permit one to manoeuvre the whole crane around in a turn with the aforesaid 6 ft metal pole lever, of course lowers the machine so it sits on the legs before doing turning manoeuvres

Edited By Adam Harris on 10/02/2021 15:01:45

Edited By Adam Harris on 10/02/2021 15:15:44

The angle of the OP's castors may be intended to prevent the crane moving or being moved under load.

Speaking as someone who has moved a crane with a Pontiac big block v8 on the jib, running a wheel into a 1/4" af nut hiding on the floor will fix any constipation problems you may have had. It's surprising how much 250kg can bob up and down.

[Reg RossiterParticipant @regrossiter24538]

One thing to be aware of with any lifting operation using a crane, including the type under discussion, is that as soon as the load is off the floor the mass of the load is effectively at the end of the boom where the fall attaches. In the case of an engine hoist that means the mass of your 200kg lathe you're lifting is now in effect about 1.5 metres in the air. Move it at your own peril!

Reg

[Martin KyteParticipant @martinkyte99762]

Posted by Nigel Graham 2 on 10/02/2021 17:41:28:

Adrian –

The manufacturers do tell users the maximum SWL at the different settings but might discreetly design them so that they will withstand some abuse and will "fail safe".

 

Martin –

"An inch above the ground… " Commercial crane-handling courses teach always to ease the load just off the floor, and pause to ensure all is correct before further lifting and moving. Usually if that shows anything at all, it is as simple as adjusting the slings for balance. And that is for normal operation, not just for load-testing the lifting equipment.

It is no bad thing to follow such practices in our own workshops – whether the hoist is lifting a brand-new 6" lathe onto its cabinet or taking the strain when you are changing one of its heavy chucks.

What I was proposing was a failure test. Actually try and break it with a larger load than you are going to use in anger but in a way that causes no risk to you. But perhaps you realised that.

regards Martin

 

PS looks like this one will run and run. Maybe I should pose a wacky idea just for the entertainment value.

Edited By Martin Kyte on 10/02/2021 21:00:58

[Maurice TaylorParticipant @mauricetaylor82093]

Posted by Reg Rossiter on 10/02/2021 19:14:02:

One thing to be aware of with any lifting operation using a crane, including the type under discussion, is that as soon as the load is off the floor the mass of the load is effectively at the end of the boom where the fall attaches. In the case of an engine hoist that means the mass of your 200kg lathe you're lifting is now in effect about 1.5 metres in the air. Move it at your own peril!

Reg

Hi,Could you please explain why the mass would appear to be 1.5m off the floor ,if say you’d only lifted it 10mm.

Maurice

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Maurice, so you lift 1 tonne just off the floor, then that 1 tonne is transferred to the hook and then the pivot pin in the end of the boom. i.e. the weight of an object is on whatever is holding it, imagine you have a bag of shopping on a set of scales and you pick it up, all the weight of the bag and shopping is then in your hand and the scales return to zero.

Regards Nick.

Edited By Nicholas Farr on 10/02/2021 22:14:59

[Martin KyteParticipant @martinkyte99762]

The weight of the load is at the hook but the mass is where it was. The force moves not the mass.

regards Martin

[Dave Smith 14Participant @davesmith14]

Posted by Martin Kyte on 11/02/2021 08:41:26:

The weight of the load is at the hook but the mass is where it was. The force moves not the mass.

Martyn

Nice point which many people are unaware of and hence it gets misused, that mass is different to weight.

Mass = Density x Volume

Weight = Mass x gravity

Essentially on Earth Mass = Weight. However on the moon the mass of an object remains the same but its weight is much lower due to the lower gravity.

Dave

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Martin, agreed and that's why I said weight, which is the effect I believe Reg was talking about.

Regards Nick.

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