- Thread starter W.olly
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They are very strong and stable for sure... but also light & easily moved. I thought a van on top to be rather top-heavy and (to use an old saying) a bit "Swede on a Knitting Pin" to risk your life under for a few quid.
On a perfectly solid ground surface, with the existing design and 400kg downforce on each stand, at the height shown in the photo, with the wheel right in the centre of the stand, then a fag packet estimate of the sideways force required to tip a stand over is 80kg. That could easily be reached if pulling or shoving quite hard on one corner of the vehicle. If the wheel is off centre, then the required sideways force to tip the stand decreases in one direction and increases in the others. If one stand starts to tip, sideways forces would start to be applied to the other three stands, which would tend to add some resistance to the sideways movement. How much resistance would depend on things like the direction of movement, suspension stiffness, and tyre pressures.
indy4x
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Devil's advocate, axle stands only have a single tube above the triangular bit, this has 4 on each
ajlelectronics
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But a tripod is the most stable shape.
W.olly
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So no need to load test them haha.
To answer.a.few.concerned thoughts. I have some 5mm thick discs x 75mm diameter for the leg bases. Just not welded them on yet.
The flags have been down for 15 years or more. The cracked ones are from when I had boats on trailers which weighed around 3500kg.
I wanted to get it this height so for ease of working knowledge it. I can either lower the lifts to 500mm high so I can lye down on a creeper or at the fullnheight I can stand to rebuild what's needed or sit on a chair under the car to work on it.
I have given it a good shove about in all directions and it's very stable.
The blocks of wood to gain height is fine to so. Safe enough and as for the length of timber used as a jacking beam. Well that is 75x50 x 3mm RHS. It's 47inch long. It is locked inplace each end so unable to move or slip.
So I agree in the need to spread the load of the legs more as.said I have discs to help there. Even considered adding say 6mm or so rubber base to the leg bases.
After working under cars for years when on a le.stands this feels so much more stable and safer.
To answer.a.few.concerned thoughts. I have some 5mm thick discs x 75mm diameter for the leg bases. Just not welded them on yet.
The flags have been down for 15 years or more. The cracked ones are from when I had boats on trailers which weighed around 3500kg.
I wanted to get it this height so for ease of working knowledge it. I can either lower the lifts to 500mm high so I can lye down on a creeper or at the fullnheight I can stand to rebuild what's needed or sit on a chair under the car to work on it.
I have given it a good shove about in all directions and it's very stable.
The blocks of wood to gain height is fine to so. Safe enough and as for the length of timber used as a jacking beam. Well that is 75x50 x 3mm RHS. It's 47inch long. It is locked inplace each end so unable to move or slip.
So I agree in the need to spread the load of the legs more as.said I have discs to help there. Even considered adding say 6mm or so rubber base to the leg bases.
After working under cars for years when on a le.stands this feels so much more stable and safer.
Pigeon_Droppings2
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Too sketchy for me I'm afraid but each to their own I reckon....I do just prefer stuff thats certified in some way I think.
On the general design...would the failure of a single leg (for whatever reason) result in the whole lot falling down?
On the general design...would the failure of a single leg (for whatever reason) result in the whole lot falling down?
W.olly
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If it was an axle stand then yes it would be certain fail lol.
arther dailey
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Can some oneexplain why this is supposedly a bit edgy ? when a hydraylic lift fits four pads under the tin sills and every garage uses them ?
Provided the welds are good, and there's not a lot of sideways shoving involved, the stands should be OK. It's more a case of being mindful of what the limits might be.
Bear in mind that something like a Transit van has a side cross sectional area of, let's say for arguments sake, around 100sq.ft, and a 50mph gust hitting that directly broadside would impart a force equivalent to 300kg, which would probably topple the whole thing. The original post mentioned using the supports for a car, so a somewhat smaller cross section.
Bear in mind that something like a Transit van has a side cross sectional area of, let's say for arguments sake, around 100sq.ft, and a 50mph gust hitting that directly broadside would impart a force equivalent to 300kg, which would probably topple the whole thing. The original post mentioned using the supports for a car, so a somewhat smaller cross section.
W.olly
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I think it's more.to do with folk overthinking things.
Mine uses a four poster - sills fail, it dumps it on the deck.
But the lift itself is bolted to the floor – and yes, cars do still fall off them. The structure itself, assuming it’s not been abused, is more stable, robust, certified.
Here, my spidey senses are twitching.
And when they do, I step away. So far, I’ve had no reason to second guess those twitches in 30 yrs of work 35 yrs of playing with cars, including lifting them up and down. I have scissor lift, big robust stands and a pit – not all in the same place I wouldn’t be trusting anything on 4ft high axle stands, never mind home made ones.
And with the assertion the slabs have cracked under 3-1/2 tonne nicely spread over tyre contact patches, I’m also closing my eyes when I walk past . . .
Pigeon_Droppings2
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I'd never use any type of stand for that height on all 4 corners to be honest....just never had the need to do it.
I've always used blocks/ramps for getting all 4 wheels off the ground. Anything else I usually roll the car over.
I think it's down to personal preference....if you're happy they're ok then it's your choice I think.
The point load on those flags looks a bit extreme, could you not weld something to the bottom of the legs to spread it out a bit?.
Also I know those bolts in shear should be more than up to the job but it's a lot of faith in them.
As said above it's up to the individual what the maximum element of risk is acceptable.
Also I know those bolts in shear should be more than up to the job but it's a lot of faith in them.
As said above it's up to the individual what the maximum element of risk is acceptable.
Morrisman
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Whenever I get under a car that’s up on jack stands, or blocks, I grab something solid on the car and give it a damn good shake, push and pull it, just in case… If it survives that I have no qualms climbing underneath.
I’d never simply hike a car up in the air, then dive underneath and start work.
Jelly_Sheffield
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I have, replacing the suspension on 4x4's where the chassis is already 425mm high with wheels still on the ground, and above 500mm by the time the suspension down-travel is exhausted.
The trick is to use appropriately sized (i.e. bigger) stands with nice wide bases, and if you're in any doubt, to use more of them.
If I was doing it regularly, I'd make trestles to slide underneath.
In short, it's not as well designed or made as a proper lift...
That said, it's not an awful design, and could easily be modified to remove a lot of the remaining issues.
1a) Starting with the locking mechanism... Machine screws (and most other types of bolts) are not intended to carry sheer loads.
That weak point is an easy fix: use dedicated pins turned from a suitable grade of steel for the imposed load.
1b) Continuing on the locking mechanism, there's no positive retaining mechanism for the locking pins, the one time one gets knocked out, suddenly all hell can brake loose.
Given nuts would go right now on for zero effort or modification, that's just slack.
Proper pins cross drilled for a d-shape or spring type cotter pin would be better though.
2a) Moving on to stability, the imposed load on the slabs is huge, and OP already recognised this issue, and planned a mitigation (weld on spreader pads), but used it anyway without fitting them.
Sure it's fine this time, but only takes a bit of water getting under a slab to make it hollow and suddenly the very strong (under compression) slab is very weak (under tension) and cracks, increasing the risk of toppling.
Easy fix, fit the damn spreader pads.
2b) if it does become unstable that's made much worse by the fact that the four lifting stands are not connected or bolted down, making the whole thing susceptable to toppling.
As it's on slabs bolting (a preferred option in my view) is probably out.
But connecting the 4 stands together (by bolting them to thick angle iron or c-channel) would vastly improve stability during a both lifting and any potential failure condition.
If quick assembly is an issue, welding scaffold clamps to the stands and using 4 (or ideally 8) scaffold poles), would be better than nothing.
3) Then we have the stands themselves, the design is susceptible to racking and binding during a lift, with 16 separate slide ways that each have substantial play and multiple degrees of freedom.
A "proper" lift will have only one slideway per lifting element, usually engineered such that it's so close fitting that the moving part can only go up and down.
Slightly more involved fix, but if each post had a brass/bronze bushing with a close sliding fit, the play could be eliminated.
4) The lifting mechanism is comparatively high risk, using airbag jacks gives comparatively poor control compared to a chain hoist, lead screw, or hydraulic ram.
Compared to said methods air-bags have a substantially greater risk of catastrophic failure, causing a rapid loss of control, and are less easily inspected for damaged.
Easy fix again, use single acting hydraulic rams with a single pump, (or even individual air over hydraulic bottle jacks) mounted in the bottom half of the stand instead.
There is one issue that's not as easy to make a fix for, which is the lack of an emergency load restraint.
5) Modern lifts built with a mechanism that isn't fail-safe, usually incorporate a one-way self engaging break, that has to be positive disengaged to lower it (often hidden by the fact it's actuated by the control mechanism when you push the down button).
Using ratchet pawls would be an option for OP, but would need careful positioning to be effective.
I'm just going to leave this here...
