adjustable car ramp

Apologies folks,

the link should be

I hope your design skills are better than your web skillz.. try linking to the full size picture, not the thumbnail:

Other than that, it looks interesting. Having a low run-on would definitely have helped on a couple of cars I've had with low air dams or long overhangs.

It would be better if the height adjuster was accessible from both sides (or mirrored on each of a pair) as you'd have to be under the front overhand to get to it the way you've drawn it. I think you'd have turn the scissors sideways to make that work though, unless you add an extra shaft and set of bevel/worm gears..

my website skills are not great!, thanks for bringing the error to my attention

try this link

But how is the 'run on' achieved in practice? This has to take as much load as the rest.

I've a feeling I've seen adjustable ones for sale already.

However, if you've a problem with a low spoiler etc a stout lump of wood between wheel and start of ramp can do the trick.

Another important thing is to provide some means of the ramp not just being pushed along the floor - I've glued some rubber matting to mine.

There used to be such things on sale but I don't recall seeing any for some years. As I recall, the design was similar to yours.

As someone else mentioned, a real problem with ramps is stopping them being pushed away as you drive on. I loop a bit of old carpet around the lowest "step" so the wheel is turning on that and "pulls" the ramp toward the wheel. Maybe a neater solution would be a design improvement for your project.

With two pairs of ramps you can lift the whole car level- always nice if you've some serious crawling under it needed.

Good luck with the project.

As others have said, these are (or were) already made, I have used a set, but it was quite some time ago.

They are a good idea in principle, but they do have their problems (as unfortunately I found out!) One of the basic first rules of working on a car, is that you never work under a vehicle supported only on a jack, in effect your ramps in their basic form are simply jacks, and with the set I was using, one of the jack collapsed while the car was on it, the pivot which anchored the screw gave way. Luckily there was no one under the car at the time. To make a safe product, you would need to incorporate some kind of secondary holding system into the design, something completely independent of the lift screw mechanism. If you study the type of lifts used by garages, they always have a mechanism to prevent the lift from dropping in the event of a failure of the lifting mechanism. This is a legal requirement under LOLER and H&S regulations. While your device would mainly be used at home, you would have great difficulty finding anyone to produce the design if it was not legally compliant, and you would also be in big trouble in the event of someone getting injured or killed while using the device, if you could not show that it was built to comply with current safety regulations.

Anything that uses a screw that can't turn by itself (ball screws aren't used for this reason), does not need a secondary locking system. And before you try arguing, at work there are three different two post lifts (two are 3tonne rated, the other 5tonne rated) that use screws, along with a four post lift rated at 18tonne, all of which use screws with no secondary locking device.

See the answers given in all the other newsgroups you have posted your message to.

Are you sure they're not driven by a braked motor?

You'd need a *very* coarse screw thread to be reversible.

The message from "Dave Plowman (News)" contains these words:

Think Archimedian jeweller's drill.

As opposed to a g cramp. But screw threads, particularly greased ones that are subjected to vibration do move quite easily.

That's the exact principle they rely on. Certainly all the two posters have no form of braking, but the motors are highly geared via belts, which helps increase resistance to the screw self running (the screws spin, and the nuts are stationary). Having had to lower one manually, they're not going to self-run! The big four poster isn't braked, but again each motor is geared through a gearbox (going by the shape/location of the gearbox, I'd suspect they're epicyclic gearing, rather than a wormwheel and screw)

And getting back on topic, a brake on the screw/nut/drive system is not a secondary locking device.

The message from "Duncan Wood" contains these words:

Not under load, they don't. And anyway, how much vibration are you expecting on a set of ramps?

Yep, they do. Try greasing a tyre change jack you don't care about. If you're running an engine a reasonable amount.

The message from "Duncan Wood" contains these words:

I've always greased the screw on scissors jacks and never had one go down on me (ooo err, missus).

Cue long boring discussion of VBG70. Although if they're connected by belts braking the motor woukd be pretty pointless

My scissor jack stripped it's threads recently. I suspect post lifts are made of sturdier stuff and for commercial use need to be inspected in order to obtain insurance.

Commercial ones use precision ACME threads with bronze nuts, and some form of lubrication system (some use oil, some use grease) They've also got to be inspected every 6 months, which includes a check for thread/nut wear.