Controlled release of a Clarke Bottle Jack fitted to an engine building stand

Hi - I have a Clarke 2 Tonne bottle jack fitted to my 5" gauge engine building stand but the one issue I have with the device is that you do have to be very careful when operating the release valve as failure to do so results in the table coming down with quite a bump threatening the stability and safety of the whole assembly. I have got use to just cracking the valve when lowering the table but I am concerned that should it be operated by someone else, a member of the family for example in my absence, they would let it down as one would when using a standard roadside wheel jack with possible disastrous consequences all round. Has any else had this problem and come up with a means of fitting a controlled release?

Have you left the jack with the original 'engage the jack handle release' arrangement? I made a simple knurled knob out of a piece of scrap Ali for my workshop press; it made control of the release/reduction of pressure much easier than using the jack handle type device supplied with the press.

BTW, as you can see from the photo, sometimes 30 tons isn't enough on its own to free a stubborn rusted in part!

Further to the suggestion from Stueeee of a permanently fitted knob, or short handle, for better control consider adding a stop pin or flap to restrict the initial valve opening to a suitable slow descent position. Make the stop device spring loaded or hinged so it can be overridden when you want faster movement.

Myriads of ways to do this sort of thing. Depends what you have in the "too useful to bin" box.

Clive

PS Naturally the perfect bolt on and go part will surface about an hour after you have spent half a day faffing around to "it'll have to do" standards with the crap you managed to find!

You could add a lever to the release valve and then operate the lever with a screw to give both control and limited movement to the release valve. I don't know what your setup is like but this type of operation would allow you to put the release operating knob in a convenient position and also avoid accidental release caused by catching the release valve operating knob.

Martin C

Have attached a pic of the current set-up

Perhaps allowing even more control than a knob would be adding a lever to the knob.

I like the idea of a lever with a stop to lit its movement.

How does the threaded part operate the valve at its base?
If it's a tapered fit, a bit like a brake bleed nipple, then maybe a new part with a more pointed taper, such that the hole is exposed slower as the bolt is unscrewed, similar to a carburettor main jet..

Bill

Martin's idea of a lever operated by a screw would give you a very safe/slow predictable way of opening the valve.

If that is the jack I think it is there may well not be room to permanently fit anything sensibly easy to operate to the release valve without interfering with the actual jack operation.

If that is the case look into whether some sort of L shaped, box spanner and lever, device can be made with the initial travel limited but striking the ground or part of the jack body. Further opening would require the spanner to be removed and refitted putting the lever clear of the obstruction for another partial turn. I have encountered more sophisticated variants of that style of device which were permanent assemblies with sprung loaded detents restricting the travel to half or one third of a turn at a time. Pushing the knob down let it move past the detent for another bite.

I'm sure the same sort of thing could be arranged with a spanner device and suitably shaped head on the release screw. The bottle jack on my home made press, similar design to Sueee, has a flat bar shape on the end of the release device so restricting to half a turn at a time is easy. The T-bar handle spanner I made for the job turned out rather longer than I'd ideally have liked due to having to avoid a projection that would have restricted it to half a turn at a time!

Clive

Clive

All of this is down to the viscosity of the fluid (oil) ! on a cold day your controls act slowly - On a hot day it will drop like a stone ! On simple (cheap ) gear this will always be a problem, to be safe in most conditions it will be to slow ! Using mechanical solutions to solve a hydraulic problem will not give a satisfactory result . VERY careful operation of the relief valve is the only way ! Put simply if you are not competent to use the equipment - THEN DON'T ! I understand how an aircraft works - it doesn't mean I can fly safely ! Noel.

I have attached a photo of the release valve removed from the jack. The thread mikes up at 9.70 x 1mm pitch and has a square end face whereas I might have expected a taper fitting. The thread is presumably a nominal 10x1mm. Shinning a light down into the valve body reveals a corresponding flat seating face but it was not obvious without further poking around whether or not a washer of some sort is in place.

As an alternative have you thought about a 12v electric scissor jack where you have button control of lowering speed.

Search youtube and you can see them in operation most were rated at 3 tonnes.

You could supply power from a laptop charger or a spare 12v battery.

A small clamp-on bracket on the left hand plate, a pivoting nut on that bracket, a clamp-on lever on the release valve with a pivoting anchor point at the top and a screw with knob between to two pivots and you have a controlled release mechanism for very little cost or effort.

Martin C

Martin - Perhaps a simple sketch of what you have in mind would be useful.

Is there a ball in the hole under the flat ended screw? That's sometimes done as a cheap option that is tolerant of the fluid port not being quite concentric with the thread. If port is not concentric with thread, it's more difficult to produce either a 'needle' or a 'spline' tip on any replacement item to give finer control.

Michael - Looks good - Many thanks for that

Not answering the question:
- add some telescopic gas dampers to moderate the descent rate independently of the jack, or
- replace jack with screw operated type and use a cordless drill to raise/lower
- add prominent warning label "release cautiously, platform may drop faster than you expect" or similar

All I would say is does that design put any part of you underneath the table?