Anyone know anything about pneumatics?

[Trevanion]

I've got this really wacky idea that's been bouncing around in my head for a long time... I wonder how much of a complete pig of a job it would be to convert a Sedgwick 571 morticer to run on pneumatic downfeed?

I haven't got the foggiest idea about pneumatics so I'm not even sure if it's possible to get that kind of force out of a cylinder or even how I would attach the bloody thing in the first place, how would I make it stop at certain positions on the depth stop and that kind of thing? I honestly haven't a clue.

Open discussion, please tell me I'm an imbecile if you think so :lol:

 

[rafezetter]

I don't know that much about pneumatics (linear actuators and hydraulics) - but I was under the impression from what I've seen with YT's, and other "crazy builder type" programs on TV that once powered on, they are usually an "all or nothing" affair.

To get them to stop where you want them to, you either have to stand there and turn the power off manually, or have some sort of sensor driven "power cut off" system, the former being very inaccurate.

As for "I'm not even sure if it's possible to get that kind of force out of a cylinder" that is absolutely possible and then some, and will take some tinkering just to find out what the absolute maximum Nms you will need to be for the hardest hardwood you or someone else** might work, like chocabolo, without going crazy over the top.

(**I personally tend to make things with the next owner in mind to cover all bases - if I bought that off you thinking it would make my life easy for hardwoods to find out it's only powerful enough for pine, I'd be pretty pi$$ed.)

Which neatly brings you to your next challenge: using some sort of hard "depth stop" will likely cause motor burnout and other issues as it continues to push against it for the rest of the cycle, or the stop is not strong enough and it just breaks.

Attaching it then becomes the least of your problems to solve, and is probably the simplest to solve.

But linear actuators over hydraulics is definitely the way to go.

...... thought - depth - get a "short throw" actuator... nope nvm - every mortice will be different unless..... you get a longer throw than you might use regularly then have some sort of contraption for height adjust on the bed.

maybe a picture of the machine in question might help?

 

[jimmy_s]

Should be possible. Getting hold of a pneumatic actuator with a sufficient diameter and long enough stroke may be the main issue. You would have to make up heavy duty depth stops unless you wanted to get into electronics. I know of someone who has a pneumatic press which he uses rather than a hydraulic one for pressing powders etc.

One thing to think about though is that air under pressure can be much more unpredicatable then hydraulics as it wants to expand. So for example if a depth stop were to move or something jump out from under the end of the ram and if the ram was under pressure it would immediately and quickly shoot out/extend where a hydraulic ram wouldn't.

You would probably want a double acting ram and a suitable spool valve

hope that makes sense!

Jimmy

 

[xy mosian]

I have done a little work with pneumatics in industry. Forty odd years ago.

My work entailed clamping jigs on production lines so the niceties of control were down to ON/OFF.
Having said that we had some quite large beam cross cut saws, two motors mounted at 45 degrees to the bed, 12 " blades, 18" throw. They were pneumatically driven on the cut and moved quite slowly. They worked so I never got into the how and why of them.

I do recall, 100psi into a 6" cylinder gives 1 Ton of force, near enough. Sorry about the ancient units.
Area x Pressure = Force.

xy

 

[Trevanion]

Basically, in my mind what I want to do is turn one of these, A Sedgwick 571:

Into one of these, a Wadkin MT without the hideous price tag:

After you've done several thousand holes you begin wondering if there's a better way to do it that isn't so hard on the shoulder. The way I think it could be done possibly is that there is a linkage between the head and the shaft the handle is attached to, if you were to somehow attach a cylinder to this linkage I think you could put the force in that way.

(**I personally tend to make things with the next owner in mind to cover all bases - if I bought that off you thinking it would make my life easy for hardwoods to find out it's only powerful enough for pine, I'd be pretty cheesed.)

Funnily enough, the absolute toughest timber to mortice that I've come across is Accoya, technically a softwood. I can usually put holes in Oak, Sapele, Iroko, or any other common hardwood with absolute ease but once you load a piece of Accoya in it's almost twice as hard work sometimes to punch a hole in than Sapele.

Would Hydraulic be a better option? Like I said, no idea myself!

 

[Sideways]

It would be useful to know roughly what kind of force gets applied at the chisel of your morticer when you pull as hard as you can on the end of the handle.
This is a starting point for sizing a pneumatic ram (or maybe a pair - one on each side of the head).
If I were trying to measure this with no special kit, I'd try to arrange a bathroom scale in some sort of sandwich between two blocks of wood where the timber should go. I'd have a block so that the head can press down on it without a bit or chisel in place. Lastly, as swinging on the end of the handle might well be enough to break the bathroom scales, I'd hold the handle just a half or quarter of its length from the pivot and scale up whatever reading I got by 2 or 4 accordingly.
There seems to be a constant supply of surplus new pneumatic cylinders on ebay because people get sizes wrong. They always looked good value for money to me. Thick wall platic pipe and push fittings designed for pneumatics are cheap enough
Solenoid valves will turn air on or off under electrical control. I imagine your idea could be made to work and needn't break the bank.

Get catalogues from people like Festo and (I think) SMC ? Pneumatics make manufacturing production lines work all over the world. It's proven technology ...

 

[Trainee neophyte]

Essentially you want something to pull the handle on your behalf, yes? My immediate thought was an electric winch motor, pulling a cable around a pulley wheel attached to the handle or its shaft. A continuous cable would give you up and down, and the pulley wheel could be sized to give you the correct force. Your average Chinese cheapo winch can lift 200kg, which would be the same as 2 big lads hanging off the end of the handle. Would it be fast enough? Having to wait for it to return could drive you mad.

And then I thought "linear actuator" - 1500 Newton's, 1 metre stroke length - would that work?
It's a buy new listing, so hopefully not forbidden: https://www.ebay.co.uk/b/Linear-Actuato ... d9ffe56671

You can "shop by stroke length" Again, it may be too slow for your frenzied output requirements.