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torker
03-06-2008, 12:48 AM
Hey guys! Here's where I am with the lift cylinder deal.
Got done that welding pics thing tonight...fed up...went back to the shop and worked on this. Gave the camera time to rejuvinate the low batteries so I snuck a couple pics.
All I have left to do to the mount is drill and tap 3 holes. Got the thing welded out a few minutes ago.
Run the lines...mount the raising valve and it's done.
http://img.photobucket.com/albums/v210/torker/DSC00001-42.jpg
http://img.photobucket.com/albums/v210/torker/DSC00002-28.jpg
Now I AM played out...lol!
Russ

wierdscience
03-06-2008, 08:58 AM
That's the purpose of all this moderization,so we aren't as pooped out at the end of the day:D

torker
03-06-2008, 09:03 AM
LOL.. Darin. it's a lot of fooling around but this saw is pretty long. You need to go for a little hike to grab the lift handle at the end of every cut. Time is money!

Bill Pace
03-06-2008, 09:18 AM
LOL... You need to go for a little hike to grab the lift handle at the end of every cut.
Especially if youre doing it in "the bag loader shuffle" mode, huh, Russ? Then have to LIFT the dang thing....ouch!

How is the ole backbone? you havent mentioned it .... and obviously you still goin 90mph

PS. You come up with some neat s**t!!

torker
03-06-2008, 09:26 AM
Bill...the back is slowly getting better. Yup..I'm still doin the shuffle thing. I think what is helping the most..I finally quit lifting heavy chit and I quit bending over so much. Sorta walking like I got a broomstick shoved up my...well you know...but it helps. Laying around hurts the most so I keep moving/working.
The saw project...trying to make a silk purse out of a sows ear...lol!
Soon it'll have all the features of the $12,000 Hydmechs I used to use...all for under $1000.

torker
03-06-2008, 02:54 PM
Ha...I'm not much for saying "sweet" but if I ever was it might be about this.
It's pretty damm nice!
If I would have had this saw for quite awhile..I woulda said.."Geez..I shoulda done this long ago"!.
But of course I just got it so...
Final install of lift cylinder.
Cool rating on a scale of 1 to 10...gotta be a 10! Lift a lever and the saw raises...priceless!
I love this thing!
Notice the metering tap on the top of the cylinder... anyone guessed Chev radiator draincock...you win a bag of stale popcorn :D
I was thinking of all kinds of ways to release the air from the cylinder...don't need it with the tap...and this valve bleeds the air out in the bottom position.
Only things left...I've got a raise limiter figured...very simple. A normally open mechanical type lever control valve. I'm going to steal Johns cable/pinch bolt idea and this will close the valve therefore stopping the saw from raising were I want it.
Have to move the mag switch yet and add the limit switch Evan sent (thanks eh).
I could have made a very fancy enclosure for this and spent a pile on fancy bulkhead fittings to tidy it all up...but what for. It's funtional and easy to work on.
http://img.photobucket.com/albums/v210/torker/DSC00001-43.jpg
http://img.photobucket.com/albums/v210/torker/DSC00002-29.jpg
Russ
And no...that's NOT blood on the damm floor! The floor is red...that's water. I haven't cut anyone for a couple weeks.

Doozer
03-06-2008, 04:15 PM
Why do you need two cylinders?

--Doozer

macona
03-06-2008, 04:28 PM
Hes using one cylinder to control the downfeed, the other he is using to raise the bandsaw with compressed air.

Doozer
03-06-2008, 04:41 PM
I know what both cylinders do, but why the need for both?

--Doozer

torker
03-06-2008, 05:23 PM
I know what both cylinders do, but why the need for both?

--Doozer
I never started off thinking about a lift cylinder til I saw Johns setup. Twas an after thought...I just copied his....sorta.
I think the hydraulic cylinder would be better for the control of such a heavy saw frame....but then I'd need a pump to power it to use as a lift.
This is quick and easy.

Doozer
03-06-2008, 05:30 PM
Perhaps you could use an "air over oil" reservoir. Pressurize the oil, which would normally be vented, with compressed air and the oil will flow to lift your saw. You could probably use the air valve you already have. You can still use you needle valve to control the speed on the oil side as well. Just another way to do the same thing. Thought it might save you some parts. Looks cool though.

--Doozer

torker
03-06-2008, 06:03 PM
Oh boy...always another way to skin a cat! OK doozer..I'm all ears. The downfeed side is a closed loop. How would I get air to just push on the one side? Then how would I exhaust the pressure from that side to lower the saw again? The air I'm using now is no problem...just blow the air out into the shop. Oil...gotta be more complicated.
HOLY SMOKE! I just took the spring off the back of the saw to smooth out the last bit of downfeed. I thought the saw was heavy before. Now it's just rude. I'm thinkin I can put up with a last twitchy bit.

John Stevenson
03-06-2008, 06:18 PM
Russ,
Just one ram, double acting, top port left open or filtered.

Make up a box out of a bit of 4" box section about 5" tall, weld up into closed box with sealed filler at top.
Two connections needed, one at top for air, one at bottom to connect to lower cylinder connection.

In this pipe you fit a one way adjustable restrictor, an air one will work.

Now 3/4 fill the tank with hydraulic oil.

To raise you apply air to the top of the oil via the top pipe, this lifts the cylinder / ram / frame
When you release the air the frame forces the oilback into the tank via the adjustable valve. when down apply air and it will lift up very gracefully.

It's well worth remembering this air over hydraulic trick to get steady movement.


[ Edit ] I only added another cylinder to my saw as it alreday had a good working damper cylinder on it.
If it had been missing the damper cylinder or it was broke I would have gone the above method.


.

torker
03-06-2008, 06:33 PM
Thanks John! Holy...that's so simple even I could build it! I JUST found out I have interferance problems with the two cylinders right at the top of the stroke. Was just going to hack up the mount to change it. I'm thinking now...I may leave it...add the air over hydraulic deal...then I'd have a spare air cylinder for yet another project...gawd I love this place!

torker
03-06-2008, 06:35 PM
Doozer...Thanks for the heads up!
Hey...now I can start a new thread "So...I got a spare air cylinder" :D

John Stevenson
03-06-2008, 06:47 PM
True story.

A customer of mine that builds machines for the oil industry was asked to build a ball grinder, Alistair no tittering at the back :D

These balls are the ones that go in the 1/4 tun valves you see on air and steam lines but in oil instalations these buggers can be 1.5 meters in diameter, that's 5 feet in old money.

Obviously the machines are big, so the first big one they built was designed to have clamshell doors with air cylinders to open and close.
Opening was fine, air was applied and using flow valves the doors opened up.

Closing was a disaster, air was applied and for a while nothing happened and then BANG they closed that hard the windows nearly fell out.

No amount of playing with the air valves could make it better as all that happened when you throttled them back was it would just build up until it had enough pressure to move and then gravity took over.

Just fitting an oil tank on the rear cured all this and you could get the doors closing at any pace you wanted.

.

torker
03-06-2008, 07:29 PM
John..lol! I worked in a mine one time. They had air powered everything down there. Some of the gates and stuff would have cut you in half if you ever got caught in them. Must be the same thing.
Just thought of something...an air powered vise for the saw. Geezuz...laziness is really taking over huh?

Doozer
03-06-2008, 09:18 PM
Air powered vise... This is gunna be one sweet saw. John is right on with the reservoir construction. On the cheap, perhaps you could use an empty hand held propane torch cylinder. Volume would be about right compared to your hyd ram. Keep posting pics of your progress.
--Doozer

John Stevenson
03-07-2008, 03:59 AM
John..lol! I worked in a mine one time. They had air powered everything down there. Some of the gates and stuff would have cut you in half if you ever got caught in them. Must be the same thing.
Just thought of something...an air powered vise for the saw. Geezuz...laziness is really taking over huh?

Not a bad idea,


.

Oldbrock
03-07-2008, 01:53 PM
Russ, don't answer this, I don't think you have time:D How many Russ's are there and do you ever sleep? I have never known anyone with such efficient use of time. Do you carry a laptop strapped to you and communicate while you're working. The back problem doesn't seem to have slowed you down. Do you have an anal broom as well:D or does the gurl do the cleanup? You have so many projects on the go I can't keep up. Your energy is exhausting me:mad: Peter

torker
03-07-2008, 06:18 PM
LOL! You guys are funny! Ya..I sleep and ya..I'm slowed down a bit.
Buuut... I did get the new hydraulic tank finished today...waiting for the paint to dry right now. I'll be trying that sukker out tonight!
The air powered vise will be a challenge. Not much room under the blade for the cylinder. But I've got a plan... (Oh no..not again!)
Pics at 11 :D

torker
03-07-2008, 07:44 PM
Hey guys...I need some magic here. I got the system all hooked up...bled all the air out of it that I could get???
Hook up the air... (100 psi at the cylinder) Hit the lever...takes about 5 seconds then it starts to lift just right.
Lifts good for 3 1/2" inches then quits.
Won't lift anymore even if I raise it by hand...then the last couple inches it starts to lift again. I put the spring back on before I even tried this. It's not that hard to lift through out the travel. The other air cylinder lifted this very easiliy...I really had to turn the air discharge nearly wide open on the top of the cylinder so it didn't slam the saw up.
Any ideas what I'm doing wrong?
Maybe mechanical advantage issues?
How big a deal would air in the hydraulic part of the system be?
I'd hate to have to change the mechanical advantage as it will greatly effect the lowering part of the system????
Thanks!
Russ

Doozer
03-07-2008, 07:47 PM
Could you post a pic of your plumbing and which way your check valve is pointed?
Any air should naturally make it's way back to the tank.
Are you using the upper or lower mount location? Maybe that is changing things.

-Doozer

torker
03-07-2008, 07:52 PM
Doozer.. I gotta go to town to get some batteries for my camera. The pipe goes from the bottom of the tank..up through the valve on the straight through side...if it went the other way it would go through the metered direction. I'm wondering if that speed valve may not have a big enough hole to flow oil??

torker
03-07-2008, 07:56 PM
Doozer..one more thing...I unscrewed the restrictor needle all the way in the speed valve. The saw just screams down when I shut the air off.

Doozer
03-07-2008, 08:01 PM
Just thinking out loud... If the check valve/needle valve were restrictive, it should only go slow, but pressure should still be there. You say it stops completely at one point? Check valve arrow points to the cylinder,right? Is the internal spring bad or is the check valve position sensitive?

-Doozer

torker
03-07-2008, 08:04 PM
As soon as I'm done eating I'll run dowtown for batteries. In the meantime...
Air into the rotary valve...3/8" tubing for the air into the top of the tank.
3/8" tubing out of the bottom of the tank....goes up into a lever type valve then right into the (air) speed valve. This is then plumbed into the bottom of the cylinder. The top opening of the cylinder has nothing in it at the moment. All tubing and fittings are 3/8"

torker
03-07-2008, 08:09 PM
You got me...I don't know. I wonder...if I cracked the fitting at the bottom of the cylinder...It should tell me if I have pressure there. Or that's maybe dumm. I should maybe have a pressure guage to really know where I'm at.

Doozer
03-07-2008, 08:14 PM
Thought of one thing... If that needle/check valve is used from something else, I have seen the failure mode of those valves to be where the tip of the needle breaks off and sort of floats in the valve, making very erratic adjustment. They can act fine for a while, but the tip can then jam and then things either go real fast or real slow. Just a thought.

-Dooz

torker
03-07-2008, 08:30 PM
Doozer..again I don't know. It's a brand new valve.....everything inthe system is new. However..it is a speed valve meant for air. I don't know if that matters.
The way the saw lowers tells me there is still a bunch of air in the system.
I still don't know if that matters. These are cylinders meant for air anyway.
After I come back I'm going to unhook the cylinder from the saw and see how it cycles.
The tank is 4"X4"X6" tall...shouldn't really matter right?

torker
03-07-2008, 09:01 PM
Hang on guys! Don't rack your brains. I'm a dummass. It's gotta be mechanical. Don't ask... (I'll tell ya later :D )

torker
03-07-2008, 10:51 PM
Ha! Here it is...all lifted up with one multi-purpose cylinder!
http://img.photobucket.com/albums/v210/torker/DSC00001-44.jpg
OK...I'm not really a dummass...well ok..I thought it had to be a leverage issue. Got back and changed over to the top cylinder. It has about two times the leverage. Lifted it like nothing...but REALLY frikkin slow.
Doozer...funny you kept pikkin on the speed valve. That's gotta be it. Before... I used this same cylinder setup with just air and it would slam the saw up. Now it lifts it ok...I can live with it but the valve must be the problem. I think it doesn't flow oil nearly as fast as air. I'm going to order a new one that flows more.
Here's the UGLY looking mess. I have to go get more fittings/tubing to tidy this ugliness up. I just grabbed lines and bent them around without cutting anything...just to get it working.
http://img.photobucket.com/albums/v210/torker/DSC00002-30.jpg
Here's the new tank we built. The gurl did pretty good. Her first pressure vessel welding...not a single flaw in a welded seam and no leaks.
http://img.photobucket.com/albums/v210/torker/DSC00005-5.jpg
This thing is just turning out to be too cool!
Russ

torker
03-07-2008, 10:56 PM
Oh ya..John S and Doozer...Thanks for your help guys. I just learned how to do a very damm cool thing here. I can see lots of uses for this air/hydraulic thing. I can also see me being broke all the time...buying cylinders and valves :D
Russ

Doozer
03-07-2008, 11:30 PM
Bravo! That tank looks especially schweet!!
When ya gunna start on the air vise?
Thanks for the pics.
--Doozer

John Stevenson
03-08-2008, 01:01 AM
OK...I'm not really a dummass...well ok..I thought it had to be a leverage issue. Got back and changed over to the top cylinder. It has about two times the leverage. Lifted it like nothing...but REALLY frikkin Russ

Use the lighest weight oil you can, thin with kerosene if nessesary.
Failing that increase the size of the tank so you have more surface area for the air to act on.

.

TGTool
03-08-2008, 08:25 AM
I've lost track of all the features incorporated through various iterations so I may be lost in the woods here. If so, just tune me out.

I should think you'd want a section of parallel lines going from the tank to the cylinder. Each line has a flow control valve and a check valve pointing the opposite direction. One control valve governs the up the the other the down. If the circuit is such that it should be free flow through a check valve in the raise direction then I'd agree with John that it's a viscosity problem.

Jan

John Stevenson
03-08-2008, 08:49 AM
Do a search on ebay for hollow cylinder and you will come up with something like this.
120210033117

What you need to do then is to modify or make a new screw so the cylinder is under the fixed jaw of the vise and moves the thrust point from the handle end to the nut end.

The handle end is then free to move in the bracket but has a decent spring on it.

In use the vise is clamped by tightening the handle so it just makes contact with the work.
Final tightening is applied by the cylinder pulling the nut and moving jaw towards the work, the spring is there to stop it fouling the bracket.

Power is applied to the cylinder by getting an air chamber off a tractor trailer pushing a clutch master cylinder that then goes to the hollow cylinder.

Air pressure isn't sufficient to push one of these hollow cylinders with enough force to hold the vise. You need a differential air over hydraulic setup to achieve this.

Shout if you want a sketch.

.

torker
03-08-2008, 09:26 AM
Oh boy!
You sorta lost me there John. I'm not at all familiar with semi truck parts.
I'm sure a sketch wouldn't hurt!
A question... I'm using AW46 hydraulic oil in this. So where does that oil fall in the grand scheme of viscosities? Thanks!
Russ

John Stevenson
03-08-2008, 09:32 AM
Ok, I'll do a sketch.

[edit] bugger it, throw the screw away and drop one of these in instead. 290212430576

For oil if it's struggling on speed you want gnat's piss.

.

torker
03-08-2008, 10:00 AM
John..lol! The jack idea is brilliant! I'm thinking a little 12 ton would fit underneath perfectly. I'll have to go into town and measure one.
Question...how the heck do you get enough gnat's piss to run the hydraulic system this time of year? :D

Ian B
03-08-2008, 10:31 AM
John,

What will increasing the area of the tank do? It'll mean the fluid level varies less for any given cylinder movement, but I don't think it'll increase the pressure of the fluid.

To get a faster lift speed, I'd probably look at increasing the size of the piping from the tank to the cylinder.

Maybe you'll add an air over hydraulic hollow cylinder to your rack-feed tailstock barrel - instant power assist...

Great thread!

Thanks,

Ian

John Stevenson
03-08-2008, 10:46 AM
Ian,
100 psi acting on a 4" x 4" area will give 1600lbs force
100 psi acting on a 6" x 6" area will give 3600lbs force.

Unless I've got something wrong.
It's surprising just what force is needed on a cylinder this close to the pivot point.
My lift cylinder is 50mm diameter and works fine until pressure drops to the point where the compressor needs to kick in again and then it's touch and go whether it needs a slight nudge

My saw has a simple lever operated version of what I described originally, the fixed end of the screw is on a cam operated block connected to the lever.
In my case I leave the vise slightly undone, slide the work thru and pull the lever to clamp the vise.
It was made this way.

torker
03-08-2008, 10:59 AM
John..you got it right about the forces needed to lift the saw at near the pivot point. I learned about that last night.
I was concerned that my leverage was all out of whack so I unhooked the cylinder and tried to lift the saw by hand from that point.
Holy Smoke..I couldn't budge it til I put a cheater pipe on it.
This morning I worked at getting more air out of the system A slight improvement but I think you've nailed it with the viscosity idea. I put a heatgun on the tank and lines. It helped quite a bit.
The speed valve is still a problem as it has a lower flow rate than any of my other valves in the system.
Ian mentioned putting larger pipe from the tank to the cylinder. I think I'm ok there.. it's 3/8" pipe BUT...that got me thinking...the fitting we welded into the bottom of the tank only has about a 1/4" hole in it..maybe a bit bigger but that could be a problem.
I have to tidy up and replace some of the plumbing so I'll have to deal with the drippy mess one more time. That'll give me a chance to take the tank off and drill the hole out larger.
BTW...with 120 psi right now...warm oil etc...the saw lifts at just the perfect speed.
Cold oil and lower pressure..not great but I'm very close to where I need to be. It's almost a done deal.

Ian B
03-08-2008, 12:03 PM
John,

I think you're mixing pressure in a fluid up with force on a piston rod. No matter what area the fluid in the tank has, the pressure at the fluid outlet will always equal the air pressure that you apply to it (plus a trivial amount fir the hydrostatic head). Apply 100psi of air, you'll get hydraulic fluid at 100psi.

What *will* make a difference is if you then apply that fluid to a 4" square or a 6" square piston - then you'll get a big difference in the force.

At least, I think that's how it works.

Ian

Doozer
03-08-2008, 12:58 PM
"...increase the size of the tank so you have more surface area for the air to act on."

It is a wash. It is a one to one ratio.
The number of pounds per sq in that gets transfered from the air to the oil is the same, as is the volume of the air that displaces the oil.
sq in Air = sq in Oil
lbs Air = lbs Oil
disp Air = disp Oil
For their to be a pressure increase, more air would have to displace less oil.
I hope I explained that right.
--Doozer

Your Old Dog
03-08-2008, 01:11 PM
Just thought of something...an air powered vise for the saw. Geezuz...laziness is really taking over huh?

I happen to have one of those... It's the plethora of bandsaw cylinders you have that I'm short on !! :D Maybe I'll go out to the shop, take a picture of it, just to rub it in your face :D

Your Old Dog
03-08-2008, 01:14 PM
The air powered vise will be a challenge. Not much room under the blade for the cylinder. But I've got a plan... (Oh no..not again!)
Pics at 11 :D

Can we see a picture of your shoes and did you make them too? :D

Doozer
03-08-2008, 01:16 PM
...Also, would you consider anti-freeze for the working fluid? Viscosity would be very stable with hot and cold temperatures. Straight anti-freeze would not be corrosive and leaks would be easier to clean up. You would have to flush your system with mineral spirits and then alcohol to clean the oil out. Many gas charged lift struts (think car trunk lids and hoods) use anti-freeze in them as the dampening fluid before getting charged with nitrogen.
-Doozer

dockrat
03-08-2008, 01:23 PM
Can we see a picture of your shoes and did you make them too? :D

He moves around so fast his feet never touch the ground...he dont need shoes :D

BadDog
03-08-2008, 01:30 PM
I've got one of those 20T air over hydraulic cylinders on my press. Quite respectable for the cost. But rather slow. You can also get nice little aoh pumps fairly reasonable. They look like little small shoebox sized things with a rocker on top, an air fitting on one side, and hydraulic on the other. I had those on my old Kansas Jack frame machine, and they work very well, and they have a coninuously variable control. However, they do use quite a lot of air in "fast" mode.

BadDog
03-08-2008, 01:38 PM
Here ya go. There are similar items on ebay now for under $200 (didn't look at closed). 300203108570 looks like s similar but cheaper version of what I had. 190203576972, 350032597714, 280205948828, 190203577933 just for a few more. Searching a simple "air hydraulic" turned up loads of them. And the best part, it will power any hydro system you hook it to. Mine had a hydro quick connect so I could swap them from towers, to lift, to portable tools as needed with minimal mess and fuss (though they sometimes leaked).

rdfeil
03-08-2008, 01:47 PM
Hey guys,
I'm no hydraulic engineer, but I have designed many air cylinder systems to move some fairly large valves and the problem is always converting line pressure (air, oil, water, applesauce :D ) into mechanical force/motion. The quick and dirty way to make a guess is to calculate the area of the piston in the cylinder in square inches (or mm or what ever) then multiply by the LOWEST available pressure. This will give you the lowest mechanical force applied to the rod. Do the same for highest pressure (with big cylinders things can and do break / bend :eek: )
For example, take a cylinder with a 1 inch piston (remember, the piston and the rod are not always the same size, especially in air cylinders) and 100 PSI air, do the math... Area = Pi*R*R or 3.14*.5*.5 = .785 In Sq. Now take that times the air pressure .785*100 = 78.5 Lbs lift. As you can see a 1 inch piston air cylinder really doesn't give much force. Now check out a 2 inch piston cylinder...
3.14*1*1 = 3.14 now times pressure 3.14*100 = 314 Lbs force. look at the difference, 2 inch vs 1 inch is 4 times the force all due to the area of the piston. The line size or tank size makes absolutely no difference as to the force applied, It will make a difference as to the speed that things happen. Also remember that air compresses and oil does not so you can get a smoother and steadier motion with oil. Air over oil has another big advantage in presses. The air can move the ram quite quickly into position and provide enough pressure in some cases to hold things in place. Then the hydraulics take over either with a hand pump or electric and then the BIG pressures make things move, not really possible with air. Think about a small bottle jack. When you pump the handle you are moving a small (1/2 - 3/4 inch) piston pump. Add the leverage of the handle and that little pump can deliver a GREAT pressure but little volume. Now take that pressure and apply it to a much larger (relative to the pump) cylinder and do the above math. Now your little handle being pumped by your arm is capable of exerting literally 100's of tons of force if the jack cylinder is large, but it is SLOW. Now add air over to the same jack. Through a series of check valves the air is allowed to push the oil from the oil tank into the lift cylinder thereby extending the ram. Now when you want the big force you hand pump the lever like before. The small piston pump provides the much higher hydraulic pressure to move the ram with great force but a lot less distance and at a slow speed.

I hope this helps a little in following pneumatic and hydraulic systems and how the pressures and forces relate through the cylinders. I know, this is greatly simplified and taks none of the other system variables into consideration, but like I said... I am not an engineer.

Sorry for the long post.

Robin

torker
03-08-2008, 02:20 PM
Robin...no need to apologize for the length of your post. This is all great stuff.

rdfeil
03-08-2008, 02:24 PM
Thanks Russ, I hope it helps.
Robin

torker
03-08-2008, 02:37 PM
Ya..it did. I'm thinking I may just order up a bigger cylinder. This one is marginal at best for the weight.
After reading your post.. my cylinder is 1.6 inch diameter. The next size up is 2.5. I'm suprised at the difference in power when the size goes up.
I'll try this one for awhile and see.
Thanks!
Russ

rdfeil
03-08-2008, 07:39 PM
Hi Russ,

Just remember, as I mentioned above, The important specification is the piston size, not the cylinder diameter. Extremely high pressure cylinders may be quite large but the piston is much smaller. This is to allow the cylinder walls to handle the pressures. A 1.6 inch cylinder may have a piston size of 1 to 1.25 inch to allow for cylinder wall thickness and threading for the end caps. A 2.5 inch cylinder may well have a 2 inch piston therefore the increase over a 1 inch would be 4 times the force. When they get really big (12 inch plus) be sitting down ( 12 inch piston cylinder at 100 psi is 11,300+ pounds of force) :eek:

Do a quick search for Bimba air cylinders, they have all of their specs online and you can compeer the physical size of the cylinder to the piston size.

Another thing to consider is the amount of force it takes to get things moving as compared to the force required to keep it moving. Most of the stuff I work with like this are sliding gate valves (large pipe, low pressure air). It takes a lot of force to get them to start moving off the seats, then very little to open them up the rest of the way, same for closing only not much to start them but a lot to seat them fully closed. We use them to route CO2 scrubbers in the fruit warehouses. This way one scrubber machine can handle multiple sealed storage rooms with different atmosphere requirements.

Anyway, I'm rambling again.

Good Luck
Robin

John Stevenson
03-08-2008, 07:45 PM
Hi Russ,

Just remember, as I mentioned above, The important specification is the piston size, not the cylinder diameter. Extremely high pressure cylinders may be quite large but the piston is much smaller. This is to allow the cylinder walls to handle the pressures. A 1.6 inch cylinder may have a piston size of 1 to 1.25 inch to allow for cylinder wall thickness and threading for the end caps.

Robin

All the air cylinders I have ever come across state the bore and stroke, not the OD of the cylinder, so in my case the 50mm x 200 means 50mm bore AND piston size by 200 mm stroke.

If it is double acting then you do have to take off the area of the rod from the piston to get the return size surface area but in Russ's case he's running single acting.

.

rdfeil
03-09-2008, 01:29 AM
Hi John,
I agree, I was just pointing out that the physical measurements may be misleading. If you are going by the manufacturers dimensions the cylinder will be specified as bore X stroke as you say.

Robin

Ian B
03-09-2008, 01:35 AM
Russ,

Instead of going for larger diameter, could you instead move the attachment point of the lifting cylinder further away from the pivot? It'll mean longer stroke, but it'll reduce the forces on the attachment points. Small jerks in the cylinder's motion will be less noticeable.

Ian

torker
03-11-2008, 01:43 AM
Hey guys! I worked on that damm saw all night. Rebuilt all the mounting points...put on the longer cylinder, etc.
Moved the top point out further away from the pivot.
Nothing...not a bit of improvement.
Straightened out all the plumbing so it looks decent...while I was at it..I plumbed it without the speed valve. That IS the culprit. Saw just flys up without it. But it also flys down as well. I could control it with the shutoff valve but it's too tricky to adjust the downfeed each time. The speed valve is the way to go but I'd like one with more flow.
I've looked in the catalogs I have and can't see a faster flowing valve than this. I'm sure they are out there but not in anything I have.
Tomorrow I'm going to get some kerosene as John suggested.
I did a hillbilly flow test tonight. The hydraulic fluid I'm using is pretty darn thick.
Automatic tranny fluid flows quite a bit faster than this stuff.
So..kerosene it is.
This has been a worthwhile project to say the least.
A bit of tuning and it's done.
Now for a bit of a break.. starting the new press tomorrow and the new tool holder for the lathe. That is... as long as none of them pesky customers stops by to bother me. Can't they see I'm busy? Sheesh...some peoples kids :D

rdfeil
03-11-2008, 02:27 AM
Russ,

If the speed valve allows the down feed adjustment that you need you could add a check valve to bypass the speed valve for high speed lift. If needed you could add a small valve in line with the check valve to allow lift speed adjustment. You might try to contact an industrial refrigeration company and ask them if they will sell you a 1/4 or 3/8 HENERY valve. They are just small valves that are used in ammonia refrigeration systems. They are fairly cheap and pressure rated. If you cannot find anything in your area let me know and I will check prices here and let you know. I use to work for a company that built ammonia refrigeration systems and can still buy from them at good prices :D for personal use, I won't tell if you don't:D

Robin