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Old 08-19-2010, 01:37 AM   #21
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Default Re: exp. design for a dbl. acting mini. hydraulic cylinder

Hi Kel.

At the moment, I'm using the plastic tubing, pretty much the kind for fish aquariums, air tubing.

That's the kind of tubing I used for my lift table, I don't recall having any kind of issues with that table project using that tubing, If it was expanding and causing problems I really didn't notice anything, however your RC projects may need more precision in its movement of the piston, while my table project was more like brute force just to get it to raise up.

Have you tried "smallparts.com", they may have the kind of lines your looking for.

Thanks for watching my thread.



Hello to everyone,
Update in my build thread:

As I said in my earliewr posts, my work in progress threads go from one idea of build to a completely different approach until I hit the right combination.

I hope this thread isn't becoming confusing, with all the detours I take.

With that said, I am now REDOING AGAIN the whole cylinder arrangement, the reason for that is, when I did my last cylinder, it came out great, However I clamped the cylinder after it was hollowed out just a little too tightly in my V block to machine the tube connector, and put a dent on the inside that will not ream out, the piston stilol works fine, but now and then there is a small catch in that area.

But as I was thinking about the best way to build these should I want to build several, I thought about using 3/8" dia. alu. rod, for the cylinder, and machining as one piece the tube connectors onto the end caps, that way less iterupted cutting on my lathe for the length of the cylinder, and use 3/4, to 7/8 dia. rod for the endcaps, with no offsetting in the lathe but all machining would be done on the mill for the tubeconnectors.

These are ideas I'm kicking around right now.



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Old 08-21-2010, 03:55 AM   #22
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Default Re: exp. design for a dbl. acting mini. hydraulic cylinder

To make the cylinder I used a piece of 3/8" alu.round rod.
I drilled and reamed it and tapped both ends 5/16-24 threads.

Now I turn my attention to the endcaps, I'm using a piece of 1" dia. alu. rod,

After dressing it up (face turning), I then machine a 1/4" spigot.
on the end



to use a die and make 5/16-24, outside thread, which will mate with the tapped ends on the cylinder.




Now a relief cut in the workpiece., to give clearance for ther form tool.



Now I machine down the 1" dia. to around 7/8" dia. This then will leave aroiund 1/4" material above the 3/8 " cylinder.



At my mill I begin the process of drilling the inlet hole and the machining off the sides and later the bottom off this.



Now using the forming tool I form the tube connector.



here it is right after the machining of the connector.



Bandsaw the right amont off.





Now I wrap plumbers tape around the threads and screw it on to the cylinder, and place the whole assembly back into the lathe for machining the finishing on the endcap.







Now drill and ream for the piston rod.



Still have the bottom cap to make yet.
But here is what it looks like with the tube connector machined into the endcap, rather then the cylinder.





Next is the making of the bottom endcap.



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Old 08-21-2010, 09:38 AM   #23
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Default Re: exp. design for a dbl. acting mini. hydraulic cylinder



Nice work. Your trials and solutions are very informative.

Ron
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Old 08-26-2010, 09:35 AM   #24
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Default Re: exp. design for a dbl. acting mini. hydraulic cylinder

Thankyou Ron, for the nice compliment.


Here is a test using air only, and it is coming from a small solder sucker, bulb,
I hooked the line up to the bottom cap inlet only, and left the top inlet open, to the atmosphere.

I have a lot of extra hose around 3ft. so this is a good test to see if a minute amount of air through a long distance of hose will have a positive effect on the piston, in the cylinder.

To my surprise, it has a very positive effect, also I never expected this, but when I let go of the solder sucker bulb, the vacume suction of the bulb pulls the piston back in again, there is a good seal with the piston, and rod, and the cylinder and top cap, where the rod passes through.

I can vary the amount of piston movement both directions, with very positive controle of squeezing the solder sucker bulb.

This test proves that the build is succesful so far, at least with air.

I need to finish the bottom endcap, then start working on the pistons and endcaps for both manual pumps, that I started earlier.

I'm hoping ,if I get this working properly, with water, or air, to move the piston in precise movements, to be able to make some sort of a dialing mechanism, where I could dial in on a wheel, left or right, which would push on levers for each manual pump, to actuate the piston in small incremental movements in relation to the amount of rotary turns on the dial..

That will ttake a lot of experimenting, and design work, which is what this project is all about.

Here is a video of the piston movements actuated by the solder sucker bulb.
The movements are kind of fast and non precise, as I was just trying to keep the video as short as possible for the upload time.

http://www.youtube.com/v/Wba8TlYf-vM?fs=1&hl=en_US

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Old 08-26-2010, 11:25 AM   #25
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Ron
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Old 08-28-2010, 02:08 AM   #26
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Default Re: exp. design for a dbl. acting mini. hydraulic cylinder

Thanks for the thumbs up Ron...

I'm making the bottom endcaps for the manual pumps, cylinders,
again the spigot will be formed on the cap as one piece, however this time the spigot (tube connector) will be elevated at 45*, so as to accomodate the tubing in more of a vertical configuration to the cylinder, rather than perpendicular to it.

I started out with 1" dia. alu. round stock, cut and machined to finished length.



Then a nub is machined onto it and threaded for 7/16 20 to mate with the bottom of its pump cylinder.



Then I center the spindle in relation to the center of the workpiece.




Vice tilted to 45*
First machine a flat that will be the top of the spigot.
Now drill the output hole for the spigot later to be machioned. Also this hole serves to line everything up as a reference, later when I need to get back to center for the final forming of the spigot.





Now I drill 4 reference holes to guide the 1/8" milling bit to rough shape out the spigot.



Now with the endmill, mill out the rough shape, of the spigot.



Back to centering up the workpiece under the spindle using the drilled hole as reference.



Now the finish forming of the spigot.





After milling out all the material around it.







And with the manual pump cylinder screwed onto it for a test fit.



Testing it's performance with the hose connected.



Next is to finish the other pump, endcap base, then start working on the pistons and such for each manual pump cylinder.




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Old 08-28-2010, 02:19 AM   #27
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Default Re: exp. design for a dbl. acting mini. hydraulic cylinder

Nice progress Hobby. I Like your methods.

Is that a home made cutter you used to make the spigot?

Kel

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Old 08-29-2010, 02:08 AM   #28
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Default Re: exp. design for a dbl. acting mini. hydraulic cylinder

Thanks Kel:

That is a homemade cutter, it's more like a corner rounding from tool, I machine the spigot to a rough 1/4" square, then proceed to use this forming tool, to make it round.

Please see post #14 page 1, I give a little detail of how I made it, with a quick video of it being used.
In the video I used fast speed, because my portable caqmera only takes 30 sec. of video, so I tried to get it working as fast as possible, but when I normally use it, I have it on low to medium speed, and very carefully plunge it onto the square post, a little at a time, until it starts forming the shape then when it gets to that point, it then cuts almost like butter, very easily and quickly, almost feeds itsself into the work.

Thanks...

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Old 09-03-2010, 03:27 PM   #29
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Default Re: exp. design for a dbl. acting mini. hydraulic cylinder

These are the parts so far, the further rightmost set of parts are the hydrailic cylinder and piston assembly itself, the left sets are 2 identical manual pumps, seperated into there individual components.



This is a rough mockup of the assembly for testing purposes only.



This is the first in several fine tunings that will be needed to make it as leakproof as posible.
First I checked to see how a rubber gasket glued to the top will work in sealing the water from leaking out the shaft holoe. It works well except that the leakage occured at the contact point of the cement itself, lifting the seal.



So I know that I coulod make a rubber o-ring gasket to fit snugly around the shaft to prevent leaking.

So the next process in this is to redo the top endcap, where I will make a screw fitting to encase and crimp tightly a rubber gasket against the top openeing of the endcap, where the shaft comes thru.

Also I noticed that there was leaking occuring around the cylinder and top encap connection, where the two screw together at, This is mainly due to the fact that I machined the square portion to close to the thread,



which gives very little surface area to make a seal between the cylinder end and the cap base.



So now I will make accomodations for these two failure points in the top endcap.
That's updated for now...

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Old 09-03-2010, 03:57 PM   #30
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Default Re: exp. design for a dbl. acting mini. hydraulic cylinder

Hobby, great progress.

If you use a thick oil, like hydraulic fluid or gear oil you will have a better chance of your seals sealing. This is because the molecular structure of water is very thin, where as oil molecularly thicker and will be less likely to leak.

Just a thought.

Kel



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