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DEVILHUNTER
08-08-2016, 03:55 PM
Changing tools is taking to much time to my, and nowadays time is a limited resource in my life, so I though it would be a great idea invest some of my time in a power drawbar. It will use the Tormach Tooling System, for those who don't know it, it's just a stright shank tool holder mounted in a collet in the spindle. The tool holder also has a flat ring that allows you to have Z axis repetitivity. If you want to know more about it, just google it since is becoming pretty popular in the hobby world because it's simplicity and cheapness.

The power drawbar cylinder I'm going to use is a 4 stage cylinder. This is in order to multiply the force of the cylinder. It will have around 2 tons of force, in fact I'm having problems to fing Belleville washers strong enough. The idea is to make sure I won't have any tool slipeage. My splindle is MT3 so it will clamp the shanks pretty tight.

I have designed the power drawbar to be modular. I can easily add or substract stages, or even enlarge them. It will be the floating type. Other types use a smaller one stage cylindern and multiply the force with a lever, but this applies all that force on the spindle bearings, and with a quill this is not a great idea.

The cost of the project will be around 100, taking into account I had to spent 30 in o-rings, while I'm only going to use less tan 20. Here you have the CAD model, with the work in progress 20 tool ATC.

https://s25.postimg.org/9tuo4f5zj/cad.png

Started buying lapped tube for hydraulic cylinders. 100mm ID and 110mm OD. I bought it 600mm long, although I only need around 150mm, but decided it will come handy to have it around for other projects.

https://s25.postimg.org/lk8llsyrz/IMG_20160601_211626.jpg

After cutting the slices with the hacksaw, mounted my ER40-to-4 jaw lathe chuck in my mill and turned them to size.

https://s25.postimg.org/8u4d8pqtr/IMG_20160607_113501.jpg

https://s25.postimg.org/aakh4lj4f/IMG_20160609_102810.jpg

DEVILHUNTER
08-08-2016, 04:11 PM
Mounted my vise sideways so I can easily swap the parts, drilled and tapped the holes where the pneumatic fittings will go.

https://s25.postimg.org/jngguyxhr/IMG_20160609_172310.jpg

Machined a T-shape nut that will go threaded in the top of the spindle. Threadmilled it and used a small T-slot cutter to make a relieve groove for the threads.

https://s25.postimg.org/d77i4voy7/IMG_20160606_110025.jpg

Funny how all the chips got magnetized and kept on the tool.

https://s25.postimg.org/5d6wjhh5b/IMG_20160605_140722.jpg

Finally this si how the stack of spring washers will fit. )))((()))((()))((())). Great thing about belleville washers is that you can get whatever force and legth of travel of your spring just you want by stacking them together.

https://s25.postimg.org/40p7hljpr/IMG_20160606_110827.jpg

pinstripe
08-08-2016, 04:32 PM
Nice. Did you consider making an electric one, or was it always going to be pneumatic? Mine is pneumatic, but I do wonder how much quieter an electric one might be.

phil burman
08-08-2016, 07:12 PM
Nice. Did you consider making an electric one, or was it always going to be pneumatic? Mine is pneumatic, but I do wonder how much quieter an electric one might be.

Is such an animal available, any links please?

Phil:)

DEVILHUNTER
08-08-2016, 07:17 PM
Always designed it to be pneumatic. Does yours works with an impact wrench? Mine should be quiet, and you can allways use a noiseless compressor. It won't use too much air, even a homemade one with a fridge compressor would be enough.

What I do though about is my mill motor. Currently I'm running the DC original motor (1.1 KW), which won't last long. I have an 1.7 KW AC servo motor that is perfect size to fit in there, even could be bigger. The problem is that I don't have the servo drive yet. I will try with a Vector VFD that is supossed to be able to run permanent magnet motors and, if it doesn't work, I would buy a 3 phase one. The 3 phase would be way bigger than the servo, and probably the power drawbar won't fit with that motor installed. In that case I would use a small hydralic cylinder conected to the power drawbar.

Well, to make the piston and intermediate plates I used a 10mm 7075 aluminium plate I had at home. It was going to be for my 4th axis but finally decided to use steel there so I can hold indicators. The plates were perfect to make two pistons and two intermediate plates each one, but I had to be carefull with the hacksaw to get the cut straight.

https://s25.postimg.org/dnsprbcpb/IMG_20160718_113728.jpg

After the cut, I held the plate in the table, with some wood under it, with a couple of clamps on the sides.

https://s25.postimg.org/hy7dmwhsf/IMG_20160728_120549.jpg

In that position, I drilled the center and used the boring head to increase it up to 20mm snug fit. Then, without unclamping the part, I added another clamp in the center hole. After tighten this clam, I unclamped the firsts ones, now I was ready to mill the outside.

https://s25.postimg.org/m8m1ihmvj/IMG_20160728_150548.jpg

Then used the small T-slot cutter to make the o-ring groove.

https://s25.postimg.org/pgqivj95b/IMG_20160728_154654.jpg

DEVILHUNTER
08-08-2016, 07:40 PM
Ooooooopsss!!! I made a UNI-Torx nut! While making one of the intermediate plates I didn't realized in the CAM were one of the last contours was going to start and I crashed the machine at G0 (3500 mm/min) with the clamp. Luckilly I was nearby and could stop the machine before something worse happened. Funny thing is that the cutter didn't get damaged at all.

https://s25.postimg.org/pi0goyaz3/IMG_20160729_154522.jpg

Since the intermediate parts were going to be machined in the back too, and the clamping and unclamping of this setup was too slow, I decided to go into another aproach. Clamped my small toolmakers vise to the mill and put a piece of the 20mm chrome plated hydraulic rod vertically on it. Indicated the exact center of the rod and drilled a through hole on it. Now I can just fit a part, install a clamp on it and hit cycle start in just ten seconds. What was even greater was that the vise size was perfect, allowing me to mill the side of the parts in one setup without hitting the vise.

https://s25.postimg.org/vkcot6ost/IMG_20160731_122912.jpg

Decided to go ahead and blue the steel parts in a caustic salt bath. It was my first time trying and turned out great, not perfect, but great. The cylinders finish was quite black (ST52 steel), the T shaped nut (F125/4140) was kinda brown, but I really didn't bother to finish it with sandpaper before. I did finish the aluminium parts with sandpaper, also rounded the edges of the piston plates in the mill with a woodworking bit. I think the contrast between the clear aluminium and the black steel is very pretty. Also cut and chamfered the chrome plated hydraulic rods.

https://s25.postimg.org/9eesxnuof/IMG_20160801_135242.jpg

Checked the height of the pneumatic fittings holes were right once the intermediate plate were mounted.

https://s25.postimg.org/a2nnglte5/IMG_20160801_134953.jpg

RB211
08-08-2016, 09:06 PM
No lathe?

Sparky_NY
08-08-2016, 10:38 PM
Very nice ! I am curious what your mill is, a RF45 type?

I have a RF45 type in process of being retrofitted to cnc. I used a bought 3 stage pneumatic cylinder in the same fashion as you are, only real difference is my spindle is R8, I got the TTS R8 collet. I also have a toolchanger in mind for the future.

George

pinstripe
08-09-2016, 07:29 AM
Is such an animal available, any links please?

There probably aren't many commercial units. I know there is this one http://www.grizzly.com/products/Electric-Power-Drawbar/H8368

Most are custom built from cordless impact drivers.



Always designed it to be pneumatic. Does yours works with an impact wrench? Mine should be quiet, and you can allways use a noiseless compressor. It won't use too much air, even a homemade one with a fridge compressor would be enough.

Yep, mine is an impact type. Most of the noise is from the impact, but the motor isn't what I would call quiet. It spins at 3,000 RPM. I do have a "silenced" compressor. Nowhere near as quiet as a fridge compressor, but pretty good.

This is an interesting project. Thanks for taking the time to post it here.

boslab
08-09-2016, 09:24 AM
Ooooooopsss!!! I made a UNI-Torx nut
I had an odd expirience years ago with a NC drilling machine, it was drilling through 6mm mild steel bar for pins to be stuck through and pressed to make dog combs (I think they were for dogs but I had enough hair to use one in the 80s), the titex drill bits were breaking continually, I called the drill company and a rep came, he looked at the machine and upped the drill feed by about a factor of 10, I was horrified, started the machine, bear in mind the holes were .06 or less, I could hardly see the thing drilling, it was slamming the drill bit into the steel like a sewing machine, the drill didn't break, it lasted all day till the holes started wandering as it had got blunt.
The fact that sometimes you hit a cutter hard seems to save them, I cut through a 1/4 steel bolt yesterday with a wood circular saw, brand new blade, I thought that's buggered it, I checked it with a magnifyer, one tiny chip on one tooth, I think I ran out of lack for this week!
Nice job btw, love festo fittings myself
Mark

John Stevenson
08-09-2016, 09:33 AM
I query the pressure of the cylinder and springs on a MT3 taper ?
On an MT3 it takes roughly twice the load to release as it did to tighten.

DEVILHUNTER
08-09-2016, 11:03 AM
No, no lathe... yet, RB211. I can say I'm making one.

My mill is a WEISS WMD30, a bit smaller than the RF45 type, Sparky_NY. I want my ATC to be simple, just another pneumatic piston plus a stepper motor to index the tools. Point was I want the tools to be in a full step of the motor, so I can choose only 10 or 20 tools for the ATC. Luckily when I was drawing it I notice that the 20 tools one fits just perfect without hitting the column by just a few millimiters. Before knowing that I was thinking on a second ATC in the other side, or a chain type one.

The pint is that with the MT3 splindle I can't use the impact power drawbar since they have the tendency to self lock because of so small taper, pinstrip. Also mine is going to by way cheaper than that electric one!

Nice history boslab, remind me when you are starting in the machining world and you try to be so carefull with your tools that the rubbing destroy them.

That's an interesting point, Sir John. With the stack of disk springs I'm going to use, I got around 8700N of preload at 75%. My multi stack piston is 100mm in diameter, and the rods are 20mm. That gives me a bit more than 300 cm^2 of efective surface. My compressor will be set between 6 and 8 BAR, so that is 18000 to 24000 Newtons, I think that is goint to be more than enough to release the MT3.

This week should arrive the tool holders and the material for the final plates I need. The o-rings and pneumatic fitting are going to take more.

bborr01
08-09-2016, 12:22 PM
When I saw the term "4 stage cylinder" I was expecting to see a cylinder with 4 different diameters that could fire independently of one another. Those look to be all the same size. It doesn't seem like having them being the same size would give you any more pull force than a single one. Or am I missing something here?

Brian

Noitoen
08-09-2016, 12:36 PM
It has the same force as a cylinder with double the diameter. Think of 4 cylinders pushing the same direction at the same time.

Sparky_NY
08-09-2016, 12:46 PM
Here is a link to a commercial cylinder of the type being built, for those that are not familiar with them.

http://www.fabco-air.com/products/multipower/multipower.html

DEVILHUNTER
08-09-2016, 02:04 PM
Exactly, the point on the multi stage ones is to increase the surface (force) without increasingt the footprint. This one is equivalent to one with around 200mm diameter piston.

Mike Amick
08-09-2016, 03:37 PM
I'm really amazed that you need that much force to tug on the drawbar. Not doubting you, you
obviously know what you are doing. Just surprised.

So your cylinder is going to have an inlet between every plate ?

I would love a power drawbar .. but would prefer electric.

Yours is the most complicated and ambitious one I have seen and can't wait to
see how it turns out.

boslab
08-09-2016, 03:41 PM
You could use an air over oil intensifier and a smaller hydraulic cylinder as a variation
Mark

bborr01
08-09-2016, 03:55 PM
I still don't understand how they can get more pressure unless they are in parallel. It seems like if they are end to end type of arrangement they would all max out the same as if there was only one cylinder.

Anybody have an explanation of how they work? I looked at the fabco site and didn't see it explained.

Brian

Lew Hartswick
08-09-2016, 04:03 PM
I still don't understand how they can get more pressure unless they are in parallel. It seems like if they are end to end type of arrangement they would all max out the same as if there was only one cylinder.

Anybody have an explanation of how they work? I looked at the fabco site and didn't see it explained.

BrianI'd appreciate an explanation also. With some sort of a sketch to show how the multicylinders add.
..lew...

J Tiers
08-09-2016, 04:38 PM
Presumably each section has to be a complete "half cylinder" in itself, with an end piece, rod seal and piston. The next cylinder's end piece would be the opposite end for each cylinder except the end one.

Pressure is then developed between the non-moving end piece and the piston, for each cylinder, accounting for them adding up.

How each gets linked to the rod without some feature that would foul up being fed through the seals might be interesting..........

John Stevenson
08-09-2016, 04:50 PM
Simple.
Image two completely separate thru rod cylinders, on air each cylinder has a pull [ or push ] of 1,000 pounds.
Put them side by side, body fixed and rod onto say a blade and there will be 2,000 pounds of force.
Now stack the two cylinders, hold the body's and apply air and you still have 2,000 pounds of force.

Each cylinder has to be added to the first.

John Stevenson
08-09-2016, 04:58 PM
Couple of months ago our local ALDI had some 1/2" drive impact wrenches made to operate from 240v AC for 30 so I grabbed a couple.

Tried one on the Bligport with a 3/4" drive impact socket as supplied and it works fine. Nice feature on these is that loosening ir full force wheras tightening is torque limited. They are made for wheel nuts etc and they don't want anyone screwing a lug bolt off.

The idea of getting two was I wnat to butcher one to use just the guts and no handle, the switch being replaced by relays so I can use simple buttons on the side of the mill. Unlike full air ones I will have to pull this down onto the drawbar but at that point it it hit a micro switch to enable the buttons.

Reason I don't want to go to air is my big compressor is big and if I only want to do a simple quick job I have to wait for it to fill and then all the attendant noise.

Using electric is quick and a lot quieter.

J Tiers
08-09-2016, 05:53 PM
Simple.
Image two completely separate thru rod cylinders, on air each cylinder has a pull [ or push ] of 1,000 pounds.
Put them side by side, body fixed and rod onto say a blade and there will be 2,000 pounds of force.
Now stack the two cylinders, hold the body's and apply air and you still have 2,000 pounds of force.

Each cylinder has to be added to the first.

Naturlich, aber.....

The mechanics of getting them stacked up and operating bidirectionally is the interesting part.

DEVILHUNTER
08-09-2016, 06:10 PM
http://enginemechanics.tpub.com/14105/img/14105_157_2.jpg

Here is a cross section of a tandem cylinder. If you inyect air in A and C while B and D are conected to the atmosphere, you get twice the force. Then since I don't actually need force to retract the piston, I can only apply air to B or D, or even use a spring. NYCCNC has a great video disassembling his Tormach power drawbar that maybe helps explaining how it works. Of course the travel is way lower, on mine will be less than 15mm.

https://www.youtube.com/watch?v=gkE0vk_oDAU

Yeah Mike Amick, the cylinder have inlets for every piston. Think about it as several cylinders that then you just join their saft.

You are right bobslab, if fact I'm using this system in the brake I use in the lathe/4th axis headstock I'm finishing. It have a small pressure booster, an air cylinder conected to a samaller hydraulic one to generate 25 times more pressure. It's similar to what I coment on #5, but at first I try to avoid it since the maintenance of the hydraulic one is more critical. If one of the seals of the pneumatic one get damaged, it will just leak some air but it will keep working. If I have an oil leak I will stop working because it's a closed circuit. I can build an air powered hydraulic pump to use with an oil tank, but is way more complex.

The rods are already joined to the piston plates, J Tiers. I used anaerobic retainer to bond them together, I love that stuff. Instead of a long rod, like the one on the picture, each plate uses ist's own small rod. The first rod pushed the second, and so on.

pinstripe
08-09-2016, 06:23 PM
Reason I don't want to go to air is my big compressor is big and if I only want to do a simple quick job I have to wait for it to fill and then all the attendant noise.

That was similar to my thinking. Electric would be more convenient for me because I don't always have the compressor running. I also didn't have air near the mill. I have run air to it now. I will probably make a modification so that I can use it manually if needed. My compressor is small a quiet, but the power drawbar is loud.

Does anyone know why power drawbars are predominantly driven by air? Is there some benefit over using an electric motor?

John Stevenson
08-09-2016, 07:03 PM
Basically cheap and simple on air.

I am going off air as being wasteful, noisy and not so convenient.

Some years ago I bout an air tapping head, the type on cantilever arms.

http://www.stevenson-engineers.co.uk/files/tappinghead1.jpg

This set goes from 3mm up to 12mm and it works well on the smaller sizes but struggles a bit on the larger. On long jobs you do have to wait and I have a 15 cu.ft compressor.

What I found though was if I only has 3 or 4 holes to tap and the compressor hadn't been on I wouldn't bother and tap them by hand.
So one day I set about converting this.
Canabalised a 1/2" air drill to get the reduction drive and linked it to a 3/4 hp 3 phase motor so I could use single phase via a VFD for speed control.

http://www.stevenson-engineers.co.uk/files/tapping%20head3.jpg

Fair bit heavier so had to play about with some springs as well as the gas strut to achieve neutral buoyancy.
Works very well now and I can go up from M12 to M14 and it's available at the flick of a switch for just one or two tapped holes.

The lathe compressor hardly ever runs now and I rely on a small quiet dental type compressor for blowing parts out and the odd bit of air.
It's actually paid off quite well as I'm in the throws of a house move and workshop move to smaller premises and the big compressor can't go due to size, noise and no three phase.

All the old air tools have been given to one of my customers who does a lot of site work.

DEVILHUNTER
08-14-2016, 06:35 PM
Some updates. The last aluminium plates I needed and the steel one arrived this week. Also the toolholders, they are better than I expeted. Haven't checked the runout yet, though.

https://s25.postimg.org/qe2yrt1cf/IMG_20160810_132732.jpg

Unfortunatelly, when I was milling the last but one aluminium plate, the T-slot end mill broke. So now I'm waiting for the new tools to arrive.

EddyCurr
08-14-2016, 07:45 PM
Does anyone know why power drawbars are predominantly driven by air? Is there some benefit over using an electric motor?Study the before/after photos of Mr Stevenson's tapping arm.

An air motor is a considerably simpler device than an electric motor - this has implications for cost, size, weight, power, speed, to name a few parameters.

With air, one centrally located prime mover can power air tools, pneumatic controls, sprayers and what-have-you. Going electric means a motor on each device; in the case of the tapper, a VFD, too.

.

DEVILHUNTER
11-05-2017, 07:07 AM
Well, It's been a while since last updated this topic, and a lot of things have happened. First of all I want to comment that I started having a lot of pullout problems and chatter, no matter how hard I screw the drawbar. I even got some of the safts a bit damaged. At first I though it was the quality of the toolholders, but finally I discovered that the problem came from the collet. It was only gripping on the top of the saft. Changed the collet for another one and no problem since then.

After finishing all the plates and bars that hold the power drawbar to my mill, It all fitted pretty well:

https://s25.postimg.org/hkhmeqe4v/IMG_20160918_182926.jpg

Unfortunatelly, soon after that my original DC motor got burnt. I was already expecting that, so I had been making a timming belt conversion, but couldn't finish it before it happened. To finish the HTD 5M spindle pulley and the 30x30mm bars that will support the new motor I had to use and old cordless drill that I had to connect to a power supply since it's battery was dead:

https://s25.postimg.org/43prehbqn/IMG_20161017_190455.jpg

Using a router at the side of the headstock, made the plastic pulley and MDF adapters to an old washing machine motor:

https://s25.postimg.org/clz7iuku7/IMG_20161018_165154.jpg

https://s25.postimg.org/43prehyvz/426139615_127138.jpg

DEVILHUNTER
11-05-2017, 07:08 AM
I installed this motor in order to make the adapter for the new motor while waiting for the VFD, but turned out to be too low torque to mill even MDF. The motor I had and wanted to use was a 1.7KW AC servo motor, with the same size of the original motor. I bought VFD that was, in theory, capable of driving this motor, but I couln't get it working, so I finally bought a second hand 1.5-1.8KW 3 phase induction motor. Installed it with MDF and made all the final parts in aluminium. I actually messed up the pulley, made the bore 25mm while the motor shaft is 24.... I will have to make a new one in the future.

https://s25.postimg.org/whv6y1emn/IMG_20161116_195509.jpg

https://s25.postimg.org/mkk64yrlb/IMG_20161120_114928.jpg

https://s25.postimg.org/kfzt3vxof/IMG_20161212_142707.jpg

In the last picture, you can see the encoder disk I made from aluminium sheet stock. I probably won't use it, I will install an absolute magnetic encoder on the motor.

https://s25.postimg.org/9gelsb9u7/IMG-20161209-_WA0002.jpg

DEVILHUNTER
11-05-2017, 07:09 AM
But this new motor have a big problem, my power drawbar does not fit anymore! So now I have to go with an air over hydraulic system. Made a couple of pistons and cylinders, 30mm in diameter so the pressure will be around 300 BAR. This way I will connect the cylinder in the headstock with the cylinder in the air piston with a braided hose. It's very important that the hose is as rigid as possible radially. If the hose expands too much, won't be enogh oin to push the drawbar all the travel. Since the hydraulic system is closed, I have to ve very aware of any air trapped and oil leak.

https://s25.postimg.org/penbihecv/IMG_20161212_143424.jpg

https://s25.postimg.org/sy998awi7/IMG_20161212_143539.jpg

https://s25.postimg.org/44zp7n5rz/IMG_20161212_145455.jpg

And this is almost all right now. The braided hose should arrive soon, plus I still have to buy a new compressor. Now I'm thinking on through spindle coolant, but I will have to change the hydraulic piston on the spindle to get the coolant/air into the drawbar.

On parallel I have been developing my automatic tool changer, but I think it deserves it's own post!

https://s25.postimg.org/yz6y5e69r/IMG_20170725_114030.jpg

Bob La Londe
11-05-2017, 09:25 AM
I still don't understand how they can get more pressure unless they are in parallel. It seems like if they are end to end type of arrangement they would all max out the same as if there was only one cylinder.

Anybody have an explanation of how they work? I looked at the fabco site and didn't see it explained.

Brian


I'd appreciate an explanation also. With some sort of a sketch to show how the multicylinders add.
..lew...

I am sure its already been explained, but think of it like stacking weights.

Basically its 4 pneumatic cylinders. Each one is pushing on all the other ones. Each pneumatic cylinder is capable of so much force. Since they are contained in a fixed (immovable object) that force can only go in one direction. Pressing into the back of the next one.

Those of us who have pushed a car might rebel at the concept. If two guys push a car it moves. If one guy pushes a guy pushing the car then the guy in the middle collapses. However in the case of the pneumatic cylinder the piston rod can't collapse. The force is added just like stacking weights on a scale.

Sparky_NY
11-05-2017, 01:08 PM
Look forward to you doing a thread on your toolchanger. It looks great!

Bob La Londe
11-05-2017, 02:14 PM
One thing, and you probably already know this if you have researched TTS, is that the collet for TTS is machined flat so the ring on the tool holder consistently engages the nose of the spindle and does not hit the front of the collet. That way when a tool is added to the tool table on your machine its the same every time it loads.

dave_r
11-05-2017, 02:36 PM
I am sure its already been explained, but think of it like stacking weights.

Basically its 4 pneumatic cylinders. Each one is pushing on all the other ones. Each pneumatic cylinder is capable of so much force. Since they are contained in a fixed (immovable object) that force can only go in one direction. Pressing into the back of the next one.

Those of us who have pushed a car might rebel at the concept. If two guys push a car it moves. If one guy pushes a guy pushing the car then the guy in the middle collapses. However in the case of the pneumatic cylinder the piston rod can't collapse. The force is added just like stacking weights on a scale.

Wouldn't some kind of failure come into the picture? If you have two 20ton cylinders connected in series, I don't think you would want to try to use them to generate 40t of force...

Mcgyver
11-05-2017, 02:39 PM
great stuff - keep them coming

Black Forest
11-05-2017, 02:44 PM
Wouldn't some kind of failure come into the picture? If you have two 20ton cylinders connected in series, I don't think you would want to try to use them to generate 40t of force...

It would depend on the structural integrity of the materials used to build the cylinders. If the cylinder rods would only stand the 20 tons then yes you would be right. But if the cylinder walls and rod will handle 40 tons then it is no problem. Essentially what he is doing is increasing the piston area therefor increasing the amount of force that can be applied.

RichR
11-05-2017, 08:56 PM
Those of us who have pushed a car might rebel at the concept. If two guys push a car it moves. If one guy pushes a guy pushing the car then the guy in the middle collapses. However in the case of the pneumatic cylinder the piston rod can't collapse. The force is added just like stacking weights on a scale.

I think you are wrong. If you have 2 cylinders each capable of generating 20 tons of force and you connect them in series, you will wind up with
an assembly that can generate 20 tons of force with a longer stroke. If you want the forces to be additive, the cylinders should be in parallel and
the load evenly distributed between them.

doctor demo
11-05-2017, 09:42 PM
I think you are wrong. If you have 2 cylinders each capable of generating 20 tons of force and you connect them in series, you will wind up with
an assembly that can generate 20 tons of force with a longer stroke. If you want the forces to be additive, the cylinders should be in parallel and
the load evenly distributed between them.

I agree with what you are saying,but as I understand what the op as meaning is a stack of pistons on one common rod with separate chambers.
I think under those conditions it effectively puts the cylinders in parallel.

Steve

DEVILHUNTER
11-06-2017, 04:04 PM
Here is the post about the automatic tool changer:

http://bbs.homeshopmachinist.net/threads/74956-Automatic-tool-changer-for-my-mill

Yeah I know about the shorter collet for the TTS system. In fact I went a bit further with the collet so I can actually use flat tools, without the recess.

Bob La Londe
11-06-2017, 06:32 PM
I think you are wrong. If you have 2 cylinders each capable of generating 20 tons of force and you connect them in series, you will wind up with
an assembly that can generate 20 tons of force with a longer stroke. If you want the forces to be additive, the cylinders should be in parallel and
the load evenly distributed between them.

I think you are wrong. The stroke of the piston doesn't change because you have another piston pushing on the piston rod. LOL. The stroke of the piston regardless of how many there are is limited by the length of its cylinder.

J Tiers
11-06-2017, 08:01 PM
I think you are wrong. The stroke of the piston doesn't change because you have another piston pushing on the piston rod. LOL. The stroke of the piston regardless of how many there are is limited by the length of its cylinder.

He meant to attach the second cylinder to the first one's rod, I think. That , while a bit impractical, would add the strokes.

If you put both pistons on one rod, you can get more force, but the stroke is limited to that of one piston, the shorter stroke one.

doctor demo
11-06-2017, 09:15 PM
He meant to attach the second cylinder to the first one's rod, I think. That , while a bit impractical, would add the strokes.

If you put both pistons on one rod, you can get more force, but the stroke is limited to that of one piston, the shorter stroke one.

Way back in post#15 and 16 it is explained as to the op's intentions of how this will work,and a link to a commercial cylinder like the one he built.

Steve