Can two hydraulic cylinders of two different sizes, be plumbed together?

[Bigshooter81]

What about when retacting the cylinders? Could the larger one pull the rod or damage the packing of the smaller one?

No because the cylinders won't be connected, and actually the drawing above isn't exactly the way it's going to be.... the larger cylinder will push and pull like it does above, but the the small cylinder will push and pull the entire assembly on its own fulcrum. they will not share fulcrums, so the only overload potential is from payload.

 

[Luke'sScreenName]

I'm thinking this is for the car-eating, fire-breathing, robo dinosaur at the monster truck show? Am I right?

 

[Bigshooter81]

I'm thinking this is for the car-eating, fire-breathing, robo dinosaur at the monster truck show? Am I right?

Negative, but I'm sure in the wrong hands it could be!

 

[muddstopper]

If I am reading this right, you have a boom you want to make move a total of 65degrees, vertical/horizonal doesnt matter. Is there some reason the cyl must have 17in of stroke, or can one of a shorter stroke work. I cant see why you cant make it work with only one cyl, size the cyl to handle the maximum load and keep it simple.

 

[Bigshooter81]

If I am reading this right, you have a boom you want to make move a total of 65degrees, vertical/horizonal doesnt matter. Is there some reason the cyl must have 17in of stroke, or can one of a shorter stroke work. I cant see why you cant make it work with only one cyl, size the cyl to handle the maximum load and keep it simple.

I need 110 degrees of motion. It will essentially work like a hoe bucket, except instead of a linkage between the bucket and cylinder, there will be another cylinder. My attachment points on the machine side do not allow for manipulation of radial arcs based upon advantages leverage points.. ie: attaching the cylinder low on the lever to maximize swing with a given stroke allowance.

 

[pmsmechanic]

I need 110 degrees of motion.

So instead of trying to invent something new why don't you mimic the bucket curl linkage from a backhoe. It's a suggestion that I just thought of.

 

[CCWKen]

So instead of trying to invent something new why don't you mimic the bucket curl linkage from a backhoe. It's a suggestion that I just thought of.

I think is was mentioned before but you're right. A link is the way to go. Multiple cylinders will just make it look like some kind of 25 cent carnival ride.

I haven't had the chance to use the ones I have yet but I bought a pair of tandem axle spring mounts to use as links. Mounting the cylinder to the center basically doubles the curl range. The image below shows a spring kit but I bought the forged steel mounts individually at Northern Tool.

 

[Bigshooter81]

So instead of trying to invent something new why don't you mimic the bucket curl linkage from a backhoe. It's a suggestion that I just thought of.

As stated earlier, I need 17" of stroke length, but do not have adequate area to install a cylinder of that retracted length. Again, if I could utilize only one cylinder I would.

 

[CCWKen]

That's where the link comes in. It can double the stroke too. Look at the way it's already being done. Your situation is not new.

 

[Bigshooter81]

That's where the link comes in. It can double the stroke too. Look at the way it's already being done. Your situation is not new.

It can, but also halves the leverage, or with a larger cylinder to compensate, requires a ridiculously robust linkage design.

 

[CCWKen]

Like most backyard engineers that throw parts together and hope for the best, it sounds like you don't have your stress/design limits in mind. And nobody else here knows either. The suggestions are offered as a solution to a common problem. You can make your own links but the premade links above are for mounting two 3500 pound axles under a trailer. They make them bigger. A 17" stroke cylinder rod will need to be pretty "robust" too for full extension. The link can cut your cylinder length in half and perhaps allow for a slightly larger cylinder for the same or lower price.

But, you can do whatever you want. You seem convinced you need to build a carnival ride. :confused3:

 

[Bigshooter81]

Like most backyard engineers that throw parts together and hope for the best, it sounds like you don't have your stress/design limits in mind. And nobody else here knows either. The suggestions are offered as a solution to a common problem. You can make your own links but the premade links above are for mounting two 3500 pound axles under a trailer. They make them bigger. A 17" stroke cylinder rod will need to be pretty "robust" too for full extension. The link can cut your cylinder length in half and perhaps allow for a slightly larger cylinder for the same or lower price.

But, you can do whatever you want. You seem convinced you need to build a carnival ride. :confused3:

I've been in fabrication for 23 years, a Machinist for 5, all of my loads and leverages are calculated and accounted for. The question was about cylinder function, not design input. The design side was brought in as inquiries by other members. Your opinion is based upon assumptions, and while I thank you for taking interest in my posting, please reserve your judgement for someone else. As far as my research has shown, there has never been a design/ function like what I am trying to build, and am intentionally trying to be discreet with specifics. Additionally I stated that I need 17" of total stroke, not necessarily from the same cylinder, but in total to achieve the necessary arc at the given fulcrum and load points.

 

[bcp]

You appear to be doing what I often do, combined with what I should do.. I design what I want or need, they try to buy parts to build it or fit it, usually unsuccessfully. I need to find the most likely parts first, then design around them. The parts on hand to start with should be the most important part, or the most difficult to make.

It sounds like you are designing around a link you want to use, but maybe you should have found the cylinder most suited, then design around it, even if you have to make a link or change your design slightly. Hard to give more constructive ideas without knowing more.

I find lots of ideas in patents and don't mind copying them for personal use.

Google Patents

Search for anything related to your use, or anything that may have a use for a similar linkage. Just a quick glance at the drawing should lead to more investigation, or skipping past it. You may be designing a post-pulling crane, but find your answer in a lobster trap retriever.

Bruce

 

[Bigshooter81]

You appear to be doing what I often do, combined with what I should do.. I design what I want or need, they try to buy parts to build it or fit it, usually unsuccessfully. I need to find the most likely parts first, then design around them. The parts on hand to start with should be the most important part, or the most difficult to make.

It sounds like you are designing around a link you want to use, but maybe you should have found the cylinder most suited, then design around it, even if you have to make a link or change your design slightly. Hard to give more constructive ideas without knowing more.

I find lots of ideas in patents and don't mind copying them for personal use.

Google Patents

Search for anything related to your use, or anything that may have a use for a similar linkage. Just a quick glance at the drawing should lead to more investigation, or skipping past it. You may be designing a post-pulling crane, but find your answer in a lobster trap retriever.

Bruce

Excellent advice.

The design only has one constraint and that is space. It absolutely must be as compact as possible, while still meeting the minimum performance requirements.

 

[bcp]

Another thing about cylinders is the mounting and attaching. For example, a trunion-mounted cylinder with cross tube or an attachment hole in the rod end will be much shorter retracted than a same stroke cylinder with 2 clevis ends.

Bruce

 

[aircommuter]

Perhaps you could use a scissor linkage arrangement and have the cylinder pushing instead of pulling. Then a smaller cylinder would give you as much power as the bigger one. Plus that would allow you to be more selective on total motion in a limited space.

 

[BukitCase]

Good point; a 4" cylinder with 2" rod will have 1/3 more push than it has pull, at any given pressure...Steve