Pneumatic questions...

[Out of Sight]

Having to fiddle around the last 1 month with my Unimog (which also marks the first month of my life being with a Lego pneumatic system )..I'm thinking of creating a lifting crane with a telescopic boom, while also improving working and rotation range, therefore the pneumatic actuators will be subjected to serious leverage when the crane is fully extended.

Main objective : more powerful lifting capability on the main boom while maintaing the original design as much as possible, of the 8110's crane.

If I were to retain the stock 8110 setup, single pump, no air tanks running a single M motor...which of these options gives better lifting power?

1. Adding another pneumatic actuator on the main boom

2. Running two pumps at once (i don't know if a single M motor is able to do this)while still having a single actuators on the main boom.

There are maybe other options, you guys are welcomed to make suggestion. Thanks guys

[efferman]

a second pneumatic cylinder on the boom will double your lifting power and in addition with a second pump you will have the same speed when aou have a single cylinder.

with one pump it will work slower

Edited September 8, 2012 by efferman

[allanp]

Having to fiddle around the last 1 month with my Unimog (which also marks the first month of my life being with a Lego pneumatic system )..I'm thinking of creating a lifting crane with a telescopic boom, while also improving working and rotation range, therefore the pneumatic actuators will be subjected to serious leverage when the crane is fully extended.

Main objective : more powerful lifting capability on the main boom while maintaing the original design as much as possible, of the 8110's crane.

If I were to retain the stock 8110 setup, single pump, no air tanks running a single M motor...which of these options gives better lifting power?

1. Adding another pneumatic actuator on the main boom

2. Running two pumps at once (i don't know if a single M motor is able to do this)while still having a single actuators on the main boom.

There are maybe other options, you guys are welcomed to make suggestion. Thanks guys

Adding another actuator will help, it will be twice as powerful but twice as slow so you may want to use another pump as well. However, don't have them going in and out at the same time. Have them off set so that one is going in as the other is going out. That way the motor is only ever pumping one at any one time but you get twice as much volume.

Edited September 8, 2012 by allanp

[Out of Sight]

Thanks guys. I see...since I flunked physics class during my high school years..(well not flunked just not too bright), I understand that running double pneumatic actuators (let's call it 'PA')will increase the lifting capability but since the pump is running at constant speed/same debit of air , the PA will move twice as slow, although actually that's OK since I will need a slower more precise movement.

How about running two pumps at once using two M motors,on just a single PA? In theory I'll be pumping twice as much debit of air therefore increasing pressure hence better lifting capability? Although I'm worried that the movement will hideously fast and uncontrollable.

Edited September 8, 2012 by Out of Sight

[allanp]

Thanks guys. I see...since I flunked physics class during my high school years..(well not flunked just not too bright), I understand that running double pneumatic actuators (let's call it 'PA')will increase the lifting capability but since the pump is running at constant speed/same debit of air , the PA will move twice as slow, although actually that's OK since I will need a slower more precise movement.

How about running two pumps at once using two M motors,on just a single PA? In theory I'll be pumping twice as much debit of air therefore increasing pressure hence better lifting capability? Although I'm worried that the movement will hideously fast and uncontrollable.

Using two pumps will make it faster as the pressure will build up quicker but will not make the cylinders move with any more force. One pump will eventually get to about 60 psi or more which is when hoses start popping off. Two pumps will just get you there quicker. And like I said if you do want to use two pumps you don't need two motors. The pumps only pump air on the inwards stroke, not the outwards stroke, so by offsetting the pumps 180 degrees the motor will only be pumping one at any given time. I use up to 8 pumps in large MOCs, not to get anymore pressure but to get things moving quicker.

[SNIPE]

You can try experenting with different liftarms/ links where the cylender extends and retracts to create the hinge/pivot in the arm.

Gears and secondary liftarms can strenghen where the pivot is too.

What angle the cylender is at makes a difference too

Edited September 9, 2012 by SNIPE

[Out of Sight]

@allanp

Thanks for clearing this out. So I guess i'd better be off running one M motor using two actuators, but with the two pumps running at opposite 180 deg ofset so each 1/2 cycle pumps air as opposed to running just one pump (1 cycle 1 pump). In theory I should get the same movement speed with twice the strength when the pumps are pumping those two pneumatic actuators that I'll be installing later, is that correct?

EDIT : Allanp, is there a specific way to connect the air hose from the two pumps, or do i simply just add a T joints from the two hoses of the outlet from the pumps into one hose leading to the output switch?

@SNIPE

Yes I did experiment with the lift points.. to get better rotation range of the main boom, which the stock crane design lacks . But the range works like a gear ratio, since the pneumatic actuator travels at a fixed distance, therefore increasing rotational range ( moving the lift points closer to the pivot points of the boom) means greater leverage, therefore I need more force.

As you can see I have better rotational range of the boom compared to the original 8110 crane design, but I can barely lift anything heavier than 100 grams when the crane is fully extended.

The other reason is I plan to extend the main boom few studs longer so i can reach and drop the load on the logging trailer that I'd be moc-ing later on.

Edited September 10, 2012 by Out of Sight

[allanp]

@allanp

Thanks for clearing this out. So I guess i'd better be off running one M motor using two actuators, but with the two pumps running at opposite 180 deg ofset so each 1/2 cycle pumps air as opposed to running just one pump (1 cycle 1 pump). In theory I should get the same movement speed with twice the strength when the pumps are pumping those two pneumatic actuators that I'll be installing later, is that correct?

EDIT : Allanp, is there a specific way to connect the air hose from the two pumps, or do i simply just add a T joints from the two hoses of the outlet from the pumps into one hose leading to the output switch?

That is correct. It sounds like it should not be possible because you are getting twice the power without adding anymore motors or batteries. However it works because instead of having the motor under load 50% of the time, it will be under load 100% of the time, so it may drain the batteries quicker but batteries normally last a long time in pneumatic MOCs anyway. And yes, all you have to do is link the two outputs into one using a t-piece. One way valves inside the pumps prevents air from simply being moved from one pump to the other. Interestingly this does not work for LAs. Unless you are providing them with enough torque to activate the internal clutch, pairing two LAs onto one motor will not give you any more power, only less power due to increased friction from having more parts!

[Aris]

Nice topic.In my opinion, the best ways to increase your lifting power are:

1) To add a second mini pump(or more)

2) To add an air tank in order to have high pressure for heavy loads(in case you want slow movement don't lock the air switch!)

3) To add a second pneumatic cylinder(or more).