Calculate hydraulic motor for a Flywheel

[Hans Heyde]

Gentlemen:

I got stuck in this problem and I really need your help:

I have an hydraulic line of 23Mpa ( 3.300 psi) 10 gallon/min

I built a flywheel weight 58,000 grams with the following Inertial properties Principal moments I1= 2.5 , and I2= 2.3 and I3= 632170437 grams mm3

Flywheel will turn around I1.

I have V belts connecting the flywheel to an Hydraulic motor:

Flywheel have a nice shaft with taper bearings and it is well dynamically balanced. The pulleys. between Hydraulic Motor and flywheel are not fabricated yet, waiting for your answers and can be built in any diameter.

I would like to make this flywheel spin at maximum rpm, regardless of torque received by flywheel.

Question: what are the necessary data that I will need to order the hydraulic motor?

Best regards and thanks for your time.

Hans

 

[anorlunda]

1. When a flywheel exceeds its maximum speed, it breaks up into pieces. What that speed is depends on the material the flywheel is made of.
2. The power needed to turn a fly wheel is determined (a) by how fast you must accelerate it, (b) the power needed to overcome friction in bearings and the air surrounding the flywheel. If you neglect acceleration and friction, then zero power is needed (no motor needed to allow the flywheel to keep spinning at constant speed, just like no motor is needed to keep Earth spinning once revolution per day.). So in real life, you must specify the acceleration and the friction forces. Friction is very hard to estimate, you probably need to build the flywheel and run experiments to measure friction.

 

[Dr.D]

If you really want maximum speed for the flywheel, you probably should first determine what that maximum speed is. As anorlunda indicates, the true maximum speed is just short of that which causes the flywheel to disintegrate. If that is known, then I suggest that you back off from that speed by a healthy margin of safety and set that as your design goal.

Then again as anorlunda has said, you must determine the bearing losses and friction. These will govern the power required to run at design speed. V-belts may not be the best way to transmit power if the speed is extremely high as they too are subject to strength limitations.

 

[Hans Heyde]

Hi

1. When a flywheel exceeds its maximum speed, it breaks up into pieces. What that speed is depends on the material the flywheel is made of.
2. The power needed to turn a fly wheel is determined (a) by how fast you must accelerate it, (b) the power needed to overcome friction in bearings and the air surrounding the flywheel. If you neglect acceleration and friction, then zero power is needed (no motor needed to allow the flywheel to keep spinning at constant speed, just like no motor is needed to keep Earth spinning once revolution per day.). So in real life, you must specify the acceleration and the friction forces. Friction is very hard to estimate, you probably need to build the flywheel and run experiments to measure friction.

Hi Anorlunda.

Thanks for your reply.

Flywheel is made of Steel plates welded together.

I will have a brake system to avoid spinning too high and breakup in pieces.

Also, my flywheel shape has many open plates that will find air resistance and reduce speed.

Bearings are very good and friction is very low.

What I will need is to achieve maximum speed in the shortest time.

Then I will stop it with a brake system they will impose a torque against the free

I have to spin it with an hydraulic motor, that will also stops de rotation when the oil flow stops.

My problem is, therefore, find out what will be the characteristics of this motor that will spin it very fast at a maximum rotation. Note that we can supply oil at maximum 3300psi and 10 gal/min, and I will like to use the full power of it.

Best regards Hans

 

[anorlunda]

We can't answer your question without numbers.

What is max speed? How fast must you accelerate?

It would take infinite power to accelerate in zero time, so you have to choose the time and then we can calculate the power.

The dimensions of the spinning disk are also needed. We need to know the moment of inertia.

The numbers for air resistance and bearing friction are also needed, not just words high or low.

The more specific you can be with your question, the better the quality of the answer.

Did you read what @Dr.D said about belts?

What are your plans for safety? If a flywheel breaks, it could kill everyone standing nearby.

Think also about vibration. If everything is not carefully balanced, vibrations can destroy everything. Do you know how to balance spinning things?

 

[russ_watters]

What is the purpose of this machine? Can you draw us a diagram?

 

[Hans Heyde]

Hi Russ & Anorlunda
My machine is to cut tree branches.
See attached photo.
The hydraulic motor is not shown.
The fly wheel has steel blades attached to a turning "steel cave".
This structure is turning by an hydraulic motor and pulleys and belts.
The hydraulic motor maximum speed is 750 rpm, torque is 19.5 Nm power is 12.5 W.
My idea is to have pulleys that will turn the "Flywheel" at around 2.000 rpm.
I already tested this speed on the real flywheel and there is no vibration ( it is well balanced).
My idea is to make the flywheel turn up to maximum speed of the gear motor, and the to feed it the tree branches that will cut them in little pieces (chips).
Each revolution will cut a small part ( chip) of the tree branch, and will reduce it speed.
If the branch is too strong ( stronger wood or bigger diameter) the flywheel will reduce the speed.
When the "machine operator" finds that the speed is too slow, he will deduce the velocity that he is feeding the branch .
Outside diameter of the flywheel is 300 mm and its weight is 58 kilos ( 580 N).
Well, I believe it may work: what do you think?
Thanks a lot for all your help.
Hans

 

[Dr.D]

Commercial wood chippers are on the market. you might want to look at one of them.

 

[Hans Heyde]

Hi Dr D
Yes, I already checked those, but they do not match what I need.
This is a unique application...a new one...similar but not equal to the existing models.
I decided to make my own to match what i Need
Thanks a lot for your information.
Regards
Hans

 

[JRMichler]

When building a machine that has the same function as commercially available machines, it is good practice to take a look at similar machines, then design around their weaknesses. A commercially available chipper with about the same power as your 12.5 Kw hydraulic motor is: https://www.drpower.com/power-equipment/chippers/wood-chippers/self-feeding-wood-chipper-16-5.axd. If the chipping head has enough inertia, it can be direct driven by the engine.

Larger chippers automatically vary the feed rate to get maximum chipping speed. One of these will chip an entire tree in a few seconds: http://www.morbark.com/equipment/3036-whole-tree-chipper/#1365620863249-5-4.

MTA: Dr D beat me to it... In what way is your design better than the commercially available chippers?

 

[anorlunda]

I'm still seriously concerned with safety. As those blades hit the wood, they will enentually break sending sharp,pieces of metal flying. Suppose there is a nail in the wood you're cutting. Then the remaining wheel will be seriously unbalanced. It might throw off more blades. Your machine needs heavy duty shielding to contain any flying bits.The slower the RPM, the safer. Why do you think you need such high speeds?

Here is a wood chipper that sounds close to,your description. Rotating disc 434 kg, 4 knives, 250 hp engine, no data on RPM.

http://www.scanwood.co.za/downloads/TP_320_Data_Sheet.pdf

 

[berkeman]

Thread closed temporarily for Moderation...

 

[berkeman]

Hi Russ & Anorlunda
My machine is to cut tree branches.
See attached photo.
The hydraulic motor is not shown.
The fly wheel has steel blades attached to a turning "steel cave".
This structure is turning by an hydraulic motor and pulleys and belts.
The hydraulic motor maximum speed is 750 rpm, torque is 19.5 Nm power is 12.5 W.
My idea is to have pulleys that will turn the "Flywheel" at around 2.000 rpm.
I already tested this speed on the real flywheel and there is no vibration ( it is well balanced).
My idea is to make the flywheel turn up to maximum speed of the gear motor, and the to feed it the tree branches that will cut them in little pieces (chips).
Each revolution will cut a small part ( chip) of the tree branch, and will reduce it speed.
If the branch is too strong ( stronger wood or bigger diameter) the flywheel will reduce the speed.
When the "machine operator" finds that the speed is too slow, he will deduce the velocity that he is feeding the branch .
Outside diameter of the flywheel is 300 mm and its weight is 58 kilos ( 580 N).
Well, I believe it may work: what do you think?
Thanks a lot for all your help.
Hans

@Hans Heyde -- What you are working on is potentially pretty dangerous, especfially with your limited background and experience. Basically if you need to ask for design help on an Internet forum, you probably shouldn't be undertaking the dangerous project.

So this thread will remain locked, and I have a couple quick pieces of advice for you. First, on projects like this, it is best to find or hire an experienced professional who has the skills to help you design the project with all applicable safety measures. Second, please look into the liability insurance ramifications of building and fielding such a project. Even it it is for private use, you are opening yourself up to lawsuits by anyone injured by the device, and if you plan to use it professionally or sell it, that opens up a much larger liability world (please consult a liability lawyer for that). Please stay safe.