Help with gear design 2

[nambass]

Hi everyone
I need help!

I am trying to build a gearbox for an electric motor. The motor must turn a waterpump.
I want to keep the motor as small as possible (Lowest KW motor as possible), but at the same time get more than enough torque to turn the pump without overworking the pump and to provide enough power to start the pump.

Most electric motors I have looked at is running at 2800rpm (AC 230v motors) or even 12v DC motor will also work
I need a run at 200rpm and have at least 430nm torque.

I was looking at drive train, pulley or planetary gears. I having access to a machine shop with waterjet cutters etc. So creating gears should be doable.

Please, I need someone that can help me solve this - I do not want this for free, but will appreciate any help!

 

[MikeHalloran]

Waterjet cutters cannot produce decent gears in the size you need. Furthermore, building your own gearbox is insane when you can buy mass produced and well engineered gearmotors for just about any application.
... but don't buy one just yet.

Please explain why your particular pump must be driven at a mere 200 rpm.





Mike Halloran
Pembroke Pines, FL, USA

 

[nambass]

Well is actually a long story, is a self modified pump, so now I have calculated the best optimal speed is the 200rpm.
I was looking at some companies manufacturing reducer gearboxes, but do not know if that would be the best. But looking at your comment, is something I need to consider. Never the less, it will still be good to know how to calculate this with excel. That way if I do have a different need, then I can apply the same formula.

 

[MikeHalloran]

There isn't _A_ formula for designing gears.

Use stock gears and/or v-belts. Be aware that the motor you buy will need bearings rated for radial loads (belt pull or gear separation force). ... or buy a planetary gearbox.

In the meantime, do tell us the long story about the pump.
Do include pictures, please.


Mike Halloran
Pembroke Pines, FL, USA

 

[gearcutter]

As MikeHalloran has suggested; we need a great deal more info than the little that you have already given.
If you want our help; you need to help us understand exactly what it is that you're trying to achieve.
If you can't provide that info; then do as MikeHalloran has suggested and look into an 'off the shelf' solution.
Alternatively; purchase the latest gear rating standards from the AGMA's website and design your own gears. There are programs that you can purchase that can do most of the work for you. A simple Google search will put you on the right track.

If, as you say, you're prepared to pay for someone's help; hire a gear design consultant. The AGMA's website lists several.

There are alternatives to AC motor stock RPMs........2800 isn't the only speed that can be purchased.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[nambass]

Hi Guys

What I have done was to use a centrifugal pump in a borehole and attached a same old push rod system used by a windmill. The push rod I attached onto a wheel to work same as the steam engine. I am not at the farm at the moment and will not be able to show some pictures now. It was just a proof of concept I build but now want to change the motor. I used up to now a petrol engine with a pulley to turn the bigger wheel. What I now am thing of doing is to change the petrol engine to a electric motor with a solar system and backup battery. On the 10k water tank I have a ball valve that I want to wire to engage the pump. This I still need to get working but it is the basic concept of what I am trying to achieve. The main reason why I want to do this is because I am not at the farm always I want to have a automatic system. The farm is small, about 200hectar and only started now with some sheep, goats and will soon start veggies.

 

[drawoh]

nambass,

The only way to minimize the power of your motor is to select an efficient speed reducer, and make sure your pump is running at peak efficiency. Single stage spur gears, chain drives and belt drives are pretty good. Watch out for worm gears. High ratio ones are very inefficient.

You can minimize the size of your motor by running a low torque, high speed motor, but you need to worry about your drive train, as noted above. For a given pump, flow rate and pressure, your power is constant. Darn those laws of physics, anyway!

--
JHG

 

[3DDave]

2800 to 200 is 14:1, which is a pretty good jump. This is better handled as two stages of roughly 4:1. Chain drive is pretty easy for this, though toothed belt could be more corrosion resistant.

Check

http://www.bikeradar.com/us/road/news/article/chain-or-belt-drive-which-is-faster-36074/

Also, check the math on this:
430n-m*200Rev/Minute*(2*pi/Rev)*(1 Minute/60 seconds)
= 9005.89894029074061692624 n-m/second = 9kW.

That's a pretty big pump. 750 Amps at 12V; Are you sure about that torque figure and the size of the farm?

 

[nambass]

Thanks 3DDave
Does this mean I need to have a 9kw electric motor to generate enough torgue, even when using a two stage chain to drive belt system? MMM is that is the case then I am screwed as that will not work. I was hoping of using a smaller electric motor even a 3 or 4 stage can help, but since I need or want to get the motor running from a single car battery as backup power and a small solar panel to provide charge to the battery, I need to keep the motor as small as possible. Also to try and keep cost down.

The farm is small, is 187hectar.

 

[3DDave]

It depends. First, did I get the math right? I'm pretty sure I did, but there should be another check on it. Second, did you get the values right for the torque and speed requirements.

I mention the farm size as that seems to be a lot of power, suggesting a pretty large farm.

How much water / how fast and how high are you pumping it?

 

[tbuelna]

nambass-

The 9kW number noted by 3DDave may not include the mechanical losses in the drivetrain between the electric motor and pump. A commercial 14:1 reduction gearbox would produce at least a 3-4% loss by itself. Your electric motor and controls must also be sized for starting loads, which will be much higher than operating loads.

I'm also a bit curious as to your centrifugal water pump that operates at 200 rpm. Can you provide some details about the pump design? And could you also provide more specific details of your pump installation and drivetrain configuration?

Regards,
Terry