Looking for suitable ball bearings

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Discussion Overview

The discussion revolves around the design and performance of a water turbine prototype, specifically focusing on the challenges faced when integrating ball bearings with the turbine. Participants explore the effects of bearings on turbine RPM and seek suitable bearing options for the design.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant describes a water turbine prototype that performs well without bearings but experiences a significant reduction in RPM when bearings are added.
  • Another participant notes that small turbines typically have limited energy output, questioning the necessity of ball bearings for such designs.
  • Several participants suggest different types of bearings (open, shielded, sealed) and provide specific part numbers for bearings suitable for a 15 mm shaft.
  • There is a suggestion to use a thin wire shaft instead of a larger diameter shaft to reduce friction and improve performance.
  • Some participants express skepticism about the practicality of using ball bearings given the low power output of the turbine.
  • One participant mentions the potential for using a Windmill Spinner design, questioning its compatibility with the turbine.
  • Another participant raises the idea of measuring the turbine's RPM and power output before attaching it to a generator.
  • Concerns are raised about airflow blockage when attempting to extract energy from the turbine, which could stall its operation.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the necessity or suitability of ball bearings for the turbine. There are multiple competing views regarding the design considerations and the effectiveness of various bearing types.

Contextual Notes

Some participants highlight limitations in the available data, such as the absence of dimensional drawings or videos that could clarify the turbine's design and performance. There is also uncertainty regarding the actual RPM measurements and the implications of using different bearing types.

Who May Find This Useful

This discussion may be useful for individuals interested in turbine design, bearing selection, and experimental setups in fluid dynamics or renewable energy applications.

T C
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TL;DR
I am looking for suitable ball bearings for my waters turbine because I have found that without the bearing the turbine rotates well but when a shaft is attached and bearings are fitted, the RPM reduces drastically.
I made a waters turbine CAD design and make prototype with a 3D printer. I first tested the turbine by putting it at the tip of a ball point pen. At the tip of the ball point pen, the turbine rotates well. I made a video but there is no option by which I can upload the video. Later I attached a shaft and bearing but found that the RPM reduced drastically in the same condition when when the shaft and bearing is attached. Can't understand the reason.
 
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There is not much energy available from small turbines.
Post a diagram or picture of your turbine, or a link to a similar one.
We need to know the size of the bearings you require.

Sealed ball bearings have higher friction in the lip-seals.
There are ceramic ball bearings available for wet situations.
Search eBay for examples. 'ceramic ball bearing'.
 
1730031329532.jpeg

This is the turbine. Everything will be clear if I will be able to upload the videos, but there is no way I was able to upload those. It's basically a Waters turbine.
 
T C said:
Everything will be clear if I will be able to upload the videos, but there is no way I was able to upload those.
We do NOT need videos, we need dimensional data and a diagram of the mounting shaft(s).
What is the outer diameter of the turbine?
 
The diameter of the turbine is 25 cm and the shaft diameter is 15 mm. Kindly note that when the turbine is put at the tip of a ball point pen and set before a ceiling fan, it rotates well. But the RPM drastically reduced when the shaft and bearings are attached.
Here is the first video. Here you can clearly see how well it's rotating without the shaft and bearing while being put under a simple ceiling fan. But you can see how drastically the RPM is reduced in this video when the shaft and bearing is being attached. Now it's time to find out a suitable bearing for such a device.
 
Last edited:
T C said:
The diameter of the turbine is 25 cm and the shaft diameter is 15 mm.
Ball bearings are available as open, shielded, or sealed. The open and shielded have the lowest friction, while sealed have the highest friction. Part numbers for a typical ball bearing for a 15 mm shaft are:

Open: 6302
Shielded: 6002-2Z
Sealed: 6002-2RS

Mounted ball bearings are also available. These have sealed ball bearings inside a housing, where the housing has bolt holes for mounting. The sealed ball bearings used in mounted bearings have higher seal friction than plain sealed ball bearings.

A good source for general information on available types of bearings is McMaster-Carr: https://www.mcmaster.com/products/bearings/. Major manufacturers of ball bearings include SKF and NTN. They have bearing catalogs online that include information on friction for different types of ball bearings.
 
Which kind of bearings can be most suitable for such a machine? kindly suggest.
 
I am trying to guess what kind of bearings were used in the Tesla Turbine shown in the video. Apparently it seems that the weight of this Tesla turbine and my turbine is almost the same.
 
T C said:
Here is the first video.
But you can see how drastically the RPM is reduced in this video when the shaft and bearing...
Those links are not working for me.
As requested above, could you post all or part of the waters turbine CAD design you have used to make prototype with a 3D printer?
 
  • #10
T C said:
Which kind of bearings can be most suitable for such a machine? kindly suggest.
Will it be used in water or in air?
 
  • #11
Baluncore said:
Will it be used in water or in air?
In air.
 
  • #12
Lnewqban said:
Those links are not working for me.
As requested above, could you post all or part of the waters turbine CAD design you have used to make prototype with a 3D printer?
Kindly inbox me.
 
  • #13
T C said:
The diameter of the turbine is 25 cm and the shaft diameter is 15 mm.
The power available from such a small wind turbine is insufficient to justify a ball bearing.
 
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  • #14
Baluncore said:
The power available from such a small wind turbine is insufficient to justify a ball bearing
In that case what are you suggesting?
 
  • #15
T C said:
In that case what are you suggesting?
That you spin it on the tip of a ballpoint pen, or on a thin steel wire shaft, less than 1 mm in diameter.
Search eBay for; Windmill Spinner .
 
  • #16
Baluncore said:
Search eBay for; Windmill Spinner .
Do you think a Windmill Spinner can hold this turbine?
 
  • #17
T C said:
Do you think a Windmill Spinner can hold this turbine?
Yes.
Any attempt to take energy from the airflow, will block the airflow through the turbine, the air will go around the outside, so the turbine will stall.

The cost of buying and installing a ball bearing will exceed the total power generated over the life of the system.
 
  • #18
Baluncore said:
Any attempt to take energy from the airflow, will block the airflow through the turbine, the air will go around the outside, so the turbine will stall.
For now, I don't want to engage in a debate in this regards. As I have told before that the turbine was rotating well when placed at the tip of a ball point pen. But RPM reduced drastically when ball bearings are attached. I just want to find the suitable ball bearing or any other means that will help to rotate the ball bearing freely.
 
  • #19
The shaft diameter is too big, so balls travel too fast and too far.
You need to reduce the shaft down to a couple of millimetres at most.
https://www.ebay.com.au/itm/135243236381?
If they have thick oil, wash the oil out of the bearings with diesel or a lighter oil.
 
  • #20
T C said:
the Tesla Turbine shown in the video.
I get a YouTube video of a son gifting a car to his dad...
 
  • #21
Baluncore said:
Windmill Spinner
What kind of bearing do those simple Windmill Spinners use? Just a thin wire shaft in wood or plastic maybe?
 
  • #22
berkeman said:
Just a thin wire shaft in wood or plastic maybe?
Yes.
Take a look at the way Mattel Hot Wheels took on the Matchbox scale model cars by lowering the axle friction. Mattel disrupted the industry, beat, and then purchased the Matchbox holding company, Tyco Toys.
First, Mattel replaced the wheels with a wider, hard plastic material, so the wheel rotated freely on the fixed axle. Second, they replaced the thicker metal rod axles with an 0.8 mm spring wire. Finally, Hot Wheels nickel plated the axles.
https://en.wikipedia.org/wiki/Hot_Wheels#History
 
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  • #23
Wait, aren't you going to attach this to a motor/generator to genereate and measure power output? You can mount the turbine directly to the generator shaft.
 
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  • #24
russ_watters said:
Wait, aren't you going to attach this to a motor/generator to generate and measure power output? You can mount the turbine directly to the generator shaft.
I first want to measure the RPM and guess the possible output from it. After that, I will attach it to a generator to measure the output. By the way, if anybody want to test it at his/her own, then I am ready to share the CAD drawing with him/her.
 
  • #26
The flow velocity from a common ceiling fan is around 2.5 m/s. You can check from the first video that even at this velocity, the turbine is rotating well without the shaft and bearings. At least this shows that the power output will be sufficient at higher velocity. Though I haven't measured it, but I can guess that the RPM of the turbine without the bearings is around 200 and the diameter is 25 cm.
 
  • #27
T C said:
The flow velocity from a common ceiling fan is around 2.5 m/s. You can check from the first video that even at this velocity, the turbine is rotating well without the shaft and bearings.
The videos don't work for me either.
T C said:
Though I haven't measured it, but I can guess that the RPM of the turbine without the bearings is around 200 and the diameter is 25 cm.
Do you have the ability to measure the RPM? Searching the google app store, I see they have a stroboscope app for android phones...
T C said:
At least this shows that the power output will be sufficient at higher velocity.
Sufficient for what? Anyway, I think your next step here is to select a suitable DC motor to act as your generator, and set up the electrical test circuit. Do you have an idea of what you think the power output will be, to select the motor?

You will also need and anemometer to measure wind speed.
 
  • #28
russ_watters said:
Do you have the ability to measure the RPM? Searching the google app store, I see they have a stroboscope app for android phones...
A simple market available tachometer will be enough.
russ_watters said:
You will also need and anemometer to measure wind speed.
I have guessed it because I have tested the flow velocity from a ceiling fan with an anemometer not so long ago.
 

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