Bearing damage

[bsmtboy2]

Switch to Swiss WIB bearings and you will be very happy as previously stated......bearings in plastic inside a motor at 400 degrees is a recipe for disaster.

 

[dwilfong]

Well when I ran the VAC .91 with the RS 1.01 piston and sleeve in it The bearings failed quick. Like the first day testing.
Spent many hours on the phone with Greg Settle talking about this problem.
SO had bearings made with full complement ceramic balls and thy lasted for ever.
Go here and have some made with .001 radial clearance noted in the comment section of the order page.
https://www.ortechceramics.com/prod...earings/6002-hybrid-ceramic-bearings-15x32x9/
Not bad at $40.25 then again you can get spendy and get the ABEC 7 for $12.25 extra..........................

 

[Timbo Whalen]

Most of the large bearings in our nitro motors are a C3 fit, ABEC 5. ABEC rating does not necessarily translate into a better bearing. A very high quality WIB bearing with an ABEC 3 rating will likely perform better than a low quality ABEC 9 bearing.

The key here is to pick a high quality bearing. WIB, NMB, SKF, GRW, INA all produce good bearings, but you have to be willing to dive into the exact quality of these bearings to find the good combinations.

Thinkin' the fit is the big issue....ABEC-7, 9 is a waste of money and might possibly not be as durable considering nitric acid residue from burning nitro. Food for thought.

 

[Timbo Whalen]

Most of the large bearings in our nitro motors are a C3 fit, ABEC 5. ABEC rating does not necessarily translate into a better bearing. A very high quality WIB bearing with an ABEC 3 rating will likely perform better than a low quality ABEC 9 bearing.

The key here is to pick a high quality bearing. WIB, NMB, SKF, GRW, INA all produce good bearings, but you have to be willing to dive into the exact quality of these bearings to find the good combinations.

Also, it seems Joe Warren found a good bearing for this application sourced from some company out of Turkey.....maybe he'll chime in.

 

[Terry Keeley]

Thinkin' the fit is the big issue....ABEC-7, 9 is a waste of money and might possibly not be as durable considering nitric acid residue from burning nitro. Food for thought.

Here's the problem, a precision balanced spindle it aint!

 

[dwilfong]

ABEC ratings just mean thy spend more time to make sure the dimensional clearances are with in a closer tolerance.
When you have them custom built you can specify what radial clearance you want.
The radial clearance is what keep the bearing alive in are small high RPM engines.
This compensates for any heat expansion that is the reason for the bearing getting TIGHT and failing.
Greg spent many hours trying different clearance set ups and found that between .0008 and .0012 clearance is best.
With ceramic balls thy do not swell up when heated so this takes one veritable out of the equation.
Full complement increases the load carrying ability of the under sized bearing like that in the VAC .91 engine.
Remember the small RC turbines spin at over 100,000RPM and use full complement bearings.
Had this talk with Jim Allen also and a light went off when I told him this.
This is not conjecture but real life proven facts.
So take it for what it is and keep spinning them up.

 

[tnrcboatracer]

Also the mass of the balls is less for the acceeration and microwelding of the balls to race are eliminated with ceramic balls. Comparing a 100k turbine application to a single piston engine is apples to oranges.

 

[dwilfong]

Also the mass of the balls is less for the acceeration and microwelding of the balls to race are eliminated with ceramic balls. Comparing a 100k turbine application to a single piston engine is apples to oranges.

Yes the lighter ball react much different no need for a cage to keep them separated.

 

[Tom Foley]

Interesting information. It seems there are several views regarding the application of ceramic bearings in our engines . I have only had one experience with them and that was in a NR DD46 . The bearing had a reasonable life but did degrade . I am going to continue using conventional bearings of the two major brands mentioned. Keep all the information coming it's very interesting.

 

[tnrcboatracer]

I would not recommend the full complement with steel balls in our application due to the surface contact speeds causing the balls to microweld at the skid contact point.

I'm trying to find the thread where the variation in angular velocity was discussed. I want to say it was on the order of 20% variation (5000rpm) from compression stroke to power stroke. Heavier brass flywheels help reduce this at the expense of throttle response.

 

[LohringMiller]

I wrote a series of articles on nitro engine design and construction. Attached is the last in the series on construction methods. The articles depend heavily on information Jim Allen and Frits Overmars shared with me over the years. I doubt that machinists exist in the US with the skill and interest to replace Jim and his predecessors. Fortunately, Al Hobbs has contacts in Europe that are still capable of producing these high quality engines.

 

[RaceMechaniX]

Small RC turbines as well as the car turbo's which have cartridge style ball bearings use pre-loaded angular contact bearings with ceramic balls. Big difference to those versus deep groove BB's which most of use run in engines. Although the RC turbines use full complement, all the automotive and commercial vehicle turbo's use cages however they are a special design and often silver plated or nitro carburized. The reason they do not run full complement is the friction between the balls can be high and the relative velocity of the ball to ball contact is 2x what the ball to cage is.

BTW, the smallest cartridge ball bearings used in passenger turbo's spin to 230kRPM and have to live about 10k hours over some nasty conditions. Needless to say a lot of R&D has gone into those bearings.

 

[JoachimRuess]

I wrote a series of articles on nitro engine design and construction. Attached is the last in the series on construction methods. The articles depend heavily on information Jim Allen and Frits Overmars shared with me over the years. I doubt that machinists exist in the US with the skill and interest to replace Jim and his predecessors. Fortunately, Al Hobbs has contacts in Europe that are still capable of producing these high quality engines.

Hi Lohring,
your article about nitro engines is the most interesting thing i have ever read.
Is there any opportunity to see the whole series of your articles?
I will be very interested.
Thank you very much
Joachim

 

[LohringMiller]

Thanks. Someday NAMBA promises to have all my technical articles on the website. Here are the rest of the articles:

 

[LohringMiller]

Part 2

 

[LohringMiller]

Part 3

 

[LohringMiller]

Part 4

 

[LohringMiller]

Part 5

 

[Barrie Lever]

Thanks. Someday NAMBA promises to have all my technical articles on the website. Here are the rest of the articles:

Hello Lohring

I think that parts 1 to 3 are the same document.

Very interesting reading.

Thanks

 

[LohringMiller]

Sorry, I fixed the files.
Lohring Miller