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  #31  
Old 06-23-2012, 02:58 PM
johnny stick johnny stick is offline
 
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Default auto vs rv

My old plymouth and my old landcruiser both used tapered roller bearings. In both cases, the inner shaft was tapered so when the inside bearing's inner race was preloaded it would lock onto the inner shaft. To remove the inner race, I had to beat on it or heat it with the torch. The inner race for the outer bearing was kept from turning with a special washer that was keyed into a grove in the axle. The washer sat between the inner race and the nut. Based on these two designs the inner race of the tapered bearings were keep from rotating by the design of the spindle and keyed washer. JMO
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Last edited by johnny stick : 06-23-2012 at 11:09 PM.
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  #32  
Old 06-23-2012, 11:27 PM
WingsOnWheels WingsOnWheels is online now
 
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Quote:
Originally Posted by PerfTech View Post
... This is the way ALL RVs are made!!!!!!!!!!
Also several billion automobiles front wheels!!!!!!!!!
That is true for the RVs, there is nothing much keeping the inner race from spinning on the axle which is a lackluster design.

However, this is not true for the automobiles. For example, Most cars that use tapered wheel bearings eliminate the inner race and the bearing rides directly on the tapered spindle shaft. Those that do retain the inner race of the bearing have the race pressed onto the shaft or retained using a splined or keyed shaft and inner race.
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  #33  
Old 06-24-2012, 08:30 PM
Tim Lewis Tim Lewis is offline
 
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Default Axial load rating

I am intrigued by the idea of eliminating the need to repack bearings every year. However...

Wikipedia says "Tapered roller bearings are bearings that can take large axial forces (i.e., they are good thrust bearings) as well as being able to sustain large radial forces." If one were contemplating replacing field-proven tapered roller bearings (RV main wheel bearings) with ball bearings, I think one would want to see good data to support the notion that the replacement bearing can handle both the radial and axial forces.

For my RV-10, the main wheel bearing is an LM29749 in an LM29710 cup. According to page 147 of the relevant Timken catalog (http://catalog.timken.com/WebProject...Code=trb12flx#), the stock RV-10 bearings are listed with a dynamic rating of 2830 pounds of radial thrust and 1610 pounds of axial thrust.

As noted earlier, the Timken Ball Bearing Catalog (http://catalog.timken.com/WebProject...Code=tbb12flx#), page D57, lists the bearing used by Anti-splat (RA103RR2) as having a dynamic load rating of 4900 lb. Thats good. The catalog, however, lists no axial thrust rating.

Quote:
Originally Posted by PerfTech View Post
... When I submitted to Timken a detailed drawing of the aluminum wheels we use on our RVs they told me that the wheels under all axial and radial load conditions will fail long before the bearings.
Even if that statement regarding ultimate failure loads is true, how does one know what axial loads the RA103RR2 can routinely tolerate without excessive wear or damage? We don't seem to have the data to know whether the RA103RR2 is as capable as the LM29749 in ability to handle axial loads day in and day out.
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  #34  
Old 06-24-2012, 10:09 PM
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digidocs digidocs is offline
 
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Tim,

Correct me if I'm wrong, but I believe the RA103RR2 would be classified as a deep groove ball bearing. Unfortunately, I couldn't find any tech data on the Timken site about the axial capacity of their ball bearing assemblies. However, another well known manufacturer, SKF, has this to say:

If deep groove ball bearings are subjected to purely axial load, this axial load should generally not exceed the value of 0,5 C0. ... Excessive axial loads can lead to a considerable reduction in bearing service life.

(source)

Using the load rating (Co) from the catalog, 2500 lbs, these bearings are theoretically good to a side load of approximately 1250 lbs.

Now the million dollar question: Is 1250 lbs of side load capability enough? That's tough, but here's a stab at it:

Assumptions:
-Full gross weight, 1800lbs
-Single wheel carrying aircraft weight at 1G (one-wheel touchdown)
-Coefficient of friction between tire and surface 0.8 (FAR 23.479)

Ideally, the wheel tire would skid sideways before the bearing exceeds its axial load capability. Without a spacer between the bearings, the entire axial load is carried by a single bearing. The maximum axial load that the tire can generate is then 1800*.8 = 1440 lbs. Under these conditions, it appears the bearing is slightly overloaded.

Commentary:
There are of course several additional factors that should be taken into consideration. The radial touchdown load should be combined with the axial load in this scenario. This further increases the overall load on the bearing. On the other hand, the axial loads applied are likely to be of short duration. These short overload periods may reduce bearing life, but the overall bearing life may still be more than adequate. Adding a spacer between the two wheel bearings should approximately double the capacity.

In short, the analysis suggests that this new bearing, as installed, may or may not be up to the task. On to the real world testing!
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  #35  
Old 06-24-2012, 10:48 PM
johnny stick johnny stick is offline
 
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Default ball bearings in axial load

When I was working on F16s, we used ball bearings for axial loads too. These bearings had a dot on one side of the inner race, and a dot on the other side of the outer race to indicate load direction. If these ball bearings are truly meant for axial loads of any significant value, they should have a dot on the two races indicating assembly direction. In the pictures of the bearings, I do not see a dot on either race. I would be leery of using them for axial loads. Do we have any bearing experts out there who can weigh in?
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Last edited by johnny stick : 06-24-2012 at 10:50 PM.
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  #36  
Old 06-25-2012, 02:15 AM
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As I live in France and near to the Beringer factory which has recently moved to the Gap Tallard airfield I went to their recent Open House and bought one of their nose wheels for my RV6A. I must say I am very pleased with this product.
Coming back to the thread concerning the use of ball bearings with the main wheels, Beringer whose company specialize in producing aircraft wheels and break systems do a main wheel and break kit for RVs.
With their main wheel they also use ball bearings however they replace the standard RV axle with a tapered axle so as to clamp the inside bearing and hence make sure that both bearings support the axial load. If you look at the link below and scroll down to page 17 you can see this in detail

http://www.beringer.fr/cat/catPlaneEn.pdf

I have no connection to the Beringer Company however I must say their products seem to me to be top quality and if I were to build another RV I would go with the complete Beringer wheel and break system. It maybe a little more expensive than the Matco one which Vans provide as standard but to me it seems to be of much higher quality.

Barry RV6A F-PRVM

Last edited by Barry : 06-25-2012 at 05:19 AM.
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  #37  
Old 06-25-2012, 10:12 AM
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Quote:
Originally Posted by Barry View Post
As I live in France and near to the Beringer factory which has recently moved to the Gap Tallard airfield I went to their recent Open House and bought one of their nose wheels for my RV6A. I must say I am very pleased with this product.
Coming back to the thread concerning the use of ball bearings with the main wheels, Beringer whose company specialize in producing aircraft wheels and break systems do a main wheel and break kit for RVs.
With their main wheel they also use ball bearings however they replace the standard RV axle with a tapered axle so as to clamp the inside bearing and hence make sure that both bearings support the axial load. If you look at the link below and scroll down to page 17 you can see this in detail

http://www.beringer.fr/cat/catPlaneEn.pdf

I have no connection to the Beringer Company however I must say their products seem to me to be top quality and if I were to build another RV I would go with the complete Beringer wheel and break system. It maybe a little more expensive than the Matco one which Vans provide as standard but to me it seems to be of much higher quality.

Barry RV6A F-PRVM
....If you go to this link as suggested and take a look at the line drawing on page 17 you will see that the inner bearing is a slip or sliding fit on the axle with no taper where the inner bearing rides. This arrangement places 100% of the side loading on one bearing (the very small outside one) and none on the inner. This outside bearing is rated at less than half that of our bearings and is used by them all the way up to their 26"& 29" diameter bush set-ups. The aluminum axle they are selling for the 500x5 size category doesn't even begin to approach the strength of the 6000 series spring steel used on the Vans aircraft mains. Please don't think I am trying in any way to degrade, down-play or cut short Beringer or there products as they are some of the finest in the world. I am sure there engineering staff did their homework before designing their entire line of very expensive wheels, axles and bearings. It appears, perhaps we are over building and under pricing our service and parts? It just my be that we can get by with a much smaller, much cheaper bearing like they do. Allan....
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Last edited by PerfTech : 06-26-2012 at 09:51 AM.
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  #38  
Old 06-25-2012, 10:19 AM
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Mike S Mike S is offline
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Quote:
Originally Posted by PerfTech View Post
take a look at the line drawing on page 17 you will see that the inner bearing is a slip fit on the axle. This arrangement places 100% of the side loading on one bearing
I did notice that, and try as I might, I could not figure a way to import it here for folks to look at.
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  #39  
Old 06-25-2012, 10:44 AM
xavierm xavierm is offline
 
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Default Pic from page 17

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Last edited by xavierm : 06-25-2012 at 10:47 AM. Reason: edit pic link
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  #40  
Old 06-26-2012, 10:04 AM
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PerfTech PerfTech is offline
 
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Default Southern California RV-10

...If someone in Southern California is building an RV-10 I would like to see and measure the wheel and brake components. I will most likely be offering this set-up for the 10s as well and hate to go buy everything to evaluate the feasibility. Thanks, Allan...
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