[modeleng] Re: Needle roller bearings

Hi Ron,

I have fitted drawn cup needle roller bearings to all the axles of my 
2½" 4-8-4 Helen Long. The bearings run straight onto silver steel axles 
and the usual side play is allowed so the axle can float from side to 
side. I don't think you will have any wear problems - the axles and 
bearings will outlast the rest of the loco! Most of todays loco 
designers use this combination.

There was some discussion about needle roller bearings on another forum 
and some members seemed concerned about the life of plain silver steel 
axles. As a result of this I conducted an experiment using a 10mm bore 
bearing running on a silver steel axle as fitted to Helen. I connected 
the axle to a motor running at 1440rpm and hung a 16.5 pound weight on 
the bearing to simulate the load. This was the equivalent of a 2½" 0-6-0 
loco weighing 99 pounds - a much greater loading than in real life 
(Helen weighs about 45 pounds). The 'axle' was left running for a total 
of 230 hours which in Helen's case would have equaled a distance 
travelled of 3,400 miles! After this, there was no measureable wear on 
the axle at all, only a slightly matt finish to the bearing surface. You 
can see the experiment here:

http://www.baggo.copperstream.co.uk/me/locos/25inch/helen%20longish/helen19.htm.

I intend to fit needle rollers to my Simplex axles which are 3/4" 
diameter and will again be silver steel.

John

Ron Head wrote:
> Hi chaps
> Does anyone have experience of fitting needle roller bearings to locomotive 
> axles, that they would like to share?
>
> I want to fit drawn cup sealed needle roller bearings to a 5" gauge battery 
> driven diesel shunter.  Ideally, I'd like to fit hardened sleeves to the 
> axles, but there isn't space to do this.  However, the axles are of silver 
> steel.
>
> The loco has six wheels, and so the middle axle will need to have some side 
> play.  If the axle is allowed to float through the bearing, there will be 
> sliding instead of rolling contact between the rollers and the axle, and I 
> wonder if there might be a problem with wear on the axle?
>
> Would it be better to constrain the bearing on the axle in some way, and 
> allow the axlebox to move in the horns?
>
> Over to you guys!
>
> Regards
> Ron
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