engine test stand with rollers

[mmagliaro]

I have the Bachrus rollers, and the conductivity is perfect.  I have always wondered how the heck they did that.

[narrowminded]

@RBrodzinsky and @haasmarc  Just curious as one of you has success and one some trouble, are the bearings that were used sealed?  Just shields?  Exposed cages?  SS?  I ask this because one possibility would be that the sealed bearings are greased, as you would like a bearing to be, but that's when you use it as a bearing, not a conductor.  I strongly suspect that for them to work well they should not be SS and should be run dry, which could only be accomplished by washing out the grease (or never putting any in).  Sealed would be tough but just shielded could probably be washed out and certainly open could be.  Maybe add a little Conductalube but no more.  I'd be curious to hear. 

Here's a link to Max's thread that Peteski was referencing for some gory detail on the ball bearing not conducting well.  I didn't chime in until page 3 but what you'll see is that we've been there and been confounded.   https://www.therailwire.net/forum/index.php?topic=37254.msg446907#msg446907

[metalworkertom]

Here are two photos of the ones that I have.  Does anybody know what brand they might be?  Once I figure that out I will know how to price them and will put them in the Trading Post.

Micromart sold them. Not sure of manufacturer. I only saw O scale with a quick look. I may be interested depending on what you want for them.

[RBrodzinsky]

Sealed. Here’s a front and back picture of them

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If one just touches the probes of a multimeter to the top of the roller and the side of the housing, there is no connectivity. If I push down on the roller, there is.

[metalworkertom]

I am willing to make these, very accurately constructed, if the interest is there.  They would be a little pricey (quick est. $40+/-?) as the bearings (shielded ball bearings) will have to be purchased but that's still not too bad for a very precise device.  Standard set would include eight bearing set blocks for four axles (sixteen bearings) and that could be increased in multiples of two blocks (one axle) as desired.  Even though there are a lot of six axle locos, a set under each end of each truck would probably be all that is needed, meaning four bearing sets should be sufficient for most diesels.  When purchased together each additional axle could be estimated at one quarter of the four axle set (est. $10 ea.). 

The bearing blocks would likely be machined from aluminum bar with the gauging blocks between them 3D printed and then critical dimensions on the prints finish machined as needed for excellent tolerance.  All parts would be very accurately made.  Gauge blocks for different gauges than N would be available finished and ready to use for Z and HO.  I guess other gauges could be furnished too although flange depths should be confirmed before to promise interchangeability. 

Any interest could be sent in a PM and if there's enough, I'll get on it.

.

I would be interested in some if you make them.

[haasmarc]

The Bachrus bearings appear to be sealed.

[peteski]

The more I think about it, the more I suspect that it is the lubricant that  kills the electric conductivity of ball bearings.  The more viscous the lubricant is, the more problem it will cause with conductivity.  A dry bearing would probably be the best conductor of electricity. And for what we use them for we could just run them dry. Or with some very light lubricant (like kerosene) woudl probably be ok to use.

[u18b]

I used micro bearings in some passenger cars, and they are the open kind and dry.

I have heard people in the past warn that bearings don't conduct very well- and maybe they don't.   But I have not seen a problem yet.

[crencs]

Saw this on Amazon
https://amazon.com/Yamix-Scale-Accessories-Treadmill-Bearing/dp/B07T39ZDZR/ref=sr_1_2?dchild=1&keywords=n+scale+test+track&qid=1610466893&sr=8-2 
Has anyone tried this out? Pricing is much lower than ones listed in this thread.

[narrowminded]

Saw this on Amazon
https://amazon.com/Yamix-Scale-Accessories-Treadmill-Bearing/dp/B07T39ZDZR/ref=sr_1_2?dchild=1&keywords=n+scale+test+track&qid=1610466893&sr=8-2 
Has anyone tried this out? Pricing is much lower than ones listed in this thread.

That one seems to have all of the conductivity points covered except for the SS part.  But, in this scenario it will probably work fine as it uses point contact of the axle to the through conductor rods on each side so has the opportunity to break through the nonconductive oxide (which is what makes SS, SS) with minimal effort.  Point contact has very high PSI loading even with very low applied force so has the chance to break through the oxide.  I'd be interested to see that one at work.

My biggest concern would be the execution of the part details but with all of the elements there, even if there were some quality issues it could probably be tweaked as needed to fix any troublesome fits.  Then there's the absence of support for trailing trucks and such but that too might be able to be rigged.  The cost is right back in the range of the quick estimate I put on one ($40) so that seems in line.  At least on paper, I think the better concept approach is this one.

[RBrodzinsky]

How is that supposed to work?  One rarely has access to the axles in a loco's trucks, or on a steamer's drivers.  Where do the wheels sit on this?  (I may just be dense this morning, so forgive me if this is obvious)

[narrowminded]

How is that supposed to work?  One rarely has access to the axles in a loco's trucks, or on a steamer's drivers.  Where do the wheels sit on this?  (I may just be dense this morning, so forgive me if this is obvious)

Power is fed through the two outer round bars.  The axles engage them at 90 degrees at that point making the electrical contact.  The loco wheels sit on the inside edge of the bronze/ brass wheels pressed on to the axles.  The inboard axle bearing supports the loco end of the axle and the other grooves should just be guides, allowing that end of the axle to bear on the outer, power supply rods.  The plastic block carries the features needed to set the gauge and hold it all together.  That's where I would be concerned about fits and finishes but have never seen one in person so don't have anything beyond concerns to offer.  I wouldn't mind seeing one in person.

I could make that style, too.  Preliminary budget estimate remains about the same as with ball bearings.

[RBrodzinsky]

Oh, now I get it! The brass wheels are at track width, and everything else is wider!  My mind was trying to envision the outer bars as “rails”, and I just couldn’t understand what I was seeing.

[narrowminded]

Oh, now I get it! The brass wheels are at track width, and everything else is wider!  My mind was trying to envision the outer bars as “rails”, and I just couldn’t understand what I was seeing.

Right!   It's also free standing, not sitting on the track.  You would supply power to the two outer rods with jumpers from your track or direct wired to your normal power arrangement.

[RBrodzinsky]

I followed the link on the page to their listing for just 6 of the bearing assemblies ($32) and it states

The positioning steel pin is made of bearing steel, which is harder and more wear-resistant.
304 solid stainless steel shaft, copper alloy oil bearing, make the front drive work more stable, the rotation is more delicate.

I think I will “bite” and place an order. Will be interested to see how well it works