Looking for help designing a truck axle pocket wear test fixture

[learmoia]

While your latest idea is viable, why put all that wear and tear on a drill press when the same thing can be accomplished with a small hobby motor and some rubber bands?

Most of my modeling stuff is still packed from the move.. The drill press would be an easy setup.. I just want to see if the idea would work.. Not going to run it for more than 5 minutes....

~Ian

[Lemosteam]

While your latest idea is viable, why put all that wear and tear on a drill press when the same thing can be accomplished with a small hobby motor and some rubber bands?

Least of my worries for a 1/2hp drill press.  Now electrical use on the other hand....

[peteski]

Most of my modeling stuff is still packed from the move.. The drill press would be an easy setup.. I just want to see if the idea would work.. Not going to run it for more than 5 minutes....

~Ian

But John is using this setup for a wear test - he will be running for for days, weeks, or months.   Assuming that he runs it at a realistic N scale speed (not at 10,000 RPMs!  He doesn't want to melt the axle pockets - just wear them out.   

[Lemosteam]

Yes. Yes I do.

[learmoia]

But John is using this setup for a wear test - he will be running for for days, weeks, or months.   Assuming that he runs it at a realistic N scale speed (not at 10,000 RPMs!  He doesn't want to melt the axle pockets - just wear them out.   

Well I was shooting for a couple thousand RPMs... and run for a couple hours (if things hold together..)

[peteski]

Well I was shooting for a couple thousand RPMs... and run for a couple hours (if things hold together..)

I think the test will take much longer to even show any appreciable wear. And again, if the wheels spin unrealistically fast then I don't think the test will be accurate or valid.

I remember Victor Miranda's locomotive tests - he ran them for hundreds of hours (240 hours is just 10 days).  I think that the the loads and the bearing surfaces we are dealing with here will take much longer than few hundred hours to show wear.  But again, under realistically replicated load and speed.

[Lemosteam]

My drill press can get down to the hundreds of rpm.

[peteski]

My drill press can get down to the hundreds of rpm.

From me, the noise of a large drill press running constantly for several days would annoy me.  But a sound of an N scale motor running fairly slowly would not.

[Lemosteam]

From me, thes noise of a large drill press running constantly for several days would annoy me.  But a sound of an N scale motor running fairly slowly would not.

I'll record the audio and send you the video. 

[peteski]

I'll record the audio and send you the video. 

You are an *EVIL* man John LeMerise!

 

[learmoia]

IT'S ALIVE!!!!!

I took a Life like 50' underframe - cut it in half.  Scraps of 1x2s and screwed the underframe halves to the end.  drilled a hole in the center of the 1x2 and run a screw through with a washer to mount it to the drill base (this allows me to easily adjust the block towards / away from the spindle to factor in the size and tension of the rubber band.  I used a nail for the spindle drive.

I think the truck is MDC truck.. maybe Atlas..

In the video it's running at 200 RPM at the spindle.. I adjusted the pulleys up to 860RPMs with no issues (see next video)
The drill press is a 2 belt drive and 860RPM was as high as I could go without flipping belts. 


200RPM

860RPM

Here are the dims involved.
Diameter of the spindle shaft .090
Diameter of the wheel axle near the rubber band is .055 but it tapers a bit to the center.
Diameter of the wheel at the flange .206 and of course that tapers a bit too.


*EDIT... MUCH BETTER..
Spindle at .969" to .055

~Ian...

[learmoia]

So check my math..

The Spindle is set to 860RPM
The diameter at the spindle is .969"
The diameter at the wheel axle is .055 - so RPM of the axle is 15151.64RPM?

Then Translate that to the wheel.
.055 at 15151.64RPM
to .206 = 4045.34RPM of the wheel.
Now I want to convert from N scale to 1:1.. so we're going to say the 4045.34RPM is turning a 32" wheel
So a 32" Dim wheel at 4045.34RPM give you 2,093,903.60 feet/hour
I assume take that /5280 gives MPH = 396.57mph?

.. So I'm running the assembly at about 400 Smph..   

~Ian

[peteski]

.. So I'm running the assembly at about 400 Smph..   

~Ian

Very cute, but that is exactly why I said earlier that to me that would not be a valid test setup.

But John is using this setup for a wear test - he will be running for for days, weeks, or months.   Assuming that he runs it at a realistic N scale speed (not at 10,000 RPMs!  He doesn't want to melt the axle pockets - just wear them out.

[learmoia]

Very cute, but that is exactly why I said earlier that to me that would not be a valid test setup.

But John is using this setup for a wear test - he will be running for for days, weeks, or months.   Assuming that he runs it at a realistic N scale speed (not at 10,000 RPMs!  He doesn't want to melt the axle pockets - just wear them out.

Well I really had to push things to get it that fast.. at 200rpm with the nail, the speed was pretty reasonable.. I just wanted to see of the idea would work.. and it did..

FWIW..
Video 1 was 8.3 Smph
Video 2 was 35.75 Smph
Video 3 was 384.9 Smph

~Ian


 

[Lemosteam]

Bingolio!