Traction on Brass vice Stainless rail

[phils2um]

I fixed the grade this afternoon. (See my post on boosting tractive effort under electric locos.) I now have nothing steeper than 3.5%. The long straight grade was laid on what's locally called slag sand so it was easy to adjust. I noticed an interesting difference in traction on brass vice stainless steel rail when testing it out. The lower section of the grade is LGB brass track, the upper is Aristocraft 332 stainless steel flex track that I picked up second hand. My LGB locos seem to have noticeably better traction on the brass track. A train that will stop and start on the grade OK on the brass track will have wheel slip on the stainless steel rail just past the transition. I don't know if the static coefficient of friction is that different between brass and stainless or if there is a subtle difference in the rail profile that causes the locos' traction tires to be less effective on Aristocraft stainless steel track. Anyone else out there notice this difference?

Phil S.

 

[G-force1]

There are certainly different friction coefficients between differing metals. The best friction is usually obtainable between similar metalls, i.e. steel on steel, brass on brass etc. even so, nothing is as good on wet as it is on dry. As for 'rail grip' there are a lot of other things to take into consideration, such as what vegitation is overhanging, conifers seem to drop something that really doesn't help at all.

I do wish someone would suggest a good way to guestimate grades in percentages, I find it totally impossible, it doesn't relate to anything common sense at all. A grade is an angle in degrees, or a ratio such as 1:50. I have no visualisation of what 3.5% is at all.

 

[ntpntpntp]

I do wish someone would suggest a good way to guestimate grades in percentages, .. I have no visualisation of what 3.5% is at all.

3.5% as a ratio = 3.5:100
If it were 4:100 that would be 1:25, so 3.5:100 is a shade flatter.
Simples!

 

[stockers]

I agree with you - percentages do not register anything meaningful in my little brain.
I was however told an easy way to visualise it.

For percentages, the distance along the ground is always 100 units. Divide this by the number of units required to gain 'one' unit of height. Simples.
So 1 in 30 is 100 divided by 30 = 3.3%
and 1 in 50 is 100 divided by 50 = 2%

 

[G-force1]

When I see it on a road sign I know when it's uphil or downhill (and it's nothing to do with percent). That'll do for my poor noggin.

When I want to measure one, I use a sprit level of known length and measure the height (mine happens to be 2ft) at the high end, so 1" up means 1:24, 1/2" up, 1:48. Anything else is just making life difficult for no good reason. Why in the name of He above would I then want to start doing sums to get to a percentage??????

 

[Rhinochugger]

Yeah, why should you have to do maths to work out the slope? percentages do not relate.

1:3 over Honister Pass makes complete sense

 

[phils2um]

My 3.5% "grade gage" is a 4" wide board with a piece of 1" dia. PVC pipe attached 28.5" (1 in 28.5 or 3.5 in 100) from the end along with a small level. If the bubble is on the high side when the gage is on the track the grade is steeper than 3.5%, low side is less than 3.5%, centered is 3.5% on the money. This is a very useful tool I read about somewhere quite while back. I don't recall where or I'd give proper credit. It was indispensable when laying the block for my curved bridge approach.

Phil S.

 

[stockers]

Yeah, why should you have to do maths to work out the slope? percentages do not relate.

1:3 over Honister Pass makes complete sense

1 in 3 - sounds interesting.

 

[goneloco]

There are certainly different friction coefficients between differing metals. The best friction is usually obtainable between similar metalls, i.e. steel on steel, brass on brass etc. even so, nothing is as good on wet as it is on dry. As for 'rail grip' there are a lot of other things to take into consideration, such as what vegitation is overhanging, conifers seem to drop something that really doesn't help at all.

I do wish someone would suggest a good way to guestimate grades in percentages, I find it totally impossible, it doesn't relate to anything common sense at all. A grade is an angle in degrees, or a ratio such as 1:50. I have no visualisation of what 3.5% is at all.

I used the free SCARM software available online to plan my layout to and it automatically calculates the gradients against spot heights inserted once you have established a zero datum. I then used a spirit level which I added calibrations to to indicate percentage - 1,2, & 3% max as the bubble then starts to disappear from view - used a metre length of track and packed it up one end 10,20 & 30mm to get the calibrations. I just use it then to check the gradient as all my track is laid on dolomite (quarry dust) and requires regular maintenance in the winter as tends to settle somewhat when rained on and we are having plenty of that at the moment in South Australia.

 

[Zerogee]

1 in 3 - sounds interesting.

Blimey, that's worse than Beavercreek Mike's....... (though not by much!)

Jon.

 

[David1226]

I agree with you - percentages do not register anything meaningful in my little brain.
I was however told an easy way to visualise it.

For percentages, the distance along the ground is always 100 units. Divide this by the number of units required to gain 'one' unit of height. Simples.
So 1 in 30 is 100 divided by 30 = 3.3%
and 1 in 50 is 100 divided by 50 = 2%

That's clever. Statistically speaking 8 out of 5 people cannot do fractions......

David

 

[Rhinochugger]

1 in 3 - sounds interesting.

Oh, we're not talking trains

but even in the '60s it was a challenge for a car

 

[trammayo]

That's clever. Statistically speaking 8 out of 5 people cannot do fractions......

David

Fractions can be rather vulgar.

 

[beavercreek]

Blimey, that's worse than Beavercreek Mike's....... (though not by much!)

Jon.

Yeah and some, but thank goodness Rhino is talking roads not track!

I can remember doing Wrynose Pass and Hardknot Pass in the snow and ice...now that was interesting!
I had my old BMW E34 525iX Touring in those days and it was the first BMW to have 4 wheel drive and only 25 came to britain as it was meant for the European and American market as BMW surmised that they had more adverse conditions than us (the X5 did not appear until many years later).
A great car that made short work of the conditions.. it was built like a tank.

 

[Paul M]

Fractions can be rather vulgar.

Yes but it gives the kids something to think about these days

 

[trammayo]

Yes but it gives the kids something to think about these days

Wonder if they still teach Algebra or Calculus these days?

 

[Greg Elmassian]

sorry to derail the derailment... SS track is much more slippery than brass... the oxide on brass just seems to be rougher... the best traction is aluminum... it oxidizes almost immediately in the atmosphere, and most people recognize aluminum oxide as on type of sandpaper.

Greg

 

[stockers]

It also stops the armpits sweating Greg. No really, the white powder is Aluminium Oxide.

 

[Greg Elmassian]

Yeah, was more looking at the properties of the oxide on the rail, not the oxide as a powder by itself. Aluminum oxide sandpaper:

 

[Dan]

Fractions are easy, try multiplying Mantissa and exponents and fractional at that!!
This was my job troubleshooting main frames years ago.