But WHY do plastic wheels collect more crud??

Yeah, you must be tired. ;)

1 in 80 doesn't need units specified - it doesn't matter if it's 1 in 80 mm or 1 in 80 furlongs, the slope is the same.

However, I'd have to say Terry has some pretty poor quality metal wheel/truck combinations - I've got N scale metal wheelsets on some Kato tank cars that will _start_ rolling on a less than 1/4 in 48 (1 in 192, or just short of 1/2%) grade. Tomix does even better - I've seen 1 locomotive easily pull over 100 Tomix N scale cars.

No wonder he's always whining about wheel and track standards. LOL!

Don't bother, Terry - You're kill-filed. I only see it when someone else quotes it.

Terry's 1:80 grade is the same as a 1.25:100 grade, that is, 1.25%

Your 0.5:96 grade is the same as 0.052:100, or 0.05%

Thus your grade is a little less than half of Terry's.

If cars are rolling out of THAT yard, they are VERY free rolling indeed.

I strive for a car that will roll freely on a 1% grade, but even then some require 1.5% to 2% grade to get started. If a car won't self-start on a 2% grade I do SOMETHING with the trucks (wheelsets, sideframes, lube, whatever) until they will. I don't run cars that won't START rolling on a 2% grade. That's my minimum standard. Probably 50% of my cars will start on a 1% grade.

It requires some effort and expense to achieve that standard, and continual maintenance to keep it.

Lot's of stuff 'out of the box' won't start, or even keep, rolling on a

4% grade. The newer products are getting much better, however.

Dan Mitchell ============

The models you have that start on a 1 in 100 (1%) grade , what do you do to achieve this, or what are the common factors? The only carriages I have had with this level of free rolling are brand new pin point metal axles in new plastic bearing bogies. After some running in the friction increases to the more typical values you quote above. I to use the same minimum rolling test.

I simply replace the plastic wheelsets with KD, P2k and other suitable wheelsets into the stock trucks. I don't know if the carriages that you are running are two or four axle and if the sideframes are removable. This might be the biggest difference. On my rolling stock (American Prototype) they are changable. I use Athearn trucks (Acetel plastic) and the wheelsets above with Acetel plastic axles.

If your wheels are either 33" or 36" (American sizes for four axles) then buy a pack of wheelsets and try them on a few cars and see if they work any better.

I have a feeling that what the sideframes are made of, if they can't be changed will be a problem.

Good luck

Daniel A. Mitchell wrote on Tue, 22 Feb 2005 09:50:04 -0500:

DAM> Terry's 1:80 grade is the same as a 1.25:100 grade, that is, 1.25%

DAM> Your 0.5:96 grade is the same as 0.052:100, or 0.05%

DAM> Thus your grade is a little less than half of Terry's.

Sorry to disappoint you, but it seems to me that 0.05 is a bit less than half of 1.25 :)

Just my 2 c worth.

Dave.

Dan just slipped the decimal point one place too many to the left. Instead of 0.05 it is 0.5 - which is a little less than 1.25%

Correct! Math/Typo ERROR on my part.

"DAM> Your 0.5:96 grade is the same as 0.052:100, or 0.05%" SHOULD have read ...

DAM> Your 0.5:96 grade is the same as 0.52:100, or 0.52%

... which doesn't change the validity of the discussion, or the conclusion that I stated: "DAM> Thus your grade is a little less than half of Terry's.".

Dan Mitchell

That could well be the problem. If the axle is too long, it will poke into the sideframes, increasing friction and possibly causing the wear that someone mentioned.

If the axle is too loose, it will bear on the cone of the axle more than the point, increasing friction. If way too loose, it may cause truck tipping and tracking problems.

The axles really need to fit the sideframes properly, with just a TINY bit of end play.

Dan Mitchell ============

I think the problem is the conversion to % grades. Why North America uses this method has got me beat. I mentioned wear. As models wear in, the rolling resistance increases. And from what I can see my average models are in the same zone as far as rolling goes, they self start down a 1 in 50 grade = 2% grade. Only brand new models would self start on my 1 in 80 grade = 1.25%. Some observed self starting on a 1 in 100 grade = 1%. Half a 1 in 80 grade is 1 in 160 grade = 0.625%. The above axle clearance rules are mostly complied with by myself, (some 4 wheel wagons are a problem) and the only difference I can guess as to the difference is better surface finish on the axles and bearings, some form of lubrication or inaccurate measurement of the grade.

I use Reboxx's Exxact tool to clean and shape the bearings in the (HO) trucks, which always improves rolling quality. I use Kadee or Proto 2000 wheel sets, which have engineering plastic axles. I usually twirl a 4B pencil in the bearing, too. The trucks will roll on 0.5% (1:200)

To the poster who complained about the noise of metal wheels on his friend's layout: the roadbed etc on your friend's layout is built incorrectly. For minimal sound transmission and amplification, the following is by far the best method (based on my and many other people's experience.)

1) open frame benchwork, ie, no solid table top.

---> A solid table top acts like the sounding board in a piano, it amplifies sound something wonderful.

2) risers of 3/4" ply or 1" dimensional lumber 3) subroadbed of 3/4" ply or 1" dimensional lumber

---> Heavier lumber increases the mass of the substructure. It takes more energy to move a larger mass, which leaves less energy for the sound itself.

4) glue a layer of 1/2" extruded foam insulation to the subroadbed with latex glue.

---> This _really_ isolates the sound from the substructure.

5) glue ballast former (cork, foam, Homasote, etc) to the subroadbed with latex glue 6) glue the track to the ballast former with latex glue (a spot every 6 to 8 inches is enough)

---> Never pin or nail track. It's fast and easy to do so, but it causes troubles in addition to sound transmission. Temporary pinning while the glue dries is OK.

7) use matte medium, not diluted PVA (white glue), for gluing the ballast. PVA tends to dry hard, and hard stuff transmits instead of absorbs sound.

For glue, I use Lepages #7 water-based latex contact cement. Works very well.

A layout built with this method will be so quiet that you can hear the wheels click as they pass over the rail joints. You can file small nicks into the surface of the rail at scale 39ft intervals to get the prototypical clickety-clack, if you like.

If you don't need the strength of open-frame benchwork, use a light framework and extruded foam sheet. There's more to it than that, but this post is long enough already.

HTH

[...]

That's certainly one reason.

But I think the main culprit is plasticisers. All plastics have additives to give them the desired characteristics, and more additives to modify the effects of the additives. (Footnote) It's quite an art to design a plastic. Some of these additives are sticky, and slowly migrate out of the plastic, forming a sticky film on the surface, which mixes with the dust and stuff attracted to the wheel surface by static. IMO, that's the main reason plastic wheels accumulate gunk much faster than metal ones.

Footnote: For example, pure polystyrene is clear as water and very, very brittle. The clear styrene CD cases give you some idea of just how brittle the stuff is, but that styrene has been toughened up with plasticisers! The coloured styrene in models is softer and tougher. For more demanding uses, styrene is alloyed with acrylo-butylene, the result is ABS. Etc.

HTH

I suspect you're right about the plasticizers. I also think that the soft tread of a plastic wheel allows dirt to imbed far easier than on a metal wheel. Wheel to rail contact pressures can be amazingly high despite the light weight of the cars (VERY small contact 'patch').

I've never agreed that static is a big issue, but can't prove it either way.

Anyway, plastic wheels DO collect more crud than metal wheels, and are harder to clean without damaging them. And, nicks and scratches just invite MORE crud to collect.

Dan Mitchell ============