Locomotive wheel thickness question

[syrtismajor]

Hello all!
This is sort of a newbie question where I have had various answers from different people who all seem to have varying opinions.
Basically it is about the thickness of locomotive wheels, specifically when used on 3.5" gauge track (3/4 scale)

Some loco designers seem to favour a thicker wheel (3/8" tread with a 1/16" flange) while others seem to favour thinner wheels (5/16" tread with a 1/16" flange). Is this just down to the opinion of the builder or is there a genuine reason for this difference?

The thicker wheel makes sense to me for long duration of use whereas the thinner (or more finescale) wheel wouldn't have the same durability. This however is the squashed by the angle most wheel treads are cut so the are not at 90degree angle to the face

Anyway, I hope the following crap-o-cad drawing will make sense:

The main reason I ask is that I am in the process of trying to design my own live steam 3.5" gauge locomotive. Most of it I think I have pretty much got sorted (including the layout of the valve gear). The main two things I need finalising are the thickness of the wheels and the design of the boiler (that will be 'borrowed' from a published plan though). This will be the next project after my 'Virginia' is completed...

Any help or suggestions would be greatly appreciated!

 

[kvom]

As far as wear goes it shouldn't make any real difference. For a thicker wheel the lateral spacing of the side and main rods and cylinders might be affected. OTOH, heavier is better for traction.

 

[kf2qd]

A bit more width might help by giving you just a hair more to work with as to rail spacing tolerance.

 

[rkepler]

The thing that will matter the most is the back-to-back spacing and the flange thickness which together gives you the gage and the ability to run through frogs instead of over 'em. The 1/16 looks a bit iffy to me, not much thickness for a riding scale.

Here's a link to a pdf that gives a fair view of the IBLS standards:

http://www.homerailwayjournal.com/Wheel_Standards.pdf

Don't forget the 2.5 degree taper, it's what lets trains work with solid axles.

 

[Bastelmike]

Hi,I would stay close to the wheel width in 1:1 scale. Wheel rims for standard gauge are 100-120mm wide.Don't forget the taper on the wheel rims, usually those tapers are 1:20 up to 1:40.And include a radius between wheel rim and flange.Mike

 

[chipenter]

A lot depends on the number of driving wheels , six driving wheels tend to spread the rails on the curves and a short four my drop through , 3\8 overall works well on our club track .

 

[syrtismajor]

Thanks for all the help here! A few of the points I am already aware of and it's probably my fault for not incorporating it into the crap-o-cad. The taper will be on the wheels as well as the radius between the tread and the flange.

My design is for a Pacific loco (4-6-2) so there'll be six driving wheels in total. Each will have a slight lateral movement which combined with the 'tolerance' gap left between the facing sides of the flanges will allow travel through corners. This freedom is taken straight from a published design in 1946 for another Pacific loco 'Hielan Lassie'

I currently own three drawing sets for 3/4 scale locomotives. Two by LBSC and one my Martin Evans, both who are respected model engineer loco designers. LBSC is the one who prefers the thicker wheels while Martin prefers the thinner. Both also state that the flange should be only 1/16 thick (this is interesting especially with that really helpful pdf posted by rkepler).

With all this info I think I am going to go with the 3/8 overall thickness as this makes the loco 1/8 thinner overall. It doesn't sound like much but will alter the appearance of the loco. That is unless anyone here can give me a good reason why this would be unadvisable?

Thanks again!

 

[tomsmachine]

On my 1" scale the drive wheels are .562 wide the flange is .140 at the base and tapered at 5°, the tread is tapered with a 2.5° angle. the taper on the tread is what keeps the loco from a drunken path going down the rails. As the train travels on the track and the wheels move axialy, the larger diameter of the taper will drive that side of the loco a little faster, and the smaller diameter pulls the loco to that side, the result is the wheels find an equaliberm so it leads the loco to follow the center of the track.