Model Railway Forum

Go Back   Model Railway Forum > Model Railway Construction > On The Workbench

On The Workbench A place to show what you are building, altering, kit bashing etc


Reply
 
Thread Tools Display Modes
Old 07-07-2018, 12:36 PM   #11
Mountain Goat
Unique Member.
 
Mountain Goat's Avatar
 

Join Date: Mar 2011
Location: UK.
Posts: 2,484
Mountain Goat is an unknown quantity at this point
Default

Quote:
Originally Posted by Mixed Signals View Post
Now I'm testing the track and running trains I'm getting a few derails. The track is not perfect yet, however most the derails are on wagons and coaches that appear to have shallower wheels.

Hopper type wagons and the Flying Scotsman coaches derail all the time and have these wheels.

I have a fair bit of Triang stock and didn't expect that to run due to the larger wheel cones and flanges.

However I thought modern stock would be okay. Is the best solution to change the wheels.

Other stock without these shallow wheels rarely derail.
Three things can cause issues. The track, the wheel back to back measurement and the wheel profile.
Wheel profile is often overlooked. The flatter the tread and the more angular the difference between the tread and the flange, the more likely it will be for the wheel to leave the track.
If the wheel tread has a slight angle and there is a nice curve between the tread and the flange, they should stay on the track OK. If you can visualise what happens between the wheels and the rails as they travel round corners with a profiled tread you can start to understand what is happening when the wheels shift outwards due to the curve.

Back to back measurement. The Triang plastic wheels had the ability to vary the back to back as the wagon or coach went along. This can be an advantage but can also be a disadvantage depending on the track used. Triang stock with these wheels do tend not to like modern finer pointwork with their narrower flange ways.
Old Triang stock have deep and thick flanges. It is normally the thickness and the back to back which cause any issues.
For Triang stock to work OK and modern stock to have issues, what is most likely happening is that at the points, the frog is likely to have very generous gaps. The deep flanges on old stock will float over the frog as the bottom of the deep flanges gently touch the bottom of the frog of the point (At the bottom of the flange way part). Now with shallow finescale wheel flanges, the wheels are likely to drop into the flangeway gap at the frog (Where the two flange ways cross) and bounce so the wheels will often derail as they bounce. This is the most common issue.
The back to back measurement can cause issues as the wheels can hit the checkrails and cause a derailment. This can happen if the back to back is to narrow, but can also be an issue the other way round as both flanges may be scraping the rails and may not happily be sitting on the rails.

Track. Another common issue is where the track has a dip or a rise on the top surface. If the rails are not sitting at the same height, then one one wheel may be partly in the air. Now this is where deep flanges have the advantage as they are more likely to catch the rail then jump off. Shallow rail flanges work well on good track, but will really show up when ones track isn't as good as it should be.
I hope these may help.

I once had similar issues but these were with finescale wheels which were on coaches that had a close coupling design including the NEM coupling system. I believe the issues I had were chiefly the flex and the friction in the couplings but add to this the finescale wheel flanges and the coaches failed to grab hold of the track, where other finescale wheeled stock (Along with those with deeper flanges) didnt have the same issues.

My fascination with wheels and track grew when I started to experiment with making my own track for my 7mm narrow gauge layout. I basically use 00 gauge track but the sleepers are larger to account for the larger scale. When I started to build my own points and sharp corners (With checkrails), it was an interesting learning curve. I'm actually glad I didnt get things right straight away as had I done so, I would never had worked out what was going on with the wheels and the track, so it has been a worthwhile project that I'm making.

Last edited by Mountain Goat; 07-07-2018 at 01:09 PM.
Mountain Goat is offline   Reply With Quote
Old 08-07-2018, 08:23 AM   #12
Steved1234
Junior Member
 

Join Date: Jul 2018
Posts: 7
Steved1234 is on a distinguished road
Default

Hmmm I can only comment that using NEM standard wheel profiles on my stock ( Bogie and Fixed wheel) the only time I had derailing trouble was BEFORE I fitted kaydee Couplings.
Steved1234 is offline   Reply With Quote
Old 08-07-2018, 09:37 AM   #13
Mountain Goat
Unique Member.
 
Mountain Goat's Avatar
 

Join Date: Mar 2011
Location: UK.
Posts: 2,484
Mountain Goat is an unknown quantity at this point
Default

An interesting observation. Id say that most issues were prevented by changing because all your couplings will be the same size. Tension lock couplings of different sizes tend to get caught on each other. Another issue can be found if one uses narrow tension locks with no sideways flex on longer vehicles. Of corse, the largest issue with using tension lock couplings fitted with the nem type system is up and down movement. Add the extra flexibility of the close coupling system fitted to coaches and it spells disaster! Before these two designs came out, as long as the sizes of tension lock couplings used were the same I had very few issues at all. The issues came when I mixed Mainline or mixed Airfix stock with my main fleet of the wider metal tension lock couplings that Hornby once made. Run all Mainline or all Hornby and they worked well. Airfix were less successful as they tended to self destruct!
If I decide to keep my 00 gauge items (As at the moment I'm considering selling any spares which dont fit in with the main collection) I'm planning to make my own coupling system for all my stock.
There are coupling designs which are far more universal in that they are less suseptable to issues caused by the coupling height or even size (Within reason). For example, the design I made for my narrow gauge which should have the ability to be altered to use a hook instead of a drawing pin so one can use it for 00 gauge. The only issue is that it is a manually operated coupling design. I have thought about using this for my 00 gauge but I dont think that I am keeping the collection, so tension locks will be more useful for new purchasers.
Mountain Goat is offline   Reply With Quote
Reply

Bookmarks



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT +1. The time now is 06:42 PM.


Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.