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Guard Irons


Joined: 1-01-03

Topics: 1

Replies: 1

Posted: Thu 9th Apr 2015, 7:32pm
Guard Irons

Does anyone have any recommendations for standard dimensions for guard irons, in particular a recommended height above the rail? I have just test run a loco I have been re-building and managed to seriously bend a front guard iron. In my efforts to straighten it and set it up again I thought I would just check the society wheel and track standards to see if there were any recommendations and I cannot find any information. Can anyone advise and should this information be added to the track and wheel standards page?

Replies To This Post


Joined: 1-01-89

Topics: 9

Replies: 180

Posted: Sat 11th Apr 2015, 9:20am

There are no standards for guard irons set by the Society to my knowledge. If you are building a scale locomotive for show rather than operation you could stick to the scale dimensions. However, to run on 7¼" gauge tracks things become different, as you have found out. The tracks are not dead level, in some cases far from it, so that the front of the loco can move up or down considerably, so guard irons will strike the rails. Many narrow gauge locos are built with a 'derailment' bar across the front of the loco which is designed to slide along the rails should the loco derail. These are usually about 1" above rail height - again no standards set as it depends on the loco design and the track it is to run on. I think it inevitable that guard irons if made to look even semi scale, will suffer damage at some point. The solution I suggest is to make them easily removable so they can either be repaired or replaced when they get damaged. Perhaps some of our members who operate scale locos could offer their views?


Joined: 1-01-92

Topics: 27

Replies: 333

Posted: Sun 12th Apr 2015, 10:13am

I agree with Mick, scale is one thing, and the rest is much up to the builder. The main consideration might be that with a derailment, something like cylinder drain cocks could get damaged, so they perhaps need some protection.


Joined: 1-01-85

Topics: 10

Replies: 66

Posted: Tue 14th Apr 2015, 10:04am

Hi Jeremy - and all
I cannot claim to be a scale model engineer, but I have constructed a couple of standard gauge diesel locomotive models in 7 1/4 and am happy to share my thoughts regarding derailment bars. The true scale appearance of a standard gauge steam loco with correctly proportioned guard irons is undeniable, but unfortunately the maxim that 'you can't scale nature' often comes into play when running on passenger carrying railways. The point is that in full size the guard irons are there to deflect debris on the track, when scaled to 7 1/4 the issue is that rail joint misalignment and derailments occur that defeat the durability of the scaled guard irons.
In my locomotives I use round section derailing bars solidly welded to the main chassis, these are also used as a means of securing the locomotives into my trailer, the bars simply run into securing 'jaws' attached to the transport rails. I use a running height above the rail of just 10mm and this also ensures that in case of derailment the bars slide along the rail head and avoid damage to the running gear. This has worked well for me over the last 30 years. On occasions I do hear the bars make contact with the rail, but this does not cause any problems and the 15mm round section bars simply run along the rail head in such cases. Before fitting the derailing bars to my original locomotive a low speed derailment caused significant damage to one of the power bogies, but this has never happened since the bars have been in place.
It is really a choice between scale appearance and ruggedness, I have always opted for the latter I must admit.
Good luck with the rebuild.

Cheers, Ivan.
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