Self Guarding Frogs and motorcars?

sbhunterca · **Joined:** Sun Aug 22, 2004 7:58 am **Posts:** 728

I'm wondering if anybody here has had experience with the wheel profile on handcars, motorcars, section lorries, etc. around self guarding frogs?

Note, we don't have, and never will have, any steam power with blind drivers, so this doesn't factor into our frog at all.

We are installing a new turnout as part of our mainline realignment/ carshop lead, and want to ensure no difficulties occur:

http://public.fotki.com/elliottd/sfrmeo/sfrmeoalbum5/imgp9970.html

Due to the design of the frog, it would be easy and safe enough to cut the guards off and install proper guardrails. However, I would like to understand exactly what is behind the rumoured tracking difficulties.

Thanks, all!

Steve Hunter

G. W. Laepple · **Joined:** Mon Aug 23, 2004 5:10 pm **Posts:** 1182

At least in my experience, motorcars and pushcars don't have any particular difficulties with self-guarding frogs. Hy-rail vehicles, on the other hand, may derail if not operated slowly and carefully. Their wide wheels will ride up on the guard, but will come back down where they belong if operated with care.

Bobharbison · **Joined:** Fri Dec 03, 2004 9:42 pm **Posts:** 3011

Are you certain the comments were related to Self Guarded Frogs? Unless your motorcar has exceptionally wide treads or the wheels are mis-gauged, you typically should not have an issue. As you mention, steam locos with wide driver tires are a different matter.

However, speeders and the like do have problems with spring frogs and other movable point frogs where the flangeway closes. On spring frogs, they typically aren't heavy enough to force the springs open. Obviously the lack of a flangeway means at best you get a rough ride, and it has to be done very slowly and carefully.

Could they have been mistaken on the type of frog they were discussing?

Bobharbison · **Joined:** Fri Dec 03, 2004 9:42 pm **Posts:** 3011

PS - If they have to go, before you slice off the guardrails and probably ruin the integrity of the casting due to the heat and loss of structure in the process, look into swapping it for a regular frog.

sbhunterca · **Joined:** Sun Aug 22, 2004 7:58 am **Posts:** 728

I'm really not sure what the basis is for the rumours I've heard, and that's why I'm asking here. As with all rumours, they could be completely unfounded, but due diligence must be exercised!

The comment regarding hy-rail vehicles makes total sense and could be the source of the rumours. It's very possible it results from confusion between self guarding and sprung frogs.

As far as I can see, the only possible difficulty would be the narrower tread on the wheels- I'm not sure whether they could shift far enough to one side to catch the frog point and derail. So far, the only such wheelsets that have been through the new turnout were on a heavily loaded lorry that was hard to shift sideways.

Obviously, I'd like to extensively test the frog/ wheel interaction, and if the rumours prove to be unfounded, no mods would be made. Basically, I'm just looking to see if anybody has seen difficulties.

Thanks, all!

Steve

sbhunterca · **Joined:** Sun Aug 22, 2004 7:58 am **Posts:** 728

OK, I found these articles on the NARCOA web site. It appears the cause of difficulties is indeed the narrow wheel profile:

http://www.narcoa.org/info/safety/self-guardingfrogs.pdf

http://www.narcoa.org/info/safety/guard_frogs.htm

Installation of proper guardrails should prevent any difficulties, with no need to modify the frog.

Steve