Clearance for grain-of-wheat bulbs

[jecorbett]

I am planning a fairly large project to light many of my structures. I will be using 12V grain-of-wheat bulbs. I have read that these can get hot enough to melt plastic so what is the minimum clearance I should have between bulbs and the plastic. Since heat rises, I am guessing I would need more clearance overhead than to the sides or below the bulbs, but you tell me. I'd rather not have to learn this the hard way.

Also, I have a few cardboard roofs. Do they require a different clearance and could this be a fire hazard?

[Railphotog]

Sorry I don't know anything about specific clearances for the bulbs, but do have a personal account of something happening.  I had a bulb inside my roundhouse, on the upper side, that came loose.  It was in contact with the shell of an HO scale diesel for quite a few hours at a train show (this is on my modules).  It melted a hole right through the shell of my custom paintded diesel.  I was able to repair it, but the area is still kinda rough.

Good luck!

 

 

[mikesmowers]

  I use a lot of GOW bulbs for structure lights as well as street lights. They are rated at 12-16 volts, I run them at about 11 volts and have no problem with them at that voltage. If I were to guess I would say that if you were to leave 1/8 inch it should be pleanty. I would suggest that you run them at a lower voltage that they are rated if you can, they will last much longer and not get near as hot.            Mike

[chatanuga]

Sounds about what happened to me with my old Athearn Amtrak FP45.  Had used a grain of wheat bulb to move the headlight down into the nose.  Worked great...for a while.  Took the locomotive along with my old Amtrak consist to the club during one of our open houses.  After running for a while, I noticed a dark spot on the nose next to the headlight.  Sure enough, the bulb had come loose and gotten against the shell next to the headlight, distorting the area of the nose a bit.

Kevin

http://chatanuga.org/WLMR.html

[Texas Zepher]

I don't know either.  I know that in my cabooses and passenger cars that used to use them -- or even bigger light bulbs -- I started making heat sinks to distribute the heat along the entire roof using aluminum foil or cut up beer cans.  This prevented things like the photo below.    For structures I don't recall ever melting one of them down.  If this is just putting the lamp in the center of the structure I would guess that 1" all around should be sufficient.  It probably also depends if the structure is totally sealed or if there is a "window" or two open somewhere.

 

 

[reklein]

Wire in a 1/4W 220 ohm resistor. That'll tone em down enough to keep from settin the layout on fire. Thats what I did on my MDC loco kits when I melted the headlight casting.