Gasket for Inspection Lamp

[TomoHawk]

The engine inspection-work lamp has a round rubber ring under the white plastic bulb cover... It keeps the moisture out, and the bulbs last longer

Where can you get new ones? I was thinking of making one using plaster-of-Paris and the usual black RTV silicone stuff.

thxZ

[Mikes Z car]

I cut one of out of an old truck inner tube for one I have but recently I noticed in another one that there seemed to be two gaskets, besides the rubber one there seemed to be a brown possibly translucent gasket that was very thin compared to the rubber one and seemed like it was made out of plastic.

But for fun how would you use plaster of paris to make one?

[TomoHawk]

It's the same way they make gummi bears or worms.

You pour Plaster of Paris into a shallow mold (about 10mm deep) and before it sets, you press your part (the old rubber ring or some kind of similar plastic ring, coated with some Vaseline) into the plaster. After the plaster hardens, you might modify the female mould, then flow some RTV stuff into it, and let that set up overnight. You could even make several copies of the part or press other parts in the same mould.

But for the gummi bears they just use a bed of starch powder.

[Mikes Z car]

Hah! That is pretty neat. For some reason I get excited about figuring out how to make parts from moulds or other techniques for making parts. I have some mould rubber for making moulds that I haven't used yet. I want to eventually try to duplicate the badge in the middle of the horn button just to see how it might come out. First though, I have to get a horn button to duplicate.

I wasn't sure what you meant by pressing other parts into the same mould. Did you mean the first mould can spawn another mould for a different part that has some commonality as far as its shape as compared with the first part?

[TomoHawk]

By pressing other parts into the mold I mean that you can make many parts from the same mold. If it's big enough you can make a mold, say for all the parts needed for a project, like you get in a plastic car kit. I usually just do one at a time, because the plaster hardens quickly.

I haven't tried this myself yet. I was just suggesting a quick way to make the rubber ring for the inspection lamp until a proper one can be located. I'm not even sure it'll come out right, because Plaster of Paris is porous, and the texture will probably show in the finished part.

Another problem I think I will have is that I probably need some kind of release agent, as RTV silicone might stick to the plaster! Maybe a dusting of baby powder will work, or a thin coating of Vaseline. Maybe it should be sprayed with clear paint even, then some wax, grease or oil.

Edited August 30, 2013 by TomoHawk

[Mikes Z car]

Oh okay I understand now. If you do some experimenting with this if you are so inclined I would be curious as to how any of this might turn out. They make a mould release, I don't know if it would be any better than vaseline.

[TomoHawk]

OK, but as I said, this rubber part is basically just an O-ring with a triangular cross-section.

[EuroDat]

I stamped mine out of rubber foam. Its about 3mm thick and works well. Mike, I think the original (on mine) was a silicone rubber gasket with a clear adhesive ring to attach it to the lens holder. The adhesive in mine turned brown and brittle. The silicone just crumbled in my hand.

I also made a mould for the lens, but its 2mm to high to send as regular post and therfore cost €16.00 to ship anywhere outside The Netherlands:disappoin Started making a shorter version, but other more important projects keep interrupting planning. Now winter is coming Ill finish it. See blog for details

Chas

[TomoHawk]

It looks as though you could just put in a 3mm ring of silicone RTV and never need another.

[EuroDat]

I just made some photos of the ones I made some time back. The one I am using in the car is 2 years old and no signs of wear.

The rubber foam Im using is used as a vibration insulator in truck bodies so it should hold up to the conditions its in without any problems. The grey/green lens is a 3mm shorter mock up for a new mould. It still needs polishing. The photo doesn't show the height difference all that well, but it is a little shorter.

Chas

[Mikes Z car]

EuroDat,

Your lens looks really great! I'd be proud of that work.

Mike

[TomoHawk]

That looks like an improvement to what was in there originally. I have never seen that material in the usual auto parts stores; is there anything else that you could get at the DIY stores, like Home Depot, or even a fabric store?