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Old 6th March 2008, 15:20   #1
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Default Headlight glass: Convex, Concave, Flat?

Hi, have always been curious about this, although somehow never really tried mixing/matching. Would love to hear your thoughts on this...

For a bike with a round headlight (Roadking, Bullet etc), you get 3 different kinds of glass for the headlight. One bulges outwards, one is sunken inwards, and the third is flat. Which one do you think would give the best dispersion of light?

I have felt that the inward-sunken one somehow gives a 'spotlight' kind of effect, and the flat one was recommended very highly by a mechanic, as he said it would give the widest beam. Any experiences?

Also want to change the headlight bulb from standard on my 2001 Machismo A350. Any suggestions?

Hope to hear from you all...
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Old 6th March 2008, 15:38   #2
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Quote:
For a bike with a round headlight (Roadking, Bullet etc), you get 3 different kinds of glass for the headlight. One bulges outwards, one is sunken inwards, and the third is flat.
Where do you get such options ? I believe you are referring to different type of headlamps on different bikes which are different from each other.
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Old 6th March 2008, 15:46   #3
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For bulls, I have seen two types of HL glasses. Flat ones and outward bulged ones. I ride a Std 500 and the OEM was a Lucas outward bulged one. Recently I changed the doom set to an Autopal (the same ones in new Ambys) and that's has a flat HL glass. I would say visually I liked the classic outward bulged glass, but the beam of flat one is slightly better.

I use 55/60 philips halogen in my std 500. Mine is a 2004 model bike which has HL running from alternator, not from battery. Running on 55/60 for last 3.5 years without any problem and light is awsome.
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Old 6th March 2008, 15:51   #4
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Nope, not different headlamps. In the bikes I mentioned, it is possible to change only the glass of the headlamp as they are clipped onto the reflective portion, and then held in place inside the dome with a screwed-on front portion.

So, unlike the newer single units, the older headlights actually had 5 components:
1. The outer dome (In the Bullet, this is where the speedometer etc is, and this piece extends down to the front fork. In the Roadking, it is held in place with screws on 2 sides.)
2. The Ring screwed to the dome (This closes the compartment & fits right outside the headlight glass)
3. The glass itself (Convex, concave or flat, anyone?)
4. The reflective portion of the headlamp (in which the bulb and/or parking light sits)
5. The bulb(s) itself

Hope this clarifies it. This thread is basically trying to gather info/experiences on component 3 (above)..
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Old 6th March 2008, 16:00   #5
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Thanks for the details av
Quote:
3. The glass itself (Convex, concave or flat, anyone?)
Hmm is this still the practice in current gen Bulls?

Interesting. See normally I have observed that the Non clear lens type has bulged outside kind of glass, the Classic pulsars had clear lens & although they didnt have flat glass it was less bulged out.

I think some one who has used all these types should be able to answer better.
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Old 6th March 2008, 16:13   #6
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Originally Posted by avkurian View Post
1. The outer dome (In the Bullet, this is where the speedometer etc is, and this piece extends down to the front fork. In the Roadking, it is held in place with screws on 2 sides.)
This is called Casquette. This a bull term, along with Tiger Eyes (those twin parking lamps). This is how they are reffered by bull heads and you can see these terms in classic sites too
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Old 6th March 2008, 16:19   #7
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The convex one are the best for a wider beam throw but some amount of light gets dispersed in this type. Flat is good for medium beam throw and light dispersal is less hence the impression of a better beam. Concave is good for extremely focused lights like search lights and spot lights.
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Old 6th March 2008, 16:27   #8
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Hey, we read and we learn..

Didn't know about it being called a casquette, although have heard of the tiger's eyes. As redfire pointed out, i guess the newer Bullets have single-piece domes that just require the inclusion of a bulb. My experience is mainly on my Roadking, coz I used to sit with my mechs and bug the hell out of them with my questions!

Redfire, can you share the cost of your Autopal & 55/60 halogen set-up? Bangalore is going from hi-tech city to hi-beam city. Will soon need to carry a halogen torch to shine in the eyes of the (in)famous call centre cab drivers.
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Old 6th March 2008, 17:48   #9
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Quote:
Originally Posted by avkurian View Post
i guess the newer Bullets have single-piece domes that just require the inclusion of a bulb.
Yeah, buy the dome, insert the bulb, plug the conector, fix it in the ring and scew .

Quote:
Originally Posted by avkurian View Post
Redfire, can you share the cost of your Autopal & 55/60 halogen set-up? Bangalore is going from hi-tech city to hi-beam city. Will soon need to carry a halogen torch to shine in the eyes of the (in)famous call centre cab drivers.
The Autopal p43t dome (flat glass) cost 120 buck, here in Tvm. The bulb costs from 60-120 range depending on the brand. You get Halonix in the 60 Rs range, and philips 55/60 in 80-100 range. Always match the bulb base type and dome. If you are going for p43t bulb then go for p43t dome or p45t bulb and p45t dome. The p43t bulb has a small disc base having 3 legs projecting which fits into 3 groves on the dome, while p45t has a big round disc base with a small projection at the disc which goes into a slot on the dome. Get both the reflector and bulb from one dealer and try to insert the bulb to see if both are of same holder type. Or keep in mind the type of bulb / dome you got first when you go to get the latter.

Also get the bulb connector, a 3 pin plastic connector which fixes on the three legs of the bulb. My bull came with this connector as the bulb was of new type with three legs. If you are having the old type bulb as OE, with no legs projecting out, you need to get this 3 pin plastic connector and then cut the HL wires and connect the ground (red) / low and high (blue and green) wires to the connector and then plug the connector to the bulb.

Last edited by redfire : 6th March 2008 at 17:53. Reason: bulb connector
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Old 6th March 2008, 18:39   #10
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Convex lens => Conergent Beam
Concave lens=>Divergent Beam

Thats What elementary physics says!
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Old 6th March 2008, 19:05   #11
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Elementary physics is right but convex lens is convex inside and concave on the outside on headlight beams. Vice versa with concave.

So for head light beams the opposite is true.
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Old 6th March 2008, 19:59   #12
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Quote:
Originally Posted by vikram_d View Post
Elementary physics is right but convex lens is convex inside and concave on the outside on headlight beams. Vice versa with concave.

So for head light beams the opposite is true.
Pardon me, but i'm not able to follow the logic
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Old 6th March 2008, 21:17   #13
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If im not mistaken there used to be some fiat headlamps which were convex on the outside. Iv definitely seen it, but maybe that was some bungling mechanic's artwork and not a norm
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Old 6th March 2008, 21:46   #14
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Quote:
Originally Posted by aravindwarrier View Post
Convex lens => Conergent Beam
Concave lens=>Divergent Beam

Thats What elementary physics says!
convex lense converges till the focal point (for a parallel beam, some adjustment for non-parallel beam required) and after which it starts diverging in the other direction. for distances on road, it will always be divergent, unless the docal length of ur convex lnse is in couple meters (till you visiblity). you will not be able to detect the curvature at that high focal length.

the focussing of the beam is done by the reflector which acts like a concave mirror(convex lens) and after that the glass can only diverge it to a suitable extent.
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Old 7th March 2008, 15:13   #15
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Perfect explanation Vivek.
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