[troutie-mtb]

As you might have seen from some of my posts I have been making the bar mounts on my lights in the hope that they will use the bars for a bit of heat removal.

so I thought I would take it a bit further with a housing for the cree mc e led when it becomes available

here is the idea for my light .

this will also keep it out of the way when turning the bike over to fix a flat.

So with this design where do I put the driver to keep it as small as possible
I am not sure which optic to use either the 20mm or 26.6 mm
if I used the 20 mm then I could put 2 mc e`s side by side in the aluminium I have

but I figured the larger 26.6mm optic may be the best for the leds and would make a smaller light.

any ideas please

 

[Frs1661]

I'd be a bit worried about getting good thermal contact with the bars. IMO you'd want to clean off whatever paint was on the bar, and use some thermal paste. Your bar mount has to make strong clamping pressure with the bar.

Even assuming a good thermal connection to the bar, you're not really adding alot of mass. I think it may saturate rather more quickly then you might like.

What kind of wattage do you want to push through the LEDs?

Where are you planning on putting the battery? My first thought is a water-bottle setup, where you cold keep the driver in the bottle with the battery.

 

[troutie-mtb]

ref contact with the bars they are anodised so no need to remove any paint
the light will hopefully be machined to be a good fit and a little tip here is to use a little
zinc baby botty cream as zinc is a great heat conducter and the other ingredient is caster oil so will not hurt the bars.

also there will be 1.8 square inches of contact with the bars.

the cree mc e leds will be powered at 700 ma

I already put my battery in small camera bag under the stem it is a 15 v li ion

I have been doodling again and here is my next idea on this theme.

 

[znomit]

Looks good troutie, but since you asked for feedback Ill try and shoot it down...
Its gonna get hot. It might expand enough that it gets loose on the bars.
I would make it hang or sit on top of the bars, and COG right over or under the bars so it doesn't want to flop down. Over the bars means you don't have to deal with cable shadows either...not so bad on a triple of quad but with such a small source a cable in the way would be really bad.

 

[troutie-mtb]

Looks good troutie, but since you asked for feedback Ill try and shoot it down...
Its gonna get hot. It might expand enough that it gets loose on the bars.
I would make it hang or sit on top of the bars, and COG right over or under the bars so it doesn't want to flop down. Over the bars means you don't have to deal with cable shadows either...not so bad on a triple of quad but with such a small source a cable in the way would be really bad.

Cheers znomit , that is why I posted for constructive feedback :thumbsup:

good point about the expansion ok I make the rear of the clamp oversize and line it with inertube .

I like the vertical idea too and it might give me more space for the driver but the heat then has to travel down to soak to the bars .

cant hang down cos the cables will deff be in the way but I like that too keeps the light out of the way from over the bar dismounts too .
will have to check where the cables are

 

[Guest]

I have always liked the idea of using the bike as a heatsink and I think it should work fine, copper grease is a good heat conductor but I never knew about zink cream. The only problem I can find is you can't aim the light left to right.
Becouse heat rises having the light under the bars will allow the heat to rise into the bars, but then as said before you may have cable probs. EDIT the post above wasn't there when I started typing.

 

[troutie-mtb]

Cheers dweeby
never even thought about the heat rising into the bars
I will have a close look at the cables and see if it can go under and experiment with my exsisting light to see any shadows .

also copper grease I have a massive tub of that just never thought about using it
for heat transfer

 

[mofoki]

What are the masses with carbon bars going to do?

 

[znomit]

good point about the expansion ok I make the rear of the clamp oversize and line it with inertube .

If you do that it wont transfer the heat.
Im really liking my under stem setups. Totally out of the way. I used some welding rod to spread the cables. I think all stems are different though so a machined clamp is no good.... maybe a double clamp to the bars or a single offset one? Someone made a double clamp to the bars either side of the stem and it looked fantastic, think it was that curvy triple???

 

[Guest]

I had an idea some time ago after too many beers. It was to make a stem face plate with Leds in and put the driver insde of the hollow stem. It never happend but I still look at my wobbly drawing for a laugh now and then.
But you never know, one day........

Just a thought on expansion, if the bar clamp and bar are both made from the same meterial won't they both expand as they get warm and then still fit tight. Maybe not, not sure on that.

 

[Turveyd]

Okay :-

Heat only rises in air/water not in solids, because it makes the air expand and therefore lighter than the normal sized air around it in Metal heat will radiate equally, feel your copper central heating pipes same heat top and bottom, yes the heat of the bars will convect up towards the unit but as your moving it'll have zero effect.

NO way is this thing going to get hot enough for it to become loose on the bars, 80c is the internal max temperature, so doubt you'll get to 40c external temperature while riding outta and even then the bars will heat up and expand to fill the gap anyway.

Wouldn't use Copper Grease, yes the copper part is good but the grease part isn't better off with CPU thermal paste.

What you really need is copper water filled bars though

Water filled bars, would really increase the transfer rate, then a pump and a motorbike radiator mounted under your stem

 

[znomit]

I had an idea some time ago after too many beers. It was to make a stem face plate with Leds in and put the driver insde of the hollow stem. It never happend but I still look at my wobbly drawing for a laugh now and then.
But you never know, one day........

Just a thought on expansion, if the bar clamp and bar are both made from the same meterial won't they both expand as they get warm and then still fit tight. Maybe not, not sure on that.

Thats a cool idea Dweeby. :thumbsup:

Regarding expansion, the light housing is going to be significantly hotter than the bars and hence get bigger.... probably a lot hotter.

 

[dazzat3]

Okay :-

Heat only rises in air/water not in solids, because it makes the air expand and therefore lighter than the normal sized air around it in Metal heat will radiate equally, feel your copper central heating pipes same heat top and bottom, yes the heat of the bars will convect up towards the unit but as your moving it'll have zero effect.

NO way is this thing going to get hot enough for it to become loose on the bars, 80c is the internal max temperature, so doubt you'll get to 40c external temperature while riding outta and even then the bars will heat up and expand to fill the gap anyway.

Wouldn't use Copper Grease, yes the copper part is good but the grease part isn't better off with CPU thermal paste.

What you really need is copper water filled bars though

Water filled bars, would really increase the transfer rate, then a pump and a motorbike radiator mounted under your stem

I Believe Turveyd is correct in regards to heat transfer in solids and I agree that thermal paste would be the best option. Copper cote/grease gets everywhere, regardless of how hard you try not to spread it.

Just thinking out loud here...How would you go making your housing a rectangular shape with rounded corners and 3mm x 2.5mm cooling fins equally spaced around the entire housing?...mmm, I do like dweebys stem mounted light idea, though!

 

[troutie-mtb]

If you do that it wont transfer the heat.

no I would leave the front of the clamp bare and a good fit to the bars

dweebys idea is good can you get into the stem with the bars in the way
now that would take some making
can we see your wobbly drawing dweeby please

 

[znomit]

no I would leave the front of the clamp bare and a good fit to the bars

dweebys idea is good can you get into the stem with the bars in the way
now that would take some making
can we see your wobbly drawing dweeby please

:thumbsup:
You could spring load the mounting bolts too to keep things tight... hmmm.

Yeah, that stem mount would kick arse. Are the bolts a standard spacing?

ps, I was snooping cutter.com.au and they have prices up on MC-E leds.

 

[troutie-mtb]

well Hope do make a stem faceplate with mount for their lights and battery
I bet the bolt holes are not standard though

MC-E prices http://www.cutter.com.au/products.php?cat=45
but not until august/september

Oh well that gives me plenty of time to get the housing sorted

 

[Guest]

It's a funny old world, but I mentioned the stem light to fellow mtbr members about a year ago and most thought I was mad so I listened to advice for once and never bothered. Only to find people now like the Idea and most annoying is that exposure lights have gone and done it(well a commuter version). I don't want to take the subject off of troutie-mtbs light just agreeing with using an alloy bike as a heatsink.

 

[troutie-mtb]

Dont worry about my thread it is threads like this that spark ideas for folk.

Your stem faceplate idea just lends itself to the new MC-E led and 20 mm optics
with there small footprint I think the optic and led mcpcb will be max 15 mm deep and the driver in the stem ok you lose the thermal protection but I am sure you could put 2 MC-Es on a face plate and there would be plenty to take the heat away

one main issue would be getting the vertical angle right for your own stem.
I do have an idea how to make it adjustable though.

Come on dweeby you can do it , you know you want the challenge

 

[Guest]

There are a few problems and the biggest one has always been the aim of the thing. but it can be done. The idea at first was to have it permanently fitted as no real point removing it when the only added weight is two leds and a driver. But not too long ago someone posted (maybe znomit)a dynamo light with the elecronics inside the fork steerer and that got me thinking again. A DC socket in the top cap and you could just plug the battery into it and go. I don't know about this one as a challenge, I end up not sleeping untill it's done, it pisses the wife off and turns my house into a load of wire and metal dust.

What is your idea for adjustability, mine is simply to have slots instead of holes.

 

[znomit]

There are a few problems and the biggest one has always been the aim of the thing. but it can be done.
... not too long ago someone posted (maybe znomit)a dynamo light with the elecronics inside the fork steerer and that got me thinking again.

What is your idea for adjustability, mine is simply to have slots instead of holes.

Theres is a bit of adjustability in the face plate anyway. If its a floody beam the adjustment isn't critical so you could guess and design most of the angle in.
If you dont need to transfer heat to the bars you can make a simple pivoting plate for perfect aim.

Yes, there is a lot of spare room in the steerer tube. The board I bought from pilom.com for my dyno is custom designed to fit, clever. A bflex should squeeze in a switch seals the top. You should be able to run wires past the star nut. Battery and LED wires out the bottom. Very tidy.